I was having a discussion with a friend that has a LGT and we were talking about my lean condition on the top end. His understanding as well as mine was a 12.5:1 ratio isn't horrible for FI. We were also debating between how accurate a tailpipe sniffer reading and an actual O2 sensor being installed was. When my Prelude was tuned by Jeff Evans he swapped out my O2 for a wideband.

So does anyone know how accurate a tailpipe version is against an O2 sensor in a bung? What would need to be done to get AFR done via an O2 sensor for our cars? Would another O2 bung need to be welded in first? If so where? Lastly does anyone know a NY/NJ shop that would run AFR that way instead of via the tailpipe sniffer?

Thanks for any help you can offer!

 

Alot of the aftermarket headers come with an additoinal O2 bung welded in already. You can also use a Wideband O2 in the stock location as long as it is one that functions as both wideband and narrow. You would have to run the wideband signal to a gauge and splice the narrow into your wiring harness for the ecu.

 

With a true AFR of 12.5:1 it does not leave you much margin of error. You really wont see much of a substantial power gain running your s2k at 11.8-12.0:1 versus 12.5, thus why I dont recommend running a street car at 12.5:1 under full boost.

Ive done some testing between some various tail pipe 'sniffers' and while some of them can be very accurate, on lower engine speeds there is a small delay until the correct reading if the o2 is located at the rear of the exhaust. It also depends on the wideband you are using. some react different than others. on my dyno dynamics it uses a very nice autronic wideband, and the way my dyno loads the car before the run, there really isnt a delay even if i use a sniffer out the back.

The dynojet wideband sniffer is amongst the worst compared to most. their sniffer is basically garbage, you always have to service them, IMO most people dont end up relying on them because they end up malfunctioning. DJ's wideband sensors do not last long either.

I always recommend any boosted guys buying their own wideband, now days they arent expensive. Its a great tool to have.

Good luck,

Mase

 

i had my car at ISP yesterday for dyno tuning after installing the sc setup. they thought their wideband in the tailpipe was incorrect as well because Peter added 24% more fuel above 6krpm and the AFR went up by only .2

but there was no way for them to put the wideband in the stock o2 sensor location unless they welded another bung on my test pipe they said.

 

So what are you going to do now?

BTW what SC kit, what other add-ons (if any) and what was your AFR before and after?

 

The thing I'm worried about is buying something like an emanage and then having it installed and tuned when in reality the car might have been in the 11.5-12.0 range but the tailpipe sniffer isnt as accurate. The only thing I'm looking for is saftey and minimal headaches. After reading some of the posts regarding the emanage it seems some people have weird issues they cant track down. There's two other ways I can go, find someplace with a good wideband that installs in the OEM O2 bung and check it again and if it is lean turn up the FPR a bit to try to correct that. The second way would be to spend even more money and just go the AEM EMS route and have Jeff Evans tune it since I trust him. Basically I'm looking at $300 ---> $800-1000 ---> $2200. Obviously they're all worth it vs the cost of a blown motor but again to spend that kind of money when its not necassary seems senseless.

 

well my setup had a bunch of other random problems, that were all due to my own carelessness. so i don't know if a problem with the wideband was really what was causing issues with tuning.

they should finish up today and let me know how it went.

 

Ok looks like my setup was running stock plugs (NGK PFR7G - 11S), from what I understand these are "hotter" then recommended for a FI applicaiton. I know I should search for this answer but someone help me, could and would this cause detonation on the top end? Also could they affect AFR? I'm assuming if I'm getting detonation then the resulting exhaust wouldnt be what the AF meter is expecting and?

 

it might be detonation, but if your under boost that can very very quickly destroy the motor. What's was more likely is that its a misfire, due to the temperature of the plugs, condition, or gap size! Get the right plug, weld on a bung onto your test pipe, and get a wideband in there for peace of mind! It won't be more than 100 dollars to weld on a bung, probably alot less!

 

That sounds great and all but do any of these map AFR so I can check it later? Most of them seem like real time gauges, kind of hard to be running to 8k and checking an AFR gauge at the same time. Once the car is straight I'm not going to mess with it anymore so that's all I'm looking to do, get it right.