Boost and timing at altitude question.
Boost and timing at altitude question. I ran a test pass on the street last night. I have my bleeder turned all the way in so I am making as much boost as I can with the WG springs I have in the car. I will need to swap springs to run any more boost. Not a big job but a job.
This is the same set up I ran on my NHRA test passes @ 146-148 mph trap speed with a lousy 60 ft. in 6500 ft DA.
The data log shows a maximum of 17 psi boost,(most of the run it is much less) 11.2 AFR and 11.5 degrees of timing at the max boost level. There was no knock present on both pulls. Car ran clean. I am running 91 octane (Premium fuel at our elevation) and meth injection) IAT were 95 degrees.
The combo is a forged 408 with at S400-Hp88 turbo. The car weighs about 2400 lbs without me in it. Powerglide car with 3,73 gears and 32" tall slicks.I am at 4500 ft actual elevation and the DA is usually close to 7000 ft.
I am planning on going to the track here in a week or two and would like to get the boost up to the 20 lb range with the meth. I have the timing on the table down to around 10 degrees at the 20 psi boost level to be safe.
I am a being a wimp here and being too safe or can I start to add some more boost and timing to this taking into account my elevation?
This is the same set up I ran on my NHRA test passes @ 146-148 mph trap speed with a lousy 60 ft. in 6500 ft DA.
The data log shows a maximum of 17 psi boost,(most of the run it is much less) 11.2 AFR and 11.5 degrees of timing at the max boost level. There was no knock present on both pulls. Car ran clean. I am running 91 octane (Premium fuel at our elevation) and meth injection) IAT were 95 degrees.
The combo is a forged 408 with at S400-Hp88 turbo. The car weighs about 2400 lbs without me in it. Powerglide car with 3,73 gears and 32" tall slicks.I am at 4500 ft actual elevation and the DA is usually close to 7000 ft.
I am planning on going to the track here in a week or two and would like to get the boost up to the 20 lb range with the meth. I have the timing on the table down to around 10 degrees at the 20 psi boost level to be safe.
I am a being a wimp here and being too safe or can I start to add some more boost and timing to this taking into account my elevation?
Sure you can run more boost. The turbo will just work harder (spin faster) to create the same boost at 4000ft as it would at sea level. Your power gained per pound of boost will be down slightly as your base power output will be down in the thinner air. Running more boost is a good way to get around the altitude issue. I'd crank it up to 25 or so at 7000DA.
Your timing sound really conservative for a 408 IMO. But I'd dial up the boost to what ever your comfortable with first. Adjust timing last a point (or half point) at a time until your MPH stops making big jumps. (1mph or more IMO). Personally I wouldn't go above 15* or so on pump gas.
Your timing sound really conservative for a 408 IMO. But I'd dial up the boost to what ever your comfortable with first. Adjust timing last a point (or half point) at a time until your MPH stops making big jumps. (1mph or more IMO). Personally I wouldn't go above 15* or so on pump gas.
Thanks for the reply. I will swap out WG springs and get it over 20 psi and see how it runs. I knew it was conservative but I have been taking it slow on the tuning as I only am able to do one pass on the street before I need to get home as with the 5" DP it is pretty loud at WOT.
Thanks for the reply. I will swap out WG springs and get it over 20 psi and see how it runs. I knew it was conservative but I have been taking it slow on the tuning as I only am able to do one pass on the street before I need to get home as with the 5" DP it is pretty loud at WOT.
That chassis shouldn't take much to go crazy fast. May want to schedule a dyno visit to get it tuned in. I've always tuned my stuff on this road as well. But this 8 second 160mph stuff is getting a little sketchy. Lighter the chassis and shorter the wheelbase the worse it gets!
Good luck!
I swapped the waste springs to a large and small blue one for about 15 lbs on the gate. I put a turn or two on the boost controller and took it out and it was at about 16 lbs or so. I will take it out again this week and get it dialed in to around 20 lbs or so.
Yes, this car is harder to street tune due to the speeds and noise involved. I just shift into drive and stay in it for a second or two and then hurry and slow down.
I have never liked running cars with big slicks and automatics on the dyno. I really should do this one as the dyno is only about 5 minutes from my house and I could dial it in much better and more quickly there.
Yes, this car is harder to street tune due to the speeds and noise involved. I just shift into drive and stay in it for a second or two and then hurry and slow down.
I have never liked running cars with big slicks and automatics on the dyno. I really should do this one as the dyno is only about 5 minutes from my house and I could dial it in much better and more quickly there.
