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Old 06-10-2016, 12:55 PM   #71
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Originally Posted by Cowracer View Post
Any engine is basically an air pump. If you block off the exhaust (which is what an exhaust brake does) the engine turns into an air compressor. Air can get in, it cannot get out, and it takes energy to compress air. Any engine will function like that with the exhaust blocked (or partially blocked) off.

A Jacobs "jake" brake opens the exhaust valve at the time the injector or spark plug would normally fire. Energy is used up in the compression of the air in the cylinder. Its basically the same function as an exhaust brake, but the action occurs at a different place in the engine.

With all that being said, exhaust brakes (of any kind) are most effective on diesel engines because they do not have throttles. They gulp in the same amount of air no matter how far you press the accelerator. Gassers usually have the throttle closed for deceleration, largely limiting the amount of air that can be compressed to aid deceleration.

What some new computer controlled gassers with throttle by wire are doing is killing the ignition spark and fuel injection pulse, and opening the throttle WFO while in "exhaust brake" mode. In that case, they can be just as effective as one on a diesel.

Fully aware of how exhaust brakes work, they just don't put them on gas engines due to the fact that the compression is too low to be effective. Been a gearhead all my life.

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Old 06-10-2016, 09:42 PM   #72
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On racing motorcycles years back it was called a compression release. Jacobs had a law suit against towns that had posted signs that said do not use/engauge jake brakes in town because they were not all Jake brake by design.

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Old 06-10-2016, 09:54 PM   #73
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Originally Posted by Time-Travelers View Post
We don't have that weight yet, still 'making it ours'. Should be close to 'fully' equipped and weighed by the end of the month. Dry weight of our 8289WS is 8125 with a CC 1208.
Flat towing no problem when i did it with F 150 but over weight from day 1! Trailer brakes ran pretty high to slow it.

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