Anybody running turbos and a switch pitch trans together? I've made only a few passes but so far I like it.
I was going to run a SP-TH400 with a 3800 high stall and a 2000 low stall, it is a great way to get the boost up on launch I was thinking. Instead I am going with a built 200r4 with 3500 stall and lockup converter this way I have a nice high stall like the switch pitch but can lock it up 100% when I want to, plus the 4th gear. I have been messing with a 700-R4 that I have in my daily driver and I added a 3500 stall converter, and modified the lockup function so I can turn it on and off or leave it in automatic lockup which works off engine vacuum (lockup at 9 hg of vacuum or higher). This works like a charm! Leaves the hole HARD and I cruise the highway at 350 rpm lower than without the lockup!
How high is your high stall and how much boost do you get at the line before launch and what rpm? How are you operating the low stall? Using a timer, manual switch?
I hadn't thought about a 700-R4 before. I have considered a 4L80E. It's an old KB SP149 (I think that's the number?). The high stall isn't a lot, but it's noticeable. Switching from high to low stall will bark the tires. Right now I'm using a button on the steering wheel. Just after the car launches, I release the button. I haven't learned to look at the tach and boost gauge yet, so I don't know the numbers! ou: No boost at the line. I press the button and bring the rpm up a little, then mat it on the last yellow. I plan to build a circuit that will latch the S.P. on, then unlatch it at a preset boost or RPM level.
At the end of the race season this year I put the switch pitch out of my bracket car into the Skymaro. It is a 3000 stall Switch Pitch and low side is really low like 600. In the bracket car I could foot brake the SP almost to 3000. I have not done any serious testing on the turbo setup yet.
I would not use a 700R4 behind a turbo engine, but they are good in mild under 400 hp combos.... The 4L80E is VERY strong trans and if you are willing to run a manual valvebody then you can avoid the computer issues.
Sean, your 2004r talk is making me jealous. You know it's on my wish list right? 2004r and tube chassis are the last big things on the dream list left. Well, except for paint and cosmetic stuff.
I know, but as you know things are coming along slow for me as well these days... I found a good 200r4 core and saving up for the rebuild....
What ever it gets next needs to be stronger than what's in it. My best guess is it's over 500hp now, and hopefully 600 isn't too far away. I'm shifting at 5700 and don't have an intercooler on it yet.
So far it's all been 1/8th mile. The best so far is an 8.18 @ 87.92, with 8 lbs of boost. The best 60' so far is 1.902, I think that was with 4 lbs.
What is your combo? 455 cubes and stock heads? I can not see you being at only 500 hp with 8 psi unless you only made 350 hp NA. I am going to spray at least a 80 shot of nitrous into my twin turbo car to help inter-cool and also boost performance... Nitrous is VERY cold so it works great with turbos.
The point has been raised that higher torque applications can put too much thrust on the stator thrust bearing. I think your KB will have a torrington, which will help, but that is supposedly the weak link with a SP. As you dial-up the boost you might take out the thrust bearing in your converter. I know that Burek and some of the V-6 turbo guys have claimed they work real well from an operational standpoint.
462 cubes, non-ported stage 1 heads. Stock rods and forged replacement pistons. I need to look at the timing and the A/F ratio. I'm using race gas to be on the safe side. I'd like to get a 7.99 out of it before I upgrade everything. I don't know what the limit is, and I really don't want to find out the hard way! :error: I plan to build a standard TH400 this winter. A heavy duty switch pitch setup would be great, although a lockup converter would work well, too.
Alan, I really want to see you car/setup....of course I probably don't since it would all fit under the hood of my 73 Limited 2 door......
I removed all the A/C stuff and converted it to manual steering (if you can imagine such a thing!!!), but all that could be worked around! And your car would be lighter! :Brow:
I researched both sp-400 and 200r4 and kept flipping back and fourth on the two...and finally decided to stick with for sp400. Mainloy because of its durability with no need to freshen it up every couple years it's cheaper! and if i really truly need and o'd i can always add a gears vendor unit..
A switch pitch is nice, but the way to go is really a well built converter matched to the combo with the th400 unit. A properly built unit will work better and survive longer then a switch pitch unit. Question to Alan. What specs are your turbos?
I'm not as good at keeping up with details as I need to be! What I remember is T04-B with T04-E compressor wheels (or housings?) and .96 A/R turbine housings.
