Hey, I posted this in teh dyno discussion but figured i'd post it here too since not alot of people visit the dyno forums, anyways heres teh graph...

1995 Maxima SE 5SPD



Mods:

-Hacked Air Box
-P&P Intake Manifolds
-Warpspeed Y-pipe
-Gutted Cat
-Motostorm UDP
-New OEM Knock Sensor
-New Left Bank o2 Sensor

Something is really wrong with the AFR, I dont see why it would be that off with the mods listed, the fuel system is still intact/stock....

This is 95BLKMAX's dyno, im sure he'll chime in in a few.

 

Hey btw, this was a 4th gear pull, air temp in the shop was about 90*F

EDIT= After a long talk, E55AMG suggested it might be a vaccum leak on the intake manifold (I did reuse the old metal gaskets that go between the heads and LIM when I P&P'ed the IMs), and there was a vaccum leak sound for about 3 days after putting everything back together, but THE NOISE went away afterwards, the leak mght still excist however.

The low power (for the mods) doesn't concern me much. I'm more concerned of what may be causing my a/f to be VERY lean then VERY rich . Since I think that's the primary cause of my low power anyways. Any ideas are welcomed, thank you

 

He is running really rich after 4000 rpm, maybe he should get it tuned. Did he check if he has any codes? how many miles on the car? What size wheels?

 

He port and polished matched the intake manifolds

 

Thats pretty hard to do, the lower you can do, but the upper is almost impossiable.

 

The reason it's lean is because your at 2000 rpms, the WOT map doesnt start till about 3000-3500.

 

The lower IM is completely done, however the upper IM I just port-matched and polished what I could reach with the dremel, and the same on the side where the TB mounts (that's also ported slightly and polished as far back as the hole for the EGR, and the TB is port-matched). Oh yea, the IMs are port-matched to each other. The LIM, on the sides that face the heads were ONLY POLISHED, since I wasn't going ot touch the heads I saw no reason to port the LIM there. That would just have created disturbance in the airflow in all runners.

The car has 118,8xx miles

EDIT= I have Z32 TT wheels, the fronts are 16x7.5" and weigh 16.0 lbs (the rears are 16x8" but they dont matter to this) and I'm running BFG G-Force P225/50ZR-16s on them

 

Definately replace the gaskets, we dont have many gaskets that are reusable on the car and the IM is not one of them.

 

Do you have a crankcase breather filter?

 

ok that is true, but what about the other extreme? from 5k rpm til rev-limit it stays at 11.0-11.5:1, that is EXTREMELY rich for an N/A car :-(

 

no sir, runing the PCV (new) valve on the rear VC and the hose that goes to the resonator box from the front VC, no breather

 

Perfect.



The lean condition still should be related to unmetered air. Do you have any good pictures of your setup?

 

[img=http://img358.imageshack.us/img358/9559/myenginebay8aw.th.jpg]

That's the only recent pic I have of my engine bay

 

Everything looks fine. What exactly did you do to the airbox?

 

In the dyno forum, i'm quoting Kevlo911 with=
This might sound stupid, but how are his grounds? I dont like that dip in the power and it might be electrical. Fab up a homemade ground kit and see how the car feels. I know it wont make up for all the power but it might be something you wanna try.

That dip in power might just be electrical, my AC/Alt belt has been squeeking lately on launch with the AC on, I've just been too tired from work and school to tighten it (I checked and yes it is a little loose). I'm actually going to make a grounding kit with a cousin later this month, so we'll see.

 

OK, I removed the stock snorkle crap to the airbox, and I cut a triangular hole on the side that faces the driver-side fender.
EDIT= There, on his 1st picture in that page, that's what I did to my airbox
http://maxima.cardomain.com/ride/370660/7

 

That is part of it. The stock flow pattern across the MAF sensor has possibly been disrupted, this is a VERY common issue in 2k2s. I would still search for unmetered air leaks and give the ECU a little more time to adjust it's open loop settings. But even if you do find something wrong you will still need to tune that A/F via a piggyback.

 

Interesting? Would a aftermarket intake cause the same interference?

 

Perhaps. I know they do on 2k2s. Especially at 5200 rpm.


But don't get me wrong. I am not saying that IS the problem here, I am just saying that based on my experience I see it as a potential culprit.

 

Maybe porting the manifolds disrupted the airflow somewhat. Ideally each runner would have been flow-tested to make sure the airflow was laminar and consistant to all cylinders. This was a hack-job relatively speaking. Just a thought.

Edit: Just thought about something. The WOT maps only depend on 2 inputs, MAF voltage and engine speed (CPS-POS). Perhaps the MAF is reading X amount of air, but since the airflow might be turbulant AFTER the MAF, the airflow reading isn't accurate. Make sense?

 

You are going in generally the right direction but I kinda doubt that he removed enough material for that to make a difference. Having to port match a Nissan product is rare and even when it can be done there is little to do. And they usually don't flow test production parts. Perhaps one in every thousand or so may get inspected.

 

What i mean is it should have been flow-tested AFTER the porting ideally, that's all. Either way, it's an air metering issue.

Edit: Do you know if a bad rear 02/gutted catalytic well affect WOT air/fuel ratios in 4th gens?

 

As far as it being a hack job, yea it was. Did it as a lil project over a weekend. But it came out very even, and remember I made sure to port-match using the gaskets as reference. But I still feel that the big thing going on here is the a/f being so busted up.

I'm lucky enough to have a day off this Weds, so that day I'm going to replace those metal gaskets and I may go to Nissan for exoticcreations to do a diagnosis on it and to see if timing is being pulled/ all the sensors are in the right working parameters, etc...
Really appreciate the help people keep them coming, I wont mod again UNTIL the "problems" are fixed

 

To be exact, I'd lay the gaskets over the runners, look straight down onto it and use a Sharpie to mark how much metal was sticking passed the gasket. Like so (notice the edges of the runners how on some parts of each runner there is blue ink on them):

 

Update;
- As I removed the fuel rails I noticed two of the injector grommets (bet'n the injectors and the LIM) were crushed. I must have forced them in like an idiot when putting everything back together after the P&P. Got all 6 grommets brand new and made sure everything was seated correctly.
- Replaced the metal LIM-Heads gaskets
- Found something odd. The KS harness was completly disconnected from the KS, and the metal wire retainer was nowhere to be seen. s0ber as my witness, I DID put that retainer on correctly when we did my KS. So I cant explain how that happened. s0ber sugeested that we may have accidently tugged on the harness while moving around inside the engine bay when we did the clutch, which is possible. By guetto, yet effective means, the harness is permanently attached to the KS, so that wont be a problem anymore.

I did feel that there was less power at the bottom end, but i never suspected the KS was to blame, since its been 95 degrees plus here in Miami, I figured it was just the heat

Driving around;
What a difference. Launching from 2nd doesn't sputter the motor at all, it just goes. Powerband is much smoother and I FEEL harder pulling up top. The power increase wont be verified until the next dyno day at this same place. But by then I'd have a CAI, grounding kit, and possibly headers. I know I wont wait until after the next dyno day to install new mods

Thanks for all the help, I'll bring this thread back to life once I go back to the dyno

 

awesome man... looks like you;ve got your ride in check... i'll figure out when the next dyno day is... maybe some south fl. maximas can go out there and do some representation...

 

Good work, nothing like finally finding a mystery problem.

allen