yea... the Greddy sp2, cats, and retune could very well yield that 14hp so where the Cosworth fits in is unknown.

Just got the Cosworth installed. Sharif and the guys stayed three hours late to get it all finished, So thank you again Forged Performance! I will post the results tomorrow and some pictures of the engine bay. I was very impressed with the results. Sharif can explain them a bit if he wants to chime in :-)

BINGO! ;) The cats and reflash alone are good for this kind of gain so it's pretty safe to say that the Cosworth manifold virtually gained nothing. That's not unexpected as from what we saw from other dynos incl. A/F ratios, the Cosworth plenum outruns the stock plenum only at very high rpm (which again requires different cams to make power) or on f/i applications where CFMs are obviously much higher.

It becomes obviously that the stock plenum design flows enough air without becoming a bottle neck for bolt-on moded n/a cars. Plenum spacers etc change the resonance frequency and air distribution and can make some gains out of this, but the Cosworth manifold is built for different purposes.

the velocity stacks dont shine till more CFMs are pushed.

Like the consensus around here leans on, performance wise, its probably the best plenum mod if you are FI, and looks very nice.

What were the results? Do you have before and after dyno charts?:confused:

i agree im starting on a n/a build this summer step by step... by myself... no dropping a blank check off at forged (though i will be going there for tuning and any other helpi would need from sharif) but Tac-m said it best... "i believe the VQ has a lot to offer without f.i."... and i agree whole heartedly... honestly i could have her boosted before the year is over... but i'd rather go n/a for some reason... who knows plenty of people said they wouldn't go f.i. and look at them lol but to say modding a z n/a style is a waste is falls heavily into bullshiet's yard... at the end of the day if you f.i. guys cant drive worth a shiet... whats the point lol

What are your goals HP wise?

To do a complete N/A build you are looking at building a motor with similar efforts to what is needed for boost. Except you run no boost.

I am sorry, but there is a reason that the number of n/a builds is limited to a very small few.... it isn't worth it. I don't think it's sitting in 'bullshiet's yard' It is falling into the realm of logical thinking. People want to get some hp for their time and money.

Even with a bad driver, a boosted Z can be fun.

"worth it" is totally determined by the person footing the bill. To me, building an FI car wasn't worth it, since I already have a hp high FI car. I wanted something different, and that's what I chose to build

like i've said time and time again... i want to get as close 300rwhp as i can n/a... any dipstick with rich parents or a lot of money can drop off a check at a local tuner shop and say "make it fast" ive seen plenty of guys just in MY area spend thousands and thousands of dollars just to blow their engine in less than a year... to me ... thats not worth it... people want different things form their projects.. me i want a quick a$$ z that can carve corners and outperform f/i z's on the track... with a little research.... time money... and racing training i feel its more than possible...

FI is awesome stuff, but I have to totally agree here.

You do not need FI at the road course to smoke 98% of all the other various cars at the track (including FI).

This of course does not apply to street driving. Street driving is much less about maintaining speed through corners and is much more about the fun factor of high acceleration rates.

FI does also greatly increase engine stress and the likelyhood of engine failure. The pros/cons of this is subjective. If you have the $$$ and time for a lot more engine maintainence, its not a big deal.

Nice to see more NA people coming out of the closet. I'm in the process of putting together an NA motor and like the challenges, plus the fun of driving an NA car with a nice set of gears.

Be prepared for the NA haters on the forums... For some reason they can't just be happy with their cars, thay also like to downgrade anyone different.

Don't forget to post your build in the new NA forum!

church... well said sir :)

nyways, bak on subject,

Is Sharif correct that the new batch of cos plenums are machined better/different than past shipments?

cuz i doubt it...

We still haven't seen the results... :confused:

I am particularly interested to see if you picked up torque accross the entire RPM band and, if so, how much? Or did you loose torque in the mid RPM ranges and only pick up top end power?

I am thinking about putting the Cosworth plenum on my G35, but only if I will not lose mid-band torque and the gains at the high RPMs are worth the $1100 price (+ the cost of the spacer to clear my fuel system and injectors if the 5/16" Motordyne isn't adequate/compatible).

My setup is being built by Japtrix using an Import Parts Pro short block, as follows:

Eagle rods
Ceramic coated 8.8:1 Wiseco pistons
ARP rod, main and head studs
Greddy 18G TT kit and Intercooler
JWT C2 cams and springs
Ferrea valves - stock sizes
Port matching/polishing on the head
RC eng. 750cc injectors
CJ Motorsports Stage 2 fuel system
Walbro 255lph in-tank F/P (may also add an external 255lph F/P, but only if fuel flow proves to be bottleneck using the single pump)
Koyo radiator (the big one)
Custom oil cooler
HKS F-CON V Pro, EVC, A/F Knock Amp, Navigator Pro, turbo timer type 1
Coolingmist meth/water injection system with Smart Injection and Vari Cool controllers, and two S-HSV valves (10 GPH each)
APS Dual 2.5" Can Back exhaust with 2.5" test pipes
Cluthmasters FX600 twin disk clutch
Driveshaft shop Level 2 axles


If anybody else can chime in on whether the Cosworth Plenum will provide significant improvement over the stock lower plenum and Motordyne 5/16" spacer on my setup (and is worth the price), I would greatly appreciate hearing your thoughts.


Also, as a side note, I need to throw out a BIG THANK YOU to Roger and Bala at Japtrix, Kyle at Import Parts Pro, and Dave at Coolingmist. All of these guys know their ****, and have given me a tremendous amount of guidence. If you want GREAT customer service, these are the guys to deal with!!!!!!!!!!!!

there are numerous dynos in the FI forum posted. The problem is of course, actually getting your hands on one.

I have performed many searches, but I have not found any dyno charts that compare the Cosworth Plenum to a stock (non Rev-up) plenum with a Motordyne 5/16" spacer. :confused:

The closest that I have found is the comparison of the Cosworth Plenum to the Crawford Plenum on Philthy's Car:

https://my350z.com/forum/shop-builds/330588-forged-performance-cosworth-plenum-test-on-philthy-s-car.html

If anyone has any dyno comparisons between Cosworth Plenum and the stock (non Rev-up) plenum with a Motordyne 5/16" spacer, or knows where they can be found, please advise...

Jonnylaw did a good write up and comparative dyno of the Cosworth against the MREV2 and 5/16" spacer a little while ago and posted the results here and on G35driver.

http://g35driver.com/forums/showthread.php?t=201673

This thread is a little lengthy but it has just about everything you could want to know about the subject. I believe the dyno plots are on page three or four of the thread.

Thank you, Hydrazine!

It looks like the MREV2 with the 5/15" spacer is the way to go for N/A. It provides more torque than the Cosworth all the way to 6500 RPM, at which point the Cosworth just inches by.

I wonder if these results directly translate for a FI application, say around 20 psi? (with water/meth injection, of course, to keep predetonation at bay). If so, I've got the right setup going in.

After spending a few more hours searching the forum, I finally found the dyno graph I was looking for! :icon38:

https://my350z.com/forum/forced-induction/320934-injected-performance-cosworth-inlet-manifold-review-8.html

imo, based on price and perfornace, the 5/16" motordyne plenum spacer is the way to go. With the Cosworth Plenum, the torque loss throughout the mid-band does not seem to be worth the gain achieved above 5300 RPM, and that's before considering the significant price difference.

OK, well, forty minutes, but it seemed like a few hours... :icon14: