weird AF reading before VTEC

alblude · Post by **alblude** » Tue Dec 04, 2007 8:38 am

hello,

I'm having a weird issue where intermittenly the SManager logs flat AF values (12:1) for some period of time before deciding to actually fluncuate. after taking some datalogs it looks like this behavior happens before VTEC kicks in. Attaching the calibration and a couple of datalogs showing the issue. VTEC kicks in at 3000 RPM

Post by **Hondata** » Tue Dec 04, 2007 10:05 am

I suggest removing R136 and R138 (for US ECUs). There resistors bias the ELD input and some widebands don't output enough current to give an accurate voltage reading in the ECU.

alblude · Post by **alblude** » Tue Dec 04, 2007 1:25 pm

Hondata wrote:I suggest removing R136 and R138 (for US ECUs). There resistors bias the ELD input and some widebands don't output enough current to give an accurate voltage reading in the ECU.

OK will do. I believe I checked for the appropriate resistors to be removed when I socketed the ECU but I may have missed at least one

alblude · Post by **alblude** » Wed Dec 12, 2007 12:17 am

Disconnecting R136 and R138 resolved the issue. My AF was richer than 12:1 and because of those resistors the voltage from the PLX could never go lower then 1V. So for any AF values below 12:1 it would just record 12:1 resulting in the flat line.

Do those resistors affect anything else?

Post by **Hondata** » Wed Dec 12, 2007 10:00 am

Thanks for the feedback. Removing the resistors will not affect anything else.

mike93hatch · Post by **mike93hatch** » Wed Dec 12, 2007 9:54 pm

ive always had the same problem as he did.. except mine would never go lower than 11.8 and would just freeze there. i had to make the voltage offset about 0.25 to get it halfway close to the correct a/f reading. im using the D10 ELD for it as well.

how do you go about removing the R136 and R138 resistors? can you just cut them off of the board ?

alblude · Post by **alblude** » Thu Dec 13, 2007 1:51 am

you shouldn't adjust the offset voltage unless the readings are off between the Wideband and Hondata.

I only cut one side of each resistor. it's pretty tight in there so I had to get some mini diagonal cutting pliers (these ones http://www.sears.com/shc/s/p_10153_1260 ... ini+pliers)

Once i cut off those resistors the offset was only -0.02V instead of -0.23V.

happy tuning!

hiperformance · Post by **hiperformance** » Thu Dec 13, 2007 1:23 pm

mike93hatch wrote:ive always had the same problem as he did.. except mine would never go lower than 11.8 and would just freeze there. i had to make the voltage offset about 0.25 to get it halfway close to the correct a/f reading. im using the D10 ELD for it as well.

I was using the PLX M-300. My A/F on the data log would also get stuck at 11.8, with the help of spunkster, I determined that it was not the ECU or the software, also no difference occurred when we removed R136 & R138, so we re-soldered them back. What it turned out to be was the PLX was out putting an extra 0.9v, sent it back to PLX, they determined the unit had a bad ground. So if your using a PLX, it could be the PLX causing your problems.

Here is our discussion. http://hondata.net/forum/viewtopic.php?t=6809

mike93hatch · Post by **mike93hatch** » Thu Dec 13, 2007 8:50 pm

thanks for the info guys... yea my plx m300 is off on hondata when comparing to the wideband display so thats why i used the offset voltage but that doesnt fix it getting stuck at 11.8..

so you think it wouldnt be worth it to cut those resistors and try it?

when youre talking about a bad ground are you talking about inside the plx controller or the actual external ground wire for the unit?

so it was just a bad plx unit? that sucks.. i see this m300 + hondata problem all the time. plx just sucks i guess :(

THANKS

hiperformance · Post by **hiperformance** » Sat Dec 15, 2007 2:45 am

mike93hatch wrote:thanks for the info guys... yea my plx m300 is off on hondata when comparing to the wideband display so thats why i used the offset voltage but that doesnt fix it getting stuck at 11.8..

so you think it wouldnt be worth it to cut those resistors and try it?

when youre talking about a bad ground are you talking about inside the plx controller or the actual external ground wire for the unit?

so it was just a bad plx unit? that sucks.. i see this m300 + hondata problem all the time. plx just sucks i guess :(

THANKS

The PLX's are good and economical but some times you get a bunk one or two. like any mass produced item. While my M-300 was being fixed, my R-300 screen burned out, they said it had bad firm ware. Got the M-300 back, it lasted 1 day and broke again. Through all this, PLX has been very good at standing behind their product and fixing them with out problem. I like them, when they work. The last time my M-300 broke, it was on the dyno, I had to use the dyno wide band to finish my tune. that worked fine, just took a little longer, sense i could not data log the a/f's.

You could cut the resistors, doesn't hurt anything if you do. you never know, it might solve your problem. It didn't fix my problem, so i soldered them back. I used finger nail cutters to clip one side and bend it up. The bad ground I am talking about was internal, in side the PLX box.

Good luck