View Poll Results: Would you swap out a 2.73 R/P transmission for a 2.2 R/P one on a >400rwhp 928?
Yes, I think it would be worth it and the lower gears would suit the additional power better
57.14%
No, I don't think it would be worth it, plus it would inevitably make the car *seem* slower
42.86%
Voters: 21. You may not vote on this poll
Question for the >400rwhp club
03-04-2008, 07:13 PM
#46
Rennlist Member
I dont know what tires you are running, but there is no one running 24" diameter tires with that kind of hp on the track (or street i would hope)
generally, rear tires will be 25 to 25.7" talkng about 295 to 335 tires.
Mk
generally, rear tires will be 25 to 25.7" talkng about 295 to 335 tires.
Mk
Here's some more concrete info.. courtesy of FlyingDog's handy excel sheet..
the excel sheet is found here:
https://rennlist.com/forums/showpost...0&postcount=57
Edit: The tyre size is based on my 17" aftermarkets.. YMMV for 18" or whatever you racers use
Disclaimer: I'm not in the 400 rwhp club yet.. still working on getting engine up to stock performance on dyno before I consider mods.
the excel sheet is found here:
https://rennlist.com/forums/showpost...0&postcount=57
Edit: The tyre size is based on my 17" aftermarkets.. YMMV for 18" or whatever you racers use
Disclaimer: I'm not in the 400 rwhp club yet.. still working on getting engine up to stock performance on dyno before I consider mods.
03-04-2008, 07:16 PM
#47
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on the street and all tracks if you have a top speed of no more than 155mph
Getting into 5th gear is a good thing, direct drive to the diff.
03-04-2008, 07:22 PM
#48
Rennlist Member
The answer for the survey should be answer 2. It is not going to suit the 400hp better, or worse, unless you know the operational speed range it will be used in. There are just as many ranges that will not be helped (sans looking at 1st gear, where there is wheel spin anyway).
I just did the test again , being real gentle. 3k 4k , rollling on the throttle, with 13" wide rear tires, the sticky race rubber spins wildly. so, any gains in the 0-25mph range, would be washed in wheel spin and the rest of the comparison would depend on the majority of the speed ranges you would spend time in.
For example, if i was spending most of my time at 95 to 115mph, 40 to 55mph, 70 to 80mph, the 2.2 box would be best. If the ranges are different, it might favor the 2.72/2.75 boxes. it depends. There is no right answer here. also, as you add hp, those operational ranges might change at the track. anderson with 500rwhp needs the 2.75 for tracks we visit together, while 300-350rwhp would require 2.2 to have the best HP utilization. at sears this might change. at limeRock, Willows, etc, all the speed ranges might change. a lot of factors. one thing for sure, is that the 2.2 giving 2200rpm at 70mph on the freeway in 5th gear, is nice.
Mk
I just did the test again , being real gentle. 3k 4k , rollling on the throttle, with 13" wide rear tires, the sticky race rubber spins wildly. so, any gains in the 0-25mph range, would be washed in wheel spin and the rest of the comparison would depend on the majority of the speed ranges you would spend time in.
For example, if i was spending most of my time at 95 to 115mph, 40 to 55mph, 70 to 80mph, the 2.2 box would be best. If the ranges are different, it might favor the 2.72/2.75 boxes. it depends. There is no right answer here. also, as you add hp, those operational ranges might change at the track. anderson with 500rwhp needs the 2.75 for tracks we visit together, while 300-350rwhp would require 2.2 to have the best HP utilization. at sears this might change. at limeRock, Willows, etc, all the speed ranges might change. a lot of factors. one thing for sure, is that the 2.2 giving 2200rpm at 70mph on the freeway in 5th gear, is nice.
Mk
03-04-2008, 07:27 PM
#49
Rennlist Member
Just using straight math, no guess work, especially on the track.
can you give me your speeds in each gear? have you plotted out your speeds at each tracks straights before braking zones? Then, calculate time spent in each gear to see if HP is maximized??
That statement is pretty lame when you think about what it takes to be fastest around the track. Many factors and trade offs. too many to list. it depends.
2.2 can be good for one track and a 2.75 can be good for another. 2.64 can fit others as well.
Direct drive only buys you a small percentage of efficiency. im guessing 2-3% at best. I dont know, maybe someone with the "Facts" can chime in on a part of a dyno run in 5th compared to 4th.
Mk
can you give me your speeds in each gear? have you plotted out your speeds at each tracks straights before braking zones? Then, calculate time spent in each gear to see if HP is maximized??
That statement is pretty lame when you think about what it takes to be fastest around the track. Many factors and trade offs. too many to list. it depends.
2.2 can be good for one track and a 2.75 can be good for another. 2.64 can fit others as well.
Direct drive only buys you a small percentage of efficiency. im guessing 2-3% at best. I dont know, maybe someone with the "Facts" can chime in on a part of a dyno run in 5th compared to 4th.
Mk