I'm learning to tune and i just got a wideband since I'm getting ready to boost my sock turbo to 11 psi.

What is a good air fuel ratio to aim for for idle and when I'm boosting? Also what af should I avoid so I don't detonate?

I searched a bit but i didn't find much so if anyone has a link to i would appreciate that too! Thanks.

 

anything below a 10 is perfect and normal

 

I'd say mid 10's to mid 11's. Start worrying at 11.5+. Idle is like 12-14s.

 

Ok cool. My idle was at 8.7. Now its at low 12s. That made a huge difference.

 

Stock turbo?

13.5 at idle.

14.5 or so under light load out of closed loop.

Closed loop to 15.0 or there abouts.

Under moderate throttle, 13.5 out of boost.

At 0", go down to 12.5 and hold that number until about 4-5 PSI. Then go down to 12 until about 7-8 PSI. Now taper down to 11.5 to 10 PSI an run 11 exactly after that. Once you hit the 15 PSI area, 10.5.

Of course, without knowing how the car is configured, it's all a guess. And timing is rather important...

 

Arron,
Why would you want to run run a more lean mixture during idle than under light load..? Not saying you're wrong, but I am just curious.

OP,
Here the basic foundation I used to tune my Eclipse (yes, I know completely differnent engine, but AFR's should still be about the same).
Idle: 14.5 - 15
Light to moderate load (out of boost): 14 - 14.5
Heavy Load (out of boost): 13.5
0 PSI - 6 PSI: 12
7 PSI - 10 PSI: 11.5
11 PSI - 15 PSI: 11
16 PSI - 25 PSI: 10.5
And of course you will also need to adjust timing according. A good starting point is to retard 1* of timing for every 5 PSI of boost. Without having both parameters set correctly, you can cause detnation and kiss you engine good bye. Remember, these are just starting points and every engine is different requiring different tunes.

 

good topic. may i suggest adding info for us N/A guys? im gonna be getting a wideband and maybe rtek in the future. i know some about this stuff but have never actually tuned anything before. all my info comes from reading. not a good substitute for real life.

 

Ill get you some info in the next week or so. I have an RTEK that just shipped and have a wideband in my NA. I'll have EGT probably next week as well before I start tuning it.

For an NA you want to shoot for high 12s to very low 13s for AFR. I believe the sock on my fuel pump is clogged so I need to take a look at that this weekend.

 

He is saying run idle RICHER than when under load, not leaner. If you run the idle mixture above 14:1 it the car starts to miss and idle roughly. Between 13.1 and 13.6 AFR it will idle smoothly.

 

Yeah, I know I read it again... I must have been having a brain fart.

Also, I've never run a anything richer than a 14 during idle, I'll have to check out that mixture sometime...

 

what's the point of getting wideband when u only have rtek? You can't tune anything anyway.

 

^ Rtek 2.1's allow you to adjust the factory fuel and timing maps. This is a 2.1 right?

Idle AFR depends on porting and timing advance. I have found that streetported motors need a bit richer idle to be stable. Btw, this is without an air pump. The air pump will make your idle AFR read way way leaner.

It's a bit more complicated on this application. If he is using an Rtek 2.1 he really should convert to rpm vs boost timing maps as opposed to airflow based timing maps. And then you have to tune trailing split.

 

RTEK is fully adjustable as they only have the 2.0 version for NA cars.

 

So far AAron is the only one in this thread even REMOTELY on track with AFRs although I really dont think 10.5 AFRs are necessary and I have never used anything lower then 11:3 even on pump gas in excess of 17 PSI. OF course 10.5 will guarantee no problems with pre-ignition you could run into ignition break up problems.

Trailing split is something best left to tuning on a dyno since most engines will react differently to different splits.

 

i also would like to see the information for Na please and thanks

 

NAs are about the same.

13.5 at idle.

14.5 or so under light load out of closed loop.

Closed loop to 15.0 or there abouts.

Under moderate throttle, 13.5 or so.

Under WOT, it does depend a lot. With an NA you have the option of not needing richer mixtures to prevent detonation. I would not recommend going leaner then 13.5 or so under WOT. NAs will like anywhere from 12.5 to 14.0 under WOT and where you run it will depend on where it makes power.

AFR tuning is not a hard and fast science. It depends on a lot of things.

 

i could look this up, but please save me time, can u simply explain closed loop?

 

closed loop, when the car is at cruise speed.

 

but above or below what rpm or speed... or throttle position.

 

the FC is in closed loop between 1200ish rpm and 3500 rpm under approximately 30% throttle.

closed loop = the ecu is using the o2 sensor to get the mixture to 14.7:1

also a STOCK FC injects air pump air into the exhaust under 2500ish rpm (its throttle position and rpm), so a wideband will read 16-18:1.

havent looked at an s4 yet, but if you have a stock properly functioning S5 Na it runs these afr's

idle-1100ish rpm: 16-18:1

closed loop, 1200-3500 rpm: 14.7:1

WOT @3500 its mid 12's gradually richening up to about 11:1 around 5500

 

ah ok, well my air pump is only really running the vdi that open at 5500. i have a rb true duel exhaust so the airpump cant get air in there and my port actuators are blocked and ports wired open because the actuators are too stiff to open via the pump.

 

Did any N/A guys here tune since posting? I'm about to tune my '89 N/A with the an RTEK.

 

go for mid 13s, low 13 at pk tq...
have gotten as high as 13.7ish and 13.5 in NA... it was fine... doubt anything bad can really happen unless you **** up big

 

Yep, I did mine. Low 13 AFRs are where you want to be at full load. You can taper that up slightly as you reduce load.

 

The rotary really like to run rich huh.... I know a lot about tuning piston engines.... but damn those numbers looks rich all over the place.... 8.5 at idle stock OMG, no wonder they burn your eyes standing behind one....