[Power Hungry]

Originally Posted by tohi2care

Well I have been trying out the different tunes and I'm not sure what to think. I can say that there is definatley a difference from the canned tunes, but between the 87 performance and 87 towing I can't really tell the difference. I can tell the 87 economy shifts alot sooner and softer but my milage didn't really go up compared to the other custom tunes, in fact I get my best milage with the performance tune. I haven't hooked up my boat to test the towing tune but with no load it behaves very similar to the performance tune. I was also recieving a very unusual shift from first to second when accellerating from a stop, pedal to the floor. It feels like the truck is losing fuel pressure from 2500-5000rpm and then when the shift is supposed to happen it feels like all power is lost and magically returns with a CRAZY hard shift in both the performance and towing tunes. It did not happen at all with economy tune or when returned to stock. I say it seems asthough fuel pressure is lost because it feels the same way (acceleration wise not shifting) as when the truck is reading low fuel on the info center and I punch it and the truck surges obviously from fuel moving away from the pick-up in the tank. I tried to reproduce the same situation today but could not thankfully. I think it could be related to my fuel filter not being changed for about 30,000 kms, so I am getting it changed next week.

Is it possible to get say a "build sheet" of our tunes to see what was adjusted and by how much compared to stock?

A build sheet? Doubtful. There are simply too many parameters to begin listing down all the modifications. I could give you a rough idea of what was changed but the details are simply too involved.

The biggest difference between 87 Tow and 87 Performance is fuel curve, shift torque mgmt., and minor shifting adjustments. As for the 87 economy, the shifts are early and unless you drive like grandma you may not see much improvement. Even then, it's tricky. If you decide you don't like te economy program and want something else, I'd be happy to replace the file for you.

As for the "fuel" issue? It could be related to the Open Loop fuel curve, the MAF transfer curve, or even something that simply corrected itself after the computer had a chance to relearn some of the strategy. All I can offer at this point is if you experience the issue again, let me know so we can investigate it and make any necessary changes.

The crazy hard shift probably occurred because the PCM is expeting a certain amount of torque output from the engine and bases the shift timing and pressure on those values to achieve the desired slip. If for some reason the engine output falls off just before or during the shift, the shift will then become overly aggressive.

Originally Posted by SinCityFX4

I am sure Bill will pop in here and explain things for you in a detailed manner with his massive intellect.