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redrosie
Samba Member
Joined: November 05, 2019
Posts: 36
Location: Indiana
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 Posted: Fri May 16, 2025 6:56 pm Post subject: Better MPG with 40° Timing |
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I set the timing to 40° with the help of Tencent's procedure and immediately saw results on the highway and a separate tank of city driving.
Both tests showed improvement of close to 3 mpg. Highway 17.7, city 16.2 mpg. I drove it hard and didn't baby the throttle at all.
I have kept mpg records since my engine rebuild about 4000 miles ago. At that time it was set according to the GoWesty 35° procedure.
I've spent lots of miles wondering what the issue was because before the rebuild the mpg was better.
I did use a HF $35 adjustable timing gun this time instead of measuring and marking the crank pulley.
Do my higher ratio Rockers require the full advance timing? Not sure.
In addition to the lower mpg, the engine needed to be warmed up quite a bit or take offs were jerky which is not an issue now.
Also I feel slightly more power.
Big thanks to Tencent and the other great contributors on this forum. |
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MarkWard
Samba Member
Joined: February 09, 2005
Posts: 18736
Location: Retired South Florida
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| Posted: Sat May 17, 2025 7:39 am Post subject: Re: Better MPG with 40° Timing |
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Sounds like you found a sweet spot for your engine. Too much timing can lead to knocking/detonation which will cause engine damage over time. Compression, fuel mixture etc determine how much timing advance you can run. Go Westys value of 35 degrees is likely in a safer zone when you don’t know the other conditions I mention above.
When we tune timing advance we are on a chassis Dyno and are watching max torque. We advance timing till we measure a drop in max torque and then retard a couple degrees. I posted this so that others understand that there is not a one size fits all for total advance. |
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Wildthings
Samba Member
Joined: March 13, 2005
Posts: 52319
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| Posted: Sat May 17, 2025 9:51 am Post subject: Re: Better MPG with 40° Timing |
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| MarkWard wrote: |
Sounds like you found a sweet spot for your engine. Too much timing can lead to knocking/detonation which will cause engine damage over time. Compression, fuel mixture etc determine how much timing advance you can run. Go Westys value of 35 degrees is likely in a safer zone when you don’t know the other conditions I mention above.
When we tune timing advance we are on a chassis Dyno and are watching max torque. We advance timing till we measure a drop in max torque and then retard a couple degrees. I posted this so that others understand that there is not a one size fits all for total advance. |
Decades ago both my stock '91 Multivan and my stock '87 Syncro were being used as daily drivers. The Multivan ran very nice when "correctly" timed to the middle of the book specs, whereas the Syncro liked being several degrees towards the retarded side of spec.
As for the ratty 1.9L that was in my 83 1/2 when I bought it, it seemed pretty indifferent to where the timing was set. At the center of spec it ran like a scowled dog at 7000 ft, much better than the stock 2.1L in the rigs mentioned above and even better than the Subaru that is in the Multivan today. Adding extra timing did nothing at either 7000 feet or at sea level. I have no idea how stock this 1.9 was, but it was ratty with very low compression and used lots of oil. The only running problems we had was trying to get it started once the temperatures dropped below 10°F, otherwise it ran strong and got noticeably better than average Vanagon gas mileage.
Last edited by Wildthings on Sat May 17, 2025 11:58 pm; edited 1 time in total |
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RicMcK 
Samba Member
Joined: August 29, 2023
Posts: 225
Location: Seattle
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| Posted: Sat May 17, 2025 4:33 pm Post subject: Re: Better MPG with 40° Timing |
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Please link to the "Tencent" for the process.
_________________
Rick McK
Seattle
89 Westfalia-2.2L WBX
2006 TDI Jetta
1936 Ford Pick up
70 tin top, 700k mi when sold in 91
58 split window bug - long gone. |
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Ahwahnee
Samba Member
Joined: June 05, 2010
Posts: 10218
Location: Mt Lemmon, AZ
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Wildthings
Samba Member
Joined: March 13, 2005
Posts: 52319
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| Posted: Sun May 18, 2025 6:41 am Post subject: Re: Better MPG with 40° Timing |
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| Ahwahnee wrote: |
Note to Digijet owners (1.9 l) the measurements are slightly different since our idle is 5* ATDC. |
The book shows an "all in" timing of 42° @3800 rpms hoses connected and the DIS bypassed, which works out to 28° @3800 rpms with the hoses removed and plugged, and the DIS bypassed. which is the best way to set the timing as it mimic full throttle high rpm conditions when you want the most from your engine.
10c is in error here by quite a bit. |
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LarsHepping
Samba Member
Joined: September 03, 2020
Posts: 27
Location: Deep in the woods
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| Posted: Sun May 18, 2025 12:21 pm Post subject: Re: Better MPG with 40° Timing |
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| redrosie wrote: |
I set the timing to 40° with the help of Tencent's procedure and immediately saw results on the highway and a separate tank of city driving.
Both tests showed improvement of close to 3 mpg. Highway 17.7, city 16.2 mpg. I drove it hard and didn't baby the throttle at all.
I have kept mpg records since my engine rebuild about 4000 miles ago. |
Before advancing the timing you were only getting ~14.7 highway and ~13.2 in town? That’s pretty bad!!! Also, who rebuilt your engine? If you’re running that much timing and have an issue who is to say they won’t blame you? |
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