Is this directly linked?

I believe this is true but i just wanted this confirming....

a grade 6 plug, will not allow as much timing advance as a grade 7 and similarly a 7 to an 8?

im trying to understand why my engine doesnt seem to like much timing being thrown at it, and i think that this may be one issue that needs addressing. I believed that i had 7s put in after my build but until now it didnt occur to me to check. So when i do, i am half expecting to find a set of 6s in there....

 

if you mean the seven as in PFR7G11 for example . this is simply the heat rating lower the number hotter the plug . they fit 6 as standard .

 

i realise that, but colder rated plugs are recommended in higher power applications, so if mine are 6s then they are technically holding the car back at the moment.

 

A PFR7B will run a little cooler than a PFR6B so should be less likely to contribute to detonation.

There may be other reasons why your car isn't happy with the timing you expect though.

 

Neil with regards to the mods you have done I'd strongly recommend a heat grade 7 plug as the standard 6's will be holding the car back in the sense that it'll run alot smoother and throttle response will increase with the 7's.

As the number increases the thermoconductivity ratio of the spark plug decreases, meaning that a hotter engine will require a higher number rating of plug to cope with that added and increased heat.

I knew sum1 that had a Supra which had 9 rated plugs... think he was pushing out 800bhp!

Cars such as Mondeos... Vectras... Passats will have 5 or 6 rated plugs as standard.

7 rated will be good on a Scooby upto about 380-400bhp But get rid of those 6's mate!

 

if they are 6s...

i did have 7s before, but i havent checked these since the build. they are due for a change, but ideally id like 8s but no idea where to get them

 

Mark can supply the 8's. We used to run 9's, but have now dropped back to 8's as it doesnt appear to hamper our engines.

 

8's don't really like day-to-day running and cold starts, etc and can foul up easily though AFAIK?

Russell

 

I've used 7's up to 500bhp then 8's for anything above.

Andy

 

Thanks all, they are due for a change so ill try a set of 8s as its no longer a day to day car anyway and it should give me a little more flexibility with my overall plans

 

Neil depending on which '8's you will probably suffer from fouling, they don't clear well either, I'm using some Denso racing Iridiums for general and performance use and they are the only plug that I have managed to take past 5k miles, first set I changed at 15k, this set has been in since Feb. Trouble is they are expensive. Stick with '7's. IK01-24 is the part number of the Denso's. Fouled up plugs will cost you 50-60 bhp.

bob

 

Thanks Bob, i think that i will change mine at my earliest opportunity. I suppose the worst case is having 6s that are fouled!!

 

Can you really argue or question this man??

7 th heaven baby!!!

 

Well you should really ! What works for me may not suit everyone, an oil burner used for short runs for example may foul 7's where a clean burning car used differently may be happy on 8's.
I'm just adding my tuppence worth

 

Neilo

Must check my plugs but RCMS fitted 8's recently again to my Bugeye AFAIK which Bob has mapped and I have been running them for the past 18mts, I thought I had probs with idle but it was the idle solenoid !!

When I looked at them at RCMS it seemed a shame to throw them away as they looked pretty good to me

Shaun

 

have you guys had any problem with 8 plug having hard starting? i used it for evryday driving as the problem is i can get hold of the pfr7 here locally in manila

 

I've been running on BKR8EIX for the last 10000 miles with no issues.

 

So what mileage (ideally) should you change 7's..? (suppose it depends on car and driving style as Andy has said).

Probably worth checking them periodically, even if it is a bit of a PITA..? (although I don't mind doing them TBH..)

 

Typically about 15k depending on what you are using the car for. 7's are fine for Neil I expect, its just that they never lasted long in my car "going off" very noticably. But for the use he is intending then I know the Denso's will work nicely.

bob

 

would NGKPFR7's be best suited to my 400bhp STI7?

 

Shouldn't be a problem, gaps are important though, 0.65mm.

bob

 

cheers Bob will make sure they are gapped well

 

Do they usually need re-gapping during their lifetime..?