Enlarged Intake manifolds

[CJ]

I have read a lot about the Veilside copies available on E-bay etc but was wondering what sort of gains the larger volume manifolds give and when?

 

Are they fitted to improve top end, low end response or a mixture? Do they actually work on lower spec cars or only the monster BHP American cars? Are other supporting mods necessary to get the best results?

 

Opinions please.

[Guest Usmann A]

you have a 67P trim right? if so, no need at all .. itll just kill your low down response ...

[Matt T]

Apparantly the Veilside mani isnt all that good anyway, marginal gains over stock....

http://www.supraforums.com/forum/showthread.php?t=166026

[CJ]

Apparantly the Veilside mani isnt all that good anyway, marginal gains over stock....

http://www.supraforums.com/forum/showthread.php?t=166026

I thought that test proved that the VW model was far better than the Veilside one? I dont recall them saying that it was not much better than stock.

[CJ]

you have a 67P trim right? if so, no need at all .. itll just kill your low down response ...

Why would you kill low down response? (I am not questioning whether you are right or not, just wondering what it would happen)

 

Are the Americans not reporting this due to them running the VW or Veilside manifolds on big tubbys therefore experiencing lag low down anyway?

[Paul Whiffin]

On my car the VS fanimold had no ill effect on low down power, no loss of response at all, in fact if anything it feels sharper and more responsive, I can only recommend it to anyone with 600+bhp. You've also got the new Greddy intake out as well remember, dont know how good that is until we try/test one here though but knowing Greddy stuff its bound to be good.

[Chris Wilson]

If you are getting to the point where you are into big HP numbers you should be looking at multiple throttle bodies and re designing the manifold to be similar to that of a Skyline RB26 one. Moving to multiple butterflies nearer the ports will aid throttle response, putting a bigger volume surge tank on may well reduce it. It all depends on turbo(s), cams, throttle body size, MAF or MAP and intended use for the engine. Very complex subject.

[Digsy]

If you are getting to the point where you are into big HP numbers you should be looking at multiple throttle bodies and re designing the manifold to be similar to that of a Skyline RB26 one. Moving to multiple butterflies nearer the ports will aid throttle response, putting a bigger volume surge tank on may well reduce it. It all depends on turbo(s), cams, throttle body size, MAF or MAP and intended use for the engine. Very complex subject.

Just to second what Chris has said, our engine simulation guys love their large intake plenums (and I mean daft large, not a few % bigger than stock). However the calibration (mapping) guys hate them because it makes transient response a pig to smooth out.

 

No point in a bolt on aftermarket job IMHO.

[Guest Usmann A]

What Chris says is for the ultimate HP numbers.

 

Pau W, the shorter runners, loose low down response over a stock intake(less air velocity when not at WOT) WHat you are experienceing the huge size of the TB and the masses of air movement it creates at low TP angles.

 

It also depends onthe setup, now what turbo are you running Paul? there is no real need to go this route if your arent bigger than a 74mm.

 

Those tests are flow bench tests, what would be nice is if they could attach them to a ported head, and measure flow at 70% valve lift,this would give us a great insight into how they might flow for real vs driveability

 

The stock intake flows for 9 runs and 1000USRWHP.

[Guest Terry S]

We have been here many times eh guys. IMO the are pointless unless you really are after huge BHP.

[dk_supra]

Wrong , wrong ,wrong, Drive one and then talk about it please. The ebay manifold, (VS copy) has a lot more torque down low than the stock. Starts faster than stock and idles than stock, tuning has it's difficulty, the way i tuned mine, car does donuts, without even on boost.

 

Cheers

Dimitri

 

 

you have a 67P trim right? if so, no need at all .. itll just kill your low down response ...

[Ian C]

Hurrah, another tuning product just as contentious as ECU choice

 

I'd have the Greddy, but only so my lovely HKS fuel rail isn't hidden any more

 

-Ian

 

PS keep it friendly

[Digsy]

Sorry, but no-one is ever going to convince me about aftermarket manifolds until they post up a proper pair of back-to-back torque curves, with ONLY the manifold changed between the two.

 

How on earth can a manifold make a car start and idle faster than stock? The engine is running on the IACV and flowing naff all air, for crying out loud!

 

Although a properly tuned system can look really good on paper, even the effects of multi-mode variable plenums (common on V6 engines) can be hard to actually "feel" in the real world. Yes, wildly different runner lengths can shift the torque curve one way or another but if you optimise it so much that there is an appreciable difference in low down torque then your top end power will be absolutely crucified.

 

Anyway, we are talking about plenum volumes here, aren't we? Plenum tuning does little more than try to even out lumps and bumps in the torque curve. If you want to really move the curve about then you want to be changing the runners, not the plenum volume. And flow bench results won't tell you much because you need to look for harmonics and you won't get those unless you develop one on a running engine.

 

Jeez, you'd have to be flowing HUGE amounts of air to warrant changing the plenum from an airflow perspective, and I can't see the point of going looking for harmonic effects on a forced induction engine.

[Guest Usmann A]

WHat you are experienceing the huge size of the TB and the masses of air movement it creates at low TP angles.

 

 

Wrong , wrong ,wrong, Drive one and then talk about it please. The ebay manifold, (VS copy) has a lot more torque down low than the stock. Starts faster than stock and idles than stock, tuning has it's difficulty, the way i tuned mine, car does donuts, without even on boost.

 

Cheers

Dimitri

 

My quote above .. that is why huge TBs are deemed not 100% road friendly .. they create alot of air movement at small openings ..

 

Easy Darren ...

[dk_supra]

It does because of the volume of air inside.

Next, i don't like the big throttle bodies no oem, i have stated that on this forums and on the ones on the states, I have the Q45 one on my VS copy manifold and i had it on my stock one as well. Now the car can do donuts off boost, before it couldn't period.

 

On my GT42RS turbo, with the stock intake i couldn't run higher than 8000rpm easy (with cams), now it goes all the way to 8.8k-9k rpm without a stumble.

 

I believe the reason why it starts easier, because the air volume available for start up is more. And since i'm using really big inj. i need it. Back to back with the stock, it cranks and starts on half a turn. Mostly with really big inj.

 

Dyno it before and after just with the manifold, i cannot do it, because i installed other things from the last time i dynoed, so now it wouldn't be fare.

 

I already did 572rwhp on pump gas with stock manifold, stock cams, small FMIC, now i have VS copy manifold, 272s, BIG FMIC, and a lot shorter IC pipe work compared to the stock manifold. So even if i see 120-140rwhp more, it would still be not fair.

 

 

 

Sorry, but no-one is ever going to convince me about aftermarket manifolds until they post up a proper pair of back-to-back torque curves, with ONLY the manifold changed between the two.

 

How on earth can a manifold make a car start and idle faster than stock? The engine is running on the IACV and flowing naff all air, for crying out loud!

 

Although a properly tuned system can look really good on paper, even the effects of multi-mode variable plenums (common on V6 engines) can be hard to actually "feel" in the real world. Yes, wildly different runner lengths can shift the torque curve one way or another but if you optimise it so much that there is an appreciable difference in low down torque then your top end power will be absolutely crucified.

 

Anyway, we are talking about plenum volumes here, aren't we? Plenum tuning does little more than try to even out lumps and bumps in the torque curve. If you want to really move the curve about then you want to be changing the runners, not the plenum volume. And flow bench results won't tell you much because you need to look for harmonics and you won't get those unless you develop one on a running engine.

 

Jeez, you'd have to be flowing HUGE amounts of air to warrant changing the plenum from an airflow perspective, and I can't see the point of going looking for harmonic effects on a forced induction engine.

[dk_supra]

Q45 is very road friendly, very progressive, that's why i didn't go to the 100mm one, it would be useless with 80mm IC piping, unless i change it

 

cheers

Dimitri

 

 

My quote above .. that is why huge TBs are deemed not 100% road friendly .. they create alot of air movement at small openings ..

 

Easy Darren ...

[Digsy]

It does because of the volume of air inside.

Next, i don't like the big throttle bodies no oem, i have stated that on this forums and on the ones on the states, I have the Q45 one on my VS copy manifold and i had it on my stock one as well. Now the car can do donuts off boost, before it couldn't period.

 

On my GT42RS turbo, with the stock intake i couldn't run higher than 8000rpm easy (with cams), now it goes all the way to 8.8k-9k rpm without a stumble.

 

I believe the reason why it starts easier, because the air volume available for start up is more. And since i'm using really big inj. i need it. Back to back with the stock, it cranks and starts on half a turn. Mostly with really big inj.

 

Dyno it before and after just with the manifold, i cannot do it, because i installed other things from the last time i dynoed, so now it wouldn't be fare.

 

I already did 572rwhp on pump gas with stock manifold, stock cams, small FMIC, now i have VS copy manifold, 272s, BIG FMIC, and a lot shorter IC pipe work compared to the stock manifold. So even if i see 120-140rwhp more, it would still be not fair.

Ignoring VE effects, your engine will be sucks up 1.5 litres of air every revoluton. At idle (say 800 RPM) that's 1200 litres of air every minute - the same as a stock car.

 

I can see what you are getting at: Your big injectors, even on minimum duty cycle, need more air than stock to stop running rich, and that is probably true, but the fact is that even though there might be more air hanging around on the other side of the intake valves, there is no mechanism at work to actually persuade that air to get into the cylinder.

 

This of course assumes that the stock IACV offers no restriction and is capable of flowing 1200 litres or air, which is must be otherwise all MKIV owners would see idling and startup problems.

 

 

 

Anyway, I'll take my rant hat off for a second to try to get some facts and figures around this.

 

How much bigger volume is your manifold compared to stock? Roughly?

 

When you fitted your larger manifold, what else did you fit at the same time?

[Guest Terry S]

Dimitri's car is not run of the mill tho, 76mm DBB turbo, and he revs it to over 8.5k.

 

CJ, I think you are just fine unless your plans have changed.

[CJ]

Dimitri's car is not run of the mill tho, 76mm DBB turbo, and he revs it to over 8.5k.

 

CJ, I think you are just fine unless your plans have changed.

I have no change of plans (although I do have a newly acquired SP enlarged manifold sitting in my garage) but really was asking the question for BBS information rather than to encourage me either way.

[dk_supra]

How much bigger volume is your manifold compared to stock? Roughly?

 

When you fitted your larger manifold, what else did you fit at the same time?

 

 

I think the new is 4.5-5 lt and the stock is about 2-2.5 without runners of course. And the new one has bigger runners.

 

Larger Manifold was fitted, while oil cooler, BIG FMIC, shorter piping fitted. Nothing else, had the cams and the Q45 TB already before.

 

I think what you are saying about the inj, has a valid point, because when i was tuning my AEM with the VS mani on, i found out that the fueling was around 5% more on lower rpms even on idle to keep the same AFRs as before. Mid range about 7-8%, up high around 8%. Please don't take these figures for granted i said about, not exactly.

 

Dimitri

[Digsy]

I think the new is 4.5-5 lt and the stock is about 2-2.5 without runners of course. And the new one has bigger runners.

 

Larger Manifold was fitted, while oil cooler, BIG FMIC, shorter piping fitted. Nothing else, had the cams and the Q45 TB already before.

By bigger runners do you mean longer or fatter (or both)?

 

Longer would tend to increase low-down torque, whereas fatter would increase top end power (not only because it may flow more air, but because the Helmholz frequency would be increased).

 

What's confusing me is that the main motives for fitting a big plenum seem to be for flowing more air at really high top end power outputs and huge boost, but the starting and idling and "doing donuts off boost" all point to tuning effects for low and mid range torque.

 

I wonder whether the FMIC piping is also having an effect?

[Markie]

I read somewhere that the VS one was designed to make the air more free flowing, not so restriced as the stock. But this may only apply as mentioned above about the big HP numbers.