Guest bastaad525 Posted October 11, 2004 Share Posted October 11, 2004 I found this thread to be VERY interesting... not sure how I missed this one the first time: http://hybridz.org/nuke/index.php?name=PNphpBB2&file=viewtopic&t=32009&highlight=12+5 That's a post re: TimZ's dyno from a while back. I'm not even sure what motor he's running but I THINK that's a built up L28ET?? but a few facts caught my eye here... pump gas, 22psi, 467rwhp, and a/f ratios leaner than 13:1 up until 6000rpm!!! okay so he didn't leave it running that lean, but he did state that even at that a/f ratio he was getting no ping, and EGT's stayed in check at around 1400 degrees all the way up, measured from before the turbo. To me, this contributes even more to making a very strong case for NOT needing to run ~11:1 a/f ratios to be safe on a turbo car, even a high boost high power one like this.... Quote Link to comment Share on other sites More sharing options...
ZR8ED Posted October 11, 2004 Share Posted October 11, 2004 Well as I understand it. The theoretical optimum ratio is 14.3:1 (off hand I think). That means whether at idle, off idle, or WOT. I think most people talk ratios in the 11:1 range are doing so because of the large investment in parts/time, and the lack of ability to fully control air/fuel ratios and knock/ping. (hey I'm no better either) I'm just stating my thoughts on the reason for the richer ratios. It is a built in safety margin. Also remember not everyone on this forum has access to the same types of fuel. I can run 94 where I live, but some only have 91 octanes Turbo Moto: When in doubt richen it out! hehehe Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted October 11, 2004 Share Posted October 11, 2004 yeah I can understand wanting to run rich to protect your investment... but you see there is also all this confusion over what is optimal for power, I keep hearing different numbers, and even as to what is safe... well who figured out you had to run 11.5:1 to be safe? Who's blowing motors at leaner ratios than this? Let me restate that question, who is blowing *L28ET'S* at leaner ratios than this?? Certainly not I. TimZ certainly didn't I know I'm making a big deal out of it, but damn... I can't help it. Every time I look at my dyno sheets and think of all the 'free' power and more efficient performance I"m giving away simply in the name of being 'safe' when I probably don't need to be. Of all the questions and issues I've brought here to Hybrid Z, or those that others have, this one is almost like the good old N42/P90 head debate... lots of guys disagreeing, and no one seems to have many facts to back up their oppinions, but we know SOMEONE is losing out one way or another. Quote Link to comment Share on other sites More sharing options...
Mikelly Posted October 11, 2004 Share Posted October 11, 2004 Jim Pearl AKA BLKMGK just attended a special class on EFI standalone systems and programing. The first day was the introduction course, and the second and third days were dedicated to more indepth tuning. Jim is on here very little these days, But I'd encourage any of you to look him up, since he is VERY smart when it comes to tuning EFI and he is the only guy I know who is running a TRUE 550WHP Supra in Washington DC Rush hour traffic DAILY... Commuting 60+miles round trip! Jim told me that during the class they used his car on the dyno, chucked out the A/F ratios and focused on ignition timing and spark advance. The number one focus on their three days of learning was to debunk the myth of A/F. According to Jim, once he got over this fact and moved on to focusing on Spark and ignition curves (keeping a keen eye on the fuel maps to insure that the car never ran dangerously lean), he claims they picked up a full 40+ HP at the wheels throughout the center (Mid Torque) of the rev range. I encourage you guys to contact Jim offline... Lately his Zcar has been sitting and his laptop has been burning keys while he tunes customer cars and tweeks his Single turbo Supra into the 9s... He's currently running 10.5s, but has a 4inch downpipe, bigger turbo, and a few other mods going into the car, along with a new head. Mike 8) Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted October 11, 2004 Share Posted October 11, 2004 yeah I noticed BLKMGK doesn't post around here much more... kind of a shame since his posts were usually really informative. I was actually following along with some of his posts over on the Supra/AEM standalone boards, lots of interesting stuff regarding alchohol injection, among other things. I'm gonna email him right now, see what he's got to say. It's funny you say all this though, because not too long ago I was as 'obsessed' about the effects of ignition timing on power as I am about afr's on power now. I had gotten to a point where I strongly believed you could gain more power overall, a better curve, by lowering boost and advancing timing, but that idea was shot down on all counts. At any rate... about finding so much power thru tuning of advance curves unfortunately with a stock system I only really get the one adjustment Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted October 13, 2004 Share Posted October 13, 2004 Got a nice little dialogue going with BLKMGK by email now... it's really a shame he's not sharing his knowledge 'round here anymore One thing he pointed out to me that I hadn't really noticed or made the connection, really... is, why does my car seem to lose SO much power from moving the a/f ratio around?? In that link I posted, TimZ's dyno results, he initially starts out running pretty lean on the first run, up in the high 13:1 range at about 4000rpm On the next graph, he's richened up to low 12:1's at the same rpm. He loses all of like 5hp, and torque stays almost exactly the same, dropping off a little bit as revs go up. Whereas I lose about 20ft lbs from a similiar change in a/f ratio. Quick question, does anyone know what, if any, effect the head temp sensor has on ignition timing? Maybe I lose so much power because the motor was getting too hot and it was pulling timing? Quote Link to comment Share on other sites More sharing options...
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