I could use some tech opinions from anyone with experience in dealing with detonation. Kind of long but I want to include as much info as I can. I am on my second 426 as the first one had some issues with the knock sensors being basically disabled and I lifted the #1 cylinder ring land (which disappeared without any trace.) Others were ready to pop also. I had my latest motor rebuilt last year and had it retuned at SVS...been running awesome but I hadn't flogged it too bad anywhere. I saw ~2-3 degrees KR max using my Aeroforce gauge and this was usually when the car shifted. Otherwise it usually sat near zero. Bob saw the same thing on his dyno at SVS. I am running 10.5:1 CR and Iridium 5107 plugs (2 steps colder.) I live at 7000 feet. I get tuned at sea level. The tune I run is the sea level tune minus a bunch of WOT fuel based on my wideband, which seems to be working fine (~14.7 while driving.) At WOT at 7000 feet I am 12.0 initially then 11.5 to 11.2 at 4k on up, so I don't seem to be lean. Last month I decided to "fix" my noisy valvetrain and installed intake pushrods that were .050" longer than stock. On startup, the car ran like shit for 20 or 30 seconds then seemed to smooth out except for a pulsing I could feel while creeping forward at idle, etc. I got a P0301, P0300, & Manifold Pressure code the next day. I checked #1 spark plugs and they looked great, but ordered pushrods that were .015" longer than stock and installed them instead which took care of the pulsing and off to racing I went. (I mention this just in case it was even an issue, and I already had exhaust pushrods that are .015" longer.) I have one of PPPs cams, 224/228 .598" .578" 114, and still running PPPs "Stage 2" heads with Manley NexTec springs or whatever they are called...orange stripe on them anyway. Aug 14th I spent the week-end at the track and was running in the 12.5/112 range all week-end. I drove home 400 miles from the track and drove the car 6 or 7 times after that...car still ran great...best it ever has in fact. Two weeks ago I started the car to back it out of the driveway and instantly had a miss...P0301. 2 smashed plugs on cyl #1. We scoped that cyl and yup, missing 3/4" of the top of the ring land and the piston looked beat to heck. Car still runs great with 2 new plugs, but time for some repairs. I have to believe I did the damage at the track but I want to get some confirmation so I don't do it again. What I DIDN'T do at the track 300 miles away was 1) any data logging even though I had my laptop/Predator with me and 2) pay attention to my wideband or KR because I couldn't see them through my orange face shield and the sun was directly on them, plus I had so much sweat in my eyes I could barely see to drive anyway. I am smart. The track elevation is ~4400 feet. The DA that day was ~7000 according to a handheld as well as the racing websites. My wife shot a couple of videos the first day which I watched that night. I immediately noticed random puffs of smoke coming from my exhaust in 3rd gear, and not small. I went out and checked my catch can and it had around 1.5-2.0" of oil in it, which I dumped. The next day the smoke was 99% gone but I still saw a couple of whisps occasionally. Here is the first day early...notice the smoke (ignore my silly wife's commentary): http://s152.photobucket.com/albums/... 08-14-10/?action=view¤t=M2U00006-1.mp4 I am pretty sure that I got things real hot and lean. If I was sucking oil that sure as heck didn't help keep from detonating. I guess I saw the high DA and wasn't too concerned about adding fuel even though I had dropped 2600' in altitude. Was it a combination of things that I could have controlled that smoked my piston or should I be looking for some flaw in my simple N/A build? I have a new ringset, plugs, gaskets and am waiting on 4 new pistons. I could use some intelligent input because I sure as heck don't have things figured out. (Thanks to the couple of people I called that spent an hour listening to my ramblings!)
A 2600' drop in elevation is huge, Jon. That drop can take you from a 11.5 A/F to 12.0ish A/F. Too bad you didn't datalog while at the track. Good luck my friend.
Like Ron said. Did you add fuel back for the drop in elevation? You said you get tuned at sea level and then you pull fuel to compensate at 7000'. ...and then you added the appropriate amount back for the track at 4000'? (those were the puffs of smoke that I couldn't believe no one was alarmed about?) How come you have to guess/trial&error on the push rod lengths? Can't you calculate that? or at least use a gap gauge like we used to? (real men use solid lifters anyway... you don't have hydraulics do you?) GET A DASHDAQ (only a drop in the bucket to what you've spent on repairs now). You can leave it on the dash/pillar all the time. Nothing cooler looking for a gauge solution and infinitely customizable. and you can leave the logging on for days before filling a SD card. You can even plug your stereo into it and have it scream alarms at you at very high decibles while it's flashing. If necessary you can record your own audible alarms in tongues so you can understand them.
Sorry to hear about this Jon. What side of the motor is your wideband on? Where did you get the push-rod lengths from? There is a BIG difference between .050 and .015. While you're in there fixing the short block, please swap out those Manley valve springs for some PSIs or PAC's. It sounds like you went lean at the track and detonated, the extra oil in your intake charge didn't help either. What grade gas were your running? What does your fuel set-up look like?
I'll be heading back to SoCal to get fixed once my pistons come in. I need to whiz in the corner of Cam's new shop anyway. I agree this round of repairs is on me...a combination of things occurred of which I had the total ablilty to control. I got hasty instead of taking a few minutes to do things methodically and paid for it. I had somewhat of a mind that since I was N/A I was probably ok when it came to detonation.
Damn, John This really REALLY sucks to hear. I know Im far away,but if there is anything I can do please let me know.
Thanks dude. BUT...think about this...I can go to my garage and shift my car in and out of P and D as many times as I want knowing I don't have a pink thingy any more Ahhh, I'll get it fixed and remember the lesson...:future:
Well, DA is altitude adjusted to include environmental factors. It's the "effective" altitude (air density) -- i.e. air is less dense at 7000' than at sea level, air is less dense at 100* than at 60* (at the same altitude), air is less dense if there's a low pressure weather system than a high pressure weather system. DA puts all that together and gives you a number. "this is what the air would be like at this altitude with all the other data points at some reference value. Lower density altitude is "better" because denser air has more oxygen per volume which can allow you to burn more fuel per volume. Since you have a fixed volume for air/fuel in your motor (naturally aspirated), getting more oxygen in there to burn more fuel gives you better performance. Summary: Ron's car is slow. Anyway, you only need to know DA and altitude and all that stuff for comparisons of this run to that one and when you're trying to explain why your car is so slow (see Ron above). All you care about is that your A/F is correct. Let's say 12:1. You would need less fuel at the top of the mountain to get 12:1. You would need more fuel at the bottom of the mountain to get 12:1. Don't know about the lifters. DashDaq again. Can set up global default logging parameters. then it doesn't matter what screen you're looking at. When you hit <start log> those parameters will get logged in addition to whatever gauges you have on the current screen. Put your critical parameters in the global list and logging anytime is a matter of a single button press.
I hate reading all the problems you have had Jon...............seems to happen to the really nice guys..............and I aint going to say I .... ... ..
Lol. Thanks man What can I say when I create my own problems? I was just looking to make sure I wasn't missing anything because I am not up for a third set of pistons! After reading others opinions I am pretty sure it was my fault. Got a few more "notes to self" now Looking at the Dashdaq to replace my existing stuff...
Damn, can't we get a break? Firday evening was going pick up my kids, and was idling in traffic at a light, heard clankity-clank...pulled over shut down and called for a tow. Haven't put a wrench on it yet, but think its the timing tensioner...
Shouldn't your MAP, ambient temp, IAT and downstream O2's all see the DA change and make appropriate adjustments to your A/F.
To some extent in closed loop (not really relevant here, but don't forget it only reads outside air pressure at key on). In open loop the fuel add is a fixed value from the PE table cells. That's why you can adjust your WOT A/F with a tuner. WOT is the problem.
Oh man...that sucks arse. Shouldn't be too bad a fix though...just gotta get out there and do it This is the first time I ever heard this...interesting.
Ah crap, dude, that totally sucks. Wish I had some great advice to give, nope, just hope you get back on your feet asap.
