1974 13b-re Nova
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Joined: Feb 2012
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From: Dirty South
Thread Starter
Joined: Jan 2008
Posts: 438
Likes: 5
From: Ft Worth, Tx
Great day at the track today! The guys from Hennessey got a kick out of a rotary powered muscle car. Not so much at first, but when they saw it had some satchel, they thought it was pretty cool.
Since this was the first time we had taken the car to the track, and have no experience racing rotaries, we started out super conservative. On the first pass, we launched at 5000 rpm and ran 15 psi. It bogged badly which resulted in a 12.8 sec. ET. As time went on we got more agressive and made our best run launching at 6500 rpm and running 21 psi of boost which resulted in an 11.0 ET @ 126 mph with a 1.50 sec 60' time. We were pretty happy with this, and most importantly, everything and everyone came home in one piece!!!! I'm working on cropping the videos and will hopefully have them done pretty soon.
The car carries about a foot of air under the front tire when it launches, and this is with 350 lb/in springs in the front. Can't even imagine what it would do with drag springs!
On the last run of the day, I upped the launch to 6750 rpm and did a healthy burnout. It launched freakin' hard! I think it yanked both tires this time because the car headed straight for the wall! Definitely some chassis mods and rear suspension work on the way!!! We figured we were pressing our luck and called it a day.
Had something interesting happen....on one of the runs, after I upped the boost a bit, the car cut out for a fraction of a second after the 2nd-3rd and 3rd-4th shift. I looked through the data logs and saw that the closed loop boost control would see the boost fall off during the no-lift shift and would crank up the boost solenoids duty cycle to compensate. When the spark would return after the shift, the boost would spike triggering boost cut. Haltech closed loop boost control works great during regular shifting, but not so much during no-lift. They need to have the wastegate hold it's duty cycle when the no-lift is active. I'm going to suggest it to them and see if they'll add it to the next firmware rev. So I switched to open loop.....problem solved.
We brought the old man's Z06 out, but it couldn't make a clean run on street tires and spun badly on the top of 1st and 2nd. So the jury is still out on which one is faster..............
Things to do before the next track session:
- I had the no-lift set for 350ms. After watching the in-car video, I realized this is way too long. I need something more like 250ms. That ought to add a little more mph on the top end.
- I tend to short shift 1st and 2nd. Just practice and removal of the gimp factor.
- Sort out the rear suspension and up the launch at 7000 rpm. The car twists too much on the launch. I'm thinking rear sway bar and changing the right rear spring from 150 lb/in to 170lb/inch or so. I know this thing has a 1.4 60' in it.
- More boost. We stopped at 21 psi, but I've run 23-24psi on the street. We just ran out of time to up it anymore.
- Lean it out.....maybe. When Steve Kahn did the initial tune, he had it at about 12.0 afr on my gauge. Since then, we added water/meth injection and richened up the tune to about 11.4. We're leaving quite a bit of power on the table......but we did make it home in one piece.
When we get these things sorted out..........I see 10s in it's future!!
Since this was the first time we had taken the car to the track, and have no experience racing rotaries, we started out super conservative. On the first pass, we launched at 5000 rpm and ran 15 psi. It bogged badly which resulted in a 12.8 sec. ET. As time went on we got more agressive and made our best run launching at 6500 rpm and running 21 psi of boost which resulted in an 11.0 ET @ 126 mph with a 1.50 sec 60' time. We were pretty happy with this, and most importantly, everything and everyone came home in one piece!!!! I'm working on cropping the videos and will hopefully have them done pretty soon.
The car carries about a foot of air under the front tire when it launches, and this is with 350 lb/in springs in the front. Can't even imagine what it would do with drag springs!
On the last run of the day, I upped the launch to 6750 rpm and did a healthy burnout. It launched freakin' hard! I think it yanked both tires this time because the car headed straight for the wall! Definitely some chassis mods and rear suspension work on the way!!! We figured we were pressing our luck and called it a day.
Had something interesting happen....on one of the runs, after I upped the boost a bit, the car cut out for a fraction of a second after the 2nd-3rd and 3rd-4th shift. I looked through the data logs and saw that the closed loop boost control would see the boost fall off during the no-lift shift and would crank up the boost solenoids duty cycle to compensate. When the spark would return after the shift, the boost would spike triggering boost cut. Haltech closed loop boost control works great during regular shifting, but not so much during no-lift. They need to have the wastegate hold it's duty cycle when the no-lift is active. I'm going to suggest it to them and see if they'll add it to the next firmware rev. So I switched to open loop.....problem solved.
We brought the old man's Z06 out, but it couldn't make a clean run on street tires and spun badly on the top of 1st and 2nd. So the jury is still out on which one is faster..............
Things to do before the next track session:
- I had the no-lift set for 350ms. After watching the in-car video, I realized this is way too long. I need something more like 250ms. That ought to add a little more mph on the top end.
- I tend to short shift 1st and 2nd. Just practice and removal of the gimp factor.
- Sort out the rear suspension and up the launch at 7000 rpm. The car twists too much on the launch. I'm thinking rear sway bar and changing the right rear spring from 150 lb/in to 170lb/inch or so. I know this thing has a 1.4 60' in it.
- More boost. We stopped at 21 psi, but I've run 23-24psi on the street. We just ran out of time to up it anymore.
- Lean it out.....maybe. When Steve Kahn did the initial tune, he had it at about 12.0 afr on my gauge. Since then, we added water/meth injection and richened up the tune to about 11.4. We're leaving quite a bit of power on the table......but we did make it home in one piece.
When we get these things sorted out..........I see 10s in it's future!!
Thread Starter
Joined: Jan 2008
Posts: 438
Likes: 5
From: Ft Worth, Tx
Thread Starter
Joined: Jan 2008
Posts: 438
Likes: 5
From: Ft Worth, Tx
Thread Starter
Joined: Jan 2008
Posts: 438
Likes: 5
From: Ft Worth, Tx
Took down the video links and replaced them with these.............better quality.
http://www.youtube.com/watch?v=EUhz2MjT1fE
http://www.youtube.com/watch?v=fOGbyjl8k-o
http://www.youtube.com/watch?v=EUhz2MjT1fE
http://www.youtube.com/watch?v=fOGbyjl8k-o
Nick, i cant see the original video's anymore but it looked like you did not clear the waterbox before the burnout. It looked like there was still water on the tires when you rolled out after the burnout. You have to be careful about doing a burnout or scrubbing the tires while still in the water with a treaded tire. Treaded tires tend to sling a lot of water into the wheel well and it can drip back onto the tires. Roll trough the water and start the burnout on dry ground.
Thread Starter
Joined: Jan 2008
Posts: 438
Likes: 5
From: Ft Worth, Tx
Nick, i cant see the original video's anymore but it looked like you did not clear the waterbox before the burnout. It looked like there was still water on the tires when you rolled out after the burnout. You have to be careful about doing a burnout or scrubbing the tires while still in the water with a treaded tire. Treaded tires tend to sling a lot of water into the wheel well and it can drip back onto the tires. Roll trough the water and start the burnout on dry ground.
Honestly, I was so concerned about finding the right launch RPM, hitting the no-lift shifts, easing into boost, EGTs, and why the closed loop was spiking, that I never even thought about shocks. The rear shocks were only set to 5 clicks firmness and the front to 0 clicks. If I would have upped the rear shocks to about 10 clicks, and the front to 4 clicks or so, the car would have settled down a bit on the launch a bit and been easier to control.
Lots of things could have been much better........but they could have been a lot worse too. I'm guessing 10.6 @ 131 at 25-26 psi with a 6750 rpm launch........after I get my **** together.