A/F ratio question
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Teching In
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A/F ratio question I had my car dyno'd and put down 328.8RWHP/335.5RWTQ. The wideband showed to be around 13.5-13.6 in the upper rpm's. The only mods done to the car was a lid, descreened MAF, and EGR hacked off. It's a 00' WS6 with 36k on it. I did change the fuel filter afterwards, so that could help it a little.
Question is: Is the A/F safe to run like that? I can't hear any knock or pinging. Would the car make more power if the car ran a little richer? Also, where can I get another stock MAF screen to put back in?
Thanks in advance,
Dale
Question is: Is the A/F safe to run like that? I can't hear any knock or pinging. Would the car make more power if the car ran a little richer? Also, where can I get another stock MAF screen to put back in?
Thanks in advance,
Dale
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From: Troy, AL
In my somewhat limited dyno experience, it'll make roughly the same power from 13:1 all the way to 13.6:1 SO LONG AS you don't encounter detonation. It's ok to be lean when running NA so long as you don't encounter detonation.
Personally, I'd drop that back to about 13:1 on the dyno.
Personally, I'd drop that back to about 13:1 on the dyno.
Lean that puppy up and oce you get that sqwaured away start tweaking the timing
Check out this site and the PCM Diagnostics forum on this board for more PCM related issues and tuning
www.ls1tuning.com
Check out this site and the PCM Diagnostics forum on this board for more PCM related issues and tuning
www.ls1tuning.com
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From: Atlanta, GA
always can add more timing with a little richness 
those tailpipe widebands are not terribly good since most of the widebands require AIR to accurately dial in the nernst cell. If you shove a wideband up the tailpipe its hard to get a fresh reference air (no gas) unless its something special. I'd always spend the $20 and have a special bung welded in for the wideband.
The whole point of the ion air pump is to reference pure air (no exhaust) to get an accurate reading.
those tailpipe widebands are not terribly good since most of the widebands require AIR to accurately dial in the nernst cell. If you shove a wideband up the tailpipe its hard to get a fresh reference air (no gas) unless its something special. I'd always spend the $20 and have a special bung welded in for the wideband.
The whole point of the ion air pump is to reference pure air (no exhaust) to get an accurate reading.
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From: College Station, Tx
FWIW most of the tailpipe kits i have seen (dynojet) are actually just a sampling probe that pumps exhaust into a heat controlled box containing the oxygen sensor - so it does infact have a proper "fresh air" reference.
I would think you are probably on the lean side also - if that is were it made best power then I would add add in 2-3% fuel to account for the loading differences - if you still want to be right on the edge. Personally I would try and keep it at 13.2:1 or richer on the street, just for the sake of safety/longevity. As with all things there isn't really any "magical number", it's just a tradeoff between power and safety.
I would think you are probably on the lean side also - if that is were it made best power then I would add add in 2-3% fuel to account for the loading differences - if you still want to be right on the edge. Personally I would try and keep it at 13.2:1 or richer on the street, just for the sake of safety/longevity. As with all things there isn't really any "magical number", it's just a tradeoff between power and safety.
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Originally Posted by ChrisB
FWIW most of the tailpipe kits i have seen (dynojet) are actually just a sampling probe that pumps exhaust into a heat controlled box containing the oxygen sensor - so it does infact have a proper "fresh air" reference.
I would think you are probably on the lean side also - if that is were it made best power then I would add add in 2-3% fuel to account for the loading differences - if you still want to be right on the edge. Personally I would try and keep it at 13.2:1 or richer on the street, just for the sake of safety/longevity. As with all things there isn't really any "magical number", it's just a tradeoff between power and safety.
I would think you are probably on the lean side also - if that is were it made best power then I would add add in 2-3% fuel to account for the loading differences - if you still want to be right on the edge. Personally I would try and keep it at 13.2:1 or richer on the street, just for the sake of safety/longevity. As with all things there isn't really any "magical number", it's just a tradeoff between power and safety.
joel
Originally Posted by binksz06
ChrisB - What's the lowest AFR we should shoot for on the street. I'm open loop with a FJO Wideband.TIA.
joel
joel
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From: Atlanta, GA
The FJO is top notch shiz. They build stuff (used to) for the govt. Probably a tool used to tune tanks n stuff lol.
The dynojets here that i go to weld a bunghole (lol) in and plug directly in. They do not use the tailpipe. EGT's affect air fuel ratio, thus by the time you get to the tailpipe, its possible to skew the results.
Dyno's cant really simulate real world events unless they have a 100mph windtunnel. Things like RAM AIR and wind resistance and weight are simply not perfectly replicable on a dyno. Hence the need for widebands that are portable.
Most of the good tuners can afford a baseline $325 (wholesale) to nice (700+ - fjo) portable wideband. Sure you can do WOT under fixed conditions, but you still need to bust the laptop out to do the part throttle tuning.
I've logged o2 sensors versus widebands, and o2 sensors are FAR slower in change, and greatly effected by EGT as well. Some knock (or if you boost/n2o) can throw the regular narrowband way off course.
Most dynojet's use bosch sensors which are slower than then NTK honda ones. However the NTK is more sensitive to exhaust pulses.
I'd guess Mr FJO user above has seen a much more "wavey" result with more samplepoints than a typical bosch lsu dynojet wideband output produces. They use "smoothing" almost always which is purty, but what the heck does that do for ya on tuning.
luckily the ecu for these ls1's is pretty advanced, to make up for gross mistakes some tuners could make.
The dynojets here that i go to weld a bunghole (lol) in and plug directly in. They do not use the tailpipe. EGT's affect air fuel ratio, thus by the time you get to the tailpipe, its possible to skew the results.
Dyno's cant really simulate real world events unless they have a 100mph windtunnel. Things like RAM AIR and wind resistance and weight are simply not perfectly replicable on a dyno. Hence the need for widebands
that are portable.Most of the good tuners can afford a baseline $325 (wholesale) to nice (700+ - fjo) portable wideband. Sure you can do WOT under fixed conditions, but you still need to bust the laptop out to do the part throttle tuning.
I've logged o2 sensors versus widebands, and o2 sensors are FAR slower in change, and greatly effected by EGT as well. Some knock (or if you boost/n2o) can throw the regular narrowband way off course.
Most dynojet's use bosch sensors which are slower than then NTK honda ones. However the NTK is more sensitive to exhaust pulses.
I'd guess Mr FJO user above has seen a much more "wavey" result with more samplepoints than a typical bosch lsu dynojet wideband output produces. They use "smoothing" almost always which is purty, but what the heck does that do for ya on tuning.
luckily the ecu for these ls1's is pretty advanced, to make up for gross mistakes some tuners could make.
Originally Posted by binksz06
ChrisB - What's the lowest AFR we should shoot for on the street. I'm open loop with a FJO Wideband.TIA.
joel
joel
Is there a reason you are running in open loop also? I got tired of fighting the ECU's fuel trim.
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Originally Posted by lbz34
Is there a reason you are running in open loop also? I got tired of fighting the ECU's fuel trim.
joel
