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Discussion Starter #1
Common Question what can I do to make more power with my 6.5


While not an expert I'll pass along what has worked for me and what I've learned from others RATDOC, GMCTD you out there Thanks for all the help.


1st question you have to ask yourself is what is your goal, power or speed, I'll list what I've done for power/longevity. Speed to me is best left to gassers, yes you can build a fast Diesel but at what cost in the long term, beat it up and it won't last. If you are here on the 6.5 forum you have an "old truck" 6.6 DMAXes are current offering since 2001. How much life do you figure you have in a higher mileage vehicle, not only has your engine been stressed but so has the rest of the running gear. Unless you have done a complete top down rebuild/inspection of the whole truck speed is going to cost you in the long run.


Before plopping down bucks get smart, visit other Diesel sites to see what works there running feud aside; there are some good folks at TDP, another good place to start is www.banksdiesel.com they have a lot of good education on the site. Power from a Diesel is tied to airflow which is why turbo and in really big engines turbo/supercharging is a necessity, while you are making power you also want to keep combustion temps under control to keep the engine from self destructing.


My truck easily pulls 12K which is a lot for a L56 K1500.


1st thing I did was to install a free-er exhaust Banks 3.5" cat back system, this reduced backpressure and lowered exhaust temp, the factory down pipe gets replaced with a mandrel bent one, factory pipe look like it had been run over by our truck. Other vendors out there for this system check around, Banks was pricey but at the time I did not know better. free flowing air filter was also part of that kit Amzoil or K/N your choice another site had a pretty long study end result was Amzoil had better result but K/N wasn't far away in my opinion.


The L56 EGR engine upper intake needs hogging out it has (2) 1/8" wide x 3" long slits beside the EGR tower that the engine breathes thru, I removed the excess with a shortened metal cutting jig saw blade to reduce mess that would come from a air or dremel grinder. make sure it's hospital clean before reinstalling, don't feed the engine metal chips it can't digest. Also replace "donut gasket" ring that sits between upper and lower intake that seals EGR port/tube, hard to see under the soot but its there. I left a little webbing 180 deg apart to add support to the center tower.


Later 6.5s OBDII with electronic IP have problems with PMD/FSD overheat relocate on remote heat sink ASAP if you can't afford that, at a minimum remover plastic "Turbo Power" dress up cover to allow more flow across PMD.


Gages, not enough can be said about importance, if you are a data nut like me more is better, boost & EGT at a minimum, trans if you are frequent towing


Do no more mods than exhaust restriction removal without them!!!


You need to know when to back off Max EGT post turbo location 1000F.


If pre 97 truck and will heavy/frequent tow consider up grade to dual H2O thermostat and HO 130gpm water pump, better fan clutch.


Boost control allows fake out to PCM IAT so boost stays in longer, factory PCM program backs out boost when you need it most, max boost without Intercooling in my opinion 10 psi will explain later. Mechanical WG controls are available for mechanical IP and WG trucks


Remote bypass oil filt setup, on K (4x4) series IMHO a necessity just to get access to the filter, stock adapter does not allow easy access, bypass filt has second element for better filtration plus extra oil helps reduce operating temp from more oil to be cooled and passive cooling as filter bodies are in cooler air stream location than under engine.
 

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Actually Turbine Doc, I think you got it pretty close to being on the head. I think a lot of people might suggest slightly different things, but for the most part, you have covered the bases.


The only thing I would comment on is over on the GM-Diesel site, a couple of guys did tests on the "turbo power" cover, with digital gauges, and saw no noticable increase or decrease in temps with the cover on versus the cover off, driving or idling, so our concensus was it is your own preference.





If I can add one thing it is to second and reiterate your caution, to make sure you get the guages before attempting fuel or boost mods, and to stop modding before maxing out, as the 6.5 won't take a lot for very long, unless you get into the block, crank, pistons, basically you get the idea.Edited by: CAT 3406
 

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then when all of the above has been done, get rid of that restrictive turbo.
 

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Or...


Make your own headers to dual turbo set up, 5" down pipes (YES x2) and water to air intercooling.


Check back with me in one year on this project. Still on the drawing board at this moment.
 

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TURBINEDOC- You're welcome!!!!!



And for my next trick, I'll show you how to make your TDI fly...........


so start saving those pennies!!!!!



Tom
 

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Turbine Doc was that a typo about the L56 upper intake? I have a 94 L56 and the two passages in the upper intake were large enough to slide my fingers into. I did open them up some and replaced the lower with a 93 L65 part to block off the egr.
 

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Discussion Starter #7
Yes a typo 1/8" exaggeration to say the least, forgive me I did not really think about it until I re-read what I wrote; but it was pretty small slit either side of the EGR tower and my memory isn't what it once was. Finger width is a more accurate size, still pretty small to try and feed a 6.5 with once you start modding it for power, especially when you look at a L65 upper full flow intake, no EGR port. Edited by: Turbine Doc
 

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I was surprised to see the same restriction in my '94 L65, but last weekend I was visiting a friend with a '94 L65 and he had the same thing. I havn't see this in other year L65 ('93 or '96)that I've looked at.


one thing you didn't mention was grinding/polishing the lower intake. Say what you want, I've done it on three trucks and it's a noticable improvement.


The water to air intercooler I'm working on is going to collect oil from the intake and return it to the motor for lubrication, not combustion. Edited by: quantum mechanic
 

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Discussion Starter #9
I've done some more since I 1st posted this learned a little more I am now running mandrel bent crossover ala www.kennedydiesel.com , H/O injectors same source, reflash & PMD isolator ala www.heathdiesel.com , deep trans pan and diff cover www.yourcovers.com, suspension assist www.activesuspension.com , Lock & load hitch www.putnamhitch.com, Powerstop rotors & pads & stainless steel brake lines ala JC Whitney,
25K rated Deraile trans cooler from Summit, and some other longevity mods ala www.lubespecialist.com now making 197 Hp rwhp on a L56 engine with capababiltiy to drag 18K loaded trailer driven in moderation, got more to do but that involves going into the engine itself. More to follow stay tuned.
 

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Does taking the turbo power cover off really help?
 

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Some say yes some say no mine is on the shelf basically since I owned the truck, but that recommendation was given to me long time ago, also when I had pump mounted driver then, supposedly there was a GM bulletin on it that said to remove it. Now that I have a remote mounted FSD not a big deal, although it does allow better monitoring of leaks, access to the EGR and fuel filter.
 

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