OM617 SAE Paper - Printable Version

OM617 SAE Paper - Printable Version

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OM617 SAE Paper - Tymbrymi - 02-11-2010

Went and bought an SAE paper on the design work necessary to turbocharge the OM617 for the W116 based 300SD. It talks about piston changes, oil squirters, turbo map, fuel consumption map, piston temperatures, and EGT limits (almost 800°C!). Very interesting read... well worth the $15.

http://www.sae.org/technical/papers/780633

Here are some of the highlights from the paper:

Piston coolers AND internal oil galleys are extremely important to keeping the pistons cool. See figure 10 for a demonstration of the difference having an oil jet alone and having an oil jet plus piston with oil cooling galley.
The prechamber gets HOT!! 1650°F in places. MB made changes to the head so that the PC had better contact and is able to dissipate the heat better... keep in mind that 1650°F is AFTER the changes they made to the head!!
The STOCK max EGT is 1400°F

Directly from the paper "Gas temperatures at the turbine inlet reach a maximum of less than 800°C, a value uncritical for the usual turbine wheel materials." FWIW, the IDI VW turbodiesels have stock EGTs of 1500°F. This says to me that DI engines are the ones limited to 1250°F (Cummins, etc), and that we can safely run much higher EGTs.

Enjoy!!!

RE: OM617 SAE Paper - ForcedInduction - 02-11-2010

Interesting. Well worth the $12.50. Big Grin

There are more good ones as well; http://www.sae.org/servlets/SiteSearch?charset=iso-8859-1&ht=0&qp=%2BTYP%3APAPER&col=portal&qs=&sae_qt1=&qc=&pw=100%2525&ws=0&la=en&qm=0&st=1&nh=25&lk=1&rf=0&oq=&rq=0&si=1&ql=&jsp_name=simplesearch.jsp&qt=mercedes+diesel&ofType=PAPER&x=13&y=16
One of them discusses development of a 2-stroke common rail diesel for passneger cars and another on using two sequential VGT turbos to increase performance.

RE: OM617 SAE Paper - ForcedInduction - 02-11-2010

Interesting note; EGTs only rise to 1470*f above 4000rpm, from 2000-4000rpm its right at the "common standard" limit of 1250*f.

That suggests the engine is nearing its VE limit above 3500rpm causing reduced cylinder fill and an increasingly rich A:F ratio.

I had been looking into an RPM switch for my GT22v to overcome surge at high boost and low rpms, but maybe it would be beneficial with the Holset as well...

RE: OM617 SAE Paper - winmutt - 02-12-2010

This would explain weld failures in the prechamber bulbs. Nice read.

RE: OM617 SAE Paper - Kiwibacon - 02-14-2010

Interesting find with the EGT's.
It does make sense too, the primary failure of a DI diesel with high EGT appears to be the piston crown expanding and scuffing the cylinder wall. An idi piston is better in this regard.

RE: OM617 SAE Paper - George3soccer - 02-15-2010

Noice, I like that find good looks.

RE: OM617 SAE Paper - cell - 02-16-2010

WIN!!! thanks so much for looking this up!

so that's interesting. at full load, the most efficient point of operation for the OM617A looks to be about 260 g/kWh, which appears to happen at about 2300 to 2400 rpm and which yields just under 60 kW. So that would be about 15 kg/h of diesel. If diesel has a density of 0.85 kg/l, that's about 17.65 liters per hour, or about 4.66 gallons per hour.

this is all very interesting, because my truck happens to be geared and "wheeled" such that I would be running at 2400 rpm at 68 mph. However, that's assuming the torque converter locks, which it doesn't, so 2400 rpm probably happens at more like 65 mph. As it turns out, I make long distance trips with the pedal mostly buried (ie, approximately full load), which gives me a cruising speed of about 65 mph.

so according to that article, if full load at 2400 rpm yielded you 65 miles in one hour, that would be about 13.95 miles per gallon.

I don't have a working odometer or fuel gauge at this point, but at one point I estimated the distance traveled via google maps and measured a fuel economy of just over 16 miles per gallon (see http://www.peachparts.com/shopforum/showpost.php?p=2171548&postcount=259), with a small leak in the top of the fuel tank.

so I guess what I'm saying is that because I'm getting better fuel economy than predicted for full load operation, I must not be as close to full load as I think I am (ie, my fuel settings must be somewhat de-tuned right now).

the timing of this is somewhat coincidental, as just last night I started working on a DIY flow meter to measure fuel consumption in real time.

its also pretty amazing how fuel efficient the TDI engine is in comparison. The OM617 at full load achieves 260 g/kWh, where as the TDI achieves just under 200 g/kWh at full load. that's 23% better fuel economy.

[Image: ALH_BSFC_map_with_power_hyperbolae_268AF...E40A3F.bmp]

[Image: ALH_BSFC_map_with_power_hyperbolae_268AF...E40A3F.bmp]

RE: OM617 SAE Paper - cell - 02-16-2010

so it turns out the UT engineering library has this article

[Image: sae.jpg]

and it has a bsfc map!

[Image: om617a-bsfc.jpg]

*does the happy dance of joy*

RE: OM617 SAE Paper - cell - 02-16-2010

(02-16-2010, 08:06 PM)GREASY_BEAST It must have a hell of a drag coefficient to be bogging down that bad on the highway!

bingo

keep in mind that a fuel economy of roughly 17 mpg (assuming fixing the leak at the near top of the tank bumps me up to 17) is about a 50% improvement over the mileage I was seeing with the original gasoline engine in that truck, so its all a matter of perspective Smile

(02-16-2010, 08:06 PM)GREASY_BEAST Given adequate air, should the 2400rpm max-efficiency point stay the same for any reason?

well, now that I look at the bsfc map, it looks like the point of peak efficiency is actually about 2250 rpm, at about 80% load.

i'm not sure what would happen if you increased the boost and fuel beyond what they originally considered "full load", but I'd be very interested in finding out. there is another section of the article where they touch on the fuel economy difference between the NA version versus the turbo version of this engine. So i'd imagine you could extrapolate from that.

I went back and took a higher quality picture of the map and replaced the above image.

Here is my interpretation of the "line" of increasing power you'd follow for maximum efficiency:

[Image: om617a-bsfc-efficiency-line.jpg]

[Image: om617a-bsfc-efficiency-line.jpg]

[img]