Better Spark Plugs and hesitations

[Doug_RS2]

Does anyone know what the high power 5 cylinder turbo cars are using as better spark plugs? The cars with more than 400bhp.

I am getting a hesitation at high load and high rpm.

I have tried 2 new sets of the standard bosch plugs. We tried to run higher boost in my car but got this in most gears, so the boost was backed off but it is still there in 5th and 6th gears.

I am trying a different set of coilpacks and amplifiers to see if this is the problem. I have new HT rubber boots fitted.

Any other suggestions? Do coil packs tend to stop working like this? I will check my fuel pressure at at these conditions as well - in case that is fluctuating.

Thanks

[Doug_RS2]

This sounds very similar to my problem:

http://www.sjmautotechnik.com/TROUBLE_SHOOTING/S4_Ignition.htm

[Jamo]

NGK Denso Iridium plugs is what i used to use in my other cars.

You'll probably have to go for a colder plug though, letme see if i can find my old weblink. http://www.spark-plugs.co.uk/pages/t...chw5a-y6dc.htm

Thats the Bosch to NGK guide and on that website and it came back with the following.


Results:
No. Of Plugs: 5
Gap (mm): 0.7
Additional: Incl. S2 MODEL

Standard/Platinum spark plugs
Part No. Price £ per plug Qty. Buy
PFR7B 10.47 5

Iridium spark plugs
Part No. Price £ per plug Qty. Buy
BKR7EIX 8.14 5

[GandalfS6]

@Doug - I changed my plugs to NGK Iridium BKR8EIX (one level colder) and they work beautifully! I also got them from www.sparkplugs.co.uk. Apparently the Denso plugs give even better performance (they are thinner) but does not last long. I went for the NGK's as I never heard of Denso before (I do see them advertising on the Toyota F1 cars now a days.)

By the sounds of your mods, you must definitely not use the 7 heat grade - wheter you use platinum or idirium plugs. You might even want to try 8 and 9 to see which is best. I assume there must be a way to calculate what the right plug is after mods - there must be somebody on here that can work it out!

[Doug_RS2]

I don't understand the colder levels - can someone explain that?

[GandalfS6]

I don't understand the colder levels - can someone explain that?

From www.sparkplugs.co.uk:

Q2. My engine has been tuned/modified, do I need a colder/hotter plug?
A2. You should consult your engine tuner who should be able to advise you on the correct heat range to get the best from your engine. As a general rule, an engine may benefit from a colder grade of plug where modifications made have increased the temperature in the combustion chamber (increased turbo boost, nitrous oxide use, increased compression)

I am sure I saw a post here where Mihnea was talking about the right EGT's.

HTH

[porkkis]

Note that some plug companies use higher numbers for colder plugs and some use lower numbers for colder ones!

[Doug_RS2]

But Mihnea keeps the EGT temps to approximatley the same temperature - he doesn't run the higher power cars hotter than lower power cars. Does this mean we should stick with the standard temp rating of plugs?

I would still like to see what the 500bhp+ cars are actually using.

[Jamo]

But Mihnea keeps the EGT temps to approximatley the same temperature - he doesn't run the higher power cars hotter than lower power cars. Does this mean we should stick with the standard temp rating of plugs?

I would still like to see what the 500bhp+ cars are actually using.

Think of it as an upgrade inline with the rest of your car, the biggest issue is that with increase boost/bhp then the plug should be colder to help prevent detonation. The BKR8EIX would be perfect for your needs, as was said before maybe 9EIX but i would try one grade at time.

http://www.spark-plugs.co.uk/pages/technical/spark_plugs_faq.htm#other_factors

Sparkplugs.co.uk is a fantastic site and you can email them for advice as well. They are the ones who pointed me to a colder plug in my last application and it works a treat.

http://www.ngksparkplugs.com/techinfo/spark_plugs/overviewp2.asp?nav=31000&country=US

That link explains better than i can the hot/cold plug rating.