It doesn't really surprise me that I lost power. When I first installed my breather mods in four phases (all in one session though), I lost power at every single phase, but I really didn't expect to lose this much thouugh. The temps difference from the previous run is ~20+F from mid 70s, so that might have played a big role.

Yeah I noticed that as well but I am wondering if it is because they only or mainly use domestic parts. I really rarely see japanese modded cars with foreign parts.

 

Due to the low numbers I got from the cosworth, it prompted me to do some review of the material I previously downloaded off of their site. I never really physically overlaid them, other then just eyeballing the graphs, which I thought was good enough. Taking a second look today I noticed something strange so I quickly photoshopped the three dyno runs Cosworth had and of course the scales on some runs were not the same as others so I had to do some manipulation hence the blurriness. This more or less explains some of the huge loss I got. Take a look.

 

I had posted about this a while ago somewhere. The cosworth kind of emulates the revup lower as far as power delivery on a stock or small cam car. But the revup lower nosedives over 7k and the cosworth apparently just keeps going or so they say, waiting on adam's testing...This testing was done with run of the mill shorties going into open atmosphere pretty much so equivalency to road going cars isn't perfect. Just pondering I am still a backyard tard.

 

Hey Gabe, dont know if you know or not, you actually can find those dyno charts on www.motoiq.com aka beyond-the-dyno by Eric Hsu. That was on a stock bottom end vq35 with Cosworth heads, cams, plenum and DC headers(ugh!!!) Also dynoed on an engine dyno, so that motor would dyno about 310-320WHP...

Those are impressive #s either way without touching the bottem end. Its sometime I might consider for my car. Im still gonna wait for your results and see what you like and dislike...

 

You are right that the behavior of the cosworth is very similar to the revup when comparing it to the non revup plenum. I as well am still waiting for adams results. Those ZK2 cams are more likely on the larger side then small. Keeping my fingers crossed for some positive results with my build, hopefully rebello has a nonrev laying around.

Yeah, I also went to motoiq but I am not sure why Eric didn't make a graph similar to the one i made. It would have made my life easier. I also read that he ran them on some aftermarket headers but wasn't sure if it was the DC. On some of the pics of the engine on the dyno, the headers seems to be some custom longpipes. No doubt that the peak numbers are much better but I really didn't realize that the losses on the low-mid were like this. Hopefully after the tune it will shed some better understanding on what to expect.

 

When you say, you hope Rebello has a nonrev collector laying around, are you not going with the Cosworth any more? Or just doimg more testing. You will definately gain most, if not more, low end power back just because of the stroker kit.

Eric's Cosworth build pretty sure lost low end because the headers exited right into a fume collector. To me its just like running open headers...

What is Adam doing that you are waiting for? I thought he installed ITBs, or did he get rid of them? Gotta update myself in his thread....

 

I guess its been awhile since I read Adams thread, last thing I remember was his Racepak cluster having issues. I also knew he went ITBs but didint realized he had such much problems that he trashed them. I'm just read his blog on his 4.3gears and quaife lsd... Go Adam and good luck.

As for the Cosworth plenum, I think things should be fine in your case Gabe. After all you will be increasing the disp and I think bigger cams as well

 

Hi Gabe,

Did you see the NA MREV2/spacer Vs Cosworth dyno comparison by Johnnylaw? ( Dynos on page three.)
http://g35driver.com/forums/intake-exhaust/201673-cosworth-plenum-installed-pics.html


The Cosworth basically lost significant power and MPG.

 

Hasn't anyone figured out if you want your cake and eat it to that single stage intake manifolds just won't do it. As far as the loss of power with cosworth, I don't believe the dyno results of any substantial intake or exhaust modifications on these cars can be evaluated without a complete custom tune due to the sensitivity and lack of correction by the engine management.

 

I don't think it has anything to do with single, dual or quadruple intakes. It just comes down to flow resistance, resonance amplitude and Q.

If you follow Jonnylaws links, you will find he did retune it but even then it still didn't perform as well.

If you put a Cosworth plenum on your car and did a full retune, my guess is, you would probably see similar losses.

As far as I know from the dynos posted so far, about the only situation where the Cosworth will do better is on very high boost turbo Z's.

 

This really should not be hard for anyone to understand - it's been posted many, many times. The Cosworth rewards rpm and rewards those with cams, which is where the stock plenum (with or without a spacer) just runs out of steam. The G35 referenced on driver has no cams, no built bottom end (thus can't rev). Why he thought he would see a net gain from a plenum that is designed with those 2 things primarily in mind is beyond me. He also "lost" mpg when he installed it without retuning. Of course mpg is going to suffer. He goes on to say as soon as he uploaded the Osirus flash, the mpg came back. MPG is totally tune related and driver related.

 

I havn't seen any dynos of the Cosworth with such an engine build. Are they posted?

 

Hi Tony, thanks for the link. I saw this as well but didn't think much of it since it shows the car at a state where the tune was not meant for it which is the same state of my car as of now, however my losses are three folds more. Talked to Zcar this morning and he'll tune my car this Friday. Hopefully the cosworth does something.

Man, if i only get 16hp/14tq with the stroker kit I would seriously just run my car into the wall...no joke.

 

Hey Gabe, I say is time to submit to the power of FI, lol.

 

Do you have any thoughts on why it was three fold more than Jonnylaws losses?

I wonder if there could have been any runner design changes since Jonnylaw did his test.

 

Man, if i only get 16hp/14tq with the stroker kit I would seriously just run my car into the wall...no joke.[/QUOTE]

That's funny...you know what I meant. The stroker kit will make up for it. I talked to Adam yesterday in regards of the "supposed" off-the-shelf 3.8L stroker kit that Cosworth has, but he stated he didn't have any info on it and was pretty much for professional race teams I wanted one!!!

Anyway, I guess a stroker kit won't be in my plans for my build

 

You know, it's hard to say but i think it's related to.....................my exhaust and not having that new MD TP! Of course I'm kidding. There are two variables that vastly differed from my previous dyno to this one. First one being that my car's AFR was tuned for around 12 and now my car is running much leaner at 13.2-13.5. Second the temperature is higher by more then 20F. Anything other then these two variables would be speculation at this point, but as a note though, my car does have cams and headers where as JonnyLaw's doesn't.

There were some changes in the cosworth's runners. Judging by the date of JonnyLaw's thread, he may have the older one. Here is a link that visually illustrates the mentioned changes.

http://cosworthusa.com/store/pc/view...2&idproduct=89

That's funny...you know what I meant. The stroker kit will make up for it. I talked to Adam yesterday in regards of the "supposed" off-the-shelf 3.8L stroker kit that Cosworth has, but he stated he didn't have any info on it and was pretty much for professional race teams I wanted one!!!

Anyway, I guess a stroker kit won't be in my plans for my build [/QUOTE]

You were set on getting only the cosworth and nothing else? Is there something special about that kit?

 

I wasn't set on the Cosworth kit per se. But it was on the top of my list. The kit didn't require the removal of the oil squirters, minimal block notching for the rods, even kept the factory baffle plate. There wasn't any info on it, just wanted to know the specs. The Topshop Challenge required the shops to use parts any average "joe" could buy, Adam didn't have any info and. Cosworth has not responded to my emails or phone calls.

Cosworth doesnt skip out on things so I figured that would make a great powerplant for my car Well, I may just stick with a 3.5, maybe alittle bored over for a 3.6-3.7L. Nothing too extravagante...not looking to push the limits of NA. Looking for around 300whp and hopefully 275+wtq...

 

13.2 to 13.5 should be right in the sweet spot of this engine so at least that much moved in the right direction.

However, the 20F increase in ambient temperature trashes the confidence of any comparative results because a lot of timing is pulled out at increased temperatures.

A good retune where you can reoptimize the timing will tell you real quick what the true results are.

 

I thought 13.2-13.5 was the sweet spot for the NA VQ, but after multiple different tries with various settings it was found that 12 yielded the best performance (prior to my cam/header install my tune was around 13 with the best gains). It's sad to say but I think my car has been on the dyno more then I have spent time with it.

Yeah, I'm hoping to see something good come out on Friday before the engine is taken out and sent away.