Been pondering this one ? for a while....those to whom this applies to welcome comments...
01-25-2001, 03:49 AM
#1
Been pondering this one ? for a while....those to whom this applies to welcome comments...
The AVERAGE weight of a 225TT (C and R) is in the 3200 lb range (give or take 100 lbs)...weight distribution is ~60/40 or 1920 lbs front and 1280 lbs rear. The physics of this distribution is obvious and anyone who has autoXed or tracked this car knows that very well. Now to the ?...there has been a lot of discussion about jettisoning weight in the TT...most deals with the rear section of the car...seats, ballast weights etc. and the continued comparison in weight of performance exhausts vs the OEM exhaust (the UUC exhaust really brought this to the forefront)...doesn't this 'weight loss program' in fact create more of a front to rear weight bias and thus contributes even more to the oversteer characteristics of the car? This ? is certainly not to criticize anyone who is doing what is noted, but rather and inquiry as to any thoughts on the issue.
01-25-2001, 04:34 AM
#2
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I will perform a test for you. :-)
I'll go drive like a maniac this weekend focusing on the driving characteristics. Then I'll do the same thing after I get my UUC installed.
I'll share if there is or is not a noticeable difference in the driving characteristics.
I'm not doing this to shave weight...if I notice a difference I wonder if I can put the weight back in as ballast.
I'll share if there is or is not a noticeable difference in the driving characteristics.
I'm not doing this to shave weight...if I notice a difference I wonder if I can put the weight back in as ballast.
01-25-2001, 07:49 AM
#4
There's not much that can be done on a car that is mostly street driven or...
one thats used to impress with creature comforts. And there's that constant 60/40 F/R ratio thats always there.
Swapping out an exhaust isnt going to affect that by even one percentage point... just not enough weight difference and some of that weight comes from a point forward of the rear wheels anyway. I only managed to alter my FWD F/R ratio by 1% with weight reduction alone even tho I was able to remove over 180 lbs from the cars midline back. The biggest chunk of that was the huge lead ballast used in the FWD tucked up under the rear bumper. The balance came from rear seat/backrest removal along with spare tire and all associated tire-changing tools, carpets, spare tire cover et al. You Q guys dont have the lead ballast to contend with as it's there to compensate for your rear wheel drive assembly, tho you do have a smaller/lighter steel one thats used for harmonics dampening bolted to the drivers side energy absorbing rear bumper strut. You could live without it but its a major PITA to get to and it only weighs 18lbs (but hey, it IS a dispensible 18 lbs!). If you have a torch, cut it off... its WAY easier.
Then there's spoilers. A properly designed rear spoiler creates both downforce (rear weight) at every above 25mph speed and a significantly lower coefficient of drag. But it can be radical of design and downright distasteful to others. But I'd never broken 160+mph without it nor would I had the courage to even try it.
Another thing to consider is that this car is biased heavily to the drivers side. The battery is there as is both ballast/dampener in the FWD and the dampener in the Q. You can achieve gobs of left-to-right balance by moving the battery to the FAR rear cargo area as far back as is possible. And to a lesser degree by cutting and welding a steel lowering box under the passenger side rear seat and installing the battery there. But less than 1/10 of 1% TT owners will ever do either of these mods or add a seriously effective spoiler.
Coilovers is another way to cheat the bias. You can set the car up for more rear weight or more right side weight or both. You need to do this on a set of corner scales. And you can easily achieve multiple percentage points of bias here. I got 4% off my front to rear bias and recovered 1.5% on my already light drivers side.
And finally, but MOST importantly is driver tecnique. Try and drive this car in all situations bearing in mind your weight bias. Braking/decellerating compounds the unbalance and acceleration improves on it by inertial weight displacement. Try to not brake hard or over-cook it into turns. Brake before you enter and power progressively through and out. Try to keep some acceleration through every turn and therefore weight going to the rear. Never apply the brakes or get completely off the gas within a turn unless you like Mr Tea Cups Magic Ride. Brake early and accelerate progressiveley harder into, through and out again. Its a tecnique that works with Quattro and with a huge front weight bias as on a Q/FWD TT.
Swapping out an exhaust isnt going to affect that by even one percentage point... just not enough weight difference and some of that weight comes from a point forward of the rear wheels anyway. I only managed to alter my FWD F/R ratio by 1% with weight reduction alone even tho I was able to remove over 180 lbs from the cars midline back. The biggest chunk of that was the huge lead ballast used in the FWD tucked up under the rear bumper. The balance came from rear seat/backrest removal along with spare tire and all associated tire-changing tools, carpets, spare tire cover et al. You Q guys dont have the lead ballast to contend with as it's there to compensate for your rear wheel drive assembly, tho you do have a smaller/lighter steel one thats used for harmonics dampening bolted to the drivers side energy absorbing rear bumper strut. You could live without it but its a major PITA to get to and it only weighs 18lbs (but hey, it IS a dispensible 18 lbs!). If you have a torch, cut it off... its WAY easier.
Then there's spoilers. A properly designed rear spoiler creates both downforce (rear weight) at every above 25mph speed and a significantly lower coefficient of drag. But it can be radical of design and downright distasteful to others. But I'd never broken 160+mph without it nor would I had the courage to even try it.
Another thing to consider is that this car is biased heavily to the drivers side. The battery is there as is both ballast/dampener in the FWD and the dampener in the Q. You can achieve gobs of left-to-right balance by moving the battery to the FAR rear cargo area as far back as is possible. And to a lesser degree by cutting and welding a steel lowering box under the passenger side rear seat and installing the battery there. But less than 1/10 of 1% TT owners will ever do either of these mods or add a seriously effective spoiler.
Coilovers is another way to cheat the bias. You can set the car up for more rear weight or more right side weight or both. You need to do this on a set of corner scales. And you can easily achieve multiple percentage points of bias here. I got 4% off my front to rear bias and recovered 1.5% on my already light drivers side.
And finally, but MOST importantly is driver tecnique. Try and drive this car in all situations bearing in mind your weight bias. Braking/decellerating compounds the unbalance and acceleration improves on it by inertial weight displacement. Try to not brake hard or over-cook it into turns. Brake before you enter and power progressively through and out. Try to keep some acceleration through every turn and therefore weight going to the rear. Never apply the brakes or get completely off the gas within a turn unless you like Mr Tea Cups Magic Ride. Brake early and accelerate progressiveley harder into, through and out again. Its a tecnique that works with Quattro and with a huge front weight bias as on a Q/FWD TT.
01-25-2001, 08:35 AM
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Understeer should get worse AT THE LIMIT, not oversteer...
IMO: O/S at high speeds with quick maneuvers came from unloading the rear end due to aero lift and 'tight' suspension bushings and anti-roll bars calibrated for lower speeds. Reducing rear weight with MKII suspension and spoiler might make that particular condition a little worse, but nearer the tires' cornering limits, the fronts will now be loaded even more relative to the rears, and give up first: terminal push.
Reducing weight at the front should be much more beneficial to cornering, but what can you do?
Probably the kind of weight reduction we can accomplish by removing stuff will, infact, lower lap times on a track for all of the normal reasons. You might need to 1) adjust driving style, 2)work with tire pressures, 3)change tires or spring/antiroll bars/shock combinations to maximize the gain. Again, nothing new in this.
Losing a couple of hundred lbs. is going to be most noticeable in acceleration, mainly because we often max. accelerate forward, less often max. braking, and less often actual maximum lateral acceleration.
My $.02
Reducing weight at the front should be much more beneficial to cornering, but what can you do?
Probably the kind of weight reduction we can accomplish by removing stuff will, infact, lower lap times on a track for all of the normal reasons. You might need to 1) adjust driving style, 2)work with tire pressures, 3)change tires or spring/antiroll bars/shock combinations to maximize the gain. Again, nothing new in this.
Losing a couple of hundred lbs. is going to be most noticeable in acceleration, mainly because we often max. accelerate forward, less often max. braking, and less often actual maximum lateral acceleration.
My $.02
