This is something I always wondered about ... Would it be possible to somehow energize the ACR solenoids if you roll the throttle past "off" ... like the same way you kill the cruise or able/disable the EITMS while the bike is in motion? Reason being to turn the ACRs into a jake brake. Not sure how effective it would be since the valve is nowhere near the size of an intake or exhaust valve ... also not sure how long they would hold up to use like that. Do the ACRs open on the compression stroke only then close? ... or do they just stay open no matter what cycle the piston is in til the engine fires? Idk. Surely someone in here is bright enough to figure out how to do this and come up with a plug/play kinda deal to make it all work because I would be 1st in line to buy it!

For those that are thinking ... "Why would anyone ever want to do this for?" ... Well, if you drove truck like some of us you would have your answer. I always use my engine and trans to do most of my slowing, same way I drive a truck. It would be cool to have a little more extra engine braking than I already have without using the brakes. I sort of already have the sound of a jake with my ProPipe, but I would love to have the real deal if possible. Just think ... riding along, slowing down, roll the throttle off and ... BWAAAAAAAAAAAAAAAAaaaaaaaaaa .... I would be in my glory, lol. What do you guys think about this?

 

Interesting... I'm just trying to wrap my head around your idea. Would opening the acr slow the bike, or cause the engine to turn easier, and take away the braking effect?

 

You are correct, it would not slow you at all, a compression release is to help high compression engines spin faster to help start.

The Jacobs Exhaust BrakeÂŽ uses exhaust back pressure to dramatically increase your braking power by restricting the flow of exhaust gases and increasing back pressure inside the engine.

Benefits

Improved downhill vehicle control
A must for towing provides “peace of mind”
Helps brakes last three times longer, paying for itself
Designed, engineered and tested to OEM specifications
Jacobs, maker of the Jake BrakeÂŽ brand engine brake, provides more than 50 years of braking experience.
How It Works
The increased backpressure in the engine creates resistance against the pistons, slowing the crankshafts rotation and helping to control the vehicle speed. Overall, this requires less use on the service brakes, which means they last longer and reduce overall costs.

 

A real jake works by altering valve timing controlled by solenoids which bleeds off pressure on the compression stroke and blows it out the exhaust. No compression = no power to push the piston back down like it usually does on the power stroke. All that noise you hear when a jake is in operation is all that air that is normally compressed in the cylinder being pushed out of the exhaust instead of igniting which then turns your engine into a brake rather than firing and making power. So it basically works like an acr. The difference and question is HOW does in work in our bikes though? Your engine also slows from high engine vacuum too and if the acr doesn't close on the intake stroke you would lose that.

Not only does a real jake sound amazing, what is actually does is even more amazing if you haven't experienced one. With a strong running truck and a good jake it will actually bring your back off the back of the seat if you aren't expecting it. It won't slow you fast like your brakes, but it will bring the truck almost to a complete stop just by dropping gears. I would LOVE to be able to have that on my bike.

 

Think a jake brake would more likely lock up the rear wheel. Can't see how it would slow you down(on a motorcycle) better then a downshift.

 

I have often asked myself why would anyone want to subject a motor to excess wear, compared to the cost of brake pads, or shoes and rotors?
For me, I would rather replace pads and rotors vs do that to my engine.....
my opinion, yours obviously varies

 

I seem to remember (long time ago) either Husky or Hodaka dirt bikes had something of the sort, I think they had an extra little lever and sounded a lot different when they used it.

 

That was to lower compression when kick starting the bike. They do it automatically now.

 

No Barry ... not to argue, but you're thinking of how an actual exhaust brake works, not a real jake. Some guys with lighter diesel pick-ups have exhaust brakes. A real jake (short for Jacob's Engine Brake) works how I explained. Here you go to clear-up any confusion ...
Here's an older vid below that explains the whole process much better ... also tells you HOW it retards the engine for those that thought it would just make it spin easier. Obviously a diesel has WAY more compression than our gas engines which is why the solenoids also have hydraulic pressure to open the valve ... otherwise it wouldn't have the power to do so. I don't know how strong the acr solenoids are and keep in mind they are smaller than the exhaust valve so ... this creates more problems/questions. The starter spins your engine over slower than idle speed so they easily withstand that pressure, BUT could they withstand opening at say 5000 rpm without the aid of hydraulic pressure? I was thinking maybe yes if you timed it to open at the start of the compression stroke rather than right at the end where you have all the combustion pressure trying to force it closed. That raises another ? ... Can the solenoids operate FAST enough to energize/de-energize at higher engine speeds? idk. Would it even have enough power to do anything since the valve is much smaller than the exhaust valve? again ... idk, but I would have to think it would help because it would still be bleeding off compression.

For who said it might lock up the back wheel ... because of the size of the actual acr valve and the lower compression in our engines I say no, BUT you would also have to use some common sense of when/how to use it properly just like you do in a truck. Here's another way to help with that ... have a low/high switch that controls either one or BOTH acrs.

Right here are two more benefits of having one on your bike ... safety ... and here's the one we all would love ... EXTRA COOLING! ... No fire / compression = no HEAT! It would need to work similar to EITMS as in turning off the fuel/spark ... and you thought decel pop was bad? ... you certainly wouldn't want all that raw fuel igniting in your pipe when you get back on the power! So lets say you leave that congested ralley in town, bike is HOT, get up to speed and proceed down a long hill a mile or so ... instead of dropping a gear/riding the brakes lightly, just drop a gear and roll off the throttle without riding your brakes, listen to that air pump thumping away while also cooling your engine and brakes as you slow down or hold your speed.

 

Some of the older Honda XR 250s had them too. I knew a kid back in my younger days that had one and would pull the lever and it sounded really cool when he was slowing down.