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Old 06-07-2019, 07:57 PM   #20 (permalink)
eco....something or other
Join Date: Jul 2009
Location: Colfax, WI
Posts: 705

wood hauler - '91 Ford F-250
Team Pontiac
90 day: 18.97 mpg (US)

Rav - '06 Toyota Rav4 Base
90 day: 26.52 mpg (US)
Thanks: 36
Thanked 54 Times in 41 Posts

We have been keeping an eye on mileage since removing the balance shafts and installing the trans cooler to see if there is any change.

Before was ~21-22 mpg After is ~26 mpg over 3 tanks, and one of those tanks was used to haul a 16 ft fishing/ski boat!

That's a big jump!

The balance shafts are gone and that will increase mileage a little, yes, but it's bigger than that. With the shafts gone, the engine has more power available through the entire rpm range. We have noticed that the increased power is keeping the rpm's lower and allowing earlier shifts. This is why there is such a large increase in mileage. It's a cause and effect series. The shafts alone might account for 1-2 mpg, but when the whole system works better, the effects are multiplied.

Less engine drag=better economy, more power available/earlier shifts, less downshifting on hills

All of those things contribute to better economy more than just the reduction of engine drag alone, so it is compounded as it changes how the entire system works.

The whole driving experience is different with the balance shaft delete and trans cooler. It's just a pleasure to drive. There is no need to wind the engine out to 4,5 or even 6k because it has the power down low to do the same thing. Even towing the boat, there was no need to wind it out, it just goes. You couldn't even tell the boat was there at 60 mph. Just amazing. I could definitely tell when I was towing before the mods. The engine worked very hard and would downshift all the time.

The cooler is amazing, and I think it is actually helping to cool the engine coolant with the atf. Temps are ~140 in the pan according to my temp gun.
It feels noticeably smoother with the cooler atf providing more cushion in the transmission and better lubrication. Gear changes are silky smooth, and firm. I like the rav even more after driving it like this. My wife and I have tiffs over who gets to drive it, even if we are both in it at the same time. We need another one, lol.

It feels like a totally different car, period.

Another update:
It was 90* today and we were running errands with the A/C on almost the whole time. The fuel mileage still seems to be doing well.

1991 F-250:
4.9L, Mazda 5 speed, 4.10 10.25" rear
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