Scottie-GNZ Posted June 19, 2001 Share Posted June 19, 2001 What would be considered a good voltage reading for the system under WOT racing conditions? My voltage at idles varies from 13.6 to 14.2, but lately under a full racing load, I am getting readings of 12.3 to 12.9. My concerns are whether or not I have enough voltage for the fuel pump to run at the max required capacity, for the injectors running at a high duty cycle and for the coil packs. Is this normal voltage for the conditions and why is there such a drop considering the car has no accessories to drain voltage? It has ben suggested that I get a volt booster or an adjustable regulator that will give me 14.8 - 15.0 at ide and around 13.6 under race load. Any comments on this? What are the other folks out there racing seeing? Quote Link to comment Share on other sites More sharing options...
pparaska Posted June 19, 2001 Share Posted June 19, 2001 Scottie, I'm no expert but my feeling is that you shouldn't be seeing 12.3 volts with the motor turning more than an idle. How big is the wire from the Alternator to the battery and the rest of the loads? I like to use 8AWG for that, but 10AWG might be enough if the distance isn't too long. What's the voltage at the Alternator output at higher rpm? How big is your wiring to the pump? Is the ground side dropping voltage? Electric fuel pumps are pretty sensitive to voltage drops - You may be losing fuel pressure/volume if it gets that low and you've calibrated everything at 14.2 volts. Quote Link to comment Share on other sites More sharing options...
MYRON Posted June 20, 2001 Share Posted June 20, 2001 Scottie, is the belt slipping at high rpms causing voltage loss? I was under the impression that 14.2 is the normal charging voltage at cruizing rpm. I did notice changes in the SOUND of my fuel pump when my electric fan would kick on, but I never noticed power loss due to lack of fuel pressure. Myron Quote Link to comment Share on other sites More sharing options...
BLKMGK Posted June 20, 2001 Share Posted June 20, 2001 That's too low Scottie! If that is indeed the voltage that your pump is seeing I believe you are losing some volume. The pressure may not drop as the regulator kicks in but it could also be effecting your spark. How old is the alternator? Belt slippage actually sounds like a real possibility too. Underdrive pulleys or stock type Buick setup? Quote Link to comment Share on other sites More sharing options...
Kevin Shasteen Posted June 20, 2001 Share Posted June 20, 2001 Scottie, Have you tested voltage w/out the datalogger? Or are the readings the same? 14.2 seems to be a decent average-my Z's gauge reads close to 16...all the time; since there are no increments on the stock Z gague from 12 thru 16volts...I assume I'm pushing or pegging 15volts. In Christopher Jacob's book "Performance Ignitions" he has suggestions for wiring your ignition is such a manner that your ignition circuit sees maximum voltage at Wide Open Throttle; once you've let up on the gas pedal-your charging system drops back down to normal. He goes on to say that most dragsters dont see WOT for more than 8 to 20 seconds at a time; and that your components wont burn up or burn out within that time/after you let up-the system cools off & everything is fine. He claims you can get up to 1000rpms from the extra voltage boost. He says that Off Road racers have used the 12volt to 24volt system under Wide Open Throttle for years. Most drivers are usually at partial throttle; very little time is actually spent at WOT. Jacob's Electronics sells a few different relays for redirecting the voltage or can instruct how to run two batteries w/the relays for a full 24volt charge under full WOT only; (Hmmm?). That extra juice might be just enough to get you into the 9's or 10's/which ever it is you're closing in on(?). Something to think about? Kevin, (Yea,Still an Inliner) [ June 20, 2001: Message edited by: Kevin Shasteen ] Quote Link to comment Share on other sites More sharing options...
Scottie-GNZ Posted June 20, 2001 Author Share Posted June 20, 2001 Pete, the alternator to battery wire is 10AWG and no longer than 6'. The fuel pump + is 10AWG directly off the alternator running through a relay mounted in the passenger side toolbox. The relay is triggered by the original fuel pump hot-wire. The fuel pump ground is also 10AWG running directly to the battery. I would consider hi-13 to low 14s good at idle but how do I determine where I am losing it under racing load? Like you said, my main concern is having proper voltage at the pump. Quote Link to comment Share on other sites More sharing options...
pparaska Posted June 20, 2001 Share Posted June 20, 2001 Sounds alot like my setup for the fuel pump wiring. Glad to see someone else pays attention to adequate grounding! Are you sure the FP is actually seeing this same voltage as the volt gage? I don't know where the volt gage is wired in youur car (or is it the datalogger?) Anyway, can you get the datalogger to measure voltage at different locations? Across the battery, at the FP relay, at the FP itself? Or use the voltmeter and peek at it with it at different points in the electrical system to hunt down the drop. Also you could put it from the battery + to the FP + and measure any drop, etc. Not sure I'm any help here... Quote Link to comment Share on other sites More sharing options...
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