shmaptoe

if i were to make a map to run a b20 using an ls map to start, how much fuel should i add back in to account for the larger displacement. this is running uberdata.basically im looking to take my tuned map, safely account for the larger displacement of the b20 and send it to a friend to get his car going. i think i remember hearing that it is about 15% more fuel, but i kinda want to get second opinions.

Chris Harris

1 - (1.8/2.0) * 100 = 10%

Obviously that is a rough estimate and comes down to actually how many more Oxygen molecules get into the cylinder every cycle, but its ok to start tuning from and with a wideband of course please.

TurboEF9

I couldn't have said it better myself. Math = Your Friend.

shmaptoe

thanks for the replies. ill give it a try then. sorry i didnt do the math myself....

ZC4ME

Hmmm, there may already be a thread somewhere, but maybe a sticky would be in order, one with all the magical formulas that you guys use to figure out the corrections etc... The formula along with a brief explanation of what it does. These type of questions seem to be popping up a lot lately. Just a thought.

TurboEF9

I don't know if anyone has noticed, but, it's all the same formula.

Finding the percent of difference.

Injectors.. ((OldInjFlow/NewInjFlow) - 1) * 100 = How much fuel you need to add/subtract to "zero out" the new injectors..
Air Fuel Ratio.. ((PhysicalAFR/TargetAFR) -1) * 100 = How much fuel you need to add/subtract to hit your target AFR..
Displacement ((OrigDisp/NewDisp) - 1) * 100 = Percent of fuel to add/subtract to compensate for displacement..

Ta-da! ..all the same formula, just applied to different situations.

Chris Harris

Y = mX + b

m = (y2 - y1) / (x2 - x1) <--Slope of the line

If you know the slope of the line and one point on it, you can find b.

b = Y- mX

Then you can find any point on that line.

What's that good for you ask?

Well...most widebands are linear. So are map sensors....and a lot of other Honda sensors.

Y1 = 0v
X1 = 0 (degrees, PSI, InHg, ect)

Y2 = 5v
X2 = 5 (degrees, PSI, InHg, etc)

ZC4ME

See, as trivial as this is to you guys, a lot of people don't know this information. Hell, I have a B.S.E.E.T. and I can't remember half of what I learned and the other half is useless without the half that I forgot Anyway, I think this type of info should at least be added to the Engine Management FAQ.

Chris Harris

Bah...we're just showing off