Diesel performance Mods - What have you done? What HP do you get? - Page 2 - PeachParts Mercedes-Benz Forum

The Warden · #16 01-23-2004, 10:03 PM

I dunno how long the Cummins will live in this condition, but, with a redesigned head gasket that can hold the pressure, I believe that they can break 100 PSI. Also, after '91, the Cummins in the Dodge comes stock with an intercooler.

There's a guy who's got a Ford that he dropped a 6BT Cummins in (with the dual turbo setup); he's putting out slightly over 800 horsepower at the rear wheel. He also uses this truck as a daily driver, and the engine's been holding up well for quite a while.

I believe that, if the compression ratio was lowered (in order to allow more boost without compromising the head gasket) and the EGT's were religiously monitored and not exceeded, BOMBing an OM617 can be done safely. A ram-air setup would make the turbo work less hard to get the same amount of air, and the bigger the exhaust pipe, the better.

wolf_walker · #17 01-24-2004, 12:35 AM

I'd be willing to bet a lot you could significantly increase the power output if one was willing to do what it takes.

Generaly, with a small high speed turbo diesel, you can increase boost and fuel to a degree and pick up power and not hurt anything. For real power though, retard pump timing, lower compressin, lots of boost, fuel and intercooling. This requires basicaly rebuilding the motor, cost prohibitive to most of us.
There was a VW guy with a rabbit "GTD" he built using basicaly this formula, and then some. It worked out pretty well, same great MPG and a crap load more power. It seems to me that with the 617's, which by all accounts are a 400K mile motor in the least given proper care, even if you modified it to cut the life time in HALF, hell, 200K miles aint bad.

Except for the fact that most of us are already on or past that 200K miles.

Personaly, if I had to have one of these apart, there are a few things I'd do. Gasket match the intake/exhaust ports on the head(if there not already that way), maybe a little clean up porting, depending on how it looked, lower the compressioin some one way or another, look into head studs(again, if it already does not have them), there really isnt much that Mercedes did not already do as near as I can tell from reading the shop manuals rebuild procedure. I might look into some of the heat resistant and/or low friction piston coatings out there, maybe cryo treating some odd and end parts if I was feeling obsesive. A little more power and taller gears, and a 5spd, and I'd be pretty happy with the 617. Frankly there are better motors to spend the money on for going fast.

/ramble/

rwthomas1 · #18 01-24-2004, 06:56 PM

What a pile of crap. Someone, anyone show me evidence of moderate diesel mods used judiciously "decreasing engine life" or magically causing the engine to explode or become unreliable. All I have ever seen is moderate mods used with caution by an experienced driver results in better mileage, pulling hills in higher gears at higher speeds, better acceleration, and oh yeah, big smiles. Go back to sleep, put yer heads in the sand and let the tweakers tweak. RT

wolf_walker · #19 01-24-2004, 10:15 PM

Quote:

Originally posted by rwthomas1
What a pile of crap. Someone, anyone show me evidence of moderate diesel mods used judiciously "decreasing engine life" or magically causing the engine to explode or become unreliable. All I have ever seen is moderate mods used with caution by an experienced driver results in better mileage, pulling hills in higher gears at higher speeds, better acceleration, and oh yeah, big smiles. Go back to sleep, put yer heads in the sand and let the tweakers tweak. RT

Now tell us how you really feel..

I tend to agree in general, most of what a person is likely to bother doing is not going to drasticaly hurt the motor if your not stupid about it. These things are fairly stupid proof.

coachgeo · #20 01-24-2004, 10:55 PM

LP injection sounds easier.

I really only need more oomph to get along quicker on the upgrades. Others can use LP booste it to decrease on ramp entree.

rwthomas1 · #21 01-24-2004, 11:06 PM

Coachgeo,
The LP injection/fumigation seems to work better on lower compression diesels like Cummins/PS. I have a GM 6.5TD and belong to a GM diesel page. The GM shares a high 21:1 compression ratio and IDI design with the MB's. The GM's have had problems running LP if used at the volumes the Cummins/PS motors use. Running about have the volume seems to work well but obviously there isn't as much extra power like this. I think you might have better luck turning the pump up and watching the EGT's closely. A custom intercooler would be a good idea too. RT

Telecommbrkr · #22 01-25-2004, 01:14 AM

Glad to see that this topic has actually created some good feedback from some different trains of thought on the same result.

So, with my spare engine I should rebuild it basically stock other than the minimal port/polish if required. Lower the compression somehow and figure out how to play with the ALDA to increase fuel flow. I have spent considerable time 'thought' engineering an intercooler system so that's going to be a plus. I am going to be going to the 'fresh-air' intake that quite a few guys have been doing, and also have put together the plans for a two stage Propane injection system that I'll be fooling with on my present engine in the car right now. There is a guy on mbz.org forum called 'Twizted' that has been running this set-up plus NOS and seems to be doing fine as a daily driver. Do a search for him, he has quite a few good pics of his mods. He's also suggested boting on the next size up pump onto the existing turbo for added psi. From what I understand we already have all the potential psi in the factory MB pump so that's not a really big need.

Some one suggested going to a manual tranny to be able to utilize the 617's HP better. Is MB like GM in the way that alot of their engines manufactured during a similar time-period all had the same tranny bolt-pattern on the engine block? I'm in no way intimidated by the fabrication required to make an auto car into a manual where it never existed before. My goal would be to have it look like it came from the factory that way. Did the W126 coupe come with five-speeds? Would they bolt up to a 617?

The possibilities are limitless (other than by your budget)!!!!?

coachgeo · #23 01-25-2004, 01:56 AM

Quote:

Originally posted by rwthomas1
Coachgeo,
The LP injection/fumigation seems to work better on lower compression diesels like Cummins/PS.... RT

hmmmmm... interesting. Please keep me posted. Do you have a link to the threads that are running on this topic?

Thanks for the info.

rwthomas1 · #24 01-25-2004, 04:38 PM

Coachgeo,
The forums I quote are on a paid GM diesel site. The GM diesel guys messed with LP fumigation a while back. It appears one of the inherent problems with a high compression ratio (21:1) is that it is much easier to exceed peak cylinder pressure and damage the engine when messing around with power increasing modifications. On the GM 6.2-6.5 engines increasing boost to more than 12psi non-intercooled resulted in no power gains as inlet air temperatures quickly exceeded 300*F and EGT's climbed quickly as well. Adding an intercooler allows 15psi and more fuel with safe EGT's but experience has shown running hard with this combo results in blown headgaskets. Remember this is not daily-driver activity this is 10-12K on the 5th wheel and WOT for hours. Running LP at the same volumes as Cummins/PS resulted in blown headgaskets and even some crank/rod faliures. Apparently using about half that volume of LP was the compromise for good power and reliability. I should add that Penninsular Marine had problems with cracking piston rings, piston ring land damage on 21:1 GM's in marine applications. Their solution is 18:1 custom pistons. They have had no mechanical faliures since switching to 18:1 pistons. The 18:1 pistons have been used extensively in performance GM's installed in tow vehicles with good results. So whats this all mean? Depending on how much of a performance increase you are seeking will dictate if you need lower compression pistons to reach your goal. Since the GM's respond well to 10-12psi, increasing the fuel slightly and a larger exhaust system with no apparent detrimental effects I would think that the MB's would as well. Pushing past 15psi without intercooling would likely result in problems in the long run. I have no idea where/who would make custom low compression pistons for a MB but I am willing to bet that they won't be cheap. Since the end result of using LP fumigation is about the same as adding more fuel and boost I don't see the cost benefit of installing a $500 system, then buying a LP tank and finding a place to mount it, not to mention fueling it up. The LP system makers claim that the systems increase mileage since the LP promotes a more complete burn under cruise conditions. Have they factored in the cost of the LP? I just don't see LP as the magic bullet. Flowing enough fuel or LP will damage the engine unless you plan on some pretty major mods. So install some boost/egt gauges, turn the boost up to 12psi, have the pump adjusted accordingly to allow a max egt of 1250*F pre-turbo and see if you have enough power. If not, then get out our wallet and mortgage your house. Sorry for the long post. RT

psfred · #25 01-25-2004, 05:41 PM

I think the main reason "rodding" the "typical" US pickup truck diesel engine is so successful is that up to the latest generation engine, they tended to be low compression, low hp engines. Not too hard to get better power out of an engine that has been detuned.

I've seen the debate about dual turbo and lowering compression/raising boost before. I'm not sure what the dynamic is, but I suspect that high compression engines are much more efficient all round, and are very much less tolerant of "extra" fiddling than a somwhat lower output low compression engine. Just for giggles, take a look at the engines available for large yachts -- Detroit, Cummins, and Volvo all make them, and they definitely reflect the engine makers other products. The Detriot and Cummins are low compression engines (16:1) with multiple turbos and 3000 rpm max speeds, give or take a bit. The Volvo is a high compression engine (23:1) and revs to 5000 rpm. Single turbo, about half the weight for the same horsepower.

Adding propane to a hot, highly loaded turbocharged high compression diesel is guarenteed to produce detonation. This will blow head gaskets, burn exhaust valves, melt pistion, and break rings, as usual. NOT a good idea. Works fine if used in a low complression engine not putting out anything like full potential power (2.7 hp per cubic inch, if I remember) on diesel fuel and air. You aren't going to get hot enough pre -TDC conditions to fire the propane in a low compression engine, but 26:1 (a typical number for Volvo diesels given production variations), it's gonna burn long before TDC.

The other two variables to consider are injection timing and injection duration. Fixed IP timing (very common in the US, unheard of in Europe) gives the distictive clanking of pickup diesels (its usually set for max rpm) and another cause, with long (undersquare) stroke, for the low rpm limits.

Given the hp output of a good condition MB diesel, it's gonna be difficult to push all that much more out and keep it stuck together. Compare the hp and torque ratings sometime, correcting for displacement. A 617 rated at 120 hp coresponds to 276 hp in a 6.9 L engine, with torque similar. A 603 would produce 340 hp with 448 ft/lbs torque. That's more hp AND torque than a Vortec GM GAS engine per cubic inch.

Produces good power from 1500 rpm to 4500 rpm, too, not 1500 to 2200.

Peter

wolf_walker · #26 01-25-2004, 06:31 PM

The VW guys have played with LPF fumigation a bit. I've read good results on relativly stock motors. Were still talking relativly small amounts of power, but those who tried were happy with it.
The gains on non-turbo motors were not worth the bother is what I've read, but a mildly tweaked TD version, it made it much more fun, and increased fuel mileage. I don't have much in the way of details, just stuff I've read over the years on various forums and mailing lists.

Personaly, I don't think I'd ever bother, I don't like the idea any more than I like happy juice on a gasser. It's effective, but I just don't like the on and off nature, and that it can run out.

I'll tell you all the single most effective way to make your MB diesel feel more powerful...

Drive a VW diesel for six years prior to the MB.

coachgeo · #27 01-25-2004, 08:28 PM

Thanks RWThomas. Everytime this topic pops up I learn more. Yes I was aware your info was from a GM board. If you have some links I would certainly appreciate it.

just a side note. My LP injection system (not yet installed) cost me 80 bucks minus tank and I can set the pressure /amount of LP at any setting prior to using it. I can time it to come on at anytime I want because it will be injected only when I pull the trigger; literaly. The trigger switch I have purchased is one for a hand held circular saw. It has a lock on it so the trigger can only be pulled ifffff the lock is depressed as well. Picked this style switch to prevent accidental fumigating. I presently am thinking on mounting it to the gear shift on my Unimog.

The idea is to only use it on upgrades to keep speeds more highway friendly. My speeds / and RPM's drop to as little as 30mph on upgrades in this 5.25 ton rig. One reason it is not yet installed is because I don't yet have a feel for the
.....Too little LP <--> ......Too much LP, points.
Any suggestions on how to determine this would be appreciated.

#28 01-25-2004, 08:38 PM

http://www.mrsharkey.com/lpg.htm

http://216.239.41.104/search?q=cache:5B826Xf-TS8J:www.ias.ac.in/sadhana/Pdf2000Feb/Pe821.pdf+propane+injection+diesel+light&hl=en&ie=UTF-8

Some links to the current topic...

#29 01-25-2004, 08:41 PM

Do you want quick, easy boost in performance? take an old wornout 300D and make a "Pusher!"

http://www.mrsharkey.com/pusher.htm

coachgeo · #30 01-25-2004, 08:55 PM

Quote:

Originally posted by 82-300td
http://www.mrsharkey.com/lpg.htm

http://216.239.41.104/search?q=cache:5B826Xf-TS8J:www.ias.ac.in/sadhana/Pdf2000Feb/Pe821.pdf+propane+injection+diesel+light&hl=en&ie=UTF-8

Some links to the current topic...

Much thanx 82. The first one has been updated since I last read it a year or so ago. Glad you brought it to my attention.