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> A/F readings, What do the experts think?
Black22
post Aug 19 2012, 04:47 PM
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Hey all,

I've got a 1911cc motor with about 250 miles on it. KB pistons, stock cam and L-jet, with 1.8l heads modified to 2L valve sizes. Compression is 8.5:1. Running Brad Penn 20/50.

Car was recently running way rich and got VERY poor gas mileage. I hooked up with Joe Sharp, (thanks again Joe!) and he let me use his LM-1. I tried to dial my L-jet in and got pretty close. I've since purchased and installed an Innovate MTX-L AFR kit. Gauge works great! Here is my readings as of now and after MUCH tweaking this is my dilemma.

AFR stats:
Idle= 12.7
WOT= 9.7-10.2 (it will hit these readings regardless of RPM)
Decel= 14.8-15.9

Timing is set @ 7.5* @ ~900rpm with vacuum ports disconnected and plugged.

WOT seem rich still, but now my motor runs hotter. I know I'm leaning the motor out and should expect higher oil temps but I was running about 190-200 and now I'm running 210-220. I'm also running an external 72 plate oil cooler w/fan!

I've adjusted the timing to experiment, and had it at 9.5* adv. and it ran cooler at idle but the temp went back up while driving.

It seems I have some more adjustments to get it even leaner, but that's just going to raise the temps right? (IMG:style_emoticons/default/confused24.gif)

What do you guys think and what should I do (if anything) next?
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ChrisFoley
post Aug 19 2012, 05:21 PM
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You need to adjust the wiper inside the AFM to lean it out across the entire rev range.
Someone just posted a link in another thread to a very good explanation of how to adjust L-Jet.
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Black22
post Aug 19 2012, 05:28 PM
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QUOTE(Racer Chris @ Aug 19 2012, 04:21 PM) *

You need to adjust the wiper inside the AFM to lean it out across the entire rev range.
Someone just posted a link in another thread to a very good explanation of how to adjust L-Jet.


I think you are referring to me. I posted that link to the article. I'm doing all adjustments based on the readings and that article.

What do you think about the temps? I don't have a CHT gauge but I can feel the heat coming off the engine and it seems WAY hotter.
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ChrisFoley
post Aug 19 2012, 05:41 PM
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You should get a CHT gauge.
Leaning out the mixture will have a greater effect on CHT than oil temp.

I want my oil to get up to 210F to fully burn off volatile impurities.
And I have to work pretty hard to get it that hot.
As long as you have at least 10psi per 1K rpm its not too hot.

I'm running BP 10/30 in my 1911 with D-Jet. No problem with oil temp/pressure or CHT. I've driven hard on 100 degree days and had no issues.
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rwilner
post Aug 19 2012, 06:00 PM
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::Disclaimer -- I am not a member of the expert community, only the peanut gallery::

Gas mileage is principally determined by AFMs at cruise, at least on the highway. What are you running at cruise?

My car likes 13.5:1....a good compromise between fuel efficiency and engine head temps. I agree with Chris -- if you're messing with AFR you should have a CHT gauge installed, otherwise you're guessing.
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Black22
post Aug 19 2012, 06:35 PM
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QUOTE(rwilner @ Aug 19 2012, 05:00 PM) *

::Disclaimer -- I am not a member of the expert community, only the peanut gallery::

Gas mileage is principally determined by AFMs at cruise, at least on the highway. What are you running at cruise?

My car likes 13.5:1....a good compromise between fuel efficiency and engine head temps. I agree with Chris -- if you're messing with AFR you should have a CHT gauge installed, otherwise you're guessing.

At cruise w/ partial throttle just to maintain 70mph I'm around the 11.8 to 12.5 area depending on load.

I would love a CHT, but baby boy will be here in 2 weeks and Momma will kill me if I spend another dime on this ride! (IMG:style_emoticons/default/sad.gif)
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brant
post Aug 19 2012, 08:18 PM
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too rich...

with only 250miles on the rebuild you may need to do this more than once when the rings are fully seated...


but lean it out.
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aircooledtechguy
post Aug 19 2012, 09:55 PM
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X3 on the CHT gauge. Oil temp is VERY slow reacting compared to CHT. Your heads will be long cooked before the oil temp begins to register a problem. A $100 CHT gauge = 5 cans of formula or 4 packs of pampers, or. . . Better get it NOW before you have no $$$ at all. (IMG:style_emoticons/default/poke.gif)
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Black22
post Aug 20 2012, 04:25 PM
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QUOTE(aircooledtechguy @ Aug 19 2012, 08:55 PM) *

X3 on the CHT gauge. Oil temp is VERY slow reacting compared to CHT. Your heads will be long cooked before the oil temp begins to register a problem. A $100 CHT gauge = 5 cans of formula or 4 packs of pampers, or. . . Better get it NOW before you have no $$$ at all. (IMG:style_emoticons/default/poke.gif)

Alright, alright, I gave in and ordered the same one McMark posted about in another thread.
They say these things show temp changes immediately. Will I be able to adjust timing and see this thing react?

I'm not going to run the car until I install this gauge. Thanks for the help guys!
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76-914
post Aug 20 2012, 06:38 PM
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Congratulations to you and your beautiful wife. Say, wasn't Thomas' "Hangover Run" about 9 mo's ago. (IMG:style_emoticons/default/shades.gif) Good call on ordering the CHT gage. Yes, the resulting head temp changes are read and displayed quickly but not as quick as EGT's. Have any of you guy's ever tried to set your AFR using the EGT readings on these engines?
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ChrisFoley
post Aug 20 2012, 07:03 PM
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QUOTE(76-914 @ Aug 20 2012, 07:38 PM) *

Have any of you guy's ever tried to set your AFR using the EGT readings on these engines?

I use EGT, not an AFM in my race car. It is the best way to measure individual cylinder behavior at WOT, but much less useful when load is changing constantly.
Airplane pilots use EGT, not O2 measurement, because their engines operate at constant throttle.
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Black22
post Aug 20 2012, 08:45 PM
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QUOTE(76-914 @ Aug 20 2012, 05:38 PM) *

Congratulations to you and your beautiful wife. Say, wasn't Thomas' "Hangover Run" about 9 mo's ago. (IMG:style_emoticons/default/shades.gif) Good call on ordering the CHT gage. Yes, the resulting head temp changes are read and displayed quickly but not as quick as EGT's.



Thanks Kent! Yes it was about 9 months ago wasn't it (IMG:style_emoticons/default/idea.gif)

Was hoping to see you at the carb clinic this weekend, but the wife will be have labor induced on the 30th! I still might try to sneak out, if I get the gauge by Thursday and get my motor tuned better on Friday. I also have chores as well.

Wish me luck!
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rwilner
post Aug 21 2012, 11:17 AM
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QUOTE(Black22 @ Aug 20 2012, 06:25 PM) *

Alright, alright, I gave in and ordered the same one McMark posted about in another thread.


IF this is the micro 1000 gauge, it's the same one I have and it works great.

QUOTE

They say these things show temp changes immediately. Will I be able to adjust
timing and see this thing react?



Yes -- it reacts pretty much instantly.
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Black22
post Aug 21 2012, 11:21 AM
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QUOTE(rwilner @ Aug 21 2012, 10:17 AM) *

QUOTE(Black22 @ Aug 20 2012, 06:25 PM) *

Alright, alright, I gave in and ordered the same one McMark posted about in another thread.


IF this is the micro 1000 gauge, it's the same one I have and it works great.

QUOTE

They say these things show temp changes immediately. Will I be able to adjust
timing and see this thing react?



Yes -- it reacts pretty much instantly.


Yes, it is the Micro1000 gauge. Thanks, that's what I wanted to hear. (IMG:style_emoticons/default/beer.gif)
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