what makes Frybrid purge faster?

[großewagen]

Can someone please point me to an explanation of this. I can't seem to get my brain around it.

[Ryan DeWald]

I prolly should just wait for Chris on this but I think I can answer it. The reason is because the Frybrid does not use a looped return from the injector pump. The return line (carrying excess fuel not used at the injector) is sent directly back to the fuel tank.

In most designs, the return line is teed just in back of the fuel filter so any unused fuel stays in a circuit under the hood, cycling over and over with new fuel added to this circuit as some fuel is consumed.

With "most designs" when you switch to purge, diesel is added to this under-the-hood circuit to replace vegetable oil as it is consumed, but as the diesel replaces the VO, some of the diesel is consumed. So you have to let the engine run while the fuel in the circuit makes several passes as the diesel to VO ratio gradually changes to all diesel.

In the Frybrid design, there is no loop so once the switch is made back to diesel, there is a clear point in the line where diesel is now replacing VO. Ss that line passes into the IP and then out the return line and back into the VO tank, the purge is complete.

Did I get it right?

[cgoodwin]

"Purge faster" is kind of subjective as it depends on which plumbing layout you are using. If you have a system which loops everything then you have to burn the VO in the IP before it can be displaced with diesel, the Frybrid system is MUCH faster than this. If you have a system where the VO is looped and the diesel not, and you have a "Backflush" switch, then it may not be inherantly faster but is sure as hell is more accurate. With this type of system you switch back to diesel, then switch the backflush switch for "20 to 30 seconds"... When you switch back to diesel VO begins to return to the Diesel tank until you activate the "Backflush" switch, then you are routing the return to the VO feed line and "Backflushing" diesel through the VO filter and feed line (and heat exchanger if fitted), not a very good plan. The Frybrid controller is set to switch the feed to diesel but maintain the return to the VO tank just until diesel fuel reached the valve, then it diverts to the diesel tank. This prevents VO from getting into the diesel tank and limits the diesel in the VO system while preventing filling the filter and heat exchanger with diesel.


Chris