i have been racing my track built fd3s for 2.5 years now without any engine issues and have regularly serviced it. my tuner opted to change the spark plugs to a different heat range without a retune and at my second race event following the change, i blew an apex seal and ripped my turbo apart too.

old plugs: HKS M525 RE - heat range = 10.5
new plugs : HKS M45 RE - heat range = 9

would it be fair to relate the engine failure to the change in spark plugs?

the car is tuned on 100LL AVGAS.

thanks

 

It is reasonable to say that it contributed, but it would have had to be a super edgy tune to cause that, and for 426whp, it shouldn't have to be an edgy tune...

 

That's a pretty good jump in size.
Did the outside temps change(ambient)?

 

ditto that, if it was a conservative tune you would know if the plugs were too much of a change in range, if it is at the opposite end of the tuning spectrum then the plugs will not give a noticable change until the engine just gives up.

were the electrode arms bent or damaged? did he increase the gaps?

i have seen some of the non-surface discharge plugs extend into the housing and touch the apex seals.

 

i havent opened the motor as yet, but i do know that the gaps were not increased as i watched them take the plugs from the box and pur them in.

i am confident that the tune was fairly conservative for reliability as my tuner always ignored my requests for more power and focused on improvingt eh cars handling and reducing weight.

what would i have seen or felt if the plugs were too much of a change inrange?

thanks

Greg