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…
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.
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 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.