# Tailpipe A/F on the dyno for tuning? **URL:** \ **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:** 20\ **Page:** 1
**Author:** ![walter](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/walter/32/7202_2.png) [@walter](https://forums.speedlife.net/u/walter)\ **Post date:** [August 26, 2005, 10:12am UTC](https://forums.speedlife.net/t/tailpipe-a-f-on-the-dyno-for-tuning/1816/1 "2005-08-26T10:12:59Z")
Obviously a wideband is best. But will a tail pipe sniffer give you a decent ball park on the dyno? ---
**Author:** ![Nikuk](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/nikuk/32/7254_2.png) [@Nikuk](https://forums.speedlife.net/u/Nikuk)\ **Post date:** [August 26, 2005, 10:39am UTC](https://forums.speedlife.net/t/tailpipe-a-f-on-the-dyno-for-tuning/1816/2 "2005-08-26T10:39:11Z")
is it a straight pipe exhuast? ---
**Author:** ![walter](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/walter/32/7202_2.png) [@walter](https://forums.speedlife.net/u/walter)\ **Post date:** [August 26, 2005, 10:42am UTC](https://forums.speedlife.net/t/tailpipe-a-f-on-the-dyno-for-tuning/1816/3 "2005-08-26T10:42:01Z")
No ---
**Author:** ![Nikuk](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/nikuk/32/7254_2.png) [@Nikuk](https://forums.speedlife.net/u/Nikuk)\ **Post date:** [August 26, 2005, 10:45am UTC](https://forums.speedlife.net/t/tailpipe-a-f-on-the-dyno-for-tuning/1816/4 "2005-08-26T10:45:40Z")
then I would think that’s Your answer. I’m thinking that any obstructions (cat & muffffffler) would change the nature of the exhaust. Maybe not much, but enough that it’d be a waste of a dyno run. But, again, I don’t know shit. -Nick ---
**Author:** ![Boomin99GT](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/boomin99gt/32/7306_2.png) [@Boomin99GT](https://forums.speedlife.net/u/Boomin99GT)\ **Post date:** [August 26, 2005, 10:49am UTC](https://forums.speedlife.net/t/tailpipe-a-f-on-the-dyno-for-tuning/1816/5 "2005-08-26T10:49:44Z")
Yeah, tail pipe sniffer will tell you your CO2 percentage and stuff but isn’t as fast as a Wideband and it’d be way too hard to tune anything. ---
**Author:** ![walter](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/walter/32/7202_2.png) [@walter](https://forums.speedlife.net/u/walter)\ **Post date:** [August 26, 2005, 10:52am UTC](https://forums.speedlife.net/t/tailpipe-a-f-on-the-dyno-for-tuning/1816/6 "2005-08-26T10:52:05Z")
Not for tuning, just to get an idea of where things are over the run. ---
**Author:** ![Boomin99GT](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/boomin99gt/32/7306_2.png) [@Boomin99GT](https://forums.speedlife.net/u/Boomin99GT)\ **Post date:** [August 26, 2005, 10:57am UTC](https://forums.speedlife.net/t/tailpipe-a-f-on-the-dyno-for-tuning/1816/7 "2005-08-26T10:57:03Z")
Yeah I hear ya but usually you need to hold the gas @ a certain RPM for a few seconds before the meter can calculate whats going on, they’re not that fast and on the dyno you can’t hold it @ a certain RPM. ---
**Author:** ![walter](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/walter/32/7202_2.png) [@walter](https://forums.speedlife.net/u/walter)\ **Post date:** [August 26, 2005, 11:00am UTC](https://forums.speedlife.net/t/tailpipe-a-f-on-the-dyno-for-tuning/1816/8 "2005-08-26T11:00:29Z")
Just curious why many dyno places offer them if they aren’t really usable :shrug: ---
**Author:** ![jay\_g](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/jay_g/32/111288_2.png) [@jay\_g](https://forums.speedlife.net/u/jay_g)\ **Post date:** [August 26, 2005, 11:33am UTC](https://forums.speedlife.net/t/tailpipe-a-f-on-the-dyno-for-tuning/1816/9 "2005-08-26T11:33:31Z")
Normaly you want to have the wideband before the cat for the most acc. reading. Now This is some info that I read from a wideband builder/distributer. Granted this isnt directly to your question but it is about having a wideband after the cat. > It is ok to mount the sensor after the cat. The AFR readings should be the same but you may experience a little bit of latency (lag) between applying the throttle and a change in AFR readings. (maybe 200 ms rather than 100 ms I’m guessing). > > The instructions recommend 24" away from the engine or turbo because of heat issues. If you can confirm that your EGT is no higher than 850 C at any time you can install it precat. Temperatures over 850 C may cause sensor failure so proceed with caution. ---
**Author:** ![JoesTypeS](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/joestypes/32/7190_2.png) [@JoesTypeS](https://forums.speedlife.net/u/JoesTypeS)\ **Post date:** [August 26, 2005, 11:46am UTC](https://forums.speedlife.net/t/tailpipe-a-f-on-the-dyno-for-tuning/1816/10 "2005-08-26T11:46:37Z")
> [@walter](#): > > Just curious why many dyno places offer them if they aren’t really usable :shrug: Most of them offer wideband tail pipe sniffers… ---
**Author:** ![walter](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/walter/32/7202_2.png) [@walter](https://forums.speedlife.net/u/walter)\ **Post date:** [August 26, 2005, 11:51am UTC](https://forums.speedlife.net/t/tailpipe-a-f-on-the-dyno-for-tuning/1816/11 "2005-08-26T11:51:40Z")
Ok, so then… wideband tail pipe sniffers :shrug: Sounds like the lag will be minimal, and should work just fine. ---
**Author:** ![Zer0DazE](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/zer0daze/32/7624_2.png) [@Zer0DazE](https://forums.speedlife.net/u/Zer0DazE)\ **Post date:** [August 26, 2005, 9:17pm UTC](https://forums.speedlife.net/t/tailpipe-a-f-on-the-dyno-for-tuning/1816/12 "2005-08-26T21:17:10Z")
if there is a cat in place it will fuck up the readings ---
**Author:** ![HotRodKid](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/hotrodkid/32/7609_2.png) [@HotRodKid](https://forums.speedlife.net/u/HotRodKid)\ **Post date:** [August 26, 2005, 9:30pm UTC](https://forums.speedlife.net/t/tailpipe-a-f-on-the-dyno-for-tuning/1816/13 "2005-08-26T21:30:02Z")
if cats dont change the a/f reading, then why would obd2 cars have a o2 after one of the cats ? cats change the a/f ratio to the exhaust emission sniffers go in the tailpipe, 02 sensors belong in the downpipe / testpipe ---
**Author:** ![Zer0DazE](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/zer0daze/32/7624_2.png) [@Zer0DazE](https://forums.speedlife.net/u/Zer0DazE)\ **Post date:** [August 26, 2005, 9:40pm UTC](https://forums.speedlife.net/t/tailpipe-a-f-on-the-dyno-for-tuning/1816/14 "2005-08-26T21:40:48Z")
> [@Zer0DazE](#): > > if there is a cat in place it will fuck up the readings im pretty sure thats what i said ---
**Author:** ![HotRodKid](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/hotrodkid/32/7609_2.png) [@HotRodKid](https://forums.speedlife.net/u/HotRodKid)\ **Post date:** [August 26, 2005, 9:57pm UTC](https://forums.speedlife.net/t/tailpipe-a-f-on-the-dyno-for-tuning/1816/15 "2005-08-26T21:57:08Z")
i didnt see your post , musta skipped it on accident ---
**Author:** ![Zer0DazE](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/zer0daze/32/7624_2.png) [@Zer0DazE](https://forums.speedlife.net/u/Zer0DazE)\ **Post date:** [August 26, 2005, 9:58pm UTC](https://forums.speedlife.net/t/tailpipe-a-f-on-the-dyno-for-tuning/1816/16 "2005-08-26T21:58:10Z")
uuuuuhhhhhuuuuuuhh i see how it is 🙂 ---
**Author:** ![HotRodKid](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/hotrodkid/32/7609_2.png) [@HotRodKid](https://forums.speedlife.net/u/HotRodKid)\ **Post date:** [August 26, 2005, 10:01pm UTC](https://forums.speedlife.net/t/tailpipe-a-f-on-the-dyno-for-tuning/1816/17 "2005-08-26T22:01:36Z")
fine … then how about this - your sacf settings didnt work cause the eclipse needs an FPR, so ive decided that everything you say is wrong, even if i repeat after you your wrong and im right kk ? thanks for p[layin 🙂 ---
**Author:** ![Zer0DazE](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/zer0daze/32/7624_2.png) [@Zer0DazE](https://forums.speedlife.net/u/Zer0DazE)\ **Post date:** [August 26, 2005, 10:06pm UTC](https://forums.speedlife.net/t/tailpipe-a-f-on-the-dyno-for-tuning/1816/18 "2005-08-26T22:06:50Z")
lol how low did you end up having to go with the fuel pressure anyways? ---
**Author:** ![Viper966](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/viper966/32/7268_2.png) [@Viper966](https://forums.speedlife.net/u/Viper966)\ **Post date:** [August 28, 2005, 1:20pm UTC](https://forums.speedlife.net/t/tailpipe-a-f-on-the-dyno-for-tuning/1816/19 "2005-08-28T13:20:24Z")
last time i was on the dyno my aem in the exhaust and the tailpipe wideband were identical readings ---
**Author:** ![rj-92](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/rj-92/32/7310_2.png) [@rj-92](https://forums.speedlife.net/u/rj-92)\ **Post date:** [August 28, 2005, 1:41pm UTC](https://forums.speedlife.net/t/tailpipe-a-f-on-the-dyno-for-tuning/1816/20 "2005-08-28T13:41:47Z")
> [@Viper966](#): > > last time i was on the dyno my aem in the exhaust and the tailpipe wideband were identical readings Are you running a cat? [Next page](https://forums.speedlife.net/t/tailpipe-a-f-on-the-dyno-for-tuning/1816.md?page=2)