Track Times Post Spring Change

[NZGTRA17]

After a disappointing first outing (very slow on my local Pukekohe circuit which requires more horsepower for decent lap times as 100mph average speed is not uncommon) with my New Zealand based GTRA I decided to do some immediate rework and get the car back out to gauge impact on lap times. First outing lap times were in the 1.12.4 to 1.13.3 range depending on fuel load (tyres were "cast off" 245 front & 255 rear Hoosier R3SO4's).

Front springs were changed to 550lbs and rears to 350lbs and front bar was also set to soft. Shocks were set at setting 2 on fronts and setting 3 (firmer) on rears.

Car was a lot nicer package to race in this configuration and apart from immediately flatspotting a front tyre was consistently quicker. We eventually logged a 1.10.4 so a big improvement. Car is only clocking 115mph down the back straight and less down front straight so pleasing times for available Hp.

Problems encountered with the car so far include;

1. Front windscreen cracking,
2. Knocking geometry out of top arms (sliding over ripple strips) due stops only working one way
3. Lack of brake pedal feel
4. Steering weight to light with lack of feel (will reduce assist)
5. Boot coming loose due fasteners on leading edge popping
6. Tacho intermittent and speedo not working (sensor works but not dask reading)
7. Rear end unpredictable with apparent geometry transition causing snap oversteer in slow corners.

Next steps are strip the car over winter, go right through the chassis, modify the rollcage, replace the horizontal watts linkage with a vertical one, install a T and L engines 370 cube 600hp/500ftlb engine, TKO 600, aluminium head 3.15 diff, dry break fuel system....................and then go endurance racing if theres any mony left.

[Squerly]

Originally Posted by NZGTRA17

Next steps are strip the car over winter, go right through the chassis, modify the rollcage, replace the horizontal watts linkage with a vertical one, install a T and L engines 370 cube 600hp/500ftlb engine, TKO 600, aluminium head 3.15 diff, dry break fuel system....................and then go endurance racing if theres any mony left.

What class will you run in with a monster setup like that?

[NZGTRA17]

There are several classes over here that I can run the car in. Club saloons, Super GT, Super Sedans and endurance series. My main focus is on the endurance series which is run at 3 different tracks with a 6 hour, 4 hour and a 3 hour race. Main competition at the moment in endurance series are Porsche GT3 race cars. These are a factory built race car by porsche.

As mentioned in my post the local track that I run has 2 very fast straights and I need to be able to run around 160 mph down the main straight to compete with the Porsches, hence need for high torque & Hp. Intention is to run the engine to 6000rpm for endurance and 7500rpm for sprint racing. Given that it will have around 375ftlbs of torque from as low as 3750 rpm I figure that I can get away with the single set up for both applications.

[Squerly]

Originally Posted by NZGTRA17

There are several classes over here that I can run the car in. Club saloons, Super GT, Super Sedans and endurance series. My main focus is on the endurance series which is run at 3 different tracks with a 6 hour, 4 hour and a 3 hour race. Main competition at the moment in endurance series are Porsche GT3 race cars. These are a factory built race car by porsche.

As mentioned in my post the local track that I run has 2 very fast straights and I need to be able to run around 160 mph down the main straight to compete with the Porsches, hence need for high torque & Hp. Intention is to run the engine to 6000rpm for endurance and 7500rpm for sprint racing. Given that it will have around 375ftlbs of torque from as low as 3750 rpm I figure that I can get away with the single set up for both applications.

That's hauling ass my friend... Not sure how long an engine is going to last at those RPM's but I'm sure it'll be fun for awhile.

[NZGTRA17]

Yeah it is fast but trust me, it starts to feel slow after the first couple of hours racing. I have co-driven in the 6 hour race before in a Mazda RX7 fitted with a Quad Cam Lexus 4 litre V8. We ran that to 7500rpm for the 6 hours, well 5.5 to be precise as it ate a valve at that point.......(clipping valve on piston)!!

I am banking on T & Ls's Dart block base with forged crank, H beam rods & forged piston combo to hang together. They are confident that the engine is up for the job.

Actually I am more concerened at the moment about the body work staying on the car and would be interested to hear from any GTS runners as to how they find their cars at high speed over long distance races. I am sure good preparation will take care of most concerns but there is an awful lot of air getting in under the body work on our cars at speed just waiting to rip panels off.

Thoughts / experiences on this?

[David Eastman]

Your list of problems are dead on. I have experienced and seen most of these. As for the upper control arms Gatorac has posted about replacement controll arms that will fix that problem. I don't think the GTS guys can help you with high speed body problems as the GTS cars are plastic and the GTRAs are fiberglass.

David

[NZGTRA17]

Hi David, hmmm my car has a 90% plastic body as well. Only fibreglass is left side skirt, all of the rest is plastic. Seems this was done when the car was prepped to stand in for a Penske promotion. They also painted the car red with a broad white stripe over it.

Seems perhaps that there is not a lot of difference in the body lift off at speed between fibreglass and plastic and probably caused by a combination of amount of air that can get under the body and insufficient attachment points to hold it all down (first step I will take is to add more fastening and possibly some inside paneling to chanel air). I suspect the boot lids pop due to pressure from under the lid from all the air inside the body.

Has anybody else removed assist from the power steering and if so how did you accomplish this (by changing relief sprin etc)?