turbo for 200

[FAR OUT]

I just came across a corvair turbo unit (free). I was looking to turbo or supercharge a 200 ci engine for my 62 falcon wagon. I'm not looking to make a race engine - just a little extra zip for an every day driver. Looks super easy to hook up. I have an extra header flange and it would be no problem to weld up for turbo. The unit will sit right along intake log. I was hoping to use the corvair carb that is already mounted to turbo. The corvair was 166 ci. A simple elbow mated to intake log will plumb right to turbo. Automatic choke heat tube is built into turbo flange - the whole unit just looks so easy. Does anybody see any draw backs to this idea?

Dale

 

[Asa]

The unit will sit right along intake log.

by unit, you mean the turbo, right?
well, depending on how close the turbo is to the intake, that could be a problem, as the turbo heats up, it'll heat up the intake as well, which will rob some power
and you might wanna upgrade the carb a bit, i'm not the expert in this, but my gut says it would be a good idea to, you'll be feeding an extra 34cid


how is the general condition of the engine? runs nicely, good compression numbers on all cyl?
if so, sounds good, go for it and keep us posted (and give us pics!)

 

[FAR OUT]

yes turbo included, heat shield could be installed. and if needed I have seen carb adapters for turbo to use other carbs

 

[Asa]

heat shield would be a good thought

hrmmm... i wonder what a Jet-Hot coating would do to a turbo? keep underhood temps down, but it would prolly raise the temp inside the turbo too much.... maybe, not if you did it correctly i guess

sorry, i'm rambling

is this a blow-through, or a draw-through setup? IIRC the one corvair turbo setup i've seen was a blow-through, but i could be wrong

i'd wait till some of the others chimed in and gave their thoughts on it, but it sounds like a solid plan to me

 

[Anonymous]

[No message]

 

[rickwrench]

The corvair rajays are big and take a while to spool, but make a LOT of boost. In stock form, the corvair sidedraft Carter YF was designed to go way over-rich and choke out the engine at the very top end of it's airflow (just before your corvair engine explodes). I have a tech paper on the "mysterious" how-to tuning of the YF sidedraft if you want it. All the parts for rebuilding the turbo are available through Clark's Corvair or Corvair Underground. They also have several different impellers, weber dcoe adapters, and I think they even had 4bbl adapters a few years ago. A properly tuned weber dcoe keeps the A/F mixture correct through the top end, to the redline. The fuel is also atomized quite a bit better than with the Carter. A weber makes these turbos a much nicer animal. So much so that you can't run WOT in a weber carbed turbo corvair for much more than a minute or two (tops) without a meltdown - aircooling does have it's drawbacks.
Size-wise, the corvair turbos are probably a better match for the 200 than either size corvair enigne. The "180" would be great for a 250. There were two stock impellers used, one is the "150" (refering to advertised bhp) and the other is the "180". The "150" impeller was designed for the '62-'63 145 cid engine, but also used in the 1964 164 cid corvairs. The '65 and '66 164 cid engines used the larger, higher flow (and slower spooling) "180" impeller. All were over-sized for the engines they were on.
Jet-Hot would be a great idea. The more heat you keep in the exhaust system up to the impeller, the faster you will spool up. After that, just run open pipes, turbos make great mufflers. The rajay turbo is designed for the heat. Corvairs run much hotter than any water-cooled engine, 400 degree (f) cylinder head temps are average in turbo corvairs. Don't touch the cooling fins.
Before I got the 4x1bbl 140, I had a 180/turbo with a weber for a few years. It was a dog off the line, but once you got into the boost, i.e., very top of 2nd gear, middle of 3rd on, most of 4th, nothing could keep up. NOBODY could keep up on a freeway on-ramp. Water injection will be your new best friend.
Rick(wrench)

 

[FAR OUT]

Rick
thanks for the imput. the turbo unit is the "150" off a 64. it sounds like this is a good choice for the 200. I wonder if a properly tuned carter with the extra cubes of a 200 may not be such a bad idea. I sure do like it for hood clearence aspect. I would be interested in the tech paper. If the carter could run half way decent (seems like less tinkering) I think I would like to go that route. This is a future project that I'm collecting parts for. I still have to finish my sons Futura and have a hilborn fi 250 in a 71 comet for drags to juggle with the turbo wagon. I keep getting older and more projects keep popping up .. or am I getting slower? NAW!

 

[Anonymous]

Hi Rick,

The weber he is suggesting is a 2V side draft unit. I would be a little concerned about top end lean out with the carter. Unless, of course, it has some form of enrichment at WOT. At WOT a turbo is pushing a lot of CFM, so the carb needs to have better flow than the engine could ever use un-turboed. Example, with a turbo you assume 100% VE. Flow required equals normal cfm needed times pressure ratio. Pressure ratio = 14.7 + boost / 14.7. So, if you boost 7psi the pressure ratio is 1.47. The CFM requirement would then be 425CFM ((CID*rpm/2)/1728)*1.47. Be sure not to overboost. As I recall, the Corvair was waste gated at 5psi. 5-7 (1/2 bar) is all I would try to put through a non-computer controlled engine. Otherwise, I think the Corvair unit will make a very nice base for a 200 I6 set-up. Actually, the tubo lag associated with the 145 / 164 cid engine may be cured by the 200. Keep us posted.

Steve

 

[Anonymous]

[No message]

 

[Anonymous]

Please enlighten us.

 

[StrangeRanger]

Probably referring to the fact that density ratio is less that the pressure ratio. They very by the thermal, not volumetric, efficiency of the turbo.

 

[rickwrench]

Here's the CarterYH doc.
The Carter doesn't go lean at the top end, it goes bog rich. The venturi is too small for the airflow. All that top end created vacuum's gotta suck something, and that something is gas. But, the top end over-rich bog-out has saved countless corvair owners from melting down their engines. First by running so rich the engine bogs, and second all that extra fuel cools down the intake charge going into the cylinder. Whether this was a designed in feature or just a happy coincidence, Zora only knows.
For a 200, the 40mm weber dcoe will let you run WOT without going too rich, and give you good throttle response over the entire powerband, with many tuning options. The carter is about as sophisticated as a beer can full of gas with a couple holes punched into it, in comparison.
The rajay unit, although listed as three seperate turbos, is in reality, one center section (one part number) using two different compressors, and three different exhaust housings. Each impeller/compressor is matched to it's particular housing, but you can mix and match the compressor sides and exhaust sides as you like. The two compressors are the 150 and 180, and the three exhaust housings are the 62-63 150, the 64 150, and the 65-66 180. The only difference between the 62-63 and the 64 housing is the exhaust flange.
As panic said, the hot setup is an "E" flow impeller/housing and the stock 180 exhaust housing. The E flow is not a stock piece, but a modern and very efficient impeller design in a modified stock housing.
This is all moot as your turbo is in hand. As fordonatic Dave Williams says "Free is a virtue overcoming many faults". No faults with what you have though.
The stock 150 can put out up to 10 lbs of top-end boost on a corvair, probably even more, and sooner, on the bigger engine. So a pop-off/wastegate routed back to the upstream side of the turbo is probably a good idea (can't be venting compressed A/F mixture into the engine compartment, ha ha!). Did I mention water injection?
Rick(wrench)

 

[Anonymous]

OK - let's back up a little.

Sizing the turbo requires a set of assumptions and calculations that were not part of my post. The turbo had already been chosen. The factory built the unit with the Carter, and I would start there. However, there was a suggestion that a Weber would be a better choice. Carter, Weber, SU, we all have an opinion. Personally, I am not a fan of SU's. The Weber DCOE is a very tunable, and probably flows better than the Carter. However, to repeat, I would start with the factory set-up as a baseline.

As for flow requirements and air/fuel ratio concerns, best practice would support a ratio in the 12.5 to 13 range. The Corvair had heat and preignition problems. Put that turbo on a 200 and I would expect it to run lean. As for what is the best carb, I was trying to indicate the flow potential of the engine. Will the turbo see it, will the compressor push it. The engineering is not available. But if a carb change is considered wouldn't it be reasonable to see what the flow potentials are and have enough carb to do the job. As an example I refer to the Buick 3.8 system that has been discussed at lenght on this board. Almost 20 years after Chevy tried this with the Corvair, Buick elected to use a 4V with progressive secondaries as the carb of choice. The secondary side was jetted to insure the correct air-fuel ratio at WOT. This was, in my opinion, an excellent way to manage temp and preignition issues at WOT.

As for the statement that my math was in error, let's review. CFM required under boost = CFM unboosted x pressure ratio.

CFM requirement is simply a matter of calculating how much air the air pump (engine) in question can consume. 200ci at 5000rpm is 2500 intake strokes per min. 200 x 2500 = cubic inches of air comsumed per minute at 100% VE. Simply divide by 1728 (cubic inch per cubic foot) to get CFM. So, simply put the formula is ((ci x (rpm/2)) / 1728). Muliply the answer by what ever efficiency ratio you want. But as I indicted, at 100% it is 289CFM.

Pressure Ratio is simply atmospheric pressure + boost pressure (I recommended 7 max) / atmospheric. Assume sea level standard day and we get 14.7 + 7 / 14.7, or 1.47.

289 x 1.47 = 425. At 5psi the number is 387.

If one wants to assume their turbo can push all air their engine is capable of consuming at 7 psi wouldn't it make sence to run a carb that can flow 425CFM?

In this regard, what is clear is that the original 145ci Corvair turbo either could not push the 307CFM possible at 7psi, so the flow requirement was less, or the Carter would flow the 307CFM. Without doing some reseacrch I wouldn't know. In any event, I don't view it as unreasonable to suggest that if one is going to build a system that can draw up to 425 cfm they should look at the possibility of finding a carb that will flow 425.

As for waste gates, I don't know if the Corvair used one or not. But I still support the comment that an engine that does not have an ECU to manage mixture and ignition advance throughout the boost range should not try to run more that 7 psi boost (1/2 bar). A waste gate is a very simple way to manage this need.

Guess that's it for now - Steve

 

[Anonymous]

Weber definitely better than the YF - I just don't have any $pares for them!
SU needs only time, clean plugs, and a few needles.
From MacInnes: single SU (est. 270 CFM) install makes 300 hp, 30 lbs. boost on 164" corvair using E flow.
Corvair = no waste gate. Gate is a great idea, they just wanted to keep the cost down so they used intake restriction and a big A/R to limit boost.
The intake flow is a restriction to max power and will definitely limit boost, but it's not as critical as NA, where with 5" Hg vacuum (carb too small) instead of (the preferred) 1.5" Hg WOT the intake charge weight is reduced to 88%, and even more power is lost if air correction isn't adjusted.
Air correction is the factor that blows up motors running @ WOT with carbs that are TOO big, and not jetted; since the venturi is running out of its design range (pressure differential not great enough), the automatic "richer-with-increasing-RPM" that is a natural function of all carburetors (since 1900?) the mixture will go lean-er than designed.
Emulsion tubes (generally speaking) adjust how much air is added, how "foamy" the mixture becomes as RPM (not throttle opening) changes; they change the "shape" of the A/F curve. Air correction trims the entire air volume available to the tube; changes the "slope" of the curve, but (since it's larger than the emulsion tube hole pattern until all holes are in play) it's only really effective at top revs.