OK this is going to be long and to be honest only those with real tuning knowledge will be able to understand all of this. But ANY help is welcome.
First I will explain my setup.

383 solid roller LT1 260/260 @ .050 on 112 LSA and .618 total lift with 1.52 RR's. 12.3:1 compression JE forged pistons, Scat crank, Forged H-beam rods, 4 bolt splayed caps.....I mean EVERYTHING was done. There is nothing STOCK on my car from air filter to exhaust tips. I have the racetronix 255 GPH fuel pump with 42 lb/hr Lucas injectors. I may have forgot some stuff, but if you name it I replaced it with new and or performance parts.

Here is my problem. I am using the Innovate LM1 wideband kit and its only by logging my AFR with it did I find the reason for my problem I am having. Basically sometimes on the 1-2 and 2-3 shift my car falls on its face for a second and then the power comes right back and it start haulin *** again. Well what Is happening is the AFR is going to 15:1 !!!! after hte shift for exactly .5-1 seconds or so. Below are link to screen shots of the datalogs from the track. I have tagged each shift point, by looking at it you will see the launch, the 1-2 shift, and the 2-3 shift, then Im thru the traps and I let off the gas. now the 1st two runs my car DID NOT fall on its face after hte 1-2 and 2-3 shifts, but as u can see in the 3rd run ( 3rd Link ) the AFR goes way off for a second. Now at first I thought this had to do with the RPMs going too high on the shift points. but as you can see on run # 2 the RPMs almost hit 7500 and it DOES NOT do it. The pcm tune DID NOT change at all during these runs. The car did not always do this, It has just started doing this recently and I just last week removed the inline booster pump for the racetronix 255 walbro pump thinking maybe the fuel pressure was dropping. I But I am confused at to WHAT it could be as its intermittent, It cant be spark knock because the retard should cause hte AFR to go RICHER not leaner. ok heres the graphs.

http://www.southfloridadomestics.com/pic/afr1.JPG
http://www.southfloridadomestics.com/pic/afr2.JPG
http://www.southfloridadomestics.com/pic/afr3.JPG

Is it possible the PCM is unhappy only sometimes going above 7000 ? Altho I have NEVER had this problem before. And by the graphs above you can see run #2 the RPMs were alot higher then run 3 and the AFR didnt go haywire. I also wonder If the MAF is reaching MAX limit ( 401 gps ) which I can change in LT1 edit, but why would it only do this sometimes ? I have hte MAX MAF SES disabled and my datalogs dont show my MAF going anywhere near 400 GPS at WOT. Whats really confusing is its never done this before until recently and I havent changed the tuning except for 2 degrees more advance at 4500-7000 RPMs when on the dyno and I picked up 17 rwhp.

This couldnt be an opti problem could it ??? I would think less spark would make the wideband read richer.

Thanks for taking the time to read this ! Any help or ideas are appreciated.

Thats ugly.You might want to log some Datamaster data also like AFGS and MAP, LTFT's , and Injector pulse widths for sure. See if there's anything flakey there. Do some runs at 6000 and see if you can repeat at the lower RPM. I always thought the PCM math gave up at 6800 and you were in la-la land after that. Maybe your going thru a PCM reset or something wierd. Just thinking out loud here.

Steve

It might actually be some sort of knock.

Spark knock will occasionally look lean.

Would you think that 36 degrees of timing from 5000-7000 RPMs is too much ?

As a matter of fact I used to run 36 @ 5000, 35.5@5500, 35@ 6000, 34.5 @ 6500 and 34 @ 7000. Then on the dyno we leaned it out a little up top and changed the spark advance to 36 degrees from 5000 all the way to 7000. It was shortly after this I noticed this intermittent problem.

When the car shifts intothe next gear the RPMs drop to 5000 which even with my old spark curve was 36 degrees of advance @ 5000. maybe leaning the A/f Ratio out brought about the knock. What would you suggest I try 1st? adding more fuel and leaving the spark the same ? or leavign the current AFR and lowering the spark advance?

What are the datalogs saying? Are you seeing big knock counts in gear changes or fast actions in the pedal.

I would recommend steping down the timing especially on a 383 and especially on that compression.

It probally woudln't hurt to try to shoot for mid 12's at 5k in your case then either.

I wouldn't touch the timing or the fuel as I don't think either is out of line.
I would look at knock count and see if that is the cause of your problem.
Can you post the datalogs that you have? Or are you sure that there is nothing in there that looks any different on that 3rd run as opposed to the 1st and 2nd?

Well I went back to my old spark curve which starts at 36 degrees @ 5000 and falls off to 33 degrees at 7000. I datalogged my car and picked up ZERO spark knock on the shifts. I think what may have been happening is when I passed the 7000 mark on the shift points there was too much advance for that high of RPM causing knock. The messed up shift points was due to me trying to shift my MPH. But now that Dan K showed me how to shift by RPM I tried the RPM shift method in conjunction with using my old spark curve. Unfortunatly I am out of town for a business meeting and wont be back until tomorrow night. I logged on my wideband as well but I forgot the PC interface cable to check so I have to wait until I get home. BTW, Thanks DAN for the RPM method, so far it worked great today altho I need to tweak the RPMs a little. I will do some more research on this issue starting tomorrow afternoon and ill get back to you guys on my findings.

As far as getting the AFR into the mid 12's around 5K that might be a little tougher to do. I use a Open Loop tune and dont use my PE tables at all. The MAF has the STOCK tables and I dont want to mess with them. I may try messing with the VE tables in that RPM area but I am uncertain this will effect anything. My last resort is going back to trying my SPEED DENSITY tune so that I can fine tune with the VE tables.

Il lkeep you guys informed.

Thanks

I have a good reason to belive you are getting detonation on those shifts, My conclusion for this is cause the LM-1 will read LEAN when an engine misfires. The reason it reads lean is cause the fuel AND oxygen are UNBURNED therefore you get more o2. I would try creeping up on the timing in the 5-7000rpm range and also watch coolant temp (may wanna go back and see if it was hot or cold onthe lean out run). 17 rwhp on 2 degrees timing is ALOT. I would try adding a slight amount of fuel to this rpm range as well to help pull some heat out of the cyl. Even better yet try and narrow it down to what cyl is rattling and add fuel to that hole only. I believe you can do this in the individual cyl fuel trim table (off idle). I dont know if it will use this table at WOT or not as I have never really needed to use it this way.

My .02

pretty close to what I was thinking.. although you mentioned more timing... are you sure you don't mean a hair less.

It would help if you had some dyno graphs with this motor on this timing. YOu can really tell if the car likes it or not by its smoothness (is that a word?)

also, how do you have your knock senosr setup? isn't this a solid roller?

More fuel + less timing at those shift.

You know what just popped in my head?

How is the fast pedal movement responce in this car?

Is it possible that the only difference inbetween those runs was letting off the gas to shift? If so you got some AE issues..

You can tweek the MAF a bit to get your extra fuel. It'll work just fine. Don't be skeerd. And hey if you don't like it after your done- flash that puppy back to stock MAF tables

the problem is that it did not have this issue after the dyno tune, I drove the car daily for over a month after the dyno runs with no problems. Then one day I started feeling the loss of power on shifts and hooked up my wideband and found this issue. I have my dyno charts but I need to get them on the PC which I will do later tonight.

When I datalogged the car yesterday I was getting ZERO spark retard even tho the wideband was showing the same 15:1 AFR on the 2-3 shift. Now one thing that was different was it did not do it on the 1-2 shift anymore. And I lowered the shift RPM on the 1-2 shift. Now what I think may be happening is the PCM is freaking out when the RPMs hit 7000. Im going to do more testing and logging and get my dyno scanned.

ok more logging..........same thing its very consistant with spark knock on the shifts. Im going to try to change my MAF tables for the 4500-5500 RPM area, ill need to do some more logging to make sure i got the right frequency to change.

Well goood news

After ruling out detonation and a few other things I decided to check the MAF vs RPM only on the datalog runs. Well it turns out hte MAF was hitting 425 GPS at ~6900 RPMs. The max maf threshold was set to 407 GPS in LT1_Edit, so after bumping it up to 475 GPS the car shifts like a mad man and the AF ratio never fluxuates !!

Thanks for the help guys !

sweet, glad you found the problem.