One more Mod to add to the list http://cgi.ebay.com/ebaymotors/Exhau...62998222QQrdZ1Any one have these yet ?

 

Added to my list! Way down the end.

 

i wonder if with the longer tubing especially from a front cylinder if there would be any "dead" spots in the exhuast pulses that could hinder the turbo? just a thought. i am guessing that there is no noticable or measureable difference but something to ponder.

 

yep, they are on my list. going on the engine when i do the race build. i will have them ceramic coated inside and out from the headers to downpipe. god i wish i was rich...

 

Probably. But "dead spots" would not be as severe as the ones caused by the stock manifolds. That is why you hear exhaust flutter when you put on an aftermarket exhaust.

The flutter is caused by two factors - first, the firing orders that V8 engines use end up with uneven exhaust pulses on each bank. Overall, you get one power stroke every 90 degrees of crankshaft rotation, but if you look at just one bank, the pulses are not evenly spaced.

The uneven exhaust pulses are only made worse by reason number 2 - the "log" type exhaust manifold that dumps all the pulses directly into a chamber that connects them all together. It sucks, to say the least.

THEN, you add insult to injury by just cramming the two uppipes together and into the turbine. They combine to cause severe pulsations in exhaust pressure - a couple of exhaust pulses trying to squeeze through the turbo at the same time, followed by a dead spot.

Gassers dumped 'log' manifold decades ago because they severely hindered exhaust flow. I've often wondered why no one made replacements for the crappy stock manifolds. Well, now someone does.

Uh, oh. My PMS is flaring up again.

 

I am a firm believer in this: If the firing order and exhaust manifold were designed differently from the beginning so that all exhaust pulses arrived at the turbine sequentially timed nice and evenly, not all unevenly and making a lot of flutter, that would be worth about 2 mpg and 50 HP without having to add any fuel to make it.
IMO, that's why the smaller displacement Cummins is able to make so much more power. It doesn't have to battle against it's own ineffeciencies.

 

Interesting Kwik...this guy wants $1000 for his PSD headers (click HERE) so
with what u said these may not give u the gains your suggesting. The sets from DI that MAevans posted look like the best ones for HP gains.
Nut

 

I agree completely about exhaust design inefficiency on the 7.3. Big pipes after the turbo only address turbine exhaust - they don't address the mess before the turbine.

I'm sure a turbo-diesel designer will swear up and down that exhaust design makes little difference. They'll tell you gassers need fancy exhaust, turbos don't.

But exhaust flow, getting the burnt gasses OUT is just as important with a turbo-charged engine as with a gasser. Then there is the issue Kwik brought up - the effect of uneven gas flow and pulsating pressure on the exhaust turbine.

All the engineering effort that has been placed on head design, injector and pump designs, and zillions of sensors feeding data to fancy computer controls in order to improve efficiency and reduce emissions has made tremendous strides.

But turbo-diesel designers have their heads up their computer-obsessed a$$e$ when they should be looking up the exhaust pipe for "hidden" power and efficiency.

I don't know if they could recover 50hp (20% on a stock 7.3), but one of the secrets to getting diesels to pass EPA requirements is pumping LOTS of air through them. If changing the pre-turbo exhaust design resulted in a 10% improvement in turbine-driving efficiency, that would save them (and especially us) from more costly, complicated, and failure-prone systems like the variable vane turbos in the 6.0.

 

Hey, Nut. The manifolds in your link look MUCH better than the stock crap on these trucks. AND, being made of cast iron, are likely to live longer than the tubing headers made by DI.

But they are like the halfway efforts made by Chevy and Ford in the '60s - the "cast iron headers" that were partway between log manifolds and tuned headers.

They have a nice, smooth design that separates the exhaust ports and allows for much smoother flow. I will guess they would provide a noticeable improvement over stock.

I doubt they would work as well as the DI headers. If you look at the DI design, they actually combine pairs of primary tubes into a "tri-y" design. Very nice.

I'd like to thank them for designing them by ordering a set - but I just don't have an extra thousand bucks lying around right now. Maybe, MAYBE if my June bonus from profit sharing is big enough, I could consider it. I'll probably have to put it into my wretched house, though. It wants a new furnace/AC system.

 

From what I understand on researching turbo's, the small exhuast is to keep the air flow high to help turbine speed, to big of a pipe to the turbo and the turbo ain't worth a flip, But you would think a log manifold is outdated, the old 855 cummins turbo worked better than cat and detroit with the log manifolds becaust all the cylinders dumping into the manifold was broke up, not like the headers are though. They do look like you would get alot better turbo response.

 

It isn't the small exhaust that is the problem, it is the restrictions caused by bad design that prevents the exhaust from flowing as it should.

It is the flow of hot, pressurized gas over the turbine that drives it. If you maintain the pressure (controlled by the A/R ratio of the turbine housing) and improve gas flow, you should see an increase in turbine efficiency.

Well, time will tell. As more people start to change the pre-turbo exhaust to something resembling an efficient design, we'll start getting feedback.

Anyone that installs either of these systems, PLEASE let us know how they work!!

 

Interesting info Arn!
Nut