How does the engine brake work relative to downshifting and upshifting?

Jake won't work when the throttle or clutch pedals are pressed. With upshifting just turn it off for now. Downshifting you'll be pushing the throttle pedal to rev the engine so the jake will shut off and kick back on once you let the throttle off again.

 

If the engine brakes are active and you are attempting to downshift, engine brakes will slow engine RPM rapidity and frustrate your shift timing.

Practice downshifting with engine brakes off. Get the timing and shifting down, first. Then start using the engines brakes once your comfortable so you have better feel and control to be prepared for the changes.

I prefer the jakes latched to the brake pedal. This way a slight brake application will activate them when needed. Some just use the clutch pedal in the same regard.

 

On a manual, in shifting, the Jake will cause the rpm’s to drop much faster. So say you are shifting and develop a rhythm… accelerate, shift,1-2(rpm’s drop), shift, accelerate. With the Jake on, the rhythm feels like accelerate, shift, 1, shift, accelerate. The change in the rhythm may throw you off on your shifting, and suddenly, you’re jamming gears and bronco bucking like a rookie. Like everything else, once you learn the new rhythm, you will match timing and float through the gears.

Now, if you double clutch…?

 

I don’t shift up or down with the Jake on as it really screws with the timing. In fact, I keep it off entirely unless I’m going down a hill, or in heavy traffic.

 

You can shift at 1200 rpms and 1600 rpms. There is generally a 400 rpm difference between gears. When downshifting slow to 1200 rpm then step on throttle to bring up rpms to 1600 and it should go in gear. Because 1200rpm +400 is 1600 rpm.

Then just reverse to upshift, bring rpms up to 1600 rpm shift gear kinda slow when the rpms drop to 1200rpm it will go in gear.

 

Beyond messing with your timing, running with the engine brake on constantly is going to mess with your fuel economy.

Yes, there are some scenarios where running the engine brake and downshifting makes sense. I'd argue that driver error got the driver into that scenario in the first place but . . .

I believe in turning on the engine break when I need it and leaving it off otherwise.

 

Two thoughts - first is if you shift a DD15 like this you're going to get negative MPG. Like you're going to need a fuel tanker riding shotgun bad.

Secondly, while this works and I have taught guys just to do this (with rpms appropriate to the engine), it's shifting for people who need safety scissors. You can shift into any gear, at any speed, providing you can match the RPM. You can shift into any gear, at any RPM, provided you can match the speed. It's important to watch the gauges and listen to the sound of the engine and learn the shift points. That way a person can recover into any gear in any situation. Slowing to a stop but the light changes? See your speed, choose and gear, goose the throttle and you're running. Relying on the 1200/1600 limits the options a driver has.

 

It’s a little old shifting way since it was more for the S60 and N14. The 1200 rpm and 1600 rpm was just easier to remember. Learning each gear and road speed is better, but can be difficult at first.

On the DD15 it will pull down to 900 rpm. People could 1000 rpm and 1400 rpm. That not much difference then 1200 rpm and 1600 rpm. Learning each gear range is good also.

 

You pick up any gear except lo range in a 12.7 at 1,200 is a recipe for disaster! Nothing wrong with winding them up and everything wrong with lugging them.