kitracer

Working on it mate... working over time.

Surge

iTrader: (2)

You might try a #7 plug. I tried a 6 here in TX and it was too hot.

teammpp

i want to move to Texas . We are lucky if we get enough temp in Europe to get past a no5 plug most of the time .

Surge

iTrader: (2)

Worked fine at 12C ambient this winter.

markp27

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kitracer

I can't say it is universal, but here in HK, I have best result with #7 as well. For Temp from 10c or 30C, I always use #7.
Anything outside of that temp, I stay home...

InitialD

Here, we often get 35 C ambient temperatures and we use 7tf and 0.3 mm shim with no problems too.

teammpp

Dont know what your missing. Our first club race this year the temp was around 3-4 degC. The start of the first BRCA National round weekend the track was coated with ice

If we get 12 deg C before June we are out kissing the ground

markp27

No you won't, you'll be in hospital being treated for extreme heat stroke

teammpp

Surge

iTrader: (2)

Just thought I'd suggest it. Markp27's problem sounded either like a plug or a head shim. I've been running .4mm shims in my Rex with 3rd generation BRB and last weekend on my small local track tried .5mm and it worked maybe a little better. I suggest you try it and see what happens.

teammpp

I thought the same at first. The Novamega cases are the only ones we had this problem with over here. With similar settings they have no Top end power. We only run 16% Nitro over here in Europe. With the Novamega case we are running 1 shim less to give that top end power.

teammpp

There seems to be a lot of confusion regarding shimming and head clearance etc...

Shims are not dictated according to Nitro content, plug or weather conditions etc... Shims are set according to the amount of crankpin/conrod play, wristpin/conrod play, big end bearing play and how tight the P/S fit are.

The key is to find the correct shimming that produces the most power and torque from the engine. The closer you can get the head clearance, the more power and torque the engine will produce.

Many people declare that adding a shim is the correct thing to do when getting pre-detonation or blowing plugs but all they are actually doing is reducing the amount of usable power the engine can produce within its designated powerband. This then means you have to lean the engine out further to regain that lost power which puts the engine under increased stress.

Instead you should aim for a clearance that produces the most power and torque and keep the engine at this at all times. If pre-detonation or post-detonation occurs you should remedy this by increasing the squish area with that clearance to maintain the correct compression ratio. (making the squish area wider or narrower).

This will stop wrong detonation timing but keep the same power/torque level as was previously had. the engine will happily run that bit richer while still maintaining the desired punch from corners and pulling bigger gears.

xtreme888

HI Campbell,

I agree with your statement regarding adjusting the head clearance for most power and torque. I have ran engine with no shim without any adverse effects ( the engine was very torquey !!! With the pre/post detonation parts, how do you change the squish area, i.e wider or narrower ?

Philip

teammpp

Narrowing is not actually possible in a safe way. By wider or narrow I mean making the dome in the button wider or narrower.
To get it narrower you would need to know the exact area required and get a button made to suit. Just a matter of removing material from the appropriate place on an existing button to get it bigger.

I dont advise anyone to go try doing this unless they know exactly what they are doing and can make the proper calculations and changes to get the desired effect.