You can go to 3" right after the flex, but I figure if I'm going that far, why not get the piece of 3" flex off eBay ($27) and another 3" elbow (which I already have) and go all the way to the turbo outlet?

I knocked off one of the other projects that needed to be completed first before I tackle this. I'll knock off another one or two tomorrow - then when the flex I ordered from eBay gets here next week I should be just about ready to go ahead with this...

I would recommend going the extra $50 and putting in a 3" downpipe if your exhaust is already shot. The stock "flex" pipe is a POS design in my opinion.

3" 90* mandrel-$10ish x2
3" flex pipe-$30ish

Ditto - for 40-50 bucks it seems silly to stop short of doing the whole job...

Every bend is a restriction, even mandrel bent ones...



A true 2.5" system is more than enough to support 400 HP on a 3l motor, no matter the fuel...


Fuel goes in, gets burned, goes out.

OK, if you want to play the semantics game let's get really techincal. I should have said "no additional constriction". All bends restrict airflow in the sense that the change in direction slows down the air stream and interrupts the laminar flow. Thanks for pointing out the obvious. The point you're having a hard time accepting is that you were wrong about the bends being a significant constriction due to the diameter reduction from non-mandrel bends. But that isn't the case - like I said, they aren't mandrel bends, but they are about as close as you're going to get without a mandrel bending machine.

Sorry dude, but you are wrong. A single 2.5" exhaust isn't even enough for a 400 HP gasoline engine (Mr. Vissard's formulas prove it - 2.2cfm x 400HP=880cfm and 880cfm/115cfm per square inch = 7.65 square inches - slightly more than the area of a 3" exhaust). Even if it were enough for a gasser it would still definitely NOT be adequate on a diesel. I'd be extremely surprised if you could even get a 3L diesel's output up to 400 HP if you're choking the exhaust down to 2.5".

Even the 6.9 Fords (170 HP) came with an exhaust system comprised of two 2.25" down pipes that Y in to a single 2.5" - and it SUCKED!I know they are over twice the displacement of the 3L, but they are also less than half the 400HP 3L you refer to. Simply upsizing the downpipes to 2.5" and everything after the Y to 3" made a HUGE difference on my first F250 diesel, and it wasn't even a turbo! Just changing the exhaust I picked up around 10-15 HP.

My current F250 with the aftermarket Banks turbo system has two 2.5" downpipes to a 3" Y up-pipe, and a 3" pipe from the turbo back, and that's way too restrictive IMO. Even though the non-wastegated turbo only makes around 8 PSI at 3000 RPMs with your foot on the floor and pulling a load uphill. I wish there were room between the bellhousing and firewall to put a 4" pipe from the turbo back and I'd do that upgrade in a hearbeat.

Unfortunately you have to "roll" the tranny tunnel seam on the firewall just to get the 3" in there, so a 4" pipe just ain't in the cards...

We won't have to worry about it since no one is anywhere close to that power...


A true 2.5" exhaust will be more than fine for any power level that can be achieved with the timing chain eaters or the OM617's.... Which is what I've been saying all along..

Not semantics, fact.



Nope, you are. On a NA gasoline burner, a 3" pipe wouldn't be sufficient. On a intercooled, turbocharged 3 or 4 liter engine, its more than fine. Look at anu Grand National, Ford SVO, ect that makes power. A large Ford V8 TD engine that you pappen to used to mess with isn't valid in either discussion.

SO THESE FLEXPIPES THAT ARE ON EBAY CLAMP TO THE TURBO EXHAUST OUTLET? IF THEY DO THEN YA ILL BUY IT, AND EVERYTHING FROM THERE ON WILL BE 3 INCH PIPING.

Flexpipe = horse shat.


PS

Your caps lock called, it needs a rest...

based on what u said a long time ago, an engine is an engine . "Not semantics, fact."

That makes no sense whatsoever. A 3" is too small for an NA gasoline engine, but its plenty big enough for the same engine with a turbo and intercooler pumping 2x-3x as much exhaust volume? What have you been smoking?

Also with the SVO, and the Grand National you are still talking about gassers, and as I have stated before - they NEED some back-pressure to make good power. DIESELS DO NOT! Diesels run most efficiently and make the most power with no back-pressure at all. What you don't seem to be "getting" is that although a lot of the mechanical components are similar, the operating principles behind the two different kinds of motors are totally different.

As Eric pointed out, YOU are the one that said gas or diesel, an engine is an engine (totally untrue, but its still what you said), so the same principles that apply to the IDI Ford V8 Turbodiesel apply to the 3.0L IDI Mercedes Turbodiesel. Certainly a lot more so than your gasser formulas ever will.

BTW, what about those wonderful formulas of yours that I used to PROVE that a 400HP engine needs an exhaust slightly larger than 3"? No reply to that? Cat got your tongue?

You sir appear to be a) lacking in real world knowledge or experience with diesels and b) trolling for an argument.

I assure you that if you want to get into a debate with me you will only end up looking foolish (or should I say even MORE foolish). In a debate, I'll hand you your arse...

you tell him:behead::tank:

Bob, he’s trolling alright.

He thinks he’s all knowing just because he brags about getting 700hp out of his gasser goat. Every word that he types compares diesel engines to gasser engines. Comparing 3.8L Grand National or 2.3L SVO engines to 3.0L diesel engines is as simple as comparing apples to oranges. A diesel engine takes in more then 100% of it's air capacity (more then it can use) almost all the time while a gasser takes in 100% of it’s air capacity only at WOT. That is why a Grand National or SVO with a 2.5” exhaust is quote: “more then fine”.

What I've seen here is a guy who just brags, trolls, makes unhelpful comments, and pushes Amsoil products. ;)

im glad lance isnt the only one to notice that. see the red triangle on topright of each post, http://www.peachparts.com//shopforum...ons/report.gif please use it to report each of his trolling to brian so that he my get the point someday

Really I think the most significant improvement someone could make to the exhaust other than a cherry bomb or a straight pipe is make it come out the the through or just above the bumper like it does on a lot of modern sport cars. There is a nice low pressure point in the slipstream. The down would be the back of your car would get sooty quickly.