Big Bend Open Road Race Report

#1
Several members have been by to checkout my car, I think at least a couple have placed an order. Those that have been by know that I was planning on running BBORR, so thought I would share the results...

FYI, my car has a stock LS-7 and V10 Graz.

For those of you not familiar with Open Road Racing; It is on public roads, closed to the public. Classes are timed (winner closest to correct time for their speed), except the Unlimited Class which is what you would expect. Each class has a 'tech' speed, which you cannot exceed (radar on course so you will get DQ'd and put on the not welcome list). It takes years to work your way up to Unlimited, and rightly so. We don't need some yahoo getting himself killed and ruining things for everyone. You can choose to run with/without a navigator/co-driver (you can split driving if you would like). Most choose to run with a navigator. Big Bend is probably the most challenging of the bunch in the USA because the Sanderson end of the course is windy and hilly. So while top speeds tend to be 210-215 for unlimited cars, the winning speed is usually 170s. More info for Big Bend at www.bborr.org

While I can't call my car 'finished', I did have it on track in February, and ran BBORR a couple of weeks ago.

While out at MSR Crescent, I did identify several issues. They boiled down primarily to:

- Bad voltage regulator (too much voltage)
- Needing MUCH stronger springs front and back
- Needing downforce on the rear

To get ready for Big Bend, we replaced alternator, battery (fried), headlights (fried), installed the rear wing, front fender vents, moved to 850f/900r springs and trimmed the fenders to better clear the tires.

Car passed tech with no issues - the factory 4 point cage is good for Grand Sport (168 tech speed). Past that, the car will need a full cage with a steel inner roof. As a purpose built car, we needed a full fire system to run Grand Sport (but a Corvette does not, go figure).

For practice, officials close off a short (9-10 miles) section of a different highway for short periods of time and let a limited number of cars run down and back before re-opening the road and letting traffic through. At Big Bend, the practice course is reasonably challenging and seems to eat one car a year from the higher classes.

In practice the car felt much better than it had on track. Could have used a bit more caster, but tracked reasonably well and the additional downforce had it planted in the corners and stopped the tires from spinning in the upper gears. Ran it up to about 6800rpm in 6th. Still needs stiffer springs, but now that is probably because of the downforce. We have the front lift so had to move to 2.25" springs, but now we have a good selection available. If you want to move to the smaller diameter springs, PM me and I will share what I learned.

We did have some motor issues and struggled for days to get to the bottom of them. Finally did about midnight before the race. Turned out the fuel pump circuit breakers were toast. The original high voltage could have caused the issues, or engine compartment heat, or ???. But they are toast. Ended up re-wiring around them. For anyone interested, these are the breakers supplied with Summit brand kits and are rated at 30 amps. We have 3 pumps (one tank to surge and two pressure), all the circuit breakers fell apart when removed.

On race day, we had some clutch slippage which we had never seen before and had to baby it up to 6000rpm in 6th. Was 10 miles in cruising at 6000rpm when the motor lost a bit of power and then grenaded. Smoke and fire followed immediately but the fire was out by the time we got the car stopped. When the motor let go the cabin filled with smoke, which surprised me. We were running w/o side windows, but do have the bulkhead and the side 'tunnels' well sealed. Thankfully we were on a straight, so it was just a matter of holding it straight until the yellow line re-appeared.

We coasted to a gate marshal, so had shade, food and water while watching the rest of the cars go by. The officials said it was pretty spectacular, but no video.

The engine is a GM Performance LS-7 with no mods (other than flipping the intake). Since it took quite a while to get the car done, I've had it for a while. But first started the engine about 6 months ago. I am going to see what GM says about it. There is a whole in the block near cylinders 3/5 just at the oil pan. Oil pressure, water temp and MIL were all good when it let go. Had a few hundred miles on it and I don't think it had ever hit the rev-limiter.

In any case, I will have to do something about the Graz gearing as RPMs are through the roof unnecessarily. While the low 1st is OK for the parking lot, it is useless otherwise. I find I only really need 3rd and 6th gears for normal driving. For spirited driving 2-3-4-6 are the appropriate shifts. Still contemplating what to do about this.

Car is still in the trailer. I managed to crumble a piston in our Lotus this week so I feel obligated to help my son fix it. The SLC will probably sit for a couple of weeks before I tear into it.
 
#2
A few pictures...

In line for practice (too many Corvettes)


At a charity event in Ft Stockton (you can drive a non-street car around town all week as long as you don't speed)


At the marshal stand, the Vet in the background was doing 206 when it went by
 
#3
Frank: Sorry to hear of your bad luck at BBORR, but I'll bet it was fun while it lasted. I was a course marshal at the event a couple of years back, stationed near the Ft. Stockton end just before the road went into the hills. It was hard to judge the speed of the cars as they were approaching, but I could hear them coming in both directions long before I could see them.

Our Corvette club sends a dozen or so cars every year to the race. In fact, Dan and Debbie Leimbach won the same class you were in with a winning time of 3/1000 of a second deviation over the entire 118-mile course. It is hard to compete against those times, but I would expect that the rush is more in the drive than the winning time.

I will check with the Club members to see if they have photos of your car, but in the meantime there are some on this site: https://www.flickr.com/photos/zombieite/25945824933/in/photostream/

The official BBORR photos haven't been posted yet. I wish I had been there this year to see an SLC run. Best of luck!
John
 
#4
John,

Thanks. We really don't worry about the times. There are guys with $15k in electronics doing that. And others that are real good and the last couple of 10ths for them are probably luck.

We've got a $25 GPS unit and a stop watch. Our goal (not reached), is to be within 2 seconds and to work our way up to unlimited. We enjoy the whole week out there. That is what is important.
 

Cam

Active Member
#5
That's really unfortunate to hear about your engine issues. I think I've heard some complaints about crate ls7 valves but this sounds like it's possibly con rod or piston related. Have you had the engine tuned or were you using the factory ECU and maps?

I'm interested to hear more comments regarding the Graz v10. I'm leaning toward using this for my build and I was thinking it would be an acceptable option for a 99% street car. I don't plan on doing any top speed runs but I am somewhat concerned about spinning the engine at 3000 rpm for extended periods - say during a cross country road trip should I do one. For typical 0-60 around town driving do you feel the Graz v10 or 8 offering would be a wise choice? There aren't too many posters who have operational Graz transaxles right now so would appreciate your insight.
 

John

Silver Supporter
#6
Frank.
Thanks for the BBOR report. Sounds like a really fun event.
Sucks about the engine though. Hope GM makes it right for you.
John
 
#8
Cam,

I thought the Graz would be fine and that down the road I'd need a drop gear set. But after putting some time on it I am reconsidering. While my car will be street legal, it is not titled/licensed yet. That said, I do have a couple hundred street miles on it.

Gearing seems to be a very subjective topic, so please don't anyone take my opinions to be anything other than that.

For me I'd rather lug an engine that spin it. I am usually not in a hurry, so in a Viper or Vett I could drive all day long without ever getting close to 3,000rpm. Even in our Evora with the close ratio box I usually only get to 3,000rpm unless in 6th on the highway.

The V10 Graz has the engine spinning faster than the Evora - and there is no way around it. Given the LS-7 has 150hp more and the car is 500lbs lighter, it makes for less than ideal situation. The Graz gears are close enough together than you either skip gears, or loose the advantages of big cubic inches and a wide power band.

In 3rd gear, you can leave a stop light with just a hint of throttle.

On a typical track, all these items are non-issues. 1st is good for the pits and at most tracks you will just use 3rd-4th or 4th-5th depending on the track. And of course the Graz is probably bullet proof in and SLC with any reasonable amount of HP.
 

Cam

Active Member
#10
Appreciate your feedback on the Graz! On my 400 crank hp/4000lb car I hit 3krpm constantly but there's 7 speeds and I'm usually in 6 or 7 at normal speed (Audi dsg so shifting is easy;)). When driven in anger I redline frequently. With 125 more hp and 1500 fewer pounds I expect the driving experience is going to be very different. Trying to wrap my head around what the power train should "feel" like given these factors.

It boggles my mind that you can leave in third without stalling the engine.
 
#11
It boggles my mind that you can leave in third without stalling the engine.
If you compare ratios, I expect you will see that the Graz 3rd is roughly equivalent to the Viper 1st. With just a bit less TQ, but 1000lbs less curb weight it makes perfect sense.

There are gear options for the Graz. From the $2k drop gear set (not enough change for me), to full replacement gear sets (contact Dallas performance). And it is a rock solid transmission. So it does have a lot going for it.

Maybe I should match the engine to the gears and just try to shoehorn in a 2JZ, or go Rotary.
 
#12
Thank you for your report! This sounds like a road rally on steroids!

Can you show details on how you attached your rear spoiler to the car? Does it mount off the gearbox and tilt back before opening the rear clip?

Driving a non-licensed car on the streets had to be an odd feeling. Not to mention the speeds you were hitting! What top speed is the Graz supposed to hit? I have the V8 Graz (not running yet) and I suspect it's around 185. Is the V10 much higher?

A.J.
 
#13
I will start a thread on the wing mount in a couple of days. The car is still in the trailer. The SLCs garage spot was stolen by my son's Sprint Car. His car is finished up so we will play musical chairs with the cars this weekend.

6th with the V8 and V10 Graz's are similar. I saw 150 on GPS at a steady 6000rpm. So 7200 rpm is about 180. With a more reasonable redline and you are going to see considerably less. But driving down the highway in 6th with the shift lights blinking is a bit un-nerving! Keep in mind these are real numbers but are aporoximate as the gauges just get a quick once over routinely.
 
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