Hard cold start with corrected voltage offsets
 

Running $6E, stock 305 with 24lb Bosch III's.

By dropping the voltage offsets for the Bosch design III's, it seems it creates a situation where the injectors are not firing for long enough at low cranking voltage

Are the voltage offsets used during cranking? When the voltage for the injectors drops to ~9v, will I need to adjust the cranking PW?

I changed the voltage offset tables to reflect what the Bosch III's are supposed to run and it seems to make the idle INT less stable and causes difficulty with cold starting.

Anyone have thoughts or experiences here?

GD

Re: Hard cold start with corrected voltage offsets
 

Voltage offsets have their greatest affect at small PW since the offset is a constant for that particular voltage. So it constitutes a larger portion of the calculated PW. If ur Cranking PW hasn't been modified after introducing the new offsets, u should probably try doing that.

Re: Hard cold start with corrected voltage offsets
 

Did you disconnect the ECM to reset it? If not I'd recommend doing so. Probably won't help the cold start but may help the INT as it'll unlearn everything from the earlier injectors and settings.

Re: Hard cold start with corrected voltage offsets
 

Since I'm doing a lot of tuning and learning as I go - and doing it with a car that till about a year ago had sat for 11 years I'm not entirely sure the injector offsets are the only issue. It definitely seems *better* with the normal offsets. And it did seem that INT swing was not as pronounced with the factory offsets....

I have not seen anything during the normal running that would indicate any other lurking issues. Only other thing that comes to mind is possibly a weak spark during cranking when the voltage is dropping to 9v. I've done all the tune up parts but I keep reading about pickup module failures, etc. Weak spark with low voltage to the module/coil? I'm planning to go to the small cap distributor.....

I have done all the tune up parts - this behavior seems to have cropped up around the time I switched to 1.6 rockers and did new springs and valve stem seals. By my (admittedly rough) MAF calculations the 1.6 rockers were good for 3.8 HP on the top end of my stock 86 LB9. Could the rockers be pulling in enough more air that I need more fuel?

I'm going to try increasing the cranking PW multipler vs. reference pulse and give it a larger shot of fuel earlier in the cranking.

I will disconnect the ECM and make sure it's cleared out.

Thanks!