Understanding Engine brake
01-08-2019, 10:34 PM
#11
Junior Member
Pretty sure we have exhaust brake/ engine brake but only when the trailer is connected, and in tow mode. It sounds just like a Jake brake on a big rig except it’s a v6 so way quieter but does slow the whole truck and trailer down dramatically. If I step on the brakes hard with the tranny in drive and no gears locked out, the rpms do jump way up when this is happening but it only does this with a trailer connected and in tow mode.
01-08-2019, 10:52 PM
#12
Junior Member
Tow mode is just a 'strategy' or program for the engine/transmission to follow. It basically changes the shift points (rpm) and the times that it shifts based upon different parameters including brake application, load, timing etc.. There is nothing in the engine that would manually retard the exhaust flow that would be present in a typical exhaust brake application. I will agree that the strategy that Ford employed is good, it down shifts and senses hills very well when in tow mode which is great, but it is still not a true exhaust brake.
01-09-2019, 08:13 AM
#13
Senile member
Pretty sure we have exhaust brake/ engine brake but only when the trailer is connected, and in tow mode. It sounds just like a Jake brake on a big rig except it’s a v6 so way quieter but does slow the whole truck and trailer down dramatically. If I step on the brakes hard with the tranny in drive and no gears locked out, the rpms do jump way up when this is happening but it only does this with a trailer connected and in tow mode.
Where do these ideas come from?
01-09-2019, 08:57 AM
#14
Senior Member
Pretty sure we have exhaust brake/ engine brake but only when the trailer is connected, and in tow mode. It sounds just like a Jake brake on a big rig except it’s a v6 so way quieter but does slow the whole truck and trailer down dramatically. If I step on the brakes hard with the tranny in drive and no gears locked out, the rpms do jump way up when this is happening but it only does this with a trailer connected and in tow mode.
Exhaust braking and engine braking are 2 different things. The engine braking simply means the transmission will stay in a lower gear to help control speed. Every vehicle I have ever driven (and probably every one ever built) has engine braking. It's just that on older cars/trucks you had to manually downshift the auto trans. In newer trucks with tow/haul mode, the computer can do it for you.
Gas F150s absolutely do NOT have an exhaust brake.
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chimmike (01-09-2019)
01-09-2019, 12:27 PM
#15
What you are experiencing is a 'normal' characteristic. Looks like you have the 6-speed tranny, as do I. You will find that once the transmission gets close to normal operating temperature it will hold any gear. Until then I think it is leaving the torque converter unlocked in an effort to produce more heat to bring it up to operating temperature faster. Problem is, going downhill there is no power input from the engine on the torque converter and little heat is produced. The transmission actually has a fluid heater that uses the engine coolant. but again, going downhill the engine is not working hard so it takes time to heat up.
For me, typically around a 40 - 50C (104 - 122F) transmission temperature, the torque converter will lock. Until then it will just let the RPMs go wild. As it warms it may lock and unlock as you have experienced. There is no rhyme or reason to it. I think most people are unaware of this because they do not decent a steep grade right after starting their truck, as this is the only time you would notice it. I live in a town that has a 600m verticle drop to the next town with 8% -10% grade so this really annoys me, particularly in the winter.
So what can you do?
1) You can let the truck idle for a little while and let the transmission fluid heater warm the fluid up.
2) Drive around a bit, in 4x4 if you can, particularly uphill and that will warm the tranny really fast, then descend.
I wish there was an override on this. The truck knows what angle it is at, so once it exceeds a certain angle it could lock the torque converter. Or if in tow/haul the torque converter locks no matter what.
* Above is my theory on this and is based on my personal experience, but I am not a Ford tech. This would be worth asking your service department about.
For me, typically around a 40 - 50C (104 - 122F) transmission temperature, the torque converter will lock. Until then it will just let the RPMs go wild. As it warms it may lock and unlock as you have experienced. There is no rhyme or reason to it. I think most people are unaware of this because they do not decent a steep grade right after starting their truck, as this is the only time you would notice it. I live in a town that has a 600m verticle drop to the next town with 8% -10% grade so this really annoys me, particularly in the winter.
So what can you do?
1) You can let the truck idle for a little while and let the transmission fluid heater warm the fluid up.
2) Drive around a bit, in 4x4 if you can, particularly uphill and that will warm the tranny really fast, then descend.
I wish there was an override on this. The truck knows what angle it is at, so once it exceeds a certain angle it could lock the torque converter. Or if in tow/haul the torque converter locks no matter what.
* Above is my theory on this and is based on my personal experience, but I am not a Ford tech. This would be worth asking your service department about.
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chimmike (01-09-2019)
01-09-2019, 05:31 PM
#18
Jake Brake and exhaust brake are for diesel engines.
Gas engines pull against a closed throttle, which is the largest portion of engine braking.
You can use a lower gear as described above. Since we have 4 wheel ventilated disc brakes, you should be able to control vehicle speed to the point where engine overspeed is avoided. Especially with a 2.7, and I assume the 3.3, you just have too small of an engine to provide much braking.
If you wear your brakes out, that's an easy fix.
If your run your motor at 6000 rpms all the way down the hill to "save the brakes", that might work. Or, it might be quite a bit more expensive than brakes.
Serving suggestion....
Gas engines pull against a closed throttle, which is the largest portion of engine braking.
You can use a lower gear as described above. Since we have 4 wheel ventilated disc brakes, you should be able to control vehicle speed to the point where engine overspeed is avoided. Especially with a 2.7, and I assume the 3.3, you just have too small of an engine to provide much braking.
If you wear your brakes out, that's an easy fix.
If your run your motor at 6000 rpms all the way down the hill to "save the brakes", that might work. Or, it might be quite a bit more expensive than brakes.
Serving suggestion....
01-09-2019, 05:43 PM
#19
Jake Brake and exhaust brake are for diesel engines.
Gas engines pull against a closed throttle, which is the largest portion of engine braking.
You can use a lower gear as described above. Since we have 4 wheel ventilated disc brakes, you should be able to control vehicle speed to the point where engine overspeed is avoided. Especially with a 2.7, and I assume the 3.3, you just have too small of an engine to provide much braking.
If you wear your brakes out, that's an easy fix.
If your run your motor at 6000 rpms all the way down the hill to "save the brakes", that might work. Or, it might be quite a bit more expensive than brakes.
Serving suggestion....
Gas engines pull against a closed throttle, which is the largest portion of engine braking.
You can use a lower gear as described above. Since we have 4 wheel ventilated disc brakes, you should be able to control vehicle speed to the point where engine overspeed is avoided. Especially with a 2.7, and I assume the 3.3, you just have too small of an engine to provide much braking.
If you wear your brakes out, that's an easy fix.
If your run your motor at 6000 rpms all the way down the hill to "save the brakes", that might work. Or, it might be quite a bit more expensive than brakes.
Serving suggestion....
There's also no reason the computer couldn't open the throttle while using engine braking. The problem is that it has no way to effectively open the exhaust valve before the compression springs the piston back down. And gas engines are generally smaller and lower compression.
Last edited by RX1Cobra; 01-09-2019 at 05:46 PM.
01-09-2019, 05:52 PM
#20
I know what a Jake Brake is and how and where it works. Regardless that it's found on diesels doesn't not make it an engine brake. So engine brakes do exist.
There's also no reason the computer couldn't open the throttle while using engine braking. The problem is that it has no way to effectively open the exhaust valve before the compression springs the piston back down. And gas engines are generally smaller and lower compression.
There's also no reason the computer couldn't open the throttle while using engine braking. The problem is that it has no way to effectively open the exhaust valve before the compression springs the piston back down. And gas engines are generally smaller and lower compression.
Yes, the computer can open the throttle during engine braking, but so far it hasn't on my truck.
There is "...no way to effectively open the exhaust valve....". Right, that would be for a diesel engine, not a gas.