# adapting a b18b map to run a b20, how much more fuel????

#

**1**0.5 BAR

Thread Starter

Join Date: Feb 2004

Posts: 198

**adapting a b18b map to run a b20, how much more fuel????**

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.

#

**2**3.0 BAR

Join Date: Jul 2003

Posts: 6,449

**Re: adapting a b18b map to run a b20, how much more fuel????**

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.

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.

#

**5**1.5 BAR

Join Date: Mar 2004

Posts: 1,301

**Re: adapting a b18b map to run a b20, how much more fuel????**

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.

#

**6**3.0 BAR

Join Date: Apr 2003

Posts: 2,260

**Re: adapting a b18b map to run a b20, how much more fuel????**

Originally Posted by

**ZC4ME**...maybe a sticky would be in order, one with all the magical formulas..

**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.

#

**7**3.0 BAR

Join Date: Jul 2003

Posts: 6,449

**Finding Points on Line (Linear Graphing)**

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)

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)

#

**8**1.5 BAR

Join Date: Mar 2004

Posts: 1,301

**Re: adapting a b18b map to run a b20, how much more fuel????**

Originally Posted by

**TurboEF9**
Originally Posted by

**ZC4ME**...maybe a sticky would be in order, one with all the magical formulas..

**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.

Originally Posted by

**xenocron**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)

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)

Thread

Thread Starter

Forum

Replies

Last Post

5thgencivickid

Turbo Parts For Sale

26

04-11-2005 09:35 PM