65nassau

I'm going to get my car dyno tuned and both the guys in town say they need to 'weld' in (then plug) a 7/8" fitting to my exhaust.

I hate to do this, cause I have nice ceramic headers and a beautiful new stainless exhaust system.

Does this sound normal?

Any alternatives anyone can think off?

Vette-66

Sounds like they want to add an O2 (or some other) sensor.
Did they tell you the reason they wanted to add it or what they could not do if they did not install it?

Chuck

olescarb

Innovate Motorsports has a probe that you can place in the exhaust tailpipe that you can use to put a wide band o2 sensor in. it is a great tool that can be used to check the air/fuel mixture with a wide-band sensor based air/fuel meter and you do not have to drill any holes in the exhaust system. i like the Innovate Motorsports products and i also use them

L79vette

The welded-in bung is supposed to give you more accurate readings, but I doubt it matters for tuning a street car. Probably not even a race car. The kind that clips on and goes up the pipe should be fine.

65nassau

The probe is definitely for an O2 sensor for air - fuel ratio.

Has ANYONE had Dyno tuning done that can answer this question ???

I don't really want to go buy a sensor to take to the dyno shop, I'm wondering if anyone who has had a dyno shop tune their car suggest or use an alternate mehod other than the 7/8" hole/fitting to measure this...

I need your help as I want the car Dyno tuned and need a good solid alternative before he cuts into my beautiful new exhaust system!

6T5C2

When I had my truck dynoed they clamped a sensor on my exhaust tip and that was MORE than enough to get the correct air/fuel ratio. The weld in bung is more for the do it yourselfer that is planning on data logging and tweaking the computer program instead of having it done professionally.

I wouldn't let them weld the bung on for one dyno tune session.

6T5RUSH

65nassau,

Know what you mean/concerned about invading your new exhaust system. But, I had a plug put in my aluminized exhaust manifold and it was done cleanly. The appearance is acceptable to me. Your call.

Click on My Corvette Photos for a shot of it (had the Sweet Thunders installed at the same time by the exhaust shop).

Definitely allows the tuner to zero in on the air fuel mixture through your powerband and correct a lean or fat condition by jet size changes.

Regards,

Jim

Brutal64

I can't believe a dyno shop wouldn't have a tailpipe probe!? Maybe they're just trying to get some more cash out of you. If you don't let them weld in a bung and they don't have a tailpipe sensor, don't even bother going. The O2 sensor is what makes dyno tuning worthwhile.

Allcoupedup

Some high tech shops weld in a bung for every cylinder so you can do cylinder and fuel distribution tuning. No way would I let them modify your headers.
brian

65nassau

Update -

I just talked to the Dyno guy and he said the sensor works off heat and oxygen combined (the hotter the sensor the better) and the closer to the exhaust port the better results. 'Tailpipe units do not get the best results'.

He also said the fitting sticks up about 1/8" and can be tucked way up out of sight. The fitting is about the size of a quarter.

I asked him if he can get the fitting in stainless and not regular steel and he said he will see. If I am going to pay for dyno time 200-300 bucks, i want the best results possible, so I guess I will go with stainless fitting tucked out of sight.

Both (there only 2 in Atlanta) Dyno guys in town have the EXACT same story.

olescarb

do what you want but i see no problem with a tailpipe sensor (such as the Innovate Motorsports unit) unless you are doing race tuning at the NASCAR or NHRA level.

FYI the term oxygen or o2 sensor is very misleading because the sensor looks at and analyzes the "unburnt combustables" in the exhaust, so a wide band o2 sensor does not really look at the oxygen in the exhaust.

L79vette

I've had mine done with a tailpipe sensor. I can't compare to the bung since I have not had it done both ways. But...
The claim about the sensor working on heat is pure BS. Narrow bands do work that way, but not wideband.
Find another shop.