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Re: target a/f ratio in vac
Agreed, I ran my turbo y7 at 16:1 for cruise and got 40 mpg. 8:1 compression didn't hurt.
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Re: target a/f ratio in vac
I get 42 mpg running closed loop on my Z6/Y5 setup 8)
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Re: target a/f ratio in vac
Originally Posted by Inquisition
There is nothing more to say. Flame speed is fastests between 12-13AFR. Anything richer or leaner makes the flame speed down. This means when you run leaner, you need to advance your timing. So you are advancing your timing and removing fuel. This could be potentially dangerous as this could potentially cause detonation. You have to understand the low will be low, but that doesn't mean detonation won't occur. It just means when it occurs, it will be far less severe. So instead of just having your pistons blown to pieces, they will die a slow death and when you go abuse your car for a bit, they will finally fail, even though the tune was fine under the heavier load conditions. In the end, you really have to understand what some are able to do is not what others are able to do. When your knowledge/experience level is low, you can't just tune for 17's AFR and expect everything to be fine. The answer is exactly what I said above. You may be able to go a touch leaner in the 4-6th columns(meaning 14.7:1-15.3:1) but again, is 1-2mpg worth the possiblity of fatiguing your pistons to the point of possible failure?
Tell you what man go ahead and tune your map to between 12-13 all the way accross the board but don't tell someone else to do it. |
Re: target a/f ratio in vac
Originally Posted by snm95ls
Good god man. Have you ever monitered a stock map? If it is so detrimental to the engine to run lean in LOW load conditions then why have the OEMs been doing it for 20 years? You do realize that stock programs do allow for a small amount of detonation at sustained under cruise conditions. Hell even GM, who was pretty much on the forefront of EFI innovation for a long time, ran the craptasm TBI setups into the 17:1 range. That's it, they engineered the damn things to fail due to piston fatigue.
Tell you what man go ahead and tune your map to between 12-13 all the way accross the board but don't tell someone else to do it. PS: Within the last 20 years not too many cars have been lean burning cars. I'd say its fair to say that 90ish% of cars target stoich in cruising conditions due to emmissions. Lean burning cars were anomaly. PPS: The 12-13AFR was referenced simply because people should know that is when the flame moves the fastest. Some people would think that when they lean out their AFRs they should retard their timing because thats what they do under WOT conditions. I was simply illustrating that as flame speed slows down, you need to start the process of combustion earlier to allow the peak cylinder pressure to occur at the optimal point. |
Re: target a/f ratio in vac
You have some good points I will agree.
My reading comprehension doesn't suck. I don't like people that come off as prickish know it alls. Starting your post by saying, "There is nothing more to say." makes you sound like an ass. Your previous post was much more useful. I you don't wnat people to misunderstand information then maybe you should work on your composition skills. Have a good day sir. :-\ |
Re: target a/f ratio in vac
Originally Posted by snm95ls
You have some good points I will agree.
My reading comprehension doesn't suck. I don't like people that come off as prickish know it alls. Starting your post by saying, "There is nothing more to say." makes you sound like an ass. Your previous post was much more useful. I you don't wnat people to misunderstand information then maybe you should work on your composition skills. Have a good day sir. :-\ its the way you read it. and plus, why do you give a ----, this the damn internet. |
Re: target a/f ratio in vac
he gives a damn because that's what caring people do, they don't want to see an idiot hurt themselve or their pockets.
There are some good guys left around here, and not everyone is out to screw the next guy. although it is the internet we should still look out for each other, whether it's good information being passed around or helping somebody who is broken down on a deserted stretch of highway(not w/out my 45 cocked and locked). |
Re: target a/f ratio in vac
I'm one of the caring guys, very passionate about trannys and gas mileage.
Blundell has taken my tune and use it to tweak a few cars when he was bored. On a loaded dyno at that, lean it out till power drops, then and timing. The thing is once below 10" of vaccum, timing is back to stock, fuel is trimmed about 5% over stock. |
Re: target a/f ratio in vac
Originally Posted by Mista Bone
I'm one of the caring guys, very passionate about trannys and gas mileage.
Blundell has taken my tune and use it to tweak a few cars when he was bored. On a loaded dyno at that, lean it out till power drops, then and timing. The thing is once below 10" of vaccum, timing is back to stock, fuel is trimmed about 5% over stock. |
Re: target a/f ratio in vac
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