engineermike

I recently installed a set of 84 lb/hr Delphi injectors in my '95 LT1 with LJ's Accelleronics Impedence Converter.

With an 86 lb/hr injector constant, the Lterms are 126 - 131. The car idles and drives fine, and the A/F ratio at WOT looks good.

However, when cranking the car (cold or hot), it doesn't start very well. If you hold the throttle open, though, it starts up fine.

I have set the injector offsets to zero at 8 - 10 volts to lean it on start up, which has helped. However, it still doesn't start quickly.

I've seen in the tuned port and '93 LT1's a table for Crank Fuel Addition. However, that table isn't in TunerCAT. I think that leaning this table would make my car start right.

Does anyone know how to access that table?

Any other suggestions?

Thanks,
Mike

engineermike

^^^

tjwong

Mike,

Are you using Tuner Cat? If you are using it and if you have a registered copy of the software email TC at TunerCat. He has a new EE definition file that has cranking AFR vs Distributor reference pulses, and 4 priming pulse tables. That will fix your problem, I have large injectors in my blown 396 LT4 and I had a similar problem but not as bad as yours.

slopokrodrigez

Why are your injectors so large?

Just curious as I have yet to add a blower and thought I may be missing something.

84 * 8 * 0.8 / 0.5 = 1075HP

Is this formula not reliable?

What's your crank HP?

engineermike

For Forced Induction, use a BSFC of .65 because they like to run richer. The extra fuel cools the intake charge.

84 * 8 * .8 / .65 = 827 hp

Also, I was going to use 75 lb/hr:

75 * 8 * .8 / .65 = 738 hp

However, I talked to LJ:

http://para.noid.org/~lj

He recommended the 84 lb injectors because there is no 'disadvantage' to using them. They don't cost much more than 75's, but they'll support more power.

The downside to very large injectors is that the computer may not be able to cut the pulse width enough at idle. But, he said his 75's had an idle PW of 1.3 ms and his 95's have an idle PW of 1.0 ms, which is the lowest the computer will go. So, the 84's will support a ton of power and idle at >1 ms PW, the best of both worlds.

Mike

TriPinTaZ

Whats your closed throttle spark advance?
and low RPM cranking advance?

I had this same problem, even after leaning it out at starting it still didnt start too well. Setting my closed throttle spark advance to 40 i dont even have to tocuh the gas pedal and it fires right up on 1st crank.

engineermike

The closed throttle advance was 0 at 0 rpm and 20 at 400 rpm.

I changed it to 20 at 0 rpm and 40 at 400 rpm and the problem is almost gone.

Thanks for the advice!

Mike

TriPinTaZ

i set mine at 40 all the way across, the engine is turning less than 400 RPM during cranking. Mines fires up jsut as easy as it did stock after setting it to 40 @ 0 rpm and 400 rpm