V8 in a Miata , running lean need some tuning help

[rckrzy1]

Ok, pulled a LS1 5.3 from a 2004 silverado and installed in a 1994 Miata. Had to use an LS6 intake to clear hood and using supposedly 2002 Trans Am injectors . Car is throwing lean codes as both banks are maxed out at 25% adding fuel. I copied the injector PW etc from a 2002 hpt file and saw very little to no change. The car is simply not getting enough fuel. Regulator is a 54 or 58 PSI .

I'm not sure how to get the silverado ECU to give the car enough fuel, as in what table/s will get me more fuel to cylinders.

There does not seem to be any vacuum leaks or undocumented air.

[5FDP]

Tune the VE and MAF.

You changed the intake and injectors and that's making a huge difference in airflow/fuel into the motor over the much larger truck intake with smaller fuel injectors. There is no magic table you can just add fuel to, to get rid of the lean codes. You'll have to re-work the entire airflow model.

[rckrzy1]

Tune the VE and MAF.

You changed the intake and injectors and that's making a huge difference in airflow/fuel into the motor over the much larger truck intake with smaller fuel injectors. There is no magic table you can just add fuel to, to get rid of the lean codes. You'll have to re-work the entire airflow model.

So play with VE and MAF tables ?

[5FDP]

Yes, you'll want to tune the VE and the MAF separate from each other. You can pick either one to tune first, I normally put the vehicle into speed density and tune the VE first then switch over the MAF tuning.

Create a AFR error or EQ ratio error graph with a wideband or you can try using fuel trims and slowly correct the 2 tables.

[rckrzy1]

Yes, you'll want to tune the VE and the MAF separate from each other. You can pick either one to tune first, I normally put the vehicle into speed density and tune the VE first then switch over the MAF tuning.

Create a AFR error or EQ ratio error graph with a wideband or you can try using fuel trims and slowly correct the 2 tables.

OK, I had to go 33% as in VE and MAF x 1.33 to stop the lean , it now is at LTB1 21.9 and LTB2 8.6 , there is a small exhaust leak on B1 so I assume that is the diff there. But do you think having to go say 40% more fuel for a LS1-LS6 intake and injector change make sense ? Seems like a lot of change for just changing intakes on same motor.

I don't have a wide band and don't feel comfortable telling my friend to buy one to tune when I've never done that type of tuning. Just trying to get it in the ballpark and not be running lean, which now it is atleast in range and not throwing lean codes.

And ANOTHER issue, the tire size diff between silverado and miata is TOO great to compensate, maxed out the Trans/Rev per mile 3,840 and still off by 6mph . So I assume I will have tweak the shift points being this is an AUTO.

[5FDP]

I would not just start adding fuel like that, you will doing so blindly and you risk maxing out your fuel injectors quickly.

You/he must buy a wideband, using o2 sensor readings and fuel trims are never a 100% accurate way of knowing what fueling is really like. I would say that learning how to do this type of tuning is going to be a must or take it to a shop so they can tune it correctly.


Post a log and the tune. You may have other issues if you already added 33% more fuel and it's still showing lean on the fuel trims.

[Earwax]

Make sure there is no vacuum leaks.
They can leak under the manifold where it is hard to find.
Fix any exhaust leaks before the O2 sensors.
As stated above,
I don`t think adding more fuel is the answer.

[rckrzy1]

I would not just start adding fuel like that, you will doing so blindly and you risk maxing out your fuel injectors quickly.

You/he must buy a wideband, using o2 sensor readings and fuel trims are never a 100% accurate way of knowing what fueling is really like. I would say that learning how to do this type of tuning is going to be a must or take it to a shop so they can tune it correctly.


Post a log and the tune. You may have other issues if you already added 33% more fuel and it's still showing lean on the fuel trims.

with 33% it's just staying OK, as in LTB1 is 19% , at 25% it throws the lean code. So atleast it's better now than before.

[5FDP]

Though like I said, narrow band o2 sensors aren't always right.

Smoke test the entire motor to be 100% sure you have no vacuum leaks.

[rckrzy1]

Though like I said, narrow band o2 sensors aren't always right.

Smoke test the entire motor to be 100% sure you have no vacuum leaks.

Ok, have wide band installed. Currently running 13.0 AFR at WOT . Have MAF set at 30% more and VE at 25% more. LT trims about 3-5% positive. Seems pretty close.

He got one got P0101 MAF out of range. But since LT trims are close I'm affraid to back that down.

SO just to help me understand, my thinking has been that MAF is not used at WOT ? And the VE is the main adjustments for WOT.

[5FDP]

The other way around. Factory it uses dynamic airflow (both VE and MAF) up to 4,000rpm and then switches over to a mainly MAF only calibration for higher RPM/airflow values.


Now that you have a wideband I'd stop using the trims and correct the tune with the wideband only to really dial the tables. Choose either the VE or the MAF first, disabled all fuel trim functions and closed loop, disable DFCO and COT and tune using an AFR error or lambda error to help dial in the airflow tables.