Just wondering if anybody has actually used 4l80e locked converter engine braking for more than 2-5 years successfully. Im just wondering why they didnt enable it from the factory since it saves fuel.
Just wondering if anybody has actually used 4l80e locked converter engine braking for more than 2-5 years successfully. Im just wondering why they didnt enable it from the factory since it saves fuel.
Actually it does not save fuel. Being able to coast with minimal engine breaking saves fuel. That is the reason the 700r4/4L60E has an over run clutch in OD.Originally Posted by kingtal0n
That being said I have had my 4L85E setup with tow/haul since 2013 and have it set to agressively downshift for engine breaking at 0% TPS when it is in tow/haul. On a 6% downgrade at 12,000 lbs GCVW I rarely even touch the brakes.
Wait a minute. When you downshift a manual transmission vehicle, you convert the kinetic energy of the moving vehicles mass into rotational energy to keep the engine spinning. This is how you can keep the motor spinning with 0% duty cycle, with no fuel injector pulse, for a long distance in a manual transmission vehicle.
As opposed to having the engine at idle while you coast in neutral, which would waste fuel.
I have no reason to assume it would be any different with an automatic transmission. Engine braking saves fuel by converter kinetic energy of moving vehicle into rotating work to keep the engine spinning so you can shut off the injector. I've successfully done it with 4l80e but was worried there is a flaw or problem with doing this since the OEM didn't do it. It should be worth approx 1-3% fuel economy if done right.
You are not factoring into account that you are fighting compression and friction, even without injecting fuel.
You'll coast for longer in neutral than you will in gear with the engine off this is true for a manual or an auto with the tcc locked.
Last edited by VodeAn; 04-23-2018 at 02:57 PM.
Depending on your DFCO settings you may not actually be turning all the fuel off. So if you test what I said be sure you are fully shutting the engine off/fully cutting fuel.
Using DFCO as a "lean burn" mode is possible but now you aren't talking about the engine being off.
Yeah but nobody ever has a chance to do this in traffic.
i.e. I see a traffic light and I need to use brakes (throw kinetic energy away) but instead, I use engine braking (recovers kinetic energy, saves fuel) Since the vehicle has to stop anyways.
How do I set/ensure DFCO to turn fuel OFF? How do I test this?
Depends on the driver, TBH. Someone that is not 30 ft off the bumper of the car in front can let off the throttle and coast before braking. You get better mileage being able to actually coast. Its called maintaining momentum.
Then again that is why in the case of a vehicle with a 700r4/60E or even factory 4L80E you can manually select 3rd. 3rd applies the over run clutch and allows engine braking.
You can also buy a kit to automatically hydraulically apply the over run clutch in any gear except OD in a 4L80E even with the shifter in Drive rather than 3rd. Set your 4-3 coasting downshift at a high enough speed to give adequate braking. Just a thought. The same valve kit makes the transmission itself stronger in Drive. There is a reason most performance guys in the know shift down to 3rd before the romp on a 4L80E.
So everything aside it should be no big deal if I enable engine braking with this 4l80e then, it sounds like.
I will turn it back on and let you know if anything bad happens. I just wish I knew how to "Make DFCO" Work properly and completely turn fuel off. How 2 do that ?
basically DFCO pretends to be a fuel cut, but it shows 0.5% duty like a standard in DFCO and I get a weird smell. suppose I will pull injector fuse verify its really fuel (if not an o-ring leak but yeah right) then reduce minimum injector ontime i suppose. You'd think DFCO would override but maybe not I guess.
Last edited by kingtal0n; 04-25-2018 at 09:05 PM.
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