AFR's guess work or science?
 

I know a little about tuning, so bear with me as i fill in the gaps.

I know that dumping fuel into the cylinders reduces cylinder temps and reduces the risk of dreaded knock. But i've always been told ignition is the difference between a good and a bad tune.

I am guessing the main area's where afr's are key is during transition, ie going from closed to open throttle, if you aren't careful the car will just bog down as it can't burn off the extra fuel?

Re: AFR's guess work or science?
 

Ignition is really what affects power. Any AFR between something like 13.0-16.0:1 will get you within 5% of your maximum power, you really just need to make sure that it stays at very least within that range. For boosted cars you want more fuel for 'thermal management' purposes as you mentioned. Changes in throttle are a bit tricky because it is the rate of change in vaccuum that determines how much air will end up in the cylander at that moment. Usually when a car bogs in this case it is not getting enough fuel.

A car may appear to run quite well on a very very small and fatal amount of fuel.

Re: AFR's guess work or science?
 

what he said!

Re: AFR's guess work or science?
 

yes.. so i guess with wideband you will know that youre runing wrong..

Re: AFR's guess work or science?
 

Or at least with some way to see whats coming out of a narrow band you could make sure youre NOT lean, but for a boosted car you want to make sure its well below 14.7:1 for a lot of the base fuel table.

Re: AFR's guess work or science?
 

if you boost your car and you havent a wideband and you like to tune it.. forget it!

Re: AFR's guess work or science?
 

Agreed.

Here are the guidelines from the EFI University textbook.
This is in lambda, to convert to AFR multiply by 14.7.

Idle - .90-1.0
Cruise - 1-1.05
Overrun - 1.09+ (I believe overrun refers to being in the higher RPM areas with the throttle closed)
Transition (high load, not boosting) - .88-.90
Low/Medium boost - .82-.87
High boost - .80-.85
Dead zones (areas of the table not normally seen) should be reasonable values which follow the contour of the rest of the table.

This is a GUIDELINE. If you were running, say, an air-cooled & turbo Porsche motor you would want much more fuel to help counter the heat.

Re: AFR's guess work or science?
 

Read this about thermal management with Fuel.

http://www.innovatemotorsports.com/resources/rich.php

Re: AFR's guess work or science?
 

runing too rich could tofuck the o2 sensor..

Re: AFR's guess work or science?
 

Very good article.

Re: AFR's guess work or science?
 

Just put those lambda values into my calculator. Came up with around 12-12.5:1 AFR's for high boost, I guess thats about right, but my N/A friends go as low as 11.5:1 on their ITB'ed up all motor racers. I guess i'll have to have a trawl through a few crome .bin's just to get a feel for what other tuners are having success with.

I guess the area it will show most improvement in, is the ignition advance you can run without experiencing knock.

Re: AFR's guess work or science?
 

thats why you disable it

Re: AFR's guess work or science?
 

yep but what would happen if you hook up your wideband in o2 stock hole?

Re: AFR's guess work or science?
 

It'll work.

Re: AFR's guess work or science?
 

so runing toooo rich will not damage to wideband like o2 stock?

Re: AFR's guess work or science?
 

Walter - A never ending question machine.

Read a damn book.

Re: AFR's guess work or science?
 

Ah give him a break. He reads books too.

Yes running very rich will lessen the life of a wideband sensor too.

I just said that it would work if you put it in the stock O2 hole, it's not ideal. That doesn't have to do with running rich, but your EGTs are higher in the manifold than say a foot down the downpipe where it should be.

Re: AFR's guess work or science?
 

i know it will work fine if you hook up wideband into o2 stock hole.. ok ... i just had the doubt if youre runing too rich could can to damage your wideband too. ok. and yes.. it doesnt have to do with to run too rich..

that be the only question.. ;) and yes.. im reading a book about this ----.... ;) i readed if you hook up very higher your WB in the mani , it's possible your wideband could read only mixture of one cilinder or so.. and more shits about it.... ;D

if i had a perfect english i would learn faster about ecu and tuning :-[...

jagojon.. thx brother ;)

Re: AFR's guess work or science?
 

Walter is Curious Spaniard

Re: AFR's guess work or science?
 

12:1 AFR for low boost on most water cooled engines. Richer for more power. At a certain point, more fuel = detonation, but most the HMT guys will never hit that point.

Re: AFR's guess work or science?
 

Evil JD...did you take your Zanax today?

Re: AFR's guess work or science?
 

???

It's spelled Xanax, I can't stand the stuff.

Re: AFR's guess work or science?
 

this tuning thing is tricky :S

Re: AFR's guess work or science?
 

lol no ---- tricky .a lot to learn but i gues it all comes in the end .just a lot of stuff to read about :1 :D