maf tune theory questions

[thebeewantsboost]

how smooth should a maf curve be?
and i've been wondering and thinking about how a maf tune helps, is this about right?

in part throttle/cruise... you're basically just reducing your fuel trims as much as you can... does this help throttle response? mpg?
obviously wot is the biggest gain.. and its cuz its actually happening in open loop. the only way it can be dialed in, is manually with a wideband... and when the afr is most correct, you will have the most power.????

[Perforator]

I don't worry about the smoothness of the curve too much. I worry more about how close my fuel trims are to zero in closed loop and how close to the commanded a/f ratio I'm at in open loop. As far as power goes, the leaner you go the more power you make to a point. You need to dyno to know for sure where you make the most power.

[murphinator]

my understanding is where it helps with 3800's is that trims carry into WOT so if you can get them locking in at 0 you dont have to worry about leaning out from the trims pulling fuel at wot

[thebeewantsboost]

the leaner u are, the more power??? really?

i had a pretty good afr error% then i smoothed and, it threw me way outta wack so... thats why i was curious bout smoothing. don't think i will from now on.

[murphinator]

the leaner u are, the more power??? really? .

you left out where Perforator said "to a point" too lean and you will damage components.

you are normally aspirated correct ? if yes then at wot you want to be somewhere in the 12.5-13.0 afr range " in most instances" - when you add boost you will want to dip into the mid to high 11's "typically".

[thebeewantsboost]

i've j/never heard that you want to be lean at all... so my stoich is 14.4 (up to 10% ethanol gas) what should i be aiming for?

[angrygoat]

if you are using that as your stoich then I believe you need to make the change in you stoich table to reflect that and then continue to shoot for 0% fuel trims.

As far as AFR, N/A you want to shoot for 12.8-13.2 is where you should see your best tq numbers using a normal stoich of 14.68. If you are using 10% ethanol and a stoich of 14.4, then lean and rich best torque will be along the lines of what Murph said

As far as the smoothness of the graph, you want a 0% afr error but if you have to choose between a smooth graph and a 0% afr error, choose a smooth graph. You have to remember that a drastic change in the MAF from one table to another could lead to a stumble or a jump in tq when crossing from one cell to another. Also keep in mind there are always small errors or slight throttle transitions that could be affecting you wideband readings.

[Bandit gs]

If you're tuning with a wb your curve won't be "smooth" per say, you'll get small dips and rises, that's ok.

[thebeewantsboost]

just a simple question..

when tuning for "up to 10% ethanol" gasoline by changing your stoich to 14.4(or whatever you choose)

logically... i would think the car is gonna use more gas...
but i was wondering if anybody knew from experience because i could also see the car running more efficiently, and under moderate throttle, possibly getting better mileage
i really like to know why and how things work so i thought i'd ask the pros!

[angrygoat]

If I understand it correctly, it doesnt run more efficiently but it will use more fuel and mpg will go down because of the lower stoich value so you wont be able to burn as much are per fuel mass.

Personally I think its a shady way for the gas companies to get us to use more fuel

[murphinator]

Personally I think its a shady way for the gas companies to get us to use more fuel

there are tax advantages based on percentage of ethanol in the fuel thats why its present in most states

[angrygoat]

so they get a break while we get hosed....do I have that right

[LETZRIDE]

just a simple question..

when tuning for "up to 10% ethanol" gasoline by changing your stoich to 14.4(or whatever you choose)

logically... i would think the car is gonna use more gas...
but i was wondering if anybody knew from experience because i could also see the car running more efficiently, and under moderate throttle, possibly getting better mileage
i really like to know why and how things work so i thought i'd ask the pros!

at 10% ethanol I believe stoich is 14.1 irrc, 0% ethanol is 14.7 (14.68 in our cars I believe) and if you want to tune somewhere in the middle, I believe the reccommended number is 14.4.

Stoich should be the point at which you get the maximum combustion of your fuel so that all the products are used up. It would be the cleanest and most efficient as there should be no products left over (atleast this is what I got when I was semi paying attention in chem class)

ethanol brings the stoich number down, so depending on how much ethanol is in your gas, will depend on what your stoich should be set at...since over here it is always "UPTO" 10%, I opted to put 14.4, since it wont always be 10%, and it won't be 0%, so 14.4 is going to be closer to stoich then 14.1 or 14.7 will in my opinion.

[passingpower]

All things being equal on a reasonably (factory) or well (HPTuners) tuned vehicle; going from 100% petrol to 90% petrol/10% ethanol, there WILL be a drop in milage. That happens because the NB O2s will pull the fuling to stoich and we'll see a consistant +4% LTFT. If we calibrate our Base Stoich AFR to 14.13:1 for 10% eth and go ahead and burn 10% eth, we'll get the same stoich and same fuel consumption. The only difference will be with the trims, LTFT will be 0.0 because the Base AFR will be holding stoich WITHOUT being modified by an O2 signal.

[thebeewantsboost]

so. in a town where all the pumps are "up to 10% ethanol. every fill up is going to lead to different fuel trims, awesome!

[murphinator]

so. in a town where all the pumps are "up to 10% ethanol. every fill up is going to lead to different fuel trims, awesome!

since they get the tax breaks on the ethanol they purchase they probably mix as much of it in the fuel as allowed , there are some pushing for e 15 for this reason - no good reason to only put in 5% if your allowed 10% so I run 14.13 for stoich on this logic but have no test data to back that up

ethanol is good for making power like e85 or e98 for example but unfortunately they are mixing these low percentage ethanol blends in a manner that octane numbers dont improve - nobody ( on this forum at least) would be bitching if e10 were 96 octane

[bilemke]

Yeah.. If they are mixing ethanol in, it should be boosting octane, but it isnt.. They are using it as a cheap way to get the octane up to the normal levels they always sell.. Basically, you are buying cheapened down gas (the ethanol blend has less energy in it the the gas without it, so you are paying the same amount to get less energy and ultimately less mpg).

[TeacherCreature]

so. in a town where all the pumps are "up to 10% ethanol. every fill up is going to lead to different fuel trims, awesome!

Yup happens to me all the time Tryin sticking to one gas station if you can preferably a larger one.


BTW am I the only idiot tuning WOT on a narrowband lol?