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Pontiac - Boost Turbo, supercharged, Nitrous, EFI & other Power Adders discussed here. |
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#41
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Usually the outlet of the wastegate is plumbed into the exhaust pipe from the turbo downpipe. Some guys route it down to open air like the old engine road draft tubes. That's noisier, but has less backpressure restriction of course.
A blow-off valve just dumps to open air since it is venting air. |
#42
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I would think with a manual transmission, you would really need a blow-off valve. This will allow the compressed air an escape route when the throttle blades close between shifts. This is better than the air rushing back and hitting the compressor blades. You can either vent the blow-off valve to atmosphere, or plumb it back to the intake tract of the turbo (the compressor, not the turbine side,) which would give the turbo a slight help to recover between shifts. You can get a cheap and very effective BOV from 90-94 Mitsubishi Eclipse turbo cars. They are usually good for around 20-25 psi.
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Panos Little Miss G Racing |
#43
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Thats a good point about the throttle blade and shifting. We will look into a blow off valve. The kits didn't have one but must have worked with damage to the turbo, but I can see how it would help.
Joe |
#44
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A Compressor By-pass Valve, as was mentioned, is very common on today's turbo cars.
It doesn't by-pass the compressor, it by-passes the air as was said in Post #42 vs having the closure of the throttle drive the Turbo into surge when the mass flow stacks up on the closed blade. Tom Vaught
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"Engineers do stuff for reasons" Tom Vaught Despite small distractions, there are those who will go Forward, Learning, Sharing Knowledge, Doing what they can to help others move forward. |
#45
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Turbo Vacuum control : For standard dist. I used the 68 Firebird dual outlet control.believe it was a delco 1115411.Also 1115367 By digging deep in the parts book ,I found a dual port HEI control used on some Caddys about 1980-81.delco P/N 1973595
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GOOD IDEAS ARE OFTEN FOUND ABANDONED IN THE DUST OF PROCRASTINATION |
#46
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I'm privileged to have had him as General Manager of H-O Racing Specialties, Inc. and then later when he was the owner of same. |
#47
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Plumbing wastegates with manual boost controller to set boost: http://www.tialmedia.com/documents/w..._wginstall.pdf Plumbing Blowoff valves: http://www.tialmedia.com/documents/w...bovinstall.pdf Should give you some more ideas. This is how my AWD Talon is setup, except I run a pair of wastegates instead of one.
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Panos Little Miss G Racing |
#48
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I often found myself being the go to guy for hard to find or oddball parts...even when I was in the Air Force. Seems I have a knack for finding them one way or another. Think I know someone not far from me who just may have one of those(more maybe?) cannisters now that I have some numbers... Thanks again. I'll let you know what I turn up. |
#49
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If you find a extra 2 port 68 vac. control, let me or Ken Crocie (Dad) know. This will help our latest project. Pure simplicity.
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#50
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Not sure if I understood a previous post. Instaling a BOV will keep the turbo speed in check, not increase it. If air is moving the turbo is doing "work." With no BOV the turbo can overspeed when airflow stops, like throttle shut. Put your hand over a running shop vac inlet and listen to the motor speed up. Correct me if I'm wrong here.
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#51
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If there wasn't a bov in the system the turbo could be damaged when the throttle closes. When the throttle closes the air stacks up and pressure is sent back toward the compressor wheel. The wheel could be stopped and started again very rapidly by this, and could damage the wheel or even break the shaft. The turbo does not speed up when the throttle is closed and there is no bov installed. The reason that the the turbo could possibly speed up when the bov is opened is because of pressure on each side of the turbo. Pressure and mass is driving the turbine wheel wich is driving the compressor wheel. The compressor wheel is pushing air into the engine when the throttle blade is open. When you shut the throttle blade and the bov opens there is no more pressure in the charge pipe, but there could be some pressure in the turbine side. Think of it as a tug-a-war. Two guys are pulling on the rope and one guy lets go letting the other guy go flying. If everything is sized correctly and a w/g is used the turbo shouldn't overspeed when the bov opens because as the throttle closes exhaust mass decreases putting little pressure on the turbine wheel. This is how I understand it. I hope this helps. Ronnie |
#52
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My BOV post was a throttle shut scenario, just after WOT.
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#53
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engine repair
Moving forward with the project, I tore into the engine for a quick check. Turns out water had gotten to the cylinders when the car was being wet sanded during its paint job. The block and pistons were damaged, heads ok. The block is .030" over now with a TRW forged piston. I suspect it will have to .060" to clean up, it might at .040" but unlikely. We will need new pistons and are wondering if we should lower the compression. Summit sells Icon forged pistons that are dished +14 cc, the TRW / Sealed Power are a +6cc piston. Will that make much difference? Remember, this is a restoration project, 6-8 psi boost only and no racing. I know Ross makes great pistons but may be out of the budget, we are still in the planning / recovery mode.
It also has the exhaust crossovers in the head filled. I believe this should come out to help cold starts and atomize the fuel better, but being a turbo engine, will it matter? One more thing, the engine has a solid harmonic balancer install. When I say solid, I mean solid, no moving parts! I can not see any point in this, who was selling them back in the late '90s when this engine was built and why? Joe |
#54
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You can also (as Ken C jr mentioned) set up your system to where you can run a oversized Turbo and keep it out of surge by having the BOV open (adding mass flow to the system but wasting it) until the engine goes into WOT and then BOV closes and the turbo supplies the larger air flow to the engine. Tom Vaught
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"Engineers do stuff for reasons" Tom Vaught Despite small distractions, there are those who will go Forward, Learning, Sharing Knowledge, Doing what they can to help others move forward. |
#55
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#57
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I can use it, in another project I am working on, as a register for a degree wheel. Send me a PM and I will send you an address! LOL! Tom Vaught ps I would never use one of those things on a RUNNING ENGINE!
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"Engineers do stuff for reasons" Tom Vaught Despite small distractions, there are those who will go Forward, Learning, Sharing Knowledge, Doing what they can to help others move forward. |
#58
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TV & CH : you old guys are sure forgetful! Remember Pontiac used solid,no damper, hubs in '76-'77.Those engines used a bolt on timing tab as well. Maybe this is what joe has. I wouldn't use it either. The '67 and earlier engines used a solid hub with a bolt on dampener. maybe one of those found it's way to joes engine.
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GOOD IDEAS ARE OFTEN FOUND ABANDONED IN THE DUST OF PROCRASTINATION |
#59
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The balancer appears to be aftermarket. It was black at one time but now rusted. I don't believe its a Pontiac hub as it matches the originals in size and diameter. My local machine shop had never seen one either and also said to toss it. I can send you a picture if you wish to post it or see it.
TRW pistons it is and some digging on the heads. I believe they used Hard Block in the cross over's, it sure reminds me of concrete and flakes out like concrete. The camshaft is not marked so I need to degree it and see what it is. A reproduction 068 cam should work, shouldn't it? Can we get a original cam for this engine? or how about the HCO1 cam from SD Performance, I have used it with really good results. The Summit 2801 cam is also a decent street cam. Joe |
#60
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