I am trying to decide if I would benefit with my current TT with a crawford plenum. Now I am using the stock plenum, and since I am forcing the air into the camber will a crawford plenum make a difference?
Enough of a difference for the cost?

 

I think it made a difference in my car (SC), I am sure mixed reviews will be given. I like the idea of having even air distribution across all 6 cylinders. Before Doug sent mine out I had him install 2 extra vacuum ports for gauges and timing equipment.

 

I went with the Crawford unit just to be safe. Do I know for certain that not running it would be unsafe? No. In fact, I have seen alot of TT cars with the stock plenum. I do know that the OEM plenum does not evenly distribute the air to the front cylinders so, it is more for my own comfort level.

 

I have one....definately made an improvement in my dynos. I did some back to back dynos, and simply changing plenums and fresh spark plugs netted me 36hp at the peak, and about 40hp and lbs of trq across the power band! I was stunned!

Be careful though...the plenum will likely lean out your car .5 to 1.0 A/F points across the board. So a retune will be needed.

 

GQ, or anyone else, do you think a tune would be necessary on a N/A car due to this leaning out of the A/F ratio?

 

Not essential , but a good reflash will keep the ECM from pulling extra timing due to the slightly leaner condition (more knock prevalent).

 

Wow didn't realize a manifold alone on TT would net that much gains. Thats awesome.

 

plenum displacement over stock here will make power.

i have yet to see any proof that any cylinders run leaner then than the rest with stock plenum. Matter of fact, I HIGHLY doubt that it does. The plenum is not divided, the displacement in the back is part of the displacement in the front, there is nothing that would cause the front cylinders to ONLY get air from the front of the plenum... that doesnt make sense. Its phyics, the pressure will drop in the entire plenum every time a set of intake valves open, it doesnt matter where in the plenum you measure it, the entire plenum will drop in pressure or increase in pressure at precisely the same time.

If youw anna look at the flow... the air going to the front cylinders has a straighter path anyway and i would think the front would actually be less starved for air then the rear. So I bet if you wantd to look at static flowbench numbers I would be surprised to see that the front cylinders do not flow greater than the rear. but flowbench doesnt matter here anyway... this is not exactly flow, this is a pressure equalization process. the intake valves open the the pressure is lowr in the cylinder and its actually SUCKING the air from the plenum more than it is being pushed. Boost makes it sound like your forcing it... but your only forcing into the plenum, once those valves open that cylinder is going thru pressure equalization.

the increase in plenum displacement iwll make power because the pressure drop inside the plenum will not be as severe, it has more capacity to equalize pressure between the cylinder and plenum in the short time that it has when the valves are open.

YES the plenum makes power, of course it will... it increased your plenum displacement. as for equalizing the A/F between your cylinders... eh... i highly doubt it does anything of the sort because i highly doubt anything of the sort is even an issue with the stocker. the only time i would worry about this is when the plenum is tiny tiny and has a very biased feed, such as a stock MR2 turbo intake manifold.

HP and airflow are the same thing so technically the MAF sensor should see the increase in air and not run you lean... but at the same time you all have your MAF sensors maxed out anyway so you do need to tune for it.

I would love to argue with someone on this topic that could either tell me if im right or wrong but has some real technical information to support the theory other than how the manifold appears at first eyes glance.

 

I agree with most of your assessment ; however, the MAF can not account for distribution issues from the TB down to the individual intake valves.

The single MAF can only measure an aggregate Mass of air , not individual distributions. So the MAF can account for bulk mass as long as it is allowed to operate within it's designed dynamic range.

Now the fuel on the other hand is distributed in a per cylinder basis via individual port injection. So MAF / 6 is an approximation and assumes that Plenum distribtution be perfect or near perfect.

For low MAF volumes the OEM Plenum is more than likely near perfect. However; at high CFM , (high RPM and/or high boost) this distribtution is most likely less than perfect. Of course until someone outside of Nismo flows the OEM plenum with individual cylinder A/F telemetry , it is mostly conjecture.

But greater more balnced Plenum volume woudl seem to alleviate the high CFM flow issues and not hurt.

 

you misunderstood what i was saying about the MAF. I know the MAF cant tell how much air is going into each cylinder... what I was getting at is that assuming the MAF sensor isnt already maxed out in voltage... if you increase the volumetric efficiency of your engine via a plenum, it will see greater airflow and the ECU can injector more fuel... once again assuming your EFI or MAF systems are not at their capacity.

The entire point of a MAF is its ability to sense changes in volumetric efficieny and run your EFI system accurate as possible. A system like speed density (no MAF, just a MAP and AIT) are what I like to call assumed volumetric efficiency systems. If you were to upgrade your plenum, cams, turbos, intercooler, anything that changes your VE, you need a retune cause there is nothing there that is able to notice the fact that you are pulling in a greater volume of air even tho your MAP pressure isnt any higher.

 

It has been done (many times) and the fronts do have less flow than the rear.

 

So do you think that everycar that is TT that has a new intake manifold installed on it will yield as great of gains as gq's did. Cause that would be awesome. If so that is my next mod.

 

here the before and after on the dyno. First with stock plenum on 8000 miles on the plugs. The After is crawford plenum and fresh plugs. Same outside temp...same dyno....about a week apart...same boost. Take it with a grain of salt, becuase with the low starting number, i might have had a bad plug to begin with. Regardless, the gains look pretty darn good.

http://www.savepic.com/is.php?i=1956...after_jpeg.jpg

 

Well whether or not it was a bad plug, great gain off the plenum. I wasn't really questioning your gain, but just whether or not it seems logical that most TT cars will pick up as much power with a plenum or if yours just reacted exceptionally well to the plenum. One way or another thats alot of performance for not much money.

 

Sorry I have not followed up on your latest mods..

The Crawford Plenum Seems to have increased the volume of available air to the heads. And as Charles has mentioned, when the intake valves open - the engine breaths (sucks) the plenum dry on each intake stroke. Then before the next cylinder intake opens, the plenum must be fully charged from the turbo.

I think this is what Charles was refering to...

However damage was previously detected in Cylinders 5 & 6 with a stock plenum..

So the Crawford/APS style plenum may be the "hot" setup for FI.

Cheers Amy -

Keep up the good work, and let us know how your "built and Forged" project works out for you..

 

002-M-P,
I'll likely be going to the crawford plenum when my engine is pulled and built. From GQ's numbers, it looks like the plenum works real well with the TT. I see that you're having a TT installed real soon. Another power gainer for the TT is the exhaust side. (ie) I made 404 rwhp at 8 psi with the RT high flow cats and Borla exhaust. When I switched to test pipes and the Greddy EVO II exhaust, the Z picked up 40.5 rwhp on the dyno at the same psi. I also beleive ACP saw similar gains with this set up.

 

Yancy, thanks.
I got the test pipes ready to go in as well and am just waiting for the turbo stuff(should be here monday). But later I plan on the Gruppe-S Y-pipe and a custom single tip exhaust using HKS Hiper Ti muffler. I think that will solve any flow problems in the exhaust.

 

Whats better the Crawford V5 plenum or a kinetix version?

 

Without question, I would go with the Crawford V5. The Kenetixs plenums are highly prone to cracking, and I would not trust it with significant positive manifold pressure. That's my personal opinion.

I know that lots of OEM use plastic for their manifolds, but given the track record of the Kenetix plenum and cracking...I would never buy one.

 

Crawford all the way... put HP on N/A and also on TT