Okay, I've done some thinking here (dangerous) and was wondering about turbo operation. . . here goes. If the turbo gets it's power from the exhaust, then the your backpressure from the turbo is equal to that of boost, correct? If you have 7 psi of boost, then you have at least 7 psi of back pressure. Am I correct in my thinking?


Back pressure is going to cause negitive effect on engine performance (reduced volumetric efficiency), unless I miss my guess here. Any thoughts about how to escape this nasty cycle? Is there a way to provide more positive pressure on the intake side without the way of building up backpressure on the exhaust?


Or, am I all cracked up on my thinking?Edited by: knkreb

The 6.5 turbo is sized small to get Boost at low-rpm condition - off-idle and up - where a working truck needs the power. This is referred to as 'driveability'.


At upper rpms, the small turbine becomes a bottleneck.


A wastegate can be used to limit Boost to safe levels, and relieve excess back-pressure due to small turbine.


Larger turbo can increase upper rpm power and reduce back-pressure, but low-end power suffers - black smoke and low power until turbine spools up, called 'turbo-lag'.


Variable-vane technology can be used to get both low-end and upper-end power - the new F**d 6.0 uses an electronic-controlled VV turbo, according to my sources.


Early attempts were centrifugal, where vanes were aggressive at low rpm, reducing 'pitch' as rpm increased to allow for high rpm flow.


So, yeah - your thinking is within specs.http://www.dieselplace.com/forum/smileys/Wink.gif


p.s. - EBP vs Boost is not direct 1:1 ratio - at ~10psi Boost , EBP can peg a 20psi gageEdited by: gmctd

Its called a supercharger.

Superchargers are not exhaust-turbine driven.

Yes a turbo will have some negative effects in the sense that they create backpressure. But the general principle is that they take energy that already exists in the exhaust system and then uses that energy to compress air for the inlet charge. General rule I've heard (and of course this varies hugely) is that for every 100 hp you gain with a turbo you have to spend about 3 hp.

Think about a turbo as an extra muffler or catalytic converter, except it actually does something besides clog your exhaust. http://www.dieselplace.com/forum/smileys/Big Smile.gif

Turbos = good!

What I am most interested in seeing is how much better utilized that BP will be with a balanced exhaust and the stock turbo ( the van/hummer set-up).


Ted, can you think of a smaller turbo off hand that might fit the 6.5 in a twin configuration? Something I might find at the salvage yard? I am thinking a small displacement gasoline engine turbine.

Any thoughts about how to escape this nasty cycle? Is there a way to provide more positive pressure on the intake side without the way of building up backpressure on the exhaust?





It called a Supercharger.








Superchargers are not exhaust-turbine driven.








I never said anything about a Supercharger being exhaust driven. You posed a question, and I answered it. A Supercharger, since it does not use the exhaust at all to increase intake air volume is one way to, "escape this nasty cycle". Edited by: Juancho

Yeah, a supercharged 6.5/6.2 with an intercooler and headers would be a whole other animal. Do they make superchargers for the 1500-2500 rpm range?

Superchargers are not as efficient at making boost as turbos are. Lot of rotating mass and they spin about 8-10x crank speed. For such a relatively low RPM/high volume app, you would have to increase the ratio even more to make it effective.

There is a 400 HP supercharged 6.5l called the tigershark. They also sell a drop in kit that includes supercharger+ intercooler +++ Pretty darn flat torque curve!!


http://www.marinediesel.nu/md_site.html

There is a 400 HP supercharged 6.5l called the tigershark. They also sell a drop in kit that includes supercharger+ intercooler +++ Pretty darn flat torque curve!!


http://www.marinediesel.nu/md_site.html








I want one! I have to replace the motor in my '95 Burb anyway, might as well replace it with this. LOL!http://www.dieselplace.com/forum/smileys/HiHi.gifEdited by: Juancho

That's a mechanical pump, get ready for some conversions to make it work. What was the price, they did say custom hand built to order.

I think the price was 10K (not confirmed, saw it somewhere else) for the entire drop in motor (without conversion issues for all you electronic guys...), which IIRC is a ton lower than Penninsulars 400HP twin Turbo (16k??).

I was just joking. I can't even afford the $2000 I need for a reman block, but I can still dream. They actually had a couple other less aggressive motors, which might be a little cheaper. Sure would be nice.


Heck, I would even settle for the Stingray. I don't need the full blown Tigershark.http://www.dieselplace.com/forum/smileys/Big Smile.gifEdited by: Juancho

ahh, whats life without a little dreaming...a couple of years ago I was dreaming of being where I am at now, so time to upgrade the dreams!

OK, how is a ball bearing turbo different than a normal turbo, and whats the advantage for us?

The turbos we have rotate on brass bushings and couldn't make it happen without a constant supply of oil to reduce friction. Ball bearing turbos have less resistance so they spool up faster. The ATS ball bearing for the ford and dodge is $2500.

$2500 real $$'s?? ouch. Thats a BIT steep for my blood!! Think I'll just slap my little GM-4 in front of the penninsular- THAT will solve my slow spooling!!

Here the hummer exhaust/turbo set-up. should be the same as the van.


http://www.dieselplace.com/forum/uploads/B8D_EngineCrateRear.jpg


and the turbo.


http://www.dieselplace.com/forum/uploads/DD1_NewEngine28.jpg