Topic: AFR testing & tune?

[Don R]

 I won an auto meter contingency payout racing and got an AFR meter. I made a test probe and put the portable air fuel meter probe in the blue green K0, it's a cruisin image 836 kit with a mild port job and kenny harmon F cam, ape springs and retainers, K0 carbs, stock jets, no number yamiya pipes, stock air box and filter.  With the baffles out it blubbered at steady cruise rpm with them in it's better. I assumed part throttle lean but it's the opposite.
   I put the meter probe through a spare drilled baffle on cyl#2.
   
    Edit, it's become clear my numbers from the o2 were skewed for whatever reason so any conclusions I reached using it were incorrect. Jetting the old fashioned way (asking and trying) yielded better results. 
    Thanks again for the advise guys. (calling BS when I was clearly off track)

[Don R]

 The spare parts bin yielded a set of 130 mains, that was always our go to size way back when putting on a header but may prove too big a change. I have 3  #32 pilot jets, one twisted off during removal. I was thinking the gold K0 came with #40 pilots, that thing started with no choke.
 Edit, I'm off a few on the pilot jet size.

[scottly]

  At 80mph and wide open throttle it reads around 17-1 lean

How was the bike running? Was it accelerating properly, given the gear you were in?

[Don R]

 It was pulling good Scottly, if it's really that lean I'd expect blue pipes except I coated them inside.  The heads were pretty fresh and it got new copper crush washers and my nicest clamps so air leaking in isn't likely but I'll check another cylinder or two.
  I found 130 and 135 main jets, my set marked 125 set turned out to be 112.5.  42 pilots were in the stock 750 with 4-2's I may try them in it too. I may set it on a fast idle on the center stand and check all cylinders at low rpm's.
 It was also pretty lean at idle, the internet says stay 15-1 or richer to get a good idle. It'll be fun to adjust the pilot screw with it idling. Maybe I'll understand this thing a little better when I'm done playing.
  I'm wondering how the long exhaust duration on this road race cam is affecting the afr.
  Well I'm rambling, time to sleep, grandkids at 5:30 am.

[scottly]

It wouldn't pull good with a 17:1 AFR @ WFO, Don.

[Don R]

  I re-checked cyl# 2 and at the far point of the ride I moved to a different cylinder this morning, got different numbers. The part throttle cruise is still at 10-1.  WOT looked better on #3, it was reading 14.5 to 15 to one but I wasn't able to get up to 80 and hold it open on the road I was on today. 
   Either #2 is running out of fuel at sustained WOT, the left side is, or I just wasn't able to use it up on the road I was on today.  The tank cap vent is clear and recently taken apart, rebuilt 2 outlet petcock and proper Honda 5.5mm fuel hose run downhill with no filters. I'll check the bowl and screen today too.   
Finally, it has a Pamco and I recently checked timing and dwell.
 Edit, it rained and I put it away. Then I spent time with grandkids and took them home.

[Don R]

  I dropped the jet needles to the top groove, and left everything else as is.
 The lean high rpm is better, I'm still on #3 though I'll move back to #1 or 2 and check again,  The part throttle cruise sounds way better, no more blubbering but it's still reading rich, it does go leaner than 10-1 at times which I like.  Next test I'll go back to left side pipes and try the K&N air filter swap just to see if my old cheapie filter is causing air flow issues. 
  Some gasohol would help with the fat cruise A/F ratios, but not in my wrinkle tank. 
   It occurs to me this bike came with a 4-1 when I got it, I didn't re-jet when going back to the stock 4-4 type pipes.  I now think the lean numbers were fuel delivery issues, petcock dirt and a fuel line hump. Also, you don't look at the meter for very long at speed.
  A quick ride checking #1 looks rich through the range. I've probably wrecked a set of plugs by now.

 Edit, it had 120's in it so I dropped in a nice set of 110's I had on their original unmodified emulsion tubes. It's getting a lot better afr numbers, cruise at 10.5 up through 15-1 or so at it's leanest. When going through the gears I'm seeing 12.5 to 15-1  I later remembered the 112.5 jets I have too.  I think the plugs have recovered nicely.  Rideability is much better, it is cooler and dark out now. It has a tiny cackle on decell.
 

[scottly]

Don, I suspect you aren't getting an accurate reading from your test probe. The dyno uses an air siphon to ensure exhaust gasses are flowing to the sensor. There is a flow meter to calibrate for a certain amount of flow.

[Don R]

 It's showing a full range of afr's as I've turned off the fuel or leaned into the choke, so it isn't just reading lean or rich. I'm relying on back pressure from the baffles to force the flow exhaust through the probe tube, it's true I don't know how much is flowing through except it changes fairly quickly with rpm.
  When I roll off throttle it reads lean right away. Maybe I'll build an outlet chamber with the sensor and a tailpipe after that.
   After the 110 jet install the bike has now stopped misfiring at part throttle cruise so I'm confident I'm on the right track. I've loaned out my pin gauges so I can't confirm the jet sizes except by number. I've seen drilled ones before.
  On our jr. dragster engines installation of a .563 stroker crank on a previously stock stroke engine required a smaller Mikuni main jet so it's not a totally foreign concept to me. 

[Don R]

 I read a missfire will show as an o2 increase, in this case with 4-4's I would need to check each cylinder to look for one. Hopefully I can get the dragster winterized and have some decent weather to do some more testing. 40* air may be a  little misleading.

[Nicklopic]

I think using a wideband is probably the best way to tune assuming you’re getting good readings.
What does your probe set up actually look like? Sniffer style ones can pull fresh air in and throw your readings off but under pull gallop ripping on it that shouldn’t be an issue.

From the research I did before tuning, WOT should for 11.5-11.8 to 1. You can go leaner, like 12-12.5 but the extra fueling helps bring cylinder temps down (taken from an interview with a Porsche endurance race team running 24 hour races with air cooled Porsche’s)
Cruising stay around stoichiometric, 13-15 in that range.
Idle like 13-14.
My bikes on the rich side at idle, like 12:1, I’ve just been too lazy to pull the stupid pressed in slow jets out and step down a size lol

[scottly]

From the research I did before tuning, WOT should for 11.5-11.8 to 1.

Wrong!!! The AFR for max power at WOT is 12.8-13.2:1.
What's the difference between a porcupine and a Porsche?




The porcupine has the pricks on the outside.

[Tracksnblades1]

From the research I did before tuning, WOT should for 11.5-11.8 to 1.

Wrong!!! The AFR for max power at WOT is 12.8-13.2:1.
What's the difference between a porcupine and a Porsche?




The porcupine has the pricks on the outside.

I thought 12.6 a/f straight real gasoline was the Lambda Max Power ratio.?  Adding ethanol lessens the Max Power A/F ratio as the percentage of ethanol increases….. naturally aspirated….

[Tracksnblades1]

I read a missfire will show as an o2 increase, in this case with 4-4's I would need to check each cylinder to look for one. Hopefully I can get the dragster winterized and have some decent weather to do some more testing. 40* air may be a  little misleading.

Don, what A/F ratio are you dialing in on your naturally aspirated  gasoline drag rail…
Curiosity and the cat thing…😜

[Nicklopic]

I never said it was for max power, I guess I should have justified more. I’m suggesting those number because the extra fuel helps bring cylinder temps down, and helps keep things alive and run cooler. Specifically mentioning the Porsche part because the race cars the team was running are all air cooled and a reasonable comparison to air cooled bike motors. There’s no water jackets to pull heat away.
This is the article/interview I was mentioning.

“We typically run these air cooled motors around 11.5:1 AFR at WOT. This helps keep the temperature under control. You can get more power by running a bit leaner, but there's no point in that if the motor can't finish the race.”
www.masterenginetuner.com/air-fuel-ratio-tuning-tips.html

[Tracksnblades1]

I never said it was for max power, I guess I should have justified more. I’m suggesting those number because the extra fuel helps bring cylinder temps down, and helps keep things alive and run cooler. Specifically mentioning the Porsche part because the race cars the team was running are all air cooled and a reasonable comparison to air cooled bike motors. There’s no water jackets to pull heat away.
This is the article/interview I was mentioning.

“We typically run these air cooled motors around 11.5:1 AFR at WOT. This helps keep the temperature under control. You can get more power by running a bit leaner, but there's no point in that if the motor can't finish the race.”
www.masterenginetuner.com/air-fuel-ratio-tuning-tips.html

Good article…he took the long way around the track to express the pit falls of lean best power..😜
Check out the cylinder head differences that show up on supercharged methanol drag BBC/HEMI.
Eyeball that .9/1 air fuel ratio, yes (point 9)  for supercharged nitro.  Puts in to perspective what happens if them dual 44amp magneto arc welders can’t get it all lit…😜

[NitroHunter]

Our 21 gpm .9/1 A/F indicators are always spot-on... 

[Tracksnblades1]

Our 21 gpm .9/1 A/F indicators are always spot-on... 

😳😩

All in less than a second …?

[Nicklopic]

Sweet Jesus that’s a lot of juice flowing lmfao
And yeah it definitely takes some time for him to get on with it but It seemed like a snippet of a longer interview so they’re were back and forth a bunch

[Don R]

 We're using a target A/F of 10.8 but have oxygenated fuel. Q16 VP. I'm looking at E85 race fuel next year. Pump E85 isn't consistent from batch to batch so I'll either get E98 and blend it myself with no lead race gas or buy a barrel of premix. The VP is close to $20 a gallon and will probably get there by next season.

[scottly]

I never said it was for max power, I guess I should have justified more. I’m suggesting those number because the extra fuel helps bring cylinder temps down, and helps keep things alive and run cooler. Specifically mentioning the Porsche part because the race cars the team was running are all air cooled and a reasonable comparison to air cooled bike motors.

I fail to understand the reasoning that in order to keep a fragile Porsche alive during endurance racing involves de-tuning the engine by running an excessively rich mixture at WFO? After all, the whole reason the throttle is WFO is because you are asking for maximum power??!! Rather than choking the engine up with carbon deposits and diluting the oil with fuel, it might be better to back off the throttle a bit. Also, your example has Nothing to do with our bikes.
Have a look at this dyno chart: at 7000 RPM, one run is with an AFR in the high 12:1 range, while the other is in the high 11:1 range. There is a difference of about 8% in the HP, which is no small amount.

[scottly]

 We're using a target A/F of 10.8 but have oxygenated fuel. Q16 VP. I'm looking at E85 race fuel next year.

Don, I asked VP about the desired A/F of their oxygenated (MTBE?) racing gas a while back, and they responded that it was the same as gasoline, although re-jetting might be required due to the difference in specific gravity. Your target should still be in the range of 12.8-13.2 for your dragster, unless you are sandbagging.  

[Don R]

 That's correct, 12.8, I had a brain fart, we talked about 10.8 with spray for Top Dragster didn't do it. My engine guy likes to keep it on the safe side, so said 12.8 at WOT. VP fuel says 13.0 to 13.4.  I had a Holley rep tuning it the first time out. He was testing the throttle stop settings, we offset 20% when it goes on the throttle stop since it is a separate throttle blade set under the efi not a linkage stop. The TPS is seeing WOT.  With the open headers we are in open loop at low rpm because the o2 sensor is seeing a lot of air coming back up the header pipe between exhaust pulses. No room for 18" long collectors. We also go open loop above a set rpm for consistency. In closed loop it tunes it's self and fights our prediction usually making us too quick.
 We launch at 4800 rpm, go wide open for .1 seconds to clear the beams, shift at .7  and stay on the throttle stop for around 2 to 2.2  seconds depending on the density altitude, rpm pre-set at 4200. Then it relaunches wide open in high gear and the converter does the rest. If I set the timer right it will run 8.90 around 171 to 175.

[dragracer]

Dang. 175mph on the stop. Wow. I'm 145mph  WOT, end to end running 8.90 on my bike.

[Don R]

 It's been 7.30's at 182 but it was perfect conditions. Our 383" pulled hard off the line, this 567" pulls all the way to the stripe. If I had $3 or 4 K to waste I'd run it on the mile. Tires, wheels and gears $$ wow. 

[Don R]

 I went back to what's known to work and now see how far off base I went jetting this beast. The leaky as F. #1 carb has caused me a boatload of grief and a few spark plugs. It was well behaved today, I may still be suffering from painter induced sandblast grit in the fuel tank even after multiple cleanings. One float bowl showed signs of sediment.