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Old 04-09-2003, 11:56 AM   #1
Homemade WRX
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Default How do you tune a turbo using an EGT?

Hi, I was told not to buy an A/F meter because I should buy and use an EGT instead. Can anyone explain why? I'm very interestedin finding out why and I would like to find out which to buy before installing my turbo.
Thanks, Micah
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Old 04-09-2003, 12:08 PM   #2
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You were told wrong. To properly tune you need an A/F ratio. The egt guage is only to monitor your engine to make sure your a/f is close to correct (high temps means your running lean).
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Old 04-09-2003, 12:18 PM   #3
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so I should use both?
or do I only need the A/F?
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Old 04-09-2003, 01:04 PM   #4
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both would be best.

You can use the AFR gauge to give you an idea if you're running rich or lean and you can use the EGT gauge to fine tune your fuel ratios.

Most people here will say to keep it below 1600F. Some people like having a margin of safety and keep it below 1500F.

Running lean = high egt's
Running rich = lower egt's

but running too rich, and your egt's will go back up again.
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Old 04-09-2003, 03:14 PM   #5
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thanks I thought it was like that but wasn't sure. Thanks, Micah
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Old 04-09-2003, 03:27 PM   #6
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I am not sure if this is true but i have been told that A/F gauges arent all that accurate, i think it only gives you a general idea. But that is only what i have heard, could be wrong.

Ben
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Old 04-09-2003, 03:43 PM   #7
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PHAT: A/F guages are generally very accurate. It's the sensors that isn't that good if you use the stock sensors. However if you buy a true wideband and place it after the turbo it will be dead nuts on.
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Old 04-09-2003, 04:36 PM   #8
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how much do wide bands run? and not clear on whether or not you can use S-AFC as a A/F meter. does it have that function?
Thanks, Micah
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Old 04-09-2003, 06:30 PM   #9
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Quote:
Originally posted by mbiker97
You were told wrong. To properly tune you need an A/F ratio. The egt guage is only to monitor your engine to make sure your a/f is close to correct (high temps means your running lean).
And now you are being misled by an inaccurate reply.

1. EGT readings depend on where you are taking the reading

2. EGTs will indicate approximate A/F. Under boost, you tunne to 12:5.1 to 10.5:1, depending on how much boost you really are running

3. NB02 sensors and A/F gauges are absolutely worthless for tuning boost. Don't let anyone convince you otherwise.

4. EGT tuning will get you in the ball park until you can stick a WB02 on there and smooth out your A/F curve accurately.

5. Good rule of thumb presuming you are measuring EGT not that far from exhaust ports, is 1550F by redline in 4th gear. Too high, you are a bit lean. from Redline - XXX RPM. As I said, it gets you in the ball park.

6. Regaring a WB02, the sensors are < $200, but the trick is reading them with some display and/or integrated electronics. WB02 outputs are not the same as NB02, so the ECU is not going to be calibrated for it, and an NB02 calibrated A/F gauge won't work with it either. You can buy something such as a lambdaboy kit pre-fab'd, or build a DIY WB02 kit. Its typically easier and smarter to simply pay $100/hr for some dyno time coupled with WB02 tuning.

- b
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Old 04-10-2003, 01:55 PM   #10
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A true wideband A/F guage would be good to get spot on A/F mixture. I would still get a EGT guage to compliment that. EGT guages are good because it gives you a good idea how much energy is in your exhaust. A low EGT would merrit wasted exhaust energy (too rich) too high would merrit too much and you're probably going to cook something. IMHO EGT is a much better indicator for how well your timing is. Too much timing you can have low EGT's and not enough (too much retard) causes higher EGT's. Hope this helps.

-Erik
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Old 04-10-2003, 07:47 PM   #11
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Default EGT

Quote:
Originally posted by bvl


And now you are being misled by an inaccurate reply.

2. EGTs will indicate approximate A/F. Under boost, you tunne to 12:5.1 to 10.5:1, depending on how much boost you really are running

3. NB02 sensors and A/F gauges are absolutely worthless for tuning boost. Don't let anyone convince you otherwise.

4. EGT tuning will get you in the ball park until you can stick a WB02 on there and smooth out your A/F curve accurately.

5. Good rule of thumb presuming you are measuring EGT not that far from exhaust ports, is 1550F by redline in 4th gear. Too high, you are a bit lean. from Redline - XXX RPM. As I said, it gets you in the ball park.

6. Regaring a WB02, the sensors are < $200, but the trick is reading them with some display and/or integrated electronics. WB02 outputs are not the same as NB02, so the ECU is not going to be calibrated for it, and an NB02 calibrated A/F gauge won't work with it either. You can buy something such as a lambdaboy kit pre-fab'd, or build a DIY WB02 kit. Its typically easier and smarter to simply pay $100/hr for some dyno time coupled with WB02 tuning.

- b
2. True. However, If you run anything leaner than 11.0:1 on 93 octane, buy a spare shortblock.

5. Try not use EGT as an indication of rich vs. lean. It does not work well. EGT is better to understand the efficiency of the engine, i.e. timing indication.

my .02

Steve
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