BCM Community
Bus Discussion => Bus Topics ( click here for quick start! ) => Topic started by: Iceni John on June 28, 2023, 09:06:43 PM
-
A Detroit mechanic that I know told me that Jake brakes should not be used at high RPMs. Has anyone here heard why they shouldn't be used that way? Jakes have more holding ability at higher RPMs, and when descending long grades I'm in 3rd or even 2nd gear at almost 2000 RPM.
Just curious.
Thanks, John
-
Jakes don't damage a 2 stroke at high rpm,the 4 strokes you never flip the jakes on at 2000 rpm,My ISX Cummins the Jakes come on in stages to prevent the engine from never turning over 2100 rpm.The early series 60 and M11 Cummins would throw rods if you turned the Jakes on at 2000 rpm.You still need to watch the rpm on your 2 stroke the Jakes will increase the rpm if not careful in some cases,the oil consumption will increase with constant use of Jakes on a 2 stroke too,you are fine at 2000 rpm at 2500 it is a different story and picture
-
Thank you for that explanation. I won't argue with him about this, but I'll keep using my Jakes as always!
John
-
I try to drive at 60 to 62 or so. I use my Jake on long downhills and to slow getting off the highway. I keep an eye on the tac downhill and break a little if I need to, but I fear blowing a front tire at over 60 or so. That in itself would be a bit of a rodeo getting to the shoulder. I have heard multiple times it eats oil when you use the jake. I can buy a lot of oil for one tire. I don't overspeed it but feel like you John. If I can't use it, why have it?
-
The jakes apply resistance to the rear drive wheels so in the event of a front tire blowout, the bus will tend to stay straighter and more controllable, if that is any help.
-
I drive with the Jakes on all the time. That is what they are for. Just don't over-rev the engine.
-
Way. way back before the dawn of time, (or about 1970) my assigned 1963 Crown Supercoach school bus had a Cummings 743 220 engine with a Jake Brake. If memory serves, there were no limiting factors using the engine brake at very high rpm.
Very high rpm meaning more than the governed speed of 2100 rpm. Amazing tech ... the old girl would come down the ridge route North on Eye Five at 40-45 mph without touching the service brakes. The Jake was very noisy inside the bus.