i've always wondered how the turbo's from a semi/dump truck were different then the big ones in fast gas cars. i'd assume you'd need smaller bearings, but what else? does anyone know how much boost they put out? my friend is rebuilding his 460BB pretty soon and i'm sure (if it could work) he could put a semi turbo on there real cheap.
is it possible?

 

Not too sure, but I'd assume they are for HUGE displacement motors. Aren't most Semi's diesel?

Doubt a turbo for a 6-cly 20 liter engine would really do much for one of us here.

 

Actually, diesel turbos usually have HUGE bearings, becauase they regularly see copious amounts of boost. But most big rig/semi turbos are bigger than most any gas motor can use. I have personally looked into putting a Holset turbo on my camaro, they are the turbos that come on Cummins powered Dodge trucks.

 

they are huge engines, but the turbos are the size of one you'd see on a fast street car.
his truck makes enough tq downlow so i figured it might be possible. so i guess it wouldn't even work if he got a turbo off an old dodge and kept the waste gate open?

 

my fault, i meant to write that it would need smaller bearings.

 

Why would it need smaller bearings? Please explain what you mean, as I'm sure it makes sense to you, I'm just not getting it. Remeber, diesel turbos are speced to provide large amounts of boost and airflow. A turbo that feeds a 5.9L Cummins might be very efficient on a gas engine. I wish Holset would advertise A/R ratios, trims, etc. but they are pretty hush-hush on that subject.

 

Most diesel motors have huge strokes that help spin the turbo right??

Otherwise the turbo is coming off my '94 GMC bob truck! lol

 

i don't know alot about turbos, but generally figured smaller bearings would reduce friction, but they wouldn't fit anyways.

but are you saying that it is possible to use one from the dodge trucks? i can't find anyspecs on them, but it would be cool to get one cheap from a junk yard.

 

you would be hard pressed to find ANY gasoline engine that could spin a semi turbo to put out any useful amount of boost. the size and air displacement of an average semi turbo is far beyond that of anything you could even imagine on a gasoline car or truck. look at it this way, semi's have enourmous intakes and piping, meaning very little restriction (boost pressure is actually the restriction of airflow, not the amount of air flowing tho they are somewhat related), however even with such a small amount of restriction, some of the higher grade, more performance oriented turbo's are capable of cramming 150+++ psi into a diesels intake system. i say 150+++ and not just a capped off number because 150 is for the most part the most boost i have seen from a single diesle turbo, but only because that is all that the engine could handle (or more reasonably, all that the driver cared to attempt to handle ), not because that is all the turbo is capable of. tho most of the trucks running that much boost from a turbo are actually quad turbo engines... 2 main turbos putting up to 300 psi or more (300 is simply the highest ive seen, who knows if someone is putting more into an engine) and the other 2 turbo's i imagine are helping to spool the 2 main turbo's. that all sounds absolutly rediculus but its far from fiction.

there are 2 main reasons diesel engines are able to spool turbo's of this caliber. one has already been stated, the engines huge displacement, and the other is the amount of combustion pressure diesel engines have. most of the time, the combustion needs more room to expand then it has in the engine, so when the piston nears bottom dead center on the power stroke and the exhause valve starts to open a lot of whats left over of that pressure exits through the exhaust. this is part of the reason deisels have EGT's in the thousands rather than in the hundresds like gasoline cars do. tho gasoline engines also have an exsessive amount of combustion and some does escape when the exhaust valve opens, it is not even comparable to a diesel.

this all applies to the smaller diesel engines like powerstrokes, cummins, duramax and so forth, however, it is not as extreme because of the much smaller displacement of these smaller engines. wether or not you could effectively use a turbo off of a smaller diesel on a gasilone car, i do not no, tho i highly recomend you dont waste time and money trying it, no matter how cheap, because there is nothing like a gasoline car turbo for a gasoline car, thats why they make them after all.

 

i was gonna suggest it to him if if was cheap and practical. but i guess your saying it isn't? cause even if the cummins was too much you could always get one from a saab or something.

 

You likely won't find ANY numbers from a Dodge Cummins turbo. The reason being is because Holset does not advertise those specs. Wheel trim, A/R, lb/min, nothing. Of course, there are estimates, but nothing official. DSMs are begining to use the Holsets in some of the wilder setups, most utilizing an HX35, with a few stroked 2.4s trying the HX40, a popular upgrade for the Cummins trucks. I have a friend in my home town who has done some work to his Dodge, and is using the factory turbo, with it pushing well over 70 psi. He claims over 500 rwhp, without the use of any nitrous or propane. Holsets are incredibly rugged, and are considered the cream of the crop for turbos in Europe. The bearings are incredible, and they are capable of flowing MASSIVE amounts of air. I think that with the right amount of research, the right Holset could be located that would work suprisingly well on an LS1. Are there better turbos out there? Absolutely. But they are an option.

 

70? i heard that 50 was the limit for the stock hx35
but at any rate if you think of the turbo in terms of its limits vs. where its at, i guess the reliability isn't so suprising. that still insane though.

 

I never said that what he was doing made sense. But he is doing it. And it's still the stock turbo. He has upgraded his intercooler, fuel pump, etc, but has left the turbo stock.