spark plugs not looking so good.... some tip missing!
 

so i pulled my plugs out today and found they dont look so great. i have since been running a 100 octane leaded race fuel mix ( race and pump ). car has been running very strong considering i have been running on 13.5 psi. but what could cause a part of the plug tip to be missing? the missing plug tip was on the front lower. here are some pics.

front lower , front upper
http://i202.photobucket.com/albums/a...7/000_0158.jpg

rear lower , rear upper
http://i202.photobucket.com/albums/a...7/000_0159.jpg

Call me stupid but i thought you were suppose to use different plugs than those. You know, the ones that are flat on top.

i have been running the ngk 5820's for a while without any issues. i have only had an issue since i began running race fuel. they are very similar to a b10egv with a 10 degree heat range.

from what i have been reading it appears to be lead erosion. i have been running vp c16 so that would make sense. how often do you straight race fuel guys change plugs? i believe these have about 300-400 miles of use with leaded fuel.

You might have to shell out some money for the expensive ones...

never had an issue with these plugs until now. looks like i will have to pick up a set of the b10egv's. seem to work great for everyone. i plan on running race fuel most of the time so i need a plug that will work under the conditions.

Whats your timing look like?

this timing setup is used for race fuel only, 16 deg. IGL with a 6 deg. split. i am thinking about changing over to ms109 unleaded race fuel. only issue is that it is only 105 motor octane. so i may run that with a 50/50 a/i. i am looking to run 20-22psi on my 35r.

wow, i run the EGV's on mine with race fuel. this is what they look like after much abuse.

Leading on top, trailing on bottom

http://i3.photobucket.com/albums/y54...u/DSC07493.jpg

http://i3.photobucket.com/albums/y54...u/DSC07494.jpg

try swithing back to the egv's....and monitor them?

Unleaded fuel only

Both sets look like crap the bottom set looks like they have been fireing in water and rusted.
The top plug looks like it burned off.
When i have run leaded it always looks white, also they look dry like no oil. Premix?

Same here. Mine have never looked that bad. However I pull plugs and clean them more than I drive the car.....

I've had so many problems with aftermarket plugs. From now on, it's stock for me (BUR9EQ). My stock plugs are handling 1700 degrees pre turbo EGT just fine, pump gas at 15.5psi. Timing is 10 degrees at peak torque advancing up to 17 at redline, 15 split over 10psi boost. I used to run the BR10EIX with race fuel and they just couldn't take the heat, despite being rated as a colder plug (meaning more heat dissipation due to insulator design). The colder plugs also require additional tuning to maintain a smooth idle. Plus you have to use the stupid thinwall plug socket. I managed to round the hex of a plug using that thing, which was a huge bitch to get out.

Considering how hot the exhaust gets on stock nonturbo cars (easily 1600-1700 degrees) and they only run the hotter BUR7EQ's from the factory, I'm not worried about it. The porcelain on my BR10EIX (admittedly, the fine wire irridiums) would crack without detonation. HKS says not to use non-resistor plugs (such as B10EGV) with the Twin Power and considering how expensive those things are I wasn't going to risk it.

i have never had an issue when running 93 octane fuel. since i changed to a leaded race fuel mix, is when the plugs pulled out like that.

** also on the plugs i labeled them incorrectly. the plugs that look rusty were both the trailing plugs. the plug with the missing section was the front leading. the other next to it was the rear leading.

could running a 16* IGL with a 6* split on 100 octane at 13psi really run that hot? fwiw my previous setup was 14* IGL with a 10* split on pump and i would run up to 16psi, this was on pump only.

your timing is nothing crazy.... I would run the stock 9's all around for what you are doing. Once you hit the 450 up area you can do the 10's or such but I would stick with the $$(35) NGK ones.

What is your a/f ratio it looks lean to me but i dont claim to be an expert.
Also i would add some premix those things look dry.

I run the expensive 10's year round and have changed plugs 3 times in 3 years and never fouled a plug.
Hell i drive 15 miles to the track and run tens and drive home....i know ive been lucky.
Good luck man, makes you wonder were that piece of plug went!:dunno:

i run a full time wideband and it runs in the mid 11's for an afr. i hope that piece of the plug melted. i did a compression test just to make sure everything was in check, but still doesnt mean i didnt nick anything in the motor. i have ran stock 9's plugs and they would break up on the top end after running them for a few hundred miles. on my pump gas setup i have no issues with these plugs. i am going to drop that tune back in and look into running unleaded fuel.

whats the max boost i would be safe at running 105 motor octane? this is with a 14* IGL and a 10* split.

Im not the right guy to ask about boost and fuel......im running 20psi on 93 pump only but im running 8.5 s4 rotors.

Good luck hope it doesant do this again!:icon_tup:

how far can you run the stock 9's all around? i am making 480whp now on full c16 and dont want to have a plug issue again.

here's my logic. the stock motor surely runs hot as balls in terms of air, water, and exhaust temps. Yet it still has 7's in the leading. 9's are two steps colder. that's a big difference.

You may want to read this thread, good info that may help you re: spark plug choice:

https://www.rx7club.com/rotary-car-performance-77/why-apex-seals-fail-866513/

I'm at similar power and boost levels, and I'm running NGK 6725s 10.5s all around. A bit too cold for my application, I just got a set of NGK 7420s in from Japan, 10s leading and 10.5s trailing.

FWIW, I recently swapped back to 9s to see how they felt. Didn't change anything else. Idle quality and sub 2000 rpm was much smoother. However, WOT pulls surprised me---the car felt more flat, and above 5000 rpm it sure felt down on power. This was at only 15 psi.

It may have something to do with the water injection.... regardless, for the amount of time I drive my car (and the amount of money dumped into the engine bay) I have no problem running expensive spark plugs if it's going to maximize performance.

thanks for the link. i am also actually changing my turbo for a gt3567r which is basicly a 35r turbine wheel with a 67mm compressor. it was a design by full race, have to see how it works but i would expect at least 10-20whp up top. so i will need a plug that is always running at 22+psi and around 500whp.

Sounds like full race basically copied the A Spec 500R.

Based on that, we should know exactly how it will work :lol:

6725s/7420s are your friend ;) The 7420 are iridium and may be the best choice for guys like us. I have been able to source some from overseas and may be placing another order soon so please let me know if you want some. Not cheap, around $35-40 per plug.

Rich, your stock plug vs. 7420 comparison. Was that new 9's vs. new 7420's?

I did a similar (ok ok exact same :) NGK7420-10's and 10.5) test in my car this year. Similar results, but the 9's I changed from were fairly aged, not dead but not new either. Maybe 5,500kms of street and hard driving on them.