Even though many users have previously posted about the Cosworth Intake Plenum not performing well on non-FI car, no one has really done a good before and after test. So a few months back I took the plunge and shelled out the premium to get one to hopefully gain some power over my Motordyne 5/16th and MREV2.

As expected from cosworth and any premium items, Build quality, packaging, and looks were top notch.





Installation of the unit was straight forward, other than three things.
1. My box didn't come with a manual so I had to get one faxed from the vendor.
2. Installing the gasket for the carbon cap is really a pain in the butt and would appear to be very susceptible to leaks.
3. The bracket on the passenger side carbon cap is not meant to last. It broke off right after I started the engine. Luckily it's not vital for the operation of the plenum.



After installation, the manifold definitely looks a lot nicer than the stock setup and clears the strut bar much better. Please ignore the dirty engine bay.



Aesthetics aside, how did it perform? Driving the car around a noticeable power loss can be felt down in the lower and mid range. I was quite disappointed to say the least but I never trust my butt dyno so off to the dyno it went. Below is a series of two different test comparing the Cosworth on a fully NA engine.





Based on these tests, it is apparent that the Cosworth is not suited at all for my application so back to the Motordyne setup it is. But I must say that the one performance advantage the Cosworth has over the MD is the ability to sustain power pass 6500rpm... to be continued.

 

Thanks for taking the plunge and actually getting dyno'd and posting some great info.

 

Nice. Another win for Tony

 

did you not see my dyno comparison from 02/08?

https://g35driver.com/forums/2687535-post31.html

https://g35driver.com/forums/intake-...ed-pics-3.html

[QUOTE=jonnylaw;2687535]

Red: MD 5/16 iso spacer, MREV2

Blue: Cosworth Plenum

Breathing mods: Arc intake, Amuse titan tube, nismo headers, PE HFC's, Tanabe y pipe, Amuse Titan exhaust, UR pulleys, Technosquare reflash


All the pulls made today with the cosworth plenum:

 

^ Good thing you posted in here Jonny, I figured you would since you were one of the early adopter of the plenum and it's good to get some more data points on this interesting product.

I've seen your test, but the unsettling area in your test was the tune and the time difference between the tests which didn't sit well with me so I did a series of three tests on my own. One which is not shown here since it was on the engine dyno and comparing it to something different.

 

Understood. I was trying to do another back to back test, this time while F/I. But my tuner is tied up for a couple months, so I'm deciding to just put back on the new Cosworth plenum I just got. Maybe later on, I will do a back to back comparison of the 5/16 spacer/Mrev2 vs Cosworth on my HKS SC setup.

Thx for taking the time to do these tests. It's clear the MD 5/16 spacer/MREV2outperforms the Cosworth on a N/A revup. Gains of the Cosworth on a typical N/A setup are similar to a spacer alone.

Of course we all know, the Cosworth shines on high boost/high rev applications.

 

Definitely looks like Cosworth for NA is neither the best nor the best bang for the buck. Both those titles go to Motordyne. Thanks for sharing.

 

It's the other B though (bling).

 

Sooooooo.... are you looking to sell that Cosworth now?

 

Thanks a lot for this comparison, good information to know. I've been itching to buy the Cosworth for many months now but I've always heard it was a waste of money for NA builds, and this just proves it without a doubt.

I recently bought an Arc airbox and intake tube, so I've pretty much filled my useless power-losing bling quota for the foreseeable future.

 

there have been other dynos that show Cosworth doesn't perform on NA... its not just a myth that people guess about... I remember reading Jonnylaw's and at least one or two others (on my350Z I think)...

 

^Like I previously mentioned above. I have seen the test by Jonnylaw but there were certain things that bothered me.

There aren't many test of the Cosworth on NA and it's definitely not a unanimous concensus that it is bad. I'm sure you remember the Castrol Challenge where Cosworth decided to use their plenum on an NA car. On a more recent page, I can remember one performed by Z1motorsports which turned out to be quite successful. The other one I can remember is of ___jb's car which also turned out to be quite good. Injected also had a test a while ago that showed the Cosworth to be quite comparable to a spacer. I'm not trying to prove a point but if you did spend time researching it as if you were to buy one, you'd come up with the same dilemma as me, which is that it's not clean cut. All I'm doing is adding my test to the few data points that are out there.

 

^^^ I read a bunch about the Cos plenum way back when it came out (and even prior to its availability...

Its my understanding the the intake runners are designed for much higher velocity that NA typically produces...

I'm not bashing your attempts... it's just a pricey "test" just to confirm a pretty common understanding.

 

No offense taken. I didn't originally buy it for the sole intent of testing it. I was really hoping for it to perform as well as it did when Cosworth themselves used it on their NA engine in their engine build off. If anything my car should, at the minimum, flow as much as their 3.8L stroked engine. If you go to their US site, you will notice that the Plenum dynos all revolves around NA application for a mildly built NA car.

 

if it's the same info I read a while back - iirc the impressive gains were extremely high rpm - bellow that it wasn't worth half the price... you may be referring to a different article, but I did read their test info...

*Edit... this isnt the info I read in the past - but still states the same info... it shows their own dyno data:

http://www.cosworthusa.com/store/pc/...0&idproduct=89

there has been much of the same around different forums...

Anyway - it looks nice and a lot of people are more in it for looks that performance anyway so for that reason it suites some NA people... otherwise the only decent gains I've seen are FI.