130mph, 26" tall slicks, what diff gears should I have?

[EV1LR8]

DAM u pricks getting super low 60's

i pushing hard to get the 1.7 1.8's with the M6

[Brett SS]

it's a triangle calculation...ie .....*imho* car set up beats brute HP each and every time.

368rwkw / 3.9 Diff Gears / Vigilante 4200 High Stall / Full street weight sans Pro lights.......Running 28" MT Drag Radials . ANDRA Race number 3106..driven to and from track...Willowbank Brisbane return.

Edit , sorry brett SS...EFI logs have me crossing the traps at 6950rpm locked in 3..bit of TC slip there but the Vigilante does the job imho

Thanks for your info Mark, but your track is a MASSIVE reason why you are able to 60' the way you do. When you're limited to Heathcote you are happy when running into the 1.5's...

[dogsballs]

went out to heathcote yesterday. had issues tagging the limiter keeping it in 3rd, with new 4.10's, my old 235/60/15s on a 15x8 rim. had issues with auto shifting into 2nd early so thought that was the reason for hitting limiter.

however after a bit of measuring and calcs today (25.5" tyre diameter, 4.10 gears, 7000 rev limit) this should be able to manage ~129mph, but factoring in convertor slip this will drastically reduce. Luis from APS who tunes the car has mentioned that with our recent shift to e85 and massive improvements in the tune the convertor was flaring over the 4500 (possibly 4900), but it must also be slipping a bit more. Using the 7% thrown around earlier this rounds out to 119mph, which was the fastest i saw on weekend.

sooo, if i go to a 255/60/15 radial, should push out to 137mph theoretical or go to 3.9's 135mph.

actually, it might have something to do with my 15x8 rim, as last time at calder i borrowed a mates 235/60/15 on a 15x7 (as his have tread and i drove there). recalculating this should get an extra 4mph.

[ittwgn]

yeh theoretical speed is one thing but as you say with converter slip=??? dont get what your saying about 15x8 rim!!!! extra weight???cheers

[dogsballs]

235/60/15 radial designed on a 7" rim. on 8" it drops the diameter to 25.6" in my case with worn tread. measured mates on 15x7" and its 26.2", doesn't sound a lot but calcs show an extra 4mph. will try those next outing till i can afford some 255/60/15's.

[Brett SS]

What converter are you running in yours? You probably have more like 10% slip if it's an inefficient converter. With my 4500rpm converter which was initally built by Dominator (has been rebuilt since) probably has close to that as I lock mine up after 6000rpms in 3rd and you get another 10mph or so out of that gear before hitting the limiter...

went out to heathcote yesterday. had issues tagging the limiter keeping it in 3rd, with new 4.10's, my old 235/60/15s on a 15x8 rim. had issues with auto shifting into 2nd early so thought that was the reason for hitting limiter.

however after a bit of measuring and calcs today (25.5" tyre diameter, 4.10 gears, 7000 rev limit) this should be able to manage ~129mph, but factoring in convertor slip this will drastically reduce. Luis from APS who tunes the car has mentioned that with our recent shift to e85 and massive improvements in the tune the convertor was flaring over the 4500 (possibly 4900), but it must also be slipping a bit more. Using the 7% thrown around earlier this rounds out to 119mph, which was the fastest i saw on weekend.

sooo, if i go to a 255/60/15 radial, should push out to 137mph theoretical or go to 3.9's 135mph.

actually, it might have something to do with my 15x8 rim, as last time at calder i borrowed a mates 235/60/15 on a 15x7 (as his have tread and i drove there). recalculating this should get an extra 4mph.

[dogsballs]

same, 4500 dominator (although since on proper e85 flaring a bit 4700-4800). we have it locked but over 120mph (which would we aren't even seeing at the moment on my tyres). although jason recommended not to do it.

interesting, thanks didn't think of that. so could keep the tyres

[Brett SS]

It's always not "recommended" but if you are locking up the converter well past the stall speed (ie 6000rpms) then the converter can't flare any further and should lock up ok.

I have done it plenty of times with my blower with a lot more torque and it's still holding up well. However of course it will reduce the life of your converter clutch so you may need to get the lockup clutch material redone at some point.

same, 4500 dominator (although since on proper e85 flaring a bit 4700-4800). we have it locked but over 120mph (which would we aren't even seeing at the moment on my tyres). although jason recommended not to do it.

interesting, thanks didn't think of that. so could keep the tyres

[solid]

Have ppl seen an improvement on times by locking their converter? I run 3.73 gears with the stock engine, stock trans and stock stall and pulled 11.26@130.5mph at 6430rpm over the line. That's using 26 inch tyres. Is be interested to hear about what gains are to be had by locking the converter as I've never done it

[munz]

Does that mean the converter locks in 3rd or just overdrive?

I'm looking to buy one (4000) and have the option to upgrade to a multidisk one for lockup at WOT as I've hit the limiter in 3rd last year (6400-6500)
so is there more chance to hit the limiter in 3rd with a converter?

[Brett SS]

Have ppl seen an improvement on times by locking their converter? I run 3.73 gears with the stock engine, stock trans and stock stall and pulled 11.26@130.5mph at 6430rpm over the line. That's using 26 inch tyres. Is be interested to hear about what gains are to be had by locking the converter as I've never done it

I only ever locked up mine in 3rd above 6000rpms but I'm running 4.11's so I need that extra RPM I can get out of 3rd by locking it up. There can be a small gain in MPH and ET (maybe 1-2 tenths and 1-2mph) as you gain that extra power you are normally losing in slip...

You should give it a try at some point but make sure you're locking it up well above your stall speed so that it doesn't fry the clutch...