Outer Limits 4x4 Board

I have just pulled the plugs out and put some equivalent others in and I think they are being blown out.
Pulled Bosch WR8dc and was given NGK BPR5es-11.
Straight petrol , intercooled.

Or are their too many variables between setups for a "across the board" plug.


And I need to know what the gap should be.

Thanks

Depending on how much boost, compression timing, coil and ignition type you won't find a definate answer but I usually run .65 to .8, gapping 1.1's down to .65 might be a bit much though.

Plus I run temp 6 or 7 again depending on other factors you may be too hot although this won't blow them out that's all the gaps work

Thanks. Figured out they must be too hot now, being a four.
Found some the same as what came out.

Check if your engine is ment to run plugs with or with out resistors. made a diffrence to mine on high boost missfiring with the BPR resistor types.

turbmav wrote:Check if your engine is ment to run plugs with or with out resistors. made a diffrence to mine on high boost missfiring with the BPR resistor types.

How would I find that out?
Trying to sort it on about 9psi atm.

Good feedback. Thanks

I'v got a tb42 carby motor and the plugs from factory are BP5ES not BP(R) for resistor. I run straight gas 16psi and found BP7 ES stays preety clean could even go an 8 but your running fuel so I would watch the fouling on anything colder than BP6. Need a MSD or Crane CDI to run higher than 10 psi and gap plugs .7-.8 mm. These are just a few things I did to get mine to run sweet, yours maybe slighty different being fuel. Hope this helps.

From what i can gather a standard Tb42 would run a BPR4ES, but that is for a caby motor, so not really sure.
http://www.frontierpower.com/nissan/nissantb42.htm

In my Gregory's manual it BP5es gap .8 to .9mm.

i run bpr6es with a plug gap of .6 at 8psi

Std plug is a BPR5ES, turbo depends on the quality of the ignition system. The largest plug gap that the ignition system will support is the best. More boost (cylinder pressure) means more heat and a greater the chance of the spark being blown out as does low total ignition timing, so if you have high boost meaning that your total timing is low, less than 10 degrees, you need more spart as the cylinder pressure is much higher due to the piston being closed to TDC. The point is that optimal plug choice, temp and gap will differ from engine to engine depending on peak cyl pressure, fuel octane, intake air temp, and ignition system output. It is also generally accepted to run the coldest plug possibe as long as it dosen't foul. If you are running plug gaps down to .6mm then you are compromising economy and power off boost where a larger gap is more efficient as often the small gap will not be effective at lean cruise mixtures.

Joel

Std plug is a BPR5ES, turbo depends on the quality of the ignition system. The largest plug gap that the ignition system will support is the best. More boost (cylinder pressure) means more heat and a greater the chance of the spark being blown out as does low total ignition timing, so if you have high boost meaning that your total timing is low, less than 10 degrees, you need more spart as the cylinder pressure is much higher due to the piston being closed to TDC. The point is that optimal plug choice, temp and gap will differ from engine to engine depending on peak cyl pressure, fuel octane, intake air temp, and ignition system output. It is also generally accepted to run the coldest plug possibe as long as it dosen't foul. If you are running plug gaps down to .6mm then you are compromising economy and power off boost where a larger gap is more efficient as often the small gap will not be effective at lean cruise mixtures.

Joel