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?

<font color=black>2003 G35 Coupe, Blk/Blk</font color=black>
<font color=red>Frisco, TX</font color=red>
TXREFI G35

 

Wait for the APS plenum.

 

Most changes in VE will be directly affected the same way with Forced induction. The volume of air does not change with FI. But the density does as more air is packed into the same volume. Changing the VE will have the same change in volume whether it's FI or NA. The only thing this may not apply to is cams. Particularly when you start playing with a lot of overlap. Cams can help increase VE for FI application, but one that works very well for NA, may not work so well with FI.

 

What is VE? So are you saying the more open plenum of Crawford or APS would help?

<font color=black>2003 G35 Coupe, Blk/Blk</font color=black>
<font color=red>Frisco, TX</font color=red>
TXREFI G35

 

looks like this is what a lot of companies are doing, u guts see the top secret plenum?

 

I THINK VE stands for Volumetric Efficiency. I recall someone using a Crawford for their FI setup but I'm not sure if it was TT or SC. It should certainly help even out the airflow into all the cylinders, IMHO.

 

If you are forcing the air in, how much better could a crawford or etc be, for $500.00?

<font color=black>2003 G35 Coupe, Blk/Blk</font color=black>
<font color=red>Frisco, TX</font color=red>
TXREFI G35

 

TX - I'd guess that since Doug says that the factory plenum restricts airflow to the front cylinders by as much as 30% on a N/A car, then that data would also apply to even an F/I setup. After all, U can only squeeze so much airflow through a fixed orifice ( at a given pressure ). It would seem to imply that the front cylinders won't make as much power ( especially at upper rpms ) as the rear ones due to the lesser airflow. Might try E-mailing Crawford to see if they've done any testing with their plenum on an F/I car.
BTW - Love your car!!

Gene

 

I have the crawford plenum and FI. My engine is blown

I did it mostly for style, and to say I have it. It looks much better on top of the engine then the stock one. And, hell, I drove 5.5 hours to Crawfords shop in Nashville I might as well have something to show for it (you can't see the headers or cats).


Kevin
www.KPtechnologies.net
AIM: KPiersonTec
04 DG Coupe / VDC Memory
OEM Remote Window up mod
Procharged / Crawford / TS

 

And if indeed the front cylinders were deficient in airflow by 30% then the front 2 cylinders would be lower on power by nearly that amount. Considering the front 2 cylinders would be responsible for 33.3% of the motor's power if all cylnders were receiving the same airflow, then the loss in power t the front with a 30% restriction would be 33.3% x 30% = .099999% decrease in power. So essentially you would get aback about 10% of the lost efficiency. 10% seems relatively small. 28 HP on a N/A VQ. But as power rises, that percentage makes a bigger difference in the aggregate power gain. A 400 HP motor would see closer to a 40HP increase. I'm abit skeptical of the 30% figure myself, but I only went with it for the purpose of explaining this.

 

Kevin,

Did you notice any change with the new plenum since you are blown?

Thanks
David G

 

Kpierson, after your engine is blown, did you replace it?

 

NO KIDDING! Time for another PM to Kevin...

 

I have one on my car, and I did back to back dyno testing with my Greddy TT at 8.5psi. The gains were surprisingly large. Roughly 30-40whp across the board. Now, I also changed to a fresh set of plugs, so some of the gains could be attributed to that. But based on my experience, I am a believe in the Crawford plenum for forced induction.

The Plenum did cause me to lean out slighltly, which necessitating a slight retune of my fuel maps...thats the only thing to keep in mind.

 

First of all, there is NO WAY nissan would build a recent engine where two cylinders get 30% less airflow then the rest. That is insane. 3-4%, maybe. Gains from manifold changes do not come from just more equalized air flow per cylinder (although that can help). VE can change quite a bit, and sometimes you will lose some VE in one rpm range while gaining in anothe rrpm range.

Second, yes, turbos DO benefit from different manifold designs (runners, plenum, throttle, etc). There is a big misconception that forced induction is totally different than N/A; they are actually very similar. From a physics standpoint, ALL engines are forced induction. No engine "sucks" air in. Gasses will always try to equalize densities in a common chamber, and thus moves from a high pressure (more dense) to low pressure (less dense), period. In a N/A engine, the piston moving down on the intake stroke creates more volume and therefore lower pressure in the cylinder. The air in the intake manifold, at standard pressure (usually 14.7 psi, yes, air around us IS under pressure) will move inside the cylinder. There is no "sucking" going on. The exact same thing happens with a turbo or supercharger, only difference is the pressure in the intake (and typically also in the cylinder) are higher than N/A applications.