350SS

iTrader: (38)

I'm trying to switch to E85 and initially was severly maxing out my injectors (83 lb/hr going to 143% dc at 6000rpm). I picked up a set of FMS 1600cc injectors knowing they would be overkill but trying to make them work. I've been able to get them down to pulsewidth of 1.4ms at idle with afr at 8.31 (stoich for e85 is 9.78) or lambda = 0.85. This is with base fuel pressure of 45psi. Any lower pulsewidth and the engine stumbles...maybe they're not eving moving fuel past that point.

My question is how much can I lower the fuel pressure on these injectors and still have decent spray pattern, fuel atomisation, etc...

Is 25psi base pressure too low?

RAACCR

If you're at 45# now, you'd need to get down around 32# of fuel pressure to make up the difference to get to stoich. Are you at 45# without vacuum reference? If so, changing to vacuum reference ought to pull the pressure down and get you pretty close to where you need to be.

BTW, I've run disc injectors down into the mid to low 20's for emissions testing, and they ran okay. Pintle style probably would be even cleaner at low pressures. The injector works on a pressure differential between the rail and the tip, so when you are under vacuum at the tip (in the manifold), the injector thinks the pressure is really higher that what you've got in the rail.

FICINJECTORS

iTrader: (30)

the 1600cc Bosch is a pintle type injector, not a disc. They were designed for the CMG market, (natural Gas powered engines) These work very well at 32psi input pressure due to the pintle design. I did a video a while back showing these running at 32. As stated by the post a few up you can also run them lower.. The spray pattern etc was very satisfactory. What driver are you using? I will try to find the video, if I can I will post it for you.

350SS

iTrader: (38)

I'm running a regulator with vacuum/boost reference so at idle (at 40kpa or 17.7 in Hg vacuum) the pressure drops down to 38 or so but of course the differential is still 45 psi. It sounds like I can drop the pressure then and be okay...hopefully that will clean things up. I'm running an acceleronics versafueler and have made a few changes to the injector parameters using EFILive.

Thanks for the help guys.

seanmathes

Can someone explain to me what is the purpose of lowering the fuel pressure? I will also be running 160s soon with a versafueler. I am running the stock ECU and tuning done on SCT advantage 3.

Frost

iTrader: (45)

It's purpose is gaining the ability to idle without drowning the engine.

seanmathes

Are there any negative impacts to doing this? Is this because the injectors are pushing less fuel at the same pulse width at a lower pressure?

Frost

iTrader: (45)

lowering base pressure will lower pressure EVERYWHERE, which in turn lowers the overall flow of fuel into the engine.

You second sentence/question, your assumption is correct

seanmathes

Wanted to ask this again, but is there any reason you wouldn't want to run a lower base pressure?

350SS

iTrader: (38)

As stated above, lowering the fuel pressure decreases the flow rate across the vacuum/boost/rpm range. Depending on your setup, lowering the fuel pressure may result in the injector not being large enough to flow enough fuel on the top end.

In addition, there is a point to which lowering the fuel pressure will effect fuel spray pattern and decrease fuel atomization. This depends on the pressure and the type of injector.