KR Trouble with 3.6" SC Pulley

Didn't think 104's were needed for my setup a few months ago, so I opted for 605's. How much difference do you feel 104's would make in place of 605's? I figured to change plugs the first week of Oct when I'm off work again, IF I pull a couple out and they look like it's needed. They're only a couple months old, if that. No need to replace if they stayed clean thru the Seafoam. Still, I'd do the 104's if they could help some on the KR.

Recorded LFT's, MAFF, and O2, but LS1M doesn't list an A/F parameter. LFT1 recorded around -11 til 14% TPS, then toward zero until about 44% TPS, crossed over to + 1.6 at 45% and locked there all thru WOT.

This will be much easier when I can post the log tonight, really hard to get this info reading it off the Palm.

Not sure how much difference, but every little thing helps, and plugs are cheap. As long as you exercise using boost now and then, I think 104s will work. I'd replace them no matter what after the Sea Foam treatment. INTENSE recommends:

* Use the Autolite® 605 spark plugs (one heat range colder than stock) if you have a 3800 Series II or III engine engine with up to 6 pounds of boost. At this level, we recommend reducing the spark plug gap to .055", or .035" with nitrous oxide.

* Use Autolite® 104 spark plugs (two heat ranges colder than stock) if you have a 3800 Series II or III engine with 6 to 12 pounds of boost. At this level, we recommend reducing the spark plug gap to .050", or .035" with nitrous oxide.

* Use Autolite® 103 spark plugs (three heat ranges colder than stock) if you have a 3800 Series II or III engine with 12 to 18 pounds of boost. At this level, we recommend reducing the spark plug gap to .045", or .035" with nitrous oxide.

I think at 9 PSI, you're in 104 territory. The idea is, cooler plugs let more heat out of the cylinders. It can only help to change them out, imo.

I'm reading your scans very clearly from your description. Appears you're running slightly rich as you go WOT, which could be part of your problem.

Slightly rich shouldn't add to a KR problem though, should it? Or are there other factors in the lean vs. rich equation?

I hadn't read that guide for some time, thanks for posting it here. I think at the time I was starting mods, wasn't planning as much as I've done.

BTW, PFYC says I have to measure at the belt to determine which pulley I have. Going to check...

Quote :

2.56 rear just doesn't cut it at the track.

no. That's what I have in my RM and it is a dog off the line.

I have a half decent 60' for the Buick 350 / 2.56 posi rear end combo I have. The 350 has good torque numbers, but I die by half track with a stock-ish cam and no head work. Great for 2000 mile trips though.

The pulley looks to be correct at about 3.6.

Uggh.. Sorry, I meant to say "lean". + trim means the PCM is adding fuel, or it thinks the A/F mix is lean. It confuses me as well sometimes. You want LTFT to lock in at zero, or slightly on the neg side (rich) at WOT. Anytime trims are +, it means the PCM thinks you're lean.

Ok, gotcha. Here's my scan today:

www.scandepot.net/viewscan.php?pk=4348

Thanks, that's a cool way to display your scan! I'll get a BIN together for you. I've never written for another car's PCM, so will be interesting to see if it will allow you to write. I'll squirt a little extra fuel into the fire, should cool that knock down.

Do you want the Perf Shift option? I use the factory Perf Shift settings in the Riviera's PCM, not anything radical. Makes the shifts a little firmer and quicker; you can't turn it off, though.

Haven't you seen Scan Depot before? Pretty cool option.

The factory Perf Shift settings will be just fine, and I won't want to turn it off. Soft, slow shifts suck big time.

Thanks!

Check your email for the BIN. Sending it now.

Got it!

Thanks Aaron, I see there's something waiting for me on my work email server...

So when are you getting it uploaded to the PCM? I'm looking forward to seeing your next scan!

Thu night possibly, or may be next week. Will update afterward for sure.

6pm tonight!

Well Aaron, we pulled it off, with a little hesitation. Before we uploaded, got a popup msg warning that the software didn't recognize the PCM's OS ID. We read thru the fine print a couple times, and hit the OK anyway...(my call)

Uploaded w/o a hitch, then crossed fingers when I hit the ignition! Started right up, and I breathed a BIG sigh of relief. Did some easy cruising around town for a bit, then did a short stretch on interstate, accelerating a bit harder. Sorry to say, the KR is still present. Mike did some logging, and will email the file to me later, and I'll post it up. Still saw 5-6deg of KR, again coming in at around 40mph. Only went up to 60, as we hit a sgl lane construction stretch, and it was getting late.

The car runs great, the fans actually turned on for a change, and the modified trans shifts are fantastic. O2's were low, mostly in the 800's, with one reading just under 900, so it is lean. I did not find time to swap in the 104's, that will get done Monday or Tuesday.

Haven't decided if I will log a WOT run tomorrow, or do some more casual driving for a few days then log early next week. I have a nice Flex medical reimbursement check coming in a few days, and a chunk will be used to order me up a PT from PFYC, and try to find a decent cheap laptop...

Short log of a brief low speed run on interstate last night. Will try to get a log done at noon today with my LS1M.

http://www.scandepot.net/viewscan.php?pk=4409

Sorry to hear about the KR situation. I will look at your scan soon. What was ambient temp when you did the scan? Has your O2 sensor ever been replaced?

Looking at your scan, I do see some improvements. First, at lower throttle LTFT went from -11 to +2. This ideally should be between -3 and 0, but for a first tune, not bad. Second, you're now locking in at 0 LTFT at WOT. This is very good.

I don't understand the low O2 values. They were showing 900-920s before, which is slightly lean. Now, after I tuned for 3% more fuel, they go lower... doesn't make sense... they should've went up. Makes me wonder if there's a problem causing these readings to be incorrect.

I am convinced there is a problem somewhere. Your engine should not be knocking 6 deg with 6 PSI at 3k RPM. Maybe next step would be to change those plugs out. Then I could tune again based on the new data, also set your timing back to stock. I was afraid the slight timing advance would not help things...

Oh, are you sure the BBV is set in the correct position? I thought you tried modding this, can't remember though.

No hurry here Aaron, take a look whenever you find some time. Not much to see in this scan. Ambient was about 60deg. Denso O2's were both installed 2 weeks ago with the new DP and cat.

Think I'm going to gas up at a different station next fill. I've been running 92 from Amoco, exclusively. It's 91 most everywhere else, but I'll try a different source. Also will be doing the 104's early next week while I'm off work.

Sounds like a PT will be available for sale on a local board in the next couple weeks, was offered to me last night. Do you happen to know how licensing/ownership issues are handled when you buy used?

You can just call or email DHP, they'll set you up. But you already have the BIN, so it should work for you. Also Rob (Rivman) works with DHP, so he might be able to help you if you give him a shout.

If it's 60F, I'm really surprised at your scan results. KR should be gone, imo. Good idea switching gas. I've run across a bad batch one time.... Instant 5 deg KR when previously it was zero!

How do you like the trans holding on into higher RPMs during normal (25-50% throttle) driving? Should rev to 3.5k-4.5k RPM before receiving your 1-2 gear "jolt".

Any thoughts about TCC while cruising? Try accelerating from TC lock-up at 65 mph. Then compare to the way it used to be by engaging cruise control and trying the same thing.

Cool, thanks.

I love the higher revs in normal driving. The old lower RPM shifts sucked big time. I think you have things set just about perfect for the street. The shifts are noticeable but not harsh. VERY happy with the work you've done! I did accelerate from a steady 60 last night up to 75, and yes, could feel the difference in the tranny.

As I think you've said before, it's almost like driving a different car.

So tell me, what are the implications of me already having the BIN file loaded? When you buy a new PT, do they include a BIN? Or are you simply taking your stock PCM data, and creating your own BIN? I'm a bit fuzzy on this. It would be nice to get a deal on a used PT, but not if it's overpriced. He says when he bought it, the open 3800 tuning was a $100 add-on, which he has.