If you know what you were getting before as far as mpg's go, drive it for a week and see what you got. When I was at 1* atdc (lumy probe) my mpg's dropped about 2 mpg's from what I was getting. When I went to 2* atdc I gained more power and went up slightly to 18 mpg from 17.8 or so. Over all it's been a vast improvement power wise from when it was at 10* atdc @ idle and 18* atdc @ 2000 rpm.
ip marks
- Thread starter jtate
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If you know what you were getting before as far as mpg's go, drive it for a week and see what you got. When I was at 1* atdc (lumy probe) my mpg's dropped about 2 mpg's from what I was getting. When I went to 2* atdc I gained more power and went up slightly to 18 mpg from 17.8 or so. Over all it's been a vast improvement power wise from when it was at 10* atdc @ idle and 18* atdc @ 2000 rpm.
see its kind of hard for me to tell because i dont drive it everyday its not my daily driver as of wright now. the previous owner had really took this truck through the ringer. i have been slowly bringing it back from the grave, and the only thing i have left to do is put a new brake booster on it and i could drive it everyday, but im trying to hold off and swap it to hydroboost because the reason i bought the truck was to pull a 32ft travel trailer.
f-two-fiddy
Registered User
Your timing is confusing.
Are you running retarded? The proper timing is supposed to be 8 degrees BTDC?
Are you adding the offset into your timing figures?
You have to read very carefully, I know when I first got my Snap-On MT480 all reference suggested that the timing be set to 8 to 9 degree BTDC. There is a lot of misleading info out there covering the luminosity style meters. What I found out is that this is for the pulse type adapters only! The Snap-On MT480 (any meter that uses a luminosity probe) should be set “at or after top dead center - ATDC. How people actually got there truck running setting the timing at 8* BTDC using the lumy probe is beyond me, however I think this is why some have had issues with the glow plugs melting – I think the plug actually got smashed from the pressure and shock of pre-ignition.
I’ll try to describe what’s going on.
The pulse style adapters sense the pressure drop in the injector line as the injector opens. You want to get the adapter clamp as close to the injector as possible, that why there is some kind of adapter mounted right on top of the injector (#1 for PU’s and #4 on Van’s. This is not the ignition of the fuel only the start of injection. When the piston reaches top dead center it is at full compression this is the approximate time when you want ignition to start. Changing your ip timing will determine when the air fuel mixture is correct to start combustion. So even though you’ve got the timing set to 8 BTDC the ignition really does not take place until you are close to top dead center.
The luminosity style probes actually sees (using a crystal inserted into one of the glow plug holes) the ignition as it happens so that is why you have two different timing references.
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