Author Topic: computerized rev limiter fuel shut off? I got a plan. (Read 3434 times)

voodoo · « **on:** August 27, 2006, 07:48:33 pm »

megasquirt hooked to a distributor or some kind of tach input, and when the motor reaches 4000 rpm or your choice of rpm, it turns off the fuel solenoid limiting rpm, fuel turns back on when rpms go below redline.

plan is to take the governor out of the pump.

RabbitJockey · « **Reply #1 on:** August 27, 2006, 08:01:27 pm »

i dunno about need megasquirt, but i had actually thought of this as well, i think it would be a fairly simple circuit to create that would shut off fuel at a certain frequence output of the w terminal, this owuld of course the frequence of w/e rpm you want to cut fuel, say 5k exactly, this way could disable your governor as much as you want and have no power loss until you hit the brick wall of the governor, rather than the slow decline in power and then the sudden cutt off that the motor has from the factory.... yeah i thought about this before, i dunno why i didn't post anything haha.

QuickTD · « **Reply #2 on:** August 27, 2006, 08:05:31 pm »

The fuel solenoid will not re-open if it is shut off at high RPM. The suction from the head and the housing pressure hold the plunger against the seat and the solenoid won't pull it back up until the engine speed falls, it'll sometimes pull back in before the engine stalls, sometimes not.

You can't completely eliminate the governor either, you need to keep the flyweights and at least the idle and starting springs. The governor balances injected quantity against engine load at idle. It adjusts injected quantity as the engine warms up or the accessory load changes. Without it the engine will either rev to destruction or slow to a stall, it'll never reach equilibrium. The starting spring is needed to pull the governor linkage to the starting quantity position (which is higher than than full "throttle" position) when the engine is at cranking speed, the flyweights compress the spring fully as soon as engine rpm starts to rise to idle speed.

jtanguay · « **Reply #3 on:** August 28, 2006, 07:21:47 am »

Just seems like this Bosch pump is already perfect in every way! I personally think that if you starve the pump at high rpm, you're going to do some serious damage to the internals

better find a way to do it AND keep the diesel fuel lubricating it :wink:

I think you should start looking more towards having an electric governor. The flyweights are what limit fuel right? Why not have them magnetically actuated when you reach the rpm that you desire? We're talking some SERIOUS engineering here, but it could be done. They would basically stay inward until you reached the rpm you want, then spring out when you reach your 'wall'. One thing to consider as well, is what kind of damage, if any, might be done to your motor from having a huge surge like this. (engine mounts... etc...)

zagarus · « **Reply #4 on:** August 28, 2006, 07:51:29 am »

can't you just increase the tension of the governor spring (or whatever part it is, im still dum with this) and just make it so the fuel cutoff isn't at 4200 or where ever it is, but say 5500? That way you won't worry about over reving but at the same time you will have more power longer. i thought that would be the smartest way. dubcanuck mentioned it.

QuickTD · « **Reply #5 on:** August 28, 2006, 08:20:28 am »

Replacing the main and intermediate governor spring with a longer spring (more coils) with a slightly higher initial tension than the existing main spring would give the sharp cutoff that everyone seeks. Possibly even removing the whole spring capsule and replacing it with an extension spring of the proper rate would work better (more coils and a more constant rate). If you take a look at the video's of VE governor operation that were posted a couple of weeks ago you can see the effect of a long, fairly constant rate spring on governor operation.

The only drawback to this method is that testing is very time consuming, any changes to the spring require pump top removal...