ENGINEERMAN

Hi all:

I have a Strosek 911 Turbo, the motor for which was built by David Hart of Proto Tech a few years ago. The motor is an 84 based motor and according to David is putting out about 400 HP or so. I do not have all the spec's on what was done (previous owner, long story) and David does not have the records either and does not recall exactly all of the modifications that he did. The car seems very well sorted out and runs like a top.

I have been doing some maintenance things over the winter and decided to look at the plugs to get an indication of the motor condition (the motor now has just under 10k miles since complete rebuild and performance update). They were all looking perfect. I wanted to put a new set in. They are Bosch W3CS. From what I understand the W3CS is a silver electrode plug that is supposed to have very good heat transfer characteristics and I must say the car was running just fine with the W3CS's.

When I looked in Bruce Andersons book, it seems that her recommends this plug for almost every 930 model in the 77-89 model range. However, when I look at the Pelican Parts site or check with the local auto parts store I get different plug recommendations, e.g. Bosch W3DPO, NGK BP8EVX.

I would be curious to get your input as to what plugs you all find to be the best in your 930 motors. Is there anything to the new Irridium plugs, etc.?

Thanks in advance!

Tom

Geoffrey

The CS plug indeed has a silver electrode. I run the W4CS in my car which is one heat range hotter than the stock plug which is a W3DPO or platnum plug. In my opinion, the 3 heat range is too cold for these cars, especially if you have EFI and can control fueling. The NGK BP8EVX is in the same heat range as the Bosch '3' heat range. If you say your plugs are "perfect" then why change?

Steve Weiner-Rennsport Systems

Hi Tom:

Those Bosch Silvers you currently have are very good plugs and FAR better than Iridiums. As Geoffrey said, the "3" heat range is cold but the true test is how they look after use in your engine. If you are not fouling them, I'd stick to those W3CS.

Bottom line: The heat range of choice is dependent on how the engine is operated. High boost (1 bar and above), track use, and higher speeds do require colder plugs than strictly highway use at stock boost.

If you are really curious, do a proper plug cut and pull one out to take a look. If you are unsure how to perform this, contact me directly for a list of instructions.

ENGINEERMAN

Thanks guys!

My boost is set at .8 Bar and as I said the car is PLENTY fast (I sometimes think that I am on an amusement park ride it)! This is a street car, I do not plan on tracking it since I already have a pretty well set up 944 Turbo & a Mazda Miata with all of the Racing Beat goodies for track purposes) and this car is to dear to me to take a chance at the track of wrecking it. Again, I am looking for maximum longevity of the engine at the current performance level but want to learn from all of you who clearly have much more experience.

I did notice that that cylinder #1 was a little darker than any other cylinder as if it was just beginning to foul a little (I drove the car pretty hard before putting it away for the winter and it won't be driven any harder than that.

Based on what you gents said, I think that I might give the W4CS's a try just to see how they look by comparison (my gas mileage is in the low teens around town and around 15-16 on the highway and so I suspect that it is running on the rich side anyway and a hotter plug may be a little better suited). Geoffrey, if you are using the W4's with success under the track conditions, higher boost and significantly higher output then I can't imagine that I am going to get the plugs too hot with the type of driving that I do on the street. That might clean up that #1 plug a little better as well. Do you agree?

Also, how often do you change plugs, cap, rotor, plug wires? Every 10,000 miles as I have seen some people recommend seems to be pretty short based on my experience with other cars but again I am still learning this car and want to do it the right way. So your input is appreciated.

Finally, no one seems to stock the W3CS or W4CS plugs. Can you recommend a source(s) that sells them?

Thanks!

Geoffrey

I'm using the W4CS plugs at .7bar of boost on the track with an EFI engine. They have been in 2 years so far and still look good. One if the big issues with the CIS cars is that they are set so rich at idle 12.0-12.5:1 afr that they look sooty and black. As Steve mentions you need to follow the proper procedure to be able to have a plug that is read. I have also started the Iridium plugs from NGK with good success lately, especially with a racing CDI system. I use an NGK heat range of 7 or 8 on an EFI turbo car. There are so many choices, shrouded, unshrouded plugs, and heat range that NGK offers so it is a little easier finding a plug that will work for a given application. You can call Steve and he can get you the plugs. My local import store is able to special order them for me.

ENGINEERMAN

I just got off the line with Steve. He is a real wealth of information! As I said only the #1 plug looked a little sooty and so I thnk that my next step will be to ry the W4CS's when I next change the plugs.

Thanks again for your help!