Best suited AFR for performance

[DanMystro]

Hi guys, I've recently installed an Apexi NEO SAFC and an AEM wideband on my 2000 LS400. I was just wanting to know if anyone knows the best AFR for performance for our engines, I've seen on various forums and videos online that in general 11.5 is best rich for torque at WOT and 12.2 is for safe best power at WOT. Currently I'm running 11.5 and it feels great but can only street tune it so don't actually know the true performance, would going leaner to say 12.4 be better?

Thanks.

My supporting mods are custom free(er) flowing exhaust and custom intake.

 

Any advice greatly appreciated.

[Malc]

good lord Dan, welcome to this forum ......  like me I'm thinking most Members here won't have a clue as to what you're trying to say to us 

Malc

[BigBoomer]

Welcome Dan 

I don't know of many on here who are into tuning their LS, but there might be a couple.
If you want that kind of info you may be better off with the US based forum 
https://www.clublexus.com/forums/ls-1st-and-2nd-gen-1990-2000-183/

[DanMystro]

1 hour ago, BigBoomer said:

Welcome Dan 

I don't know of many on here who are into tuning their LS, but there might be a couple.
If you want that kind of info you may be better off with the US based forum 
https://www.clublexus.com/forums/ls-1st-and-2nd-gen-1990-2000-183/

Thank you! 

Yeah haha, I had a sneaky suspicion I'd be better off posting over there, thank you anyway!

[DanMystro]

1 hour ago, Malc said:

good lord Dan, welcome to this forum ......  like me I'm thinking most Members here won't have a clue as to what you're trying to say to us 

Malc

Not to worry, thanks 😁

[steve2006]

IIRC the Lambda or stroichiometric value is the perfect air and fuel ratio for complete combustion of the fuel used which in theory should produce the best efficiency.

Values vary dependent on the fuel used I.e. natural gas, propane and liquid fuels such as petrol but for cars is generally around 12:1 air/fuel ratio.

Heavy reading link 😀

https://en.m.wikipedia.org/wiki/Air–fuel_ratio

Twin turbos Dan, the way to go or an ISF engine.

[DanMystro]

3 minutes ago, steve2006 said:

IIRC the Lambda or stroichiometric value is the perfect air and fuel ratio for complete combustion of the fuel used which in theory should produce the best efficiency.

Values vary dependent on the fuel used I.e. natural gas, propane and liquid fuels such as petrol but for cars is generally around 12:1 air/fuel ratio.

Heavy reading link 😀

https://en.m.wikipedia.org/wiki/Air–fuel_ratio

Twin turbos Dan, the way to go or an ISF engine.

Yeah, I understand the stroichiometric value but once you go open loop after about 80% throttle and start messing with AFRs, 14.7 isn't really ideal power wise, thank you anyways!

Seen most people talk about 12.1 +/- as you say so may have to lean it back up, won't hurt to try.

In the long run I'm looking at supercharging, do love the belt whine. 

[Supafly]

From reading I did a while ago on the subject:

High RPM full throttle 12.2:1 to 13:1 / Your 11.5:1 maybe on the rich side.  It would certainly be worthwhile starting to lean it out bit by bit and see if there is anything left on the table.  Keep a keen ear open for any pre-ignition as things really start to go lean.

Couple of links that I have found useful:

Full throttle (hpacademy.com) - loads of videos and articles posted by these folks

AFR+ Basic Functionality - Understand AFR Values, Wideband O2 Sensors, and Fuel Trim vs. Auto Tune Modes of our Fuel Controller. (afrplus.com)

 

Hope these help.

 

If you find a way of easily adjusting ignition timing please let me know, as it is an area I would like to explore on my UCF20 VVTI 1UZ.

[steve2006]

Long gone are the days of loosening the clamp bolt and turning the distributor.

I bet if I spent enough time in “The shed” the Dwell meter would be rediscovered still boxed 😀

[DanMystro]

On 8/10/2022 at 6:38 PM, Supafly said:

From reading I did a while ago on the subject:

High RPM full throttle 12.2:1 to 13:1 / Your 11.5:1 maybe on the rich side.  It would certainly be worthwhile starting to lean it out bit by bit and see if there is anything left on the table.  Keep a keen ear open for any pre-ignition as things really start to go lean.

Couple of links that I have found useful:

Full throttle (hpacademy.com) - loads of videos and articles posted by these folks

AFR+ Basic Functionality - Understand AFR Values, Wideband O2 Sensors, and Fuel Trim vs. Auto Tune Modes of our Fuel Controller. (afrplus.com)

 

Hope these help.

 

If you find a way of easily adjusting ignition timing please let me know, as it is an area I would like to explore on my UCF20 VVTI 1UZ.

I've yet to find anyone, video or forum that's had the success of adjusting the stock ECU for timing, most people either piggy-back or go full standalone, for the time being I'll stick with AFR tuning etc. I'm still learning and modifying on the go. 

Yeah, I'll most likely lean in back closer to 12.2.

[Supafly]

I have read of people using resistors to 'trick' the signal from the ECT sensor but I wouldn't use this method as there are so many variables that are affected by ECT values.

I've just recently replaced the sensor (only 'while I was there', no running issues whatsoever) and picked up 5mpg with no noticeable change in driveability.

[DanMystro]

19 minutes ago, Supafly said:

I have read of people using resistors to 'trick' the signal from the ECT sensor but I wouldn't use this method as there are so many variables that are affected by ECT values.

I've just recently replaced the sensor (only 'while I was there', no running issues whatsoever) and picked up 5mpg with no noticeable change in driveability.

Is the ECT sensor under the manifold for VVTi models? I already changed my starter, god forbid removing all that again. 😂

Edit: Don't worry just searched, doesn't look that hard to change.

[Supafly]

On 8/22/2022 at 3:43 PM, DanMystro said:

Is the ECT sensor under the manifold for VVTi models? I already changed my starter, god forbid removing all that again. 😂

Edit: Don't worry just searched, doesn't look that hard to change.

Very easy to change, and I think can be done without replacing the coolant.  I took the throttle body off because I was changing the oil control valves too and that made it even easier.

 

Bit late for you now but a tip for anyone researching this in the future.

On removing the inlet manifold... everywhere I read they said that it has to separated into it's top and bottom halves... I didn't do this.  I left the fuel pipe connected as I struggled to disconnect it.  Then I took off all the lower mounting nuts/bolts and lifted the whole thing up and over to the right (facing the front) so it rested upside down.  I then changed the contacts in situ which meant I didn't have to struggle getting the gearbox side bolts out to extract the starter.  So far it's been going well for nearly 40k miles.  See post below for images and some more notes.