Lift pumps and EFI surge tanks

[milner351]

Bill - I would imagine that even with the radials - you're accelerating fast enough to deform the tires through the run - I would think it would be very difficult to get matched speed from front / rear - and for either calculated vehicle speed from tire speed value to match something like GPS or trap speed.

Amazing what you guys are doing with vehicle electronics at this level.

[dieselgeek]

I'm going adjust the front to be the same as the back as I just eye-balled the gap rather set it with a guage. The back reads clean. I also need to adjust the diameter's as they should track the same and not diverge. Neither is correct according to the trap speed measured by the timing lights in any event.

I learned that the right way to measure the tire diameter & circumference is to put a piece of tape on the tire with a radius line drawn on it. Put another piece of tape on the ground and line it up with the radius mark. Then roll the tire 1, 2 or even 10 complete revolutions to where the line is again pointing directly downward. Measure the length between marks, the more revolutions you make the more accurate the measurement. Then use math to convert the circumference to a diameter, key that into your Speed and Gear sensor configs.

We did this with Lee's car on the salt, our timed exit speeds are within .2 mph of our front wheel speed indication. The rear wheel is slipping around 2% (in top gear) up until he lets off the throttle, then both speeds line up to the tenth. I never got the GPS working to compare, but I'll have it working on our next trip out. Apparently there isn't much tire growth on the LSR tires at speed.

[BKBridges]

The fuel pressure trace looks like classic flow vs. pressure droop in the regulator. With a return style regulator its not an undersize issue but a diaphragm vs. valve seat design issue...Which regualtor are you running? Is it manifold vacuum referenced?
BKB

[CDMBill]

Its an Aeromotive 13110. I do not have it vacuum referenced as that was not how they recomended installing it and tuning it for an N/A EFI set-up. Would you recommend that I configure it that way? BTW the rails are 5/8" ID Wilson Manifolds "D" shaped rails.

Supply and return lines are #10. V to rails is #8, as are the rails to regulator. The regulator is 5 years old as is the whole system except the brand new pump.

[CDMBill]

I learned that the right way to measure the tire diameter & circumference is to put a piece of tape on the tire with a radius line drawn on it. Put another piece of tape on the ground and line it up with the radius mark. Then roll the tire 1, 2 or even 10 complete revolutions to where the line is again pointing directly downward. Measure the length between marks, the more revolutions you make the more accurate the measurement. Then use math to convert the circumference to a diameter, key that into your Speed and Gear sensor configs.

We did this with Lee's car on the salt, our timed exit speeds are within .2 mph of our front wheel speed indication. The rear wheel is slipping around 2% (in top gear) up until he lets off the throttle, then both speeds line up to the tenth. I never got the GPS working to compare, but I'll have it working on our next trip out. Apparently there isn't much tire growth on the LSR tires at speed.

I would expect tire deformation changes. I did a little impromptu street testing and saw the difference that a spinning rear tire makes in the logs. Very easy to spot as is the initial motion which gives a clear sense as to long it is between when I hit the throttle/TPS and when the tire actually turns. Given there is little take up in the driveline I get a great indication of true stall speed at launch. And i'll try the rolling effective circumfrence process as that makes great sense to me. We had originally enetered a diameter number that was smaller for the rear 30" tall tire and the front 26" tire; I guess I was tired.

[BKBridges]

[QUOTE=CDMBill;673570]Its an Aeromotive 13110. I do not have it vacuum referenced as that was not how they recomended installing it and tuning it for an N/A EFI set-up. Would you recommend that I configure it that way? BTW the rails are 5/8" ID Wilson Manifolds "D" shaped rails.

Supply and return lines are #10. V to rails is #8, as are the rails to regulator. The regulator is 5 years old as is the whole system except the brand new pump.

Bill,
Not wanting to go against the mfgs requirements, but it might be an interesting test to see if the reg "keeps up" with the demand better when referenced to MAP. The droop cant be good for performance. The only other thing that could cause pressure droop is restricted inlet/restricted fuel delivery. IMO Id at least take the reg apart and check for debris and or wear and check to see the condition of the diaphragm (stiff etc.)
BKB

[CDMBill]

Good thinking BKB. I'm also checking into the stock tanks venting after talking to Aeromotive tech today. Its the original 3/8 line and may well be too small. I'll be kickin' my self if that's the issue.

Interestingly when I raised the vacuum referenced question with Bret at Aeromotive he said the tuning would be easier if it was vacuum referenced. I have a spare vaccuum line available so I think we'll try some tuning with the line connected to the regulator at Drag Week. As the engine pulls 6-7 inches at idle and 10-12 at cruise throttle settings it won't be a big deal, but I like the concept especially as we have bypassed the fuel pump controller and will likely leave it that way for Drag Week.

Neither, the instructions for their N/A 1000 HP EFI setup nor the regulator show connecting it for N/A only boost referenced. Thanks for the tip.

I'll do flow test when I'm back home to work on the car. Traveling now.