Best Spark Plug for good price $$$
Evolved Member
Joined: Jan 2003
Posts: 1,121
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Here is a direct cut and paste from page 16-35 of the Evo's service manual:
SPARK PLUG CHECK AND CLEANING M1163004300278
CAUTION
• Do not attempt to adjust the gap of the iridium plug.
• Cleaning of the iridium plug may result in damage to
the iridium and platinum tips. Therefore, if carbon
deposits must be removed, use a plug cleaner and
complete cleaning within 20 seconds to protect the
electrode. Do not use a wire brush.
Check the plug gap and replace if the limit is exceeded.
Standard value: 0.7 - 0.8 mm (0.028 - 0.031 inch)
Limit: 1.0 mm (0.039 inch)
The owner's manual is wrong. The service manual goes on to show electrical waveforms to diagnose spark plug gaps that are too small or too large. In other words, not your typical owner's manual stuff. Which is why I trust it more than the owner's manual.
SPARK PLUG CHECK AND CLEANING M1163004300278
CAUTION
• Do not attempt to adjust the gap of the iridium plug.
• Cleaning of the iridium plug may result in damage to
the iridium and platinum tips. Therefore, if carbon
deposits must be removed, use a plug cleaner and
complete cleaning within 20 seconds to protect the
electrode. Do not use a wire brush.
Check the plug gap and replace if the limit is exceeded.
Standard value: 0.7 - 0.8 mm (0.028 - 0.031 inch)
Limit: 1.0 mm (0.039 inch)
The owner's manual is wrong. The service manual goes on to show electrical waveforms to diagnose spark plug gaps that are too small or too large. In other words, not your typical owner's manual stuff. Which is why I trust it more than the owner's manual.
One thing to keep in mind guys is as you switch from plug manufacturer to manufacturer, gaps may vary well vary.....
We have the Denso Iridiums in stock for the Evo (one step colder than stock) which are $58 a set shipped in the 48 states. Only 6 sets available as of right now, more are on backorder.
These come pregapped at .028, though its best to double check prior to installation
Adam
We have the Denso Iridiums in stock for the Evo (one step colder than stock) which are $58 a set shipped in the 48 states. Only 6 sets available as of right now, more are on backorder.
These come pregapped at .028, though its best to double check prior to installation
Adam
Last edited by Z1 Performance; Jul 14, 2003 at 10:41 AM.
I just gap checked the FACTORY NGK Iridium plugs that came out of my EVO and they are gapped to a TIGHT .024 to a semi-tight .025.
.026 and above is way to tight. Therefore I have confirmed the factory gapping is .025 on ALL four plugs.
hehe shape - I meant feeling snappy by the boost just doesnt come on as hard as it did prior with the Iridiums.
.026 and above is way to tight. Therefore I have confirmed the factory gapping is .025 on ALL four plugs.
hehe shape - I meant feeling snappy by the boost just doesnt come on as hard as it did prior with the Iridiums.
I have an Evo 8, I have put over 2500 miles on NGK B9ES. I also raised the idle to about 850 / 1000 to avoid low speed fouling. 1 thing I noticed with the stock plugs, was the idle was really low. I live in Ca. & it seems that the ig map was globaly reduced due to knock, resulting in a lower idle. If I reset the ecu, the idle was high, jump on the gas for a bit, WHAMO, I have a lower idle point. After installing the B9's, this phenomenah was greatly reduced. I plan on buying some B9EV's which have a smaller electrode, i.e. less prone to detonation due tothe smaller electrode tip.
But 1st I wanted to see if this heat range was okay for city driving, which I do 95% of the time! I hope this helps out.
NGK ALL THE WAY.
But 1st I wanted to see if this heat range was okay for city driving, which I do 95% of the time! I hope this helps out.
NGK ALL THE WAY.
Evolved Member
Joined: Jul 2003
Posts: 638
Likes: 7
I beg to disagree. Fine wire elctrode plugs are used specifically in racing applications to increase the reliability of the spark. Also in racing you usually gap on the tight side (not too tight!) to decrease the likelihood of misfire. The size of the spark is not considered to be that relevant though admittedly a larger spark may give a minimal power advantage but the increased risk of misfire is hardly worth it, as with the latter any potential power advantage rapidly disappears.
Originally posted by timzcat
The small center electrode plugs suck because the surface area for the spark to jump to is small. It may require less energy but you will get a larger spark on a normal electrode. Look at a spark plug when it fires. It is not 1 simple spark but more of a broad spark. On a small center electrode there is less surface area. Especially in the case of a boosted car because the cylinder conditions are more demanding then an N/A car. This is why they are generally not recommended. Normal plugs or the larger center electrode are clearly better.
The small center electrode plugs suck because the surface area for the spark to jump to is small. It may require less energy but you will get a larger spark on a normal electrode. Look at a spark plug when it fires. It is not 1 simple spark but more of a broad spark. On a small center electrode there is less surface area. Especially in the case of a boosted car because the cylinder conditions are more demanding then an N/A car. This is why they are generally not recommended. Normal plugs or the larger center electrode are clearly better.
EvoM Guru
Joined: Apr 2003
Posts: 559
Likes: 0
From: D/FW, TX
Fine wire electrodes are also a potential source of detonation with high boost. The sharper the point, the more likely it is to happen. It isn't worth the risk to me.
I mean all of the manufacturer test data I have seen seems to indicate that the iridium plugs perform better in every regard.
Add to that the fact that Mitsu saw fit to use them in this car in the first place, kind of says a lot to me.
BTW My original stock plugs were gapped at .028 when I pulled them out, I bought a replacement set from the dealer and they were pre-gapped at .026
The denso comparable replacment plugs WI20/WI24 spec sheet indicates that they should be gapped at .028.As has already been mentioned, the shop manual says .028-.030, I would go .028 unless your running major boost, then maybe go lower. Standard plugs with a larger electrode, that can not fire off as easily should probably be gapped lower to begin with. Although I also would not recommend using standard plugs, of course thats just my opinion.
Last edited by SILVER SURFER; Nov 10, 2003 at 08:13 PM.
Evolved Member
Joined: Jan 2003
Posts: 1,121
Likes: 1
Sharp points in the combustion chamber create hot spots. Hot spots can lead to detonation.
Iridiums are good for longevity in applications that cause a lot of plug wear (turbos).
But I'll only use $8 per set NGK copper plugs in my car. So what if I change them 3 times a year? I run 26psi at the track, and I don't need sharp points in the combustion chamber.
Iridiums are good for longevity in applications that cause a lot of plug wear (turbos).
But I'll only use $8 per set NGK copper plugs in my car. So what if I change them 3 times a year? I run 26psi at the track, and I don't need sharp points in the combustion chamber.
Newbie
Joined: Sep 2003
Posts: 93
Likes: 0
From: Fallston, MD
I had a set of NGK Iridiums that were "pre-gapped". The car ran fine at 18 psi but at 20 psi it would misfire badly. I took the plugs out, checked the gap, and every one of them were .040". I gapped them down to .028" and the car ran great even at 24 psi. If I can run 18 psi with .040" gap, then there's no way .028" is too large a gap for an EVO running <24 psi.
Only problem with the iridiums is I definitely see more knock with them. They are probably too hot a plug. But the original question was the best spark plug for a good price. I paid $40 for my set of iridiums and even that price is too high for plugs in my opinion. NGK BPR7ES's work the best for me, and if I run into any misfiring problems with them, I will switch to BR7ES's. For $10 a set, I don't understand why people buy into the hype.
Why does Mitsu use them on the EVO? Because a lot of people who pay $30k+ for a car will pay $120 for a set of flashy spark plugs (and Mitsu probably has an agreement with NGK). Factory parts are always more expensive than they have to be.
Only problem with the iridiums is I definitely see more knock with them. They are probably too hot a plug. But the original question was the best spark plug for a good price. I paid $40 for my set of iridiums and even that price is too high for plugs in my opinion. NGK BPR7ES's work the best for me, and if I run into any misfiring problems with them, I will switch to BR7ES's. For $10 a set, I don't understand why people buy into the hype.
Why does Mitsu use them on the EVO? Because a lot of people who pay $30k+ for a car will pay $120 for a set of flashy spark plugs (and Mitsu probably has an agreement with NGK). Factory parts are always more expensive than they have to be.
Originally posted by ShapeGSX
I have compared the 2 side by side. They have a lot in common.
Differences:
The Evo's block is rotated 180 degrees in the engine bay. In other words, really no casting difference. They just put the engine on the other side of the engine bay.
The Evo's head is mirrored left to right in the engine bay. Definite casting difference here.
The Evo's intake manifold is lower and has shorter runners.
The Evo has a serpentine belt instead of the 3 belts my car has.
The Evo has a coil on plug wasted spark ignition as opposed to the remote coil wasted spark ignition on my car.
The initial thought may be that there is nothing in common by looking at them. But there isn't anything that really makes them operate differently. And operation is the important thing.
On top of this, the engine computers in the 2G Eclipse and the Evo appear to have most of their major functions in common (as is stated in the Evo's Technical Reference Manual).
Frankly, all the stuff that makes any difference when it comes to getting a spark to fire in the combustion chamber is the same or better with the Evo. Copper plugs will work fine.
I'm telling you why they will work fine.
Why don't you tell me why they won't instead of just trying to tell me that they won't?
I have compared the 2 side by side. They have a lot in common.
Differences:
The Evo's block is rotated 180 degrees in the engine bay. In other words, really no casting difference. They just put the engine on the other side of the engine bay.
The Evo's head is mirrored left to right in the engine bay. Definite casting difference here.
The Evo's intake manifold is lower and has shorter runners.
The Evo has a serpentine belt instead of the 3 belts my car has.
The Evo has a coil on plug wasted spark ignition as opposed to the remote coil wasted spark ignition on my car.
The initial thought may be that there is nothing in common by looking at them. But there isn't anything that really makes them operate differently. And operation is the important thing.
On top of this, the engine computers in the 2G Eclipse and the Evo appear to have most of their major functions in common (as is stated in the Evo's Technical Reference Manual).
Frankly, all the stuff that makes any difference when it comes to getting a spark to fire in the combustion chamber is the same or better with the Evo. Copper plugs will work fine.
I'm telling you why they will work fine.
Why don't you tell me why they won't instead of just trying to tell me that they won't?
The highlighted portion of your quote would change the dynamics of the engine enough to warrant looking at different plugs alone... the change in compression ratio difference is a no brainer... then again, I'm used to treating every engine like it is different from every other... because it is.
Hm, okay.. so I got lost in this whole tech talk of gapping etc.
Basically, what are some good plugs to try out?
The NGK Coppers and the stocker Iridums? (any model #'s?)
And how often have people been changing their plugs?
n00b question: how do you tell when it's time to replace the plugs?
Basically, what are some good plugs to try out?
The NGK Coppers and the stocker Iridums? (any model #'s?)
And how often have people been changing their plugs?
n00b question: how do you tell when it's time to replace the plugs?