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> Air/Fuel ratio, is there a quick answer?
malcolm2
post Mar 27 2017, 03:16 PM
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I made it home.... 800 + mile weekend trip. I don't think I will go that far again until I get some new padding for my seats. (IMG:style_emoticons/default/driving.gif) (IMG:style_emoticons/default/driving.gif)

As far as the A/F goes... I filled up with pure gas, 89 oct I believe it was. So the 1st 330 miles started with maybe 25% 87 oct e10 + 75% 89 oct pure.

MPG (best numbers I have ever recorded)
tank 1: all interstate: 337.5 / 11.25= 30 mpg
tank 2: 100 miles of city: 314.2 /9.99 = 31.4 mpg
tank 3: 151 miles of interstate: xxx/xx = still on 1/2

I-40 from Nashville to Asheville has quite a few hills, some 4 to 5 miles long.

The car ran very well. I visually logged @ 12.7 a/f cruising on flat ground at about 3400 rpm. Up the hills still at 3400 rpm, CHT reached 380-ish and the a/f evened out at 12.5. Oil temps were steady at 210.

My total a/f interstate range for the most part was 12.3 to 13. Once thru the mountains with only about 20 miles to go, I noticed there were times it was running richer. I saw some 12.0's even 11.8 for brief times.

City driving on Friday, it would idle at 14.6 then stop-to-stop up to 4th gear and 3000+ rpm I say I saw 12.5 - 13.

I did not see the rich numbers yesterday. the range was about like the City driving 12.3 -12.8 all day on 87 oct e10 fuel. 3400 to 3800 rpm 70 - 80 mph.

Unless someone thinks I am out of whack, I think I may not tweek any further.

I will also edit and add a spark plug photo for Tim.... (IMG:style_emoticons/default/shades.gif)
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malcolm2
post Mar 27 2017, 04:33 PM
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Ok what do you think? Maybe 1000 miles with this new AFM and it's set up.

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timothy_nd28
post Mar 27 2017, 05:10 PM
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I got nothing. My work with you is done.
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Mark Henry
post Mar 27 2017, 05:17 PM
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I'd say that plug is a tad hot, what number is it? Brand?
What are you running for total advance?

I'm looking for beige or tan colour on the insulator, your insulator is too white. Or is it just the pic?

Edit: could be my one monitor, on the other one it looks about right. As long as the insulator doesn't have a gloss finish appearance it should be correct.
I run two monitors but one is better than the other.
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malcolm2
post Mar 27 2017, 07:11 PM
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QUOTE(Mark Henry @ Mar 27 2017, 06:17 PM) *

I'd say that plug is a tad hot, what number is it? Brand?
What are you running for total advance?

I'm looking for beige or tan colour on the insulator, your insulator is too white. Or is it just the pic?

Edit: could be my one monitor, on the other one it looks about right. As long as the insulator doesn't have a gloss finish appearance it should be correct.
I run two monitors but one is better than the other.


They are NGK BR5ES. It was cylinder #2. Have not checked the timing in a while. I guess I should.

I thought it was pretty white too. Don't remember seeing one that white. I figured that was a good thing. It was not shiney.

Thanks
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Olympic 914
post Mar 28 2017, 07:55 AM
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Spark plugs are an easy change, you could try NGK 6 in there, its one step colder.

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72hardtop
post Apr 24 2017, 05:38 AM
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This is a great graph for air cooled engines:

https://www.thesamba.com/vw/gallery/pix/1463782.jpg


14.7-15 or so is the 'No go zone' danger. Shoot for ~12.5 - 13.0 WOT/Accelerating and while at cruise (part throttle cond) 16-17 AFR

Use an LM-2 wide band

16-17 AFR at cruise (part throttle cond) is cooler running (EGT's/CHT's) than 13:0-13:5 same scenario.
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72hardtop
post Apr 24 2017, 05:49 AM
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QUOTE(Mark Henry @ Mar 5 2017, 05:55 AM) *

Yes 15:1 cruise is too lean for an aircooled 14:1 would be the max and even then I'd want a good headtemp gauge to be sure they're not getting too hot.

That chart might be OK for a watercooled, but not aircooled. WC big advantage is they can control head temps way better than air cooled.

Aircooled has a much narrower burn AFR range.
This would be my aircooled chart;

About 11:1 is the max for rich burn
WOT power between 11.5 and 13
Max performance WOT 12.3 to 13 maximum
Lean burn no higher than 13.5-13.7, nickies can run 14:1-14.3


The exception to the above is decel, AFR on decell is of no concern, of course it's a high reading, you just took away all the fuel, but no load so it's not producing heat.

You can run richer than 11:1 without really hurting the engine, but your power and tune goes to poop.
Anything over stoich you better have a damn good head temp gauge to monitor your temps, you are getting into dangerous territory.
As you head temps go over 350f you will start to lose power as a heat soak condition starts to set in.
Running 17-18:1 and you will have a hole in a piston PDQ.

Basic rule on heat temp and heat soak is you can go over 350f on a long hill, as long as the temps recover on the downside. Once the temps are not recovering on the downside of the hill you have a heat soak issue. Even a cheap VDO gauge you can easily see this heat soak/no recovery condition.
Head temps consistent 325f is about perfect, 350F is OK, but I don't want to see much more for long periods of time.
On my LN nickies I don't see much over 300F unless I'm really hammering it on a hot day.


Well in a 914 one may not see much over 350F or so if everything is dialed in. But temps over 350F are not for much concern. It's when you go over 400+F then start worrying.

As for AFR's once you start pushing beyond 15:1 the EGT's go down. Why? Simple you are closing the burn (fuel off). The below chart shows the relations between EGT, CHT, HP and ICP. Peak EGT is ~14.7-15:1

During 'cruise' get into the 16-17AFR for cooler running. Part throttle cruise is NOT a load condition. Ones foot dictates load. If you're running around during cruise at 13:0 - 13:5 you are wasting fuel and running hotter EGT's and CHT's than you would be if you were running 16-17AFR at cruise (part throttle).

https://www.thesamba.com/vw/gallery/pix/1463782.jpg
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VaccaRabite
post Apr 27 2017, 09:13 AM
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QUOTE(timothy_nd28 @ Feb 7 2017, 10:47 PM) *

350 degrees is not normal, atleast I hope not. Remove the thermostat cable and repeat the test.


350 going up hill at 70 sounds pretty good to me, especially if the CHT is reading cyl 3 and you are in 5th gear.

My car always used to be approaching 400 on long highway hills in 5th. It would be pulling like a champ, but getting hot. I learned to downshift to 4th at the base and keep that air moving. That said I never had valves stretching on me. Now that I'm in EFI and have a wideband I'm looking forward to see if my engine stays on the hot side or if its now going to run a bit cooler. But I'd love to see 350 at 70MPH running up some of the long ass hills here in PA.

Zach
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malcolm2
post Apr 28 2017, 06:29 AM
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QUOTE(Vacca Rabite @ Apr 27 2017, 10:13 AM) *

I'd love to see 350 at 70MPH running up some of the long ass hills here in PA.

Zach


on my daily drive I have a long, low hill that I have been comparing each day.

On my last trip to SC there is a mountain to climb. It seems like it is 5 miles long and very steep. My VDO CHT under #3 needle moves to what I would call 375 in 5th gear on that "hill".

I filled up with 90 octane pure gas yesterday. This morning, on the "hill" maybe 75 mph the A/F was 12.2-ish and cht was dead on 350.

So the A/F seems a bit rich, but still in range. Earlier in the week with 93 oct, E-10 it was reading 12.7 on my daily hill.
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jpapatrout
post May 6 2017, 04:24 PM
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I just saw an ad for an AFR from Innovate that monitors 2 sensors. They say left and right banks on a V8 engine may run different numbers. Does anyone have experience/opinions on this? Could this be helpful?
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72hardtop
post Oct 29 2018, 02:19 AM
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QUOTE(malcolm2 @ Mar 27 2017, 03:33 PM) *

Ok what do you think? Maybe 1000 miles with this new AFM and it's set up.

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Was it allowed to idle prior to pulling the plug/ It matters even the slightest. Also with today's ethanol blended fuel E10+ it takes a few thousand miles of seasoning the plugs before you can use them as a gauge for AFR.


Load = WOT

Part throttle is NOT load

Cruise = part throttle condition

An AFR of 16-17 at cruise (part throttle cond) is COOLER running than at an AFR of 13:0 - 13:5

With respect to jetting....Get above (14-15AFR range) when on the progression and below (14-15AFR when on the main jets. 90% of ones driving is on the progression circuit (idle jets).

The following chart shows this....

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72hardtop
post Oct 29 2018, 02:29 AM
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QUOTE(timothy_nd28 @ Feb 6 2017, 08:41 AM) *

(IMG:style_emoticons/default/agree.gif) Aircooled engines may need to run slightly more rich than the water coolers


Incorrect.

Under load? Yes.

At cruise? No

Cruise = part throttle condition. One is not at WOT/load under that scenario.

Nothing wrong with 16-17 AFR with a cracked throttle. Throttle position dictates load.
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Chi-town
post Oct 29 2018, 10:36 AM
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There is no "short answer" for this question.

There are some basic references for non forced induction though.

WOT = 12.7-13.2 under heavy load
Cruise = 13.7-14.7 under light load
Idle = Hot-13.0-15.0 / Cold- 11.5-12.5

Now keep in mind all of these are dependent on timing.

You need to know where your base timing is set, what your advance curve looks like and your peak advance.

This is where those old SUN distributor machines come into play.

You need to measure the weights and spring tensions, the diaphragm movement per inch of vacuum in the actuator.

Even off the shelf reman distributors often have the wrong curve as they mix and match weights and springs.

Now that you've got your distributor curved correctly, timing set, and your wideband O2 installed Now you can tune your carbs or check your F.I. to make sure it's operating correctly.

Reading plugs is a good back up to the wideband and will tell you if you're too aggressive or not aggressive enough with timing.

Here's some good reading on that:
https://honda-tech.com/forums/forced-induct...%2A%2A-3063102/

Remeber always make minor adjustments and don't get crazy aggressive and your engine will last a long time.
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72hardtop
post Nov 1 2018, 12:04 AM
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QUOTE(Chi-town @ Oct 29 2018, 09:36 AM) *

There is no "short answer" for this question.

There are some basic references for non forced induction though.

WOT = 12.7-13.2 under heavy load
Cruise = 13.7-14.7 under light load
Idle = Hot-13.0-15.0 / Cold- 11.5-12.5

Now keep in mind all of these are dependent on timing.

You need to know where your base timing is set, what your advance curve looks like and your peak advance.

This is where those old SUN distributor machines come into play.

You need to measure the weights and spring tensions, the diaphragm movement per inch of vacuum in the actuator.

Even off the shelf reman distributors often have the wrong curve as they mix and match weights and springs.

Now that you've got your distributor curved correctly, timing set, and your wideband O2 installed Now you can tune your carbs or check your F.I. to make sure it's operating correctly.

Reading plugs is a good back up to the wideband and will tell you if you're too aggressive or not aggressive enough with timing.

Here's some good reading on that:
https://honda-tech.com/forums/forced-induct...%2A%2A-3063102/

Remeber always make minor adjustments and don't get crazy aggressive and your engine will last a long time.


WOT = 12.7-13.2 under heavy load
Cruise = 15.5-17:0 under light load (better MPG's)

14:0 - 15:0 is where the highest EGT's & CHT's will be. Get above that zone when on the progression circuit and below it when on the mains (WOT).

Idle isn't where we/one drives so it's out of the pic.

Reading plugs takes time. With new plugs you need a couple thousand miles for them to get seasoned.
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914Toy
post Nov 1 2018, 09:13 AM
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QUOTE(jpapatrout @ May 6 2017, 03:24 PM) *

I just saw an ad for an AFR from Innovate that monitors 2 sensors. They say left and right banks on a V8 engine may run different numbers. Does anyone have experience/opinions on this? Could this be helpful?


I have one of these with my 911 engine headers. Info is very helpful tuning carbs. Do not cut the harness to fit your application.
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