air/fuel ratio

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glanzamike89

Fresh Recruit
is running 11.5 safe just asking because my tuner sed its a bit to lean so he richend it up a bit? and lost 6bhp lol is he bein over cautious
 
M

monka

Member +
14.7/1 is deemed there perfect ratio, so I don't see why a tuner would do that,

New to mapping perhaps?
 
S

Starbus

Member +
monka said:
14.7/1 is deemed there perfect ratio, so I don't see why a tuner would do that,

New to mapping perhaps?
Click to expand...

Not as new as some people ;)

AFR means nothing on its own.

As above, 14.7 means stoich for petrol. (different for other types of fuel) 14.7 is also known as "lambda".

In closed loop mode then engine will run around 14.7, realistically between 14-15AFR.

On boost or anything more than very light throttle this will richen up.

11.5 is perfectly safe for most cars, 11.8 is usually what most map to, maybe richening slightly in certain engine types. Rotary engines for example run 10 AFR.

Anyway, It sounds likes he's been overly cautious, but what is your engine spec?
 
Jay

Jay

Admin
monka said:
14.7/1 is deemed there perfect ratio, so I don't see why a tuner would do that,
Click to expand...

14.7 is ideal in a controlled environment. Add to that real world factors and a great number of variables and you will find that the ratio will need to be much richer on boost.

It varies between tuner and ultimately you should trust what your tuner is doing. If he feels that 11.5 is suitable for your setup it probably is a balance between power and safety.

For what it's worth I would normally aim for that area to ensure a safe tune but it depends on the car. On boost I would stay far away from 14.7 as it's liable to pop.
 
GTti

GTti

Member +
There has been many who report the stock EP82/91 ECU fuels at 10.5:1 on WOT.

11.5 is fine, I personally wouldn't run any leaner.
 
M

monka

Member +
Just looked at my rr printout, top of the rev band wot just over 10.5 started at 13.5 on 1600 rpm wot

So would I get more power if at top of the rev range instead of 10.5 I'm at 11.5, or more power from being less than 10
 
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jabran200

Member +
11.5 at wot is being safe but running 12:1 will achieve more power usually but tuners tune to 11:1, 11.5:1.

I personally go to around 12-12.2 on my cars and toward the really top end of the rpm I use 11-11.5:1 but those areas are rarely entered to during driving or racing.

tbh I would leave yours at 11.5:1 as thats rich enough.
 
M

monka

Member +
Just looked at my rr printout, top of the rev band wot just over 10.5 started at 13.5 on 1600 rpm wot

So would I get more power if at top of the rev range instead of 10.5 I'm at 11.5, or more power from being less than 10
 
S

Starbus

Member +
monka said:
Just looked at my rr printout, top of the rev band wot just over 10.5 started at 13.5 on 1600 rpm wot

So would I get more power if at top of the rev range instead of 10.5 I'm at 11.5, or more power from being less than 10
Click to expand...

You'd get more power been at 11.5.

But your tuner knows this, what is the car's spec?
 
Jay

Jay

Admin
Less is more, the lower the number the more fuel there is.

Leaning it out will produce more power but if you lean it out too much in the wrong place and BOOM!!!.

Hence the need to have a wideband and experience.. If he's being cautious there's probably a reason for it.
 
GTti

GTti

Member +
My GTti used to fuel 10.5:1 on WOT with stock ECU also. I think it was the safe zone for most of the older generation of turbo charged jap cars.

Pump shouldn't make a difference unless the regulator can't cope with the added drive behind it.
 
Fatman

Fatman

Member +
10.5 is too rich, 11.5 is okay, personally I aim for 12:1. I've run up standard 4E-FTE's on a wideband before and WOT is anywhere from 11.2 - 12.5. For an NA motor you will generally tune more towards 13:1, being under less strain, additional fuel to stave off detonation is not really required.

Short answer is YES your tuner is being overcautious. More fuel doesn't necessarily mean more safety or more power (as you noticed)
 
J

jabran200

Member +
I totallyy agree with fatman on this the tuner is trying to make it extremley safe but isn't that somewhat defeating the point of tuning?

Cars come very rich from factory 10:1 it's not uncommon on turbo jap cars but thats why with a remap and some mild ignition tuning decent power can be had and as well as some saving on fuel consumption beacause you can get the values a little closer to peak power (12:5:1 on turbo cars ) as running rich bogs the car down.
 
S

starlet666

Member +
i personally tune to around 11.5 now at WOT but mine atm is untuned....... totally gay afr running sub 10's and still makes 180hp at 15 psi lol no ignition tuning at all and just added fuel for a bit tuning soon woo

cruise for mine is anywhere between 13.7 and 12.7 depending on what revs it is at

but low revs is high 13s makes it work sweet.... when i change to 85% ethanol im going to have to make a massive change in my tuning ways :( but can make a shit load more power then
 
J

jabran200

Member +
you should try and bring cruise to around 14.5 (i tune leaner lower down) but in general keep it at 14.5 or thereabouts.

12.7 is way too rich for cruising.
 
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