question about track times
Thread Starter
Staging Lane
Joined: Mar 2009
Posts: 94
Likes: 0
From: Perth Australia
question about track times Hi Recently ran at the track with my 408 single gt4294, 3000 stall, 2.75 ratio in the 9" with 26x8.5x15 mt street radials. 3800lb race weight. Rattled off a 10.91@124 mph and a 1.60 60ft time first run. Zero boost built off the line just point and shoot. I was impressed but could feel it lay over a bit in the second half of the track.
I had been told the turbo was too small and it showed on the dyno flat lining at 560hp from about 3400rpm so I did some back pressure tests pre turbine on the street. Running 12psi boost, readings I managed to get at 4000rpm I hit 38psi pre turbine i'd imaging it would of kept climbing if I kept the boot into it.
So turbo upgrade is coming but the question I have is could the 2.75 diff ratio be too tall for drag racing or just my turbine back pressure? Is that track time and mph about on par for the power and weight? I ran a second time that night but stuffed up the take off, ran 11.3 with same mph.
I had been told the turbo was too small and it showed on the dyno flat lining at 560hp from about 3400rpm so I did some back pressure tests pre turbine on the street. Running 12psi boost, readings I managed to get at 4000rpm I hit 38psi pre turbine i'd imaging it would of kept climbing if I kept the boot into it.
So turbo upgrade is coming but the question I have is could the 2.75 diff ratio be too tall for drag racing or just my turbine back pressure? Is that track time and mph about on par for the power and weight? I ran a second time that night but stuffed up the take off, ran 11.3 with same mph.
I've got a 3.08 and a 26" tire. The 60' isn't really killing you. Turn the boost up. 12psi, your weight, and that trap is like 550-600whp I believe. What's the weather like? Altitude, temp, humidity.
This is 16psi, 5.3, precision 76gtsh, TH400, etc.
This is 16psi, 5.3, precision 76gtsh, TH400, etc.
Thread Starter
Staging Lane
Joined: Mar 2009
Posts: 94
Likes: 0
From: Perth Australia
Yeah I was pretty happy with my result first time, 54% humidity, temp 63f, density altitude 395ft. We were running in between rain and oil downs all night. Cameronvic thanks for putting up your slip, gave me a comparison, My car on the dyno was finding it hard to make anymore grunt even tried adding a bit more boost hit 575 but it we backed it off and fattened it up. Power flatlined at 560hp from 3400 to redline.
I am upgrading the turbo to uncork this 408 a bit, Scored a gt4708 for next to nothing and it fit in my engine bay without having to cut any of my kit up so I am going to run it and see what happens on the dyno. I have a spare 9" centre so will set up the 3.25 ratio I found also. Season fires back up in a couple of months.
I am upgrading the turbo to uncork this 408 a bit, Scored a gt4708 for next to nothing and it fit in my engine bay without having to cut any of my kit up so I am going to run it and see what happens on the dyno. I have a spare 9" centre so will set up the 3.25 ratio I found also. Season fires back up in a couple of months.
Yea I forget you guys are coming out of the winter down there. LOL. That's confusing to someone in the northern hemisphere. I'll bet your car will love 3.25. What were your RPMs through the traps on the 2.75?
Thread Starter
Staging Lane
Joined: Mar 2009
Posts: 94
Likes: 0
From: Perth Australia
Didn't check but didn't feel like it was in the sweet spot, felt quite low in the rev range. That's why I was asking initially as I didn't know if it was the turbo just choking me back or my gears were too tall. But back pressure pre turbine was ridiculously high so I have taken the gt42 off and the gt47 is on now. Not sure weather to try run the 2.75 with the new turbo first or switch ratio now.
Another question I have, Should I run the water jacket on this turbo stand alone, through the engine cooling system or can I get away with not running fluid through the water jacket on the turbo? Not sure which way to go. This is a journal bearing 47 with water jacket.
Another question I have, Should I run the water jacket on this turbo stand alone, through the engine cooling system or can I get away with not running fluid through the water jacket on the turbo? Not sure which way to go. This is a journal bearing 47 with water jacket.
"Running 12psi boost, readings I managed to get at 4000rpm I hit 38psi pre turbine."
"The 60' isn't really killing you. Turn the boost up. "
Turn up the boost w/ this back psi already seen with 12#??
"The 60' isn't really killing you. Turn the boost up. "
Turn up the boost w/ this back psi already seen with 12#??
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Staging Lane
Joined: Mar 2009
Posts: 94
Likes: 0
From: Perth Australia
tried winding the boost up on the dyno and it just wont make more power past 3400. I will post a vid of this flat power. I do street drive this car so will leave the gear and try it once the track opens again with the different turbo. This turbo makes full boost pretty much straight away so that backpressure snapshot at 4000 rpm was it climbing until I had to back off.
Last edited by StatoJase; Jul 24, 2013 at 09:26 AM.
I guess I skipped over that part the first time through. When you say it like that, I agree. LOL.
Thread Starter
Staging Lane
Joined: Mar 2009
Posts: 94
Likes: 0
From: Perth Australia
heading back to the dyno in a few weeks with the bigger turbo to see how It goes with the bottle neck gt42 removed. The gt47 was cheap and fit straight on so I thought why not. Have decided to run the water jacket lines for the turbo through the cooling system to save on adding a standalone pump and all the other bits. Diff gears will stay at 2.73 for now on everyone's advice as It is a street car and My 60ft times can still be improved by hitting the 2 step and spooling off the foot brake which I havent done yet.
Last edited by StatoJase; Jul 24, 2013 at 07:14 PM.