how does the injector return work?

[Don Tanklage]

i see that there is a line that comes from all the inj's and goes back to the tank



how does this circuit work?



thanks, don

 

[Don Tanklage]

maybe i should have asked how the injector itself works first... .



as for the return ciruit - i see mine has a fixed orfice in the banjo (just like the ve uses... . hummm). the orfice for ea inj is . 061"



that raises another question - the cross sectonal area of a . 061" hole is how big? i keep coming up with . 0029, is that correct? (sounds too small)



don



ps - has anyone figured out where i am goin with this?

 

[1stgen4evr]

Each injector function is pressure controlled by a spring (under an adjustable forcing screw) setting. The VE pushes (governor controlled quantity of) fuel to each injector in the correct timed sequence. When the fuel pressure exceeds the spring setting, fuel is allowed into the combustion area. (This the 'pop' pressure that is discussed) The pressure is such (3800 lbs) that as the fuel enters through the orifices, it atomizes and upon contact with the (compressed and high temperature air) it spontaneously ignites. There are no 'seals' as such in the injector. Therefore, some fuel is leaked by the working parts. Thus the required return line.



James

 

[Don Tanklage]

ahhh, thank you very very much



don

 

[sdstriper]

ps - has anyone figured out where i am goin with this?

No...



Your trying to increase the flow both in and out...

 

[Don Tanklage]

ps - if the orfice (for the return) was smaller, would less fuel be able to "leak" by the working parts?



would the smaller orfice create more pressure there (behind the orfice) and the pressure itself act like a seal (sort of) in the inj?



in other words do you think that more of the "gov controlled quantity of fuel" would make it into the chamber and less would be going back to the tank?

 

[1stgen4evr]

in other words do you think that more of the "gov controlled quantity of fuel" would make it into the chamber and less would be going back to the tank?





Take the line off somewhere and look at the very small amount of fuel returning. If you block (partially) the return, you will introduce a wild card in so far as controlled delivery as you will not have precisely the same function at each injector and could have one cylinder getting a disproportionate amount of fuel. (Which in fact is to some extent the case all the time as the injectors are minutely different. )



If you want more fuel, the pump settings will be the preferred place to 'crank it up'. It is relatively easy to get more fuel than can be economically burned into the combustion chamber. Also more rpms which give more power pulses in a given elapsed time.



PODs and a little tweaking on the pump will give you a nice "against the seat" acceleration. But as stated quite some time ago; chasing the HP goddess is a slipery slope that generally ends in a blown engine, transmission etc. Like all goddesses, she is for sale to the highest bidder. What's in your wallet.



James

 

[Don Tanklage]

in other words do you think that more of the "gov controlled quantity of fuel" would make it into the chamber and less would be going back to the tank?

hi james, and thanks - yes, that is what i was wondering...

Take the line off somewhere and look at the very small amount of fuel returning. If you block (partially) the return, you will introduce a wild card in so far as controlled delivery as you will not have precisely the same function at each injector and could have one cylinder getting a disproportionate amount of fuel. (Which in fact is to some extent the case all the time as the injectors are minutely different. )

what if one was to get or make a set of inj return banjo's that had a smaller orfice?



then the restriction would be the same for all the inj's, all the time...



would it still be a 'wild card'? (obviously this would be something that would have to be played with while on a dyno, but do you think there is possibly more power to made in this area? wouldnt it be best if one was able to get all of the fuel pumped from the ve into the cyl?)

If you want more fuel, the pump settings will be the preferred place to 'crank it up'. It is relatively easy to get more fuel than can be economically burned into the combustion chamber.

other than maxing out the afc (or removing the lever for it) and turning the fuel screw all the way in (or welding a point on the end of it if you can not get to a run away condition with the stock screw bottomed out) and installing a 14mm head, what other mods can one do to the pump to make it pump more fuel to the injectors????

Also more rpms which give more power pulses in a given elapsed time.

i understand that, and inj timing is another area where there is power to to made, but right now i am concentrating on the fuel volume end of it

PODs and a little tweaking on the pump will give you a nice "against the seat" acceleration. But as stated quite some time ago; chasing the HP goddess is a slipery slope that generally ends in a blown engine, transmission etc. Like all goddesses, she is for sale to the highest bidder. What's in your wallet.



James

the truck has pod's, screw all the way in, afc out, and is supplying WAY more fuel than the little h1c can deal with



i am just wondering if a guy was to spend 5k (or better) on twins and all the nice stuff that goes with them what else he could do to get more fuel to it once the pump was maxed



just thinking...



that is all



thanks again james



tank

 

[cerberusiam]

ps - if the orfice (for the return) was smaller, would less fuel be able to "leak" by the working parts?



would the smaller orfice create more pressure there (behind the orfice) and the pressure itself act like a seal (sort of) in the inj?



in other words do you think that more of the "gov controlled quantity of fuel" would make it into the chamber and less would be going back to the tank?

IIRC, when the injector "pops" the return is closed to the fuel so flow is maintained. When the injectors seats again then the return is opened to bleed the pressure off. I think a certain amount of fuel has to bypass for cooling and lube of the injector parts hence the return flow under partial pressure.



An easy way to increase the "gov controlled quantity of fuel" are the DV's.

 

[Don Tanklage]

do you mean 'porting and polishing' them?



replacing them?



(maybe with larger (higher flow) valves)?



is that what a 14mm head is?

 

[cerberusiam]

do you mean 'porting and polishing' them?



replacing them?



(maybe with larger (higher flow) valves)?



is that what a 14mm head is?

Replace them, hone them, or ?? To push more volume at the same pressure you have to open up the restriction points, but not to far or you have problems with the pulse wave in the fuel line.



The 14 mm head is a custom piston and head assembly that does thehigh pressure injection event. Stock is 12 mm I believe. The 14 will push more fuel but the results were less than stellar when they were pushed to the limit.

 

[sdstriper]

Are the industrial engine delivery valves larger or smaller diameter? Is there a check valve in there or what is in them?



Don the 14mm hyd. heads are custom made, very few exist. Several were fried during test and tune but there are still success stories among them and there are a few available now, I believe approx $500 each.

 

[cerberusiam]

Are the industrial engine delivery valves larger or smaller diameter? Is there a check valve in there or what is in them?

There are not many options available for the VE engines. A few different sizes. Yes, there is a check valve to stop the pressure wave from the injector closing hammering the high pressure piston.