Data Log - Looks to be a problem

Did a WOT run and datalogged it. Here is a chart below. Look at Bank1 vs. Bank2. I talked briefly with Van about this. Bank1 around 0.789 is correct during the big WOT's...but look how my bank 2 will shoot up to 1.6 during the same time. Van said I should replace all my spark plugs and gap at 0.032. They are brand new plugs, but I guess there could be a bad one. He said do that first, if not that, then it could be a vacuum leak or something and I'd have to do a smoke test.

I need a tutorial on this. Is bank 1 and bank 2 referring to the 4 per side on the engine?

Go here to view it: http://www.corepuncher.com/Parts/log1.png

As you can see, bank1 afr drops down low during big WOT / RPM ramps ups...and rises spikes up when I am shifting (and letting off gas). But for Bank 2, it spikes up IN THE MIDDLE of the WOTS...that is the problem from what I can tell.

You need to get it on a Dyno.

+1 for a dyno. Need to check the tune/afr on a loaded dyno with an accurate Air Fuel sensor. You can also datalog during the dyno for your benefit

I would be open to doing this but I don't want to drive to Tulsa to do it. I'll have to check around the OKC area, surely someone has one.

If you do want to stay local, then make sure the dyno you are using has an ACCURATE A/F sensor. A lot of Dynos just stick a sniffer in the tailpipe and/or are using a junky meter, which is FAR from accurate. It can be a full point off...then your adjusting the tune off of an inaccurate reading and possibly risking the motor.

Kurtis has an AFM1000 A/F sensor, which is the ONLY aftermarket A/F sensor Kenne Bell trusts when you are questioning their tune if that tells you something.

I think the problem is fixed...thanks to Van's advice. He said to change out all my plugs (which were BRAND NEW BTW) and gap them at 0.032".

I already had gapped them to about that range I had thought, but maybe one was bad. So I removed all the old plugs and also tested the gap. most were right at 0.035...but one was 0.040. That subtle difference, apparently, makes a world of difference when you are talking about high RPM's.

So, I spend a long time with the new plugs, gapping, and regapping, and re re gapping until I thought they were all equal and perfect. Hard to do as sometimes the plugs can "stick" to the gapper if there is a sharp corner.

Put them all in, and did another run. Looks much better. Amazing how such a little thing can make a big difference.

Hope that fixed the issue. Do you know which cylinder the bad plug was on?

No Lee I do not know. Van said the custom is to just replace them all, so I did. It might have been something as simple as mixed gaps, but not sure. I'm glad I didn't have to go looking for some vacuum leak!

Hey let me know when you have those prices for carbon fiber parts, I'm still interested.

Not to be a downer but plug gap .035-.032 will yield little to no difference at boost levels lower than 20 psi. When you gain some miles on the new plug set re-log and post the graph please.

If one wasnt seated he could have been losing compression. May not necessarily be the gap that caused the issue on its own.

But yea, wait a week and datalog again.

One of them was 0.040.