rsilver

I am running an 8746 ecm and am pretty well dialed in on fuel and spark..........I think. My Blms are in the 126- 128 range, and the WBO2 tells me at WOT I am in the 12 to 12.5 AFR range depending on conditions. At part throttle cruise I am in the 14.6 to 15.0 range.

The last thing I am trying to work out is I notice a power loss when the engine warms up and goes to closed loop.
I have dual snorkle air intakes so i think I am getting as much cold air as possible (although I know its not true cold air) and the car runs between 180 to 200* on average days. Are there any specific tables I should be looking at
that could help me with better performance at higher operating temps?
In all other respects the drivability of the car is excellent, I am just trying to see if there is something I have missed on this issue.
thanks very much..............bob

Grumpy

Couple things in effect here.
The 8746 has no MAT/IAT corrections. So once you remove the Thermac, they can wander all over the place.

And it's not so much as a power lose when hot, as there being a power increase when cold. Colder just means having more fuel and more timing. And with the fuel in a less ignitable state, the motor is less likely to detonate.

And it's easy to mistake throttle response for HP.

rsilver

Grumpy, thanks for the response. makes sense.

Do you think it is worthwhile to convert to the 8747 ECM to help with this IAC issue? Would I be able to get a substantially better tune with this ECM ?

Thanks..........bob

JPrevost

The 8746 does have MAT/IAT corrections... it's just very course without a patch .
It's a good ecm that's just as hacked as the 7747 so there really is no need for anybody to still be using the 7747!

RBob

iTrader: (1)

Bob, not uncommon to feel a loss of power once the engine goes closed loop. Typically they are being run leaner then the open loop AFR's.

Force open loop by setting the closed loop temperature at max temperature (set $22B to zero).

Then drive it around and see how it is.

RBob.

rsilver

Ok, I am relutcant to ask you guys this since my only experience with tuning is win aldl, a WB02 and the cats tuner and a pocket programmer. I don't know what "$22b" is , how to find it , how to change it to 0 . I just don't know anything about this. I see references to these things all the time and I haven't been able to figue this out from articles I have read. Also I see the word "patch" a lot but I don't even know what that is.

Could you guys referr me to something that would help??

Jon did a thread about getting the 8746 to show final SA and knock SA, so I downloaded tunerpro and followed his instructions in the thread but I never got any meaning info. Just 0's in promida and occasional numbers in promidb (which I assumed where knock retard).

I would really like to try what rbob and jon suggested but this is a level I don't understand.

Your help is appreciated.............old carb guy bob

RBob

iTrader: (1)

I looked at JonP's ECU file and found this entry:

Constant 36: Closed loop coolant threshold

Set that value to 0 for no closed loop.

RBob.