# Tailpipe A/F on the dyno for tuning?

**URL:** https://forums.speedlife.net/t/tailpipe-a-f-on-the-dyno-for-tuning/1816
**Category:** NYSpeed Automotive
**Created:** [August 26, 2005, 10:12am UTC](https://forums.speedlife.net/t/tailpipe-a-f-on-the-dyno-for-tuning/1816 "2005-08-26T10:12:59Z")
**Posts on this page:** 1
**Showing post:** 28

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### Author: ![Jack](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/jack/32/7613_2.png) [@Jack](https://forums.speedlife.net/u/Jack)
#### Post date: [August 30, 2005, 6:31am UTC](https://forums.speedlife.net/t/tailpipe-a-f-on-the-dyno-for-tuning/1816/28 "2005-08-30T06:31:53Z")

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> [@rj-92](#):
>
> If you know the cat Eff’s up the readings, it has to do so in a linear fashion, hence this irregularity is predictable and can be acounted for and a correction factor applied to get and acurate reading… Correct?

I don’t think its that easy. Like Bry said… EGT has a HUGE influence on your cat… so if you do a pull, cool down, do another pull… your EGTs will be different (especially if you made some changes) and now the cat will be warmer/cooler than before and working more/less efficiently

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