Hey guys,

I have been wondering about my difficulties tunning my AEM EMS with alcohol injection. Specificly durring spool up.

I figured it out!

While using boost comp tunning in the AEM EMS it is assuming your volumetric efficiancy remains for all intents and purposes relativly constant. If you have an alcohol injection system that "ramps up" over a range of boost then this totally screws with a system that is tunned in boost comp.

In boost comp tunning your fuel map for a given RPM at any boost level from 5 psi to 35 psi is a flat plane with no changes.... but with a suplementary fuel system (alcohol injection) that ramps up over a specified boost range your fueling needs change over that boost range rather than remaining constant. I figured this out when swapping out my spring in my wastegate I was running 18 psi instead of my normal 24 psi and my A/F ratios went from 11.0:1 up to 11.8:1 due to less alcohol being injected at 18 psi than is injected at 24 psi.

If there is a way to set up the SMC kit to either be on or off rather than progressive ramp up I will do so, otherwise I am going to set up my SMC kit so that my "full blast" alcohol injection is 1 psi above my "onset" boost pressure.

Keith

 

Yeah, I was going to just suggest setting the min/max proggressive settings at the same psi to make it an on/off system basically.

 

This was another reason why I moved to using the NOS maps tuning each rpm and load breakpoint for fuel and ignition on the AEM using the SMC pressure switch and did the write up on in the AEM section. It will eliminate the latency on spoolup in different gears and you can tune the NOS maps for what ever setting you set the SMC controler too as it progressively ramps so you get no lean areas and the correct fueling is achieved during pump activation. Otherwise you are guessing how much alky is getting into the system and depending on what gear and how agressive your drive may or may not be it won't be the same.

 

I have been going crazy trying to self tune my evo for alky, I did pretty good job for pump gas but with alky the afrs were all over the place and I was getting real frustrated. That totally makes sense now. So what do the big tuners do about this while tuning the cars?

 

Well today I switched the system to a basic on/off and tuning it was much easier, tried to get to the track but ended up being to busy, maybe friday. I am still very interested in how tuners go about tuning alky...I have been thinking about it a lot and I just can't think of what they do unless they tune for a AFR range thats fairly safe that way if it bounces around it will be ok.

 

I also found it much easier to tune with just on/off- the idea of using the nos map would be the way to go.

 

how much whp gain will you get by installing the alky kit?

 

I've been saying progressive on an EMS is useless from day 1. Glad you found the same.

 

I am beginning to wonder why you would want progressive other than to conserve spray, I would love to hear from a tuner on this topic...

 

Conserve spray is one...second is if you have a stock ECU setup where you can't remove fuel by boost pressure (like an AFC w/o the MAP mod, or DSMLink..etc). In this case having a progressive makes the car run better during spool up / more tunable -- instead of dumping all the alcohol at once at a low boost pressure.

Any system where you can tune fuel with RPM vs boost, progressive is not necessary, and as noted here sometimes a little troublesome.

 

Progressive will make a nicer transition. Not to talk about AEM EMS for now... Without a progressive controller, an engine may see a nice 12.5AFR at tip in and drop to a 10.0AFR abrupty. The bigger nozzle you have, the bigger problem it is.

I see that you are using an UTEC. My way of tuning UTEC with alky is to find a boost level where the load site changes. For my car, it changes from load site "10" to "20" by 7psi, so that's where I set my SMC to start spraying. Then do a lot of logs and pull out fuel gradually until I see a nice transistion when alky kicks in at around 7psi. I hope it makes sense. Yes, it's very time consuming, but it can be done.

 

although my experience is a little different, we are running E85 with 5 injectors. (its a 250cc 4 cylinder 4 stroke with turbo). our 4 primary injectors fire all the time, but they were sized to small and reach 100% duty cycle before redline. interestingly, the engine is also restricted per the rules, and even at max airflow the primary injectors at 100% duty cycle can keep enough fuel flowing to the engine to keep a steady .85 lambda (a/f). because the 4 primaries were reaching 100% duty cycle we decided to go with the 5th injector to move the duty cycle of the 4 primaries back down to a controllable range. we started with a bang bang type controller you describe.... on/off 5th injector spraying the alcohol. this turned out to be extremely problematic as the 5th injector threw off the a/f ratio so bad the engine hardly wanted to keep going when the 5th injector turned on. the ECU has a 16x16 fuel table for adjustment and we compensated with the 4 primaries by reducing pulse width, but regardless there was a non-linear fuel flow rate going to the engine causing wild jumps in the a/f. the 5th injector was triggered with manifold pressure, thus when we reached a certain boost level, it turned on, and it turned off when it reached the turn off value.

per the advice of the ECU manufacturer and our mentor (a honda CART engine R&D engineer) we developped a pulsing 5th injector. the 5th injector pulses with crank angle, and the pulse width is dependent on manifold pressure. we no longer have a massive spike in a/f ratio when the 5th injector turns on. we have quite a bit more tuning to do with the 5th injector, but it is clear the progressive injector is far superior if you have the ability to tune yourself. keep in mind that the 5th injector we were using was supplied with the primary fuel line (50psi) and was the same size as the 4 primary injectors, therefor when it turned on, we were instantly getting 20% more fuel flow with the on/off controller.

i have the AEM software and there is quite a bit of capability there. if you have the time, i would work on making a smooth transition with the progressive 5th injector. your engine and a/f ratio will love you, and you will feel a smoother powerband.

 

I agree with you 100% on the idea that it can be done a bit smoother with a lot more effort. I could either wire the "spraying" indicator output from the SMC controler into the AEM EMS wire harness to tell it that when the Alcohol starts spraying to switch on the N2O mapping tables for fuel and timing compensation (best solution) or abandon the boost comp fuel strategy and go back to cell by cell tunning of the fuel map (would be very smooth.... just a pain in the *** to tune compared to boost comp).

My primary injectors are 1000 cc, so the alcohol injection is a small percentage compared to my primarys.... so the A/F ratio spike is not nearly as bad with my setup as it was for your 250cc project.

Keith

 

This is exactly what I spoke of above, it is what I have been doing for quite sometime and several people use it. It works much better, check it out.

https://www.evolutionm.net/forums/sh...d.php?t=151383

 

Update:

I asked Dave Buschur if he could set my car up like this, and he said "yours isn't like that? We set them all up that way now!"

So, anyone getting an SMC kit from Buschur who has the AEM EMS it will be set up this way.

Keith