Correct A/F Ratio...
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Okay I've searched and have not found what I need to know..maybe I'm not looking in the right place either.
Once and for all is there a "magic" A/F ratio all us LSX guys are looking for and does it matter if its a N/A motor, FI motor or a motor built for nitrous?
Here's my dilema...every LSX motor I've run, weather it was a head/cam 346 or an MTI 422 stroker they have all seemed to run rich. A/F on most tunes around 11-11.5:1. Very safe in my book...
Why exactly, looking at our plugs and combustion chambers, does it show this A/F ratio being so very rich? Is that what is "normal" for these LSX motors, a very sooty combustion chamber and not a nice clean, tan colored chamber and plug??
In order to get that I believe we would have to run 12-12.3:1 A/F...I've heard of a few other FI motors, not LSX, running a 12:1 A/F with no problems...
So what "exactly" would be the proper A/F ratio to reach peak performance and still be a safe tune? And like I mentioned earlier does it really matter if its N/A, FI or NOS...?
I'm at around 11-11.2 and the combustion chamber looks sooty as hell. The plugs look so-so a little on the rich side but not pig rich...
Once and for all is there a "magic" A/F ratio all us LSX guys are looking for and does it matter if its a N/A motor, FI motor or a motor built for nitrous?
Here's my dilema...every LSX motor I've run, weather it was a head/cam 346 or an MTI 422 stroker they have all seemed to run rich. A/F on most tunes around 11-11.5:1. Very safe in my book...
Why exactly, looking at our plugs and combustion chambers, does it show this A/F ratio being so very rich? Is that what is "normal" for these LSX motors, a very sooty combustion chamber and not a nice clean, tan colored chamber and plug??
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In order to get that I believe we would have to run 12-12.3:1 A/F...I've heard of a few other FI motors, not LSX, running a 12:1 A/F with no problems...
So what "exactly" would be the proper A/F ratio to reach peak performance and still be a safe tune? And like I mentioned earlier does it really matter if its N/A, FI or NOS...?
I'm at around 11-11.2 and the combustion chamber looks sooty as hell. The plugs look so-so a little on the rich side but not pig rich...
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Once and for all is there a "magic" A/F ratio all us LSX guys are looking for and does it matter if its a N/A motor, FI motor or a motor built for nitrous?
using a wideband LM-1 and some motors will make more power closer to 13:1
and some are more at home around 12.2:1
Here's my dilema...every LSX motor I've run, weather it was a head/cam 346 or an MTI 422 stroker they have all seemed to run rich. A/F on most tunes around 11-11.5:1. Very safe in my book...
They don't require as much fuel as compared to a gen 1 iron SB to make
the same power. BSFC numbers are fairly good with a well built engine combo.
So what "exactly" would be the proper A/F ratio to reach peak performance and still be a safe tune? And like I mentioned earlier does it really matter if its N/A, FI or NOS...?
(dyno/track tune). I truly believe a motor that continues to make power
and is built to handle the RPM is safe. I also believe most motor failures are
due to incorrect timing, motor assembly, clearances, etc. - not because of a tune which yields the most power.
Last edited by Adrenaline_Z; 08-30-2006 at 07:07 AM.
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from what ive seen 12.5ish for a N/A car
11.1-11.5 FI
also from what ive seen is a car may make more power at 13.1 on the dyno but its slower on the street than a car thats a little fatter
11.1-11.5 FI
also from what ive seen is a car may make more power at 13.1 on the dyno but its slower on the street than a car thats a little fatter
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Originally Posted by JMBLOWNWS6
11.7 is the max I would set your monster at!
We can mess motor up being overly rich just as well as being lean so...I'll be doing more "plug" tuning than I've been doing lately.
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Dyno testing is one thing. But, on the street, the A/F ratio will shift. This is based on the load, a non-load dyno will generate vs what you see when the car is actually on the ground.
Too often folks get wrapped up in thinking about an Ls1 like an old school Gen I motor. This is why you see folks make the mistake of trying to put in too much spark lead, etc...
Some of the things folks neglect to check are EGT and BSFC along with AFR. If you take a older non-efficent motor, you often have to run 12:1 to keep the motor alive. While a very efficient motor can run 14:1. Most engines can't run this lean and make their best power curve, but engines that are highly efficient, without any dead areas or fuel air separation spots in cylinder heads, will like to run this lean .
There are no hard fast rules, the motor will tell you what it likes. There is one caveat to this. You can loose power but keep the motor alive with a safe fat tune. You simply leave power on the table.
One thing I also see no one doing is to make their tune fatter at TQ peak, and to roll the A/F leaner as they roll towards HP peak. As an example on an N/A motor going from 12.2 - 12.5 at peak Tq to say 13.5 at peak Hp. You motor needs fuel at peak Tq, but it doesn't need the same ammount of fuel at Peak HP.
Ok, this is a gross generalization, but a nice "safe" number is 11.8-12.2 AFR for a boosted motor. Can you go leaner? Most certainly. You can creep up on leaning the motor down. When you stop seeing power, then back up a few steps. Same with timing. Add timing till you stop seeing gains. As an example, on a stock Z06, there was no HP gain on a dyno from going from 22 to 28 degrees. So, why add timing? All it is is negative work?
You can add timing and lower BSFC.
You can add fuel and lower BSFC.
You can add fuel and raise EGT temps.
You can take away fuel and Lower EGT temps.
See this article:
http://www.maxracesoftware.com/egt_probes.htm
Too often folks get wrapped up in thinking about an Ls1 like an old school Gen I motor. This is why you see folks make the mistake of trying to put in too much spark lead, etc...
Some of the things folks neglect to check are EGT and BSFC along with AFR. If you take a older non-efficent motor, you often have to run 12:1 to keep the motor alive. While a very efficient motor can run 14:1. Most engines can't run this lean and make their best power curve, but engines that are highly efficient, without any dead areas or fuel air separation spots in cylinder heads, will like to run this lean .
There are no hard fast rules, the motor will tell you what it likes. There is one caveat to this. You can loose power but keep the motor alive with a safe fat tune. You simply leave power on the table.
One thing I also see no one doing is to make their tune fatter at TQ peak, and to roll the A/F leaner as they roll towards HP peak. As an example on an N/A motor going from 12.2 - 12.5 at peak Tq to say 13.5 at peak Hp. You motor needs fuel at peak Tq, but it doesn't need the same ammount of fuel at Peak HP.
Ok, this is a gross generalization, but a nice "safe" number is 11.8-12.2 AFR for a boosted motor. Can you go leaner? Most certainly. You can creep up on leaning the motor down. When you stop seeing power, then back up a few steps. Same with timing. Add timing till you stop seeing gains. As an example, on a stock Z06, there was no HP gain on a dyno from going from 22 to 28 degrees. So, why add timing? All it is is negative work?
You can add timing and lower BSFC.
You can add fuel and lower BSFC.
You can add fuel and raise EGT temps.
You can take away fuel and Lower EGT temps.
See this article:
http://www.maxracesoftware.com/egt_probes.htm
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There are no hard fast rules, the motor will tell you what it likes.
what the motor wants, not a specific number that a tuner is shooting for.
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Originally Posted by J-Rod
One thing I also see no one doing is to make their tune fatter at TQ peak, and to roll the A/F leaner as they roll towards HP peak. As an example on an N/A motor going from 12.2 - 12.5 at peak Tq to say 13.5 at peak Hp. You motor needs fuel at peak Tq, but it doesn't need the same ammount of fuel at Peak HP.
One final note: The wide band O2 sensor reads much more accurately when placed in a bung just past the header collector. When shoved up the tailpipe, I've seen them read more than a point leaner than they really are. As a result, people that are tuning for 12.5:1 A/F ratio at the tailpipe are actually giving the motor 11.5:1 when read at the header collector. Something to think about.
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2016 Corvette Z51 M7 Magnuson Heartbeat 2300 supercharger, TSP LT headers, Pat G tuned, 667rwhp, 662rwtq, 191mph TX Mile.
2009.5 Pontiac G8 GT 6.0L, A6, AFR 230v2 heads. 506rwhp/442rwtq. 11.413 @ 121.29mph 1/4 mile, 168.7mph TX Mile
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2013 Corvette Grand Sport A6 LME forged 416, Greg Good ported TFS 255 LS3 heads, 222/242 .629"/.604" 121LSA Pat G blower cam, ARH 1 7/8" headers, ESC Novi 1500 Supercharger w/8 rib direct drive conversion, 747rwhp/709rwtq on 93 octane, 801rwhp/735rwtq on race fuel, 10.1 @ 147.25mph 1/4 mile, 174.7mph Half Mile.
2016 Corvette Z51 M7 Magnuson Heartbeat 2300 supercharger, TSP LT headers, Pat G tuned, 667rwhp, 662rwtq, 191mph TX Mile.
2009.5 Pontiac G8 GT 6.0L, A6, AFR 230v2 heads. 506rwhp/442rwtq. 11.413 @ 121.29mph 1/4 mile, 168.7mph TX Mile
2000 Pewter Ram Air Trans Am M6 heads/cam 508 rwhp/445 rwtq SAE, 183.092 TX Mile
2018 Cadillac Escalade 6.2L A10 Pat G tuned.
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With his car being in SD and not a MAF tune I reconmend tuning it on the street. There no better way to do it IMHO. Ive use a dynojet and I have seen AFR's leaner on the street under load than on the dyno on a WOT. As long as you have a wideband installed in the car tune it on the street. Im using HP tuners with the RTT and the output from the wideband into the scanner
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Originally Posted by Adrenaline_Z
That is the best bit of information in this thread. The final AFR is a product of
what the motor wants, not a specific number that a tuner is shooting for.
what the motor wants, not a specific number that a tuner is shooting for.
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Originally Posted by JMBLOWNWS6
With his car being in SD and not a MAF tune I reconmend tuning it on the street. There no better way to do it IMHO. Ive use a dynojet and I have seen AFR's leaner on the street under load than on the dyno on a WOT. As long as you have a wideband installed in the car tune it on the street. Im using HP tuners with the RTT and the output from the wideband into the scanner ![Happy](https://ls1tech.com/forums/images/smilies/LS1Tech/gr_stretch.gif)
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2013 Corvette Grand Sport A6 LME forged 416, Greg Good ported TFS 255 LS3 heads, 222/242 .629"/.604" 121LSA Pat G blower cam, ARH 1 7/8" headers, ESC Novi 1500 Supercharger w/8 rib direct drive conversion, 747rwhp/709rwtq on 93 octane, 801rwhp/735rwtq on race fuel, 10.1 @ 147.25mph 1/4 mile, 174.7mph Half Mile.
2016 Corvette Z51 M7 Magnuson Heartbeat 2300 supercharger, TSP LT headers, Pat G tuned, 667rwhp, 662rwtq, 191mph TX Mile.
2009.5 Pontiac G8 GT 6.0L, A6, AFR 230v2 heads. 506rwhp/442rwtq. 11.413 @ 121.29mph 1/4 mile, 168.7mph TX Mile
2000 Pewter Ram Air Trans Am M6 heads/cam 508 rwhp/445 rwtq SAE, 183.092 TX Mile
2018 Cadillac Escalade 6.2L A10 Pat G tuned.
LS1,LS2,LS3,LS7,LT1 Custom Camshaft Specialist For custom camshaft help press here.
Custom LSX tuning in person or via email press here.
![](https://ls1tech.com/forums/signaturepics/sigpic210_1.gif)
2013 Corvette Grand Sport A6 LME forged 416, Greg Good ported TFS 255 LS3 heads, 222/242 .629"/.604" 121LSA Pat G blower cam, ARH 1 7/8" headers, ESC Novi 1500 Supercharger w/8 rib direct drive conversion, 747rwhp/709rwtq on 93 octane, 801rwhp/735rwtq on race fuel, 10.1 @ 147.25mph 1/4 mile, 174.7mph Half Mile.
2016 Corvette Z51 M7 Magnuson Heartbeat 2300 supercharger, TSP LT headers, Pat G tuned, 667rwhp, 662rwtq, 191mph TX Mile.
2009.5 Pontiac G8 GT 6.0L, A6, AFR 230v2 heads. 506rwhp/442rwtq. 11.413 @ 121.29mph 1/4 mile, 168.7mph TX Mile
2000 Pewter Ram Air Trans Am M6 heads/cam 508 rwhp/445 rwtq SAE, 183.092 TX Mile
2018 Cadillac Escalade 6.2L A10 Pat G tuned.
LS1,LS2,LS3,LS7,LT1 Custom Camshaft Specialist For custom camshaft help press here.
Custom LSX tuning in person or via email press here.
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fatter at peak torque, lean out until you approach max RPM/max HP then fatten up again. thats how I do it, and with FI setups I aim for normalized 11-11.5, to be safe. theres more power to be had...but not worth the risk on anything but an all out race car.
as people have already mentioned, with N/A you can go leaner in general with no worries. 12-12.5
I also like to run a little more timing when its a little rich. the extra fuel helps prevent detonation, and the extra timing makes up for the loss of power from the slightly rich ratio. I run 23deg with a cam and forced induction, and get no knock.
as people have already mentioned, with N/A you can go leaner in general with no worries. 12-12.5
I also like to run a little more timing when its a little rich. the extra fuel helps prevent detonation, and the extra timing makes up for the loss of power from the slightly rich ratio. I run 23deg with a cam and forced induction, and get no knock.
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One final note: The wide band O2 sensor reads much more accurately when placed in a bung just past the header collector.
Some cat systems (3-way cats) inject air into the exhaust to reduce NOx.
Any reading taken after a cat (especially a 3 way is skewed).
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Great info guys! And just when you think you know it all..Jarrod as usual you've given me a lesson in these new Gen Motor Engineering...
BTW we did the intial tuning on the street...Thank god I live in an area I can do that. 4th gear roll ons need some room for sure. This did cut down on the dyno tuning and time involved.
We did the final tuning on a Mustang Dyno at Conleys. I've always felt the car was too rich and apparently I was correct. Damn I hate to see more HP still waiting to be tapped...
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BTW we did the intial tuning on the street...Thank god I live in an area I can do that. 4th gear roll ons need some room for sure. This did cut down on the dyno tuning and time involved.
We did the final tuning on a Mustang Dyno at Conleys. I've always felt the car was too rich and apparently I was correct. Damn I hate to see more HP still waiting to be tapped...
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Last edited by DJ's99SS; 08-30-2006 at 11:12 AM.
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Originally Posted by Patrick G
My car is SD tuned as well, but I don't like doing long 4th gear pulls on the street. 7000 rpm in 4th gear for me is over 150mph! 2nd or 3rd gear pulls on the street don't load the motor as well as 4th gear pulls. That's why I use the Mustang dyno. 4th gear pulls on the MD take as long as 4th gear pulls on the street, I can make instant, real-time timing and fuel changes with my EFI Live Roadrunner Emulator, and I never have to worry about speeding tickets or accidents. In my experience, there is no change in A/F ratio going from the Mustang Dyno to the street.
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