Custom Tune Question

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Mar 11, 2019 | 10:23 AM

Martin Torres

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Tuned

Joined: Feb 2016

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Custom Tune Question

I have a question on custom tuning. Have used the TS6 but have a Hydra arriving on Wednesday. Saw several threads on here and a few other sites about decel tunes and EBPV brake mods. Read a few warnings about potential backpressure/valve issues and potential automatic transmission issues but not one actual post about anything going wrong as a result of a decel tune or EBPV brake mod. In fact, most if not all of the posts by those who have them are positive if you know when to use them.

My truck is a 2003 7.3 with a John Woods Towmaster auto trans and I am really interested in a decel tune for Hydra. If I can’t find one, I may do the mod. Not interested in buying an aftermarket exhaust brake. I want good info to base my decision on though. Does anyone here use a decel tune or EBPV mod with an auto trans?

Can a custom tune be built to activate the EBPV, lock up the TC, only activate when the brakelight switch is active, and only activate at a minimum RPM or higher? Once I find a couple tow tunes I like, can these be added to an existing tune?

Mar 11, 2019 | 11:09 AM

roostercrows

Laughing Gas

Joined: Aug 2005

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From: Port Elgin, On

Very good questions. I am curious about this as well and am subscribing to hear the answers.

Mar 11, 2019 | 11:57 AM

Tugly

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Joined: Jan 2011

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From: Puget Sound

I happen to have experienced more than one decel tune, and I know a little something about the limitations, strengths, and caveats.

On an automatic, you need a good coast clutch.
4th gear decel is pretty tame, but 3rd gear gets it done. I can hold 40-45 MPH down a 9% grade while towing my 8000-pound boat with surge brakes on the trailer.
The exhaust backpressure needs to be kept in check, or you need stronger valve springs - you can use the decel tune as long as you are not at very high RPMs (like at high freeway speeds in third gear).
The tuning can lock the torque converter until the RPMs are too low to make pressure to hold the lock.
The EBPV needs to be maintained, and a lot of the turbo exhaust castings have a defect that the butterflies catch on and stick closed until the engine is shut off. Filing that defect down will remedy the problem.

Mar 11, 2019 | 02:16 PM

roostercrows

Laughing Gas

Joined: Aug 2005

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From: Port Elgin, On

Rich, could you better define a good coast clutch please? I'm guessing that the factory one doesn't meet that standard.

Also, what would a good coast clutch cost? And if you were starting with a completely stock truck, would you consider it worth upgrading the coast clutch in order to get the decel tune?

Mar 11, 2019 | 02:25 PM

Tugly

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Joined: Jan 2011

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From: Puget Sound

I'm not much of an expert on transmissions, that title falls to Mark Kovalsky. I know that during my research into the HD4R100 transmission I have, the coast clutch was mentioned for the sake of engine braking.

Mar 12, 2019 | 02:20 AM

aawlberninf350

It's a Van Gogh

Joined: Feb 2010

Posts: 7,802

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From: Elk Grove, CA

IIRC the decel tune from DP increases line pressure on that clutch to help keep it from slipping too much. No doubt more robust components would be more desirable. But the tune works as intended on my stock 4R100 (well I have a Factory Tech valve body, otherwise OE) with no obvious harm in my experience. Cody uses something similar on a daily driver tune AFAIK. I'm sold on this tune, but it's absolutely not simple. Trans tuning is important but often unappreciated.

Effectiveness of the deceleration depends on RPM. Low RPM won't do squat. But say 2200 and up it works great, whatever gear that happens to be. And no doubt if you engage it at 3300 RPM you'll be on the side of the road wishing you had installed primo valve springs. That said, operating a decel tune is no more complicated than driving a stick shift.

To sum up I'd never DIY an engine brake system, get something from a pro.

Mar 13, 2019 | 12:19 AM

ScaldedDog

Fleet Mechanic

Joined: Aug 2010

Posts: 1,456

Likes: 155

From: Sedalia, CO

I've got a thread on here from years ago where I tested DPs exhaust brake tune, and I couldn't get back pressures any higher than those commonly seen in other driving situations, so I stopped worrying about it. Years later I'm still towing with the same truck and same tune.

These tunes can be hard on coast clutches, but so is mountain towing without an EB tune. In fact, mine failed, and that caused me to get a BTS transmission, and only then did I start running any non-stock tunes.

Mark