Backfire while coasting

Carbs & F.I.

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cegammel
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Location: Thomasville Georgia
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Re: Backfire while coasting

Post by cegammel » Tue Jul 14, 2015 3:43 am

Latest post of the previous page:

I initially connected my cht sender under my TS2. The CHT worked fine, but it did screw up the TS2. There was about a 50° difference, but it was just as consistent.

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Mulcheese
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Location: Maple Grove, Mn
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Re: Backfire while coasting

Post by Mulcheese » Tue Jul 14, 2015 6:36 am

I have started a new thread on the topic of the terminal end.

I do feel that I have been running a bit lean and have done some AFM adjustments to correct.

I do have a exhaust leak but question. How bad does a leak need to be to create the popping?

Can someone supply a pic of a decent looking plug from a know "perfect" running engine? I understad that plug color is only part of the diagnostics. That is why I brought up the temp issue. Following the last AFM adjustment temps dropped considerably and performance was static so I feel that I am on the right track.

Thanks,
"attending to things in the moment with curiosity and acceptance."
____________________
82 Vanagon Westy - aka: Honey Badger - "cause she just dont give a ...."

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Randy in Maine
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Location: Old Orchard Beach, Maine
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Re: Backfire while coasting

Post by Randy in Maine » Tue Jul 14, 2015 7:45 am

It takes just a whisper of an exhaust leak to create that popping on deceleration.
79 VW Bus

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Amskeptic
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Re: Backfire while coasting

Post by Amskeptic » Sun Jul 26, 2015 10:34 am

Mulcheese wrote:I have started a new thread on the topic of the terminal end.

I do feel that I have been running a bit lean and have done some AFM adjustments to correct.

I do have a exhaust leak but question. How bad does a leak need to be to create the popping?

Can someone supply a pic of a decent looking plug from a know "perfect" running engine? I understad that plug color is only part of the diagnostics. That is why I brought up the temp issue. Following the last AFM adjustment temps dropped considerably and performance was static so I feel that I am on the right track.

Thanks,
Here is Chloe's Death Valley 2013 spark plug portrait:

Image

These would be too lean if it was just driving around town or even on the highway, but these plugs had just been through some serious ambient heat. There should be no white on the ground electrode. The ring at the bottom of the threads should be black. The insulator should have a touch of brown maybe white near the center electrode. Hot plugs have the insulator sticking out from the bottom of the threads, cold plugs have the insulator nestled within, like those in the photograph.
Colin
BobD - 1978 Bus . . . . . . . . . . .111,130 miles
Chloe - 1970 bus . . . . . . . . . . . 206,787 miles
Naranja - 1977 Westfalia . . . . . 93,996 miles
Pluck - 1973 Squareback . . . . . 55,510 miles
Alexus - 1991 Lexus LS400 . . . 72,113 miles

72Hardtop
Old School!
Location: Seattle, WA./HB. Ca./Shizuoka, Japan
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Re: Backfire while coasting

Post by 72Hardtop » Sat Jun 03, 2017 12:21 am

The following were after jetting with an LM-2 wide-band for WOT 12.8-13 or so and cruise at low-mid 13's (where a bus is happy CHT wise). You want to stay out of the 'Death zone' with these engines (14.7) when WOT and cruise. A bus can weigh easily 2.5 tons fully loaded. Combine that with it's aerodynamics and running stoich = High CHT's

NGK B5ES plugs
https://www.thesamba.com/vw/gallery/pix/1201652.jpg

Piston engine power management chart:

https://www.thesamba.com/vw/gallery/pix/1463782.jpg
1972 Westy
2056cc T-4 - 7.8:1 CR
Weber 40mm Duals - 47.5idles, 125mains, F11 tubes, 200 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
Bosch SVDA w/Pertronix module & flamethrower 40K coil (7* initial 28* total @3200+)
NGK B5ES @ .028
002 Trans
Hankook 185R14's

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