Sr20det gt2560r (s15 t28) Running lean

[jroy1234]

Ok i am not one to post before researching ( i already have) but i want to get some feedback on here.

I installed the gt2560r today and the car is running quite lean. I have a enthalpy tuned ecu(used).

My set up:
-550cc injec
-z32 maf ( wiring specialties harness, so it has the PnP connector)
-255 wali
-aremotive fpr (set at 43psi with vacuum off and 37psi with)
-aem wideband

Here is what i found out:
maf
exhaust leak
Vacuum leak

All the hoses on the motor are new, i did the swap at work (Nissan) and replaced everything down to those BS OEM 1990 OEM clamps.

My biggest red flag is that the manifold has a slight leak that will be welded friday, but i read the the stock ecu doesnt use the o2 readings at idle just maf and coolant temp sensor.

When I start it. at idle, it runs perfect at start up (warm) then peaks and fluctuates with perfect afr's but then as soon as the idle drops after peaking afr's go straight to >17-18. and under boost the best i got was 15. the SR has never had any fluctuation problems. ever.

I adjusted the fuel pressure up and the fluctuations grow faster (900-1300) with no change in the afr's.

The car was running a bit rich (12-13.5, sometimes @ 11 under no boost cruising) with the stock t25 with the same mods and tune, but never had a lean problem. I also never had the ground connected on the MAF and it still functioned perfectly.

Right now i have the MAF ground connected, set factory fuel pressure, and leak tested any vacuum leaks. My biggest red flag is that manifold leak.

Let me know what yall think.

[cotbu]

but i read the the stock ecu doesnt use the o2 readings at idle just maf and coolant temp sensor.

Not true, it's temp based! when you reach operating temperature and idle is trying to stabilize the ecu does use the o2 sensor. usually around 78-80c
With that being said, I see a problem with the tune. As being not perfect for your setup.
But let's say it's not the tune, you have vacuum/boost leaks that need to be repaired.
Is the z32 mafs and OEM unit. What brand are the 550cc injectors, and have you checked them for leaking pintle or orings?
Have you verified ignition timing?

The fluctuation up and down, can be a vacuum leak, CTS, poor tune, IACV coolant line missing, of course there's more, but you have to start somewhere.

Iv'e seen people mask problems like this, by raising the idle. I recommend finding and fixing the cause.

[marks14]

I would defiantly fix that vacuum leak before ripping your hair out. You can also send Martin at RS Enthalpy a e-mail, his customer service is top notch.

[jroy1234]

See if i lower the idle the, the fluctuation stops, yet it still reads lean.

Used z32 i got from a tech at work (working fine before turbo swap), Sti 550 injectors, leak tested before i installed them

Ive checked all the leaks with a leak down test and smoke tester. I'll weld up that manifold crack today and see how it behaves

[Shayl]

You can't use any of your information until you stop those leaks.

All the leaks you mentioned are introducing unmetered extra air which would explain your lean ratios.

Fix the leaks and test again

[cotbu]

It's probably the coolant temps sensor, if temps in TX are anything like DE's today? I've seen a few cars with the fluxing idle today and after I manually controlled the coolant temp sensor they enriched and idle correctly. CTS was not faulty! Just cold!

[jroy1234]

well yesturday i fixed the pinhole in the manifold, and the afrs are better, but not perfect. I discovered the exhaust manifold gasket is leaking so i got me a new one and im installing it today after work.

all in all im leaning towards the exhaust leak causing the issue because after fixing the pinhole leak its been running a bit better. I also turned up the fuel pressure to be safe when im running with the leak not to lean out.

the idle still fluctuates, but less after i welded the manifold.

ill keep you guys posted.

[jr_ss]

Do you have a tune for a T25 yet you are running an S15 T28? If that is the case obviously you are going to be running lean...

What exactly is your tune for? You stated it was a used ECU, so I'm assuming you bought it from someone and slapped parts together to meet that "tune".

[roadbuster]

In my experience, when I had an exhaust leak up stream of the o2 sensor, my AFR's read pretty lean.

The worse the leak, the worse the AFR's...this was on an SR20DET with t3/t4 turbo & 3" vband that was leaking at the turbine exit.

[e5s4y]

Originally Posted by jr_ss

Do you have a tune for a T25 yet you are running an S15 T28? If that is the case obviously you are going to be running lean...

What exactly is your tune for? You stated it was a used ECU, so I'm assuming you bought it from someone and slapped parts together to meet that "tune".

oem redtop ecu w/s15 t28 at .9 bar. Im sure my injectors arent too happy, but still running pretty much perfect afrs

[jroy1234]

Originally Posted by jr_ss

Do you have a tune for a T25 yet you are running an S15 T28? If that is the case obviously you are going to be running lean...

What exactly is your tune for? You stated it was a used ECU, so I'm assuming you bought it from someone and slapped parts together to meet that "tune".

its tuned for a t28 550s and a 300zx maf.

I got most of the issues somewhat figured out, i isntalled a new manifold gasket and the leak went away so it fixed the afrs better under boost but sill runs a bit lean on idle.

Im going to hook up the EPROM and read the maps that are on it, but i have an event this sunday so im strapped for both cash and time.

Today, however, i did hear a bit of an exhaust leak again, so my biggest fear is that my manifold might be warped. im gonna run a smoke test and see if it is. im going to double check leaks again on the intake side, soo ill let you guys know

JC