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Turbo waste gate discussion
Posted by: DOUG WARD ()
Date: August 11, 2022 06:47PM

Well guys, I am re-doing my turbo exhaust system. I had previously attached the waste gate to the pipe going from the crossover ( head to head) that leads up to provide the turbo it's exhaust pressure / heat. I did show good pressure readings on the panel gauge. As I got to working on it though, I thought to myself " wait ! doesn't the system build pressure from the OUTPUT of the compressor ?" shouldn't the waste gate be between the exhaust outlet on the turbo & the muffler ?
I didn't seem to be able to tell if or when the gate opened so I put one of those cheap little whistles in it . Still could not tell or hear any sign that the gate was opening. ( my system puts out what appears to be about 20 PSI without the gate so I adjusted it to open at 10 PSI.)
I briefly asked one of our well known turbo guys who frequents our forum & he said that I DID have it in the correct position. This just doesn't make sense to me, but if I am still out in left field on this I would like to hear your comments.

Doug Ward
Orange, Calif.
65 Corsa 180, 64 Monza convertible, 61 Lakewood, 61 Monza


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Re: Turbo waste gate discussion
Posted by: MattNall ()
Date: August 11, 2022 07:55PM

Sounds like you have a "Blow-off" [no sensing line] that is mounted on the engine's intake tract.

Post a picture or LINK to which valve you bought

MODERATOR
Sea Mountain, between Charleston Harbor and Coos Bay! SW Oregon Coast
Click HERE for My Website...Click HERE for My TechPages!
...............110-PG.................................................Webered-Turbo

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Re: Turbo waste gate discussion
Posted by: Darrin ()
Date: August 11, 2022 08:23PM

You have it in the right place Doug, but sounds like it may require service or an upgrade.

The exhaust gas is vented off before the turbine to regulate max pressure going in, thus controlling the spinning speed of the turbine, etc. More modern turbos route the waste gas back into the exhaust pipe after the turbo so it goes through smog equip.

Darrin Hartzler
Bethesda, MD/Catlett, VA

Northern Virginia Corvairs & Group Corvair

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Re: Turbo waste gate discussion
Posted by: zarfnober ()
Date: August 11, 2022 08:36PM

Your waste gate has to be installed after the head and before the turbo, and yes, there is positive pressure on the exhaust side. They’re adjusted to limit boost by bleeding off exhaust pressure. Blow off valves like Matt mentioned bleed off boost pressure on the intake side to keep the turbo spinning when you back off the throttle between shifts, you don’t want this in a draw through setup, and on a blow through, it has to be before the carb, otherwise you’re blowing gas all over the engine compartment.

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Re: Turbo waste gate discussion
Posted by: DOUG WARD ()
Date: August 11, 2022 08:57PM

Matt, I have a TIAL MVR/MVS waste gate. I bought it from Ray Sedman & it does have an air supply ( sensing ) hose from the intake manifold. It is installed per the instructions that came with it.

Darrin, I understand when you say that the exhaust is vented before the turbine but there is no BOOSTED pressure there.That is just exhaust pressure / heat. I thought that the purpose of the waste gate was to relieve excessive boost, which occurs AFTER the compresser. ( the more I learn, the more confused I get )

Doug Ward
Orange, Calif.
65 Corsa 180, 64 Monza convertible, 61 Lakewood, 61 Monza


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Re: Turbo waste gate discussion
Posted by: DOUG WARD ()
Date: August 11, 2022 09:12PM

Zarfnober, OK, I am beginning to get how the system works. Oh; I see in the diagram that the sensor hose going from the intake manifold to the waste gate DOES read the boosted intake pressure & then opens the gate at that point. The sensor opens the gate which then relieves the excessive exhaust gasses from the exhaust supply.

I will be putting on a blowoff valve as well - in the boosted tubing going from the compressor to the carb. intake piping.

I knew you guys would show me the way to understanding this system. This is my 10th Corvair but it is my 1st turbo. I have "hot rodded" a few in the past & always wanted to try out this blow thru style of intake stuff.

Doug Ward
Orange, Calif.
65 Corsa 180, 64 Monza convertible, 61 Lakewood, 61 Monza


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Re: Turbo waste gate discussion
Posted by: MattNall ()
Date: August 11, 2022 09:42PM

Doug, did you test the valve with regulated compreesed air?

Post a pic of the topside of your engine

MODERATOR
Sea Mountain, between Charleston Harbor and Coos Bay! SW Oregon Coast
Click HERE for My Website...Click HERE for My TechPages!
...............110-PG.................................................Webered-Turbo

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Re: Turbo waste gate discussion
Posted by: playerpage ()
Date: August 11, 2022 09:46PM

This stuff always makes me want to tinker--but then I don't want to have my car down for another year.

Cheers.

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Re: Turbo waste gate discussion
Posted by: cnicol ()
Date: August 12, 2022 05:19AM

Normal configuration Corvair turbos don't play well with intake-side pressure control "blow-off" valves because pressurized air on the intake side also contains fuel so the vented blow-out gasses are explosive. Modern cars with EFI engines don't have that issue.

As has already been covered, Cotvair over-boost is controlled by venting exhaust pressure.

Craig N. Coeur d'Alene ID.
66 Black Monza 4dr, 4.2L V8 49k
61 Seamist Jade Rampside 140 PG
65 Canadian Monza 4dr 110/PG 40k
66 Sprint Corsa convt - First car! Re-purchased 43 years later
2+2 gnatsuM 5691

+17 Tons of parts

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Re: Turbo waste gate discussion
Posted by: Darrin ()
Date: August 12, 2022 05:19AM

placing the wastegate after the turbo would not affect the spinning speed of the turbine wheel. You would just be venting off exhaust before it got to the muffler which does nothing to what is happening inside the turbo. In order to control the spinning of the turbine you have to control what's going into the turbo not what's coming out does that help?

on a Corvair where the gas is drawn through the turbo charger compressor side a blow off valve would be venting air fuel mixture into the engine compartment. Not good. Cannot use a blow off valve in a Corvair unless you do a blow through system where the turbo is blowing through carburetors. would also work on a fuel injected Corvair. In that case you would just be venting off compressed air with a blow off valve before the fuel is added, unlike a stock turbo set up.

Darrin Hartzler
Bethesda, MD/Catlett, VA

Northern Virginia Corvairs & Group Corvair

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Re: Turbo waste gate discussion
Posted by: DOUG WARD ()
Date: August 12, 2022 01:15PM

Matt, I did test the W/G with about 15 to 20 PSI air pressure & it's opening the valve. I still have trouble posting pictures .


Craig, The blow of valve will be installed in the outlet pipe from the turbo to the air intake manifold to the 4 carbs. A blow thru system. It won't contain any fuel mixture at that point.

Darrin, your comment is the most interesting to me. Seems to me that if the W/G is in the boosted side, it will relieve the excess pressure AND keep the turbo spinning so if one got on the loud pedal immediately after letting up, the residual boost would still be there, instead of having to wait for it to spool back up & produce boost again. Like I mentioned to Craig, it is a blow thru system. I'm anxious to see your response to this.

Doug Ward
Orange, Calif.
65 Corsa 180, 64 Monza convertible, 61 Lakewood, 61 Monza


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Re: Turbo waste gate discussion
Posted by: Darrin ()
Date: August 12, 2022 02:02PM

Can you clarify "on the boosted side", you mean on the intake/compressor side coming out of the turbo to the carbs?

Darrin Hartzler
Bethesda, MD/Catlett, VA

Northern Virginia Corvairs & Group Corvair

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Re: Turbo waste gate discussion
Posted by: playerpage ()
Date: August 12, 2022 02:06PM

I don't think it comes out of the turbo into the "carbs". It comes out of the "carb" into the turbo.

Eric C. Player
Fargo, North Dakota
MEMBER: CORSA National, Central Coast CORSA, South Coast CORSA, Vintage CORSA, Sfba CORSA, and Great Plains Corvair Club.
THEN: 1965 Monza 110, Canary Yellow - 1965 Corsa 180 Turbo, Red - 1966 Monza 110, Purple - 1967 Monza 140, Red - 1966 500 110, Black; nicknamed "Shadow" - 1965 Monza 110, Camaro Yellow; nicknamed "Silver"
NOW: 1966 Corsa 180 Turbo, Blue; nicknamed "Bluvair"
---------------------------------------
"He cautioned me not to take notes. It would not have helped if I had, as he would start a paragraph with, 'It is therefore obvious. . .'
and go on from there to matters which may have been obvious to him and God but to no one else."
-- Robert A. Heinlein, character of Daniel B. Davis, 'The Door Into Summer.'

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Re: Turbo waste gate discussion
Posted by: DOUG WARD ()
Date: August 12, 2022 04:49PM

Darrin, yes the boosted side is coming out of the turbo to the carbs.

Eric, In this system, I have removed the YH side draft carb.so the turbo just draws air from the air cleaner. The boosted air exiting the turbo goes to the intake air manifold ( a re-welded one that fits onto the 4 Rochesters - I call that part an intake spider )and blows the pressurized air thru them; they then mix the air with fuel & passes that mixture into the engine.

Doug Ward
Orange, Calif.
65 Corsa 180, 64 Monza convertible, 61 Lakewood, 61 Monza


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Re: Turbo waste gate discussion
Posted by: Darrin ()
Date: August 12, 2022 05:30PM

Gotcha. That would be a blow off valve. You can do either wastegate on ex side or blowoff on intake. Same result by different means.

Darrin Hartzler
Bethesda, MD/Catlett, VA

Northern Virginia Corvairs & Group Corvair

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Re: Turbo waste gate discussion
Posted by: Darrin ()
Date: August 12, 2022 06:33PM

Doug, did you modify/stiffen the floats in the carbs when you did the blow through Set up?

Darrin Hartzler
Bethesda, MD/Catlett, VA

Northern Virginia Corvairs & Group Corvair

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Re: Turbo waste gate discussion
Posted by: roger65180 ()
Date: August 12, 2022 07:05PM

Darrin the blow off and the waste gate do not do the same thing the blow off only dumps air when the throttle is suddenly closed as in up shifting the wastegate opens when the exhaust pressure exceeds the spring pressure holding it shut and since we are talking about a modified turbo system you should also have an exhaust pressure gauge if you really want to make power , the boost and exhaust pressure should be close to a match . all tho I have never checked a stock system I bet they are close , I personaly know the guy that builds the worlds fastest snow mobile drag sleds when I was talking to him about my lowly corvair he asked me what my exhaust pressure was and I didnt know sow I went home and installed a gauge after both sides joined before the turbo I had 1 and a half times as much exhaust pressure as boost thats ok only if you want to get to the next stoplight first , on the dyno i would see early boost i could open the waste gate in first gear 15 lbs boost and the power curve goes straight up to 5000 and starts back down now that i have both balanced it is still going straight up at 5000 rpm

Roger R
Madison Wi
62 ct pg turbo
65intercooled 180 4sp,autocrosser
62 Rampy

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Re: Turbo waste gate discussion
Posted by: DOUG WARD ()
Date: August 12, 2022 07:42PM

Darrin, the floats are getting modified. I knew about that but hadn't done them yet. All 4 , right ? I am pretty sure that I'll be better off with both a W/G and a blow off . Seems to me that they compliment each other in function. I would still like to see your take on my comment about 6 posts ago,( 8/12/22/1:15 p-m ) about the W/G being on the output side.

roger65, I'm still trying to understand your comment. Could you clarify ?

Doug Ward
Orange, Calif.
65 Corsa 180, 64 Monza convertible, 61 Lakewood, 61 Monza


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Re: Turbo waste gate discussion
Posted by: vairmech ()
Date: August 13, 2022 05:17AM

If it isn't settled yet the waste gate needs to be installed in the turbo exhaust inlet pipe. You will want to put a flange on the outlet and connect it to the outlet pipe before the muffler. It will scare the SH-- out of you the first time it lets exhaust out, it will be loud if you just dump it out.
Think of the name to make it simple, waste gate. It wastes the exhaust, exhaust is waste isn't it? WELL, not in a turbo but you get my meaning.

As far as a blow off valve for the intake, try it without fist.

Ken Hand
Handy Car Care
248 613 8586

Vairmech@aol.com

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Re: Turbo waste gate discussion
Posted by: DOUG WARD ()
Date: August 13, 2022 10:41AM

Hi Ken, The waste gate IS welded to the exhaust pipe going up in to the turbo. Are you saying that it should ALSO be connected from the W/G 's outlet to the exhaust pipe as it enters the muffler ? I just re-read what you said & I think you mean that if I DON'T attach the W/G outlet to the muffler inlet, it will then be really loud. If that is so, then that is how I want it. I DO want to know when the engine is making full boost, and letting the excess pressure out, audibly.

Can you describe what will happen if there is no blow off valve ? as opposed to having one ?

Doug Ward
Orange, Calif.
65 Corsa 180, 64 Monza convertible, 61 Lakewood, 61 Monza


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