Duramax power and cooling modifications for towing

[Mark Rinker]

I am interested in hearing what people are doing re Duramax modifications - specifically for increasing power and cooling - while towing RVs, flatbed trailers, etc.

Under the Performance section, I have recently posted findings while testing three 'tow' tunes. I found power and better mileage, but also found that all three have limitations when it comes to towing over 20K# GCVW in moderate/warm temps in moderate to steep mountain grades...

Your input is appreciated!

[moss6]

Mark,
Here is a post I made last year. I still like everything that I did except that I did remove the fans from the engine oil cooler because they were actually an air restriction if not running.
I do not have to worry about anything but EGT's now; all fluids stay nice and cool even under the worst of conditions. You have seen first hand what happens to temps when towing heavy, it's good to see someone interested in relieving the heat load.
It is now an extremely rare event for my fan clutch to kick in.

LBZ Heavy Towing Improvements

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I have recently undertaken a project designed to lesson the heat load while towing heavy (14,000lbs) on a 2006 2500 Chevy LBZ. I started several threads on another forum in search of answers and guidance on the project; a mistake, I soon found out. Part of the problem, I am sure was mine, as I used the evidently taboo words like ‘hot’ or ‘overheating’ in my description of conditions that I experienced when towing heavy under adverse conditions. Talk about lighting a flame! You would think that I had insulted their mother; suggesting that there might be some benefit in lowering what I consider to be temperatures in the upper operating range ON MY TRUCK. The majority of responses avoided any question I posed, rather they just basically expounded on the ability of their trucks being able to tow loads in excess of listed maximums at any speed under any condition without so much as breaking a sweat. The general consensus being that I am a moron, or that, as they put it a ‘troll’?? looking to sell something.

In any case the project is very nearly complete but there still a few things to be done and some answers to be had.

First of all a list of modifications and any real or perceived effects that I can comment on at this time.
1. Banks Monster 4” cat back.
I truly can say this addition offered no benefit in the way of power or in the lowering of EGT’s on my truck. If anything, there may be a reduction in 1800 to 2000 rpm torque. I guess I should put the stock back on and re-evaluate but I don’t think there is enough difference to make a difference and the Banks is nice and quite, near stock sound. Besides I’m tired of crawling around under the truck for now.
2. Removal of the innards of the cat; this on the suggestion from John Kennedy, and there was some lowering of EGT’s.
Exhaust noise increase was very minimal; a good modification.
3. Addition of a 3” cold air supply to the stock air filter housing. Routing is from the passenger side recovery hook hole
(hook removed) up and through an enlarged hole in the bulkhead and then into a hole created in the housing. The
stock supply is maintained from the fender well but the holes were enlarged. The filter housing received some
additional sealing from engine compartment heat. IAT’s came down some and seemed to lower even futher when the
EGR was blocked. Total average gain I would put in the -8 to -15 degree range but I honestly don’t think it had much
effect on the EGT’s. The engine does make an intermittent hollow sound now when idleing that I assume is when the
EGR valve opens and there is no exhaust gas available. I would rate the modification as good if for no other reasons
than supply air IS cooler and the engine is no longer forced to ingest it’s own exhaust. I like the additional air supply
far better than any after market add on that I have seen, and I can use the stock filter and not have to accept the grit
that the after market filters let in the engine.
4. Installation of a Setrab 920FP as an engine oil cooler with an Earl’s sandwich plate with -10AN fittings for 5/8”
Aeroquip ‘blue’ 300degree hose. The Earl’s plate is the only one that I am aware of, that has the ability to use 5/8”
Hose which the Duramax needs for the amount of flow. The plate has a 175 degree stat. The ports in the plate were
A bit less than 5/8” so I did enlarge them; if you do this be aware that the thermostat seat is very close so care must be taken not to damage it. Also the adaptor bolt has a smaller hole that the stock filter bolt so I drilled it out to match the size of the stock unit, I believe 7/8”. The cooler was mounted about 2’ forward of the fuel cooler at a bit of a tilt so that it is protected by the truck frame, and a screened shroud was fabricated to capture and funnel a bit more air than what would normally go thru the cooler. The cooler fans are activated by a switch in the cab so they can be run as desired. I need to install an oil temperature gauge and have asked for some advice on this forum for a good location for the sensor but the choices so far are few and difficult. I really wonder now if there is any one out there that has installed one. I sure could use some help on this one!! With the gauge I can better tell how much the cooler helps, what I can say is that the oil pressure is now somewhat higher when the truck is hot and especially when pulling heavy. I cannot tell if it lessened the heat load on the radiator but in theory it should. I am very pleased with the install and am sure that the cooler oil has multiple benefits. The cooler adds near 1 qt. to the system.
5. Installation of a ‘MikeL’ transmission cooler, this also a Setrab product which is a replacement for the stock trans-
mission cooler and offers at least twice the cooling of the stocker. This cooler is very nearly a bolt in; the only mod-
ification needed is a little notching of the square tubing ‘A’ frame for the hood latch. The cooler comes with the
quick connect fittings installed. This is a remarkable cooler and I have yet to see temps above the half-way point on
stock temp gauge. The cooler adds a about a quart of oil to the system and must be relieving some of the radiator
heat load.
6. Installation of a Setrab 920 as an auxiliary radiator, this is the same cooler as the oil cooler but does not have the
fans, adds about a quart to the system. This cooler was installed under the bumper and behind the air dam with a
hole being cut in the plastic air dam for air supply. This cooler is tied into the EGR circuit which is 5/8” hose so
-10AN fittings were used on the cooler. In non towing driving the stock temperature gauge registers somewhat
lower than before so temperatures before I’m guessing were somewhat above the thermostats 195 degree control.
Towing heavy the stock gauge shows very much the same as without the cooler if conditions are favorable. If con-
ditions deteriorate, wind, steep long pulls etc the temperature stays well below what it was before and it is now
very rare for the fan clutch to engage. That being said the fan clutch does now seem to engage more when you
slow down from the highway and enter a town with slow speeds. The fan does not stay engaged very long but it
does seem to run more than before; I have no explaination for this nor for the fact that the fan clutch seems to
engage more on cold start ups even when the ambient temperature is high??????
I am considering adding a scoop below the hole in the air dam to capture even more air and futher enhance the
cooling when at highway speeds. This has already proven to be a real stress reliever for me; not having to monitor
the temp gauge so close and wondering how long before the fan clutch will finally kick in and cool things
down.
7. Custom tuning by John Kennedy. The tuning offers a lot more pull and the truck just does not have that feel anymore that is working a little to hard and that you might ought to ease up a tad. The EGT’s non towing are definitely lower about 75 to 100 degrees. Towing EGT’s are lower too as long as load is not too extreme. What
I observed during the only chance I have had to tow since the tune was installed, is that when loads approach
the 95% range the EGT’s will still become excessive. The highest that I ever saw before the tune and the other
modifications to cool things down was 1380 degrees and I immediately backed out of it. This time with the
additional cooling I went ahead and pushed things on a long steep grade out of Santa Rosa, N Mex. and the
EGT’s got to 1460 degrees before we crested the top. One instrument that I was lacking on that trip was a boost
gauge so I do not know what kind of pressure I was getting from the turbo; I have a good one now and will be able
to see how that looks on a trip in two or three weeks over some even demanding climbs. I will not let the EGT’s
get that high again but will be able to see what boost is at high load percentages and be able to talk to John to
see if any futher improvement is possible. It may very well be that this is as good as it gets and anything better
is beyond the realm of reason. The Kennedy tune is an exceptional value and far exceeds any generic that I have
had in the past. I am very pleased with this modification.
8. I am considering creating underhood ventilation to help in lowering underhood temperatures. I notice that Sun
Coast offers a hood that vents near the center of the windshield and see no reason that the stock hood wouldn’t
easily lend itself to the same type of venting. I also notice that Ford now has underhood ventilation on their new
diesels so there must be some benefit to it. Like to have some thoughts on this.

Overall I am very pleased with what I have been able to accomplish in the attempt to ease the heat load of the truck. It is a vast improvement over what it was before and is far less stressful on me and the truck when towing heavy; trips now are more what they are supposed to be…..a pleasure. Many thanks to those who did actually help; most notably Mike and John. I know much of what I cite as results is very lacking in documentation and I should have done much more to make it better, I do apologize for that. I did enjoy doing it and hope to even further improve on it with your input.

[Mark Rinker]

Thanks for re-posting. Have you considered upgrading to a larger turbo? Unless you tow all the time, its probably cost-prohibitive.

A larger turbo and billet torque converter may be in my future...that is if I can stay in business, in order to afford them... :)

Anyone out there done either of these mods, for towing purposes - not for racing?

[moss6]

Mark,
I think the the turbo upgrade is a very viable option, though questionable as cost effective. A more efficient intercooler would also be very benefitial, but from what I have seen out there in that respect I have reservations on the claims; look at the negative results on the Banks units.
Until/if some new technology becomes available, I think I have gone as far as possible in making the LBZ as tow capable as it can be; that is sans transmission beef up and turbo upgrade/cool mods????
I have never seen anything that could not be improved upon, wife and children by special clause excluded.
Randy

[Mark Rinker]

I might start with something MUCH less expensive, like an LB7 fan clutch that kicks in much sooner...

Your mods are obviously effective at what they set out to accomplish - congrats on that success.

[carco]

I mounted a large cooler built for Allison transmissions under the cab and plumbed to the trans cooler circuit. I do not tow far very often but when I do weights are 21000 to 23500 GVW. The cooler has a temp switch and fan but I do not know if the fan has ever engaged. trans temps are definitely controlled 200 to 210 max per GMs gage even out west in 103-109 degrees and strong headwind last summer. The engine temp is better but still climbs on pulls in real hot and steep grades, but lasts longer before the heat is too high. The biggest factor slowing the truck is usually EGT climbing toward 1400 degrees. When 1350 is reached I back out depending on the length of hill and ambient temp and load. Overall the trans cooler was well worth the $$.
Opened up the air intake to the filter box and from the filter to the turbo. Changed out the turbo mouth piece for an LBZ mouth piece. this added a slight bit more noise and the turbo whistle is slightly more evident. Blocked off hot engine air into air intake. I believe more air is being pulled because the air restriction indicator on a clean filter is now always set near half way. Worth the $$.
The cat falling off the exhaust system was a very good thing. Overall last 30000 miles a plus .2 to .3 MPG. Slightly more noise through 4" system with 4" see through muffler, sounds good!
I do also run and Edge w/Attitude, levels 1 or 2 only, boost stick, EGR blocked and FingerStick. Oil changes 7-9000 miles that oil analysis show as ok. Trans oil changed every 25000.

[moss6]

Having begun using fuel additive since the last time we towed last Summer I'm curious as to what if any difference to expect this season in respect to overall temps. and especially EGT's. What effect does a cetane boost have? I do feel that there is a very slight increase in power which is good, but not if that also equates to a rise in temps; what are the thoughts on this? I haven't seen this addressed before.
Randy

[carco]

Moss, unless the system is highly contaminated with deposits I do not believe you will notice a difference in power or driveability. If you truly notice a difference you needed the additive and a dose from time to time may well be good, continuous dosing is a waste of $$$. Cetane boost might be noticeable and may allow the engine to run a little quieter and the dyno may pick up a power increase but here again to actually notice may be hard to realize. Temp differences will be negligible. bob...............

[moss6]

Is negligable higher or lower? One would suspect that combustion duration would be somewhat affected, my guess is lengthened, which in theory should raise temperature to some degree. But again if that is actually fact then less fuel would be needed, IE proven positive gains in fuel consumption so the on e might cancel out the other in terms of overall generation of heat. Just a thought. I have always added a cetane boost since starting the addition of the additives and have experienced milage gains as we as performance enhancement.
Randy

[moss6]

Just returned from first towing trip of the season and experienced the lowest EGT's I have ever seen on that particular route that I have traveled many times. I would estimate that temps on average were at least 100 deg's lower, most noticable on the long steep grads, especially the one just west of Santa Rosa, NM. Was it just the conditions or was it the additive? Don't know, but there was a definate difference.
Randy