Technical > Spud Miller's Cave

high speed to lean

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skydvrbob:
I ran the car the other day and it worked great down low but leaned out and nosed over on top. Is there a simple way to keep it lean coming out then richen it up on top. Hilborn stack with only an idle bypass. No high speed.

Paul New:
The easiest way is to not run the high-speed get a good tune up that makes the car run the quickest you can get it to run. If at that point you decide to run a high speed fatten it up a 10 spot then go make a pass with the high speed. I wouldn’t run a high speed without a flowed fuel system telling me what pressure to have it crack with a given main pill.

denverflatheader:
skydvrbob - if you have inline fuel filter, might first check to see if it’s completely clear, due to your leaning out on top end.  If filter is clear, next check your fuel tank, shutoff, all lines, connections, nozzles, etc. to verify they are all 100 percent clear and working proper.  If all okay, then what Paul wrote.  1st things 1st, send your pump to FIE and have it checked/flowed for $70.  If pump okay, next look at your metering valve.  If all okay, your engine might have issues.  Alan

JrFuel Hayden:
I always think of my high speed vslve as nothing but a fuel pressure regulator, if you set at 100 lbs to open, then that's your fuel pressure from then on especially if you have no jet in the high speed, like Don Enrquez and Gene Adams run. I used to have an adjustable valve and gauge hooked up to our compressor in the trailer to check pressure. Once I started running over 100# which exceded our compressor we now just check the RacePak and adjust the shims in the HS. BTW I have a .080 jet in the HS instead of opening to the return line, so my fuel pressure more follows the RPM curve.
The idea of low pressure injection is the tune-up is less affected by changing weather conditions. at one point Bob McKray/ Don Enrquez were running 49 lb fuel pressure which of course the valve opened at the hit and stayed around 49# for the whole run.
The high pressure idea is it help adomize the fuel better, but I change the pressure almost every run depending on weather changes.
Have Fun,
Jon 

gregm784:
With a blown car, we definately use our "high speed" differently.  I use mine as a launch enrichment.  When mine comes off the torque converter and starts to climb RPM, the lean out opens (tuned with spring pressure).  At the shift, it goes back on the converter for a second and the lean out is once again closed.  WHen it finds the opening pressure again, it sounds/feels like it shifts again.

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