Cruising RPM. can it be to low ?
From a gas mileage point of view . Can cruising RPM be to low ? What would be a good RPM for getting the best mileage.? , for a mostly stock small block. Can the RPM be to low (under torque curve). With a set 2.76 or 3.23/ 27.4 dia tires / A500 with lockup/ .69to1 overdrive.
With the 2.76's I get a cruising RPM @60 of 1399.
With the 3.23's I get a cruising RPM@60 of 1641 (which I'm sure would be a better choice)
Would the lockup even be usable at 60 MPH at those RPM's ?
There are a few things to consider here.
1. If lockup gets the motor so low in RPM's that it builds heat faster that the cooling system can circulate it out.
2. If lockup comes on so early in the RPM's as to be a detriment to fuel economy. (Or lugging the motor causing detonation)
I have my lockup come in at about 75 mph and usually run about 80mph at 2,100rpm's or it's turned off and just run in OD just for those reasons.
It just made sense to try and keep it all close to what the vehicles the trans came out of ran.
To low of an RPM under load doesn't get your mechanical timing in, and you are running late timing compounding the low RPM heat problems.
Like I said, I try to keep the RPM's within the range the manufacturer meant it to be, as they have already done the R&D on it.
In my case that's in the low 2k's at 80 in lockup.
If I'm pulling a big hill with lots of throttle I'll drop it out of lockup just to get the R's up to were I know my total timing is in.