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Topic: How fast is too fast" (Read 1507 times) previous topic - next topic
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Re: How fast is too fast"

Reply #25 –
Yahoo Message Number: 88238
Stop and go driving we get about 20 to 22 mpg at 4000 ft altitude. On the interstate about 29 at 70 mph. Driving the high ways between 60 and 65 gives us 30 + , between 55 and 60 about 33 according to the computer and unlike the Silverleaf the computer in the CR-v is always right, so far. Its also amazing how much your milage will improve by inflating your tires to 35 lbs from 28 or 29, but then the ride is like a pickup. I wanted a new Odessey, but the Cr-v does for us about 95% of what the Cr-v and costs a bunch less to operate. I do miss being able to haul 6 to 8 people though at rallies, etc and the rear air-conditioner vents. TWI 2012 CRV

Re: How fast is too fast"

Reply #26 –
Yahoo Message Number: 88294
I have told that there is very little danger of damaging the engine due to the safe guards built into the Allison. I routinely hit that for a brief period but it then comes back down to about 2250 where it seems to settle.

Re: How fast is too fast"

Reply #27 –
Yahoo Message Number: 88295
Per

I think there is a difference when cruising on the relatively level terrain and when climbing long grades. In my C-9 I also run about 1500-1600 rpms on the level: but, I have to really drop it down when climbing. As I said before I was bumping rpms up to 2000 rpm but getting excessive exhaust temp error codes and told to drop the rpms to closer to max torque which is around 1200 rpms. I now try and keep it around 13-1400 rpms and I have noticed that it seems to like the result but I sure do climb a lot slower than I like. Those tags add a lot of weight.

Dan 2006 Allure 31348 (traveling in the truck slow lane)
 

Re: How fast is too fast"

Reply #28 –
Yahoo Message Number: 88300
On my ISC and ISl 400 the up shift point with the exhaust brake in one case and the engine brake in the other was 2600 rpm. When I descended Wolf Creek Pass in the past before putting the coach on a diet and changing to the CR-v, I would be in second gear right at 2550 most of the way and having to tap the brakes now and then. I would even get a warning yellow light forcing me to upshift, apply the throttle for a few seconds to increase oil circulation, and then continue. >Going down the grape vine or descending either side of Eisenhower tunnel on I-70 in Colorado or that beautiful stretch heading east on I 70 in Utah cause me no issues even though I might be turning 2500 in 3rd or 4th. I imagine the ISX owners the limit is probably more like 2450. I' ve seen my engine up shift at full throttle at or approaching 2200 rpm and ISX 600's on test drives at 2050 so the limits of big blocks to medium blocks isn't that much different. So 2250 should be no cause for worry. Just don't touch the throttle until you up shift.

There was an instance when the accumulator section of the injection pump was allowing diesel to enter the oil system of the engine, thus thinning it. So, when I went to use the engine brake it wasn't very helpful and I had to use my service brakes till I could get to Cummins for repairs. Since I have changed from Rotella to Valvoline my down the road oil pressure is back over 40 lbs and when I descend grades the oil pressure approaches 65 lbs. So when the coach shifts down to second going down at 9 or 10% grade you feel as if you are dragging a large anchor; there is so much braking force with out touching the brakes. I'll try Wolf Creek and maybe Slumgullion pass this summer and let you know if there is a change in the results.

TWI 2004 Intrigue 11731 and Allure 30255