ProtoCab

What kind of plugs are you guys with heavily modded 993TT's running?

Are you still using the OEM FR6LDC plugs, or have you changed to a heat range lower, such as a FR5LDC plug?

Just curious, because the W3DPO's for the 911/930 turbo's are extremely expensive and too cold for street use, so I'm considering using a 993TT plug if that's a more viable solution.

I've tried a 4 heat range plug in my car, but that is still too cold for pure street I think. They tend to foul up pretty quickly.

I'm considering trying a 5 or 6 heat range, as used in the 993TT's. I know that a colder plug is more resistant to detonation, especially for track use, but for stree use, they tend to foul up pretty quickly since the motor isn't under extended heavy loads often enough to burn off carbon deposits. A hotter plug would be better, but caution must be taken to ensure it's not TOO hot a plug as this can cause pre-ignition/detonation under heavy loads.

Advice please?

P.S: BTW, my car is a daily driven heavily modded EFI'd turbo, which runs ~1.15 - 1.2bar of boost

911/Q45

I still have the stock plugs in my Andial 3.8. It is twin plug and I run it hard and hot at the track, but do a lot of putting and idling otherwise. When the ambient temp is above 80°F I use about 50% 100 octane race gas and have had no detectable detonation problems. I'd be afraid to run a colder plug, as plug changes are very tough with twin turbos and twin plugs if they foul.

ProtoCab

Thanks for your feedback

Are your stock FR6 plugs gapped as they came from factory (i.e: 0.9mm), or have you lowered the gap somewhat? Are you also running the OEM ignition system? No aftermarket MSD/Crane?

911/Q45

Factory gap, factory twin distributor and coils.

ProtoCab

You mean, 993/964 distributor? The 993TT never came twin plugged AFAIK.

How much boost do you run with your setup?

How do your plugs look when you pull them? Tan/grey color? Or black & sooty?

911/Q45

The twin plug setup was added by Andial and uses the factory 993NA ignition parts. I'll find out the condition of the plugs soon, as I'm approaching 30K miles since the conversion. Boost is about 1.3 bar.

ProtoCab

Thanks for your input. I run 1.25-1.3bar on my 3.3 EFI turbo, but my car is 100% street. I currently run a 3 heat range plug, but since I do a lot of low speed driving in traffic, these tend to foul fairly quickly and I'm replacing my plugs every 3,000-5,000 km's.

I'm trying to ascertain what would be an ideal heat range, suitable for my car/application and I'm leaning towards the FR6LDC, or maybe one range colder, the FR5LDC.

I don't get to drive her to max boost very often, which would explain why my W3 plugs are fouling so quickly Therefore, if you guys are successfully using the FR6 (or FR5's) in your heavily modified TT's, then I should be able to get away with running a similar plug in my 3.3 turbo. That's MY theory anyway.

When I eventually track my car, I will then run a 3 or 4 heat range plug for track events, to reduce likelihood of pre-ignition under sustained heavy loads.