How lean can you lean a Type4 for steady state cruise...
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- Old School!
- Location: Little Rock, AR
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How lean can you lean a Type4 for steady state cruise...
How lean can you go on a Type4 for extended steady state cruise? I am mostly done with my fuel map, and now need to start turning for economy at 45,55,60 and 65mph.
My latest backroads highway run (45-55-60-65 cruise) run averaged 12.5mpg, with 13:1 AFR. Granted, I have a lot of racks, and there was a lot of headwind, but I feel like I should be able to go leaner...
If this image is to be believed, and various articles accompanying it, I should be able to go way leaner, as long as the engine does not buck due to load...
Thoughts?
My latest backroads highway run (45-55-60-65 cruise) run averaged 12.5mpg, with 13:1 AFR. Granted, I have a lot of racks, and there was a lot of headwind, but I feel like I should be able to go leaner...
If this image is to be believed, and various articles accompanying it, I should be able to go way leaner, as long as the engine does not buck due to load...
Thoughts?
1981 Volkswagen Vanagon Westfalia - air-cooled Type4 1970cc CV (hydraulic lifters, 42x36 valves, stock cam, microSquirt FI with wasted spark ignition)
1993 Ford F-250 XL LWB Extended Cab 7.3L IDI
1993 Ford F-250 XL LWB Extended Cab 7.3L IDI
- airkooledchris
- IAC Addict!
- Location: Eureka, California
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Re: How lean can you lean a Type4 for steady state cruise...
Your Dakota Digital CHT gauge will tell you once you've gone too lean. =)
1979 California Transporter
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- Old School!
- Location: Little Rock, AR
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Re: How lean can you lean a Type4 for steady state cruise...
Brilliant.airkooledchris wrote:Your Dakota Digital CHT gauge will tell you once you've gone too lean. =)
1981 Volkswagen Vanagon Westfalia - air-cooled Type4 1970cc CV (hydraulic lifters, 42x36 valves, stock cam, microSquirt FI with wasted spark ignition)
1993 Ford F-250 XL LWB Extended Cab 7.3L IDI
1993 Ford F-250 XL LWB Extended Cab 7.3L IDI
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- Old School!
- Location: Seattle, WA./HB. Ca./Shizuoka, Japan
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Re: How lean can you lean a Type4 for steady state cruise...
Don't run stoich.
1972 Westy tintop
2056cc T-4 - 7.8:1 CR
Weber 40mm Duals - 47.5idles, 125mains, F11 tubes, 190 Air corr., 28mm Vents
96mm AA Biral P/C's w/Hastings rings
42x36mm Heads (AMC- Headflow Masters) w/Porsche swivel adjusters
71mm Stroke
Web Cam 73 w/matched Web lifters
S&S 4-1 exhaust w/Walker 17862 quiet-pack
Pertronix SVDA w/Pertronix module & Flamethrower 40K coil (7* initial 28* total @3200+)
NGK BP6ET plugs
002 3 rib trans
Hankook 185R14's
2056cc T-4 - 7.8:1 CR
Weber 40mm Duals - 47.5idles, 125mains, F11 tubes, 190 Air corr., 28mm Vents
96mm AA Biral P/C's w/Hastings rings
42x36mm Heads (AMC- Headflow Masters) w/Porsche swivel adjusters
71mm Stroke
Web Cam 73 w/matched Web lifters
S&S 4-1 exhaust w/Walker 17862 quiet-pack
Pertronix SVDA w/Pertronix module & Flamethrower 40K coil (7* initial 28* total @3200+)
NGK BP6ET plugs
002 3 rib trans
Hankook 185R14's
- Amskeptic
- IAC "Help Desk"
- Status: Offline
Re: How lean can you lean a Type4 for steady state cruise...
Little late to the party, but the graph is showing a drop in CHTs as the mixture leans.airkooledchris wrote:Your Dakota Digital CHT gauge will tell you once you've gone too lean. =)
When I was experimenting with mtcamper's AFM on the highway while he drove, we discovered the same thing, as I leaned the wiper, the CHTs would drop. It appears that the work load has as much to do with CHTs as anything. Whenever I reduced the engine's output by egregious tomfoolery at the AFM, the CHTs would drop.
It is a delicate thing, this CHT/EGT/HP/AFR map.
Colin
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles
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- Old School!
- Location: Little Rock, AR
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Re: How lean can you lean a Type4 for steady state cruise...
how lean did you guys go?
1981 Volkswagen Vanagon Westfalia - air-cooled Type4 1970cc CV (hydraulic lifters, 42x36 valves, stock cam, microSquirt FI with wasted spark ignition)
1993 Ford F-250 XL LWB Extended Cab 7.3L IDI
1993 Ford F-250 XL LWB Extended Cab 7.3L IDI
- Amskeptic
- IAC "Help Desk"
- Status: Offline
Re: How lean can you lean a Type4 for steady state cruise...
No LM-1, but I was robbing the engine until he could get no acceleration at all. Full throttle at 60 MPH, I would lean it until he could only maintain speed.luftvagon wrote:how lean did you guys go?
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles
-
- Old School!
- Location: Little Rock, AR
- Status: Offline
Re: How lean can you lean a Type4 for steady state cruise...
I got it up to 18 AFR at 65mph at about 85 kpa manifold absolute pressure. It is possible that it could go leaner.... at what risk, I wonder.
1981 Volkswagen Vanagon Westfalia - air-cooled Type4 1970cc CV (hydraulic lifters, 42x36 valves, stock cam, microSquirt FI with wasted spark ignition)
1993 Ford F-250 XL LWB Extended Cab 7.3L IDI
1993 Ford F-250 XL LWB Extended Cab 7.3L IDI
- Xelmon
- Sedna of VW lovers
- Location: LA or Portland, OR
- Status: Offline
Re: How lean can you lean a Type4 for steady state cruise...
Uhm, at frying the top of your pistons, see image for example...luftvagon wrote:I got it up to 18 AFR at 65mph at about 85 kpa manifold absolute pressure. It is possible that it could go leaner.... at what risk, I wonder.
Not what I would call healthy by any account!
The thing is that a temp sensor won't really help you here, and here's why.
At full load a classic engine will want to hover around AFR 13.5, maybe 14.0 if you feel really froggy. This is so that the fuel helps and cools the piston surface. As you increase the AFR, you are taking away that cooling effect.
Going super lean can cause nasty things like the burnt piston that I linked, marred cylinders, fried valves, etc. You may also hit detonation issues, which means that you need a knock sensor so that you can retard the timing, which robs you of even more power.
So, essentially better fuel economy and the death of your engine walk a very fine line. As I said, look at doing 13.5, maybe 14.0 and see what that does for ya. If it's marginal, then take it back down to 13.0 with the knowledge that your engine will last longer.
- Amskeptic
- IAC "Help Desk"
- Status: Offline
Re: How lean can you lean a Type4 for steady state cruise...
That is a question that begs another question. Why do you want to experiment with how lean you can get away with? Fuel economy? Sort out your needs. You want power, you want happy metallurgy, you want fuel efficiency.luftvagon wrote:I got it up to 18 AFR at 65mph at about 85 kpa manifold absolute pressure. It is possible that it could go leaner.... at what risk, I wonder.
You lose fuel efficiency in the name of power, you lose metallurgy in the name of fuel efficiency. Strike a balance and do not get all over-focused on one particular variable.
The BobD seemed to really like 12.5 - 13 at cruise and dive down to 11 - 12 under throttle. I had "acceptable" fuel economy that mirrored the factory claim of 17 mpg, and my CHTs were around 380-410 and my 50-60 acceleration times were around 7-8 seconds.
Colin
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles
-
- Old School!
- Location: Little Rock, AR
- Status: Offline
Re: How lean can you lean a Type4 for steady state cruise...
Here is the current AFR table:
And a beautiful matching fuel map:
And a beautiful matching fuel map:
1981 Volkswagen Vanagon Westfalia - air-cooled Type4 1970cc CV (hydraulic lifters, 42x36 valves, stock cam, microSquirt FI with wasted spark ignition)
1993 Ford F-250 XL LWB Extended Cab 7.3L IDI
1993 Ford F-250 XL LWB Extended Cab 7.3L IDI