60-130 MPH: New performance measurement!
01-16-2007, 02:58 PM
#1051
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[.
JJayB, it is very surprising to know that you are having lag issues with your K16 hybrids on the track! Would you say it is rather the torque curve of our turbo motors that makes it loose to a Viper on the track, rather than lag..?[/QUOTE]
Jean,
I haven't lost to Viper yet,
due to the rather good throttle response the K16's have. With that said, I'm sure their out there. The 3.8 has helped with the torque curve out of the slower corners until the turbos spool up. Yes, I would agree its more of a matter of the torque curve. I have run against some single turbo Supra's that I have flat left for dead, until they spool up there is too much ground for them to make up. I guess that's the point I was trying to make. 
JJayB, it is very surprising to know that you are having lag issues with your K16 hybrids on the track! Would you say it is rather the torque curve of our turbo motors that makes it loose to a Viper on the track, rather than lag..?[/QUOTE]
Jean,
I haven't lost to Viper yet,
due to the rather good throttle response the K16's have. With that said, I'm sure their out there. The 3.8 has helped with the torque curve out of the slower corners until the turbos spool up. Yes, I would agree its more of a matter of the torque curve. I have run against some single turbo Supra's that I have flat left for dead, until they spool up there is too much ground for them to make up. I guess that's the point I was trying to make.
01-16-2007, 03:02 PM
#1052
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Originally Posted by Red9
Jean the question I would ask is " what other cars do that to you(JJayB)? The Vipers have enormous torque that could make you feel like that.What about Cupcars or RS's? How do they compare?The other issue is that if the revs drop below the torque characteristics of the engine it will create "lag". Imight add if the same issue arose with a Cupcar-- well-it aint turbo lag!
I'll try and post a video of what my car looks like from a GT3 cup car driving at 7/10's.
01-16-2007, 03:31 PM
#1053
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Originally Posted by NineMeister
The Quaiffe diff is a torque sensing device and never fully locks the diff which explains why it drives differently to the Salisbury plate type diff. The Torsen diffs have a "bias ratio", which is basically the ratio of how much more torque can be transmitted to one side in comparison to the other, as far as I can work out from the gear angles the Quaiffe diff bias ratio is around 2.5:1. I believe that it is the constant sense/adjust function of the Torsen which allows it to maintain a straight course whilst accelerating hard.
The downside to the Torsen is that if you lift a tyre off the ground whilst under hard load, like over a kerb on track for example, the tyre on the road momentarily loses driving torque (2.5 x zero = zero), for this reason the first choice for track use would normally be the Salisbury type differential. I have driven cars with both and would say that for road use the Torsen takes a lot of beating, and on short circuits with uneven surfaces (like the hillclimbs I do) and in the wet it has its advantages, but for flat out use on an open circuit I much prefer a Salisbury.
For fast circuits I use a motorsport version of the Salisbury diff with a 50/80 or 80/80 locking factor but this is definitely not suitable for road use, even with just 400-450hp.
The downside to the Torsen is that if you lift a tyre off the ground whilst under hard load, like over a kerb on track for example, the tyre on the road momentarily loses driving torque (2.5 x zero = zero), for this reason the first choice for track use would normally be the Salisbury type differential. I have driven cars with both and would say that for road use the Torsen takes a lot of beating, and on short circuits with uneven surfaces (like the hillclimbs I do) and in the wet it has its advantages, but for flat out use on an open circuit I much prefer a Salisbury.
For fast circuits I use a motorsport version of the Salisbury diff with a 50/80 or 80/80 locking factor but this is definitely not suitable for road use, even with just 400-450hp.
01-17-2007, 05:02 AM
#1055
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A Quaiffe diff works in the same way as a Torsen. Its all to do with the pressure angle on the gears! However, the important thing is how they drive. My experience is much more circuit biased than road but I am in complete agreement with the Ninemeister! The Quaiffe diff is a lot softer and allows more relative speed difference between one driven wheel and the other. Again, as Colin said, if you lift the inside driven wheel away from the road the diff becomes open and the unloaded wheel will spin. A "plated" diff, (Porsche motorsports ZF or GT gears equiviliant etc) controls the relative wheel speeds more carefully. They can be set with different preloads and set with different ramp angles, therefore altering their lock up characteristics and hence the way the car drives. In my opinion use a plated ZF for the circuit, use a Quaiffe for the road. You will have less understeer with the Quaiffe but ultimately it is less controllable hence my choice for the track. However, there is little doubt that going from an open diff to a slipper of any sort will alter the handling of the car big time.
Enjoy but be careful!
Richard.
Enjoy but be careful!
Richard.
01-17-2007, 05:32 AM
#1056
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Thanks Jean.
I assume that you mean "push" understeer, like you would feel on a large roundabout in the wet, rather than speed induced understeer that you would get on track? In my experience both types of diff will increase the available grip of the rear axle and allow the car to push understeer if the circumstances are appropriate, however the Torsen is a lot more progressive in its operation, so the effect at low speed is much more progressive.
At the other end of the scale it is the ability of the Salisbury diff to quickly lock the rear end and transfer all the torque to the gripping wheel when the other wheel slips which makes it more capable of inducing power oversteer on the exit of the bend. In contrast the Torsen can only transfer 2.5 to 3 x times the grip of the slipping wheel, so the available torque on the gripping wheel may not be 100% of the available torque and hence - as the slipping wheel loses more grip - may not be enough to break traction of the driving wheel.
The other side of the coin which Toby touched on first is the lift-off locking factor of the Salisbury diff. It is well known that Porsche used a 20/100 diff in the 964RS and 965 turbo road cars and use 100% lock on lift off to stabilise the rear end, a feature which I like because it allows you to easily lift-off oversteer the RS into bends under braking. This is fine in the 964 chassis, but in the 993 the rear subframe and multi-link kinematic geometry I am going to guess that they do not cope well with such severe loadings, which probably explains why a 50/80 Motorsport diff in the 993RS chassis on the road tied the rear end up in knots. For the 993 chassis on the road I would think that somewhere around 40/60 would be as far as you would want to go.
Originally Posted by phelix
Does a torsen diff induce as much understeer as a Salisbury diff?
At the other end of the scale it is the ability of the Salisbury diff to quickly lock the rear end and transfer all the torque to the gripping wheel when the other wheel slips which makes it more capable of inducing power oversteer on the exit of the bend. In contrast the Torsen can only transfer 2.5 to 3 x times the grip of the slipping wheel, so the available torque on the gripping wheel may not be 100% of the available torque and hence - as the slipping wheel loses more grip - may not be enough to break traction of the driving wheel.
The other side of the coin which Toby touched on first is the lift-off locking factor of the Salisbury diff. It is well known that Porsche used a 20/100 diff in the 964RS and 965 turbo road cars and use 100% lock on lift off to stabilise the rear end, a feature which I like because it allows you to easily lift-off oversteer the RS into bends under braking. This is fine in the 964 chassis, but in the 993 the rear subframe and multi-link kinematic geometry I am going to guess that they do not cope well with such severe loadings, which probably explains why a 50/80 Motorsport diff in the 993RS chassis on the road tied the rear end up in knots. For the 993 chassis on the road I would think that somewhere around 40/60 would be as far as you would want to go.
01-17-2007, 10:25 AM
#1057
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Maybe whats needed is a 964 C4 style electronically controlled diff.With the appropriate inputs/software that would give total control .Or go the factory race route and weld the diff up !!!
Colin, Know what you mean about the 993 rear. First time I put a 993 on a chassis dyno I was amazed at the rear geometry variation with power . Lots of bushes to harden up !
Geoff
Colin, Know what you mean about the 993 rear. First time I put a 993 on a chassis dyno I was amazed at the rear geometry variation with power . Lots of bushes to harden up !
Geoff
01-29-2007, 04:45 PM
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This tread is a discussion in depth of situations with different tuned engines. But, it seems that everybody forgot to discuss the engines torque. My understanding of engines is somehow limited, but a tractor can pull whatever with a 150Hp engine, a 500Hp Porsche will be unable to take same load.
01-29-2007, 05:06 PM
#1059
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ClaesM,
There is much confusion over the relationship between HP, torque, gear ratios and RPMs. It is a subject worthy of its own thread, rather then clutter up this one more. This has been discussed in the past, but I would ask that you repost your question as a new topic.
There is much confusion over the relationship between HP, torque, gear ratios and RPMs. It is a subject worthy of its own thread, rather then clutter up this one more. This has been discussed in the past, but I would ask that you repost your question as a new topic.
01-29-2007, 07:26 PM
#1061
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depending on the engine HP x 1,3-1,5= NM (torque)
a Porsche with 500 HP can pull more than a tractor with 150 HP (in 1st gear) lol!
Konstantin
a Porsche with 500 HP can pull more than a tractor with 150 HP (in 1st gear) lol!
Konstantin
01-30-2007, 02:33 AM
#1062
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Originally Posted by Konstantin
a Porsche with 500 HP can pull more than a tractor with 150 HP (in 1st gear) lol!
Konstantin
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01-30-2007, 03:53 AM
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Ca993Twin
Well, I dont think I am cluttering up the discussion. Horsepower ratings in the area 600-700HP is not the only way to get low 60-130 mph figures. I think many Porsche owners would rather benefit from cars with lower hp but more torque and better 4WD grip. I read in the previous posts that many cars seems quite equal in performance even if they have 550 or 650HP. Did anyone asked for torque / rpm diagams?
Konstantin
The formula you posted is not valid for all engines...
Well, I dont think I am cluttering up the discussion. Horsepower ratings in the area 600-700HP is not the only way to get low 60-130 mph figures. I think many Porsche owners would rather benefit from cars with lower hp but more torque and better 4WD grip. I read in the previous posts that many cars seems quite equal in performance even if they have 550 or 650HP. Did anyone asked for torque / rpm diagams?
Konstantin
The formula you posted is not valid for all engines...
01-30-2007, 05:50 AM
#1064
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Originally Posted by ClaesM
Ca993Twin
Well, I dont think I am cluttering up the discussion. Horsepower ratings in the area 600-700HP is not the only way to get low 60-130 mph figures. I think many Porsche owners would rather benefit from cars with lower hp but more torque and better 4WD grip. I read in the previous posts that many cars seems quite equal in performance even if they have 550 or 650HP. Did anyone asked for torque / rpm diagams?
Konstantin
The formula you posted is not valid for all engines...
Well, I dont think I am cluttering up the discussion. Horsepower ratings in the area 600-700HP is not the only way to get low 60-130 mph figures. I think many Porsche owners would rather benefit from cars with lower hp but more torque and better 4WD grip. I read in the previous posts that many cars seems quite equal in performance even if they have 550 or 650HP. Did anyone asked for torque / rpm diagams?
Konstantin
The formula you posted is not valid for all engines...
A light hearted display of torque in relation to 60-130 is here:https://rennlist.com/forums/showthre...ighlight=world
Or torque curve relating to 60-130 here:https://rennlist.com/forums/showpost...&postcount=972
01-31-2007, 04:34 AM
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Originally Posted by ClaesM
Ca993Twin
Well, I dont think I am cluttering up the discussion. Horsepower ratings in the area 600-700HP is not the only way to get low 60-130 mph figures. I think many Porsche owners would rather benefit from cars with lower hp but more torque and better 4WD grip. I read in the previous posts that many cars seems quite equal in performance even if they have 550 or 650HP. Did anyone asked for torque / rpm diagams?
Konstantin
The formula you posted is not valid for all engines...
Well, I dont think I am cluttering up the discussion. Horsepower ratings in the area 600-700HP is not the only way to get low 60-130 mph figures. I think many Porsche owners would rather benefit from cars with lower hp but more torque and better 4WD grip. I read in the previous posts that many cars seems quite equal in performance even if they have 550 or 650HP. Did anyone asked for torque / rpm diagams?
Konstantin
The formula you posted is not valid for all engines...
Power = 2 x PI x N (speed) x T (torque)
In metric units, power in watts, torque in Nm and N in Hz (revs per second)
In simplistic terms Claes, the 993 turbo engine is heat and cylinder pressure limited, so it is not possible to make more than a constant 800Nm without risk of damage to the engine. Most of the very fast aircooled cars running here are already at this level (TB, Jean, etc) therefore the only way to increase their performance is to improve the "area under the curve" by spreading the same peak torque over a wider rpm range, which is what most high level tuners always aspire to.