Air to fuel ratio

[V8 Beast]

When I spray my air to fuel is about 10.8:1. Currently I have 94 in the tank and c14 in the fuel cell. If I go with a lower octane gas will that have any impact on the air to fuel. Also when spraying whats a safe air to fuel without having to worry about drowning my plugs.

[Draco-REX]

Not sure about proper ratios when spraying, if I were to guess, it'd be about where you're at now.

 

As for lower octane gas, the AFRs won't change. However, lower octane means the fuel is less stable. So often the fix is to run the mix richer to compensate.

[V8 Beast]

10:1 is too rich for these cars. I'm just not seeing a lot of movement with changing jets alone so I thought I would check. I'm going to keep stepping them down until its right.

[Guest Spam]

It depends on how the ecu reacts to the car. I know nothing about V8's but lowering octane to compensate on a turbo car affects the car by either detonation, therefore hurting performance as the ecu pulls timing to protect the car.

 

For instance, running e85 on my car requires 30% more fuel than typical 93. So if i were not to compensate, i would run a VERY high AFR.

 

What do you want the AFR's to be when you spray?

[Billiumss]

Depends on the gas.

 

You want about a 11.3-11.6 AFR for N20.

[Guest Spam]

Depends on the gas.

 

You want about a 11.3-11.6 AFR for N20.

 

Is that on a typical 14.7:1 stoich wideband?

[Billiumss]

Wideband O2

[V8 Beast]

Depends on the gas.

 

You want about a 11.3-11.6 AFR for N20.

 

Thats what I thought, thanks. I've got it from 10. to 10.8.. Hopefully one more jet change will get it to 11.3.

[Guest Removed]

on spray...dont trust the wideband.(mixxing the pump gas and race gas in the chamber, and dumping out the exhaust, is why you dont want to trust the wideband.)

 

read the plugs. i always went by egt's at the collector myself. and reading the plugs. it will mean shutting it off at the end of the run, pulling a plug on the return road and reading it.

or pulling the plugs, drag it back to the pits.. and pull them all is what you really want to do

it could be showing rich, and be lean... you really dont know, till you look at something thats been in the chamber... not the top of a piston after its exploded and made a big mess and all you see is damage.

Edited April 25, 2010 by Removed

[Cordell]

Depends on the gas.

 

You want about a 11.3-11.6 AFR for N20.

 

This only partially acurate, because it has everything to do with how much you're spraying. My target A/F is at 11.2 when spraying for a little safety factor.

 

Let's just say you're target A/F is 12.8 when n/a and your car make 400hp and you spray 100hp shot, use the following equation.

[(400/500)x(12.8)]+[(100/500)x(7)]=11.64 new target A/F

Simple HP numbers and how they coordinate with the target A/F for air and nitrous.

 

This is accurate, and I'd also do what Gearhead talks about and learn to read the plugs. This is a science in it's self.

 

Also keep in mind that the cylinders will not all get even distribution on an LS1 without a directport, so make sure the safety factor is there. I personally like to add fuel to the injectors as well on a wet shot by about 10% to make sure there is at least a good distribution of fuel. Beleive me I've learned the hard way and have done my research.

[neonkiller]

lead gas fucks up wide-band sensors, When the VW was chugging it every weekend, I used 4 in one summer for my AEM and car 02 sensors. $$$$$$$$$ I would change your wide-band sensor out every year just to be safe and make sure its reading accurately

[koolrayz]

use the VP ms109 instead of the leaded fuel.

Wide band does not take the place of correctly reading plugs. You can use the wideband to insure your staying in the same A/F range, but that range is determined reading plugs.

[Nate1647545505]

Different fuels have different stoichiometric points -- even different blends of octane. You need to find out the H/C and O/C ratios from the vendor and crunch accordingly.

[Nate1647545505]

This only partially acurate, because it has everything to do with how much you're spraying. My target A/F is at 11.2 when spraying for a little safety factor.

 

Let's just say you're target A/F is 12.8 when n/a and your car make 400hp and you spray 100hp shot, use the following equation.

[(400/500)x(12.8)]+[(100/500)x(7)]=11.64 new target A/F

Simple HP numbers and how they coordinate with the target A/F for air and nitrous.

 

This is accurate, and I'd also do what Gearhead talks about and learn to read the plugs. This is a science in it's self.

 

Also keep in mind that the cylinders will not all get even distribution on an LS1 without a directport, so make sure the safety factor is there. I personally like to add fuel to the injectors as well on a wet shot by about 10% to make sure there is at least a good distribution of fuel. Beleive me I've learned the hard way and have done my research.

 

Quoted for truth