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I Finally made some time today and managed to get around to changing the spark plugs on the Beast. It says after first tuning the NOS, you are supposed to inspect the plugs, which can give an indication if your running rich or lean. I had used my AEM UEGO gauge anyway last time I gave the Nitrous a blast, so I knew that the AFR was dropping to 13.7 from around 11/12 when on boost. The meant that the NOS was leaning out the engine when injection was taking place. After the plugs being in the engine since it was build, I knew it would be worth changing them. What a great difference they made....the engine had been a little lumpy recently, and seemed to hunt around at idle.
The plugs were actually really filly to do. If you have ever worked on a boxer engine, you will sympathise. I must have had 5 or 6 different socket combinations just to either get the plug out, or back in and using various breaker bars and bad language, I succeeded.
As a quick hint, on the passenger side, remove the battery and go in from the top, its a lot easier than from below. Also on the drivers side, just remove the air intake and its a lot easier.
I would like to think that after all the years of Impreza development, Subaru have finally designed in more clearance in the engine bay for future models, but I doubt it!!
Anyway, the plugs were pretty fouled and black, indicating a tough life running rich! It idles so smoothly now its gorgeous. I also treated it to an Oil change on 10 W 50 Millers fully Synthetic.
Mileage is only 26,124 (Just for my records!)
After that, I removed the nOS fogger and kept the same fuel jet, and swapped to the next size down for the Nitrous jet. This should mean that the engine does lean out as much on injection. Ill have to have a play around with the controller and increase the injection power a little now Im on the smaller jet, but for that, I need more time to set up the AFR gauge in the exhaust again so that can wait until next week.
It seems that the best investment I have made was the magnetic sump plug. After removing it, I found a small screw stuck to it, that was in the Sump!!!! I haven't a clue where that came from, but I guess I got luck it was caught by the magnet and couldn't circulate!!!!
The plugs were actually really filly to do. If you have ever worked on a boxer engine, you will sympathise. I must have had 5 or 6 different socket combinations just to either get the plug out, or back in and using various breaker bars and bad language, I succeeded.
As a quick hint, on the passenger side, remove the battery and go in from the top, its a lot easier than from below. Also on the drivers side, just remove the air intake and its a lot easier.
I would like to think that after all the years of Impreza development, Subaru have finally designed in more clearance in the engine bay for future models, but I doubt it!!
Anyway, the plugs were pretty fouled and black, indicating a tough life running rich! It idles so smoothly now its gorgeous. I also treated it to an Oil change on 10 W 50 Millers fully Synthetic.
Mileage is only 26,124 (Just for my records!)
After that, I removed the nOS fogger and kept the same fuel jet, and swapped to the next size down for the Nitrous jet. This should mean that the engine does lean out as much on injection. Ill have to have a play around with the controller and increase the injection power a little now Im on the smaller jet, but for that, I need more time to set up the AFR gauge in the exhaust again so that can wait until next week.
It seems that the best investment I have made was the magnetic sump plug. After removing it, I found a small screw stuck to it, that was in the Sump!!!! I haven't a clue where that came from, but I guess I got luck it was caught by the magnet and couldn't circulate!!!!
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