5.73@122.1 DRW/Buick new best.
- Thread starter Alky V6
- Start date
Its hard to say with the T6 housing. It may drop off after spool or on shifts if the converter pulls it back too much and it may not. Id just find the sweet spot for the N20 shut off where it will keep it spooled no matter what at WOT. Maybe its 18 psi maybe its 23psi. It would be tough to dial in with out CO2 holding the gate shut. It may ramp too fast with a large amount of N2O on spool and blow the tires off. Traction control would be nice. We would need to see the compressor chart and see what the mass flow is at different shaft speeds. It doesnt take much more shaft speed on a larger compressor to get a much higher mass flow. When i use intake air to hold the gate shut i have found i can play with ramp up by using different size restrictors in the gate pressure port. I just use old N2O jets. I actually want a tiny bit of overshoot so i know im getting full boost at WOT in 1st gear. The engine will easily tolerate it for a half a second anyway. You stated earlier you were holding the gate shut with manifold pressure and the spring was good to approx. 30psi. So with that you could add the pressure holding the gate shut to the spring pressure and get somewhat of a bp number. It might be a lot higher than we think. Like mid 50's
. Thats only if the surface area the pressures are acting on on both sides of the diaphragm are the same.
. Thats only if the surface area the pressures are acting on on both sides of the diaphragm are the same.All very good points. Good food for thought. Thanks. I talked to Precision today, and they were torn between the .96 and 1.08. Much the same way I was. Pete swayed more toward the .96 with the T6 housing. He felt that if the .96 a/r did end up being too small, at least you can race with it until the next housing comes in. He saw the only benefit of sticking with a T4 housing being the ease of installation. He was pretty sure the T4 housing would pinch off a little power on the top end. I don't want anything being pinched off. I'm more concerned with getting the right setup for top end power than making it more convenient on me. If the best setup is the T6, then I'll make it fit. Another thing. As soon as I mentioned I was using a 200 shop of nitrous to spool, he didn't hesitate to recommend the T6 housing.
- Joined
- May 27, 2001
Great minds think a like, maybe Harry should hire me LOL...
If the 3 to 3.5 liter import guys can run a T6 GT5591 I did not see any reason you could not run the GT4788 T6 with an extra liter.
I want pictures when you are mocking that mutha up!!!
Dusty Bradford
Well-Known Member
- Joined
- May 24, 2001
The BW turbine wheels will not flow like the Garrett stuff. I tuned a car with the 75mm version but it was on a 406 SBC...not much to relate to your application.
I do think you'll be suprised with your bp readings. With the times you've posted I would think your very near 60# of backpressure, my guess is 54#.
I'll make sure to take pictures. I'll probably post them on our website.
With all these monstrous bp guesses, I'm starting to think I should swap on the .96 housing I have sitting around for the T76 when I go back together with this leak repair. What do you guys think? Would it be worth a try? What would you guess the bp drop would be with the larger housing? How much hp might there be? The turbine wheel is the old Turbonetics Q trim.
With all these monstrous bp guesses, I'm starting to think I should swap on the .96 housing I have sitting around for the T76 when I go back together with this leak repair. What do you guys think? Would it be worth a try? What would you guess the bp drop would be with the larger housing? How much hp might there be? The turbine wheel is the old Turbonetics Q trim.
- Joined
- May 27, 2001
The housing and wheel are both limiting factors in your combination.
Making one a little better for free, why not?
I don't think you will see a night an day difference though.
Dusty Bradford
Well-Known Member
- Joined
- May 24, 2001
A friend swapped form a 1.0 to a 1.32 a/r on a SBC and it dropped bp from 58# to 48#. The car did not go any faster but he did have to raise the launch rpm around 200 rpm to compensate for the lack of boost down low.
I'm a little curious about what the .96 housing will do for the duration of the nitrous shot at the start of the launch. As it is now, the nitrous gets the turbo to 16 psi in .4 to .7 seconds. When the nitrous shuts down, the nose of the car drops from the loss of power until the turbo can spool up to a higher boost level. If the nitrous has to stay on longer because of the larger housing, that may not be a bad thing. Let's say it has to stay on twice as long to get to the turn off point of 16 psi. That means the engine will be at 10 psi with a 200 shot of nitrous twice as long as before. That means the engine will be at 14 psi with a 200 shot of nitrous twice as long as before. So on and so on. It might be interesting to see how the engine and car react.
With the .82 housing on a 3 amber tree, I would have to wait until the second amber to go WOT so that the car wouldn't be too high on boost by the 3rd amber. What if the .96 delays the boost rise on the nitrous long enough so that I can go WOT on the first hint of the first amber and have the right amount of boost by the 3rd amber. That would make my launch routine much simpler. It's hard timing the WOT on that second amber and then timing the transbrake release on the third.
With the .82 housing on a 3 amber tree, I would have to wait until the second amber to go WOT so that the car wouldn't be too high on boost by the 3rd amber. What if the .96 delays the boost rise on the nitrous long enough so that I can go WOT on the first hint of the first amber and have the right amount of boost by the 3rd amber. That would make my launch routine much simpler. It's hard timing the WOT on that second amber and then timing the transbrake release on the third.
Dusty Bradford
Well-Known Member
- Joined
- May 24, 2001
Just think if you were trying to cut a light on a .400 pro tree
Yeah, that procedure still needs to be figured out. Because of the timer that I use with the nitrous system, I'll have to race in the electronics brackets. In some cases that bracket uses a .4 Pro Light. I'm going to have to go WOT as soon as I stage and wait on the starter to bring the tree down. The nitrous will get the turbo up very quickly. Not too worried about that. The thing that worries me is, how will I keep the boost level reasonable for the launch with a 200 shot nitrous system trying to get it up to 16 psi? With the tires I'm using, a 16 psi launch is too much. I suppose I'll have to start playing with the launch and boost rise features of my electronic boost controller. Launch procedure for a pro light will be one of the last hurdles for me.
You said it in your last sentence. You need to delay the ramp up. Maybe have it come in over 1-1.2 seconds? Your wastegate will be doing a lot of work in 1st. Hopefully it will be enough with that amount of N2O. You would be a lot better off with a CO2 setup for this type of racing.
I've got a CO2 bottle, but I've been resisting setting it up until I really need it. I understand what you're saying.
Big surprise today. I started taking the front of the engine apart to fix a nagging leak. When I pulled the Y pipe that feeds the turbo off, I looked down the side that has a bellows in it. That's the side fed by the left bank. The stainless braided wire mesh inside the bellows has swelled and partially blocked the pipe so that the passage through it is just over 7/8 inch. Ya think I might be losing some power there? The bellows is going bye bye and I'm replacing it with a straight pipe.
Big surprise today. I started taking the front of the engine apart to fix a nagging leak. When I pulled the Y pipe that feeds the turbo off, I looked down the side that has a bellows in it. That's the side fed by the left bank. The stainless braided wire mesh inside the bellows has swelled and partially blocked the pipe so that the passage through it is just over 7/8 inch. Ya think I might be losing some power there? The bellows is going bye bye and I'm replacing it with a straight pipe.
MAybe you should put a pressure tap before the bellows to check the bp:biggrin: . J/k.
What happened, flex pipe collapse?
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