superchargeing a 2.5 - Moparchat

rockyrunner99 · #1 08-15-2001, 10:57 PM

I am thinking about supercharging my dodge shadow that has a 2.5 TBI.
I know that there was a turbo option so the engine can handle it right. I would like
some help with things like the compression ratio though, I think they may have lowered
it slightly in the turbos is this true? and what was the boost from the factory?
how much boost could I safely run? does anyone have any ideaas of where I could
get a supercharger? I was thinking from a junk yard. off something like a bonneville,
or grand prix, or buick reagal. I am looking for a centrifugal type not a roots type, I am
not sure what those cars have, so if you could help me find one. thanks

pishta · #2 08-16-2001, 12:08 AM

I believe the Ford SC coupes and the Bonnevilles both have the roots type. I saw one at a swap meet and it was tiny. About as big as a Quaker Oats can. It said 3.8 on it, so I would guess it would work on a 2.5 eh, with a smaller pulley.

curious · #3 08-16-2001, 01:20 AM

Quote:

Originally posted by pishta
I believe the Ford SC coupes and the Bonnevilles both have the roots type. I saw one at a swap meet and it was tiny. About as big as a Quaker Oats can. It said 3.8 on it, so I would guess it would work on a 2.5 eh, with a smaller pulley.

sorry pishta bu you have that bass ackwards. my dad has a 3.8L gtx w/the m90 eaton blower. you increase out put with smaller pullies Ex: 3" pulley=more boost than 4". you ll prolly have to work a bit with the computers and intake. i believe these s/c s have a waste gate or blow off vavle. they produce no boost at steady throttle position kinda like a turbo. this helps save gas mileage. also makes the use of cheaper gas safe for cruising. all this is tied into the throttle position sensor. it was designed to be ultra efficient. it uses 1/4 of 1 hp to roatae under steady throttle (no boost)

curious · #4 08-16-2001, 01:26 AM

i just noticed you want a centrifugual blower. there is no oem application even clos to what you are looking for. but there is a lot of aftermarket places.

pishta · #5 08-16-2001, 10:16 AM

Curious, I meant the lower pulley...ha ha, you got me! You are right, smaller pulley means faster spool speed, what was I thinking. I think that is the same charger that is on the Mercedes K cars, is that correct? And if you wanted a factory centrifugal blower, the Corvair and the 57 Fords had those types of blowers.

curious · #6 08-16-2001, 12:08 PM

ok i kinda figured maybe thats what your getting at. i dont know about the corvairs but yes i do remember factory installed paxtons. i wouldnt waste my time though. first s/c ers usually will need a rebuild and second and more inportant is the fact they re rare and if you found one your much better off selling it. you could prolly go with a mild pro charger. it might cost $2500 but you can get a intercooler.

goose · #7 08-16-2001, 12:12 PM

I would go ahead and get a set of the factory turbo pistons, you'll need them to run any appreciable boost safely. They are lower compression and also heavier duty I believe. With these pistons you could probably run up to about 10 PSI w/o an intercooler.

rockyrunner99 · #8 08-16-2001, 04:26 PM

I beleive that with a supercharger you do not need an intercooler. those are used in turbos to cool the air. It needs to be cooled because the turbo is driven by the hot exhaust gases. a supercharger is driven by a belt and is not hot. right?

curious · #9 08-16-2001, 06:18 PM

well if i read right you live in Ionia. if i ever should happen to meet up to you ill have to show you how hot a s/c "doesnt get" give you $5 to set your hand there for 30 seconds at idle. bet you cant do it. you dont need a intercooler but its a good idea. those eatons get so hot that people will come up to talk and lean on a fender and back away because they burn them self- im serious. im sure most s/c s are hot. intercoolers are cheep and would have came with the turbo models. so do your self a favor and see if you can find a good intercooler. somewhere i read the intake air temp approaches 270*+. this is on the oem applications like bonnevilles.

goose · #10 08-17-2001, 03:46 PM

What makes the air hotter is compressing it. The outlet temperature from any kind of supercharger depends only on the boost pressure you are putting out. Of course there are some efficiencies to factor into the equation but the pressure is the main culprit. That's how a diesel engine works actually; the CR is usually in the 20:1 range and when you compress the air that much it gets so hot that it lights off the fuel, no spark needed.