Cut dv's

[josha37]

so... I have decided i am going to cut my dv's... anyone have any comments/concerns before i go ahead with this that i might need to know about?

[tomnik]

what do you want to cut?
What Bosch did was to grind a flat to the collar to adapt the delivery curve.
Not suitable DVs will cause post spray and thus high EGT.
Can't remember that someone is running such a modification except some tests with lots of smoke and crappy engine run.

Tom

[winmutt]

Yes poor idle quality, late injection, high EGT. There are several threads about doing this and everyone came to conclusion it was a "bad thing"/

[josha37]

so.. could you just advance the injection timing to compensate?

[winmutt]

No.

[josha37]

so your telling me they caused late injection w/ high egt's because fuel was still burning in the exhaust and you cant increase injection time a bit to make it.. less late? Im just picking brains here because i havent even pulled them to look at them yet.

[winmutt]

Late injection is due to extended duration not timing. Sorry I should have clarified that. You can do one of two things to provide more fuel. Increase volume or increase duration. In this case you are increasing duration, what you want to do is increase volume as timing is very critical.

[josha37]

ok it sounded like you was implying it delayed the start of injection. Thanks for clearing that up. ok so if you are to cut dv's, downstream (at the injector end) what is the restriction that is creating the extended injection?

[winmutt]

There is no restriction down stream. The injectors are quite large enough. You can tweak the pump to give more fuel with stock elements, anything beyond that requires larger elements.

[babymog]

I'm not the learned one on this, but going from memory there was a lot of talk about the resonance in the injection line, 2nd-pulse injection from the pressure wave, other things that created fuel delivery after the normal end of delivery.

Shouldn't be too far down as this was discussed fairly thoroughly this past fall IIRC.

[josha37]

Ok that guys ill go back over those threads and see if i missed it. i remember seeing something about they cut dv's allowed more fuel to flow which held the injector open longer or something like that because the pressure did not fall fast enough in the line. Ill find it though. thanks

[winmutt]

Originally Posted by babymog

I'm not the learned one on this, but going from memory there was a lot of talk about the resonance in the injection line, 2nd-pulse injection from the pressure wave, other things that created fuel delivery after the normal end of delivery.

Shouldn't be too far down as this was discussed fairly thoroughly this past fall IIRC.

Thats basically what the delivery valve does is prevent 2nd and even more pulse injections. It really is not the place to focus. None of the 300+hp out there have even touched the DV's.

[josha37]

Not to sound like a dick but.. just because the "300 horse" guys arent doing it does not mean it is not worth looking at. example.. when i built my 383 i didnt change my valves just ported the heads, that was the route i chose does that mean that everyone that builds a 350 chevy needs to stroke it and port the head and the valves arent worth looking at? no... im just cheap and did not want to shell out more money for valves.

[winmutt]

Originally Posted by josha37

Not to sound like a dick but.. just because the "300 horse" guys arent doing it does not mean it is not worth looking at. example.. when i built my 383 i didnt change my valves just ported the heads, that was the route i chose does that mean that everyone that builds a 350 chevy needs to stroke it and port the head and the valves arent worth looking at? no... im just cheap and did not want to shell out more money for valves.

Delivery valves are not the answer. Adjust the torque, max speed, max fuel, remove the rack limiter and there is your cheap answer. If you want to take a risk, adjust all the deliver holders. This last one gave me the biggest power increase out of all of these. Not a smooth idle but I would easily guess that I have the most HP out there on a 617 without adding or subtracting anything to the system other an intake.

[josha37]

Deliver holders? torque- check, max speed- check, max fuel- check, rack limiter - check turbo.. check! . Lots of people claimed phenominal gains with dv's with a few... side effects. Ill claim the most power out of a 616 in my part of the usa until someone corrects me.