New to me 87 930 Plug Questions

[SG930]

Thanks for all the feed back on my first thread last month. Since then I bought a CIS gauge and checked my pressures. System pressure is 6.7 Bar, CCP was 1.0 @ 16 Celcius and WCP was 3.5 Bar. Since I have a BL Adj WUR, I adjusted the CCP to 2.0. This may explain the slightly harder colds starts and a pretty rich looking plug (Black lung?). It's a NGK BP8EVS. Car starts easier with the CCP at 2.0 too. The whole point was to figure out the really hard hot start which is my Fuel Accumulator. The system goes to zero in 3 minutes. Disconnected the the lower FA fitting and blocked the line and fuel came out. Ordered FA from our sponsor and looking forward to switching it out. So, since I had to remove Fabspeed IC and duct work, I thought I would check out the spark plugs. Based upon PO and rebuild at Mirage, the engine has 5000 miles so it's a guess that the plugs are from the rebuild. Not to experienced at looking at plugs or changing from the factory recommended but I get it since they are expensive, but so is the car. Any opinions on type, heat etc besides they are very dirty/fouled? Thanks.

I catch on quickly after a long time.

FYI. Fabspeed IC, K27 turbo, headers BB exhaust, RPM switch.

[reclino]

Plugs in the 930 are much colder than on most cars, part of the "reason" is that the CDI ignition easily fires a fouled plug. I am sure this is why Porsche stayed with CDI on the turbo cars. I have not run my car yet, but planned on starting out with BP7ES plugs, if I were racing or running high speed for extended times I would run BP8ES or W3DPO. I bet switching to a 7 heat range NGK of whatever flavor of the month will result in a cleaner plug. But if it's not running bad with those plugs it doesn't really matter what they look like.
David
Performance EngiNerding

[Bucketlist]

A lot of us use the BP8ES and I use the D8EA for the smaller bottom plug. They are all gapped at .025 to keep the fire from blowing out. Your BP8EVS plugs may be discontinued and were probably more expensive, I think they were Platinum. Might as well swap them for the BP8ES while you have them out.

[Neil Harvey]

I write a paper on reading plugs. Its on our outdate web site. Maybe this will help.

Remember the plugs will tell you exactly what is happening inside the combustion chamber.

https://performancedevelopments.com/spark-plugs/

[SG930]

Thanks for the input. The car runs really well especially after the new coil. I also had a typo as I do have BP8ES and not BP8EVS. I'll grab some new ones and simply replace them while I have things apart for the FA. I guess they are also known as NGK 2912 and NGK 3923 too. NGK recommends 0.031" gap. I do some more digging into that.

[spuggy]

Like David said, the stock plugs on the 930 (factory fitment was W3DPO) are much colder than most cars. This (probably) ties back to the factory thinking they were making a few hundred cars for production racing homologation, and that they'd mostly get trailered to/live at the track - rather than being bought by regular folks and driven as an actual car.

But then the question arises "why didn't the factory change the plug?". They stuck with the really cold plugs until the 993 TT (which went 3 heat ranges or so hotter, IIRC). Answer is probably that EPA testing was not cheap - and they could perhaps avoid a complete re-test if they only made incremental changes. Like the extra emissions doo-dads they grew over the years. Pure speculation on my part...

Cold plugs apparently give better/sharper throttle response than hotter plugs. And they conduct more heat out of the combustion chamber, so are "safer".

I never had a W3DPO foul on me (or break down under boost) in 10's of 1000's of miles with CIS, including plenty of stop-go driving in town - so stuck with them when converting to twin-plugged/COP. Sure, they're pretty spendy for a wear item - but seem to work flawlessly for me.

No personal experience with the NGKs. Some like 'em. They are a lot cheaper than the platinum Bosch plugs...

[flightlead404]

Originally Posted by Neil Harvey

I write a paper on reading plugs. Its on our outdate web site. Maybe this will help.

Remember the plugs will tell you exactly what is happening inside the combustion chamber.

https://performancedevelopments.com/spark-plugs/

Photographs would make it much better.

In the front of every Hayne's book there's a page or two on plugs with color photographs.

[flightlead404]

Originally Posted by SG930

Thanks for the input. The car runs really well especially after the new coil. I also had a typo as I do have BP8ES and not BP8EVS. I'll grab some new ones and simply replace them while I have things apart for the FA. I guess they are also known as NGK 2912 and NGK 3923 too. NGK recommends 0.031" gap. I do some more digging into that.

I think there's a couple of versions, one with a solid tip on the cable side and one with a screw on tip

[tops911]

Just sharing my experience when it comes to plug gap: I put in an MSD cdi box and read where mad recommended opening up the gap due to the multi spark. I opened the gap and all was good for a while. Then I had running issues and it ended up that the spark was being "blown out" under boost. I struggled for a while trying to figure out the issue. I tightened up the gap back to factory recommendation and the problem went away.

[SG930]

I ordered NGK BP8ES and received NGK BPR8ES. I freaked out a bit and after calling the supplier and searching NGK, the R is the replacement and BP8ES are no longer made. They look and measure the same. I run an aftermarket CDI Box and thought we don't run resistor type plugs but now they are the same?

[turbo ride]

Yes BP8ES (which my car ('91 964 T) has run for longer than I've owned it (11+ yrs, 60,000+ miles) are no longer - bummer. But like you said - the suppliers are all saying the BPR8ES is a direct swap in with no real world difference. I guess we'll see...

Originally Posted by SG930

I ordered NGK BP8ES and received NGK BPR8ES. I freaked out a bit and after calling the supplier and searching NGK, the R is the replacement and BP8ES are no longer made. They look and measure the same. I run an aftermarket CDI Box and thought we don't run resistor type plugs but now they are the same?

[mark houghton]

I ran BP8ES years ago jn my first 930. Worked fine. And if I recall I had gapped them really huge....like .042 maybe, mainly because I was running with MSD ignition and they recommended that gap. No misfiring ever that I could tell and the plugs looked to be colored correctly.
FWIW....