morris

iTrader: (2)

Help me out here. If the AF is at 13-14 under partial throttle or even hard acceleration is this a bad thing if under WOT the AF drops to 12 is that okay? We are talking a turboed car here of course.

HI98GS

It could be that the car is running too lean. Normal is about 12.7 (stoichometric value). You could use the European measurement of Lambda. (a value of 1 is normal) In general if the number is higher then there is more air to fuel which means the engine is running leaner.
You can't only go by the lambda or AF ratio. Some engines like to run lean and others don't. If you don't hear any pinging, then I am sure your ok

morris

iTrader: (2)

nope no knocking or pinging, that I can hear assuming that I am listening for the right sounds. I guess I may just be paranoid. We are talking about a 1uz.

I'm trying to determine if it is running to lean or if I should really only concerned about the ratio under full throttle.

Dx3

iTrader: (13)

Morris,


For my car, the more throttle I gave it - the further my AF fell. To begin with - mine was waay up. It ended up around 13 or so I believe under WOT.

What fuel management are you using???

Jonny

morris

iTrader: (2)

Well I just went out for a test drive, the mix is definitley off now. Even under WOT it is 13 and 14. I will have to have it adjusted hopefully tomorrow before my trip to Jax. Other wise I will have to take a differnet car I thikn. For now I am using the SAFC2

LMSguy

Morris, that sounds perfect to me.Under part throttle it SHOULD be a tad leaner,Then under boost you are getting more fuel which is 100% correct.
Your being paranoid.If your really worried about it post the dyno sheet and let us take a look at th A/F all the way through the RPM band.

morris

iTrader: (2)

I dont have a dyno sheet right now, but now I notice that under WOT it is still at 13 or 14, it used to settle out between 11.8 and 12.4. So something has changed, or my in car wideband is hosed. I'll have them hook up there wideband and verify whether mine is hosed or not.

LMSguy

At WOT 11.8 - 12.4 is perfect.
13-14 at WOT is too lean.
A bad tank of gas could cause detonation which could alter the A/F, just a thought.

What O2 Sensor are you using, and how long has it been in the car?
Have you been using any 100 octane gas?Most of which is leaded and most O2s dont like lead.

aleks

I agree, From my experience (non lexus) you want around 12 at WOT. You want a safe rich mixture to help with cooling and pre detonation. Lean will make more power but rich is safer. Stoich should be 14.7.

morris

iTrader: (2)

thanks guys I am using an AEM wideband it has been in for about 2 or 3k miles. But I just started using it with the Turbo.
I use 93 octane gas. just filled up today as a matter of fact.

What is stoich and how is it relevant? yea I know I should probably know this.

LMSguy

Thats the ideal ratio for gasoline.
Thats close for a N/A Application but definately too lean for a turbo application.And almost all tuners now tune a bit richer than 14.7 even on N/A engines

morris

iTrader: (2)

thanks, I knew that a lot of guys tune for about 12 or so but I didnt know it had a name.

LMSguy

When you get a little time do some research.

http://www.mpcfaculty.net/mark_bisho...ichiometry.htm

morris

iTrader: (2)

Thanks I'll check it out I just got back from the shop we tried to richen it up some but we really didnt get the best of results. The thought is that the fuel pump needs to be replaced so I will try to get that done next week. In the mean time it will sit in the garage

Thanks for all your help

I6turbo

iTrader: (1)

Assuming this is a 2JZ turbo at ~8.5:1 compression ratio, you generally want the AFR to be in the 11.0-11.8:1 range under higher boost on pump gas (probably staying in the 11.0 range if you're running > 14 PSI on pump gas). There's very little power to be gained by going leaner than about 12:1 under boost, and there is a higher likelihood of knock as you go beyond 12:1 AFR on pump gas at those boost levels. If you're on the stock ECU, the AFR will constantly (once or twice per second) flip back and forth between about 15.2 and 14.2:1 during steady-state cruise. If it's constantly running lower or higher than that range, then something is probably wrong. (This is the case for the 2JZ-GTE ECU, and I assume the same is the case for the GE ECU.)

When you roll into the throttle (go WOT) you'd ideally want the AFR to stay in the low 14s or 13s until boost begins to come on, then trail down to the upper 11s by the time boost hits ~10 PSI and beyond. However, you won't really be able to control that, and some injector/ECU/fuel controller/etc. setups happen to do a more ideal job than others. For example, changing VPC chips in my car (switching between the B, C, and D chips) has a big effect on this transitional AFR, and consequently on turbo spool and engine responsiveness during this period.

I'd be happy to take a look at it if you like while you're in Jax. Give me a call on my cell at 904-415-1950 if you're interested in meeting up. I have a lot of experience with widebands. I was pretty much the guy who got the whole FJO/built-in wideband thing started about 4 years ago by getting it going in the Supra community with my old website/business, www.widebando2.com , which I've since sold.