Hi all,
I have a problem that I can't figure out & I'm hoping someone here can help me solve this.

I have a 99 maxima QX (euro), manual tranny with a MEVI. After getting a ypipe & a whole new exhaust dyno showed 223hp & 283NM (torque).
here is the dyno: http://i60.photobucket.com/albums/h7...ka/wykres2.jpg
(please disregard the 1st runs on all dyno results)

Then I got rid of the MEVI & replaced it with one from DEK (UIM, LIM & injectors from the DEK), also I put in a Pathfinder TB and a Walbro pump. Everything was tuned and it dynoed at 237 hp & 297NM.

here is the dyno: http://i60.photobucket.com/albums/h7...ka/wykres3.jpg

Then came time for the CAMS, I got the 3.5 cams put in and they were advanced 2 degrees (per the info from here that I read)......and that's where all the good stuff ended. The power dropped. I dynoed it again & it showed 231hp & 272NM.

here is the last dyno: http://i60.photobucket.com/albums/h7...mka/wkres4.jpg

Any ideas what might have happened & why the power dropped? I was expecting gains from the CAMS.

Thanks!

 

Looks like you used a different dyno.

Should use the same one, also how does the car feel?

 

+1

Using the same dyno when doing comparisons is very important. If you use a different one you'll be scratching your head wondering why the results arent what you thought they should be.

 

What are you tuning on? Normally for cams you have to adjust fuel AND ignition timing. How does the curve look, because with bigger cams, power should be building even past the stock rev limit, it's possible that you're not taking advantage of the larger cam profile.

 

It's hard to feel a loss or a gain of 5 or 6hp when you're well over 200hp but I'm not feeling anything near as I thought I would after the CAMS swap. Should they maybe be advanced differently? I know it should be ran on the same dyno but I can really feel the loss of torque on the car after the CAMS were swapped.

The thing that worries me is not the loss of hp but the loss of torque. The car lost 30NM in the lower and mid range rpms. It does look better in the 5200rpms range even though I lost torque, it is pretty stable now between 5200-6000rpms at about 250NM. fuel & air was tuned, the only thing that hasn't been touched yet is the ignition timing & the rev limiter.
After the CAMS swap, the pressure on the cylinders dropped. Before it was 12,2-12,5 bars and now it is 10,5 bars.

EDIT:
Adapters used were 3,1mm; exhaust cams without change & intake cams advanced by 2 degrees (maybe that's where the problem is?)

The cams are from an 03 maxima:
Engine: VQ35DE (2)
Model Years: 2002-2005 (Maxima, and a slew of others)
CVTC: Intake

Intake__Lift: 9.5mm
Exhaust_Lift: 9.5mm

Intake__Duration: 238ş
Exhaust_Duration: 240ş

Intake_Opens: 6ş ATDC
Intake_Closes: 64ş ABDC

Exhaust_Opens: 52ş BBDC
Exhaust_Closes: 8ş ATDC

Overlap: 2ş

could it be that my ignition timing is not tuned???

 

It's probably due to the tune. Even with the JWT S1 cams (256*) people wouldn't see big power increase without optimizing the software. And you can't compare numbers between dynos.

 

What AFR are you at?

Also what are you using to tune?

 

up to 5500rpm - 12,8
from there to redline - 12,5

it was tuned with ECU Master (it's popular here in Europe)

 

when you play with cam timing you are also shifting the powerband which is the reason you lose some tq down low. You can get some back by playing with the inj timing

btw did you extend the rev limiter any after the cams and any chance you can visit the same dyno and run again

 

I would add some timing, does your tuner detect knock?

 

There is no knock detected.
The rev limiter has not been touched yet.

At this time, I am having software written by a tuner to have the ability to advance the ignition timing.

I will try to get the car dynoed at the same place but for now I can feel the loss in torque & I know that dyno will just prove that to me.

Why do you guys think that after the cams swap from a 3.5, I have loss of pressure on the cylinders & loss of torque?

Do you guys think that this whole power loss could also be due to the fact that ignition timing hasn't been touched?

putting the cams from VQ35 I knew that I would not get the same results in the upper range as from JWT S1 but I was hoping to keep most of the lower & mid range power that I had on stock cams & that they would lightly improve in the upper range.

I'm leaving the rev limiter for later, after I get the lower & mid range torque back.

 

If you would have the cam timing alone you would have gotten excatly what you thought

But with the cam timing altered the car is geared more towords topend

 

To really see gains you'll need to raise the limiter to atleast 6800 and play with the inj timing

btw, what software are you using to tune the ecu

 

the rev limiter will get raised as soon as i get my top end torque back. not sure if I'm understanding this correctly but changing the CAMS, it should give me more torque & not less. I lost a bit on top & a lot in the lower & mid range. Should I have not advanced the cams by 2 degrees? Is there any proven info regarding gains in power after changing cams to ones from a stock 3.5?

 

Some of this has already been said but I'll echo it.

- You have to use the same dyno when trying to compare before/after numbers.

- Any time you increase lift and duration (assuming no variable cam capability) your power band will move to the right. This means some low/mid torque loss and high end gain, however you may need to extend the rev limit to see the full effect. Another effect of increasing lift and duration is that your dynamic compression will usually decrease (ie cylinder pressure drop) unless you compensate by increasing compression ratio (ie higher compression pistons).

- Any time you make a major modification like a cam swap you WILL need to adjust fuel and ignition timing to optimize the setup. The latter (ignition timing) will influence the results far more than AFR will.

I'd do what's already been suggested, find a way to tune both fuel and ignition timing, and re-dyno on the first dyno you used before installing the cams. I really can't say what kind of gain the stock 3.5 cams should have, I'm not sure I've really seen dyno's of them but then again I've barely been on this site in the last 2 years. I'd shoot for an AFR of 12.8 to 13.0 across the board and your ignition timing can likely get up into the 32-36 deg range. But each car's different so a proper dyno tune is key.