ONE way to do calculations is to understand that E85 will require about 49% more fuel to achieve the same Lambda. You can’t use A/F when you calculate percentage fuel differences because the FUEL part is in the denominator (AIR is in the numerator). Switch it over to F/A by taking the inverse (1/x). That’s how the fueling is specified in the actual PCM strategy anyway. Diablosport tries to make it easier for CMR tuners by using A/F but they have to switch it back to F/A behind the scenes.

Here’s an example for ya…

As you can see, DOUBLING the fuel (2-parts instead of 1-part) results in an A/F of 7.35.
14.7 parts AIR with 1.49 parts FUEL gives you a ratio of 9.86 which is E85′s Stoichiometric ratio.

If you switch to F/A, it becomes easier to calculate %-differences in fuel..

Gasoline Stoich F/A: 0.0680

E85 Stoich F/A: 0.1015

Then, just do 0.1015/0.0680 and you get 1.49 = 149% = 49% MORE.

Close Injector - EV1 Dimensions

Close Injector - EV1 Dimensions

Close Injector - EV1 Dimensions

The Car Club Challenge Association offers an opportunity for any group of people to join together and create a team that can drag race competitively. It’s an alternative to dangerous street racing. It also is an outlet for the people who want to race their cars and learn about the sport of drag racing. It’s a competitive series that caters to beginners as well as the experienced racer who wants to learn more about how fun and exciting drag racing can be!

• Generally, with the base 7psi Mustang kit, you’ll see 6psi for most of the RPM range and near redline it’ll creep up to 7.
• The published boost levels were recorded at sea level in Anaheim, CA. If I remember correctly, you’ll lose about 0.5 psi for every 1000 ft elevation.
• All lot of the time, aftermarket automotive boost gauges are not calibrated accurately. Get a GOOD pressure gauge from SnapOn, Craftsman, etc. One that goes up to 20psi or 50psi or something (you can’t acurately read low pressure levels on the ones that go up to 150-200psi). Hook both gauges up to a single air line with a regulator and make sure both gauges are reading the same. Depending on the boost gauge/sensor, some you have to calibrate.
• Make sure your SC belt is fairly tight
• Every once in a while, there’s a problem that people run into with the by-pass valve operation. When the by-pass butterfly shaft slips in the linkage, the boost levels will substantially drop. Here’s a link to a post about checking the bypass valve for proper operation
• As for the boost reference location, it shouldn’t make TOO much of a difference where you hook it up. I think the line that goes to the fuel pressure sensor is hooked up to a single runner. This usually causes some fast pressure fluctuation caused by the intake valves opening and closing. For PCM use, filters are applied to the voltage which smooth it out. For a mechanical pressure gauge, you MAY see smoother values hooking up to the bypass vac/boost line because it’s derived from the intercooler housing which is common for all runners. Additionally, you may see SLIGHTLY higher boost values from the bypass valve’s pressure reference port because it is hot air. There’s a slight pressure drop after the air cools from the intercoolers. Below is a diagram I made. I think the bypass pressure reference port is actually where we measured the pressure back at Techco but don’t quote me on that because I’m not 100%.

If anyone has a video of their RMA Performance tuned car that they’d like me to put up on the channel, let me know!

Using the stock Chrysler fuel returnless system, the pressure in the fuel lines is maintained at 58-60psi. However, fuel line pressure actually means nothing for the PCM fuel calculations. What really matters is called Delta Pressure. Delta Pressure = Fuel Rail Pressure + Manifold Vacuum. During idle, there is a lot of vacuum in the manifold which helps pull the fuel through the injectors. Let’s say your base fuel pressure is 58psi. If you have 20 inHg vacuum in your manifold (~10psi), it’s actually like your fuel pressure is 68psi! 68psi is your Delta Pressure.

Anyways, my point. When you’re working with a vehicle that has boost, the opposite happens to your Delta Pressure; it goes DOWN. With a Techco base kit, you only have ~6psi boost so you can get away with the lowered Delta Pressure… barely. When you’re 10+ psi (higher boost), you REALLY start to lower your Delta Pressure which really kills the amount of fuel you can get through the injectors. Example: Let’s say you’re using the stock Chrysler fuel system with 14 psi boost. Your RAIL pressure may be a constant 58psi (which you can see on your fuel pressure gauge) but your delta pressure is only 44psi! Normally, the G302 injectors flow ~60 lb/hr @ 58psi Fuel Pressure. When you introduce 14psi boost, those same G302 injectors only flow ~51 lb/hr @ 58psi Fuel Pressure.

What a MAP-referenced FPR does is instantaneously adjust the Rail Fuel Pressure by the same amount of vacuum or boost in the manifold. The stock Chrysler system is “Constant Rail Pressure.” With a MAP-referenced FPR, it’s a “Constant Delta Pressure” system (the rail pressure fluctuates to maintain a constant delta pressure instead of the other way around. It’s almost a requirement for any higher boosting engines.

Another reason why I usually switch almost all higher boost customers over is because I come from a more formal calibration background where all the calibration data is accurate and correct instead of falsely specifying calibration data to make the car act like you want.

Lastly, DiabloSport does not have complete control over something called “Fuel Correction vs MAP” so instead of calibrating data correctly in the boosted region, either the VE table or injector transfer functions have to be falsely set in order to maintain the correct A/F ratio. When you switch the car to a Constant Delta Pressure system, there is no need for the “Fuel Correction vs MAP” table so this table is set completely to 1.0 and all the correct calibration data can be set in both fuel injector and VE calibration.

An example MAP-Referenced Adjustable Fuel Pressure Regulator can be found here:Aeromotive A1000 Injected Bypass Regulator (opens in new window)

Related Post…
Example Fuel System Setup for High Horsepower Hemi engines (opens in new window)

Check supercharger bypass valve for correct operation. You’ll need to remove the front intercooler cover (part that says TECHCO) and then remove the intercooler cores. You’ll see the bypass valve blade in there. Now turn the bypass valve from the outside of the housing by pushing forward or pulling back the bypass valve linkage. When the linkage is all the way toward the front of the car, the bypass valve blade should be open. When the linkage is all the way toward the back of the car, the bypass valve blade should be completely closed. If the valve blade doesn’t operate EXACTLY like I said, the bypass valve linkage slipped on the bypass valve blade shaft. Readjust and retighten set screw (it needs to be fairly tight so it doesn’t slip again).