chuntington101

personally i dont think there is an alternative!! there are may advantages to running a standalone, one being the ability to switich fuel/boost/timing maps when you want.

has anyone tried on demand octane systems?? basically you run two fuel systems, say 1 with 93 octane and one with race or E85 or evne straight meth! they both have heir own tanks, pumps, lines and injectors. then you mapp the standalone so that once you reach a certain boost/rpm you start to switch over the the "other" fuel. so you get a seemless transition form 93 octane gas to E85 or race gas.

this setup has been used by Nelson racing engines and W2Wpowertrain but icant seem to find any articales on them

what do you guys think??.

sorry bakc ot topic now

Chris.

PVD04

iTrader: (23)

The biggest issue with map switching with E85 is that it requires such a large amount of fuel. With race gas, you could have 4 gallons left, fill up with pump, and run your pump fuel map without any concerns. With E85, if you have 4 gallons left and add 8 gallons of pump gas, a 11:1 tune will lean out to ~11.9:1. At that point your octane rating would be around 97. This may be ok, it may not. If your pump gas tune is more aggressive you will likely be too lean. The best way to work map switching would be with a fuel composition sensor that adjusts fueling based upon ethanol content. There is some talk of this on aktive matrix, but it's still a little ways off. At this point with my setup, I don't plan on switching back and forth because it becomes a tuning pain.

-Paul

jordo

iTrader: (1)

That would be sweet, using a gm sensor or something to adjust fuel based on ethanol content.

rediddy69

iTrader: (2)

yeah i also thought about the gm sensor and would also be great for winter blends, in colorado their are a fair amount of e85 stations unfortuneately i go to school in atlanta and their are none.

Dayton_EVO

iTrader: (3)

So how would you go about using the GM sensor?? I would be very interested in trying to get this to work.

Thanks

merkzu

iTrader: (4)

I've got the gm sensor in my car. I hope some time the necessary stuff gets figured out in the stock ECU to make it work for flex fuel, but for now I just use it for an ethanol % gauge. Need a pin to run it to and a rom patch to use the voltage in calculating the octane number, afaik.

scorke

iTrader: (18)

What are you using exactly , part numbers/where to purchase?

Scorke

merkzu

iTrader: (4)

I bought the GM fuel composition sensor out of a 2001 2.2L Sonoma from ebay, and the pigtail harness #88987992 from gmpartsdirect.com. And I had a custom electronics place make a frequency to voltage converter for me, 0v = 0% ethanol, 5v = 100%

The sensors are like $450 + ~$100 S/H from gmpartsdirect and about $650 from a dealer.. go ebay if you want one, cost me $100

All the part number/signal output stuff is at http://www.megamanual.com/flexfuel.htm

oh you'll also want the gm quick connect fuel connectors, the fuel-in is a 3/8th and the fuel-out is a 5/16th, got them at napa

scorke

iTrader: (18)

Sick, do you purge your gasoline before switching or just keep driving until you see the %age come into range?

Scorke

merkzu

iTrader: (4)

I have just been running straight E85, pumps had 73% ethanol when I started in May and are up to 81% now. It read 55% when I first switched, had quite a bit of 92 left in the tank. I was running low 11 AFR's at first, and am right at 11.9/12 AFR now (gas calibrated). I switched from 780cc to 1000cc injectors during that time though so not an accurate measure of how the ethanol blend affected the tune

scorke

iTrader: (18)

Interesting, how much have you adjusted your tune otherwise TIMING wise? How bad has your milage and how have you found it otherwise?

Think it would be possible to somehow use the high/low octane maps and just have a different way to switch it ? I said possible not easy, I know its beyond me and most people on the board but do you think this could be done?

Flex fuel evo, mmmm 20-30 psi depending on the gas, and it knows when to switch to the higher timing maps.

Scorke

merkzu

iTrader: (4)

I haven't really done anything with the timing, its going DB Performance on monday to get cams and tuned on their dyno dynamics, will see what comes out of that.

Mileage has been about 15mpg, got 19mpg on gas. Total cost has been just slightly cheaper to run with E85.

I was really hoping to get the ecu to interpolate the maps, so the low maps are gas and the high are E85, and have it figure out the right timing/fuel for whatever is in the tank. MalibuJack made a post about doing it a long time ago, but no real progress has been made. I gave a go at figuring it out myself, but I hardly know any assembly.

PVD04

iTrader: (23)

The problem with using the low and high octane maps to switch from E85 to gas is that if you set your high octane map for E85, you end up with a map with a leaner low octane map and richer high octane map. If you have sustained knock that lowers your octane number you'll end up with leaner A/F ratios.

With the E85 you can run slightly more timing than you can on pump gas, although it doesn't require as much timing because it has a faster flame front. I was running 5* at peak torque on my previous setup (White Rabbit, stock block, HKS 272s) at 30 psi without knock and making over 500 ft-lb of torque according to data log lab. That same tune made 465 hp according to DLL running 22* at redline and maintaining 26 psi. I haven't played with my tune on my new setup much yet because I'm still breaking in the engine.

-Paul

merkzu

iTrader: (4)

I was thinking of not having knock count in the octane equation, since the real time knock control doesn't need it. Its basically just a long term trim to help with consistent high knock counts, I think it would be a fair trade off to lose that functionality. Maybe not, hard to say without being able to actually test it

l2r99gst

iTrader: (2)

Yes, I agree that would most likely be the approach if the GM sensor is used with our ECU to adjust the octane number for map switching. If this were the case, I would imagine the logic where the knock counts change the octane number would be removed.


Eric