fuel split on blower/ports

As much as you can through the blower without making the port jet size too small as to catch dirt. It is hard to get much above a 65%/35% split most likly get a 62/38.

 

I will not go into the 30's. Either way you need a fuel strainer screen on the inlet to the BV or an inline fuel filter. Remeber if you reduce the area the pressure goes up so the flow needs to be adjusted a little. Jetsize software does an excellent job of letting reduce or increase all the jet area by a percentage and keeps the total GPM to the motor constant.

 

Mightymouse. You need to correct Jetsize to match your car. Davenport talks about this in his instructions but it is not very clear. Here are my own guidelines. This includes adjusting GPM if you have a flow sensor so if you don't then just do the part on adjusting fuel pressure. Make sure you save a copy of that Jetsize setup you have now so you can return to it if you make a mistake.

As I have said before the Jetsize program assumes that you are reading the fuel pressure prior to the BV because Jetsize automatically drops the fuel pressure in its calculations to account for the drop through the BV. Davenport took and average drop across the BV from numerous tests on his flow bench. He just forgot to tell us.

For those who don't know. In Jetsize you can reference everything to 8000 rpm or 9000 rpm depending on how you operate your motor. With a TA/FC there is really no point in using 8000 rpm as a reference because you may never see 8000 again after launch. Same goes for if you shift at 8500 rpm there is no way you can use 9000 rpm as a reference. Make sure if you talk to a tuner or racer that you are both talking the same reference and at the same Density Altitude. I always talk fuel flow at zero feet in Density Altitude. So I change my weather in Jetsize to read zero feet and see what the GPM is. (29.92, 0%, 59*)

Double check after doing this that you have the same Tuning Modifier and same Main Jet size. If so the tuneup didn't change.

Just for info...adjusting just the GPM in Jetsize does NOT change the tuneup because it is just a reference for you.

Calibrating Jetsize To Actual Car Data


1. You need to write down all the data from the run as recorded on the data logger. You will need at 9000 rpm (or 8000 RPM) the boost, pump pressure and GPM. The best and most stable place to read this is during the third gear pull when things are not changing fast. For initial rough calibration on an uncompleted run you can use any 9000 rpm point (or 8000 rpm). The second gear 9000 rpm (or 8000 rpm) point is better than a first gear point. Normally first gear pump pressures and GPM are influenced by lean outs or enrichment circuits and should not be used.


2. Now open Jetsize program and have it set up for the run just completed. Write down what the Tuning Modifier, the main jet size, the pump pressure and the GPM are.

3. Go to the second page of Jetsize and set the boost to be what was recorded at 9000 RPM (or 8000 rpm)

Adjusting Fuel Pressure

4. If the pump pressure on the first page was off to what was actually seen then change the pump pressure on the second page. Go back to the first page and re-insert the Tuning Modifier that you had previously recorded (changing pump pressure changes the Tuning Modifier). You will probably have to go and insert the pump pressure on the second page again because it normally takes more than once to rock it in. It may take three or four times. Don’t forget to correct the Tuning Modifier everytime.

Now if you have a Fuel Flow Sensor

5. Once the pump pressure is right on go to “Adjust” in the lower left quadrant of the first page and adjust the GPM to read what was on the data logger at 9000 RPM (or 8000 rpm) during the run. (this does not change your tuneup)

6. Now check everything…… the boost pressure, the Tuning Modifier, the pump pressure and the GPM. It should all match what you had on the previous run.

It is now calibrated to your car.

 

Get Jetsize out and calibrate it for your motor. Add a 40 jet Pump Sizer Loop through a 30 lb poppet crack pressure and see what happens to your main jet size. You may need a 60 or 80 Pump Sizer jet. The GPM to the motor at this point will not change but the main jet size will. So every run adjust the Tuning Modifier by adding +18 to it. So if you are at -118 then make it -100. If you are at +30 it will make it +48. This should change your main jet size by 5 sizes which is about a .25 GPM change to flow at a time. You may have to re-adjust your Pump Sizer Loop jet to keep the main jet size where you want it. Keep doing this and watch your EGTs at the finish line. You will see them getting hotter. Keep reading those plugs. They should start going from the green bubble burn off to medium to dark gray maybe on half the flat base ring then it will start going dark gray on the whole base ring. Like you said I believe I would keep the timing where you are at now.