Well i give in, had a set of high impedence siemens 83s and changed to a set of low impedence accell 120s, i changede the injector size in the configuration screen. i cannot get this thing to run, very hard to start and when it does it is pisssed, back firing and really rich, i continue to pull fuel out of the ve but it does not help, i can lower the numbers almost all the way down and it doesnt change. Please help with some suggestions of things to look for.

 

Did you change the injector out put too low imp? Large injector are known to be terrible at idle without lots of fine tuning

 

The 120's seem to have a very short rise time, reduce the injector opening time to .4 and see how it responds then.. Chances are you have it around .8-1.0 ms right now.

-Chris

 

Yep, your correct injector offset now is .84 ill lower it and try again

 

Are you referring to the injector offset coefficients here? I understood this offset to be more of a correction for manifold design...I might be wrong, but if I am could you explain better what these offsets are for? I would really appreciate it.

For what it is worth mine is set to 1.0 ms right now with 120 lb/hr injectors.

 

Correct me if im wrong but i dont believe their is a swith for the gen 7 low/high imp injector

 

You are correct there isn't "switch" for it.

 

Straight from the DFI help file:

"Fuel Injector Offset Time (ECM Revision 4.0 and Higher Only)

The 'dead time' for a fuel injector. This is the amount of time that it takes the fuel injector to open just before fuel begins to flow from the injector. Use this table to help match your DFI Generation 7+ ECM's control strategy to the type of fuel injectors that you are using. Previous versions of the DFI Gen 7+ ECM used a value of 0.8 mS in this table.


Range: 0.4 - 2.0
Units: mS

"

If you get this wrong (larger than necessary) , you will end up with extra fuel every inject event and even with very small VE values, the car may have more fuel than it needs if you happen to be running a large set of injectors.

 

didn't know the terminology of the values that need changed for the larger injectors. I'm not experienced in Efi lingo or anything else about Efi. I'm learning as I read these things that will help me with my setup.

 

I see, I was thinking it was under the "fuel" drop down. I see it in the configuration screen now. Thanks for clarifying, I was mixed up.

 

Man I just dont get it, put the 120s back in and fired it up, sucker is poppin spitting, sputtering and just runs like crap. For some strange reason i have to force the timing to 50 deg to get it to clean up, but it will run perfect with the 83s and the original tune. gonna reset the dual sync and try again, just dont get why it will run great with the 83s but with the 120s i have to force it to 50+ degs to get it to run with out popping and banging. Something strange is going on, ive run and tuned this system on lots of different set-ups over the years and never had any problems like this

 

ok well reset the dist and found some confusing instructions on accell site, on the instruction for the dis 8 box it says to set the ignition type to custum and have the crank trigger edge set to rising, but in the gen 7 instuctions it says just select the dual sync dist which puts the crank trigger edge to falling. What i have noticed is the timing is severley retarded at low engine speeds but if i get the rpm up above 4000 or so it will stabilize and match the timing light plus all the popping goes away, but when the rpms drop the timing becomes very erradic and retarded. I have the timing forced to 35deg and it is all over the place at start up and idle, whats strange is with the 83lbs high imp injectors this is not an issue evrything is great, but with the low imp 120s its fubard, how could a injector affect engine timing!