My mechanic recommended converting to 5" exhaust and not installing the muffler. How load is this thing going to be? Is there any big performance gains with the 5" exhaust?

 

There have been reports of a loss of low end torque on the PSD when using an extremely large exhaust. IMO, 5" is way overkill unless you have made other engine mods (extreme chip, larger injectors, turbo mods etc) that justify needing that much theoretical flow. Otherwise you'll just be driving a Ford pickup version of one of those riceboy machines with the coffee-can exhausts. And wasting your money.

 

4" is good for up to 450 HP from what I've heard. Unless you plan on exceeding this with mods, and I'd sure like to know how you would exceed this, go with a 4" exhaust and a larger downpipe. I currently don't have a muffler on mine, and it's not bad until about 2500 RPM's. When I bought the truck it didn't have a muffler on it, but I plan on adding one soon. The rumble above 2500 RPM's is very loud.

 

My neighbor just put on 4" and he reported a low end power loss.

 

 

I don't know if the IDIs and the DIs are that different in the exhaust department but a lot of the guys have gone to 4" straight pipe with no muffler and love the quicker spool up on the turbod trucks. No one has reported a loss of power. Not too loud until it gets hammered hard. I heard one on the river the other day and you could hear the turbo chopping up the sound which will quiet it down quite a bit. Sounded good though. I can't wait until I can afford the ATS upgrade for mine and go with 4" and no muffler.

 

I havn't came across this on a psd yet. But on my bus with a cummins. I had the pipe break before the muffler and anyone that has heard a cummins knows they are noisy. With out the muffle piped in I could not hear the turbo wine like I normaly would. And the turbo did suffer a little bit. Cause on this motor the turbo does run off the exhaust. I'm not positive and I have not looked real close but doesn't the psd's turbo run off the exhaust. If so that would be a reason for loss of low end torque.

 

I'm one of those guys from The Diesel Stop with the 4" exhaust, and I did notice a slight drop in low end torque, but I gained a bunch at the top end. The loss at the low end was negligible, and might be more of a perception than anything else. Since there was such a gain at the top end, the bottom end might just seem to have dropped off. The turbo itself provides all the backpressure you need, and as was stated earlier, you won't need to go bigger than 4" unless you plan on exceeding 450hp. I hope this helps.

Quadzilla
'95 F-350XLT Crew Cab SRW 4X4 PSD, 35X12.50X16.5's, Limited slip 4.10's, Hypermax downpipe, gutted EBPV, "Catless" in Seattle, "Renegade" 4" exhaust system, CTFD sticker, Air bags on all four corners, TYMAR intake, shimmed fpr, Diablo Delta chip, Fumoto valve, Autometer pyrometer, Sonnax valve, Tricumulator springs, Tru-Cool, HX mod, Magnefine tranny filter,
4R100 pan, Red Line synthetic in transfer case and both diffs, reverse shackle kit, big 'ol grin on driver's face.
And a wish list that gets longer every day.
(Thank God for a wife that likes big trucks.)
Pictures: http://community.webshots.com/user/quadzilla100

 

> The turbo itself provides all the backpressure you
>need,

AFAIK, it's not loss of back pressure in the exhaust that causes loss of low end, it's losing velocity in the exhaust that's the issue. Here's some comments from Gale Banks about the subject..And he does actually measure the before-and-afters on mods with the use of G-meters and dynos, something most of us can't practically do.

"Needing backpressure, esp. on a turbocharged engine, results from an Old Wives Tale. The turbocharger turbine would be optimum with a 12-18 inch long, conical outlet pipe, with an appx. 20-degree included angle in the conic section. In other words, a megaphone -!"

"You want the coldest air, at the highest pressure, going into the compressor inlet. An open element, drawing in under-hood air, is a BIG no-no, and will actually kill power. I'm sure the factory airbox can be improved on, and this is something we're pursuing on the Dodge and the Ford."

Why some who have gone to 4" or 5" exhaust feel they have lost seat of the pants power?
Gale Banks: First of all, we found no additional power above 3.5". We lost none, and gained none, going to 4".


-Bill
Two Easters Ranch
Colorado

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2002 F-250 S/Cab Short Bed PSD 4x4. SCMT +80 HP, AFE Magnum intake.
1996 F-250 S/Cab Long Bed 460. E4OD auto, 4.10 posi, Air-Lift suspension, K&N filter in modified intake box, modified ignition advance curve, Edelbrock 2x61 mm throttle body, L&L 4 into 1 headers, milled heads, 3" exhaust system, cat & Flowmaster 70, modified MAF meter. 7,700 lbs GVW, 5,700 lbs empty.
{E\...F}

 

I,ve put 5" from the downpipe back on mine. It is quieter than some i have heard with 4". I'd like to get a tape recording of it and put it on hear. If any body really wants to hear it let me know. Didn't notice any loss, turbo definitly spools faster.

Just another opinion.

 

parrothead...how do you come to conclusion that an open air element is bad when every one is going to an open element intake. I know my truck runs alot better and i can get 30 psi. of boost out of my 99 with the tymar intake.

 

If you read the port from paarrothead he is quoting Gale Banks. I think he is someone who know a little something about the 7.3 Diesel.

Will-

 

If you read the port from paarrothead he is quoting Gale Banks. I think he is someone who know a little something about the 7.3 Diesel.

Will-

 

Well i am speaking from experiance on my truck. It runs 50-75 degress cooler with the tymar intake than with my k&n with the stock intake. i got 3 more psi of boost than with the k&n.