I'm curious what the limitations are to increasing boost on these engines (well, the OM602 specifically).


My (rudimentary) understanding is that more boost won't increase power on stock fueling, so it's mostly a pointless endeavor anyway. But beyond being pointless, is it bad or dangerous to the engine? I suppose it must be, since early '602s had an overboost protection circuit (although, strangely, my '92 does not).


But what if one were to increase fueling? I see a lot of guys running wild with larger elements on their fuel pumps and upgraded turbos pushing more boost. So I wonder - if I had more fuel, could I use more boost? And up to what point? What's the limiting factor here?


Sorry, turbo noob here.

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I think this guy was a bit past the reliability limit, twin charging (supercharger, turbocharger) with wastegates at 2.1 bar, and .4 bar boost at idle.

twin charged diesel mercedes - Engine & fuel engineering - Eng-Tips

https://www.youtube.com/watch?v=FFIfP5Y68z0&feature=youtu.be

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CC: NSA

All things are burning, know this and be released.

82 Benz 240 D, Kuan Yin
12 Ford Escape 4wd

You're four times

It's hard to

more likely to

concentrate on

have an accident

two things

when you're on

at the same time.

a cell phone.

www.kiva.org It's not like there's anything wrong with feeling good, is there?

1.5 bar.
https://www.youtube.com/watch?v=TNqLcBDR4JY

Comments on this video indicate stock NA engine, modified injection pump and larger turbo.

__________________
CC: NSA

All things are burning, know this and be released.

82 Benz 240 D, Kuan Yin
12 Ford Escape 4wd

You're four times

It's hard to

more likely to

concentrate on

have an accident

two things

when you're on

at the same time.

a cell phone.

www.kiva.org It's not like there's anything wrong with feeling good, is there?

The major limiting factor is Exhaust Gas Temperature. Without a way to monitor this, you can destroy an engine in short order.

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Sam

84 300SD 350K+ miles ( Blue Belle )

You'll melt a piston if you overboost from the EGT. These engines don't have intercoolers, so you'll absolutely get more EGT. Also, as you already know if you do not increase the fuel from the pump, you're wasting your time. Boost will do nothing.

I can't speak specifically to the om602 on this matter, but I know that people have seen performance gains from replacing the turbo on OM617 cars with a more efficient modern one. So you might gain something for your efforts.

The best answers to your questions however would probably be found at STD as they specialize is performance tuning of Mercedes diesels.

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2004 F150 4.6L -My Daily
2007 Volvo XC70 -Wife's Daily
1998 Ford F150 -Rear ended
1989 J-spec 420SEL -passed onto its new keeper
1982 BMW 733i -fixed and traded for the 420SEL
2003 Volvo V70 5 Speed -scrapped
1997 E290 Turbo Diesel Wagon -traded for above
1992 BMW 525i -traded in
1990 Silver 300TE -hated the M103
1985 Grey 380SE Diesel Conversion, 2.47 rear end, ABS -Sold, really should have kept this one
1979 Silver 300D "The Silver Slug" -Sold

Thanks, someone at STD recommended 1.5 Bar as well - I was thinking more like 1 Bar (15psi), but I guess we'll see.

I'm tentatively planning to fit a new IP with 7.5mm elements (but nowhere near max fueling). I'm told that EGT will actually be lower than stock, because of an earlier, shorter, more efficient injection duration. I'm also reading that more boost can lower EGTs (relatively) if overfueling. I don't know, I'm hearing lots of differing opinions - if I follow through on this I'm planning to monitor EGTs just in case. Just trying to figure out a starting point for the wastegate.

Thanks, I'm over at STD, too. It's hard to get really good info over there sometimes, though, because my planned build is quite conservative compared to most.

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Why not a twin scroll setup?

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1998 Ford Escort ZX2 5 speed - 279,000 miles My Daily

1992 Mercedes 300D 2.5 202,000 - Pure junk
2000 Mercedes E320 Black - 136,000 miles - Needs repair

Don't forget to grease the screw and threads on the spring compressor.

Pointless on the stock turbo to turn up boost - it'll just be a hair dryer. Now if you upgraded turbo, that's a different story - as you can see in the videos above

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1978 300D, 373,000km 617.912, 711.113 5 speed, 7.5mm superpump, HX30W turbo...many, many years in the making....
1977 280> 300D - 500,000km+ (to be sold...)
1984 240TD>300TD 121,000 miles, *gone*
1977 250 parts car
1988 Toyota Corona 2.0D *gone*
1975 FJ45>HJ45
1981 200>240D (to be sold...)
1999 Hyundai Lantra 1.6 *gone*
1980s Lansing Bagnall FOER 5.2 Forklift (the Mk2 engine hoist)
2001 Holden Rodeo 4JB1T 2WD

I believe this is the poorest quality video I've ever seen on youtube. Wow that was hard to watch. They say a picture is worth a thousand words, but in this case, I'd prefer the words.

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1998 E300 turbodiesel

America's Rights and Freedoms Are Not The Enemy!

That is what you call filming with a potato.

I have a 603 so it might be a little different, but like you, I am at a conservative 90cc with 6mm elements and don't get much feedback on STD.

I have been told by pump builders that the limit on 603s is 2.5 bar boost, and that is due to the headgasket. If you swap that out, you can run more. I suspect the 602 is similar but I'd maybe assume it can handle a bit less.

I am running about 19-20 psi on my engine now and it is fine. No smoke at any rpm. You should not need more than that for 90cc, in fact, you might even need less since the 7.5mm elements are more efficient. Really the boost is to make up for lost efficency in the upper rpms.

Another factor to consider is airflow from the turbo. People run huge HX40s that flow like 60lbs of air but only need 40, which is a waste. It also seems people are running Gt22vs that flow like no air at all and seem to think this is fine for 300hp. It generally isn't. A turbo cannot make more power than the air it can provide, and increasing boost will eventually just make it hotter and less efficient. So up to a point, increasing boost on the stock turbo is indeed pointless.

Another huge thing that I personally think is completely overlooked is turbines and their housings. This is usually the limiting factor when people can't make more power but the compressor should be able to...
I think this is another reason people say upgrading to huge turbos makes their cars seem faster...yes, because you can flow the air out better. And yes, I upgraded my HX30 to a big borg warner and the upper RPMs are great, but I attribute that to the turbine and housing more than the compressor.

If you are going to upgrade the stock turbo, if you could even, I would try to find a better turbine wheel and bigger housing for it in addition to a better compressor, but at that point it would likely be cheaper to get a new one and make an adapter if needed.

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Dan
2005 E320 CDI - 246k
1987 300SDL TD05-16g, Herlevi pump, Elbe manifold, 2.47 LSD - 213k
Past: 1987 300D - 264k

Thanks for the feedback. My tentative plan was to rebuild the stock T25 as a Big T28 (upgraded turbine & compressor wheels) and limit boost to something like 15psi (~1 Bar). But now I'm wondering if I should be going for more like 1.5Bar?

Good to hear that you're not making any smoke. I'm not really interested in rolling coal, lol.

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'Does the T25 to T28 "Upgrade" include an option for Roller Bearings ?

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'84 300SD sold
124.128

Not that I'm aware of. There is something about upgrading to a 360° steel thrust bearing from the stock 270° bronze bearing, but honestly I have no idea what that means.

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