Any manufacturer can claim a small hp gain but this would be so hard to prove that such a claim is easy to make. So you install your plenum and fail to make any gains on the dyno...oh well...different car, different other mods, different dyno, different air temp, different humidity,etc, etc,etc. I know the theory that the forward slope restricts airflow to the forward cylinders, but does it really? A plenum functions like an"air capacitor"and is basically a low velocity structure overall. One could also argue that to maintain airflow into the forward intake runners, which are father from the air source, one needs to taper the plenum to maintain some sort of air velocity. Can someone show me the data to actually show better airflow within the forward intake runners with an altered plenum design over stock?

 

I doubt most fabrication shops have the instrumentation required to perform airflow/volume tests like that. If there is data I'd like to see it, but why can't you just takes the 59 pages of positive discussion on the forum and assume that counts for something?

 

Just wondering where the idea came from that the stock plenum was deficient. I'm also just the type who questions everything until I know all the facts.

 

lol

try searching there is heaps of info on both the kinetix and a whole lot more info on the crawford, including dynoes.

i believe that they do make a difference on a car but less so than say a good set of headers or cams. on par with a catback or good intake for similar gains.

 

I believe Crawford did flow tests on the cylinder heads and found them to be quite efficient. When they added the plenum they saw the airflow problems to the front cylinders. This design of course was not due to the performance issue but due to hood clearance on the Z. I am sure if they could they would have an equal volume plenum design.

 

We came to our conclusions about the stock "intake" flow back in late 2002 after several flow bench tests. The whole project was originally to make a set of long equal length headers, however we stumbled on the intake issue when testing a donor 3.5L VQ engine on the flow bench.

We ran the ugliest plenums you ever saw for a while until we were satisfied that this was a viable modification. The we started production of the 2nd ugliest plenums you ever saw :P. Now the plenums are looking very good and other companies (SSR, Kinetix) have since followed with aftermarket plenums and plenum development.

If you want to search it may be easier to search posts by either "dougrace zs" or myself. We posted all the technical and general flow bench information back then. No specifics as you might guess for business reasons, but there is plenty of information on the topic.

 

At a local dyno get together the two guys with plenums dyno 7-10hp more than everyone else with similar mods.

 

I just had an idea. I have one of those laser temp sensors in my shop and I will check the temps on each header pipe to see if the front two cylinders are in fact running rich(colder). If someone can do the same thing with their kinetix/crawford, we can see if there is a difference.

Someone tell me if this is a good/bad idea.

 

Someone on the forum was having some internal engine work done and upon tear down they found the front two cylinders had been running very rich, running stock plenum. He posted pictures of the piston heads in the engine and the front two were black compared to the other 4. He bought an aftermarket plenum after seeing this.

 

Like yourself I was also a skeptic about the claims made by the Mfr as well as those that installed one. I bought and installed a Kinetix and a skeptic I am no more. Dont need to dyno to be convinced it made a significant improvement above 4k. Don't know if its optimized in design and would probably take a small kings ransom for a mfr to determine it..Other than design problems with Kinetix I have not seen where anyone complained about its performance or lack thereof..

 

no

 

all I can say is that after strapping mine on the car went much faster. As a matter of fact (or my opinion) it was the best add on I have for additional power. (I dyno'ed an additional 13 or so horses after install, one week apart, same time of day, almost same temp)

 

If you do a search under my name, you might find another perspective about plenums.

Crawford presented me with a nice offer as part of an independent test. The test results were blemished by the fact that before testing, an AEM intake was a modification already in place. And, the long plumbing of the AEM, frankly, isn't helpful.

Gains were modest and in my opinion, simply not worth the expense in terms of $/hp. Fact of the matter is, short of an expensive stroker kit, pretty much any NA modification will produce very modest gains. I think Jeff's Z pretty much outlines the upper limits of NA modification. We're talking less than 50 hp gains after installation of pretty much everything but the kitchen sink. That being the case, it makes sense to pick and choose the best value mods.

In my opinion, only certain NA modifications are worthwhile before FI makes more sense. Those mods include: JWT intake, UR pulley, exhaust and probably the biggest bang for the buck, either highflow cats or testpipes (w/resonators if you can't stand rasp). Headers and cams aren't worthwhile considering unit cost and installation cost relative to gains.

Plenums are probably a better value than headers or cams because they can be self-installed rather easily within a hour. Between Kinetix and Crawford, I'd go with more durable metal over plastic. However, I don't like the idea of replacing the stock strut brace. And, I still think that the plenum just doesn't produce enough gains to justify the expense. If the Crawford plenum ever reaches a price of $250 and, if they can figure out how to put it under the stock strut brace, that will be the time to add it to the shopping list.

 

sorry for going off-topic, but someone said there is a significant gain above 4000. Is there any kind of sound change to go with that?

 

I read about this too ... I was thinking about keeping my car stock but after reading this I am seriously considering getting either the Crawford or Kinetix.

Saving your 2 front pistons from turning "black" earlier than the other pistons is my main concern... the fact that these aftermarket plenums make additional HP is icing on the cake.

 

I have both the Popcharger and the Kinetix plenum. The popcharger alone was awesome and coupled with the plenum the engine is even louder..The sound is like it has a much more powerful engine than it really has. Cruising in 4th gear its very very noticeable!

 

To me, the key element of the upgraded Plenum is to more closely equalize A/F ratios between the cylinders. Especially with F/I, these engines are always on the verge of detonation. If I can gain a few whp across the board...or even in just certain areas...that would be gravy to me....but increased hp is not my primary motivation.

Doug/Crawford:

It's not too late to send me a plenum for this weekends dyno. I will do a before and after at 9psi with the Greddy kit (easily over 400whp). Should be exciting if you can make it happen. And I'll post a full writup on the results.

PM me if you wanna work something out still.