Ideal A/F ratio for NA/Boost

Boostin · Post by **Boostin** » Wed Feb 10, 2010 11:03 pm

I am curious on the actual ideal fuel air ratio for NA motors and turbo motors.

Should there be a "difference" in ideal A/F ratios between the two?
...I hear there is a difference but not from experts like you guys...

I am trying to understand what idea is and if there is a difference on the two builds and any and all information backing this.

I do not just want an answer (fix), I have to understand the why also...

PS: I am brand new, first post, first build, first attempt to understand tuning/hondata/ and A/F ratios!

Love hondata!

Martian · Post by **Martian** » Thu Feb 11, 2010 1:35 am

Boost is upping the effective compression ratio. N/A builds use high comp low ends. Therefore you tune fuel to make power and protect the motor from high compression detonation and preignition. Are they exactly the same, no. But the same principle stands. Leaner is meaner, but wetter is better.

Boostin · Post by **Boostin** » Thu Feb 11, 2010 10:07 pm

that does help the understanding...Thank You

What is the ideal A/F ratio to completely burn 91 octane fuel?

darkstarsinner · Post by **darkstarsinner** » Thu Feb 11, 2010 11:12 pm

There really isn't an exact answer for this that is universal. 14.7 is the usual base for typical gasoline, but you also have to take into effect the build of the motor, and the HP goals. Lower is leaner and over is rich.

Boostin · Post by **Boostin** » Fri Feb 12, 2010 1:31 pm

14.7 was the number I was trying to confirm.

When you say lower; as in 13.5<14.7 = leaner and 15.2>14.7 = richer?

I have an AEM wideband O2 with gauge; running s300.

Thanks for the information!

Ohh ya, here is my car specs (i might of forgot somethings but ya...)
Car specs:

d16a6 block
d15b Vtech head
t3t4 turbo
Hondata s300
255 walboro fuel pump
1000 cc injectors
AEM fuel reuglator
AEM wide band sensor and gauge
AEM boost solenoid
Hondata 4omni bar map sensor
CP pistons
Eagle Rods
ARP head studs
Brembo slotted ported rotors

...NEW OEM
water temp sensor
fuel filter
oil pump
water pump
alternator
thermostat
air temp sensor

darkstarsinner · Post by **darkstarsinner** » Fri Feb 12, 2010 1:46 pm

I'm sorry I said that backwards. Less is rich and more is lean. So 13.5>14.7 15.3<14.7. But your tuner is more then likely going to want to start at 14.7 and play with it from there. Give a little, take a little until you can find the lead you need.

Boostin · Post by **Boostin** » Fri Feb 12, 2010 1:56 pm

Awesome news.

...that is what I was thinking that it was backwards

roughly run 14.7 at idle and push a little rich to 12.5 during boost? (safety First)??

Is there an optimal point where detention occurs always?

Thank you a bunch.

Good thread too, I thank everyone for that too...only facts

Martian · Post by **Martian** » Fri Feb 12, 2010 3:55 pm

Detonation occurs when parts get hot. So we use a little extra fuel to help cool stuff down again. This is also the same reason for geting colder plugs. Small little things add up to big problems if you know what I mean. But to answer the question, no. there are many factors that contribute to heat, which in th end is the problem.

Boostin · Post by **Boostin** » Fri Feb 12, 2010 5:03 pm

That is what I was thinking, I just needed to confirm that there wasn't an idea A/F ratio to cause more detention than others.

Thanks once again!

darkstarsinner · Post by **darkstarsinner** » Fri Feb 12, 2010 6:17 pm

Just keep in mind as posted up above the leaner you run the more chance you have of detonation. This is why it is so important to start at the common base line and SLOWLY work out your actual map.

newsoltsc · Post by **newsoltsc** » Sun Feb 14, 2010 2:09 pm

My tuner has me running rich while in boost. My AEM WB02 reads like 11:1 when in boost.
Better to be protected then unprotected.

But when Im in idle/not in boost its roughly 14.7:1 / 14:1.

I feel a lot safer this way.

Boostin · Post by **Boostin** » Thu Feb 18, 2010 11:44 am

I was curious on the actual "tuning" side of s300 (haven't tried just curious)

When I datalog/record a run, I can go back in and watch the run...

Watching the AF ratio during the run, can i...find low area and move the fuel in those columns up then load that to the ecu at a later date?

I don't think i explained that well...

step1 - I datalog/record a run 1st gear to 5th gear...
step 2- I come home and load that datalog onto my inside computer
step 3- I watch everything focusing on my AF ratio...
step 4- I notice at 4500 in second that I am running LEAN
step 5- I change the fuel level for that section higher (just a little bit)
step 6- save calibration to laptop and take out to the car
step 7- upload NEWLY changed calibration to ecu...
step 8- Datalog/record a 2nd run 1st gear to 5th gear...
step 2- I come home and load that datalog onto my inside computer
step 3- I watch everything focusing on my AF ratio...

I work 60+ hours each week and datalog after work (but its cold and i am usually dead on the feet) So i spend a lot of time reviewing inside (heated area) and making changes inside....

Will this process be ok or should I make changes as I drive it?

The thing I am wanting to confirm is;
I pull a calibration with datalog to my inside computer...study it and change it (fuel/spark) when necessary....then upload back to the ecu...test the calibration again (next day)...

Is this fine or will I experience problems?

Just need experienced people to put their 2 cents in on tips/pros/cons/suggestions...

Thanks everyone!