Which plugs for 400-450 bhp (Trackuse)
 

Car is a Type R sti3

NGK R7434-8.

Does the same code apply to lesser modded cars with a slightly warmer plug i.e. NGK R7434-7 ???

lesser cars (say around 350hp) should be fine with PFR7B plugs.

Paul

Cheers Paul, thats already what i run with a 0.6mm gap just thought it may be a better alternative.

Stuart :)

Cheapest place to get them from then chaps ?

Just looked at a thread wher harvey has said choose a NGK PFR7B dont know which ones to put in now.

R.B

The 7Bs don't last too long at higher power levels, several have noted this, I had a set analysed by NGK and they said that it was subjected to too much pressure/temperature and the insulator had broken down, and they recommended either a colder plug or a 7Q (OEM for RS4/RS6 and note they are only running 50-60 lbft torque per cylinder compared with up to 100 lbft that you might expect out of a 4 cylinder 400-450 BHP Scooby). The 7Q has a different insulator. I think 7s are too hot for track use at high power, although they don't seem to break down catastrophically, but the engine just gets lumpy on boost. However, even on the road switching from 7Qs to Racing 8s at this level whilst it is less smooth at low loads or when it is cold, there is less knocklink activity, especially when booting it after a period of cruise. I chose to switch plugs rather than retard the ignition to see if it fixed the problem, and notably it did - additionally I did not need to change the gap on the 8s (which are tricky to gap anyway, whereas I had to pull the 7Qs down to 0.6-0.65mm with an apparently healthy ignition system to keep ti smooth). Racing 9s were definitely too cold for my engine and even on a warm car would hesitate when running closed loop at low speed cruise. They were not fouled but obviously carboned up when removed. The 7s always looked OK when pulled, remains to be seen what the 8s look like.

Recommendations I've seen suggest one heat grade for every extra 80 BHP or so over stock, although this is a very rough.

So I think 7s are safe enough, and can work well for a while, but probably will only last a quarter or so of the usual expected life. Given this I suppose it is in the back of my mind they could fail catastrophically one day.

Thanks for the John do you know where i can get them.

sparkplugs.co.uk ?

Ive tried on search but they say they dont list them john ?

Ring them up and ask for them or an alternative? Model numbers of the racing 8s have changed recently.

7b's are fine if run for 5k miles and then changed, if you are planning on using the car as an everyday runner then stick with the 7b's.

the 8's are lumpy on cold start and running and 9's are worse still, if its a track based car then more det protection is of value and a colder plug would be the way to go but as i see it 7's do the job at a good price and the car drives like OE with them.

stay away from Denso plugs as these have been known to crack the insulator and cause damage in one engine i know of.

Jonny, mine is an everyday driver and ive got 8s on mine. Cold start, sparks up like normal. Spot on

The latest budget 8s are iridium electrodes, so should run a little better when cold compared to the earlier ones. Also the 7119-8 racing 8s (£40 each!) are a more retracted style of plug so tend to run a little worse when cold, but offer better protection against ignition strength problems when running high boost.

There is also an iridium 8 (non racing plug) which I am currently running, and have done for about 5000 miles now. They seem good, but will switch to the new Racing iridiums (they weren't out when I bought mine).

Paul

Speak to Richard at Pentland Components in Edinburgh.

+/- £34 delivered for a set of 7b's. Cant' be bad!!!!!!!!!!!!!!!!!!!!!!

Russell

IMHO 400 is the limit on 7b's and then i would change em before then.

My cold start isnt lumpy on 8's?

I know i would personally rather pay a bit extra for some 8's that will last than buy 7's which 'may' last... especially if i had paid for an engine which i would like to stay together.

In fact, (on my soap box here) if using on track i wouldnt bother fitting 7's for any more than about 360, the continued abuse will deteriorate them much quicker IMO.

Rob