nitro2 wrote: ↑Sat Oct 02, 2021 11:41 am
If you were to run 20% through an EFI there should be no reason to blow down before restarting as the EFI should be shutting off the fuel when the ignition is shut off so the crankshaft spins X number of times with no fuel going in before it comes to a stop, and really there should be next to nothing unburnt in there anyway at idle with EFI.
Bringing this thread back up because I noticed this while rereading through it.
I can only speak with knowledge of higher percentages of fuel. You shut the fuel off at engine shutdown at the end of a pass or running in the pits, you do not cut the ignition, plug leads are then pulled, and only then the ignition is turned of. Some may have a different procedure.
The reason is that some ignitions can make a stray spark when power is cut when the engine is still rotating and the ignition is activated.
Some have pointed out a confidence in different procedures when running an amount of percentage they are familiar with.
20% is basically nothing compared to high percentages, as far as nitro volume is concerned. If you do the math you'll see what I mean.
Engines that operate at high percentages, when they are at idle on nitro, the plug fires every time as it should, BUT the nitro only lights about every 3rd or 4th plug firing and since there is very little airflow at idle, well you can see how fuel accumulation could be a problem if the shutdown is not done in a very specific manner. However, 20% with EFI is nothing like that scenario.
nitro2 wrote: ↑Fri Jan 21, 2022 1:43 am
20% is basically nothing compared to high percentages, as far as nitro volume is concerned. If you do the math you'll see what I mean.
Engines that operate at high percentages, when they are at idle on nitro, the plug fires every time as it should, BUT the nitro only lights about every 3rd or 4th plug firing and since there is very little airflow at idle, well you can see how fuel accumulation could be a problem if the shutdown is not done in a very specific manner. However, 20% with EFI is nothing like that scenario.
Noted.
How do you go about determining the amount of nitromethane needed to reach a certain air/fuel ratio?
For example, you have an EFI NA setup, 11:1 compression, already tuned for E85. You take an E10 93 octane pump gas at ~14.1 stoich and you want to add nitromethane until you reach the same ~9.8:1 stoich you had with E85 so fuel tables can remain about the same. I'm sure it's not as simple as just adding the stoich numbers together and dividing according to the blend ratio. Would you calculate the fuel flow required for each fuel if it was the sole fuel based on recorded CFM and VE data and then do a add/divide by ratio from there?