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LoveLearn
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Loc: Corner of SD, Ia. & Neb.
Questions about Mercedes MBE 900 series engines
#2022397 - 10/03/04 05:44 PM

I've been looking for fuel usage vs. power output curves for any of the Mercedes MBE 900 series engines. So far I've found none. I find lots of charts plotting horsepower and torque against RPM for various models from that series, but nothing showing BSFC. I haven't even found a table of values comparable to what Cummins publishes with which we can generate our own charts. Has anyone found more complete performance data for these engines?

I expect to be able to find fuel burn vs. horsepower values just as Cummins is so good about providing. I don't expect to find published internal friction horsepower curves vs. rpm. That would be "too good to be true." If anyone has the internal engine friction curve for any Mercedes MBE 900 4 or 6-cylinder engine or for any of the Cummins "B series" family of engines, I would love to have a copy. Please send a Private Message note if you can help in this search.

Mercedes surely has been busy increasing power making capabilities on these engines. Older literature shows the 6-cylinder 6.4 liter version of this series available factory rated at 190, 210, 230, 250 and 280 horsepower. The 2/3 sized 4-cylinder 4.3 liter included 150, 170 and 190 horsepower versions. Two similar 4-cylinder 190 hp versions show 520 lb-ft,. of torque. One develops 520 lb-ft @1200 rpm, the other 520 lb-ft @1400 rpm. Those two torque ratings at stated rpms recalculated as horsepower are 119 hp @1200 rpm and 139 hp @1400 rpm! Those are damned impressive values to me. One of these engines should be incredibly efficient pulling a 6-pole generator to produce 60 cps since that requires exactly 1200 rpm. These 4-cylinder engines probably have low internal friction at those rpms, yet they are impressive power makers. After all, 80% of internal engine friction is piston and ring sliding friction inside cylinder bores. Despite all the benefits of multiple piston designs, when it comes to low internal friction, the fewer the pistons for any given displacement, the lower the internal friction. That's why none of the 3 & 4-cylinder diesel 5 kW gen sets can run on as little fuel per hour as the best single cylinder diesels consume while developing comparable outputs. My 7.3 Navistar engine curves only show 96 hp @1400 rpm, much less than 139 hp from this 4-cylinder MBE 900 family member. Yet at any comparable rpm, sliding 8 pistons inside bores to generate 7.3 liters of swept volume surely generates more internal engine friction than sliding 4 pistons inside their bores to produce 4.3 liters of swept volume.

An "In Service Online," Aug. 2, 2004 news story on them says, "Freightliner medium-duty M2 trucks are now standard with Mercedes-Benz MBE900 diesel engines in ratings up to 330hp." I haven't found performance charts for this newest 330 hp version, but I have found a news story indicating that it is a new larger displacement 7.2 liter I-6 926 member of the 900 series family. I found nothing to indicate that a proportionally powerful 4-cylinder version with 220 hp. is being offered in their new and larger 4.8 liter 4-cylinder size, but that would make perfect sense. That would combine lower 4-cylinder internal friction with enough horsepower to handle peak loads most pickup truck drivers need. With tall gears and a manual trans that should be an incredible mpg performer. Maybe running some device to average power pulse peaks like a Voith Hydradamp should be run between the engine and the transmission so all that highly efficient low rpm output doesn't trash the drive train. Pulse peaks have been causing a lot more trouble than high average torque, so pulse load averaging devices should be becoming more popular in my opinion. Some people have said that you can't use engines where they make the most horsepower-hour per gallon because the power pulse peaks they produce when operated facing those loads kill drive trains. Pulse peak averaging devices exist. Claiming that we can't use them that way sounds equivelant to saying that we can't go outside when it's zero degrees F. because we are unwilling to wear a coat. Insulate the drive train from those high pulse peaks and use that peak efficiency. If they are smart enough to insulate their bodies from winter cold with coats they ought to be smart enough to insulate their drive trains from torque pulse peaks with torque averaging devices. I've never seen the air in a pneumatic spring worn out yet.

The Freightliner site says, "The Business Class M2 106V comes standard with Freightliner’s proprietary 6.4-liter Mercedes-Benz MBE 906 engine which offers up to 260 horsepower, 520-700 pound-feet of torque, excellent fuel economy and the best power-to-weight ratio in the industry. The 7.2-liter MBE 926, with up to 330 horsepower and 800-1000 pound-feet of torque, is available as an option." So I gather that both displacement per cylinder series engines will be produced in the MBE 900 family for a while rather than simply replace the 6.4L with the newer 7.2L and replace the 4.3L with the newer 4.8L.

I found the following update report published in January 2004: "The MBE900 will continue to be available in four-cylinder and six-cylinder versions, but will have two new displacements -- a 4.8-liter four-cylinder and a 7.2-liter six-cylinder."
http://inserviceextra.firechief.com/ar/firefighting_manufacturers_change_mediumduty/

I'm tried of all the verbiage about these engines without full supporting performance data detailing their fuel usage at stated rpms and horsepower levels. If I were controlling Mercedes engine information disclosure, I'd publish the full BSFC map set just as aircraft engine makers do. I'd also publish their internal engine friction curves. I'd not worry that many end users wouldn't instantly know how to interpret these values. Many would learn. Those who were interested would learn. Those who weren't sufficiently interested would be content with someone else's interpretation anyway. All diesel makers generate and use these charts to guide their engine development work anyway. So they already have this data. Why not publish them? Please don't tell me they can't afford the hard drive space maintaining them would cost for their internet sites. That cost would be less than a McDonald's cheese burger. It makes no sense to me and offends me that engine companies implicitly take positions equivelant to telling consumers "trust us, all those fuel usage cost numbers are excellent throughout our product line." By implication, that's what they are saying. As much as they charge for these engines, they should publish full performance curves for every model they sell so buyers can make the most informed choices possible. Some people are "specing" 200 to over 1000 truck fleet orders per year who aren't being given the BSFC charts needed to compare performance between alternate candidate engines. Is that any way to compete for big-dollar orders? To me, that's just flat wrong. There's no excuse for hiding this information which their engineering departments already generated during engine development. Navistar is just as bad. Cummins is better, but hides internal engine friction charts.

Just my opinions,
John "LoveLearn"

B1powered
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Reged: 09/14/03
Posts: 792
Loc: South Central Pa.
Re: Questions about Mercedes MBE 900 series engines new
#2022419 - 10/03/04 06:10 PM

Not sure, but Every driver who has had a MB diesel I've talked to seems to have everything good to say for them.
They must be prety good on fuel

luckuslucas
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Posts: 32
Loc: Johnson, Vermont
Re: Questions about Mercedes MBE 900 series engines new
#2024575 - 10/04/04 09:47 PM

One place I can think of that shows some specs on these motors in the Kassbohrer site - http://www.katvpb.com/products_pisten_bully.asp - they run MB engines in all their snowcats, from the 170hp 4.2L up to the 12L 430hp. They don't show any internal friction data, but there are some numbers. Now the 7.2L OM 926 LA puts out 330hp and 960 ft-lbs of torque, wouldn't that be nice to have in a pickup...

Gone Fishen
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Reged: 04/28/99
Posts: 1930
Loc: Lost Wages, Nevada
Re: Questions about Mercedes MBE 900 series engines new
#2033599 - 10/10/04 10:28 PM

I have worked most on the MBE 4000 series engine. The series 900 is avail in both 4 and 6 cylinder engines. All electronic of course. This year of course they are EGR engines. The local school dist is getting 35 for test with WT transmissions. They are NOT avail. for purchase for repowers or any other mods. The demand is to great and they cannot produce enough. The 900 is made In Germany only. Make sure you order one with 'constant-throttle' and exhaust brake at time of ordering. The cost is to great later after purchase. The 4000 series is made in South America.

LoveLearn
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Member # 19102
Reged: 01/17/02
Posts: 301
Loc: Corner of SD, Ia. & Neb.
Re: Questions about Mercedes MBE 900 series engines new
#2060255 - 10/26/04 07:58 AM

Thanks for the link to
http://www.katvpb.com/products_pisten_bully.asp
That's an interesting line of specialty products I'd never seen before.

I lifted the following from their Specifications section:
*****copy follows*****
Engine Type Mercedes Benz OM 904 LA
Number of Cylinders 4
Displacement 4.25 Liter
Horsepower 170 hp
Torque 485 ft lb (660 Nm) @ 1200 rpm
Average Fuel Usage 2.25 g/h (8.5 l/h)
*****end copy*****

485 ft-lb @ 1200 rpm = 111 horsepower @ 1200 rpm
(Horsepower = (Torque x Engine speed) / 5,252)
That's pleasing for a 4.25 liter TD

But their average fuel usage figure isn't useful since we don't know how much load that hydrostatic drive absorbed during their ratings tests.

Just based on published data curves I love comparing, the Mercedes MBE904-190 engine appears to be one of the most impressive production TDI engines in the world. This MBE904-170 is excellent too, but I'd prefer to play with the 190. Fitted into full sized pickups with only easily applied aerodynamic CD improvements, tall gears and and a manual transmission, 65 mph cruise would only require about 30 horsepower. An MBE904-190 pushing that load at about 1200 rpm would have about 110 available horsepower leaving 80 horsepower in reserve for dealing with hills etc. without downshifting. The worst "fly in the ointment" I see from this nearly ideal pipe dream load matching would be pulse loadings. 1200 rpm = 20 revolutions per second. A 4-cycle 4-cylinder produces 2 power pulses per revolution. So 1200 rpm or 20 revolutions per second would produce 40 power pulses per second! Wow. Better have some pretty fancy drive train isolation mounts and maybe some sort of power pulse peak torque limiting device inline with the drive train like a Voith Hydradamp.

That design path appears to imply well over 30 mpg in full sized clean CD pickups at 65 mph with probable drive train life of at least 500,000 miles. Most of this design approach has already been produced by Ford in Brazil. Has anyone seen any mpg reports on the Ford F-350 6-speed 3.9 liter Cummins 140 horsepower 4-cylinder offered as an OEM choice in Brazil Ford dealer showrooms? One of those with tall gears could approach this same ideal BSFC matching with one of Cummins great 4-cylinder engines. A hotter Cummins version with their 16 valve 4.5 liter 4-cylinder engine would be more competitive with these new Mercedes 4.25 liter engines.

If I controlled new product offerings at one of the big 3 US pickup makers, an offering along these lines would appear in US showrooms very quickly. With current fuel prices and the obvious efficiency and probable durability of this approach, early adopters would quickly brag about their new ride's economy. That would produce demand without big advertising budgets. Automotive periodicals would have a field day comparing it with everything they've seen before just as they did when the VW TDI set new performance standards for what was available in US markets.
John "LoveLearn"

Late edit addition.
4-cylinder 904 4.3 liters (262 cubic inches) makes 170 hp/420 lbs-ft;
4-cylinder 924 4.8 liters (293 cubic inches) makes 190 hp/520 lbs-ft.
I thought they were the same displacement. My error.
Now the 190 data points don't jump so far off the expected curve, but they are still very impressive.
2nd edit:
Just found curves at http://www.abco.co.za/MB3SA555.pdf
The torque claim at 1200 rpm which translates into 111 hp. at 1200 rpm appears to match the larger 4.8 liter version rather than the 4.3 liter version. I now suspect the person posting information on the first site copied data from the larger displacement 4-cylinder engine rather than the 170 hp. rated version they say they are using. The 4.3 curve appears to show about 93 horsepower at 1200 rpm, whereas a proportionate reduction based on comparative displacements of 259/293 x 111 hp. would be about 98 horsepower. I still like the 190 hp. version better. Same listed weight but 34 more cubic inches. A lot of these may be fitted into school buses.

Edited by LoveLearn (10/26/04 09:49 AM)

Gone Fishen
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Reged: 04/28/99
Posts: 1930
Loc: Lost Wages, Nevada
Re: Questions about Mercedes MBE 900 series engines new
#2063957 - 10/28/04 12:58 AM

The Dodge guys did a little sneak a few years ago. This was overheard from a couple of factory guys. They got a Dodge and repowered it with a 904 MBE engine. They did the usual tests and then really did the test. They ended the test because they could not find anthing that would take the torque. Price did enter into the equalion also. Needless to say the 904 will NOT find it's way into the Dodge trucks here in the USA.
BTW Allison is beefing up their transmisson to take todays torque and of course allow for some minor changes in the future.

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