You're right in that shorter tires do help initial acceleration and slow down topend acceleration, but I believe Jime is running 22" slicks which are incredibly short. I believe the main reason he runs the super short slicks is to get the massive torque multiplication to lower the OEM long gearing.

I thought I've seen DE-K dynos showing a 5000rpm switchover as stock? I know that the MEVI needs at least a 5000rpm switchover even though ideally it appears a 5200-5400rpm is better at the track....at least for most of us. You're right though, they are different manifolds and appear to perform a little differently (ie the DE-K breathes better). I just know that when I opened my MEVI at 4500rpms on the dyno, my car suffered a 15whp loss.


Dave

 

Shorter tires might, or might not hurt your top end. It just depends on the tire size and your power curve, and where it's requiring you to shift at. You could be using a tire that requires you to shift into 4th gear 150 feet before the finish line, causing you to finish the 1/4 accelerating thru like 5000rpm in 4th, where you might only be making 180whp. If you used a slightly shorter tire you might need to shift earlier, say 300 feet before the finish, and end up accelerating thru like 5600rpm in 4th, where you might be making 190whp or something, and potentially trap higher. It all just depends. I've run on tires of basically 3 different sizes. Stock, significantly smaller than stock, and significantly larger than stock, and I don't see much of a trap speed difference at all. If they were sized so extremely that it forced an extra shift, or put me in a weird part of my power curve it might do some harm (or some good).

 

Thanks Neal...that makes sense.

Dave B - Yes, stock DEK switchover is supposedly "above 5000rpm", but the hp/tq spike seem to occur close to 5100rpm. If it is EXACTLY at 5K, it's probably just an ~100rpm delay between the time it takes the power valve to switchover and the engine/drivetrain/dyno to respond.

 

My stock tires are 25.0". I've used 22.0" Toyo T1-S for the track and 23.0" BFG drag radials. Both have helped me in the 1/4 mile. But 20.0" would be the best gearing for me all motor. With the 22" tires, I would be just barely getting in the sweet spot in 3rd gear as I pass thru the traps. With stock tires, I would be at the lowest part of 3rd gear where a stock Saturn can pass me then. lol

But when I start spraying nitrous, I will need to alter my tire size so that I will be near the top of 3rd gear as I finish. But, I will need to know my expected best trap speed. Then I can figure it up. Like Jime said, shifting into OD with a 100+ shot, isn't the best thing for the automatic tranny since there's no way to quicken that shift.

 

Sorry, I have been out of town.....way to go Krismax!!! I bet there is plenty more to get out of her with the set up you have. Cooler weather, different shift points, and a better 60' foot. Can't wait to get back out the track myself.