Lowered compression=hotter plugs?

[tooch]

Just a quick question, my rebuilt motor has had the compression dropped slightly to allow more boost, would this mean that I should run hotter plugs?
The reason I ask is that the motor was running ok with plugs that were one step hotter than the recommended (Book says BKR6, I was running BKR5), and last night I changed them to BKR7, as that is recommended for 3SGTE's running higher boost. This morning, after sitting in traffic for a while, the car started idling and driving really roughly, was running on what sounded like 3 cylinders. I put this down to the plugs fouling up while sitting in slow/stopped traffic, and being colder they could not burn off the deposits.

So my question is, would I be better off running the hotter plugs again, or stick with the standard ones, bearing in mind the lowered compression ratio.

[ae86trueno]

Ahh welcome to the that annoying middle ground,
I have a similar problem is the rally car, 7's are used when in competition, ie more spirited driving, but they foul if im stuck in traffic, so between events it runs 6's just so its drivable.

The downside is that running a 6 can lead to pre-ignition/detonation during more spirited runs especially if your running more boost. And spark plugs arnt exactly easy to change in a gt4 .

Ben.

[tooch]

I'm just throwing in another set of 5's for now, as I sit in traffic a bit, and the car is running very rich still so I'm not too worried about detonation. Once it's tuned I'll stick some 7's in it, I can't be bothered arsing around pulling the cooler off every time

[kingmick]

Just a quick question, my rebuilt motor has had the compression dropped slightly to allow more boost, would this mean that I should run hotter plugs?
The reason I ask is that the motor was running ok with plugs that were one step hotter than the recommended (Book says BKR6, I was running BKR5), and last night I changed them to BKR7, as that is recommended for 3SGTE's running higher boost. This morning, after sitting in traffic for a while, the car started idling and driving really roughly, was running on what sounded like 3 cylinders. I put this down to the plugs fouling up while sitting in slow/stopped traffic, and being colder they could not burn off the deposits.

So my question is, would I be better off running the hotter plugs again, or stick with the standard ones, bearing in mind the lowered compression ratio.

bump the idle up! might get you past the fouling or go back to the standard plug.

[tooch]

True true! The idle is a pain in the arse, sits at 2k until its fully warmed up, then only drops if I give it a good blip while sitting at the lights, then settles down. I need to get this sorted with the tuning.

[oldcorollas]

why not run 6's??

it's a big jump from 5 to 7....

start with 6's.. if they stay clean, and don't show any signs of overheating, you won't need 7's...

are the 5's showing signs of overheating now?