Diablo/Pred/etc and Automatics...

[Kent5]

Hello all,

Does the Predator/Diablo/etc units do anything with the downshifting behavior of the automatic trans? Let me explain...

I'm not talking about changing RPM upshift points or the 'firmness' of the shifts. What I am wondering is if the programmers can actually change *downshift* behavior.

For my preferences, I'd like the car to be more aggressive in downshifting, maybe with less throttle opening. Seems like I have to really put my foot waaay into it to get a 3-2 or 2-1 downshift... like the car really wants to avoid going down a gear... fuel mileage biasing?

Do any of the reprogrammers address this?

(sorry if this has been rehashed 1,000 times before... I did a few searches and didn't see my question)

Thanks!
Kent
2006 GT

 

[anthony05gt]

I haven't noticed this question yet. I know the tranny doesn't use a valve body. All is controlled by the pcm. You can't adjust that with a hand tuner as far as I know, but I'd guess that a reputable shop could let you in on that info. If it can be done, they would load a custom tune into your predator and you could install it yourself. You really need to talk to someone that has a lot of experience with tuning these cars.

 

[Kent5]

I hadn't seen the question either...

It's really more of a day-to-day driveability thing... part-throttle behavior. But it sure would make the car feel a lot snappier if it was a little more eager to downshift without having to go WOT...

Seems like it should be very possible to "tune" downshift behavior if it is all PCM controlled... change the throttle position sensor downshift trigger value from 90% to 70% or something. I'm sure its more complex than that, but you get the idea....

 

[GT-Tronics]

I have the xcal2 and it has fully adjustable shift points up AND down, predator does not. The xcal2 also eliminates throttle lag, instead of gas and wait...you gas and GO.

The adjustable shift point screen (on the pc software) looks like a graph with 8 color coded lines, 4 for upshift, 4 for down.You grab one of about 6 points on each shift line and move it anywhere you want.The line moves accordingly from dot to dot.
On the graph Left to right is throttle position, up and down is vehicle speed. I Cant take a screen shot right now Im on a mac at work.

You would basically tell it at what speed you want it to down shift (or upshift) at any given speed.

You save this file to the Xcal, then upload it to your car with the tuner.