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Discussion and questions related to the course Ethanol & Flex Fuel Tuning
I am building a drag car that uses gasoline direct injection from the factory. I have been running an aux fuel system with 4 injectors for a while and its been fine. But. Recently I have passed into power and boost territory where traditional water meth injection is not cutting it in conjunction with normal pump fuel. I cannot run ethanol mixed fuels, as the vehicle has no way of adding a flex sensor on it, and ethanol pretty much does not exist near me. M1, though, I have lots of M1 available to me.
So. My plan is to convert the aux fuel system into using m1 instead of gasoline. I already have a sizable water-meth tank, and have the parts needed to make a pressurized fuel system out of it.
My question is this; with the limitations I will be listing below, what air fuel mixture strategy would you take for tuning? I would prefer to retain the DI system, as this car will be doing drag and drive events next year.
My plan was to tune the aux fuel system as its own system, and let the car do what it wants to the OEM fuel system as far as corrections go, and use the oem ecu to do my timing and cam adjustments as normal. Issue I see with this is, the gasoline that does get into the system will not cooporate with the methanol air fuel ratio, which could cause problems.
I also was debating on just dropping the OEM fuel enrichment table to 0 by full load, and have the methanol come in as that happens, but my concern with doing it this way and the other way mentioned above is there are no corrections in the aux fuel system, so if there is an issue..boom.
OEM ecu is the only means to tune.
AFR target cannot be lower than 9.8:1 due to ecu restrictions.
There is no way to read lambda, as the ecu reads in AFR only and does all fuel adjustments based on this. (thanks renault/nissan)
There is no way to wire in a external wideband into the oem ECU, as the AFR is calculated in the ecu direct from the sensor, so no 0-5v trickery can be done.
ECUtek tuning software.
Single Tune. No map switching available.
No flex fuel.
Coil packs can be upgraded to stronger ones if need be, but dwell cannot be changed.
This I have going for me:
The aux fuel system is basically speed density tuning without air temp adjustments.
An external lambda system can be datalogged for tuning the aux fuel.
The Bosch HPD5 DI pump (probably the most commonly used DI pump) is only rated to use M15 fuel, you will most likely find that straight Methanol does not have the lubricating properties needed for the pump to survive for long. The DI pump is probably not going to be able to provide the fuel volume to run on straight Methanol at anything other than light loads.
The DI injectors also need to have fuel run through them whenever the engine is running, turning the injectors off will quickly (in some conditions less than a minute of running) destroy them. When the DI injectors fail, they tend to melt the internals out of the injector leading to the combustion gases coming out of the injector and damaging the head and anything in the streams path, as well as potentially causing an under bonnet fire.
Is there a reason why you have to retain the OEM ECU? There are good reason for using OEM ECU's if they can be tuned, but I think that you have gone beyond the capacity of the OEM ECU and would be better off using an Aftermarket ECU, especially one that has a dual fuel capacity. Doing this means that you could have the DI running on gasoline for light load and cruise conditions, with the methanol coming in under higher boost/load conditions.
I think you misunderstand…im talking about using auxillary fuel. Extra injectors controlled and fed from a different source than the main fuel system… the methanol will not be touching the direct injection system…
as for why i am retaining the oem ecu; repeatability and reliability. I work on these specific vehicles that a lot if people use in the road, so i need to make them at street friendly as possible, and to retain all can bus related functions like electric power steering and climate controls, the oem ecu needs to be working.
Uh, you're mis-understanding the AFR target and lambda - the AFR isn't reading the true AFR of the air:fuel, but converting from the lambda.
You can d/l a conversion chart for petrol/gasoline AFR to the corresponding lambda value - then target the AFR corresponding to the lambda you want.
However, failing changing over completely to an aftermarket setup that could control both sets of injectors, you're probably going to have to look at a complete system running in parallel to the OEM, dedicated only to the methanol, that adds that fuel from set trigger points.
That means everything from the methanol tank through to the injectors, with everything being rated for methanol, which plays nasty with many materials usually used in FI systems.
Oh, double check on the vehicle's spec', some are designed for a basic 'flex fuel' with lower values of ethanol?
stoich AFR for methanol is what, 6.5:1
stoich for gasoline is 14.7:1.
Lambda value for either is .6
The Nissan ECU I am working with ONLY has a target map in AFR. The minimum AFR value the ecu can have entered into it is 9:1
You cannot tune this ecu using lambda values. AFR values only. I can log lambda, yes. But i would not be able to tune the methanol accordingly.
I think i am going to just install a megasquirt based system to control the other 4 injectors.
NO - the ECU ISN'T reporting the actual AFR, it's reporting what the AFR value for gasoline that corresponds to the lambda value it's reading from the sender.
If you're running methanol, ethanol, Exx, or C16 at the lambda of 1.0, it will be an AFR of 14.7:1 as far as the ECU is concerned, although the true could be as low as 6.4:1 for methanol. Check out this chart.
As I said, and you agree with, you will need a parallel system for the methanol, which comes in as required.
You won't be able to use the OEM ECU to fine tune the mixture as such, if that's what you mean, as I would expect it to try and correct the lambda to the AFR it thinks it's set to - but as the "ECU"'s gasoline 9:1 = lambda 0.61 = methanol 3.9:1, I expect you'll be able to make it work.
Okay, I see. Sorry for my ignorance. I have been tuning lower horsepower cars for 10 years now, and i am just getting customers now that was 500+ whp.