TimZ Posted August 10, 2001 Share Posted August 10, 2001 This was kind of surprising... I have been running 50lb/hr injectors at a base pressure of about 58psi, and this has been working pretty well. At the last dyno session, we noticed that the fuel temperatures were running pretty high, and with the recent high ambient temperatures, the pump had started sounding rather strained. This worried me, and after some thought, I decided to try going to larger injectors, and running at a lower pressure. I picked up a set of 74lb/hr injectors today - they were exactly the same brand/line of injectors (Siemens/Deka) as my old ones, and it took me about 5 minutes to swap them out. I ran the fuel pressure all the way down to 38psi and fired it up. Amazingly, after retuning for the different injector charicteristics, the idle quality is much better now - it still has a stable idle at stoich and leaner - it wouldn't do that reliably before. And, it was still running much richer under boost than before - I had to lean it out considerably. I fully expected having to lean things out under boost - even derated to 38psi, these injectors flow about 11 lb/hr more than the old ones did (each) at 58psi. I was amazed at how well the car idled, though - apparently the lower pressure allows the injector to open and close more quickly - the dramatic increase in dynamic range is a very pleasant surprise. [ August 09, 2001: Message edited by: TimZ ] Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted August 10, 2001 Share Posted August 10, 2001 Tim, I am wondering about your injector setup, I have a set of siemens/deka injectors that are 55lbs. Are your injectors oringed on the intake and rail ends? I am trying to figure out how to drill out the pockets on the intake without bringing it to a machinist. Just got a blank piece of fuel rail ready to be drilled. Iam using a n-42 intake. thanks, Luckyod Quote Link to comment Share on other sites More sharing options...
TimZ Posted August 11, 2001 Author Share Posted August 11, 2001 Yep - those look like the same injectors, and I am also using an N42 manifold. I took a look at mine tonight, but did not pull the injectors. Basically, the holes for the injectors were drilled out to accept the o-rings of the Siemens injectors. I had a machinist do mine. You might be able to just drill it out, but the surfaces need to be very smooth so that the o-rings can seal properly. You would have to be very careful, and use LOTS of aluminum cutting fluid, and preferably a good drill press and a new, high quality bit. Same goes for drilling the fuel rail, BTW. The thing that I couldn't tell for sure without pulling the injectors was whether the mounting ears for the old injectors interfered - if so, then you'd probably have to use an end mill to cut the holes. In that case I'd just take it to a machinist. Also, the bolt holes for the old injectors were welded up, and the protrusions that they made into the manifold runners were ground smooth. Quote Link to comment Share on other sites More sharing options...
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