Since many RX-8's will be upgrading to forceded induction I have a concern to address. Since we will be "boosting" should we get colder spark plugs? Are RX-7 spark plugs the same? Is there a colder spark plug for the 8?

See The thread I had started under Greddy Kit get's mentioned in RX Tuner Magazine. Has some info on this situation.

See The thread I had started under Greddy Kit get's mentioned in RX Tuner Magazine. Has some info on this situation.

No offense Fanman, but I'm trying to get somewhat of a discussion relating spark plugs in regards to forced induction to this parent "topic." As hard as it is, it gets pretty perplexing combing out relevant materials in the forums especially when the relevant material is different from topic heading. Please understand my frustration. Thanks for the feedback by the way.

So far as stated by dannobre there is NGK RE8A-L from Japan... however is that trailing or leading or does it matter?

Canzoomer supposedly sells a colder mazdaspeed spark plug, but I'm not aware of anyone installing or having them. He would be a good source to check first on that.

No problem, I'm not offended. Actually I would like to learn more as well. According to Can Zoomer (product list/price guide) the MS RE8A-L (which they are selling for $94) is Leading. I got a set from IZoomZoomI so maybe he can chime in.

I too would be interested in these sparkplugs. Any more info? Perhaps cut and paste the above mentioned relevant info?

found some colder plugs on this site

http://www.sparkplugs.com/results_app.asp?productTypeID=1&AAIA=1416844

Any thoughts?

Also they have a good price on the stock plugs too boot

No problem, I'm not offended. Actually I would like to learn more as well. According to Can Zoomer (product list/price guide) the MS RE8A-L (which they are selling for $94) is Leading. I got a set from IZoomZoomI so maybe he can chime in.


No trailing plugs are available from what I remember. Yea the re8l plugs are leading plugs from NGK and are the only plugs available at the time. It allows you to advance the timing a few more degrees compared to oem. I wouldn't recommend them if you live in an area where it gets real cold though, risk of flooding is a lil higher with these on.

Colder plugs are a last line of defense against knock.
This isn't an issue at the low boost levels and conservative timing of the current systems.

The detrimental effects of a colder plug will far out weigh the advantages.

What would the detrimental effects be ? I'm curious, as I would like to know more. I do want more reliability if I decide to go to 7-8 psi on the turbo. Why would Greddy dial the decrease in boost on our engine at upper RPM ? Are they being ultra conservative ?

What would the detrimental effects be ? I'm curious, as I would like to know more. I do want more reliability if I decide to go to 7-8 psi on the turbo. Why would Greddy dial the decrease in boost on our engine at upper RPM ? Are they being ultra conservative ?
Colder plugs foul more easily.

What decrease in boost are you talking about?

Colder plugs foul more easily.

What decrease in boost are you talking about?
He's talking about the decrease in boost when the tertiary ports open that is not related to greddy's tuning but the lack of a boost controller in their setup.

He's talking about the decrease in boost when the tertiary ports open that is not related to greddy's tuning but the lack of a boost controller in their setup.
Hmm. Interesting.

Has anyone actually graphed this?

I have a small dip in power when the 3rd port opens, but no dip in manifold pressure. This is due to a sudden change in the A/F (slightly lean then suddenly rich) that can be tuned out to a degree.

A boost controller wouldn't help that much if it were a dip - wastegates have a limited response.

Hmm. Interesting.

Has anyone actually graphed this?

I have a small dip in power when the 3rd port opens, but no dip in manifold pressure. This is due to a sudden change in the A/F (slightly lean then suddenly rich) that can be tuned out to a degree.

A boost controller wouldn't help that much if it were a dip - wastegates have a limited response.


Jeff, I noticed roughly a .75psi drop when the 3rd port opens. However, the boost catches back up and I hit 7psi a fraction of a second later.. I noticed that from reviewing my gauge logs since I can record what the display with the defi link.

I would think you could go to 8-9psi reliabily on our stock sparks, fuel injectors and internals provided you have a proper BOV, monitoring systems and boost controller.

From what I understand, the first problem people are likely to encounter would be the fuel injectors correct?

What decrease in boost are you talking about?

MazdaManiac,

This was a quote from this month's RX Tuner :

"Horsepower instead of the previously promised 303 flywheel horsepower, the new numbers have been lowered a bit. Reason being is that now, instead of holding a consistent 7 psi of boost, the turbo will slowly drop above 6500 rpm to around 5 psi of boost at redline. Reportedly this is done because Greddy has not been able to source suitable colder spark plugs for the Renesis."

I would think you could go to 8-9psi reliabily on our stock sparks, fuel injectors and internals provided you have a proper BOV, monitoring systems and boost controller.

From what I understand, the first problem people are likely to encounter would be the fuel injectors correct?
Yes - 9 PSI would be the limit for the factory injectors at factory pressure and 80% - 90% duty cycle.

MazdaManiac,

This was a quote from this month's RX Tuner :

"Horsepower instead of the previously promised 303 flywheel horsepower, the new numbers have been lowered a bit. Reason being is that now, instead of holding a consistent 7 psi of boost, the turbo will slowly drop above 6500 rpm to around 5 psi of boost at redline. Reportedly this is done because Greddy has not been able to source suitable colder spark plugs for the Renesis."
Interesting. Jon's system doesn't seem to exhibit this.
I wonder how they plan to accomplish this since there is no electronic boost control in the E-Manage.

Hmm. Interesting.

Has anyone actually graphed this?

I have a small dip in power when the 3rd port opens, but no dip in manifold pressure. This is due to a sudden change in the A/F (slightly lean then suddenly rich) that can be tuned out to a degree.

A boost controller wouldn't help that much if it were a dip - wastegates have a limited response.
As I don't have one, I don't know, but it does make sense to see a slight drop in pressure and then a recovery in it if the turbo output enough CFM to keep up with the greater flow with the ports open.

As far as the limited response of a wastegate, i'm gonna say I have limited knowledge of how they're controlled anyway, but if you wouldn't mind explaining that, i'd appreciate it. I wonder if someone has built a truly electronic wastegate using a solenoid valve and electronic controls. That'd have nearly instantaneous switching speed and unlimited dwell controls.

Although colder plugs are a last line of defense against detonation they may still be crucial in certain FI/nitrous apps. because the spark plugs perform a number of other tasks as well. With boosted apps. over a certain level the combustion temps will be raised so we need colder plugs to more quickly carry away a larger portion of the heat to prevent heat related damage. With my modest 55 shot I have yet to swap plugs but with the addition of FI I most certainly will need to. So far I think the 55 shot and 5-7 psi are quite comparable in terms of effects on a stock engine, i.e. no adverse effects. One other thing; I facetiously ask if there is a possibility that the automotive aftermarket functions like the computer software industry with regard to beta testing and, if so, could that beta testing be marketed as "designed for user upgradeability". In other words, GReddy isn't quite sure what the max performance potential is of their new turbo kit but with our help, they'll soon find out. Anyone agree with this theory?

CRH

In other words, GReddy isn't quite sure what the max performance potential is of their new turbo kit but with our help, they'll soon find out. Anyone agree with this theory?

CRH
If Mazda can do it that way, why not Greddy?

As far as the limited response of a wastegate, i'm gonna say I have limited knowledge of how they're controlled anyway, but if you wouldn't mind explaining that, i'd appreciate it. I wonder if someone has built a truly electronic wastegate using a solenoid valve and electronic controls. That'd have nearly instantaneous switching speed and unlimited dwell controls.
That is how a boost controller works - it has a solenoid and it has dwell and duty cycle control over the wastegate actuator.
The actuator itself is just a rubber diaphragm attached to a piston with a rod mounted in it at a 90° angle to the action of the diaphragm.
When it is pressurized, it extends by an amount controlled by a spring. It is the spring that decides the minimum opening pressure of the actuator - the boost controller can then increase that opening point by modulating the amount of pressure that the actuator actually sees.
Ideally, you want a spring that allows the actuator to open completely all at once and at a low pressure. However, this isn't possible. It will typically "crack" at a starting pressure and be completely open at another pressure that is usually 100% above the cracking pressure.
So, aim for a fully open pressure that is 75% of your target boost when selecting an actuator (in reality, finding an actuator that is set for your desired opening pressure is like looking for a needle in a haystack - they are seldom "rated" or marked in any way, so you need to test them with a pressure gauge and a pump. At $75 a pop, that can get to be difficult).

So, Jeff, are you validating the idea that there is much room for tuning improvement on the GReddy kit as it comes from the factory? Do you think that GReddy watches this forum to take a few hints from people like you and I with regard to the potential of the RX-8?

CRH

So, Jeff, are you validating the idea that there is much room for tuning improvement on the GReddy kit as it comes from the factory? Do you think that GReddy watches this forum to take a few hints from people like you and I with regard to the potential of the RX-8?

CRH
Well, not exactly.

At the supplied boost, it is pretty good, though I might be inclined to go 1/2 point leaner in parts of the RPM and load range.

I think one can safely go up about 2 PSI from the way it comes from Greddy. I can run well into the 11:1 range at 9 PSI with the OEM injectors with my E-Manage setup.

I'd like to see their MAPs once they finally send them to Jon.

This by the way hints at another advantage of a good electronic boost controller. The solenoid typically changes the air pressure seen at the wastegate so you can "fool" it by giving no pressure up until you reach your target and then letting it see full pressure all at once. This allows the turbo to maintain full boost up until it needs to stop, and then quickly stop building...another "area under the curve" problem that you can't really solve with a simple mechanical spring.

There was a good article floating about the internet describing how this all works but I can't find it right now.

jds

That is how a boost controller works - it has a solenoid and it has dwell and duty cycle control over the wastegate actuator.
The actuator itself is just a rubber diaphragm attached to a piston with a rod mounted in it at a 90° angle to the action of the diaphragm.
When it is pressurized, it extends by an amount controlled by a spring. It is the spring that decides the minimum opening pressure of the actuator - the boost controller can then increase that opening point by modulating the amount of pressure that the actuator actually sees.
Ideally, you want a spring that allows the actuator to open completely all at once and at a low pressure. However, this isn't possible. It will typically "crack" at a starting pressure and be completely open at another pressure that is usually 100% above the cracking pressure.
So, aim for a fully open pressure that is 75% of your target boost when selecting an actuator (in reality, finding an actuator that is set for your desired opening pressure is like looking for a needle in a haystack - they are seldom "rated" or marked in any way, so you need to test them with a pressure gauge and a pump. At $75 a pop, that can get to be difficult).

...so what kind of potential damage can be said about using the spark plug (leading) that is one degree colder???

...so what kind of potential damage can be said about using the spark plug (leading) that is one degree colder???
Go back and read post #12 in this thread.

Thanks for the reponse Jeff. I guess stock injectors all the way around.

i meant spark plugs. ;)

...then injectors, lower compression, fuel return (not sure how that works with the Renesis reusing unburned fuel)...

I just bought a spare set of factory spark plugs for my RX-8. You know what.. they are the same damn spark plugs that they use in the 93's... I am amazed.. all this crap about different plugs when I could have been using '93 race plugs the whole time.. argh..

I used the plugs you're talking about but they don't fire as well as the iridiums. There was a noticeable difference.

CRH

I just saw this thread, interesting...
As you can see in my signature, I have the GReddy plugs with the code RE10.
I'm not an expert, but I changed them because I had some starting problems (never flooded though). A friend had them on his car and recommended them to me. Since then I have no problems at all, even at cold weather (3-5 degrees C). Maybe someone can comment on this. They are made from iridium and they were considerably larger than the stock (size matters right;) ) Here's a pic too.

By the time I need plugs that cold I'll be at 7 psi and 100+ h.p. of nitrous. Thanks for the heads-up, though.

CRH

I just saw this thread, interesting...
As you can see in my signature, I have the GReddy plugs with the code RE10. Εκείνοι το ίδιο πράγμα για "leading" και "trailing"?

Jeff sorry, but what do you mean? And when you say "Colder plugs foul more easily"?
;)

Sorry, I speak it much better than I can write it. :p

Are those the same plugs for the leading and trailing? Colder plugs don't get as hot (by definition) so at lower RPMs and rich A/Fs they get fouled.

Heh, I got the Greek part, I didn't get the "leading and trailing" one :p
From what charles said, it sounds that colder plugs are bad... or good? Do they help at any point?

Well, the "hotter or colder" issue is about resistance to detonation. In short, if you decrease the engine's resistance to detonation (pre-ignition, knock, whatever - that is a whole other discussion) via the introduction of high combustion pressures and/or temperatures, a "colder" plug will help negate the possibility of detonation to some extent by removing more heat from the combustion chamber. However, the penalty is the plug, being colder, is unable to burn off the film of un-burned fuel that accumulates at low RPM, low load conditions.

The "trailing/leading" question was directed to the number of the plugs you installed.
The rotary engine uses two plugs per rotor - one fires before the other to complete the combustion process.
In a stock Renesis, the trailing and leading plugs are different. I was wondering if you replaced all four of the plugs with the Greddy RE-10s or not.

yep yep, all four of them, that's why there are four plugs in the pisture;)
when I look at the stock ones, they all seem to be the same though...
great info, thanks:)

Interesting. That shouldn't work very well, if at all.
I may have to get a set of those to experiment! Efharisto.

well at least in 3rd gen rx7's I always ran 9's all the way around with out fouling or tough starts(except when broken;) )

Yes, some people use trailing plugs in all 4 plug positions since the trailing plugs are a "tad" bit colder than leading.

Interesting. That shouldn't work very well, if at all.
I may have to get a set of those to experiment! Efharisto.

Parakalo:) please do experiment with them, and tell me what you think Jeff! these plugs are not so expensive, you should find them less than $150. Until now they work well:o hope the same for you!

Parakalo:) please do experiment with them, and tell me what you think Jeff! these plugs are not so expensive, you should find them less than $150. Until now they work well:o hope the same for you!
I've found them for $28 USD each in a couple of places. I'm just not so sure that a 10 heat range is the right choice.
The stock trailing plugs are 9 and the leading are 6 or 7.
Seems to me that running a 9 in the leading would be the coldest I would go.
So, maybe I will get a pair of RE-9 and have a go in just the leading plug first.