My gen3 3SGE intake manifold - design and performance

[KinLoud]

This post covers a bit of research I am doing into factory vs modified intake manifolds on my racecar.
It's a pretty long post but this info might help someone designing or modifying an intake.
Feel free to give me feedback and suggestions - including how to present the results of my investigation more clearly in this post and if it is in the wrong part of the forum.

INTRODUCTION
Early 2005 I put the gen3 3SGE into my 1983 AA63 Carina.
I used a W57 gearbox.
To adapt the 3SGE to rwd I had to modify a few things (I will post info about this later).
The engine is mounted upright using factory SA60 crossmember and engine mounts.

INTAKE
I used the factory intake but had to adapt it to rwd. I had to blank off where the original throttle body bolted to as the throttle body would have hit the top of the firewall.
I got part of a V6 camry intake welded to the intake so the throttle body pointed towards the front left of the engine bay.

As the engine is mounted upright, part of the intake sits higher than the bonnet. A hole was cut in the bonnet and hump riveted on to cover the hole. This hump looked a bit ugly!

When I bought another 3SGE to keep as a spare I got a nearly completed MODIFIED 3SGE intake.
Halfway through last racing season (2006) I decided to fit this intake to see how it went. Wayne (vvega) kindly finished the modified intake off for me.
When I raced using the intake I found that I had lost a lot of midrange power. When you changed to the next gear you had to wait until the revs got up to the power band. This resulted in slower lap times.

This is an investigation as to why I lost power.

INTAKE DESIGN PRINCIPALS
Intake design is a complex process. The intake has to fit within the factory engine bay, fit within the manufacturers budget, be durable and give good engine performance (and economy) over a wide rev range.

The length and diameter of the intake runners (individual tubes from the plenum to each intake port in the head) affects the torque (and therefore power) at various rpm.
The LENGTH of the intake runner affects it's "tuning" i.e. the resonance frequencies. This resonance can help increase the amount of air that flows into the cylinder. It can also DECREASE the amount of air if not designed correctly.
A long runner will generally help lower rpm performance, a shorter runner will help higher rpm performance.
Runner length is most often used to even out the torque band of the engine rather than provide a large peak at a particular rpm. This helps provide smooth acceleration.

The DIAMETER of the intake runner affects the speed of the air as is flows towards the intake valve and cylinder. I will give a very simplified explanation.
Small diameter runners leading to a large volume cylinder will give better low rpm performance but at high rpm the diameter will restrict the flow.
Large diameter runners leading to a small volume cylinder will give poor performance at low rpm and average performance at high rpm.

Plenum volume also affects the engine performance. I think this happens in 2 ways:
1 - The volume of air between the throttle and the cylinder affects throttle response. A large volume means it will take longer for the pressure to rise when the throttle is opened. A small volume means it will take a shorter time for the pressure to change. You will hear this described as "throttle response".
2 - The plenum chamber acts as a resonator. This will affect the resonance of the runners and the whole intake system.
Usually the plenum volume is between 50% and 200% of the engine displacement.

FACTORY INTAKE -

The factory gen3 3SGE has a complicated intake manifold. It is made in 2 parts. The shorter part is uncomplicated and bolts to the head. The longer part of the intake is more complex and bolts to the shorter part.

Runner diameter is approx 45mm. The runner cross section changes to an oval shape where it meets the head, approx 55mm x 32mm.
The total length of the intake runner includes the distance from the intake valve to the intake manifold face of the head, 100mm
It has a plenum of approx 1.3L and 4 long runners 430mm in length (530mm total).
At about 1/3 distance from the plenum, 4 very short runners join the long runners. This is the ACIS part of the intake.

These short runners connect to another plenum or resonant chamber (I will call this the ACIS plenum).


This ACIS plenum can be blocked off by butterfly throttle type plates.


The effect of this ACIS plenum is to effectively shorten the intake runners length to 310mm (410mm total).

PLENUM VOLUMES - both the plenum and the ACIS plenum have volumes of approx 1.3L each.

When the ACIS plenum is closed off (ACIS closed) the resonant effect of the intake runners favour low/mid rpm performance.


When the ACIS plenum is open (ACIS open) the resonant effect favours higher rpm.
The ACIS opens at 5000rpm (according to http://toyotaownersclub.com/forums/inde ... 38590&st=0)

FACTORY INTAKE PERFORMANCE
Power delivery with this intake is good and even thoughout the rpm range.

MODIFIED INTAKE
This intake uses the shorter part of the 2 part factory intake. A plenum has been welded on the the end of the runners. The plenum has a flange to mount the throttle body. Runner length 200mm (300mm total).
Plenum volume - approx 2.2L




MODIFIED INTAKE PERFORMANCE
Power delivery is poor below 5800rpm. Above 5800rpm the power delivery is similar to the factory intake.

INVESTIGATION
I decided to do a bit of investigation into the resonance of the factory and modified intake. I hoped to understand why the modified intake performed so poorly in the low and mid rpm range.
Method.
I measured the length of the various runners and the volume of the plenums.
I placed a speaker very close to one of the intake runners and blocked off the other runners to simulate the valves of the other cylinders being closed. I then placed a microphone inside the plenum next to the active runner.
Using ToneGen program I played sinewaves of varying frequency through the speaker.
AudioXplorer was used to analyse the signal from the microphone.
The data was entered into an Excel spreadsheet.
A test was also conducted without any intake (microphone and speaker only) to get data on the natural resonance of the room. These measurements were subtracted from the intake data to give more correct results.

You can see that all 3 lines have a broad peak from approx 80Hz to220Hz. The modified intake has a much larger peak than the others in this frequency range. I suspect this might be due to the larger plenum volume (2.2L) vs the factory plenum (1.3L)
The factory intake shows another peak around 310Hz for both ACIS Closed and Open, this is due to the basic resonance of the long runners.
At around 570Hz there is another peak for the ACIS Open, this will be caused by the effective shorter runner created by the ACIS butterfly valves opening up the ACIS plenum.

The testing I did on the resonance of the intakes was as scientific as I could easily manage. I made an effort to reduce errors and outside effects.
I have not investigated the effect of different size plenums as this would have made the process much more difficult.

COMPARISON WITH FORMULA TECHNIQUES
As a comparison I entered the intake runner lengths into a formula.

Resonant rpm for intake runner:
RPM = k/L
where
k = 79200 (constant), L (inches) http://pweb.jps.net/~snowbum/InExTuning.htm
OR
k = 84000 (constant), L (inches) http://www.allpar.com/history/memories/bob-scott.html

INTAKE LENGTH TUNED RPM
Intake runner length - Resonant RPM
530mm ACIS closed - 3796 to 4025 rpm
410mm ACIS open - 4907 to 5204 rpm
300mm Modified intake - 6706 to 7112 rpm
I understand that for best overall performance the tuned RPM should be approx 1000rpm lower than peak power rpm. This will give a wider power band and improve overall acceleration.

CONCLUSION
The short runners of the modified intake create a powerband at high rpm and much lower power at mid rpm.
I will be better off using the factory intake. Acceleration out of corners will be much better.
Possibly I could modify the factory intake by shortening the runners so the power bands with ACIS Closed and Open are raised by approx 1000rpm. This could improve power in the rev range that I use when racing.

Great description of intake design
http://www.team-integra.net/sections/ar ... icleID=466

Good comments on runner length and plenum size: look on page 120,
http://books.google.com/books?id=ze_w0i ... zrQT44LMws

BACKGROUND
In August 2002 I bought a dereg AA63 Carina with an almost dead engine (barely ran, loads of smoke!)
The AA63 Carina had from factory an early 4age (bluetop bigport), T50, 4 wheel disk brakes and independant rear suspension (IRS)
With full interior and aircon it weighed 1060kg.
After removing interior and sound deadening, replacing side and rear windows with polycarbonate and installing a full rollcage it weighed 960kg.
I raced it with the 4age and T50 for 2 seasons. I won my saloons group 3 clubracing class at Taupo in my second season (2004).
During 2004 I bought a crashed 1995 Toyota Curren with gen3 3SGE, E56 lsd gearbox, ABS, Superstrut suspension with the bigger brakes.

Ken
Ham
021 408 863

[vvega]

nice ken
who welded that imaqulate but useless modded manifold for you :d

[KinLoud]

Not useless - It would be great for a turbo setup... bigger plenum, shorter runners suit boost.
Or fabulous for a 2L Touring Car that revs to 8500rpm (instead of 7250)

Ken
Ham
021 408 863

[Caveman]

Very interesting read

Thanks for your efforts and contributions to the forum

[RedMist]

Ken, of more interest is the fact that your experiments appear to prove that the pressure waves of air in the intake runners is traveling at the speed of sound. Which I had thought to be untrue.
I'm very interested in your working calculations and why constant K is introduced, as it appears to be a variable rather than a constant in order to fudge the calculations.
The Helmholtz calculations I performed suggested even longer runners in order to get my required peak RPM. Silvertop manifold and TB's.

[strx7]

Hiya Ken,

So what can you tell me about my new inlet system.













Due to the factory l.i.m the runners are slightly different lengths.
the shortest - no4 is 425mm, the longest no1 is 485mm.
plenum chamber volume is 1.6 times engine capacity.

[fivebob]

Ken, of more interest is the fact that your experiments appear to prove that the pressure waves of air in the intake runners is traveling at the speed of sound. Which I had thought to be untrue.

Pressure waves always travel at local acoustic velocity, however that shouldn't be confused with (steady state?) flow.

On looking at the graph, there are three peaks which is what I would expect. However the frequency measured seems to be too high to be useful Is this because it's measuring the harmonic not the base frequency? Or is there something else I'm missing.

[Celica RA45]

from a factory point of view most engines are only driven from idle up to say 4000 rpm ,so they work out the best torque for that range .
what you could do if you have lost power would be to change your headers ,extractors
on my altezza motor with a inlet length of 165mm to tip of ram tube power starts at 5000 rpm with pipes that are 500mm long and 400mm secondarys .
new pipes 800 mm long and then 300 secondarys ,power is now from 3500 up to 8800 rpm easier to drive
also with a inlet length of 225 mm and 400 mm pipes with 500 secondarys power is down to 3000 rpm up wards ,finishes at 7200 rpm
on my new motor we have kept the 800 mm pipes and 300 secondarys also have gone to 225 inlet to tip of ram tube and also gone to 2 stage injection with power from 4000 all the way to 8500 rpm instead of 9000 rpm ,
its something you will need to experiment with and the same with sizes as well you can try 45mm ,50 mm and also bigger
my pipes for my motor are 50 mm primaries 55 on the secondarys and from there to 60mm and out to the back of car 75mm with 1 muffler .
also your motor having pipes you need to go up 1 size from the factory size if it is std you could try 1 3/4 on the primiares and go to either 1 7/8 or 2inch for the secondaries and then 2 1/4 out to 3 inch to the back

[KinLoud]

strx7 - You new intake looks good. It should keep you very happy.

Celica RA45 - Thanks for your comments, I'd love to have the budget/time to work an engine up on a dyno properly.
My racecar is designed to be cheap and reliable so the engine is factory as is the computer. Custom tuned exhaust to bring the peak torque up a bit in the rpm.
In the future I might go for a full house motor etc. but my aim at the moment is to keep it simple.

Ken
Ham
021 408 863

[vvega]

ken come get my beams intake...id be interested to see teh results from that....i have a mr2 turbo one as well so we can ad some more to the list......oh and a sr20det quad setup....shame i dont have teh 1uz setup anymore

[Celica RA45]

well use a altezza headers and pipes and try that then ,gives you a different idea and keeps it cheap as well if you can do most of the work your self

[vvega]

well use a altezza headers and pipes and try that then ,gives you a different idea and keeps it cheap as well if you can do most of the work your self

there just pressed steel and teh re glues togeather so not really that keen on putting boost though it
besides i was meaning for the table of data and collation
if i want a manifold of anysort ill just make it ....

[KinLoud]

RedMist -
k in the formulas I found - seem in both cases to be a combination of a simplification of theory and observations from dyno work. The websites I refer to will help to explain why I think this is true.
A true theoretical formula includes the position/timing/phasing of the intake valve opening and closing. Even then dyno time is needed to finetune the designers best guess!
Speed of sound - yeah... but the pulses that are affected by runner length are created by the intake valve closing.

fivebob -
Yes I had similar thoughts initially about wavelengths and the fundamental rpm/frequency.
From my research it seems that the runners are related the the 1/2 wavelength of one of the harmonics.
One text says that the wave created by the intake valve closing travels up and down the runner 6 times while the valve is closed before helping to fill the cylinder as the valve opens.
It would be possible to have a runner that was the 1/2 fundamental wavelength but it would be several metres long?
6000rpm = 3000 closings of a single intake valve (3000 pulses) = 3000/60 = 50Hz (50 cycles per second)
speed of sound approx 340m/s so wavelength for 50Hz = 340/50 = 6.8metres
1/2 wavelength = 3.4 metres. Church pipe organ territory!
This would be extremely impressive sticking out of a bonnet but would have large losses due to slowing of the airflow due to the long tube/surface area.
3.4 metres divided by 6 (6 times up and down the runner) divided by 2 (1/2 wavelength) = 283mm runner length total for 6000rpm.
This doesn't take into account the extra length to account for the reflection point of an open tube is out beyond the end of the tube (0.6 times tube radius?) can't find the reference at the moment sorry.
It also doesn't necessarily allow for longer/shorter length needed to match the valve opening timing.

From the formulas I posted above 283mm gives between 7100 and 7500 rpm vs 6000 from basic resonant length theory - you can see that there is still some variables that I don't understand yet (or mistakes I haven't found yet).

Ken
Ham
021 408 863

[RomanV]

Ken as you know I've got RWD and FWD gen 4 3SGE intake manifolds here, if you wanted to have a play.

BTW, I dont understand what the graphs mean?

I'm guessing that the hz frequency down the bottom correlates with RPM, and the vertical scale is... I dont know.

[KinLoud]

Hi Dave - thanks for the offer of intakes to test. I might take you up on that.
The vertical scale is millivolts, showing the output of the microphone. The louder the sound the higher the voltage from the mic.
Testing the resonant frequency won't necessarily predict performance on an engine (need a dyno dammit) but it does give a quantifiable and (hopefully) repeatable test to give some comparison between intakes.

Just thinking - I need to do another test as I think the way I tested the intakes ended up with effectively both ends of the tube open which probably gives a different resonant frequency. I will check this theory with an adjustable length of vacuum cleaner pipe (easier to deal with than an intake) and compare both ends open with one end closed.

Ken
Ham
021 408 863

[DFECTED]

KinLoud, the first thing I noticed with your manifold regarding harmonics and air flow, etc is that when the air goes in through the throttle body it hits the roof of the manifold, then its as if its got to twist and change direction completly to make it down the runners, especially the front two. Surely these changes of air flow direction add to the harmonics etc

If you compare that to the factory designed manifold all the curves are nice, long, smooth and flow

[KinLoud]

Yes the modified intake has a bit of an angle from the throttle body to the plenum, but I don't think that is the reason that it is crap at low rpm and great at high rpm. Basically the runners aren't the right length to produce decent lid range power. The angle of the throttle body might cause #1 cylinder to get less airflow and run rich.
When I got the intake it was all fabricated but some bits of the plenum hadn't been welded up. The guy was going to fit his 3sge into an AE85 but sold the motor etc. to me instead.

Ken
Ham
021 408 863

[Celica RA45]

what about a frasier inlet and a 2nd hand set of quads as in black top 1s the std ecu could still run this set up, as one of your guys in nz had a similar setup on his gen 2 3sge motor just an idea and i know your on a budget