Can someone please help me understand "shift extension"?
Can someone please help me understand "shift extension"? I've noticed more than a few threads talking about shift extension. But I haven't seen a detailed extension of what it really is, or how it should be applied to a hp/tq curve. Even if it's just a link to a detailed writeup, can someone educate me on it?
Thanks
Maybe for an example, can you use this dyno sheet to explain what I should be using for a TC. One run was on the bottle, one wasn't:
Thanks
Maybe for an example, can you use this dyno sheet to explain what I should be using for a TC. One run was on the bottle, one wasn't:
11 Second Club
Joined: Oct 2004
Posts: 418
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From: Pembroke Pines,FL
Shift extension is how low your rpm drop during a shift. I shift at 6700 & it drops to 4800 in the next gear with my Vig3200. I planning to up my converter to the TP4000 which they tell me the extenion would be raised to 5600rpm. You want to have a converter that works with your peak tq & hp curves.
What's the number of rpm's you ideally want to drop
I currently shift at 6600 rpm's due to not trusting factory rod bolts beyond that. And by looking at my autotap logs, the rpm's drop to ~4800 rpm's after shifts. So by the dyno sheet above, to optimize it, I'd either need a nitrous TC with a shift extension of about 6200 rpm's, or get a cam with a peak hp around 5200 rpm's.
Correct?
Correct?
TECH Fanatic
Joined: Oct 2003
Posts: 1,132
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From: Grand Rapids, Michigan
You also need to think about what you are going to do with the car... mostly street some track of the other way around. I say that because to get the extension you are looking for(6200rpm) you are going to need a big stall (4000+) and most will agree that is a little much for the street. Most yank SS series users really like how well they drive even in the 3800 range, I believe they make a SS4000 stall. You should ask around and see how they like them for both srteet and track use.
Ok. Well, thanks for answering my questions and educating me on it everyone. I think I'll just hold off until I get my LS2 402 built and deal with another TC change-out then. I'll just deal with what I have for one more season. I have the feeling I'd better pick a cam for it with a significantly lower peak horsepower though.
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Restricted User
Joined: Apr 2004
Posts: 377
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The TC people call it "shift extension". It has nothing to do with the shifts "at all". It is the ability of the TC slipping (due to diameter, higher stall, etc.) that keeps you in the "desired" rpm range. Shift extension is a misnomer. Example a 12" TC (rated 1,800 rpm stall) when the 1-2 WOT shift is made at 6,000 rpm will barely keep it in the "desired" rpm range that is desireable at the end of the 1-2 shift. A 9.5" TC with a 2,800 rpm (modest stall) & with a 6,000 rpm 1-2 WOT shift will hardly notice the drop off in rpm's (the big rpm drop on the 1-2 shift is gone). The higher the stall with a smaller diameter TC will get you smaller rpm drop offs between shifts. So you see that this has nothing to do with the so-called "shift extension".
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