Blow thru Turbo "Lite"

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Corvair_nut
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Blow thru Turbo "Lite"

Post by Corvair_nut »

OK.... this is the situation. Ive got a twin TBI Fuel Injection 110 mated to a powerglide... (I know... powerslide, whatever). I like the powerglide as it rearly breaks and ... look Mom.... no hands shifting. Ive gotten about as much as can be gotten out of a 110 smog/PG and thinking where the weak points are.

The main problem is somewhere around 1800-2400 RPMs, very little is being made as far as power and that is where it ends up after a shift. Yes... I can up the shift by more "foot", but that again is not the problem. The engine makes very little power at lower RPMs. My technical advisors (Corvair Friends) say to use a 140 with the offset cam as EFI can make up for some of the lower RPM losses, but rebuilt 140 heads cost more than most good cars. And again the 140 suffers also at low RPMs mated to a PG....so I want to go in another direction.

From my rude knowledge of Turbo, I think with certain vain angles, fans, etc a turbo can start producing boost early and quickly. I have designed Caps for the TBI-700 throttle bodies that would work well on a blow thru turbo.... so with all that said.. here is what Im propossing

A blow thru turbo that gets up on boost early, like 2000 RPMs and does not go high on boost as Im just wanting a little HP for the take off and the upshift. I know it would be mostly ineffective at high RPMs, but at 4000, Im doing 80 MPH, which is my limit after my last talk with the SCHP. I dont want to worry about the heat and torture that high boost engines create on the engine..... im just wanting a little help (20 extra HP). I know I can do more and get more HP, but I'm looking for modest gains without building a monster to support it. Did I also mention... this is a daily driver with 55,000 miles on the EFI system and would be used the same with a turbo.

Miniman82... awaiting your input as very few have as much hands on as you.

Thanks

Ted Brown
Anderson, SC
68 Convert/PG/EFI/DIS/FDB/ABC/123
http://www.corvairnut.com
miniman82
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Re: Blow thru Turbo "Lite"

Post by miniman82 »

Turbo is the easy part. Something from the T3 family is what you're after for fast spool, possibly a hybrid, what I'm wondering is can the regulators in your TBI's deal with positive manifold pressure? I suspect that now would be a good time for you to go with an aftermarket external one, if you already haven't. Make sure you factor in an intercooler since you have blow through, it can save your engine. Good place is right up against the openings for engine cooling air, that way you won't need to force air over it with a fan. If the surface area of the IC is large enough, the increase in head temp as a result should be negligible.
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Corvair_nut
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Re: Blow thru Turbo "Lite"

Post by Corvair_nut »

Would a T3 .50 be a good place to start since Im wanting quick spool, low RPM? If I go draw thru, would that make it much simplier?

I have been toying with the 4.3 single TBI, but didnt want to fight the freezing and throttle delay you get with NA. How does a quick/regular turbo handle/improve that situation? Trying to figure which would be best.... my twin TBIs with Blow Thru or single larger TBI draw thru. I never thought about the pressure against the TBI fuel as Ive got about 11-13lbs of fuel pressure. At 6 lbs of boost, that would reduce fuel flow and possiblity of leaning my mix.

Again.. I'm not wanting a fire breathing dragon.... Im guessing on what Ive read, but I was wanting low boost around 6 PSI. A little help to get me through the hard times as a daily driver. The other factor is dependability which I want to factor in also.

Im wanting to emulate the 140 mid power with plenty of low RPM torque that the Corvair never had.
Ted Brown
Anderson, SC
68 Corvair Convert, 110/PG/Brown Fuel Injection System
61 Corvair Loadside 102 EFI
61 Corvair Rampside
Honda B22/Corvair PG
miniman82
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Joined: Wed Jan 20, 2010 2:40 pm
Location: Great Mills, MD
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Re: Blow thru Turbo "Lite"

Post by miniman82 »

Corvair_nut wrote:Would a T3 .50 be a good place to start since Im wanting quick spool, low RPM? If I go draw thru, would that make it much simplier?

No, something with a larger compressor like the 2.3 Ford engines had. They had a .63 hot side and .60 cold, with a much bigger compressor than the T3/50. Of course draw through is simpler, but you already have injection! Why take 1 step forward then 2 back?

I have been toying with the 4.3 single TBI, but didnt want to fight the freezing and throttle delay you get with NA. How does a quick/regular turbo handle/improve that situation?
You mean the long runner issues associated with a single TB? Won't help at all, I don't think. Only thing that's ever helped that situation is manifold heat, and a lot of it. I suppose the turbo would add some much needed heat, but you'd still be pumping in fuel by the bucketload till it warmed up. Icing and all that shite.
Trying to figure which would be best.... my twin TBIs with Blow Thru or single larger TBI draw thru.
I think you should stick with the twins. Throttle response will always be better, and you don't have the fuel dropout issues like you would with a single.

I never thought about the pressure against the TBI fuel as Ive got about 11-13lbs of fuel pressure. At 6 lbs of boost, that would reduce fuel flow and possiblity of leaning my mix.
I don't know if your existing ones would compensate, but it would be easy enough to add an external one I'd think.
I was wanting low boost around 6 PSI. A little help to get me through the hard times as a daily driver. The other factor is dependability which I want to factor in also.

Shoot for at least 8-10 range, 6 won't get you nearly anywhere- the added complexity isn't worth it unless you're really gonna take advantage, know what I mean? 10 isn't really that much, and you already have better heads than my open chamber 180 has. That thing takes 10 lbs no problem, I imagine a 110 head with modern injection and an efficient turbo could get away with it pretty easy.
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