e85 + 3.0 + megasquirt - whats needed

[Ondonti]

Fuel is usually mixed by the same refinery nearbye all the same stations. Go to a different area, different refinery, different %. In Utah E70 was really more like E66. All the same company for the whole state. All year round because E70 was mandated all year for silly high altitude reasons.
Stay in the same area and you will probably never see much difference in tune. Get fuel from the same place and you will probably be fine. Some places like Costco or others that buy bulk from different places might see more differences because the supplier is not consistent. Unless you have proven you have E10 and Ezero in your tank and seen the same tune (which would make no sense) then you can't say it.


I don't even bother with the AFR table. I built one originally but then I decided that its easier to fix up my own VE table then deal with the stupid wandering AFR in closed loop.

I agree with Ed that changing required fuel makes more sense. The only important difference between E85 and 100% gasoline is the stoic. Change the stoich in required fuel to match your Ethanol % and your tune is spot on. Just because VE tables are more easily switched doesn't mean it makes sense.
If it was me, an Ethanol sensor would directly change required fuel stoic instead of trimming VE. It might work but it does not make logical sense to change VE based on your fueing. It makes talking about engine performance or how engines actually function, very confusing. The only sensible thing about the VE trimming is that it does make sense to have a spark trim and its probably easy (lazy) to use that programming loop on VE. That or maybe required fuel can't be modified on the fly.

I like to think of VE as what it actually is, something that does not change. It is a characteristic of the engine.

SBECII 3.0 on true E66 will run 18:1+ when the normal Gasoline runs out from the fuel lines. That is open loop cold start. I have a video of my first cold E85 start (with E10 still in the lines) but I guess I never uploaded it. That is something that happened between the first junkyard motor startup and running at the track on that motor. Closed loop it should easily be able to drop that back down to 14.7 and destroy fuel economy. No way to trick the ecu unless you lie about AFR values with your wideband (which you can do with E10 and get much better mileage).

[Sundance 6g72]

okay i understand ALL THAT and agree

what i dont understand though is this

I like to think of VE as what it actually is, something that does not change. It is a characteristic of the engine.

everyone seems to be ignoring the fact that different afr will cause the VE table to have different values, even though the volumetric efficiency really didnt change.

if Ed and I both have the same Built N/A 3.0 that he has, and he prefers to have it at 13.5:1 afr and i prefer mine to be at 12.5:1, we will have different VE values. His will have less and mine more. So how in the world does my motor have a higher volumetric efficiency just because im running richer? it dosnt. Its a fuel table, nothing else.


changing the injector size is what ed was talking about. Thats easy, just say your running 30% smaller an injector (or whatever % you have to use) and would work.

changing stoic (or however its spelled) might work.. havnt thought about that much

now i found something weird.... i had stoic (or as its labeld in MS, "Air Fuel Ratio"

this is what ive had it at for a while now. notice 14.7 afr and 8.8ms required fuel



Changed AFR to 9 and then the required fuel went to 10 ish





change afr back to 14.7 and i got 6.6!!! ??? 2 less than before. whats going on?





only variable to be changed was the Air Fuel Ratio setting from 14.7 to 9 and then back to 14.7

wasnt aware that math could change.

[TainterRacing]

What brand is the wide band?? I saw it some time back can't rember....


This is a air fuel shootout a ford mag did.

[Sundance 6g72]

what brand wideband?? prosport, i found mixed reviews for them but thats not what im worried about right now

MS gives mixed required fuel ammounts... as posted above. what gives

edit: i always thought my VE values where a little low but i didnt worry about it.. now i know. had 2ms more required fuel than i needed somehow. Maybe the 8.8 was wrong? i dont know how to manualy do the math.

[RoadWarrior222]

Needs a 6th column, "Advertising dollars spent with magazine publisher over last 2 years" ... just 'coz I R naturally suspicious

[Sundance 6g72]

that must be old news too. AEM can be had for $165 new if you look hard enough, otherwise they are like $200, same with prosport.

inovate i think is 250 but ive heard of someone spending $350 recently...


and i havnt heard of anyone using fast in a long time (not that they are bad or that people dont use them, i just dont see it)

[c2xejk]

everyone seems to be ignoring the fact that different afr will cause the VE table to have different values, even though the volumetric efficiency really didnt change.

Changing the VE table entry _will_ change the AFR, HOWEVER, what you are trying to do is tune the VE table so that it fuels the engine to match the desired AFR from the AFR table.

if Ed and I both have the same Built N/A 3.0 that he has, and he prefers to have it at 13.5:1 afr and i prefer mine to be at 12.5:1, we will have different VE values. His will have less and mine more. So how in the world does my motor have a higher volumetric efficiency just because im running richer? it dosnt. Its a fuel table, nothing else.

If the engines are identical, the VE tables should also be identical. If you desire a richer AFR, you change the AFR table NOT the VE table.

changing the injector size is what ed was talking about. Thats easy, just say your running 30% smaller an injector (or whatever % you have to use) and would work.

If you look at the injector sizing more as a BTU/hr, then you are just updating it for the fuel provided to the injectors.

The flex fuel sensor seems to be the best option though. In some reading, there seems to a cheaper ($50 new) one out there, but I don't know much about it... (this was mentioned in some of the mega-squirt documentation.)

On stock ecu not varying, it has been my opinion that the ecu uses long-term fuel modifiers calculated in closed-loop to adjust the WOT fueling...


Joe, in your screen shots above, why do you have number of cylinders set to 8?

[RoadWarrior222]

Yup, you'll only get 3/4 the injector you need calculating for 8 cyl!

[Sundance 6g72]

just saw the 8. WTF.



this

If the engines are identical, the VE tables should also be identical. If you desire a richer AFR, you change the AFR table NOT the VE table.

contradicts this

Changing the VE table entry _will_ change the AFR, HOWEVER, what you are trying to do is tune the VE table so that it fuels the engine to match the desired AFR from the AFR table.

how in the world will changing the afr table ever change your tune? (with all closed loop settings turned off, running from just the fuel table.

[Sundance 6g72]

figured out the 8 cyl thing. That was only used in the required fuel calculation. changed it to 6 and it took me back to 8.8 (my origonal value)

so nothing is actually wrong, ignore the 6.6 part. The actual amount of injectors is 6 and it was always set as 6.

before i got MS, i had this problem when tooling around in ed's tune. I would go into the required fuel calculator thing and it would default to 8 cyl even though ed never put it to 8.

i never ran it as 8, it simply defaulted and i didnt catch it when i took the picture

[Ondonti]

I think this is just getting twisted. We don't even need an AFR table with megasquirt. You don't need to use closed loop.

When it comes to VE, VE is something that does not change. VE = volumetric efficiency. Let us concentrate on the word efficiency. You set your VE to make the most power at each load point. Anything else is not efficient. If your wideband says a different value, that doesn't mean the motor changed its characteristics, it means you changed the VE value. Your choices do not change how much air flows through the engine.

If you have the same motor and different VE tables, each person will have load points that are either better or worse then the other's. Best case senario would be both people having the exact same tables because there is only one optimum setup.

Yes you will modify the VE table to suit what you think the proper AFR should be but if this was an OEM setup, there is just one thing that is correct and that is optimum (either for efficiency or emissions or both). Different load levels have different optimum AFRs but the differences in RPM points simply reflect the motors increased or decreased ability to swallow air (VE!!!!). AFR should be almost a flat line across any load bearing part of a row and only change as VE changes with RPM. If your measured AFR changes throughout the same load range, then you have the wrong VE values.

[Sundance 6g72]

thats what ive been trying to say this whole time. The only way to adjust your AFR directly is to edit the VE table. (assuming the engine constants settings are correct) true VE for an engine will never change unless something is directly done to effect the flow of the engine. We all understand this. What i dont understand is the importance of having the 100% correct VE values in the VE table

what i didnt say or think about is what afr gives peak power. if 12.9:1 afr gives peak power for a certain WOT load, then the ve value for that load point is the true VE? Makes sense to me BUT what about VE values for low load low rpm (cruising) They will be less than the real value because noone cruises around at 13.2 (or whatever peak power afr it would be)

my point being is that the ve table is hardly exact in real world examples. pump gas might make most power in the 12 afr but for boost we are targeting the 11s and sometimes people target the 10s. Obviously the VE values in those areas will be higher than the true volumetric efficiency. Adjusting the AFR table wont do anything to help this.. its a target table and will not effect fueling.. unless there is a calculation in megasquirt that i am missing. something that takes the true Volumetric efficiency value for a certain loadpoint, then checks the AFR table for your desired AFR and then crosschecks that with your engine constants settings and finds the perfect amount of fuel to inject into the motor but i doubt thats the case. The afr table is used for autotune features like closed loop and megalog viewer or analyze live.. all of which edit the VE TABLE to get you your desired afr.

i think we are all on the same track, just saying it differently and not understand each other. And when it comes to switching back and forth from gas to e85, we have our preference of what MIGHT work best but as far as i know the only person to run e85 was brent and i dont know if he has ever ran it with megasquirt and had to switch back to gas. Just like how he works his timing tables, it kinda makes sense to me but i still dont understand how he does it.


so for me (not everyone else) my preference would be to have two ve tables because they can be imported and exported at anytime without having to mess with the engine constants settings. Im going to try changing the "air fuel ratio" setting from 14.7 to the stoic afr for e85 and see what i get.

[c2xejk]

my point being is that the ve table is hardly exact in real world examples. pump gas might make most power in the 12 afr but for boost we are targeting the 11s and sometimes people target the 10s. Obviously the VE values in those areas will be higher than the true volumetric efficiency. Adjusting the AFR table wont do anything to help this.. its a target table and will not effect fueling..

WRONG! The VE table is used to calculate the amount of air entering the cylinder. Then to calculate the amount of fuel needed, you look to the AFR table so that you know the desired air/fuel ratio!

You can change the air fuel ratio (and fueling) by changing the AFR table and NOT touching the VE table!

[Sundance 6g72]

i dont want to say your wrong but i need you to go into detail how touching nothing but the AFR table (picture below just so we are 100% specific) will change the tune because i have never done that and i dont even remember us changing the AFR table at drag week in order to dial anything in. in fact, i dont think we ever touched it.. we just changed the ve table after doing pull after pull and then parking in that business's parking lot to look at the datalog then manual changine the VE table.



DIY told me to edit the VE table to get my desired afr after making the switch to e85.. so excuse me fro being so stubborn but they do ALOT of tuning on many different cars.

[c2xejk]

Just looked through a couple pages on the MS and you may be right. That said, it is not how it is supposed to be done. Every text book I have read on the subject says that you should calculate the cylinder air (via the VE tables) then divide that by the desired_AFR to determine the amount of fuel needed.

It appears that in the MS, they have mashed the VE and AFR tables together and then given you another table that they call AFR. The only reason I can see for doing that is throughput, it really is a poor design...

[Ondonti]

AFR Table is only for closed loop on the fly adjustments as I said earlier.

MS's fueling equation just uses VE as your user input. Its called VE. In my opinion there is only one right VE value in MS, whether or not its actually the amount of air your engine moves. That is because there is only one optimum AFR for each load point. Having a VE and AFR table that worked together would be great if closed loop was really that reliable. I don't see a need to ever use closed loop.

[Sundance 6g72]

closed loop for me dosnt work that great but i have gotten it to work better to where i was satisfied but i havnt had much time to mess with it obiously.

but yes, like i said, the afr table is only for closed loop stuff and the datalogging software that changes your tune based on what happend in the log and what your AFR says it wants it to be.

thats why i dont like it being called a VE table.. not sure what to call it other than that. I mean, it gets pretty close to actual ve but a turbo car will deff suffer from an offset value due to running so rich.

Anyways, now that all three of us are in agreement, where were we? :P

[RoadWarrior222]

I dunno, maybe you took a wrong turn in Albuquerque ... try asking the little guy with the big red moustache.