Hi Guys,

I am now tuning my engine in car.

The baseline BIN is from the engine dyno session.

ECM : 7730.
BIN : AUJP.
Size : 420.
Cam : TPIS ZZ-X (Duation 241 @ 0.050", Lift = ~ 0.59").
Heads : AFR 220 SBC Eliminator with high flow porting option.
CR=11:1.
Intake : MiniRamII.
Cat Cons : Dual Random Technology 3" in/out high flow bullet type.
Exhaust : True 3" Dual with X pipe.

Based on priminary drive tests, the engine runs rich without closed loop correction. The BLM from 30 kPa to 80 KpA and an RPM from 400 to 3200 is 108. This is the idle / part throttle load range. About a 16% fueling correction.

Idle Map : ~ 64 kPA @ 900 RPM.

Barometric Pressure : ~ 99.3 kPA.

Barometric_Pressure = MAP + Vacuum

Vacuum = 35.3 kPa.

Vaccum = 10.42" Hg.

Gauge measured Intake Vacuum = ~ 10.25" Hg.

The MAP sensor appears to be ok.

On the engine dyno, I think the Intake vacuum was 12" Hg. Unrestricted.

My assumption is pumping loss that is the result of Exhaust pressure will lower the Intake vacuum. I am looking for a 1.75" Hg difference between the engine dyno session and my in-car measurements.

1 PSI = 2.041768” Hg

A 1.75" Hg is the equivalent of a 0.857 PSI in the exhaust system.

If the calculations are correct, that amount of pressure seems reasonable to me.

Comments?

My goal here is to ascertain if we are ready to update the VE tables or presently fighting something else. .

The car “feels” ok while driving in Closed Loop. The drivability is pretty good given the fairly nasty (street car) camshaft.

Does anyone have a VE table that they are willing to share? My desire is to understand where the rough ballpark is located for this type of engine.


I look forward towards your tuning advice.

Best Regards,

Bruce

 

Dont have a bin to compare but on the engine dyno, what was the exhaust and air intake used?

Probably just a load difference at idle. Does engine dyno simulate trq converter load at idle? If not there may be some difference. Also how much load can it apply for part throttle? Same as a 3500-3600 lb street car?

I wouldnt be too concerned with the difference if exhaust was much different than whats on car or if no air intake was used. Or even if dyno load was different.

I would just start making corrections. Idle blm may not be perfect due to overlap of cam so just note that.

As always, check plugs to verify narrow and wideband o2's

 

Thanks Orr89RocZ.

Forgot to mention that I am running a TKO-500 manual transmission.

The dyno Intake was unrestricted.

The dyno headers were 4 into 1. 1 3/4" primaries and 3" collectors.

My headers are custom Dyno Dons. The standard 1 3/4" primaries were used. However, the collectors are 3" rather than the standard 2 1/2".

Maybe the headers are the difference?

Best Regards,

Bruce

 

Possible. Maybe intake unrestricted as well? Hard to say for sure but if it feels ok then nothing really to worry about imo.

 

Bruce, just emailed you my whole bin...

Only, make sure to put it into context with my engine set up from our earlier e-mail exchanges.

 

Thanks for the BIN reference.

The help is much appreciated!

Best Regards,

Bruce