Up until two weeks ago I was averaging 18.8 mpg in my mixed highway/surface street driving. Engine is 1600 DP, 34 carb, SVDA distributor, Compufire points replacement. No problem, no muss, no fuss.
Then I installed a Tiger CDI, gapped plugs to .040. Engine starts easier, feels smoother. Noticed that it was running 5 - 10 degrees (F) cooler (oil sump temp, subjective estimation only).
"Mike Rocket J. Squirrel Elliott" > >>Hmm . . . this has me puzzled.
okay, okay, you convinced me.....now i will spill the beans....you have noticed that the engine runs better/smoother..... the problem with this is it is like "found power" and you will use it...typically of course...not saying you are "hotrodding" around in your bus, but typically when something "improves" the way your engine runs, you will drive it a little hotter...it will affect the mileage of course, but you will go back to "normal" when the "newness" is gone...heh...
Maybe that's part of the reason I'm getting better and better gas mileage in my Civic. I always reset the trip odometer at each gas fill-up. I believe it's an 11 gallon tank. When I first got the car, I would have to stop at about the 310 mile mark. I've got about 22K miles on it now, and right now the trip odometer is reading almost
370. I'll need to fill up very soon, but... I think it's a combination of bumping up the air pressure in the tires, starting to take the "back roads" in to work to avoid the frantic pace on the highway, and the newness thing wearing off. (No, I'm not saying my car is a hot-rod and that I'm finally getting used to the stump-pulling torque. :-)
The engine is running smoother, but I have no sense of additional power at all. I didn't expect to get more power from a CDI and have not been disappointed. The smoothness seems to be a function of more stable ignition, is all. I don't leadfoot this old bus.
No remote cooler. The oil sump temp is now running up into the 220 - 230 F range as it heats up around here. I don't think I want to advance the timing as she is plenty warm enough as is! In fact, I plan to retard the timing a bit to see how she pulls away from a stop and see if the temp drops a smidge lower.
I just had the brakes done and the wheel bearings repacked and adjusted. Now as soon as I remember to do so, I will feel those parts to see if they are heating up. Might be something dragging.
I have received several suggestions about reducing the plug gap from the .040'' that Tiger suggests. Will do.
And of course I have a timing light and I'm not afraid to use it, so I will double-check the timing as P.J. suggested. The instructions that John C provided with the SVDA has the timing advanced to 42 - 45 degrees @ 3500 w/ vacuum connected. I don't know if this is ideal for this stock Mexi 1600DP pushing a bus.
squirrelman not saying you hotrod your bus(heh) but it is very common for someone that has perceived a difference, in your case smoother running, to actually run them a bit more because they are actually paying attention....your normal driving habits are more "natural" and you don't even think of it....but when paying attention it tends to change...was just my opinion...
You'll be happier with the wider gap. You now have a helluva lot more voltage to jump that gap. Closing them again will cause "dribbling" (Isn't that what them scopes you 'lectronic guys use show ya? - Dribbling?) Okay. Wider gap with greater voltage equals hotter spark of less duration / fewer oscillations. Fuel is ignited better. Should not directly cause any decrease in fuel economy but should result in better fuel economy - IF ALL THE VARIABLES ARE LOCKED IN. (Sorry - now I'm hoarse!) You probably have introduced more drag at the wheels. Quite a bit more. {I DO agree with Chris that you are probably slightly more aggressive now, but you're so damned level-headed and easy going, it may not be a factor!} EASY CHECK: Pull the plug out of the CDI and turn it around to bypass and drive the next tank of gas that way. (Don't worry about putting the gaps back for this one-tank experiment - it will start harder than before and will ping sooner on hard pulls)
An air cooled vw runs cooler and gets less mileage when it runs richer. I would guess that for some reason connected with your upgrading system this is happening. Just my opinion of course. Dennis
MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.