Well I have been strugling with the stock PCM. My powerband goes well above 7000 RPMs but the factory PCM only likes to work properly to 7000. However with my experiences on the dyno and while data logging I will let everyone know what happens after 7000 RPMs.

Basically any RPMs over 7000 result in the PCM jsut using the last fuel/spark cell it was just in. So if you had 36 degrees of timing at 7000rpm, VE at 97.6, and PE table at 14% + the PCM will continue with these exact numbers past 7000. I spun my engine to 7600 a few times on the dyno. The dyno cahrt shows the PEak HP at 7000 RPMs and then the TQ and HP rapidly decline. Ofcourse the reason being is the car needs MORE fuel spinning that fast which the PCM is just NOT adding. One trick we used was to take the last cells and fatten them up big time, but this is only a bandaide. Now another thing that happens is the MAF sensor cannot measure air beyond 511 GPS and I belive this is also a factor in the car starting to "shoot ducks" or "lean popping" as most would say when beyond 7200 RPMs.

This ofcourse will all be solved with an after market ECU like Accel DFI 7 which eliminates the MAF and will allow me to spin to my 7800 RPM shift point while controling a dry stage of nitrous. Dont forget teh MDS 6AL digital ignition with "REAL TIME" spark retard when the NOS is activated. I wouldnt want to blow a piston thru my hood.

Just figured I would share a learning experience with you all. I havent seen anyone attempt to spin this many revs from a small block LT1 before.

 

I read somewhere about LS1 cars dividing the MAF values in half and that allowed the stock MAF sensor to effectively read double its normal capacity. I don't know if that makes sense (it is over my head) but it was a hell of a lot cheaper than an aftermarket ECU. They were talking about stroker/heads/cam cars spraying like 200-350 hp shots and they were able to make the stock MAF sensor read it. I don't think the Lt1 stock MAF is as good but maybe it is something worth looking into. Of course that doesn't fix the problem over 7000 rpms.

Dustin

 

It's interesting, since most people I know who have went over 7K have their car just shut down. Usually they get to about 7200 RPM and then the car just shuts down. Maybe there is something different with the 97 PCM that would cause this, most of the cars that I've heard of shutting down are like 94 and 95.