Acropora

There or 335 r compounds

markski

no not in my case.... I have the fuel system(dual pumps placed in the front where diff goes. there are pros and cons for doing so.. Mind you I am in chicago in mid to hight 30s.. I don't think anyone is expecting meto hook up with a 700 rwhp@.9 bars car in these conditions....

markski

I have lag but becasue my engine is so efficient.... it would probably give alot of cars a run for there money even without the turbos...
here is the difference.. and Jean may chime in.... when I asked about my No lag feel( I asked my tuner- Todd Knighton).
He said that becasue the engine is so efficient and more importantly because I have cario cam timing.... unlike the TTs with stock heads that at idle have 30 degrees of timing and then its ON or OFF.... my heads and cams MOVE with Throttle position, RPMS, and engine load... thus producing immense amount of TQ... and that is why you don't feel the lag. KPG drove my car and was shocked... so am I... that is why this car is so special...
best,
markski
ps. here is a pic I am proud off...

Jean

Bill, at 6200RPM, Mark's 4th gear thrust curve crosses the third gear power curve, meaning if he had shifted at 6200RPMs, the torque available to the wheels would have been greater for a while than if he stayed in third gear.

How it compares to RUF...I don't have many RUFs on my database, the fastest RUF I have seen todate is Guy's GT2, which was in the 8s while lighter than Mark's car, I think Mark would be in the high 6s-low 7s with 7200RPMs and 1.1 Bar, or less, since these runs are done at 0.9 Bar and traction loss. Check out the advantage it starts to have on KPGs' at 4600RPMs or so, and KPG did it in the 7s.

Certainly a turbo car has lag, and a high performance one even more, however it is very clear it does not have much for the sort of power it has..I htink what Markski was trying to say is that this car has much more off boost torque than a typical tuned TT engine, since it benefits from much better (efficient) heads and exhaust.

On the track the CGT will beat it hands down, but for different reasons.

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..?

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!

TB993tt

One of the main differences between the AWD and 2WD IMO is that the AWD, through its heavy torque tube and front differential saps a good amount of torque from the engine and reduces the torque to the rear tyres, this is the reason one appears to get better traction with AWD because there is much less torque going through the rear tyres.
My guesstimate is that for an engine producing 700NM @ 4500rpm on a 2WD one would get 640NM hitting the rear tyres only.

For AWD 55NM will be lost through the transfer to the front reducing the torque to the rear tyres to under 600NM much less violent and hence more chance of traction.

With real torque the point is moot, when my car was producing 757NM in its first iteration in 2000 the rear tyres lit up almost as violently as they do now and that was with the AWD fully functional !!

Dknebes

I wanted to add to this post. When I was running my stock dif with 600hp my car would jump one lane when it came on boost but when I went for more hp I also switched to a Quaife dif which gives 50/50 to the rear and with 733rwhp my car will hook up faster and pull perfectly straight even with tire spin. I am not running the hp that some of these monsters are running but with 315x30-18 mpsc my car with Florida temps will hook up even in second gear with controlled wheel spin. I have to say when we have a cool morning and my car has cool charges and cold tires second gear will let loose but the car stays straight and holds straight in and this is with a 89 930 with coil overs.

TB993tt

Dknebes
I think most of us are also running LSDs, mine is a 45/65 jobbie.
The very cold conditions are a huge factor in the traction problems being discussed from 3 angles:
Colder summer tyres have cr&p grip
cold/moist roads ditto
cold dense air increases engine torque

The other factor which you have to your advantage and Jean and I also have to some extent is the relative light weight of the whole car, this obviously gives less inertia to overcome from the standing start - it all helps

Dknebes

I did have a stock LSD that came with the 89 930. When compare a 45/65 LSD to a 50/50 Quaife LSD the difference is when the tires begin breaking loose, with a mechanical 50/50 it is instant and the car pulls straight with a 45/65 the tires do not start to spin at the same time causing the rear to kick out and launch the car into the next lane where it is now pointed.

bb993tt

Jean,

Is this the type of LSD someone contemplating the conversion to 2WD would need?

Jean

Brian

I think you cannot go wrong with the Quaife, the Guard or the Posrche Motorsport, they all do the right thing. From what I hear the Guard is the most solid. I have driven my car for a while with the stock LSD and seen very often 100 meter powerslides coming out of turns at full throttle on the track, fun, but dangerous. It is perfectly drivable on the street with the stock one however, unless you are planning to go WOT, which will be rarely the case I guess?

TB993tt

Is the difference that great with a 50/50 to a 45/65. AFAIK the second number denotes the lock up when slowing down with the first the % lock when driven -how much difference would there be when spinning the wheels in a straight line between a 45% and a 50% ?

Is it not the fact that one is rarely 100% straight which causes the tail slides or does the 45% encourage the tail to step out in one direction

Acropora

Per Steve Weiner at rennsportsystems.com an LSD is great upgrade if you like to track your car. It's also kind of neat hearing the inside wheel slipping when you go around tight corners as it tries to go the same speed as the outside wheel.

Jean

That's correct TB, 65 would be on deceleration. I think the confusion is because the older gearboxes had clutch type differentials rather than torque sensing which is what the Motorsports one is as well, like the Guard and the Quaife. I am sure the three of them are identical when it comes to perofrmance (grip) 45 or 50% on acceleration will not make that big of a difference. More than that and the car will be undrivable on the street, and ultimately dangerous on wet pavement.

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.