Bowtie70SS Posted August 3, 2006 Report Share Posted August 3, 2006 (edited) Here's my situation...I messed up 4 pistons on my old engine in the SS. Had a shortblock built with forged JE pistons(supposedly 9.25 to 1 comp), Eagle rods, a Comp .640 227 cam, morel lifters. I have terrible KR when I tip into the throttle say 10-20% or on a mid throttle take off it will start out ok and then ban 7 degrees. It has been hot outside but my IAT's were in the 125-145 range. I have been watching my LTFT's and they are approx -10 and -8.5. I am running a max timing of 15 degrees according to the scan gauge. I just got HP tuners and should have my laptop this afternoon. I have been reading about tuning the VE map and since I am FI it looks like it will be tricky. I am gonna start by scaling part of the table to get my LTFT in order. What else can I look at? My "tuner" is a Camaro guy and I know they are similar, but the Radix and the weight of the truck he is not used to. The tune seems like it was done quickly and may be sloppy, I hope. I can hear piston slap when cold, and the valvetrain noise of a large cam but the knock sensors shouldn't be reading this, right? I have done a bunch of searching and am just looking for some suggestions. I will try and get some logging done tonight so hopefully some of you guru's can help me. Thanks Dave Edited August 3, 2006 by Bowtie70SS (see edit history) Quote Link to comment Share on other sites More sharing options...
misterp Posted August 3, 2006 Report Share Posted August 3, 2006 (edited) Food for thought... what's the AFR doing? It's either running lean, or octane not sufficient, or false knock. If the motor is not going lean and your octane is sufficient then I'd hunt for false knock, I've read lately of the knock sensor being thrown for a loop by exhaust pipes banging against the underside of the chassis etc... Mr. P. sorry, just reread your post, those LTFT seem a bit on the low/lean side don't they? Edited August 3, 2006 by misterp (see edit history) Quote Link to comment Share on other sites More sharing options...
RevolutionRaceWorks Posted August 3, 2006 Report Share Posted August 3, 2006 Defintely raises the question in my mind of false knock.. your new parts might be emiting a bit more harmonic resionance than the old stock parts possibly sending a false knock signal. Defintely check that against your AFR's and see if it is true. Quote Link to comment Share on other sites More sharing options...
Bowtie70SS Posted August 3, 2006 Author Report Share Posted August 3, 2006 I thought when the LTFT's were negative that meant it was taking fuel away? As in -10% and -8.5%? I am beginning to wonder how well all my engine parts are getting along...The Radix, cam, headers, pistons. False knock could be the culprit, and once I get to logging and tuning tonight I'll have a better idea of what's happening. At WOT things seem to be happy, but at part throttle it's shi++y. From what I have read it may have something to do with a improperly tuned VE table. Dave Quote Link to comment Share on other sites More sharing options...
BenKey Posted August 3, 2006 Report Share Posted August 3, 2006 Sounds similar to tip-in KR. I was getting quite a bit of that at one point - of course now my tune is all out of whack. I looked at my timing table and saw that my normal driving around timing was way too high so that when I pushed the throttle in to go WOT from just cruising, it caused my timing values to move to different areas of my timing table based on DYNCYLAIR and the transition was like from 40 to 25 (example) from one cell to the next. I reduced the large gaps and smoothed it more and it went away. Basically, my timing table starts high then tapers down as it moves to the area for WOT, not drops off cliffs like it was. Quote Link to comment Share on other sites More sharing options...
.justin. Posted August 4, 2006 Report Share Posted August 4, 2006 I thought when the LTFT's were negative that meant it was taking fuel away? As in -10% and -8.5%? I am beginning to wonder how well all my engine parts are getting along...The Radix, cam, headers, pistons. False knock could be the culprit, and once I get to logging and tuning tonight I'll have a better idea of what's happening. At WOT things seem to be happy, but at part throttle it's shi++y. From what I have read it may have something to do with a improperly tuned VE table. Dave <{POST_SNAPBACK}> Yep. Negative trims = excessive fuel. VE table could definitely be the culprit. To get it really nailed down, you'll need a wideband. It's especially important to have one with a radix anyway... You can't depend on LTFTs to tune the VE, as they don't carry nearly the resolution that the VE table does. A few cells versus well over 100 VE table cells. Quote Link to comment Share on other sites More sharing options...
Bowtie70SS Posted August 4, 2006 Author Report Share Posted August 4, 2006 Anybody willing to let me e-mail this tune to them to look at...maybe point me in the right direction? Thanks Dave Quote Link to comment Share on other sites More sharing options...
.justin. Posted August 4, 2006 Report Share Posted August 4, 2006 If you've got EFI Live, you can send to me. jgadberry AT gmail DOT com. Justin Quote Link to comment Share on other sites More sharing options...
Bowtie70SS Posted August 4, 2006 Author Report Share Posted August 4, 2006 Dang...I have HPtuners. Quote Link to comment Share on other sites More sharing options...
.justin. Posted August 4, 2006 Report Share Posted August 4, 2006 Dang...I have HPtuners. <{POST_SNAPBACK}> Send me a log in excel format and I'll take a look at it and see if there is anything obviously wrong. Justin Quote Link to comment Share on other sites More sharing options...
Bowtie70SS Posted August 4, 2006 Author Report Share Posted August 4, 2006 I'm working on it...I don't have excel. I'm still new at this whole thing. I need to export the logfile to a excel spreadsheet...correct? I can do another log tonight. I suspect one thing is my IFR is on set at 38.XX I thought the radix injectors were 42lbs at 58psi? I appreciate it and am working on it right now. Dave Quote Link to comment Share on other sites More sharing options...
BenKey Posted August 4, 2006 Report Share Posted August 4, 2006 Been there. I put 3 (cams) of them in. Like I mentioned about the stock cam bearings, they are cheap. No matter what build you get, get the cam bearings changed out to Durabond bearings, even if it is a new block. <{POST_SNAPBACK}> The problem with just going in a changing your IFR, you'll change your fueling across the board. Quote Link to comment Share on other sites More sharing options...
Bowtie70SS Posted August 5, 2006 Author Report Share Posted August 5, 2006 (edited) I changed the IFR to what is was supposed to be. I disabled the MAF and logged LTFT's into a histogram. I added the values to my VE table. My trims are a lot closer, O2 B2 S1 seems to be switching a little slow. I have changed it previous to the engine, but I think it was contaminated...good thing I have a warranty on the O2. Anyhow, on the way home tonight I watched the LTFT's and they were between -1 and 3.9. A LOT closer than then -12.9 they were. I layed into it and did a WOT 1-2 shift no KR, it pulled a lot harder than it used to. Another question: Since I changed my IFR to what is supposed to be what else needs to be checked/changed? I will do some of my own research and see what I come up with. Dave Edited August 5, 2006 by Bowtie70SS (see edit history) Quote Link to comment Share on other sites More sharing options...
.justin. Posted August 5, 2006 Report Share Posted August 5, 2006 I changed the IFR to what is was supposed to be. I disabled the MAF and logged LTFT's into a histogram. I added the values to my VE table. My trims are a lot closer, O2 B2 S1 seems to be switching a little slow. I have changed it previous to the engine, but I think it was contaminated...good thing I have a warranty on the O2. Anyhow, on the way home tonight I watched the LTFT's and they were between -1 and 3.9. A LOT closer than then -12.9 they were. I layed into it and did a WOT 1-2 shift no KR, it pulled a lot harder than it used to. Another question: Since I changed my IFR to what is supposed to be what else needs to be checked/changed? I will do some of my own research and see what I come up with. Dave <{POST_SNAPBACK}> Do NOT, repeat do NOT run boost with the MAF disabled unless you're using a 2 bar map sensor Quote Link to comment Share on other sites More sharing options...
Bowtie70SS Posted August 5, 2006 Author Report Share Posted August 5, 2006 Good point...I thought about that. I got into boost a little but I didn't wail it because as I read the VE is only for 4000rpm and below anyway right? Can I then tune the VE table with the MAF on? Dave Quote Link to comment Share on other sites More sharing options...
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