25 top gear ,overdrive, 12 psi supercharger

[blown apex]

apex gt, stage 1 supercharger 12 psi
will i have enough power to pull a od primary clutch and 25 top gear
or should i leave the 24 in it
looking for more top speed
thanks

 

[HAMMER]

Did a quick search and found this...lots of info out there...

According to my measurements and math bone stock clutches have a ratio of 0.977:1 at full shift with a new broken in drive belt with 20-30 miles on it. If your tachometer is spot on running 10800 your primary clutch spins at 8757 rpms giving a theoretical top speed of 126.6 MPH. You are very close to running out of gear running 122 mph. If you have a machined/aftermarket helix your clutch ratio is close to 0.93:1. If you can raise the drive belt to the top of your primary your clutch ratio will be close to 0.85:1 - Clutches are most efficient running at a clutch ratio of 1:1

Thanks for the reply. I understand the 1:1 ratio being more efficient however to hit my top speed, I cannot change the gears that much more or I will start to loose acceleration. I am already at a 26-38 and I am running BIG mph but I want to step back to say 24-38 gain acceleration but still be able to run 130's keep in mind with a machined clutch how often are you going to be running at the top anyways? It’s only for the odd lake race of 2000' not day in and day our radar running.

You'll get great bottom end pull and fast acceleration and still get a descent top end going with a machined primary/secondary combo. With both primary and secondary clutches prepared for OD you will get close to 0.84:1, and yes you have the power to run it into OD. Running 24/38 for gearing, the theoretical top speed will be close to 140 MPH, but due to clutches being less efficient at OD your top speed will more likely stay closer to 130 MPH than 140 MPH.

 

[DC5]

25 top gear with overdrive is good for 138 mph on radar. At 12psi with a trail setup you will only hit that speed if you are on a 2000' or longer ice track with a slight tail wind. 24 tooth is good for 132 mph on radar on ice with rpm's at 10,800.

 

[visegrip]

25/38 gave me 129.9 with an attack turbo and 1 1/4 track

 

[DC5]

25/38 gave me 129.9 with an attack turbo and 1 1/4 track

Because you ran out of power

I thought you had a 24 on top?

 

[stone88]

I ran 25/38 on my sled and ran 138.38 at Martin Last week the best I could get with 24/38 was 134.

 

[hlmrx1]

Ran a 137.13mph with 24/38 10 tooth drives and tail wind at the track this weekend, best ever! Didn't think it could happen.