115 mph traps on conservative set-up.
Thread Starter
Melting Slicks
Joined: Aug 2003
Posts: 3,403
Likes: 397
From: Lakeville MI
115 mph traps on conservative set-up.
Yesterday had a chance to test some things at the track. New 27" tall tires all around. Riken Raptor ZRs in 255/50ZR17.
I now have 3" of ground clearance under my primary tubes. Yippee!
I plan to try 27" Mickey Thompson 295/45R17 in the future, so the Raptors gave me an idea how a 27" tire would affect the car.
The taller tires knocked my effective gear ratio down to about 3.46. As a result rpm and boost were both reduced with the current 3.12" blower and stock crank pulleys.
The 115 mph traps occurred at about 5400 rpm in 4th and maybe 6-7 psi. MAF flow at 360 gm/sec was well below the peak at this rpm, LV8 (extended) was approx 300. Definitely leaving some power on the table. As pullied, 8-9 psi is typical above 6,000 rpm.
My intercooler performed reasonably well. Each run started with a little heat soak resulting in 80 F charge air temps at the 60 F ambient conditions.
At the end of the runs, charge air temps (measured at the MAF) had risen from 80 F to 109-114 degrees at 115 mph with some run to run variation.
A 30 degree rise is pretty consistent with what I have seen on the street in 3rd gear pulls (but without the initial heat soak), so no real suprises here. I start to pull timing with charge temperatures above 124 F, so no timing was pulled during these runs.
No knock with 30 degrees advance, Peak MAF flow was in the vicinity of 420 gm/sec. Not bad with the 110+ degree charge temps. On cold days, I see 470-480 gm/sec with charge temps in the 50-60F range.
I didn't play much with fueling or spark. Target AFR was kept in the 11.85-11.6 range and varied vs load. Plugs were running clean at these targets, but observers noted some black smoke out the pipes.
Track wasn't really working until 4th gear, I was plagued by wheel spin and axle hop in both 2nd and 3rd gears on my best pass.
Time to put the 2.93" pulley back on to compensate for the reduced rpm as a result of the tire/ratio change. Mph should improve. We'll see about traction.
2.93" pulley is back on. Reduced rev-limit to 6,000 rpm. Car is now making 9 psi just before the rev-limit hits.
Update: In this mornings cooler air, peak flow was up to 460 gm/sec at 6,000 rpm with 68F charge air temperature. My extended LV8 signal maxed at 382.5 and the injector duty cycle was up over 60% for the first time with the same tune. Its certainly making more power now than it did on Saturday with less rpm. Should be a bit faster.
Lovin' this cold air, in Today's 35F ambient, peak flow was up to 478 gm/sec at 5,800 rpm with 50F charge air temperature. Just goes to show how much effect changing conditions can have.
I now have 3" of ground clearance under my primary tubes. Yippee!
I plan to try 27" Mickey Thompson 295/45R17 in the future, so the Raptors gave me an idea how a 27" tire would affect the car.
The taller tires knocked my effective gear ratio down to about 3.46. As a result rpm and boost were both reduced with the current 3.12" blower and stock crank pulleys.
The 115 mph traps occurred at about 5400 rpm in 4th and maybe 6-7 psi. MAF flow at 360 gm/sec was well below the peak at this rpm, LV8 (extended) was approx 300. Definitely leaving some power on the table. As pullied, 8-9 psi is typical above 6,000 rpm.
My intercooler performed reasonably well. Each run started with a little heat soak resulting in 80 F charge air temps at the 60 F ambient conditions.
At the end of the runs, charge air temps (measured at the MAF) had risen from 80 F to 109-114 degrees at 115 mph with some run to run variation.
A 30 degree rise is pretty consistent with what I have seen on the street in 3rd gear pulls (but without the initial heat soak), so no real suprises here. I start to pull timing with charge temperatures above 124 F, so no timing was pulled during these runs.
No knock with 30 degrees advance, Peak MAF flow was in the vicinity of 420 gm/sec. Not bad with the 110+ degree charge temps. On cold days, I see 470-480 gm/sec with charge temps in the 50-60F range.
I didn't play much with fueling or spark. Target AFR was kept in the 11.85-11.6 range and varied vs load. Plugs were running clean at these targets, but observers noted some black smoke out the pipes.
Track wasn't really working until 4th gear, I was plagued by wheel spin and axle hop in both 2nd and 3rd gears on my best pass.
Time to put the 2.93" pulley back on to compensate for the reduced rpm as a result of the tire/ratio change. Mph should improve. We'll see about traction.
2.93" pulley is back on. Reduced rev-limit to 6,000 rpm. Car is now making 9 psi just before the rev-limit hits.
Update: In this mornings cooler air, peak flow was up to 460 gm/sec at 6,000 rpm with 68F charge air temperature. My extended LV8 signal maxed at 382.5 and the injector duty cycle was up over 60% for the first time with the same tune. Its certainly making more power now than it did on Saturday with less rpm. Should be a bit faster.
Lovin' this cold air, in Today's 35F ambient, peak flow was up to 478 gm/sec at 5,800 rpm with 50F charge air temperature. Just goes to show how much effect changing conditions can have.
Last edited by tequilaboy; Oct 19, 2010 at 06:14 PM.
Thread Starter
Melting Slicks
Joined: Aug 2003
Posts: 3,403
Likes: 397
From: Lakeville MI
Went back to the track again today...Still trapping 115 mph, but into a big headwind this time.
My buddies blown SRT8 challenger was down by 2-4 mph as compared to last time out. He did go 11.97 at 117 mph on new Hoosier 28x10x17 slicks, but also had some runs in the low 12 second range down around 114 mph. Nice tire (and car), in any event.
Other guys at the track commented that their traps were off by about 3 mph, so it looks like I gained something by standing still.
My air flow was up by about 5% through the traps. Charge temps were also little cooler at 106 F, but still influenced by heat soak as compared to running on the street. Speed at the 1/8 was up, with 89 mph. All indications of increased power. Except for the 115 mph trap speed.
I managed a couple 2.0x 60s on the 255/50R17 Riken Raptors with about 60% throttle and short shifting first, but still spun most of 2nd resulting in a 13.0 at 115 mph. Not bad for a cheap street tire.
Due to a previous EST error, 6 degrees was somehow being added to my spark advance. A datalog from today showed 35.86 degrees advance instead of the intended 29.88 degrees. It didn't knock much, but likely was more advance than optimum.
My buddies blown SRT8 challenger was down by 2-4 mph as compared to last time out. He did go 11.97 at 117 mph on new Hoosier 28x10x17 slicks, but also had some runs in the low 12 second range down around 114 mph. Nice tire (and car), in any event.
Other guys at the track commented that their traps were off by about 3 mph, so it looks like I gained something by standing still.
My air flow was up by about 5% through the traps. Charge temps were also little cooler at 106 F, but still influenced by heat soak as compared to running on the street. Speed at the 1/8 was up, with 89 mph. All indications of increased power. Except for the 115 mph trap speed.
I managed a couple 2.0x 60s on the 255/50R17 Riken Raptors with about 60% throttle and short shifting first, but still spun most of 2nd resulting in a 13.0 at 115 mph. Not bad for a cheap street tire.
Due to a previous EST error, 6 degrees was somehow being added to my spark advance. A datalog from today showed 35.86 degrees advance instead of the intended 29.88 degrees. It didn't knock much, but likely was more advance than optimum.
Thread Starter
Melting Slicks
Joined: Aug 2003
Posts: 3,403
Likes: 397
From: Lakeville MI
I think I might have to try some of those Hoosiers. Now that there's a real 17" drag slick available, I'm not sure I want to bother with DRs.
https://www.hoosiertire.com/pb60909.htm
Found the spark bug...It was due a change that I had recently made to rescale the min LV8 input value for the main spark table. This messed up the table indexing. Easy fix.
https://www.hoosiertire.com/pb60909.htm
Found the spark bug...It was due a change that I had recently made to rescale the min LV8 input value for the main spark table. This messed up the table indexing. Easy fix.
