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Yeah I remember that guy. In fact he was selling his car some years back and it was a good deal. Don't see why they couldn't sort the roll centres out properly though?
I'm probably looking at it too basically but I'd still think longer = better in theory.
My interest in a Corvette setup would be to include the suspension, not just the gearbox. While your build and Dukes with not dissimilar suspension is fantastic, ideally if you were to go with a blank sheet of paper you'd want suspension with longer arms/levers than a rear engine Porsche can fit. Might be being picky but the longer levers should keep the wheel in a more vertical state for more of the time compared to the shorter Cup levers. Of course the Cup suspension has had a zillion dollars spent on it over the years in terms of R&D but you'd also think that there would be a fair bit of time spent on the Vette rear end. Plus assume parts would be considerably cheaper. Overall a full Sequential gearbox would be better still but there's a limit to expenditure and one has to examine R.O.I. before making such leaps!
The 996 rear setup on my car was chosen by the chassis engineer as a "low" budget setup compared to the top choice that would be a 100% custom built double a arm setup (as I have on the fornt). With that said if you want to take a setup from an existing car I don't think there's much better choices than the 996/997.
Gearing is more a matter of track layouts. The 968 gearbox is perfect for the tracks that I run. In the slower corners I can stay in 3rd whereas with the 951 gearbox 3rd would be too tall and 2nd too short. I see no reason to change it unless I would go sequential.
The 968 gearbox is perfect for the tracks that I run. In the slower corners I can stay in 3rd whereas with the 951 gearbox 3rd would be too tall and 2nd too short
if it hasn't been said a few times already it's probably easy to underestimate Tony's comfort level with using 3 gears (until you'd be driving the car) when the 3.0's more peaky torque demands having 4 usable gears....
btw, on the '68 box, 3rd and 4th might feel a bit tall, (as in fact, they are), compared to the short 5th and 6th.
i imagine (Gustaf and Patrick) are close to 25" tires. where Tony's got to be at least 26" ??
1 3~6 combo that could theoretically work for his big engine would be the factory 968 Turbo ratios and diff.
1st; 3.182 :1
2nd; 2.000 :1
3rd; 1.435 :1
4th; 1.111 :1
5th; 0.882 :1 [oem is .992]
6th; 0.711 :1 [oem is .778]
diff; 3.45 [[oem is 3.778]
still, short of a pdk type transmission, would having 4 good gears even make his car faster?
would a pdk box and 4 useful gears help the 3.0 ??
Last edited by odurandina; 09-16-2014 at 10:31 AM.
if it hasn't been said a few times already it's probably easy to underestimate Tony's comfort level with using 3 gears (until you'd be driving the car) when the 3.0's more peaky torque demands having 4 usable gears....
btw, on the '68 box, 3rd and 4th might fell a bit tall, (as in fact, they are), compared to the short 5th and 6th.
i imagine (Gustaf and Patrick) are close to 25" tires. where Tony's got to be at least 26" ??
1 3~6 combo that could theoretically work for his big engine would be the factory 968 Turbo ratios and diff.
1st; 3.182 :1
2nd; 2.000 :1
3rd; 1.435 :1
4th; 1.111 :1
5th; 0.882 :1 [oem is .992]
6th; 0.711 :1 [oem is .778]
diff; 3.45 [[oem is 3.778]
still, short of a pdk type transmission, would having 4 good gears even make his car faster?
would a pdk box and 4 useful gears help the 3.0 ??
Well I think you're underestimating a well built 3.1l 16v turbo engine as it is nothing peaky about it. Anyways, it's not only about having a broad torque curve. If a specific track layout have corners that will drop you to say 2000 rpm in 3rd gear with a 951 gearbox that will seldom be the quickest way to accelerate down to the next corner regardless of engine. So I will repeate what I said that it depends on track layout and not only engine.
I disagree. Any 4 cylinder turbo race engine is going to be peaky compared to a equally prepared V8. In fact, I would bet that the V8 has a usable power band area close to double that of a turbo 4 (even a 3.1) in terms of usable rpms.
I can come out of a corner at 2500 rpms making 400TQ at the wheels, 450TQ at the wheels at 3000rpms and make peak TQ of 500TQ at the wheels at 4500rpms and a peak HP of 575HP at the wheels at 6500 rpms and still make 500HP at the wheels at 7000rpms.
This is why I can run a 951/S2 box as a 3 speed without any problems. Would I like a sequential box? Yes. But given the quantities of shifts I need to do with a fat power band like I have it just doesn't justify the cost.
But if I was running a turbo 4 (any turbo 4) I would probably spend the money on a sequential.
TonyG
Originally Posted by Duke
Well I think you're underestimating a well built 3.1l 16v turbo engine as it is nothing peaky about it. Anyways, it's not only about having a broad torque curve. If a specific track layout have corners that will drop you to say 2000 rpm in 3rd gear with a 951 gearbox that will seldom be the quickest way to accelerate down to the next corner regardless of engine. So I will repeate what I said that it depends on track layout and not only engine.
The rear tire is 18" 330 40% witih a circumference of 86.32" with a 6800rpm shift point
TonyG
Originally Posted by odurandina
if it hasn't been said a few times already it's probably easy to underestimate Tony's comfort level with using 3 gears (until you'd be driving the car) when the 3.0's more peaky torque demands having 4 usable gears....
btw, on the '68 box, 3rd and 4th might feel a bit tall, (as in fact, they are), compared to the short 5th and 6th.
i imagine (Gustaf and Patrick) are close to 25" tires. where Tony's got to be at least 26" ??
1 3~6 combo that could theoretically work for his big engine would be the factory 968 Turbo ratios and diff.
1st; 3.182 :1
2nd; 2.000 :1
3rd; 1.435 :1
4th; 1.111 :1
5th; 0.882 :1 [oem is .992]
6th; 0.711 :1 [oem is .778]
diff; 3.45 [[oem is 3.778]
still, short of a pdk type transmission, would having 4 good gears even make his car faster?
would a pdk box and 4 useful gears help the 3.0 ??
Everything is more peaky than a 6-7 liter N/A engine but that doesn't make it peaky per definition. Below is my old 3.0l 16v engine and my new engine have a broader powerband. Not what one would define as a peaky engine.
But I never stated that a smaller displacement turbo engine have as large powerband as an LS engine. Anyone can understand that's not realistic. The only point I made was that gearing is track dependent. And now both you Tony and odurandina seem to want to challenge that fact with only talking about the engine's powerband which is very surprising to me as it should be easy for anyone to understand how different tracks could use different gearing to optimize lap times - LS V8 powerband or not.
A turbo 4 will always have a much narrower usable power band than a N/A LSx engine. That's just the nature of the beast.
As such the turbo 4 will be far more sensitive to the gearing than will the LSx engine.
And this is the reason I can run as a 3 speed. Exiting a corner at 3000rpms in 3rd gear gives me 450RWTQ. Not an issue. Don't even need to think about downshifting. Even at 2500rpms it's still not not a problem with over 400RWTQ. (at 2000rpms I'm still over 350RWTQ)
With a 4000+rpm usable power band, gearing selection just isn't much of an issue.
BTW, If you want to see an overlay, it would be nice if you could get your dyno shop to get your dyno print out in a more conventional format with it being either all metric or all imperial with the scales the same for both HP and TQ for comparison purposes.
TonyG
Originally Posted by Duke
Everything is more peaky than a 6-7 liter N/A engine but that doesn't make it peaky per definition. Below is my old 3.0l 16v engine and my new engine have a broader powerband. Not what one would define as a peaky engine.
But I never stated that a smaller displacement turbo engine have as large powerband as an LS engine. Anyone can understand that's not realistic. The only point I made was that gearing is track dependent. And now both you Tony and odurandina seem to want to challenge that fact with only talking about the engine's powerband which is very surprising to me as it should be easy for anyone to understand how different tracks could use different gearing to optimize lap times - LS V8 powerband or not.
I agree that a narrower powerband is more sensitive to gearing but once again it doesn't automatically mean you cannot be quicker with another gearing. Torque by itself means nothing. You can have 1000 ft lbs at 500 rpm but it only equates to 95 hp and won't do much in terms of accelerating the car.
Let's even say you have the same torque at 2000 rpm and 3000 rpm. Say 400 ft lbs. Gearing A leaves you accelerating out of the corner at 2k rpm. Gearing B at 3 k rpm. Gearing B gives you 33% more HP to accelerate out of the corner which will give you better acceleration and lower lap times...
There is of course other aspects to take into account when choosing the right gearing for a specific track and engine but just saying that the V8 have loads of torque at 2000 rpm is a too simplifyed way of looking at gearing and, IMHO, an incomplete way of analyzing gearing vs lap times.
I can come out of a corner at 3000rpms and drive my V8 944 up the *** of a 4 liter cup car all day long exiting a slow tight turn. He's at 7000rpms, I'm at 3000rpms. He still doesn't stand a chance.
And it's because I have 450TQ at the wheels at 3000rpms.
TonyG
Originally Posted by Duke
I agree that a narrower powerband is more sensitive to gearing but once again it doesn't automatically mean you cannot be quicker with another gearing. Torque by itself means nothing. You can have 1000 ft lbs at 500 rpm but it only equates to 95 hp and won't do much in terms of accelerating the car.
Let's even say you have the same torque at 2000 rpm and 3000 rpm. Say 400 ft lbs. Gearing A leaves you accelerating out of the corner at 2k rpm. Gearing B at 3 k rpm. Gearing B gives you 33% more HP to accelerate out of the corner which will give you better acceleration and lower lap times...
There is of course other aspects to take into account when choosing the right gearing for a specific track and engine but just saying that the V8 have loads of torque at 2000 rpm is a too simplifyed way of looking at gearing and, IMHO, an incomplete way of analyzing gearing vs lap times.
I can come out of a corner at 3000rpms and drive my V8 944 up the *** of a 4 liter cup car all day long exiting a slow tight turn. He's at 7000rpms, I'm at 3000rpms. He still doesn't stand a chance.
And it's because I have 450TQ at the wheels at 3000rpms.
TonyG
I cannot comment on a 4 liter cup car engine but you do know that acceleration is determined by the average POWER in the used powerband?
My take is that the 5 speed would suit the V8 and it's 'lazy' torque. That's tongue in cheek when I say lazy but they do seem to inspire more of a leisurely driving style no disrespect intended. Clearly the early and flat tq curve is great in this respect. Having said that, driving our i4 bigger bore motors, there's no lack of tq exiting turns if wheelspin is any guide. Remember while you're at a possible 2000rpm out of a corner the only time we see 2000rpm is when unloading the car off the trailer. We're certainly never lower than a reasonable tq number on track.
09-15-2014, 10:45 PM
