11-21-2007, 04:25 AM
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Senior Member
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Join Date: Mar 2007
Posts: 319
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I love this thread!
Thanks Aaron and everyone else contributing to this thread!
I wish to try this modification to the O2 sensor as well.
First, I am going to Seattle soon (14 hrs from where I am in BC) and will be documenting my highway mileage on this trip so I can get at least a seat of the pants idea of my mileage. Unlike you Aaron, I am very lazy with knowing what MPG my car gets  - its already pretty 'good' as stock cars go, so I normally don't worry about it - but I want MORE MPG of course! 
I have a 91 Pontiac Grand Prix with a 3.1L V6 in it. Many of these GM V6s got very good MPG in my opinion, considering the size and weight of the cars. In the trade, this is often noted by mechanics regarding these engines.
The cool thing about a FI engine is that there are often knock control systems so that even if it is undergoing preignition, the timing will be set back until the knock stops. However, many FI systems do not use knock sensors but manage preignition through EGR and ignition curve mapping, so that protection system wouldn't help much with aftermarket mods.
Regardless, a careful ear will at least detect the worst knock and then one can do adjustments. Its important to realize though, that the beginning of preignition or even detonation (this is different than preignition) will not be detectable by ear and thus damage can occur before you are aware of it.
However, I believe the mods discussed here are quite viable and I wish to try them when I get back home after the first week in December.
Great pictures and instructions, Aaron, thanks!
I too wish to try the Pulstar plugs but am going to do one mod at a time to see what MPG changes occur. I can tell by my exhaust smell that my Catalytic converter is not working, but it doesn't smell rich. In any case, I am going to test my O2 sensor for proper operation, put new stock plugs in the car as I have a misfire in light accel conditions and though this could be other things, I have never changed them and of course will inspect them first.
LOL, i have to remember the different gallon size when I am in the States at the end of this month so I don't get wonky MPG figures  .
I cut my eye teeth on Fuel Injection systems so I see them from the other side of being very aware of how they work and seeing the many pluses of them. If you have a carbureted vehicle, in my opinion, one of the best things you can do to get more MPG right off the bat (since most of these will have many miles on them) is to get it hooked to a gas analyzer and watch your CO reading under cruise conditions. Many times this will be too high and though you won't notice anything driveability-wise, it will definitely be using too much gasoline. Adjusting the needle/seats/jets will bring this back in line. If you say 'but I have a new or rebuilt carb on there', don't be fooled! Those are some of the WORST for being in range of good fuel mileage as this is usually not set up or tested properly - they are just reconditioned.
Good points on the O2 sensor needing to warm up, Redmeanie. Open loop is designed to just get the car running well until the O2 is warmed up, thus the heaters most O2 sensors have nowadays. They want to be in open-loop for as short a time as possible as this is programmed to be on the rich side, and high emissions. It is when the ECM observes the change in V at the O2 that at some point it goes into closed loop. This is important that any mods take this into account, for if we were to modify something and have it stay in open loop - that would be much worse on MPG and emissions!
Once I get to these mods, I will also report asap on any findings!
Peace,
Stephen
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