Should I be worried?
10 March 2003, 03:35 PM
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Logged my MY99 with K&N element, Dawes (17psi) + samco hoses after replacement of failing o2 sensor.
Did a WOT run from <2000 to redline in third whilst logging all the usual sensors to make sure nothing untoward is happening. All was well apart from between 2000-2200 rpm lamda voltage dips from 0.8ish to <0.2
then back upto 0.9 to the redline.
No blip on the MAF voltage, boost between 0.2-0.4 bar at this point, no knock correction. Is this the lean spot in turbo spool-up which is corrected for in tek remaps, or do I have a problem? Could this lead to detonation?
Any views appreciated
Simon
Did a WOT run from <2000 to redline in third whilst logging all the usual sensors to make sure nothing untoward is happening. All was well apart from between 2000-2200 rpm lamda voltage dips from 0.8ish to <0.2
then back upto 0.9 to the redline.No blip on the MAF voltage, boost between 0.2-0.4 bar at this point, no knock correction. Is this the lean spot in turbo spool-up which is corrected for in tek remaps, or do I have a problem? Could this lead to detonation?
Any views appreciated
Simon
10 March 2003, 05:28 PM
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Most people put more fuel in there, but the lambda voltage is non-linear and not as bad as it looks. If it goes to zero during spool up and then back up again, it means that it was near to 14.7:1 mixture, which is no bad thing at 2000-2200 RPM off boost, well off significant boost anyway. However, you can end up with 18 PSI before 2500 RPM on a TD04 with a Dawes and decat, so it could do with richening up a bit.
Try plotting boost against lambda voltage. You will see it squiggly
up until say 5 PSI after which it should gradually richen.
Extra timing and fuelling during spool up can help torque, but as I say, a narrowband trace going to zero makes it look a lot leaner than it is. You can only really use the lambda as a guide once it goes over about 0.75 V after which it should smoothly increase to 0.87 V + on boost (usually over 0.90 V).
Try plotting boost against lambda voltage. You will see it squiggly
up until say 5 PSI after which it should gradually richen.Extra timing and fuelling during spool up can help torque, but as I say, a narrowband trace going to zero makes it look a lot leaner than it is. You can only really use the lambda as a guide once it goes over about 0.75 V after which it should smoothly increase to 0.87 V + on boost (usually over 0.90 V).
03 October 2003, 08:30 PM
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Cheers John 
I've done as you advised, not so much squiggly as a valley between 0.15-0.33 bar with a lowest lambda of 0.105. Lambda crests 0.87 at 0.5 bar and is >0.9 over 0.75 bar.
I'm getting a 3 inch exhaust with sports cat DP in the next couple of weeks, I suppose this may accentuate this further with better spool-up. May be emailing you for a tek2.5 following this
On a different note happy to see peak torque increase by 30lbft and power by 20bhp with Dawes c/w OEM boost control on Road Dyno. And plenty more "area under curve"
Simon
[Edited by SiHethers - 3/10/2003 8:31:23 PM]
I've done as you advised, not so much squiggly as a valley between 0.15-0.33 bar with a lowest lambda of 0.105. Lambda crests 0.87 at 0.5 bar and is >0.9 over 0.75 bar.
I'm getting a 3 inch exhaust with sports cat DP in the next couple of weeks, I suppose this may accentuate this further with better spool-up. May be emailing you for a tek2.5 following this
On a different note happy to see peak torque increase by 30lbft and power by 20bhp with Dawes c/w OEM boost control on Road Dyno. And plenty more "area under curve"
Simon
[Edited by SiHethers - 3/10/2003 8:31:23 PM]
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