TT_Vert

iTrader: (12)

On the dyno, i was right around 12.2 or so. To compensate for that I leaned my PE out a bit from 3600RPMS up. My o2 voltages went down so i know it was effective but the LM-1 is showing 11.9 or so. Keep in mind, i have a cat before the WBo2 as i took out my rear o2s and put in the LM-1 sensor and I have richened it up some. If the cats were going to skew air/fuel, wouldnt it showleaner if anything? At idle and cruise I am ALWAYS between 14.6-14.8 so I think this thing is accurate !! I thought cats would skew this for sure..

Here is the PE and the changes I made first off
Stock PE (PE used for dyno 3 weeks ago):

Leaner PE (Leaned out PE to compensate for what i saw on the dyno):


Here is my dyno o2 #s from 3 weeks ago (The first RICHER PE)

Here are the LM-1 #s after about 15 mins of driving today (After PE Leaning above )



Dave

ataylors

iTrader: (2)

you cant run it after the cat, the readings will be worthless

TT_Vert

iTrader: (12)

I know there is a lot of argument as to what cats do to the readings, ive talked to a few tuners now who say they see zero to .1 difference between pre and post cat wide bands so I dunno. Seeing as im at 14.7:1 at idle im somewhat convinced of that. If anything, the readings would be LEANER due to cats, not richer If I had to guess

monodax

How do you calibrate the LM-1 when you get it?

BTL FED

iTrader: (9)

When they took the WB on the dyno where was the sensor, if it was in the tailpipe the exhaust would be cooler than if it was right after the header, that could skew the numbers? how sure are you there sensor was correct, if they ran cars with leaded fuel or it is just an old sensor it can skew the readings. I would take your windband with you to the dyno and use both and compare readings. If there WB is working correctly you should show a little leaner on the street than on the dyno because there is more load on the car.

TT_Vert

iTrader: (12)

the wideband is brand new. THis is the first time ive ever used it. THe WB on the dyno was in fact in the tailpipe as well. The guy tunes lots of cars w/ that wideband so i would hope it would be accurate but who knows. It was PTC (Performance technical center) in elk grove, il. that I had it dyno'd

dave

TT_Vert

iTrader: (12)

the heater calibrates itself evertime you turn it on. You calibrate the o2 by putting it in free air and pressing the calibrate button

Dave

ataylors

iTrader: (2)

the deal with the cat is that it will burn excess fuel in the exhaust. If you are at a steady throttle cruise with a good tune, then there wont be much left over to burn. If you are at full throttle and running rich or setup on the richer side then the cat will come into play a lot more. This could be why it looks great at cruise, but i might still be off at WOT.

slow

iTrader: (7)

is you car Twin Turbo, if so, and its a dynojet, its common for the tune to be off as the dynojets don't load the car as if its driving on the street, so you will see a differnce in the tune

Ryan

jimmyblue

iTrader: (11)

Cats also seem to "smooth" the mixture and the rear
O2s seem to lag real time fronts by a fair bit. I know
you want to believe you can read after the cats but
you have to at least suspect the results of having
some embedded bogosity.

If the cats are indeed combusting stuff that may also
jack your exhaust temps around, too high and the
controller does not have the authority it needs to
stay in cal. A bung immediately downstream of the
cat may get too hot to be right, when the cat's
working overtime.

TT_Vert

iTrader: (12)

the bung is about 8-10" from the cat if I recall on the dynatech X pipe but im not sure. Id think if anything, the air/fuel would err. on the side of lean not rich. Any of you weld in a bung w/ the header in the car (c5)? Id like to put a bung in just to see for sure if it makes any difference.

The car is not Turbo'd. its just a c5 with headers, vararam and gears.
Dave

z-ya

iTrader: (1)

Weld a bung in pre cat, read the instructions they clearly state this. You spent the money now get the results, do it properly and there will be no question of the accuracy on the o2 readings.

TT_Vert

iTrader: (12)

i will but ill have to take the damn header off to get it done which sucks. Then i will compare the two and will bet there is no difference. The thing that baffles me is that all the dyno operators i talk to say cats dont matter. And this is using a tailpipe wide band location. Many tuners tune this way w/ cars w/ cats w/ certainty. I just dont get it.
Dave

deezel

I run my LM-1 in my rear O2 sensor ports (one at a time). I ran it before and after "cleaning" my cats and notice no difference in the readings.

I think if the cats are combusting stuff then they are consuming more oxygen before the rear O2 sensor sees the mixture. This would show richer than a pre-cat reading due to less free oxygen present. Then again, if you have enough combustible stuff left to burn in the cats, you are probably running rich to begin with.

jimmyblue

iTrader: (11)

I put my bung in the I-pipe, back by the door edge
(which seemed like where I would run the cable in,
I wasn't going to make a hard-mounted setup). I
didn't take into account the (possible) issue w/ cats
corrupting the measurement but with mine being
hollow it's no longer an issue. I had the bung welded
on the same time I did my cutout.

I ended last night with 1.15x values (slight rising rate)
in the PE table to get 12.6-12.7:1 wideband readings.
My starting values were slightly fatter than stock
(like 1.25x - 1.26x) that gave me the 11.7ish initial.
Looks like you only actually enriched 3600-4400 and
the rest is leaner. Yet your AFR curve looks to be
still going richer w/ RPM.

You might want to just try putting 1.15 across the board
(make sure your Open Loop Fuel Air table has no values
higher than your PE/RPM so that doesn't mask changes)
and see what you get with the current setup. Bearing in
mind some potential lag in readings, maybe use a higher
gear to run up to redline if you can find the road for it.

TT_Vert

iTrader: (12)

I agree with what you are saying and the logic behind it. Thats why I put it there in the first place. I still would like to put it before the cat just to prove one way or the other. I just think im running way fat right now at WOT. Im gonna lean it out and watch the KR. Im only going to adjust air fuel based on 4th gear as that will be the most load I see and the leanest I'll probally get. I leaned it out some not richened it like i typed (a typo) . Im running way rich and was on the dyno as well. My mistake

Dave