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Discussion Starter · #1 ·
Way off topic, but I know there's lots of turbo knowledge hanging around here so please forgive the question.

Have a '74 Chevy LUV with 1.8 liter OHC 4, 4 speed, in excellent mechanical condition: new head & valve job, possibly they rebuilt. Very strong engine. I wanted more power and upgraded from the junk stocker carb to a Weber downdraft. Got more power!

But, still not enough oomph for the mountains here, and thinking I over carbed some. I have a turbo off a Chrysler 2.2, maybe an Omni? I also have some exhaust headers that could be made to fit the Isuszu. So, what do ya think? Can I just bolt that Mopar turbo on the Suzie and call it good, or will I have to fiddle with the waste gate? Thinking I could lock it closed and hope for the best, but would like more intelligent advice than my backyard Goober droolings, don't want to scatter it.... Thanks!
 

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Discussion Starter · #3 ·
Thanks for reply, K204DR!

To be honest I forgot about that part, of boxing the carb. I remember the old Paxton/McCulloch superchargers did that. I was just considering hosing it right to the top of the carb and call it good, figuring it wouldn't leak all that much out of throttle shaft. Maybe I had better have the parts ready for a box if that doesn't work?

I'm pretty sure the littl 2.2 turbo has an integral wastegate, have to look, it's buried with some other parts. Sort of at the head scratching stage, whether to even bother. Sure enticing though! But thanks, 10 lbs will be my max!

jimmieD
 

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Discussion Starter · #5 ·
Thanks for the advice, and pics, maybe?

Poor little thing is pretty forlorn looking, but mechanically super. Prior owner, a county office, painted it bright chartreuse, I'm talking popsicle green haha! The shop guys were having their fun. I ended up buying it from the county at auction for $25, nobody bid because of paint and then a buddy of mine paid for it, said he owed me $25, so... the non-price was right! Then it turned out to be freshly rebuilt and meticulously maintained even though it looked Godawful!

So it's one of those can't lose things, whatever I do....
 

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How about a suck-through setup?
I've never turbo'd a petrol engine, but if you're sticking to low boost and no intercooler then it's the easiest solution.

Is that Chrysler turbo a T25? Post a pic and I can tell you. If so it's a very good size for a 1.8.
 

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suck-thru setups are more difficult to tune. it would also be nice to get a msd boost timing retard so you can back the timing off under boost. otherwise it will detonate and blow the pistons out the bottom.
I used to run a civic with turbo on a bone stock engine at 10psi, with a stock computer re-chipped and tuned.
since we're off topic: http://yota1man.tripod.com/vtecwagon/
theres nothing quite like a turbo on anything!
 

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Discussion Starter · #9 ·
Wow, that's one slick little ride!

I don't think I'll do the pull thru on the turbo, too hard to fab the intake etc. Probably just try to slam some more air to the carb. I'm only off stoch about 10%-15% or so, it's close. Just needs that little helping hand and I figure hey, I've got the turbo and some exhaust headers I can make work, why not?

I seem to recall it is a T25, I think the same one as on Dodge Omni and maybe the little Charger thing? Very common mid 80's Mopar 2.2L turbo.

The boost tming retard sounds like a good idea, I don't like the stock ignition anyway. It's points, and hard to get enough advance.

One of the really cool setups was on a few Blower Bentleys, with a combo setup. Supercharger engagement was on a switch, so most of the time you motored around naturally aspirated. When you wanted the big time just flip a switch, supercharger engages and winds up and oh baby, hang on!
 

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Hey JimmiD.... from my dealings at the track with the guys who like to play with the "cheep sleepers" They are haveing to put the carbs in a box to keep from weeping through the shaft seals, and blowing fuel backwards to the tank. 10psi of air in, and 7lbs of fuel pressure dont work. Now I think that one of the guys is running about 10 lbs of boost without a box, but he tweeked the carb with different float/spring, and is running higher fuel pressure. After seeing the different "cheep" setups, the box seemed the way to go and worked pretty darn good. I know that they make aftermarket blow through carbs for the turbo setups, but on a motor like yours you gonna have to order some pizza, have a few beers with the friends, and see what ya can fab up in the shop/garage. Good luck, and let us know what ya come up with.... later man

Oh, use the pizza boxes to mock up the blow box....LOL :rasta:
 

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Discussion Starter · #11 ·
Hmmm, I'm beginning to see how your little hobby developed hah!

Well, I did some head scratching, and I can't for the life of me see how a forced induction through carb throat would blow fuel back to the tank? Or how a box would fix the problem. Are you saying that the turbo pressure is blowing back through the main jet, into float bowl, then back past the carb inlet [float] valve to the tank? If the carb was in a box it doesn't seem that would change that relationship, and I can't think of any other way to blow thru to the tank.

Not to say it isn't possible, just that I'm too thick to get it.

I imagine I'll try to just shoot into the carb throat first, and if problems come up I'll see if your scenario is happening. I'm sure I have some sort of deep rooted problems: I also want to use two SMOG air pumps as superchargers on my 18hp Kohler twin and see what she'll do, on a minibike.....
 

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If you are adding say 7lbs of boost into the carb inlet, and you have 7lbs of fuel pressure, then there is no reason for the fuel to come out. And if the boost is higher, it will actually push back through the system. By building a pressure box, you have equal pressure inside and out so you dont have leaks on the shaft seals, but still have the problem with the fuel. Im not totaly sure how they are doing it, but I thought he said that it was a different float, and a stiffer float spring. I can ask him, but im sure that someone else here will have the answer..;) clear as mud aint it...LOL
 

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Oh, I do know that the FMU on my supercharger is increasing fuel psi 1to1 so you will have to think about that to keep from leaning out at boost...

I just like saying FMU.....sounds dirty :rasta:
 

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Discussion Starter · #14 ·
Hmmm, then from the explanation of float and spring, it is as I described: cramming in so much air that it makes its way all the way back through carb circuits into tank. Amazing!

Now I think of the other thread here, with the guy pondering a one way check valve in his fuel line. Might be just the thing for this application, with that one simple part eliminating the need to fab up the whole huffer box thing? Would still hit a boost limit, but no pressurized fuel return to tank.

Another thought is a boost pressure controlled fuel valve regulating a hi-output fuel pump's pressure? Low/no boost, 7 lbs, and rising up to slightly exceed whatever lbs positive pressure the boost becomes?

Third thought is a fuel return line, similar to injection, and higher pressure than needed. As boost rises less and less fuel returned to tank. May be confused on pressure/volume relations there though.
 

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The check valve wont work, you will still need to have atleast normal fuel pressure above what ever your boost is.. 7psi at 0 boost, 9 @ 2, 17 @ 10, etc, etc and you will need a way to ritchen the mix with boost also, like the FMU I was taking about.

You bring the pizza, ill get the :beer: and well get this project started.....then maby well both figure it out...LOL
 

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I tend to think Dougal's setup sounds easier; carb first, turbo then intake. Then you only have to worry about tuning the carb instead of trying to fight all the other stuff. Besides, wouldn't the gas droplets going through the turbine help to vaporize the fuel, and in turn give up more power, or at least better economy?
 

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I wonder what a backfire would be like on a setup like that??? Six feet of piping, and a intercooler full of hot gas vapor with ten psi of boost.....:nuke: ;)
 

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I tend to think Dougal's setup sounds easier; carb first, turbo then intake. Then you only have to worry about tuning the carb instead of trying to fight all the other stuff. Besides, wouldn't the gas droplets going through the turbine help to vaporize the fuel, and in turn give up more power, or at least better economy?
Just remember, I have not done this myself.:nuke:

But I think an intercooler on a suck-thru setup isn't a great idea. Throttle response would be quite spongey due to all that volume downstream of the throttle and you might have issues with fuel condensing out in the intercooler.
 

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Are you talking about a turbo setup like Accel used to sell for V8s back in the 70s? If you are, I believe that they were the least problematic setup and had excellent throttle response.
 

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Discussion Starter · #20 ·
Interesting stuff here, and a good mental exercise for minds that need to get out more! But I'm thinking the best cheap date approach might be to rig a waste gate to proper blowoff pressure and be done with it? That is just cram air down carb throat, let the leaks leak at throttle shafts, and control max boost.

Some mig work on the headers to fit turbo and a piece of drier duct aluminum hose and duct tape haha! Hey, never let it be said old JimmieD ain't in to some quality builds here.....:rasta:
 
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