The impact of old coils, wires, & plugs
 

This weekend I had the honor of hosting an EMS tuning session for a bunch of NE region rotary heads. One of the cars we put on the dyno showed signs of weak coils / plugs.

One of the crew had a spare set of brand new OEM coils, wires, and plugs and we swapped them out and got the 8 back on the dyno to finish up tuning and see what kind of measured improvement we'd get.

The sheet below is from a Series 1 RX-8 with original plugs / wires / coils at a little over 30,000 miles on the odometer.

The "low" numbers are before the swap. The high number is afterwards. While not shown, the car was run a couple times after this sheet to verify the final number. It was not a fluke. The car maintained 199-200 WHP consistently after.


That's right folks... 27 horsepower at the wheels tied up in just coils, wires, and plugs.

Enjoy!

How many runs did you measure on the old set?

holyshit...
did the guy have any mods on the car though?

yes, iirc hi flo cat, catback, revi intake and duct

Well done on doing this test . Result is impressive !

quite a few. Jeff took it up as far as he could with the old set setup. That number too is not a fluke.

Thanks Brettus! I knew you'd appreciate this.

that is a lot.

hmm, maybe its time to warranty my stuff, even i have less than 5 k miles on them? just for fun

That's pretty compelling. Linking over to this from my New Owners thread.

That's a HUGE difference.


https://3.bp.blogspot.com/-eQAPZBmwB...r-god-meme.jpg

Added: https://www.rx8club.com/showpost.php...&postcount=613

Thanks a ton for this Shell. Hard facts are always useful.

Not a surprise if you have ever driven a car with failing ignition coils. The first time my stock coils failed years ago I knew it felt like my car was attached to a huge bungee cord, the higher I revved it, the more sluggish it felt. I replaced them the power was all back again. I think most who don't drive hard don't realize their coils are failing until they start getting a flashing CEL.

well done Shell, it's nice to be able to SHOW people that old coils do in fact have a detrimental effect on the car's overall performance.

how many cars did you guys get on the dyno?

Had 7 lined up. One couldn't make it and one had an EFIDude / Mazda ECU model mismatch that prevented him from getting tuned.

And we fit in a Series 2 dyno. Was cool to see its numbers baseline wise compared to the other cars.

this i believe should be stickied to keep it in easy reach and eyesight for new members, and many current members to see. i would imagine the change in MPG's will be noticeable too

Which were??? Nice info, thanks for that BTW!!

that was mine

was 180 hp, 127 ft lb torque, with revi intake and bhr midpipe, oviously no tuning, but jeff felt confident i have at least 20 hp hidden if i could tune

here is my sheet

https://lh3.googleusercontent.com/-3...s543/photo.jpg

That's disappointing. Sorry to hear that. These cars can be all over the place I swear. I have seen guys with almost no mods and higher mileage dyno in the 190-200HP range while others with every bolt on possible only hit the 185-190HP range.

yep, i thought a s2 with low miles would have done better. my 04 w 75k got 188.64hp with a possible failing fuel pump. best i got on a 55shot before we had to abort because it started to lean out was 213-214

It's just hit-and-miss with these engines
interesting dyno Shell...thanks for sharing

another thing some may be interested to know, mine was the only reman engine. it was replaced before i got it at 26k. im at 75k now

bumped to the top

What condition were the old plugs in? I'm asking only because i'm curious as to how much of an impact swapping those made over the coils. Should have done one thing at a time.

All it takes is one bad coil, or wire, or plug in the leading position on one rotor to have that kind of impact. Even one improperly seated plug wire.

This is why my plugs get changed at a maximum of 15k for sure(more like 10k), and the coils every 25k(if I was stock), it's just good insurance.
Thanks for sharing Shell.

Yes, it would have been nice to know if it was plugs or coils....................find it hard to believe it would've been the wires at 30k.

Are old plugs wires and coils likely to cause a rough idle?