Fuel Requirement Calculation Tip for E85

Dec 192010

I have a customer that’s switching over to E85 fuel and a lot of new calculations have to be done to make sure the fuel system is capable of handling the required extra fuel. Here’s one tip for calculating fuel requirements.

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…

 AIR FUEL RATIO 14.7 1 14.7 14.7 1.5 9.8 14.7 2 7.35

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.

Injector Body Style Comparison

Dec 162010

 I thought this might be helpful for people trying to figure out their fuel and injector systems. It’s visual and dimension differences between EV1, EV6, and EV14 injector types. EV6 and EV14 are very similar with the largest difference being the overall height of the injector. The EV6 type are considered “long” while the EV14 are considered “medium”. It also briefly shows the connector types as well which are Jetronic/Minitimer & USCAR. If you have any questions, let me know. Enjoy! Close Injector Body Style Comparison - EV1, EV6, & EV14

 Close Injector - EV1 Dimensions Close Injector - EV1 Dimensions Close Injector - EV1 Dimensions

Oct 122010

 A customer recently asked me about the level of boost he’s been seeing on his Techco supercharged mustang. Concerned about the numbers he was seeing, he was wondering if there’s a more accurate way to read it. He’s using an aftermarket boost gauge Tee’d into the the vac/boost line that connects to the fuel pressure sensor. Here are some notes about reading boost… Close Inside the Techco Supercharger Diagram

• 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%.

Checking bypass valve on Techco SC for proper operation

Jun 152010

Every once in a while I get a complaint of a Techco supercharged car not nearly making the boost numbers you’re supposed to see. It can be several different things but every once in a while the linkage for the bypass valve slips which prevents the bypass valve from closing entirely. Here is an email I wrote to someone on how to check it.

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).

Example Fuel System Setup for High Horsepower Hemi engines

Apr 142010

Example Fuel Setup for High Horsepower Hemi Engines

I was bored one day so I decided to draw up a fuel system diagram for a customer that was in dire need of more fuel for their supercharged 426 Hemi engine. So, I might as well share it with everyone.

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