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 how do you turbo 1977 728
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banjoman
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Posted - Nov 29 2007 :  15:53:13  Show Profile  Reply with Quote
I just bought a 1977 728 with a 4 barrl carb what type of turbo could use to boost the HP on this bmw
james

1986,524td 1977,728 1981, 300sd benz 1987,528e(for parts) 1996vw

scottie
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Posted - Dec 02 2007 :  18:41:04   View scottie's Photo Gallery  Show Profile  Visit scottie's Homepage  Send scottie an AOL message  Reply with Quote
That's an M20 motor, right?

Also you'd have to study how to fab up a turbo for carburation. I had a Yamaha bike that had a pressured carb system (4 side drafts) and I have also seen turbo systems where the carb was before the turbo compressor turbine. Interesting, but I know little about such setups.

Scottie Sharpe
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banjoman
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Posted - Dec 03 2007 :  08:58:40  Show Profile  Reply with Quote
i was told its a m30 put iam not shure if any one knows please let me know thats guys james

1986,524td 1977,728 1981, 300sd benz 1987,528e(for parts) 1996vw
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Alpina
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Posted - Dec 28 2007 :  05:24:06  Show Profile  Visit Alpina's Homepage  Reply with Quote
quote:
Originally posted by banjoman

I just bought a 1977 728 with a 4 barrl carb what type of turbo could use to boost the HP on this bmw james


IMO you dont,, just to expensive,, by a 745 or a M102 or M106

This is a M30B28 carb. version and is not well suited to get blown

try all other solutions than this -->> turbo+M30B28 CARB

Sveinbjorn Hrafnsson
Alpina Biturbo 346@507
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Timmo6
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268 Posts

Posted - Jan 06 2008 :  01:08:11  Show Profile  Reply with Quote
sure it can be done!
it even doesn't have to cost you alot as long as you keep boost under 8psi.
what compression ratio does a USspec m30b28 have? I am sure its not that high.
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Charles
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Posted - Jan 21 2008 :  12:37:28  Show Profile  Reply with Quote
I don't think there was ever a US-spec 728. But if I recall correctly, the CR was quite high (something like 9.0 or 9.3:1) and would not be easy to turbocharge and still run on pump gas. You could run low boost (4-5 psi) and premium fuel but the benefits may not be enough to make it worth the cost.

In general blow-through (turbo before carb) configurations work better with carbs (since fuel puddling in the piping and cold driveability tend to be problems with draw-through setups). You'd have to custom-make all the piping and a carb hat, and possibly bush the carb throttle shafts to prevent fuel/air mixture being forced out the ends. A book like "Turbochargers" by Hugh MacInnes is valuable reading for someone contemplating such a conversion.

Of course you could always convert to EFI like the 728i but that introduces a whole different set of problems (mostly wiring and fuel supply). And then you don't yet have enrichment while under boost...

By the time you get dished pistons, or a head with larger combustion chambers (like a 745i head), or a custom thick head gasket to drop the CR to 8:1 (or less if you aren't intercooling), you would indeed be better off getting a 745i complete engine assembly and just transplanting it.

Have you considered nitrous oxide (not sure what country you are in or if it's legal there)? You would be impressed with the torque from a 50 or 75 hp kit and it's much easier to install than a turbo conversion. Easier to blow up your engine too, if your tuner doesn't know exactly what he's doing...

Just my opinions.
-Charles
'81 745i

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crazyfaizy
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5 Posts

Posted - Apr 02 2009 :  22:46:50  Show Profile  Reply with Quote
.....hehehehe,,,id say go EFI(electronic fuel injection) on this one,,,try megasquirt converstion if money is an issue here

ofcourse ya gona have to source/fabricate many parts but its the right thing to do becasue you are doing it the right way,,,DONT BLOWthrought you dont have to deal with that stuff since efi is invented to overcome the problems of the carb

i havent seen so far what is called reliable boost from carbs,,,those are better for drag racing in general
only good side of turbocharging a carbed engine is that it runs cooler becasue of the nature ot atomonization the carbs gives but still its no were near as good as properly set efi system..

400hp is good for stock buttom end condition that the CR is somthing between 8:1 and 8:5...intercooler and hell of accurate tune....if thats your HP gaol
is it manual or automatic ?

if its an engine it can be forced fed

Edited by - crazyfaizy on Apr 02 2009 22:51:23
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