lost 20 whp.. what could have been the problem?
 

I just recently added JWTs7r's and motordyne mrev2 and my car lost 20whp!
What could have been the problem?

I have a 2005 35th anniversary ed.. Previously I dynoed at 276whp with this mods
ARC intake, tomei V1 headers, test pipes, HKS hi-power, HKS twinspark, unorthodox pulleys, skunk2 plenum lift and COBB race tuner program.

I also change my final drive to 3.9, does this affect my dyno numbers?
Just today I brought my car to a shop for tuning, since I just added the mrev2 and JWT s7r at baseline the we got 255whp after some tuning we only reach 263whp on dynojet. What could be the reason? :confused:

Well, what dyno did you get your previous numbers on?

Same dyno machine.

Are these corrected or uncorrected numbers? What was the difference in weather between the days since you used the same dyno?

Post your before and after dyno sheets with your A/F maybe a tuner on here can tell you what the issue may be.

How does the car sound with the new cams?

thats the funny thing about this game, some times 1+1 doesnt always equal 2...

looking at the cam profile, it could be that you dont have the right suppoting mods to run that cam. There is a lot more to choosing a cam other than just the duration and max lift. You have to take into account that because of the larger lift and longer duration and no intake/plenum tuning that the speed at which air enters your motor has actually decresed, there is a good possiblity that you are getting LESS air in, thus less air out, all combined for less HP in the end...

You need a spacer
 

You need to install the plenum spacer, too.

I've seen this happen with alarming frequency, where people install the MREV2 on their Rev-Up but don't install the spacer to go along with it. This is straight from Motordyne's website:

http://www.motordyneengineering.com/...page_large.jpg

So you can see above that without the spacer, you actually see a shift in the powerband to the midrange that results in a drop in top-end power. This is normal. You recover that and gain some more by adding the spacer to the setup.

Additionally, this is in the Motordyne FAQ:

"Will the spacer work on my 2005 35th Anniversary model 350Z (with Rev-up engine).
No. The spacer by itself doesn't do anything on the stock REVUP lower collector. It must be used with the MREV2. When used together, it makes the most effective bolt-on short of nitrous or turbo. A minimum 15HP and 18TQ. Many independent tests have dynod in excess of 20HP and 30 TQ. If you can only do one or the other, do the MREV2 first. It will make substantial upper midrange gains. You can always add the spacer later for additional power at high RPM ."

///

So, assuming you haven't done this already - which it appears you haven't - drop the cash and pick it up. You'll be happy you did. However, start looking to get your car re-tuned, as you will probably be running a bit lean - I know I was at that point.

And on one last note... I always add a fudge factor of 5whp or more even on the same dyno when considering the numbers and their importance, as conditions do change; those things can have a lot of variance. Between the two aforementioned elements, your problem should be solved.

So did you retune it after doing the cams and what not? Gearing would affect the numbers slightly but not 20whp.

The number were 1st 250+ and tuned it upto 260+ I dont have a copy of the dyno numbers. The weather is constantly hot here in Manila. Does anyone in this forum have an actual experience with JWT s7r on N/A built?

I will try to remove the Mrev2 and put the stock manifold back with the skunk2 plenum spacers and see what happens. I hoping to see more gain.

Already have the plenum spacers they were from skunk2.

Last year we did the dyno on the same dynojet and got 276whp. Using the same map we only reach 250+ with the mrev2 and JWTs7r, after some tuning we only reached 263whp. Its just that i'm quite disappointed since I was hoping to gain more than my dyno last year which was 276whp, but i got less power after installing the jwt s7r and mrev2. Is it possible the jwt s7r is only for turbo application and not for N/A. does anyone have the s7r on an N/A build and got gains from it?

I dunno man, but it seems like it could be a tuning or mechanical issue such as cams not advancing correctly or knock retard. Why you using COBB which is dead and unsupported?

Do you even have cam control and logging with COBB? I can't imagine aggressive cams would be happy with the stock cam advance profile.

Secondly I would do performance logging to check your actual timing during pulls and make sure your noisy cams aren't triggering knock retard.

At least with Uprev you can disable knock control temporarily and log actual timing to see if it's causing issues.

May be the one time im glad i went FI.. swings between 450-500 whp arent going to bother me not one little bit as long as things arent breaking.... Ill gladly take any power it decides to give me. lol.

Is anybody here have the same cams as i do? JWT s7r?

seems he has upgraded intake and exhuast, the cams arnt insane so he should be good there. only thing i could think of is knock retard like someone said(doubtful i would expect alot more power lost from that.), not spinning it high enough(again doubtful since the cams arnt crazy but who knows without a dyno) orrrrr my bet is that the different cams are changing the dynamic compression ratio of the engine lowering it and netting less power which combined with the rear gear change is compounding the loss you see op. if this is the case more spark advance should be able to be added without det and gain more of that back, im unfamilar with how the cobb works though for tuning and how much you can change it?

i would call JWT and ask. But it does sound like a tuning issue.

I got the race tuner beta from cobb.

I already did but i have not heard from them yet. I also sent the maps that were used and the software from COBB.

is it possible that the mrev2 restricts the air intake flow thus creating less power?

Not in the slightest, it's honed out compared to a normal lower plenum.

You got new cams, that's going to be where you need to look, that's a major change, no matter how slight the profile change.