Wedge Spa Summer Classic - IMSA TR8

[MadMarx]

A little video from last weekend:

 

[TuffTR250]

Very good!! Thanks for posting! I love the sound of the TR8!
Regards, Bob

 

[tr8todd]

Why is the tach in the telemetry off by 2000 rpms from the two on the dash? Kept watching this thing thinking that engine isn't reving 7000 rpms and only dropping to 5000 when shifting, then I noticed the 2 on the dash. Does that also mean the telemetry speedo is off by a similar amount or is that a GPS speedo that reads correctly. Looks correct. Looks fast! What do you estimate the HP, torque and weight of the car to be? I only ask because the only TR8s I have raced were under 200HP in race trim. Had a 300 HP one on the track but not in a race. Currently building a gutted, extensively caged TR8 now but its powered by a GM 6.2L LS3 with a 6 speed. Should make well in excess of 450 at the wheels and come in around 2500 pounds. Ought to be a fun track day car because its not going to fit under the rules of any sanctioning body I know.

 

[MadMarx]

The telemetry tach, the left tach and the shiftlight are about the same rev, maybe 100-200 rpm off.
The mechanical spare tach is indeed quite off. Just a backup tool if the others fail.
All tachs are connected to the distributor.
The shift light gets on at 7200. The telemetry video has a bit of latency so shiftlight 7200 is 7000 on the video, beacuse all you see in the video is recorded on the fly. The logging datas are more exact.

The speedo is GPS driven.
The engine is somewhere between 300-400hp.
The car is still under development but this time it went faster than before, seems I'm on the right path.

 

[tr8todd]

Would it be possible to get a peek at your front suspension. I'm tossing ideas around for mine but have not finalized anything yet. Strongly leaning towards double wishbones with aluminum spindles, steel snouts, and aluminum hubs. In the past, I've done lower heim jointed adjustable wishbones with the sway bar mounted to a bracket welded up on Rover SD1 strut tubes, with threaded collar coil over springs. This time I'm not going by any rule book so might just use all lightweight racing pieces with bigger bearings, and more adjustability. Whatever I decide, the top of the shocks are going to mount on slider brackets attached to the roll cage extensions that go thru the firewall and out to the front extensions. That will give me better camber castor adjustments than regular old camber plates. Plus stiffer front springs won't deform the strut tower tops. I love the nose you have on that car.

 

[MadMarx]

When JRT Canada went 1980 with this car into IMSA racing, GRP 44 supplied parts for body, cage and suspension.
They were not as radical in Canada and left the domes in place.
Maybe this photo is a help:

 

[tr8todd]

What you have is very similar to what I had on my SCCA ITS race car. Lower adjustable wishbone is the same, but my sway bar was different. It was straight with a splined end and arms that extended back to the strut tube. Your strut tube looks like it was custom built using sprint car snouts that have the same size inner and outer bearings. Those coil over springs are huge. From the size of those coils I'm guessing at least #700. Stiffest I ever went was #550 and I didn't like it. Most of the time I was around #400 to #450, as each corner only had to carry around #650 fully loaded. I imagine yours need to be real stiff to counteract the massive nose dive your car can generate while braking. Its hard to compare what works best when every sanctioning body has different rules. No real way of knowing what is the best setup if there is no rule book, but I'm trying to figure it out. One thing is for sure, the stock way of locating the single lower control arm with the sway bar end isn't it. Neither is running stock strut tubes and spindles with those tiny tiny wheel bearings. I hadn't thought of building my own struts, but now the gears in my head are turning. Thanks for posting that picture.

 

[MadMarx]

The springs are 600 pound ones. The lower wishbone parts are adjustable and also the top of the damper can be moved to change camber. So plenty of adjustments possible.
The dive seems not to be too bad from the photo:

And the lean seems to be okay too: