I'm waiting for my new toy to arrive which is the XEDE with the SMART package, and before I start with tunning I want to find couple of answers. I did some searching about AFR, timing, knock, boost adjustment while tunning the car but still have some questions about the AFR. Please correct me if I'm wrong but I'm trying to understand everything before I start. From some of the posts that I have read when we tune we want to be aroung 11.2:1 (that is what most consider safe), now if the number is below 11:1 does this mean that the car is running richer in fuel (x>11 lean, x<11 rich)?? Also I was trying to find an answer with the xx:1 corelation, what does it mean exactly?? Does this mean xx% of air to 1% of fuel??

 

higher the number = leaner

11:1 is richer than 11.2 : 1

 

I believe it refers to "parts"....11 parts air to 1 part fuel is 11:1. the higher the number on the left, the more air, the leaner. 14.7:1 is, I think, gasoline's "ideal" number. any leaner than that could be dangerous. better to err on the side of safety...although, I am no tuner.

 

AFR is important, but the main is to look at your Timming and EGT. you can a flat 11.1 AFr, but your car running like crap 'cause your engine is knocking all over the place due to the gas and how much boost. more boost doesn't mean more power. Most people bragging about how much their car boost, well you can boost 21 psi on a 20G and it still make more power than 21psi on stock turbo. the main thing is CFM. anyway back to the subject. How can you tell if your car is knocking?? look your timming it should drop down to like 4 and steadily climbing up, but if you see dips than it's knocking.

 

Thanks for all the replys. Could someone verify Zemo theory?? Zemo please don't get me wrong, also I'm not stating you are wrong, I just want to make sure that it is what it is

 

14.7 is considered good for cruising afr, ie light load hyway driving
people run 11. 2 for high load. and you could ramp between the two if you have the software.

20. is just about no gas
6 to much gas to run.

PLEASE don't listen to the afrs suggested above, Warrtalon will have the only afr for anyone to use.

 

Tuning things yourself is very noble and can be a very rewarding endeavor. That said, you have little chance of success without basic foundational knowledge about how engines are affected by tuning changes.

Please...do yourself a service and start by reading this book:

http://www.amazon.com/gp/product/076...books&v=glance

Best of luck in getting started

 

Verified.

Those numbers refer to a ratio on a weight to weight (w/w) basis.

 

Thanks Ted B
Is this all that I should know about the AFR while tunning??
I might start another thread to find more answers about other parameters

 

So whats a good ratio for a tuned evo to be at? I've heard mid 11's, mid 12's and mid 14's. What should they be with and without alky?

 

Depends on boost and octane. I run a knock free 11.1AFR on 91 octane, 1.5bar boost peak

 

off boost you want 14.7........... on boost 11.2

 

No. There is a lot more to it than that. That is why I recommended the book ^^^^ If you are completely new to tuning, it will be difficult to learn all you need to know from this forum...

 

In support of the recommendations above, your AFR will generally be safe in the mid to low 11's at WOT depending on your mods...

This has been covered many many times on this board. Some searches on the topic will yield a wealth of information

 

stock evo AFR's have been between 10.5-9.6. very rich from the factory to keep people from blowing motors. the ideal AFR for an evo is 11.5:1 on unleaded fuel. if u run any kind of leaded race fuel, you can get away with 12:1-12.5:1.

for example, there was a guy in AZ who had his car tuned @ Dyno-Comp but his AFR was 12.5:1 (waay to lean for a turbo car on 91 octane pump gas). he went over to Mynes & they richened the AFR to 11.5:1 & he gained 30WHP!!!!!!!!!!!!!! he also no longer has detonation...