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Topic: Best speed, rpm and Peak Performance (Read 1366 times) previous topic - next topic

Re: Best speed, rpm and Peak Performance

Reply #25 –
Correct Pierce, Also have you ever had the experience of looking thru the turbo housing, clearly seeing the shape of the turbine wheel, while it is under full rated load, the turbo and most of the exhaust turns way past red,  the big problem is not getting cooked at the same time, but clearly visable can see the inner shape of the turbo, most recently was an older 855 Cummins at 350 KW on resistive load bank at 80%/full load, ran so nice, cleaned all the carbon clunks out into driveway smoking. Ha.
So nice to do this vs reading about it.
Dave M

Re: Best speed, rpm and Peak Performance

Reply #26 –
No, unfortunately I have not had that opportunity. I did have a MB diesel that would throw sparks out of the exhaust after climbing a grade and then heading downhill.

EGT maximum varies from engine to engine as many heavy duty diesels have a hollow piston crown and are cooled by a straight stream of oil from a nozzle below entering the crown and carrying off heat from the aluminum surface above. As engines wear out, the oil pressure may be less and not spray/cool as well. Another reason to watch the oil pressure gauge and check the oil level. Engines without the oil cooling have a EGT limit of more than a couple hundred degrees less. That's why we limited our MB turbo kits to 7 psi when the factory engines with the hollow pistons could run 14 psi.

Pierce
Pierce and Gaylie Stewart
'93 U300/36 WTBI
Detroit 6V-92TA Jake
1140 watts on the roof
SBFD (ret)

Re: Best speed, rpm and Peak Performance

Reply #27 –
Pierce, agree, For the last many years I think all turbo diesels, used piston cooling. Squirters, what ever, DDC, Cat, Cummins, Navistar M-B autos, would guess the VW TDI does also. Being a gear head ;D , I enjoy great designs, not just large, my love affair with the DDC stuff has been verrry good & exciting making fools out of the Cat gang, loved the "Here kitty kitty" days.  Sure not an economy thing, but very satisfying.
The reason I pick on the Cat boys, is becuz they just cant take it :D
Oh joy

Re: Best speed, rpm and Peak Performance

Reply #28 –
Michael if your offering the power charts to me I appreciate it but I also had a chart for the M11E in my coach which I have sold. I'm just an interested bystander now.
My chart showed torque dropping off above 1400 RPM and HP dropping off above 1700RPM.
I tried to keep it around 1400RPM for normal driveing and climed hills at 1700 in 3rd, 4th or 5th depending on what road speed was confortable.
1400 seemed to be a sweet spot for my engine.
Again, thanks for the offer.
John Duld
1995 U320C SE 40'

Re: Best speed, rpm and Peak Performance

Reply #29 –
John, you get to one point - question I had and originated from a comment in another thread.  I recall he dropped down a gear so that driving at 55 he kept rpm up higher than it might otherwise be.  Thinking along lines Bret mentioned, you might need to do to cool.  Otherwise I thought if you drove too long at low speed and below peak torque then the transmission would adjust itself (it would not let you lug the engine very long).

So, for you to keep it at 1400 did you just drive that fast or go down a gear.  I am thinking 1400 would be 70 mph?
Mike
2001 U320 4010 Build 5878 (Gus)
Wrangle Unlimited Toad
Nacogdoches

Re: Best speed, rpm and Peak Performance

Reply #30 –
hello Mike,
You always present... Good questions!

Not sure if my input will contribute, but..
I found I can drive in Economy mode, 6th Gear and then float around 1275 rpms at around 60 mph. (readout on my dash +/-).  and that is fine with me.

One can understand lowering the mph to get under the 'friction' element of wind speed on blunt fronts...., but then we have to change from 60 ish in 6th, to 55 ish in 5th.  In 5th rather than 6th, we are running similar rpms/(fuel intake) but less distance down the road.  Let's keep this conversation up to find middle ground on information.  Certainly, our coaches engine size will be important.

any thoughts?  Fuel numbers are worth noting, even if we choose NOT to follow them..  Just nice to know the #'s!

Coach Build # 5862/40'/2001/U320/Motorcader 17136

Re: Best speed, rpm and Peak Performance

Reply #31 –
The only time I really care about is climbing hills and yes I was in 5 th gear.
2025 Wanderbox Outpost 32 on F600 Expedition Motorhome
2015 Born Free Royal Splendor on Ford 550 nonslide version  for sale
Former Coaches  covering. 360,000 miles
1999 34 U270
2000 36 U320
2001 42' double slide U320
2018 Jeep Rubicon

Re: Best speed, rpm and Peak Performance

Reply #32 –
Mike,
Out on an interstate I would run at 1400 which indicated 65 on my speedometer.
On a two lane country I usually ran at 55 in 5th gear.
MPG may have actually been a 1/2 MPG better than at 1400 in 6th.
It didn't take much throttle and of course less drag.
My mileage ran from 8 to 10.
Usually figured on 8.5 average for trip planning.
John Duld
1995 U320C SE 40'

Re: Best speed, rpm and Peak Performance

Reply #33 –
Quote from: Bill Chaplin –
does a diesel engine reach stoichiometric ?
Old round engines were leaned to the lean side of stoichiometric and showed an increase in torque for less fuel burned, the cylinder head temp's actually dropped up to 30 degree centigrade

All right Bill, I understand stochiometry in chemistry but what the heck does it mean in Diesel talk.
The selected media item is not currently available.Kent Speers
Locust Grove, OK
1993 U300 SSE 40' (Restored at FOT 2009) Build 4323
720 watts Solar
6V92TA DDEC Silver Engine
2014 Subaru Outback

Re: Best speed, rpm and Peak Performance

Reply #34 –
Quote from: wolfe10 –
Bill,

I am not aware that diesel engines have a stoichiometric ratio. 

Unlike gasoline engines that must have very close to the "proper" fuel/air ratio (13- 14.7/1 air/fuel), a diesel can happily run very lean (or rich for more power and smoke!).

My fun car is a 1988 Benz 300D. My mechanic adjusted the arbitrary richness limit on the tnjection pump, so it is now capable of producing smoke on full throttle. It is now also capable of moderately fast acceleration, even while going up significant grades. I just have to keep an eye on thr rear view and back it off a tad if I see excessive smoke. All this and 34mpg, but only while driving slowly.

By the way, I think he toyed with the waste gate too, more turbo boost.
Tom Lang K6PG (originally  KC6UEC)
and Diane Lang
2003 38 U295 build 6209
2016 Jeep Grand Cherokee Summit Ecodiesel
still have tow-ready 2006 Acura MDX 
Temple City, California
Motorcade 16681 California Chapter President
SKP 16663 member of SKP Park of the Sierra, Coarsegold California
FMCA F071251
Retired electrical and electronic engineer