722.6 w210 stall speed

zeeman

10-04-2018, 03:12 PM #11

(10-04-2018, 07:51 AM)jav1 With respect to Zeeman, I agree that he is generally correct but I disagree on some finer points as follows. There's a generally accepted concept that diesels produce more torque than gasoline versions of engines within the same vehicles. Surely if you look at heavy duty trucks on offer from the US big 3, this is clearly the case when comparing Power-stroke, Duramax and Cummins to there gasoline counterparts.

Having said that, torque, as a unit of measure, is the same "force" whether produced via compression ignition, spark ignition or electric power. So while it can be generally and truthfully said that diesel torque converters are a lot stronger than gas converters, I feel this is a bit off point. The OM606.XXX in stock form, can hardly be compared to the heavy duty diesels employed here in the states. It is a (comparatively) higher RPM, lower torque diesel that compares better to our larger gasoline engines than it does to our behemoth truck diesel engines. In fact, the OM606.962 has a lower torque rating than many gasoline truck V8 engines.

I do believe that by diesels nature, the compression ignition event may produce higher peak crank acceleration transients than a higher torque gasoline engine, BUT- I question that this will have any impact on torque converter longevity since it is a fluid coupling... and these transients should be absorbed by fluid flow and not transmitted directly such that mechanical failures would be eminent. Now- this is just my "opinion" as I have no data to prove this view but I am a mechanical engineer, and I'm fairly well versed in fluid dynamics as well as cyclical load testing/failure analysis.

One area of concern is the lock up clutch. Converter manufacturers do publish the overall torque rating for a converter, BUT they don't publish the lock up clutches ultimate torque rating. I presume because the lock-up clutch is NOT intended to transmit HIGH torque demand events... it's usually unlocked in those cases to allow the fluid coupling and torque multiplication qualities of the converter to do their job. Also- lockup torque can be increased by manipulating system pressure to a degree. I think problems can arise in these diesel conversions because we're building a hybrid system by grafting a diesel engine where a gasoline engine used to be... and the truck/cars PCM may be trying to control the transmission/torque converter using input parameters that are likely different than originally intended. I feel lock-up clutch/torque converter failures COULD be as much related to: less than optimal control strategies, AND weak/failing internals when too often, they are blamed on the "diesel engine" itself.

Unless you have a custom converter built, I doubt you will find a diesel torque converter with a high stall speed since most USA diesels are larger, low RPM, torque monsters. And- if you use a low stall diesel torque converter, while I'm sure it won't fail, I doubt you'll be happy with the performance. IMHO- I would use a high stall gasoline torque converter that is rated in excess of the torque your engine produces and make sure the control strategy is working properly IE. that lock up occurs only when the transmission slip is less than 5% and engine power demand is below 50%.

That's my .02c.

My point was you are not going to find a gas torque converter with the stall speed you need, that will hold up to the diesel. The torque power curve of the OM 606 is much different then a gas engine power torque. Hence the need to have a gas stall speed with the diesel internals.

Also what is controlling the shift points now? Do you have an after market controller? Diesel shift points are different from gas also.

Even though both are a fluid coupling the input shaft is connected to a clutch hub in the converter that is designed for a gas engines torque curve.

And I will repeat the Diesel torque is different from gas torque, the piston power stroke in a gas engine is not the same. In fact the OM 606 fires after TDC.

If you notice on the OM 606 the alternator pulley has a one way clutch designed into it. This for the different harmonics of the diesel on deceleration.

I have already given a name of a company that can do this earlier in this blog. This is not rocket science, just common sense.

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