I wanted to see if the accel DFI VIC (variable injector controller) would work with my 93 computer, so I installed it and some 55# siemens low impedence injectors on my motor right now (running NA) and drove it around a little. I have a mildly rebuilt 355 with forged pistons and a small blower cam and mildly ported heads.

I put the injector constant as 55# on the chip and when I first started it up it ran super rich.. I dropped the fuel pressure at idle from around 45psi to about 36 psi but still the computer was pulling the max fuel it could and it was still rich. The injector d/c's were only 1.9-2.2 at idle (about 850 rpm).

With the supercharger on the car it shouldn't need that much more fuel at idle than N/A.. so I was wondering if anyone else had problems with bigger injectors at idle/low load and if they just learned to live with it being rich or if they did something to help fix the problem? Should low impedence injectors be 'ok' at a duty cycle that low (~2%?)?

 

I'm running 84's with no rich idle. I'd say anything over 84 would idle rich, though, because my idle pulsewidth is ~1.2 ms and I think the computer won't go below 1 ms.

Mike

 

Low impedance injectors will respond to shorter pulsewidths than high impedance. I am currently running 92lb low impedance injectors and have no idle issues on my 383 with a 925rpm idle. A friend has a blown small block Ford (331ci) running 160lb injectors and his idles fine at 1,200rpm. It won't idle well slower though. I can't say if this is the cam or the injectors though as we never really cared much that it idles so high (it's a race car).

Rich Krause

 

Thanks.. I am going to try to get these 55# ones to work then. I think the issue may not have been the injectors.