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if i have this engine, can i add a turbo to it?


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Guest Anonymous

45 dcoe, 300 cam, headers, ported head?

i want to go turbo, but my ignorance is that if i can put a turbo on a non fuel injected car?

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Guest Anonymous

pressurizing carbs is a major PITA (only exceeded by putting the carb upstream of the turbo).

Your compression ratio is not a problem (look at all the modern turbos running high compression engines), you just need less boost to get to your HP target, but you want to go back to a stock cam.

If you're starting, buy Corky Bell's book "Maximum Boost" and read it three times. You'll have a lot more hard information to go on then.

Cheers!

John N

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Guest Anonymous

Very true, but remember that the new engines are computer controlled, taking a lot of guess work out of boost amounts. With a high compression engine on an old carb car, you can easily overboost by accident.

Turbo+Carbs=PITA (IMO) But I may attempt it myself one day just for the hell of it! :-)

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Guest Anonymous

pressurizing carbs is a major PITA (only exceeded by putting the carb upstream of the turbo).

Your compression ratio is not a problem (look at all the modern turbos running high compression engines), you just need less boost to get to your HP target, but you want to go back to a stock cam.

If you're starting, buy Corky Bell's book "Maximum Boost" and read it three times. You'll have a lot more hard information to go on then.

Cheers!

John N

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Guest Anonymous

Throw in a WB-O2 sensor so you have some idea of what your mixture is under boost and you can do a very good job of controlling things.

The only possible reason for trying to supercharge/turbocharge a carb'd car would be for some historic reason. Otherwise, you'd gotta be nuts to even try.

Cheers!

John N

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Guest Anonymous

Despite proper ECUs, a high CR engine will

pre-ignite at lower boost when force fed then a low

CR engine. Good ECUs only let you run closer to

the edge... So if emissions and fuel consumption

are less of an issue, do lower the CR. And indeed

take a fairly stock cam, long duration cams have to

much overlap time between inlet and exhaust

valves and your boost will be blown into the

exhaust before having done the bussiness.

Take a look at the forced induction board on

roadfly, they can help you further. You're not the

first.

Good luck,

Hugo

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Guest Anonymous

need as much boost. When I pushed the numbers, an engine with 9.5:1 pistons only needs 5-6 PSI of boost to make 200-210 HP. If you take the extreme (6.9:1 pistons used in the 2002 Turbo, you need >14 PSI).

With high compression pistons, you also don't have crappy torque and horsepower while you're waiting for the boost to come up. You're absolutely right about the cams, stay with stock.

John N

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Guest Anonymous

but you will NEVER make as much power in the long run. I do agree that it is probably much more drivable with 9.5:1, but i still think 210 hp is optomistic at 6 psi. very optomistic. -Reid

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Guest Anonymous

(given a fixed displacement), is determined by how much fuel/air (at the proper mixture of course) you can pack into the cylinder, and how tightly you can squeeze that mixture before you ignite it.

For the purposes of this, we'll assume the efficiency of the flame wall is the same for low and high compression engines (e.g. BMW has done a competent job of designing both sets of pistons). [This is a very conservative assumption, since a domed piston gives you better control of the squish area and should be more efficient than flat-tops or dished pistons.] Lets also hold the timing advance constant between the two engines.

The limiting factor now becomes how much fuel/air you can pack into the cylinder and squeeze it before you get an erratic flame wall (pre-ignition = knock). If you now compare at a low compression ration/high boost verses a high compression/lower boost setup, the temperature of the charge is the factor that will determine how soon you get the erratic flame-wall (the hotter the charge, the sooner you get erratic flame-wall behavior).

Simply said, lower boost will give you a cooler charge which means that with everything else equal, you can cram more in there before you start to slag your pistons.

Cheers!

John N

BTW: If you use the rough formula that Boosted HP = (1+boost/14.7)*NA HP, and use 150 as the upper limit of 150 HP for a 9.5:1 NA engine, you get to 210 HP pretty easily

The primary factor that is going to determin this (given equally well designed pistons)

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Guest Anonymous

I've personally seen a 2.2L engine produce 215hp at 7psi with a 9.88:1 CR. Large exhaust wheel on the turbocharger was great for flow but had poor spool, the low end was horrid with the 8.0:1 he was previously running. Car now makes decent power until boost comes on and then runs like a bat out of hell with boost right to the 6100rpm rev limiter. He hasn't dyno'd the car since upping the boost to 16psi, but from being in the car at both settings I can tell you it's quite insane. Not nearly as wild as my chryco at 24psi :) Mind you I have more displacement and a lighter vehicle ;)

But in my opinion, lower boost with a higher CR and better flowing intake and exhaust tract is a much better idea. Less wear on turbocharger bearings and seals from running at the upper end of the map, no intercooler lines coming off at 22psi or having a wastegate can rupture the diaphragm. A much better setup in my opinion

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Guest Anonymous

why bother with turbos or compressors? Just up the CR a little more and you reach the same power with an NA engine as with a lower CR turboed engine.

But since that is not the case, I still believe a lower CR with higher boost will allow more air/fuel to be fed into the engine before it starts detonating. I do agree that the mixture temperature reduces the efficiency, but intercooling can solve a big part of that problem.

Besides all the theory, why do Saab LPT (low pressure turbos, with high CR) produce less PH then the HPTs (high pressure turbos), lower CR? They have a considerable amount of experience...

Regards,

Hugo

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Guest Anonymous

...running 23 psi on a 7:1 Volvo B21FT, until that boost comes on, it's a real dog. And you have to tie wrap the intercooler endtanks on to keep them from blasting off.

Running a low-pressure turbo on a higher-comp engine is a smooth, relatively trouble-free move. Small turbo = quick spool, great response. No intercooler to have to make room for and plumb. Just have to consider cams, really...

Marty

'73 malaga 02

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Guest Anonymous

boost, and HP for the two engines? Without some harder numbers, saying one made 'more HP' isn't very useful.

Cheers!

John N

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