4" Downpipe question - Ford Powerstroke Diesel Forum
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Old 03-10-2009, 06:45 PM
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4" Downpipe question

I have an early 7.3l F350 I just picked up. Doing the basic mods performance improvement. I have the 6637 DIY, the zener, zoodad coming. I am wondering about a 4" downpipe coupled with a 4" straight exhaust.
I wont have a tune or chip for a while ( a few months). Will these mods adversley affect performance before a chip. I tow a big trailer and thats primarily what the truck is for.

thanks
A
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Old 03-10-2009, 06:47 PM
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just keep the egts manageable when your towing

you will see a little better performance with the intake, and TB exhaust
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Old 03-10-2009, 06:48 PM
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those mods should be fine but be for you get a chip i would get some gauges(boost,trans,exhaut)

Ben
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Old 03-10-2009, 07:15 PM
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Im skipping the gauges this round. I debated it but I decided to wait and get it with the tune. I did get the trucool 40,000 cooler and new tires and a kenwood DNX5120, So Im a little tapped before our dune trip.
Is the 4" straight with downpipe noticeably louder? I know the motor is loud to start and Im hoping there isnt a noticeable drone.
Also, Will this combo produce higher EGTs ? I thought bigger downpipes meant lower temps.
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Old 03-10-2009, 07:17 PM
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it will be louder if you do a straight pipe
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Old 03-11-2009, 06:12 PM
JJR JJR is offline
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Use the money you where going to spend on exhaust and buy the guages first. Fact is going with a larger downpipe will kill lowend torque especially with a stock program. I would replace the stock muffler with a free flow through design and leave the rest of the exhaust stock.
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Old 03-11-2009, 06:16 PM
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Quote:
Originally Posted by JJR View Post
Use the money you where going to spend on exhaust and buy the guages first. Fact is going with a larger downpipe will kill lowend torque especially with a stock program. I would replace the stock muffler with a free flow through design and leave the rest of the exhaust stock.
if using a bigger dp kills lowend torque, why does everyone do it?
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Old 03-11-2009, 07:02 PM
JJR JJR is offline
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Because they don't know any better. On a modderate to heavily modded truck the 4"dp makes sense. On a lightly modded or stock truck it just is not needed. It will make the truck seem peppier of the line hot rodding around town empty but when you hook on a heavy trailer and pull a hill at highway speed you can notice a little loss of torque with the 4" dp. Like I said this is with a lightly modded or stock truck. If I have to choose guages or exhaust for this application I would spend the money on the gauges first.
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Old 03-11-2009, 07:14 PM
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Quote:
Originally Posted by JJR View Post
Use the money you where going to spend on exhaust and buy the guages first. Fact is going with a larger downpipe will kill lowend torque especially with a stock program. I would replace the stock muffler with a free flow through design and leave the rest of the exhaust stock.
i never heard that one
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Old 03-12-2009, 11:04 AM
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I have a 4" downpipe and straight through muffler. Sounds great, the engine is still the loud part. I noticed NO loss of torque or power while towing my minor 7000 lbs. Intead the freer breathing of the muffler change made a noticable improvement. The whole 4" system was cheap enough and worthwhile. I don't believe that there are any losses, is a 4" really needed? Probably not. The stock downpipe IS 3" which I do not believe is enough for a 444 CI engine under boost. If you're from the gas world, a 3" exhaust can only support a 350 CI engine. Turbo engines don't need backpressure.

On the zoodad thing you ordered. Send it back. Your 6637 setup does not suck air through the duct that the zoodad deal improves. It's totally worthless for an open element filter.

How's the trans cooler? I need to put one on before summer and want that 40k cooler since the 6.0 cooler is so expensive.
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