Intake tuning for your quads

[rthy]

By request I am posting this and I know its over-simplified and uses generalisatons but here goes anyway. Also of note these sort of calculations should only be used as guides, nothing beats a dyno.


Basic pricibles of harmonic resonance in the intake:

When the intake valve of an engine opens a low pressure wave travels up the intake untill it hits the end of the trumpet/plenum entry and will send a high pressure wave back down the pipe. During which time the engine has gone though its combustion. If the pressure pulse has taken the right amount of time it will hit the intake valve just as it is opening sending a possitive pressure wave into the intake of the engine. This however will only occur at its greatest at one point in the rev range (variable cam timing exempted). If an engine is at the right rev range for this to happen it is having a harmonic resonance in the intake.

To adjust the rev range at which the resonance will happen the length of the intake can be changed, for owners of 4a engines with 20v throttles this is relatively easy. Basic theory is that the longer the trumpet the longer it will take the pulse to reach the end and come back, this will work for a lower rev range because the engine at lower revs will take longer to go through its 4 strokes and hence the time delay needs to be longer to get the right resonant frequency.

So as a rough rule:

Longer trumpets than standard = more of a low end power boost
Shorter = more of a top end power boost

all in theory anyway


This can be worked out with the graph or forular as shown on Mr Accoustics webpage:

http://www.my-acoustic.com/Car/intake_exha...take/intake.htm (http://www.my-acoustic.com/Car/intake_exhaust/intake/intake.htm)

Standard 20v trumpets are not equal lengths however the rough tuning point is 5000 rpm according to Mr Accoustic

Also fo note having a harmonic resonace does not mean the maxim power will be there, the best way to think of it is it shifts your power curve in either direction depending on your tuning.

Just for the record F1 cars use this princible to the max and have variale length trumpets, and from what I hear they often have possitive pressure inside the chamber: ie boost without air being artificially pushed in.

I will try and add more information shortly when I have more time.

[ae86 drifter]

good write up sam im interested to see what else u can find out

[Gilly]

sounds like i want long ones for daily driving and short ones for track work :P

indeed a good write up Sam and something i had heard about but never looked into.

[dr1ft-pig]

by the looks of this i think i will go with shorter trumpets, will experiment when i got the cash for dyno runs and more trumpets

[Oly AE86]

Principal works indeed.

My Original trumpets inside and airbox were very short about 20mm and top end was Nuts, but bottom end was lacking.

Current trumpets are about 70mm long and bottom end has increased, definitely better up hills and driving the streets. More practical for day 2 day.

Oly

[riojin]

so for a worked late model 7afe with ITB's shorter trumpets are better?

i saw one time in a street machine (i dont read the bogan mag much anymore) a 351 with ITB's but the trumpets were all different lenghts. how would this work, would it have much potential?

it was a show car and i assumed it was just for looks

[Konakid]

Very good post, have always thought about how the length would alter the power band.

[Gilly]

i'd be interested to see pics of peoples setups, especially the longer items as there isn't a great deal of room on number 4 throttle due to the clutch master being in the way. I remember when Biggo's trumpets were being made the last one had to be made shorter :P

does inlet diameter/taper mean anything Sam?? i also remember reading something about the bellmouths themselves having an effect, with the lips that curl right over them selves being the best choice of all (much like the T3 items)

[starni_boy]

does inlet diameter/taper mean anything Sam?? i also remember reading something about the bellmouths themselves having an effect, with the lips that curl right over them selves being the best choice of all (much like the T3 items)[/b]

from what i have read, the bellmouths that curl right round themselves (eg. T3 items) have a less restriction for air travel up the throttle bodies.

in a drift battle magazine, it has a full article on 4age engines, i have it here somewhere, and it talks about the trumpets..

[rthy]

wow this topic got a whole lot more interest than what I expected. I am a bit short on time right now to reply properly but I will see what I can do tonight

[SpotterOne]

There is certainly some interest. Im about to embark on a trumpet making exercise with a pile of pre-fab trumpet ends and some torroids to make bent ones to fit under the bonnet. Just waiting till after this weekend, which is when the last NSW Supersprint round is on before I go pulling the car apart again.

The T3 ones are also tapered which has an additional effect on airflows into the engine.

[rthy]

Gilly: the idea of changing trumpets on the conditions is a sound idea, however you may find that the engine may well need a retune between changes. However if you have an ecu that accepts twin maps then your well ahead and the power is there for your taking. You could also tune it for some better fuel while your at it too

As for the taper of inlet trupets I am still looking into it, I know it’s a very complex thing and the subject of countless man hours on a dyno for race teams. The theory is that it speeds the air up with a taped inlet, I don’t know myself.

The inlet opening is a little more clear-cut though, a pipe with a flared end will flow 30% more than just a straight pipe or just an opening. This is why anyone who just takes the trumpets off and slaps an airbox on is doing a very bad thing. Going from a flared end to a full curled bellmouth gains another 3% of flow.

The debate is this: have a full bellhouth on the inside of an airbox or have a curved taped inlet in the side wall of an airbox. I have heard various opinions on this and I am staying out of it.




Drift-pig: Brendon what you can is make a set of trumpets that are adjustable without too much effort, well that is assuming my idea would work! What you do is get a flange plate for the throttles (chopped out from the stock airbox is great). Then weld some 2 inch exhaust pipe stubs on it about 20mm long. That will let you slide a piece of stiff rubber hose over each and clamp on, then at the other end have a set of bell-mouths with a short pipe on each at that end again to let you slide a piece of rubber over. Chop some 2 inch rubber pipe to the longest length that you can practially have the trumpets, do this again till you have 4 equal size pieces. Now what you can do is have the rubber lengths acting as a pipe between the flange and the bellmouths. Adjustments can easly be made from here by chopping pieces off at a time.


Oly ae86: assuming that your talking about a 20v then the tuned rpm for your two setups are as follows:

20mm: 9200rpm
70mm: 7500rpm

did you find that you lost any top end with the longer trumpets? because you shouldnt of


Riojin: I don’t think a modified 7afe would like short trumpets, simply because unless some costly internal work is done then you wont be able to rev it hard enough reliably to make use of it. From what I hear peak power with a 4age head is at around 5500rpm and I can only assume that with a high modded 7afe head it would be the same with mild cams. It would be different with more aggresive cams but then theres the rods and crank issue again. For me personally with that engine I would have a resonance at 5000rpm or so.

What you talk about with staggered trumpets its somewhat interesting so let me explain what I make of it: First up the theory is great, instead of a single point in the rev range that all the pipes work in resonance it is spread over the rev range as the shorter pipes resonate at the higher revs and the longer ones at lower revs. Reality is very different, on every engine I have seen with multiple cylinders the load metering with the ecu is done over the whole engine and that’s where the problem is. You see if at for example the longest trumpets start resonating at 4000rpm and the rest are not because the are shorter then it means that those two cylinders are getting more air in them that the rest. This does sound so bad till you consider the way the ecu works. It just measures and works out a total load of an engine, every ecu that I know of assumes that every cylinder of an engine is equal and if it isn’t like out example earlier it would get an average reading of all the air going in. So the cylinders that are sucking a this-proportionate amount of air less compared to the longer trumpets will run richer. Again not so bad but the pipes that are flowing better than the rest will run lean and then is very bad news indeed. So yeah unless it had carbies which may work its just for looks, make sense?

[Gilly]

hmmm i'll have to check the twin map thing, would be a wicked score if it does :P

i will definately be getting a retune as its copping some different gear compared to its current setup, mainly the longer trumpets, slight CR bump, and some nicer extractors (again one of your strong points :P )

always a good read Sam, thanks for the words

[rthy]

the pleasure is mine Gilly,

just a few more things to keep in mind:

for max speed it might be best to have your resonance tuned to or just above your normal max power, that way you would have a real decent acceleration.

and make sure your extractors are tuned for the right rpm too! although thats so much easier said than done

[Gilly]

i'll have to find the specs on them, they are Fujitsubo items, i have specs somewhere..

i might have to pm you some questions closer to the time it all comes together, if you don't mind of course!!

just want to ensure i optimise what i've got ;)

[rthy]

feel free its not like I am going anywhere

[rthy]

I thought you guys might be interested to also know for a while I have been dsigning a system of a variable intake system that uses a set of sliding tubes. But now I am instead thinking of making just a dual stage system to improve my power and economy.

[roadsailing]

I'm going to look in to this in the (hopefully near) future, dunno how much the tuning will need to be adjusted to find the new peak torque RPM, but im at least hoping to get a few points to make sme assumptions (hopefully the relationship is reasonably linear)

i'm planning on using a fixed length, was going to use two short and two long to flatten out the torque curve a bit, but decided i want all the cylinders tuned to the same RPM instead.

I have heard that people are generally dissapointed with very short lengths (haha) and the best thing to do most of the time is to make them quite long, as sam has said nothing beats dyno tuning, as you could find making them longer will actually give you MORE top end, as other things come in to play.

another important thing to look at is the distance from the butterfly to the inlet valve, this affects power, throttle response and drivability.

from dummying stuff up, you can get an 80mm trumpet length (not effective length) on a set of silvertop quads and angled T3 adapter on a smallport head without going outside the confines of the original manifold, but this doesnt allow for a plenum outside the trumpets, and i don;t want to use individual filters, so more work is needed.

sam, i think the dual length is the way to go, you might want to look at using 4 of 6 runners from a EL-BA falcon as they use a pretty simple system. you could look at seperated chamber pulse tuning as well, but i havent seen it used on 4 engines before. a variable length system would take too much effort to tune IMO

[rthy]

I would strongly recomend having all equal lengths for the reasons I said earlier

yeah I have heard that the falcon engine does what I want mine to do: and this is that it acheives the first long runner resonance at the same rpm at which the engine sits on the freeway helping fuel economy. I will have a look at the setup and see how they did it, thanks for the tip.

[rthy]

I forgot to post pics of my own intake:

http://www.ae86drivingclub.com.au/dcimages/2/5/2/44939.jpg
http://www.ae86drivingclub.com.au/dcimages/2/5/2/44938.jpg
http://www.ae86drivingclub.com.au/dcimages/2/5/2/44940.jpg
http://www.ae86drivingclub.com.au/dcimages/4/8/4/3/148412.jpg
http://www.ae86drivingclub.com.au/dcimages/4/8/4/3/156866.jpg

more information in my worklog

also I sujest to be very wary of going wthin a few cm of the brake booster it will affect flow.

[Chrisso]

Has anyone come across information regarding the taper of the trumpets? Are there any theories regarding the impact of a tapered trumpet versus a straight sided affair, and how long the taper runs for (ie. the whole length of the trumpet), and the degree of taper over the length?

Just some random ideas as I'll be shopping around for trumpets shortly as the adapter for the ITBs just arrived.

Regards,
Chris

[rthy]

I have been trying to figure this out for myself and I cant seem to find the information I want in books. All I could find is this informaton:

The theory is that you are meant to have a venturi point going in from the valve to a choke point of 0.85 to 0.87 of the valve dimater inside the port and from that point outwards to the edge of the trumpet is meant to be one gradual angle increasing in size till the opening. Its all theory though and I couldnt find any real world testing however I should have another source of information coming soon that may have some more info on the subject.

[Chrisso]

I would imagine that it would be something that's hard to generalise. As your info pointed out, "...and from that point outwards to the edge of the trumpet is meant to be one gradual angle increasing in size till the opening.", the taper of the trumpet itself may have little to no impact if the rest of the inlet port has a different gradient. My only thought is that the trumpet taper might alter the venturi effect at the valve assuming that the rest of the port has zero taper and that there may be an optimal rate of taper to maximise the effect over the length of the tapered section.

My uneducated guess would be a miniscule impact.

[rthy]

sounds like a damn good guess to me and I would risk agreeing with you on it. Either way I would very much like to see a dyno run with tapered trumpets and straight back to back both with equal lengths.

[stefan]

ive seen on some other 20v and formula atlantic 4age's have staggered size trumpets

why is this

it looks like its more for firing order

[rthy]

got a pic?

they may have a motec ecu that allows for seperate fuel trims for each cylender for each rpm range to allow for a greater spread of power, got a pic?

[ke70dave]

thought this might interest you sam

was talking to beerhead a while ago about this idea, basically need to draw up a graph of RPM vs maximum flow/vacumme effect produced by certain lengths of the intake track, then figure out some sort of controler circuit top control the length of the intake using a servo.

these pics are off the "R1" motorbike, pretty much what i want to build one day....

mmm automated variable intake length....

http://www.ae86drivingclub.com.au/dcimages/4/8/4/3/160516.jpg
http://www.ae86drivingclub.com.au/dcimages/4/8/4/3/160517.jpg

[rthy]

I was personally thinking more along the lines of a servo motor with a linear resisitor for feedback

[stefan]

[attachment=19671:014.jpg]

the 2nd and 3rd cylinder is longer than 1 and 4

that motor is porn

also what is those jets for that point into the trumpets?

nos lol

water spray?

compressed air?

[rthy]

ok this I think i can answer with some sort of confidence, the outer two are longer for packaging only, or else the trumpets wouldn't have a full bellmouth. With that short of a difference the engine can still be tuned as a whole. The "jets" are fuel injectors, F1 trick that one, you gain high rpm atomisation at the expense of low down atomisation and proper fuel mixing

[stefan]

ah sweet that makes alot of sense

getting good air fuel mixture b4 it hits manifold

[rthy]

its also so the fuel gets a better chance to absorb the heat out of the inlet air... I think

[Medicine_Man]

Watch this..

http://www.youtube.com/watch?v=GsKNbsDqEPs

[mc68]

<div class='quotetop'>QUOTE (Sam_Q @ Dec 13 2007, 04:04 PM) <{POST_SNAPBACK}> (index.php?act=findpost&pid=451814)</div>
ok this I think i can answer with some sort of confidence, the outer two are longer for packaging only, or else the trumpets wouldn't have a full bellmouth. With that short of a difference the engine can still be tuned as a whole. The "jets" are fuel injectors, F1 trick that one, you gain high rpm atomisation at the expense of low down atomisation and proper fuel mixing[/b]

in other words. its gonna run a like a dog when its at low rpm...but i assume those sort of engines (really shouldnt be in a sprinter anyway) idle near or above 2500 just to keep the thing running

[rthy]

medicine man: that very much looks like a setup that brings these injectors in later in the rev range, also why does it look like the third one in isnt working right?

mc68: I dont know about the idle but yeah the theory is you lose low down power, also your fuel economy gets worse

[Medicine_Man]

Just more of a video so people can see how they work..

[rthy]

yeah fair enough, just found it interesting that it seems to have staged injectors, which is ideal. I found it interesting either way

thanks for the link

[SLO-030]

Staged injection. The row closest to the head is used at low rpm and the outer row for high rpm.

Smiliar to the FA motor setups but still has usable power down low in the revs

CelicaRA45 on toymods has done that to his beams 3sge and gained huge amounts of power and torque across the board.

[rthy]

what an interesting product, never have I seen a bolt on second stage injection before. BTW they are blacktop throttles

craig: I will relook at what that guy did, thanks for the lead

[Gilly]

:blink: your thoughts please Sam

http://www.ae86drivingclub.com.au/dcimages/4/8/4/3/161104.jpg

http://www.ae86drivingclub.com.au/dcimages/4/8/4/3/161105.jpg

http://www.ae86drivingclub.com.au/dcimages/4/8/4/3/161106.jpg

[blair]

:o

[chapl]

longer 'runners' like that will give you better low - midrange torque

shit for top end though

[Gilly]

I understand that, just thought Sam would like the pics :P they are like 4 times longer than any usable length i've seen

[rthy]

How interesting, thanks for the pic Dave,

Chapl: got to be carefull engines dont always act the way they are meant to, I hear that the ideal length for top end power on a 20V is 100mm for all rev ranges.

[Gilly]

^^ thats why i posted the pic :lol: the 100mm thing you told me the other day, the reason i thought you'd like this ;)

[rthy]

any ideas on the source of the pics?

might be a rally engine with heaps of power at 6000 RPM or so.

[Gilly]

off road racing buggy from memory

[rthy]

ha! thought so, rally style engine, I would love to hear the owner say what it drives like. Any way to contact him?

[Gilly]

i just saved those pics a few months back i think. pretty sure it was for sale on toymods

[mattysshop]

just somthing of reference.. many many many manufacturers use variable inlet lengths for this exact reason.. some have a secondary set of runners.. some have an extra plenum chamber (3SGE from an SW20 Mr2 comes to mind) all in the name of accoustics, resonance, harmonics.. what ever you want to call it..


also if anybody is interested in custom spun ally trupmets, full bead (lip that curls right around), half bead what ever, made to size..

please email me mathew.cicchitti@racqi.com.au can post aussie wide..

[rthy]

I have written a decent size article with all the info from here and more, here it is:

Intake tuning for multiple throttles (http://www.ae86drivingclub.com.au/faq/index.php/BY_ENGINE/4a/quadtuning)

I am interested in peoples feedback

[SpotterOne]

<div class='quotetop'>QUOTE (Sam_Q @ Jan 9 2008, 11:13 AM) <{POST_SNAPBACK}> (index.php?act=findpost&pid=465481)</div>
I have written a decent size article with all the info from here and more, here it is:

Intake tuning for multiple throttles (http://www.ae86drivingclub.com.au/faq/index.php/BY_ENGINE/4a/quadtuning)

I am interested in peoples feedback[/b]

Just read it, that is excellent.

The only suggestion I have is that there isnt much information of the airbox principle. One of the major failings of the standard plenum on a single throttle body 4AGE is that it isn't big enough, and the engine runs out of air. Most of the airboxes in the pictures aren't much bigger (if any), which would seem to me like it sort of defeating the purpose? Also, there is some wisdom that suggests that the wall directly opposite the end of the trumpets should not be exactly square to the trumpets to prevent additional resonance. I don't know how much difference it makes, but its out there.

I'll use some of that data soon, when I start making my bent trumpets.

Leo

[rthy]

<div class='quotetop'>QUOTE (SpotterOne @ Jan 10 2008, 09:26 AM) <{POST_SNAPBACK}> (index.php?act=findpost&pid=466005)</div>
<div class='quotetop'>QUOTE (Sam_Q @ Jan 9 2008, 11:13 AM) <{POST_SNAPBACK}> (index.php?act=findpost&pid=465481)
I have written a decent size article with all the info from here and more, here it is:

Intake tuning for multiple throttles (http://www.ae86drivingclub.com.au/faq/index.php/BY_ENGINE/4a/quadtuning)

I am interested in peoples feedback[/b]

Just read it, that is excellent.

The only suggestion I have is that there isnt much information of the airbox principle. One of the major failings of the standard plenum on a single throttle body 4AGE is that it isn't big enough, and the engine runs out of air. Most of the airboxes in the pictures aren't much bigger (if any), which would seem to me like it sort of defeating the purpose? Also, there is some wisdom that suggests that the wall directly opposite the end of the trumpets should not be exactly square to the trumpets to prevent additional resonance. I don't know how much difference it makes, but its out there.

I'll use some of that data soon, when I start making my bent trumpets.

Leo
[/b][/quote]

thanks Leo, you have some interesting points, but apart from the section where I say the rough rule is that the airbox should be equal to the engine displacement I was unsure what elese to add, theres just too much contraversy in that area. Also your sujestion about the outer wall of the airbox being parallel to the opening is something I havent ever heard of it and I never thought of. I would take an eductated guess and say your right on this one though because even though theres nothing to back it up it makes sense. I just had a brain wave, I have a book that has some good information and a diagram of what is ideal, I will re-read it and write my own version of it with my own diagram. Thanks for the tips

[SpotterOne]

<div class='quotetop'>QUOTE (Sam_Q @ Jan 10 2008, 03:11 PM) <{POST_SNAPBACK}> (index.php?act=findpost&pid=466220)</div>
thanks Leo, you have some interesting points, but apart from the section where I say the rough rule is that the airbox should be equal to the engine displacement I was unsure what elese to add, theres just too much contraversy in that area. Also your sujestion about the outer wall of the airbox being parallel to the opening is something I havent ever heard of it and I never thought of. I would take an eductated guess and say your right on this one though because even though theres nothing to back it up it makes sense. I just had a brain wave, I have a book that has some good information and a diagram of what is ideal, I will re-read it and write my own version of it with my own diagram. Thanks for the tips[/b]

Cool. I should probably clarify what I MEANT and couldn't get out in print!

What I was thinking was that the standard plenum/intake is probably in the region of 1.6lt, which fits in with the stated ideal, but I think your statement regarding "bigger is better" is more correct. Dyno graphs of 4AGE's with a small amount of help in breathing (ie extractors) often show a dip at the top of the rev range, most likely due to it running out of air in the plenum. That is with a standard single throttle body, so the theory stands that with all the extra breathing from the ITB's, more air is required, and hence and even BIGGER airbox being required.

I dont know how much the effect of the perpendicular wall theory affects the standing waves, but if it isnt any harder to put a 5 degree angle on it, how could it hurt? The theory makes perfect sense to me from when I used to play with subwoofer boxes (MANY years ago!) where you would purposely change the angles to stop the box from "booming". Those waves weren't standing though, and a whole lot bigger, so I don't know how relevant it is.

[rthy]

yeah I hear you, I will try and write something in soon and that diagram I was talking about

[ae86rally]

So after reading this I thought I might post a pic or two of mine


pics in next post


they are nearly 350mm long and any on who thinks is doesnt rev better come for a drive. it has a rev limiter set at 7800 rpm for longevity of the motor it would rev way past it easily, you don't even see the shift light in first gear!!.
quote from the guy who had them designed

o Inlet manifold rocks. Currently in long trumpet mode (13.9inches from valve head) for mid range torque. Shorten to 12” at the trumpet end for 10%+ more power. But it simply harder to drive with short trumpets made easier if you have a different diff ratio. Long trumpets = 4.5K – 7K power range (as per the cam specs – 288 deg.duration, 7.5mm of lift). Short trumpets: 5.8K – 7K+.

edit - current ratio 4.875:1

to drive the car, its a dog below 3000 understeers, then starts to get going but when it hits @3800 it transforms, it takes off with a kick (I used to drive high powered 6 and 8 cylinders before this) the balance and steering of the car transforms into the easiest car ive ever driven, change to second at @7600 (no need to rev it any harder but you could if you wanted to)and it accelerates just as fast, have run out of road before I've had a chance to wind it out in third. custom close ratio box helps too.

[ae86rally]

http://i185.photobucket.com/albums/x158/vkdude/28012008.jpg

http://www.ae86drivingclub.com.au/dcimages/4/8/4/3/163482.jpg

[rthy]

interesting...

thanks for the pics and info

[Gunner]

another option for bell mouths could be jelly moulds, havent tried it but alot of size and degree of roll on the moulds make it worth while to look into.

[rthy]

I will have a look at that, thanks for the tip

[Anthony]

My only contribution to this topic is to pass on information given to me by someone who has spent many thousands of hours on a flow bench. According to him the magic number for the taper of an inlet tract to the throttle plate is 7 degrees.

You can take from that what you will, but if you're lucky enough to be including tapered bores in your next big induction project- go with 7 :)

[Ru-iki]

On the topic of bell mouths, I have a friend who is seriously into tuning his wrx. It has a fully custom and immaculately presented turbo steup, which includes a pair of plenum chambers he had made himself, after exhaustive flow bench testing.

For his setup, he has found offsetting the inlet runners from the chamber to give an angled oval mouth was very effective, not in increasing flow,but in making even airflow from one runner to the next. He claims about 3-4 percent variance in the volume which he can flow from the first runner to the second.

Secondly, he has exhaustively tested trumpet designs, with the idea he would include them in his plenums, and made a very good point about the bell mouth design. His tests indicated that the rim of the trumpet is one of the most restrictive areas. What his tests have shown is that a large share of the air drawn in to the opening has come from around the lip. So it effectively turns the corner around the bellmouth, up to around 180 degrees and accelerates as it does so.

I did some basic vacuum tests for myself and was able to observe this.

There was a lot of air drawing around the lip and very little observed to be straight in and down the funnel.

To me this means that two things are important.

- You need an excellent heat shield under the trumpets to allow cold air to be drawn from this location, closer to the heat of the engine, hence my massive tray.
- You need a smoothly machined lip with no hollow cast underside. i'd like to ee someone machine a teardrop shape on the lip and see some footage of how it flows, I think it would be very very good.

Once I truly considered why this might happen, Ive come up with a basic theory, and it relates to the pressure difference to the inlet runner and engine bay and surrounding air, of course.

Air doesn't have to be drawn in a linear sense, when there is a pressure difference between two areas, you will see all the nearby air within the surrounding area attempting to rush to the low pressure area, despite the barriers and obstructions in the way.

In this case the suction is created by the engines thirst for air.

Just as with our weather, wind is created by pressure differences and the resulting movement of air in a never ending attempt to equalise pressure.

I therefore think that even though the air around the trumpet itself and under the bellmouth is seemingly facing a difficult path, its point to point distance may only be a few mm from the low pressure area, therefore its being pulled up around and into the bellmouth by the pressure difference. This air is attempting to make its way into the inlet runner in the same amount of time as the air with an easy path above the the mouth, therefore it accelerates to do so. Air is such a flexible medium that it can be pulled around corners, and with some decent velocity too. Try it for yourself!!

I know my explanations aren't super scientific, but I though that this was an interesting point which hadnt been made yet, with the discussion focussing on inlet runner length primarily. Feel free to critique my theorys, as I'm always after a new perspective.

My inlet at the moment...

[rthy]

<div class='quotetop'>QUOTE (Ru-iki @ Feb 9 2008, 11:04 AM) <{POST_SNAPBACK}> (index.php?act=findpost&pid=482863)</div>
For his setup, he has found offsetting the inlet runners from the chamber to give an angled oval mouth was very effective, not in increasing flow,but in making even airflow from one runner to the next. He claims about 3-4 percent variance in the volume which he can flow from the first runner to the second.[/b]

any chance you can describe this for me more as I don't quite understand

[Ru-iki]

<div class='quotetop'>QUOTE (Sam_Q @ Feb 9 2008, 10:30 AM) <{POST_SNAPBACK}> (index.php?act=findpost&pid=482870)</div>
<div class='quotetop'>QUOTE (Ru-iki @ Feb 9 2008, 11:04 AM) <{POST_SNAPBACK}> (index.php?act=findpost&pid=482863)
For his setup, he has found offsetting the inlet runners from the chamber to give an angled oval mouth was very effective, not in increasing flow,but in making even airflow from one runner to the next. He claims about 3-4 percent variance in the volume which he can flow from the first runner to the second.[/b]

any chance you can describe this for me more as I don't quite understand
[/b][/quote]


Here is a diagram I made for you in paint. Should explain what I mean...

[rthy]

oh yeah I get it, thanks for that

[Gunner]

anythin ever come of the jelly moulds?

[rthy]

damn, I forgot to look

[SpotterOne]

For those of you that are looking at ram tubes and the like, I found this site:

http://www.elettra.com.au/spinnings/new_page_1.htm

They have bare ram tubes that you should be able to make fit to silvertop throttle bodies. They also have aluminium donuts that you can use to turn the ram tube to clear master cylinders and the like.

I've ordered some ram tubes and some donuts to make up a set to suit my car. I think they were under $30 each, which is not too bad. Only problem is that you need an AC Tig welder or a mig setup for aluminium.

Leo

[rthy]

hey good work, can you post some pics when you get them?

[Gunner]

they've got the 50mm ones to theyll fit blacktop throttles for thos who care

[SpotterOne]

Got a package in the post today from Elettra.

The trumpets I got are the 49mm x 230mm long versions. They were $54 each. The donuts were $22.50 each.

I did some measurements, and have some numbers for a 16v.

Valve face to edge of the head - 80mm
Average distance* from valve face to outside edge of silvertop throttle bodies with a smallport T3 adaptor - 220mm.

*Average distances are quoted because of the taper and bend in the port

T3 Trumpets are 75mm high.

By my calculations, the ideal length for trumpets is in the 380 - 400mm range, so another 105mm (max) needs to be found. Plan is to chop up the donuts as required to get the bend angle right, then chop down the trumpets to suit and weld it all together.

I've attached some pics for an idea of what you get from elettra. The material is pretty thin, but its only supporting an air filter pod. They look nicely made, and will have plenty of room for me to cut bits off for straight bits. The short trumpet is a T3 item.

Leo

[attachment=22939:tn_DSC00387.JPG]

[attachment=22940:tn_DSC00388.JPG]

[350hp4agte]

i plan in the near future to build a turbo plenum for my 20v not using quads using a single 90mm throttle body if i were to make the runners to the head as long as possible should this in theory help in lowering lag time
i assume that having long runners once on boost wouldn't make to much difference as air is forced in but should help to build boost quicker

your thoughts

[rthy]

thats exactly what my theory has been for a long time, others have also said that harmonic resonance is a small factor under boost.

Please let us know how it works out if you ever do it

[350hp4agte]

yeh I'm keen to give it a go and I'm definatly getting a plenum made i'll spec it how i want it so keen to give it a go

[Ke70alex]

<div class='quotetop'>QUOTE (350hp4agte @ Mar 10 2008, 05:39 PM) <{POST_SNAPBACK}> (index.php?act=findpost&pid=499822)</div>
yeh I'm keen to give it a go and I'm definatly getting a plenum made i'll spec it how i want it so keen to give it a go[/b]


there was a story AGES ago in zoom i think it was where they were building a killer taxi, basically the guy had too much spare time and wanted to put an rb20 turbs in a vr taxi. Come hell or high water he was going to use a modified rb26 inlet plenum, without the 6 throttles I'm pretty sure. The result was an absolute dog to drive with MASSIVE torque holes. They then put the standard rb20 gobber on and the engine ran a million bucks :)

they put it down to the short runners on the rb26 being optimised for top end and 2 small turbs and this led to the 2l inline 6 sucking all the air out of the short runners befor the turbo could pump replacement in - if that makes sense. The longer runners provided a much better cusion to draw from.

[rthy]

yeah thats true I remember that now, man that was a while ago. I could be the rb26 intake has much larger diameter runners though.

[350hp4agte]

would the size of the plenum its self make any difference (remember 90mm throttle not quads)

[rthy]

its meant to, they say the minimum 1 to 1.5x the displacement of the engine

[350hp4agte]

so max volume is best?

[rthy]

as a rough rule it seems like it, a bit hard practically for us right hand drivers though. The americans have got it easy in that regard they have no brake booster/clutch gear on that side to hinder them.

[Ru-iki]

<div class='quotetop'>QUOTE (Sam_Q @ Mar 12 2008, 09:36 PM) <{POST_SNAPBACK}> (index.php?act=findpost&pid=501173)</div>
as a rough rule it seems like it, a bit hard practically for us right hand drivers though. The americans have got it easy in that regard they have no brake booster/clutch gear on that side to hinder them.[/b]


Amen sam. Need clearance badly.

[Gilly]

yep definately the only cool thing about LHD

my trumpets wear their RHD scars with pride hey Matt :P

[Ru-iki]

<div class='quotetop'>QUOTE (Gilly @ Mar 12 2008, 11:12 PM) <{POST_SNAPBACK}> (index.php?act=findpost&pid=501272)</div>
yep definately the only cool thing about LHD

my trumpets wear their RHD scars with pride hey Matt :P[/b]


Rofl. :lol:

I think I did a pretty tidy job.

[rthy]

I might of mentioned thi sbefore but for my new engine I am building I am looking to have level throttles and then have each of the intake pipes curve firstly forward about 30 degrees and then 90 degrees down to a low mount airbox. If I do do that I will have a rubber section for vibration insulation and also for length tuning.

[350hp4agte]

hey sam does a similar theory apply to the exhaust manifold as in length of runners to the colector

[rthy]

massively,

I personally believe that all 4-2-1 off the shelf pipes with the exception of toda "race look" don't make much use of it compared to what they could and 4-1 pipes are just about all too short for ideal use aswell. I am planning some extractors that have 4 primary pipes 750mm long with some curved F1 style merge colectors into a flange for an inter-changable secondary set of pipes. I have a theory on secondary pipe length but I can't prove it so I am going to try and make about 5 different sets and then do some testing. It will take time and of course I will let people know the results. However I have a hunch that I need a 250mm secondary set of pipes.

heres some more information:

http://www.my-acoustic.com/Car/intake_exha...ust/exhaust.htm (http://www.my-acoustic.com/Car/intake_exhaust/exhaust/exhaust.htm)

http://www.my-acoustic.com/Car/intake_exha...st/exhaust2.htm (http://www.my-acoustic.com/Car/intake_exhaust/exhaust/exhaust2.htm)


and this is a calculator however you need your cam timing specs for it to work.

http://www.btinternet.com/~rshearwood/calculator.html

[350hp4agte]

what about turbo aplications is it the same sort of deal or a little different

[rthy]

well acording to hpi or zoom (can't remember which) and they said longer manifold pipes makes for more top end but more lag. I however have no idea at all how this is possible, as far as i know with boost harmonic resonance goes out the window and just isnt a relevant factor anymore.

[Ke70alex]

my understanding of this was that it is more concerned with having the pulses arrive at the compressor without interfering with each other,

ie in a firing sequence 4,2,3,1 that is the order they will hit the impeller in. This usually results in more lag but a supposed boost in a tuned frequencey *a very narrow band where the efficiency is imroved. The lag is a result of the "primaries" needing to be long enough in a squiggle to match each other.

standard tube manifolds come on much faster, usually as they have MUCH shorter primaries.

from what i have read this is not a "longer path" problem as such, more to do with a combination of the loss of thermal strength due to the extra distance, but also the materials of the exhaust. The log manifolds are usually steam piping or forged iron and m"insulate" the exhaust pulses better so they retain more thermal energy. The aftermarket tuned legth manifolds are uaually stainless steel and quite thin, they lose heat really well!

that all being said, zoom have maintianed several times that they have NEVER seen and improvement anywhere on a engine fitted with tuned length manifolds ( this is from memory so i could be mistaken). Autobling however found substantial midrange improvemnets on a forrester fitted with xforce tuned length manifold.

[rthy]

yeah well I will stay away from this argument as I am not that familiar with it and i know most of the theory I know goes straight out the window when the old snail is involved.

That said though it looks like the 6boost manifold design is ideal for making boost at the lowest revs and the highest power. But this is another topic all together.

[Gunner]

"Autobling however found substantial midrange improvemnets on a forrester fitted with xforce tuned length manifold." impossible. I have worked on and built, the fastest subis in the land, and x force extractors will loose midrange. And only give up to approx 5kw in the top end, the only time i have seen then work through the entire rev range is with group a style heads and over 300hp atw. No offence to any one, but autobling is wrong.

I don't know about the resonance and shit but in the real world x force extractors are a waste of $1500

[rthy]

no exhaust resonance makes a difference with boost, having equal length pipes is meant to do something but even that is up for debate.

$1500 is a shitload of cash!!

[Gunner]

then labour lol.

[Ru-iki]

Thought this may be of interest/worth discussing. When I had my car tuned on monday with my new silvertop engin, running Blacktop quads, flywheel, alternator, waterpump, pulley arrangement and Adaptronic with Cop coils, the tuner wanted to see how bad the factory Blacktop velocity stacks were, so he had me remove them and do a run with no filters, he charted the 2 results.

You can see when the air is moving slow its rich and once the velocities are up its lean at the top end. It has a large HP deficit in the mid range rpm and almost 3 more at top. The stated figure is for filters on. Food for thought.

[rthy]

that reminds me I got some hard figures now for people running socks, one person I know tried a dyno run with and without socks and without them he gained 7.5kw. From another source I have heard 7kw, both at the wheels...

Also he found he lost 11kw at the wheels by not having any trumpets at all and just an air box.

[Ru-iki]

<div class='quotetop'>QUOTE (Sam_Q @ Apr 2 2008, 12:17 PM) <{POST_SNAPBACK}> (index.php?act=findpost&pid=511815)</div>
that reminds me I got some hard figures now for people running socks, one person I know tried a dyno run with and without socks and without them he gained 7.5kw. From another source I have heard 7kw, both at the wheels...

Also he found he lost 11kw at the wheels by not having any trumpets at all and just an air box.[/b]

As you can see with mine I lost 2.5KW with socks, trumpets and filters on, but had a stronger midrange although a fair amount of this loss in the mid could be tuned out as it varied the Air fuel ratio significantly. I discussed airboxes with Mr Novak and he wasnt a fan unless its boosted. He also insisted that I get a set of stacks with a taper and pronounced Bellmouth, and actually made mention of the same principle I was talking about where the air is attracted from around the base of the stack. I asked for the ideal taper angle and he said 7-10 degrees.

Personally I like a strong midrange so if I o get stacks they will be quite long, although ultimately the best you could get would be some with an infinitely variable length which shorten with rpm increase.

[af300e]

No trumpets at all could give a marked change, but simply changing the lengths? I don't doubt that it redistributes the power along the curve, in fact I have had some experience with velocity stacks on road bikes.
I think however that the effect of the trumpet lengths is far greater when the engine is at a very high state of tune, Ie. 12.1 comp, 300 deg high lift cams etc. When you compare the R6 (that's the bike with which I have the greatest experience) with its 600cc engine at 120 flywheel hp, it's obviously at a far higher state of tune than say a 4age making 120 hp and therefore the effect of the stacks, is probably greater.
Also, the higher an engine revs, the more marked the effect of the trumpet length. The R6 revved to over 15,000. Most 4age's are lucky to crack 7500. Half the revs, vast difference in air velocity.

Another thing we experimented with was using shorter stacks on 2 cylinders and longer on the other 2. This spreads the power even moreso, but, the bike weighed 170kg, a light car is closer to 1000kg. Most of these minute changes are absorbed by the inertia of the chassis.

Dyno charts comparing trumpets of different lengths would be wonderful.

[Ke70alex]

<div class='quotetop'>QUOTE (gunbz-r @ Mar 15 2008, 07:01 AM) <{POST_SNAPBACK}> (index.php?act=findpost&pid=502284)</div>
"Autobling however found substantial midrange improvemnets on a forrester fitted with xforce tuned length manifold." impossible. I have worked on and built, the fastest subis in the land, and x force extractors will loose midrange. And only give up to approx 5kw in the top end, the only time i have seen then work through the entire rev range is with group a style heads and over 300hp atw. No offence to any one, but autobling is wrong.

I don't know about the resonance and shit but in the real world x force extractors are a waste of $1500[/b]
happy to dig up the dyno results. :) not disagreeing, but they can present the facts that back their argument.

[rthy]

what the hell is wrong with an air-box? I personally think nothing is better, well that is unless the main reason for the install was for the sound..