Straight pipes and low end torgue - Ford Powerstroke Diesel Forum
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post #1 of 14 Old 03-08-2011, 02:06 PM Thread Starter
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Straight pipes and low end torgue

Another basic newb question. I plan on putting a Walker BTM muffler on my stock exhaust that has the flow through characteristics of a straight pipe.
I've heard when running an oversize or straight pipes with no back pressure you lose some low end response and torque. Have those of you running straight stock pipes experienced this?
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post #2 of 14 Old 03-08-2011, 03:17 PM
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When I did my exhaust I went to 4" and did notice a torque loss running stock and with my Superchips 1705. If i had to do it again I would have saved some money and just did the Walker BTM muffler on stock exhaust. It would have been good enough for my needs. That being said after doing some research on it I think the torque loss is due to the lower pressure reading at the ebp sensor. This sensor uses the exhaust back pressure to adjust how the engine fuels depending on load (which is higher exhaust pressure). It also adjust shift firmness according to load (with an auto). So with the better flowing exhaust it doesn't think it is working as hard as before thus loss of torque feeling. A custom tunned chip will fix this as did my PHP tunes. I think it still affected it with my superchips tunes though. A fix for this running stock tunes and free flowing exhaust would be to put the sensor in the intake so it could read boost pressure instead. This will trick the sensor and still give it a verying reading based on load.
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post #3 of 14 Old 03-08-2011, 05:05 PM Thread Starter
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That makes sense. I'm planning on getting a PHP tune but it's further down the list after gauges and I THOUGHT after putting the BTM muffler on the stock exhaust.
Are you saying until I get the PHP I would be losing torgue and performance by putting on the BTM?

I do know that just doing the DIY Tymar intake and Zoodad my truck woke up and is more responsive both at low and high speeds plus it shifts very smooth now and at more consistant points or cadence whereas before it was unpredictable and sometimes wouldn't finally hit fourth or overdrive until at high RPMs.

Edit for afterthought: You don't suppose the above mentioned smoother shifts are from a fooled ebp sensor that thinks it's underloaded and not perssuring up the trans lines or is it maybe because with the Tymar it;s not starving for air like before?

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post #4 of 14 Old 03-08-2011, 05:55 PM
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Your mods will not affect the ebs sensor since you did not do anything to the exhaust. Different trucks will react a little different to the same mods. I would go ahead and do the walker muffler the stock one is a terrible design. On my truck I had a catalystic converter and the stock muffler and went to a full 4" system so I never did the Walker muffler. I know my exhaust probably had pretty good backpressure and I did notice a drop in torque but only really when towing, solo was fine. I also did the walker on my friends excursion and did not notice a significant drop in torque with his truck. I would do the walker and see how your truck reacts, your turbo will like this mod. My truck and my friends truck both spooled better with the freer flowing exhaust, mine just seemed a little flat. I know people that moved the ebs sensor to read the boost instead that had the same issues as me and all had good results with doing it. I never did it with mine though as I went with PHP tunes and was not a issue afterwards.
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post #5 of 14 Old 03-08-2011, 06:02 PM
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nope, noticed no power loss. if you like the sound of a muffled PSD, add the muffler. If you like the straight pipe sound, straight pipe it. makes no difference. There is some debate as to whether running 5" inch exhaust causes a power loss, but a 4" straight is good.


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post #6 of 14 Old 03-08-2011, 06:28 PM Thread Starter
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Your mods will not affect the ebs sensor since you did not do anything to the exhaust. Different trucks will react a little different to the same mods. I would go ahead and do the walker muffler the stock one is a terrible design. On my truck I had a catalystic converter and the stock muffler and went to a full 4" system so I never did the Walker muffler. I know my exhaust probably had pretty good backpressure and I did notice a drop in torque but only really when towing, solo was fine. I also did the walker on my friends excursion and did not notice a significant drop in torque with his truck. I would do the walker and see how your truck reacts, your turbo will like this mod. My truck and my friends truck both spooled better with the freer flowing exhaust, mine just seemed a little flat. I know people that moved the ebs sensor to read the boost instead that had the same issues as me and all had good results with doing it. I never did it with mine though as I went with PHP tunes and was not a issue afterwards.
Thank you Sir.
Thats what I was hoping to hear, as I sit here smoking cigarettes trying to figure how to make my PSD breath better.

I wanted all my mods, intake/exhaust, in place before installing the PHP so I can tell Bill exactly how it's set up so he can tune to it. Plus, with the gauges I can monitor before and after deficits and gains.
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post #7 of 14 Old 03-18-2011, 06:15 AM
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Straight piped the stock system after gutting the kitty. I have no power loss here, only a big o'grin on my face hearing the turbo whistle and the low rumble of the pipe..
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post #8 of 14 Old 03-18-2011, 09:41 PM
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If i had to do it again I would have saved some money and just did the Walker BTM muffler on stock exhaust. It would have been good enough for my needs.
I completely agree. I would say they both make the truck feel like they breathe better, but the straight pipe was a bit loud, but sounds friggin' amazing. The Walker BTM is a good mid point, you can hear the turbo, it breathes better, sounds louder but is not too much.

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post #9 of 14 Old 03-18-2011, 11:10 PM
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Ditching the stock muffler is the key... doesn't matter if you go to straigh pipe, or BTM, you got the stock, necked-down-to-2.5" inlet muffler OUTTA HERE! Myself I like straight pipe. Both trucks done, van is next. Might do the BTM on the van, as a work truck all painted and lettered for my company, helps the image in the eyes of little old ladys when I'm pullin' a huge dually box van into their driveway.

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post #10 of 14 Old 03-18-2011, 11:44 PM
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Simple as this.. what is the biggest restriction in your exhaust system...

thats right. THE TURBO!

It creates all the backpressure it needs, so anything after can and should be open. These arent little N/A gassers with 2" exhausts lol
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