Nate1647545505 Posted December 18, 2003 Report Share Posted December 18, 2003 Hello all, Had a conversation with some tuning friends about what the A/F ratio under high boost should be. One of them mentioned STP, standard temperature & pressure. Apperntly 14.7:1 is stoic dependant on many variables. Just want to know what common "scale" we use here in Ohio (they were California based) For example : They consider 10:1 to 11:1 R graemlins/thumb.gif 13:1 to 14:1 L graemlins/thumbsdown.gif 14:1+ = graemlins/nutkick.gif Quote Link to comment Share on other sites More sharing options...
slow4now Posted December 19, 2003 Report Share Posted December 19, 2003 Probably not the answer you are looking for, but if you tune with a properly calibrated wideband O2 sensor 12:1 is stoich. I would tune from 11:1 to 11.5:1 personally. I honestly have no clue what your buddies are talking about, I think they have one thing mistaken for something else. There is no "scale" for A/F ratios. I think what they may be trying to say is that elevation, intake air temp and other factors affect how much fuel is necessary to reach the proper level of tune. Say if you tune your car at 1500 ft about sea level and then drive to somewhere that is at exactly sea level, the car would need to be retuned if the method of fuel control cannot compensate for different atmospheric conditions caused by elevation changes. Quote Link to comment Share on other sites More sharing options...
Guest stevil Posted December 19, 2003 Report Share Posted December 19, 2003 Originally posted by ///M3 on crack: One of them mentioned STP, standard temperature & pressure. Apperntly 14.7:1 is stoic dependant on many variables. For example : They consider 10:1 to 11:1 R graemlins/thumb.gif 13:1 to 14:1 L graemlins/thumbsdown.gif 14:1+ = graemlins/nutkick.gif Depends on what context the A/F is taken... WOT, idle, cruising, etc. That 14.7:1 number is stoic, and should yield perfect parts for combustion of air and fuel, nothing leftover. And thats what most fuel injected cars strive for while idling, cruising, etc. It's on the "lean side" for WOT, but that reduces emmissions and such during daily driving and since the load and rpm isn't much, it's perfectly OK. Now for WOT, you want something richer, especially under boost. I think 13:1 and above is too lean, shoot for 12:1 to 12.5:1 for the most power, or lower on boost... better to be too rich than too lean. Usually under WOT, cars switch fuel tables and automatically strive for something richer around the 12:1 area. Quote Link to comment Share on other sites More sharing options...
BiG BeN Posted December 25, 2003 Report Share Posted December 25, 2003 i've always heard 11.5:1 - 12:1 was pretty safe for a turbocharged car running good pump gas. i can't really back it up, but thats what i trust my engine with. Quote Link to comment Share on other sites More sharing options...
SHIEF Posted December 26, 2003 Report Share Posted December 26, 2003 I'd go with a 12.7 at WOT, that's ideal from the research I've done as far as turbocharged goes. Quote Link to comment Share on other sites More sharing options...
rl Posted December 26, 2003 Report Share Posted December 26, 2003 Originally posted by SHIEF: I'd go with a 12.7 at WOT, that's ideal from the research I've done as far as turbocharged goes. Tuning a street car that close to the 'edge' is not the best idea ever. Quote Link to comment Share on other sites More sharing options...
SHIEF Posted December 26, 2003 Report Share Posted December 26, 2003 13's are the edge Quote Link to comment Share on other sites More sharing options...
rl Posted December 26, 2003 Report Share Posted December 26, 2003 Originally posted by SHIEF: 13's are the edge 13's are breaking ring lands if it detonates at all. Especially if your just using a piggy-back system on a stock Honda ECU. Leaner is not always meaner, you'll find power running more fuel a LOT of the time. Quote Link to comment Share on other sites More sharing options...
Renner Posted December 26, 2003 Report Share Posted December 26, 2003 As rob mentioned, 13.0 and even 12.7 are way too lean for a street driven turbo car. I typically tune for 11.5 target during wot, with small transitions to 12.0 being acceptable. This is a proven safe limit on most pent roof chamber, intercooled turbo cars. With changing atmospheric conditions, and with not being able to re-tune your car every day, having a target of anything past 12.0 during your initial tune is asking for a melted piston. Quote Link to comment Share on other sites More sharing options...
rl Posted December 26, 2003 Report Share Posted December 26, 2003 Originally posted by Renner: As rob mentioned, 13.0 and even 12.7 are way too lean for a street driven turbo car. I typically tune for 11.5 target during wot, with small transitions to 12.0 being acceptable. This is a proven safe limit on most pent roof chamber, intercooled turbo cars. With changing atmospheric conditions, and with not being able to re-tune your car every day, having a target of anything past 12.0 during your initial tune is asking for a melted piston. Well put. We generally do a 11.5 target, with a little more fuel at the torque peak. With a Honda system you have the problem of the AFR changing day to day due to air, I always tune rich with Honda's. With the Ford systems we use they have adaptive learning, it calculates how much it must compensate to achieve 14.7 at idle and it uses this information and applies a correction across the entire curve. If you tune the car correctly then the adaptive will keep the AFR right where you have it targeted, so it could be a 100* day or a 20* day and it would maintain the same AFR. It is a little more complex than that and takes in a LOT more variables, but you get the idea. smile.gif Not that this has any relevance to anything in this thread. I'm very partial to MAF systems. lean =/= mean. Dont listen to what you read on the internet message boards, go read some books on ICE's. Quote Link to comment Share on other sites More sharing options...
SHIEF Posted December 26, 2003 Report Share Posted December 26, 2003 Didn't know we were talking street driven daily driver, my bad. Quote Link to comment Share on other sites More sharing options...
rl Posted December 26, 2003 Report Share Posted December 26, 2003 Originally posted by SHIEF: Didn't know we were talking street driven daily driver, my bad. It holds true even with a race car... Quote Link to comment Share on other sites More sharing options...
SHIEF Posted December 26, 2003 Report Share Posted December 26, 2003 Hmm Quote Link to comment Share on other sites More sharing options...
Nate1647545505 Posted January 6, 2004 Author Report Share Posted January 6, 2004 What are these ICE's you speak of? Can anyone suggest any books on engine control systems? Thanks, still learning alot, my quest to become a bmw tuner has just gotten a hellova lot funer. Quote Link to comment Share on other sites More sharing options...
rl Posted January 7, 2004 Report Share Posted January 7, 2004 Originally posted by bavarian built hot rod: What are these ICE's you speak of? Internal Combustion Engine's Quote Link to comment Share on other sites More sharing options...
Nate1647545505 Posted January 7, 2004 Author Report Share Posted January 7, 2004 roger that Quote Link to comment Share on other sites More sharing options...
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