Thanks.

They have 'em in stock here at Nopi (IK-24s).

I'll probably just stay with Densos as I haven't seen the NGKs locally in Atlanta.

 

I got this info a while ago from k-huevo:
note: for IK22 equivalent
Originally Posted by k-huevo
The NGK Iridium equivalent to the IK 22 is BKR7EIX. I set the gap to .035 to be on the safe side.

 

Good. That would make the IK 24 equivalent what I had found, BKR8EIX

 

I've been using these NKG's from Mini Mania since I had misfires with my Iridiums two years ago. No more problems. That's been with 19% pulley.

NGK BKR7EKU

http://new.minimania.com/web/Item/NM.../InvDetail.cfm

 

Well, sure, I understand that the outside air affects the temp of the entering fule/air mix. But once the spark plug sparks, and the combustion happens, this is what, maybe 1200 F? Does it really matter to the spark plug if the air temp outside is 60 or 100 F? Do you argree with the idea that when it is hot outside, a colder plug is more useful than when it is cold out? I have a hard time believing this.

 

let's say you get some detonation at peak pressures and temps in the cylinder, and its' at 1150 degrees. If cool days have the car hitting 1130, no timing retard, because there is no detonation. Hot day, you get the timing retard.

A lot of this has to do with how engines are controlled now. Using computers and sensors, the cars are tuned to the ragged edge. It takes less to push you over the top,. so to speak, than it did when the cars had carbs and no knock sensor, and the tunes were much more conservative.

Another way to look at it is how much power do hot days sap from your car compared to cold days.... It's a lot, isn't it?

Matt

 

Based on Obehave's Screamin Deamon coil and its higher output, could it be that the higher output has caused the erosion of the electrodes? What gap was used for the IK22s?

 

John,

The plugs are the ones in the picture. After the first limp home mode (5 min into the first track session) I went to the pits and checked the wires and looked for any other loose items. Everything looked good, that's why I thought it might have been the gas (filled a half tank near the track).

I added a can of octane booster which seemed to help, at least it took longer before the engine started to miss again. It went into limp home mode again after about 15 min on the track. It started to miss after 10 min, getting worse as time went on.

I guess these plugs just don't last that long.

I didn't measure the gap but i can when I get home tonight. I have a set of IK-22's on the way, should be here by Thurs.

 

Exactly

On a hot day you loose a lot of power. The engine is just like you, how well do you do on a hot humid day?
Timing retard can hurt the plugs, create more EGT & loss of power. With engine management some of the power loss is minimal compared to the old days without it. Detonation was pretty common in the 60s & 70s drag racing age. You had to get a handle on the EGT to set the AFR & IGN timing. You also needed to be good at reading the plugs, an art that is still valuable today. Heat is not your friend if you want power in the summer. Bottom line, the cool weather will show the true color of the IK24s.

 

So you guys are saying a colder plug will not induce as much timing retard as as a standard plug due to a hotter incoming charge, which is more prone to detonation than a cooler charge. I can accept this. Might be interesting if some one actually measured how much less timing retard occurs using a cold plug vs the stock plug (hint to Matt). But the timing retard issue is completely separate from the "hot air loses power" arguement based on the lower density of ambient hot air. I mean, even if there were a fanatastic IC that cooled the initially hot air way down so as to eliminate timing retard, power would still suffer with hot ambient air.

 

There were a couple posts here by non SD coil users so I think it is just an issue with the plugs.

The coil only outputs 4KV more so it isn't that big a boost. A bump from 36 to 40 if remember right.

 

My post was kind of pulling at straws.... But I am curious; do you remember what gap you used for the IK22s?

 

inmmini, colder plugs don't realy have much to do with timing. What a cold plug can do is save it self from burning itself & depositing it's own material in the combustion chamber. This material can cause lots of hot spots creating a run away situation ( IE. it just gets hotter ). Timing on a modern car is controled by the engine management, O2, MAF, etc. The criteria the ECU knows ( OE maps which include pulse width & fuel injector timing as well as IGN ), the ECU will react to what it sees at spacific events. There are instruments that can measure this criteria that most of the tunners have, MTH, Unichip etc, although I don't think any of the tuners or BMW would tell you exactly how they mix their fuel to ign tuneing. However you make an interesting point, I would also like to know, does, in fact, a colder plug reduce ign retard? IMHO the answer is no, but a cold plug will help to stabilize combustion at high temps, so maybe......

 

.032 In hindsight this looks like a good idea

I had run my IK20s pre pulley at .045 with no issues.

 

but in several books I've read, there are claims that a one step colder plug will reduce combustion chamber temps about 75 F. Now I'm sure there's a lot of play in that number, but by making the heat conduction more efficient to the coolant, the metal temps in the combustion chamber will be cooler, and the peak temp in the combustion chamber will be cooler as well. At least that's the story....

Matt

 

Thanks Matt,

Pretty tough to measure pulg temp.... A colder plug will run pretty darn hot when you are making big power. The 75F figure would be a good figure, but at what AF, ign timing...... The more power you make the higher the combustion temp. The plug won't help too much with heat transfer but it will help with the burn efficency to get to that big power. This is 1 of the reasons an EGT was so important, much like an O2 sensor to an ECU, it would give us the right ( maybe ) direction to go with plug choice & jetting ( jetting first ). Too much timing, not enough timing, too lean = big temp = melted ring lands & burnt plugs, if you did not shut down = a big paper weight or scrap. The IGN is a different animal, fuel pulse width, as well as exact IGN time corrected for the fuel injection, at different RPM ranges can make or break a good tune. At the GTP IMSA races you would see a guy with a laptop adjusting for weather conditions. Since that time engine management has come light years, rember carburators, there is a whole generation of people that have never seen 1. Anyway, back to the IK24s, IMHO, they, or a same heat range plug of your choice may be a good choice for a slightly modded Mini. What I'm saying is that if you can give me better temp control, I'll take it and make more power out of it, if it's 75F I'll take it.....

 

So should we be asking ourselves . . . are irdiums, in general, better than the other choices that are available?

 

I'm at that time where I want to get new plugs (IK22's have about 25k miles), so I'm all ears on this topic...

 

"So should we be asking ourselves . . . are irdiums, in general, better than the other choices that are available?" Oh boy, that is a good question.
For now, could be. So far they are the best for this car. The NKG was the best plug we used in our shifter engines. They were the most reliable with a magnito, we could run 1400F for EGT without a failure. So there are many plugs that have not been tried, or I should say that have been posted here on NAM that may be better.

So many plugs..... So little time.....

 

From what I can tell, yes. One of our other cars is a Honda Insight; where maximum efficiency is required. The plug gap is over .1mm and the A/F ratios can get to 22:1. It comes stock with Iridium plugs. Several people have taken them considerably longer than the 105k mile replacement interval without problems. I'm thinking the issue is more in the MINI than the plug.

 

Bruce,

If you haven't already read the link in post #19, please do. Might give you some useful data on which to base an answer to the question you ask.

Regards,
John Petrich in Seattle

 

Based on thta paper it's easier to see why the NGK with a .7mm electrode will last longer than the .4mm Denso.
Conversely the Denso will be the better of the 2 for performance.
I'll take performance.

 

Thanks John . . . the paper was very informative.

 

One line of inquiry I have been following on another board (Corvettes) calls for .060 gap.... I am wondering, split the difference? (Especially if you had IK20s at .045...; maybe it is time to go back to .045???)

 

the new corvettes have coil on plug or coil near plug ignition. I think that's a 100kV system. They should be running larger gaps...

Matt