Which sparkplugs are you using in a 2.4S?
 

Hi,

I don't understand the Porsche choice of the Bosch plugs for a 2.4S (W3dpo). The engine has only a compression ratio of 1:8.5 and still the plugs that have to be used are very cold. And why ar ethey using platinum plugs? Are there alternatives (NGK!!!!).


Peter
911 2.4s

Peter,

In spite of the low compression ratio of the 2.4's ... all early S engines generate a <b>LOT of BTUs at high speed under load!</b> Hence the factory choice of a cold plug ... suitable for the local Autobahn cruisers ...

My favorite all time plugs were the discontinued Champion Gold-Palladium N-2G and N-3G ... still have a few new-in-the-box!!!

Good NGK choices are the BP-8ES/B-8ES in hot weather and BP-7ES in cold weather when no ambient temps above 40° F are expected ... though current NGK website recommendations are for EVX'-series platinums! Most early 911 owners seem to prefer the plain copper-core plugs over the pricey platinums! There are <b>STILL errors in the NGK database regarding 911 engines!</b>

http://www.ngksparkplugs.com/apps/cars_trucks_suvs/

I'll add my two cents...Info gleaned from the Early 911S registry tech board: Ed Mayo, a respected Texas wrench, says NGK B8ES,
Bosch book says W3P0 to replace the original W26SP21
My mechanic, a guy I trust named Gordon Ledbetter who has a 1973 911S says Bosch W4CS...I'm running them now, with no problems.
I've also heard that NGKB8EV works well...is this a platinum plug?

Now further confused. The NGK plug finder at Warren's link says heat range 7 for 2.4T, 6 for 2.4E, 8 for 2.4S.

David,

Read my warning thread about the errors at the NGK site (already posted above) ...

http://forums.pelicanparts.com/porsche-911-technical-forum/77219-warning-72-73-911e-owners-error-ngk-website-bp6es-bp-6evx-too-hot.html

Thanks,

I think I going to use NGK BP8es or BP8EVX's

To add more to the confusion it's my understanding that Bosch & NGK use different numbers to express the same heat range...

So what is the good plug for 73 911t 2.4?
California hot weather?

I may be going against what S-man has said but a W3 is extremely cold. that plug is used in the 930. however, I did test a used set of W3's in my 2.7s. after a long highway trip they looked ok but driving around town they were black. car still ran fine, started and idled ok.
here is the deal with heat range.
if you just drove a car at speeds and never turned it off and it never idled, you could run a much colder plug (W3). the need for a hotter plug comes from rich idling and rich starting. so the hotter plug is needed so it does not foul.

to answer your question.
make sure the mixture is correct and the timing is correct. you have good wires, cap and rotor.
start with a cold plug and check the plugs every 50-100 miles to get an idea of whats going on with the plug and engine. also note how it starts and idles. keep going hotter if the plugs look bad, IE, black. you don't want a black plug and you don't want a white plug. combustion is going in there so the plug should have some color to it.
note the annealing on the ground strap. you will se a color change. as long as that color change is on the bend of the strap, your timing is OK.
I would start with a W5 copper plug only. if you have carbs you may end up needing a W7.
this also depends on how you drive it.
if you track it I would go a step colder than what you find works best for your car around town.
bosch and NGK use a different numbering system bosch uses low numbers for cold plugs, NGK uses hi numbers for cold plugs. I think around 6 they are about the same.

ngk 6 or 7's. You want the coldest plug you can put in without it fouling. I run 6's now, get dry fouling which matters not as my car runs like a bat out of hell, idles great, etc. MFI's are tricky system, what worked back in 73 with the gas back then, stock/new engines, etc. May not work now.
If you are fouling plugs, J walker suggests running iridium plugs.
I'm guessing this is an mfi car as I know some 73.5 cars ran cis?

Hi, thanks for taking the time to reply. Yes it's an MFI car but I'm not sure what spark plug to use, the car is stock
Do I use BP7EVX or BP7ES or BP8ES ?

try the 7es, 8's might be a tad to cold.