i would like some help with my questions. Question 1: Can you supercharge and turbocharge an engine at the same time? And what would be the problems? Question 2: Could you super charge a diesel engine, and what would be the problems with that?

 

Yes the old Detroit 6V and 8V Series had both. ... Detroit Diesel Series 71 - Wikipedia, the free encyclopedia

I'm sure someone else will chime in w/ more info.

 

Well, actually the Detroit had both, but the Blower was bypassed once the turbo was up on boost. The detriot needs forced induction to run at all(as it's a 2cyl engine), but once the turbo was added to actually add BOOST instead of just 1:1 blower they added a bypass valve so the blower was not used once boost was achieved.

No other diesel requires a blower to run, but I have seen one that had a whipple charger installed. I don't know any of the information on it.

I've seen both on gas engines also. Then guys figured it was easier to put two small turbos instead of one big one, then you have best of both, boost and very little lag as the little turbos build boost quickly.

 

Yes, you can, but i would think it would become costly and complicated real quick. it also makes a difference what you're trying to do this to.
If it's a DI diesel, then all you really have to worry about is head studs, valve springs, fuel delivery, exhaust gas temperatures, exhaust and intake systems, intercooling...
If it's a gasser, you're looking at all of that plus you dont want predetonation. that kills parts fast. Intercooling and boost regulation become key here.
Also, you'll need to upgrade injectors to keep proper fuel/air mixes. you may also need a cam ground specifically for the application.
It gets very complicated with non-direct injection vehicles.
all of that aside, it can be done.
Popular rumor says that Carol Shelby (founder: shelby cars) drove a Cobra 427 that was twin turbo into a supercharger, and put out over 1100 hp. I've never confirmed this, but knowing the shelby legend, i dont hesitate to believe it.

 

While complicated to design and construct, I see some potential advantages for engines that are to receive "incredible" amounts of boost. The main one would be that the supercharger, driven by a belt, could provide boost immediately off idle giving a very large turbo the opportunity to spool up, and upon the turbo reaching the same pressure over atmosphere as the supercharger, a valve would switch from sc to tc and continue increasing boost as the rpm's increase.

One could also do this with a small turbo and a large turbo.

If the complexity is not for you an even better option is a variable-vane turbocharger, whereas the vanes on the turbine (exhaust side) are adjustable based on a vaccum signal therefore at least to some degree you can adjust it for whatever RPM range your engine is at, making for a smoother increase in boost across the usable RPM band. This type of turbo also reduces the necessary size of a blow-off valve to something more smaller, thus more common and less costly.

It depends a lot on the engine's effective RPM range as well as it's overall displacement. With a smaller engine, having boost early on would give that engine "pep" for acceleration, towing, hauling and so on. Another method is to choose the biggest engine you can fit and turbocharge that with much larger turbos - while there will be more turbo lag, you won't care that much since you have the low-RPM displacement to make up for it. After all, you don't hear too many people complaining that their 460 has no "grunt" off idle. Add a turbo to an engine of that size and you've got more grunt than stock tires can handle anyway.

I've heard about that Shelby folklore as well, though never found a picture anywhere, book or web. But, I wouldn't be surprised if it existed somewhere in automotive history simply because Shelby is.. well.. Shelby

But it seems many are impressed with 1000 HP, and that's not extremely difficult to build an engine for, especially with a turbocharger. The cheapest, easiest way to achieve this is to build out a 500cid engine and turbocharge it into the upper end of the 2-bar range in boost.

If the static C/R is reasonable, and the RPMs are reasonable (i.e. street-worthy), that's not an unreasonable goal.

 

i bet the best place to start is with a diesel 350 block(thick cylender walls) and convert it to gas i dont think id ever build a turbocharged and supercharged engine(tooo expensive)

 

Diesel engines are by far more durable than a gasoline engine, because they have to endure more cylinder pressure. Diesels typically have an 18:1 c/r whereas gasoline engines these days are typically 10:1, less if the engine is much older.

If you remember during the gas crunch of the 70's, several manufacturers brought out diesel cars - GM being probably the most obvious - and their "diesel 350" was really a piece of crap and had tremendous reliability issues, BUT if you used different, shorter rods to lower the static compression into the range suitable for gasoline, those blocks were much stronger than the "ordinary" gasoline 350 (which is pretty durable since chevy guys build those things well into the 700HP range without too much of a problem - and with a diesel block imagine how far you could go...).

The one thing to take into consideration is that diesel blocks, for a given displacement, weigh a heck of a lot more than a gasoline engine with the same displacement, and that extra weight your car/truck has to hump around reduces the overall efficiency.

Obviously 300HP in a 2800lb car is more enjoyable to use than 300HP in a 7500lb pickup, just because of the weight difference.

This is also the same reason why many amatuer drag racers strip their daily drivers of 1/2 their interior, spare tire, bumpers, and other easy-to-remove items before going down the 1/4 mile competing with their friends. Upon completion of the day of racing, they're in the parking lot putting their car back together for the drive home

The reverse way of looking at this is say the diesel 350 of yesteryear weighs 200lbs more than the chevy gasoline 350 - if that's installed in a 5500lb pickup, does 200lbs really make that much of a difference? Yes, but the percentage is very small. When acceleration truly matters, leave the overloaded bed-mounted toolbox home. I know mine probably weighs about 500lbs lol.

I received a lot of comments from various friends when I decided years ago to build a twin-turbo 500cid stroker for my F350 crewcab. "You're adding so much weight!" and "That's going to be horrible to take corners in due to the extra weight" and "With more weight you're going to need more power than you think" and comments of that kind.

The math is simple.. an 8% increase in weight to gain 300% in horsepower? That's an incredible ratio if you ask me, so what I'm potentially gaining grossly exceeds the weight cost.

And to the guy who suggested the extra weight would "limit my cornering ability" has obviously never driven an F350 crewcab. It's like pitching a moody, bloated elephant around a tree. I don't think added a bag of peanuts to that moodly, bloated elephant is going to make a difference in perceived handling, even though mathematically one could easily prove it would.

 

thanks for the info frederic man i got to say you are one of the most educated people ive met on FTE when it comes to engine and trucks alot better than those dumb ***** at the 2004-2008 f-150 forum. keep up the good work sharing your knowledge with people like me who are learning more about engines every day thanks again

 

Thank you, but don't give me too much credit. I'm like everyone else here... a hobbiest interested in certain things, experimented here and there, and certainly blew up my share of perfectly good engines trying to apply "sound" theories of mine that turned out not to be even remotely close.

But, it's fun none-the-less, right?

 

I completely agree. Kind of on the same topic, what about putting a large and small turbo setup similar to what Ford did with the '08 superduty on a 460?