I kno the RX-7 manual and other RX-7 owners advise to use NGK Spark plug, has anyone use HKS irridium spark (rotary heat range) ? do anyone advise it?

 

I use Denso Iridiums, but I don't think that NGK makes a Iridium plug for a rotary engine except for the RX-8

 

I hear Iridiums isnt good for normal street use. im just saying what i've hear not what i kno

 

It is the only plug that I don't burn through in 5K miles.

With a CDI system, using Iridiums is probably worth an additional 5 HP peak

And I only use them on street driven vehicles.

 

Do you know how much those things cost???



-Ted

 

well I spend around $30-$35 retail each for the Densos

 

there not really made by HKS, they just buy em and slap their name on em. good plug tho i have used them i go through a lot less of those than normal ngk's from the parts store

 

I use NGK Iridiums on my car. They are about 7 or 8 a piece at O'reilly's (sp). The only problem is that you have to use a special thin walled spark plug socket (only available at racing beat and mazdatrix for about 60 bucks) to get them in due to the lip aound the spark plug holes. The part number I use is BR9-EIX, I believe.

 

i thought NGK only made platinum for RX-7 n irridium for RX-8
HKS irridium cost $30 each for leading and $20 each for trailing.
hmm then im goin to consider Denso irridium spark plug then

 

BR9EIX are NGK small engine plugs for Mopeds and Snowmobiles.

They are not designed to be a multi electrode plug for a rotary engine and the center electrode is rather limited in size (reducing the available spark size) and as I recall is a single side electrode plug further reducing plug life and limiting spark. Toss in that the BR9EIX is also about 2mm short so you have a minor decrease in compression and bring the actual spark further away from the mixture. BR9EIX are plugs that fit, but are hardly a good choice. And really if you wanted to go the Brix way, Ideally you would want the BR7EIX which was commonly used in some mid/late 60's Porsche 911 product.

If you look at the Denso IRE01-27 (the grown up version of the Brix9) the spark is moved more than 2.5mm into the mixture over the Brix).

The only NGK Iridium plug for the rotary engine that I am aware of is the RE7CL (leading) and the RE9BT (trailing), but the problem is that the gap is .048 radically bigger than the stock gap (stock on the FC is .028) and basically requiring a CDI system to prevent the spark from being extinguished prematurely.

 

I have HKS iridiums and love them. No problems driving on the street. Dont buy them if you dont need them. I needed colder plugs and decided to go this route.

 

Who can truly benefit from these irridium plugs? I'm talking about actual hp gain here. I mean that's not cheap... I've gone through 3 sets of plugs in 10k miles due to various problems that have since been fixed. $30 is really expensive.

 

HKS Plugs == Manufactured by NGK.

Shh... don't tell anyone.

 

im not getting it for just performance only, my plugs r due, n i was wondering is iridium a good choice in reliability n performance then i wouldnt mind paying more, if not they ill stick with platinum NGKs.

 

Spark plugs do not increase performance or power if your original spark plugs were working fine in the first place.


-Ted

 

Iridium and platinum plugs simply last longer. They don't increase performance. Manufacturers fit them to pretty much all modern engines to increase service intervals.

I plan to use platinum leading plugs next time like the FD's do, just for longevity. Currenly I replace leading plugs twice as often as the trailing plugs.

The only thing HKS add to those plugs is cost, so don't waste your money on them.

 

That is not exactly correct.

It has been shown that Fine Wire sparkplugs (.5mm and smaller) do increase the power slightly (typically 1%) over a conventional (2.5mm) spark plugs, due to the more direct arc and reduced combustion influence pattern (quenching) in piston motors (of course I am not sure convinced you can index a plug in a rotory motor to gain anything there or I would mention that as well).

The other advantage with fine wire plugs is that they typically have a lower resistance to firing in the first place. Meaning lower voltage will be required to fire the plug. The is an advantage in aging systems that the coils do have reduced output. This is much more apparent on modifed engines, where additional boost or mixture have pushed past the factory design. This article on a mustang and Irdiums shows there are some gains on these type systems: http://www.sparkplugs.com/pdfs/muscle.pdf

But as you pointed out, with a stock engine, perfectly firing system, no wear on the coils, wires, or the plugs and with the proper plugs, there should be no performance increase when switching between plugs. But unfortantly the inherent design limitations and increased misfires are what fine line spark plugs help cure...

So, in conclusion there are two reasons that Iridiums do actually increase HP, first is because a smaller center electrode requires less voltage to jump the gap. This means fewer misfires, which should be seen in higher mileage and more horsepower. The second reason is smaller center electrodes reduce quenching.

 

hmm, good thread.
good info, seems to be solid.

sticky? no! maybe add to archives?

|M|

 

I have been running Iridium plugs for about a year. I run br10eix. I got tired of replacing plugs every oil change . I think I pay about $20 each.
Thanks Robert

 

You're right!
But without getting into a lengthy discussion into flame kernel and flame front propogation, how many FC guys are willing to spend over $100 for a 1 - 2hp gain (NA of course )?


I want to know how to index the NGK BUR7EQ / BUR9EQ spark plugs?


-Ted

 

You draw a little line on it and call that up/in. Then you can drive mad fast with 25 extra HP

 

Damn, you know all the tricks!


-Ted

 

stick with NGK i change mine once a year with no problems ever. they are reliable and perform fine. i think HKS is just laughing all the way to the bank with these plugs.

 

Where can you get 'em for $30? sparkplugs.com has them for $35.30

 

Just so you know, you can get HKS Iridiums in whatever heat range you need (9-12) for ~$25 each. That's still stupidly expensive when it comes to spark plugs, though.

Bottom line, if you're N/A or turbo making less than 250hp you really shouldn't be spending that much on spark plugs.

That said, HKS spark plugs are great, they didn't foul, or fail in any way through 5,000 miles of supercharged retardation.