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+--- Thread: Question for the people with CM870's (/showthread.php?tid=6921)
Question for the people with CM870's - Rtrucking - 01-13-2021
So one of the questions is, what water temp are you guys seeing on your truck's, I can run down the road and only see about 175-180ish, but I'm thinking it's because of the truck I have (Rawez favorite old Antique iron type of truck) it's a 378 Pete with the oilfield cooling package on it and not lying it take 16 or 17 gals of coolant (I know not the best mpg or the best to the wallet), and what's the best range to run the boost at for better mpg for the 870's, I know the 871's it's best to keep it down at about 10 or less but I was just curious about it, then the last one when the water temp does come up to 195-200 range I can run with less boost and it just seems to run better.
RE: Question for the people with CM870's - Rawze - 01-13-2021
The water temp should be 185 ... nothing much more or less unless your climbing a hill and working the engine hard.
If you have too much cooling in the front end on winter days i9n the extreme cold then one of those rad. shields will likely be your friend.
(max allowed boost)...
The CM870 is just like the CM871 ... no more than 38 psi boost no matter what, as anything more will cause engine damage and/or severely shorten its lifespan.
As far as boost goes otherwise, keeping it to a minimum as much as possible (good programming and your right foot) is best for fuel efficiency. If it has custom (or delete) programming in it, one can only guess as to how sensitive the boost levels may have been tweaked to. If they aren't quite right, the boost will be touchy or lazy in the lower fuelling ranges making for less fuel mileage than should be expected. One way to test to see if the lower-end boost levels and things are right would be ... next time you drive it bobtail, set the cruise at 50 mph on a completely flat stretch of roadway ... the instant mpg should be teetering in the upper 10+~ish range and boost should be zero on that model truck. If it hovers around the 7 or 8 mpg range and there is anything but absolutely zero boost ... then, it is likely providing too much boost/positive-pressure too early, causing eff. losses.