Denso Iridium Plug Issues......
Denso Iridium Plug Issues......
I've got around 5500 miles on my Evo. It is stock except for the removal of the air box and the addition of a filter on the end of the mass air meter. The plugs are stock with 5500 miles on it as well. The car has a little cold stumble when first started up in the morning. It is as if it needs a little warm up at idle before driving it to get to operating temp.
The car ran good with the stock plugs. It's done consistent 13.2's in the heat of the day at 102mph and even 13.1's in the cool night.
About 3 days ago I decided to try the Denso Iridium IW24's. 1 step colder than stock. The main reason for this was to try to cure the cold start stumble that my car has and ofcourse to maybe pick up a couple HP.
After installation of the Denso IW24's Initial start up was nice with a slightly smoother idle. The cold start up stumble is still there, put not nearly as much and in only takes a about 20-30 seconds for the car to warm up and feel normal as opposed to 1-2 minutes with the stock plugs. I did not change the gapping on the plugs.
The problem that concerns me is, the car feel much smoother and the SOTP (seat of the pants) dyno say the car is quicker on daily driving around town with 75% or less throttle input. At 100% throttle, the car doesn't feel as quick. It does not pull as smooth and it feels okay until about 4800-5500 rpms when there is a dip in the power delivery. Almost as if the car is pulling then reaches that RPM and dip down for a sec then starts pulling again. Very odd.
I took the car to the local 1/4 mile the other night and couldn't get better than a 13.3 at 100 mph with the addition of NOS sprayed on the intercooler. I never had to do this before to get the 13.1's-13.2's.
Note: I did not reset the ECU either.
If anyone has experience with this or knows the reason/fix for it, please let me know. This really sucks that I paid $52 for plugs that should be better than stock, but only slowed my car down.
Could it be running too rich? Maybe too lean?
For now I'll be going back to stock plugs.
The car ran good with the stock plugs. It's done consistent 13.2's in the heat of the day at 102mph and even 13.1's in the cool night.
About 3 days ago I decided to try the Denso Iridium IW24's. 1 step colder than stock. The main reason for this was to try to cure the cold start stumble that my car has and ofcourse to maybe pick up a couple HP.
After installation of the Denso IW24's Initial start up was nice with a slightly smoother idle. The cold start up stumble is still there, put not nearly as much and in only takes a about 20-30 seconds for the car to warm up and feel normal as opposed to 1-2 minutes with the stock plugs. I did not change the gapping on the plugs.
The problem that concerns me is, the car feel much smoother and the SOTP (seat of the pants) dyno say the car is quicker on daily driving around town with 75% or less throttle input. At 100% throttle, the car doesn't feel as quick. It does not pull as smooth and it feels okay until about 4800-5500 rpms when there is a dip in the power delivery. Almost as if the car is pulling then reaches that RPM and dip down for a sec then starts pulling again. Very odd.
I took the car to the local 1/4 mile the other night and couldn't get better than a 13.3 at 100 mph with the addition of NOS sprayed on the intercooler. I never had to do this before to get the 13.1's-13.2's.
Note: I did not reset the ECU either.
If anyone has experience with this or knows the reason/fix for it, please let me know. This really sucks that I paid $52 for plugs that should be better than stock, but only slowed my car down.
Could it be running too rich? Maybe too lean?
For now I'll be going back to stock plugs.
Is the air intake your only mod? If so your car is basically stock and moving to a colder plug wont help. I would stay with the factory heat range (7) unless you have at least 300hp or above. The plugs you have might be too cold for you application.
Id agree, The stock heat range should be fine for you especially becuase you are so rich stock. Colder plugs are not going to perform well at the 5000-5500 up to 8 grand because that is when the stock car runs about 9.5/1 afr stock. Buy denso but use the stock heat range, this should cure both problems so you get the best of both worlds. The cold stumble that feels like and very small miss is normal for the 4g63 engine on cold starts due to several changing veribles but it shouldn't be overly bad it sounds like you know the correct feel.
I have the same "Dip" in power, the plugs are OK to run, the cooler heat range isn't going to hurt anything. The post above mine is correct about the "Cold stumble" its actually because when the engine is cold (for 30-120 seconds) it runs in OPEN LOOP, which is sort of like engaging the choke on an older car, it will stumble when its cold. This will happen on almost any car, but the 4g63 its pretty normals.
Ok.. with that said, the "dip" in power at 4800-5000 is likely the result of your open element filter. I've had one for some time on my car, there is some level of turbulence that these filters cause which affect the MAF reading, specifically at that RPM, and is likely the reason you feel it. Its a well known anomoly of these types of filters and the reason why many do not recommend using them.
Before swapping your plugs out for the stock heat range (which is also a good idea because your car is stock, but its not necessary) you can adjust the gap size to .026 (denso's should already be gapped at that, but you can run gaps from .025-.030)
Try putting your stock airbox back in (if you can) Its likely your percieved Dip will go away.
Ok.. with that said, the "dip" in power at 4800-5000 is likely the result of your open element filter. I've had one for some time on my car, there is some level of turbulence that these filters cause which affect the MAF reading, specifically at that RPM, and is likely the reason you feel it. Its a well known anomoly of these types of filters and the reason why many do not recommend using them.
Before swapping your plugs out for the stock heat range (which is also a good idea because your car is stock, but its not necessary) you can adjust the gap size to .026 (denso's should already be gapped at that, but you can run gaps from .025-.030)
Try putting your stock airbox back in (if you can) Its likely your percieved Dip will go away.
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Joined: Jun 2003
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From: Nothern CA
I used to tweak around with surface gaps and cap discharge ignition set ups, the results were all over the place. You might try some different fuel (I get the best results with "Union 76" 98 octane) and an ecu reset with your original plugs. Your car is so fast for being essentialy stock, I can't help but think you are running lean for some reason. A lean condition might also explain why you have stumbling when it is cold.
Last edited by WildRice; May 9, 2004 at 08:43 AM.
It probably is running a bit lean.. In fact, my car from the factory Bone stock ran a 12.93 in the 1/4.. the aftermarket filter alters the MAF readings that can also cause the car to run more lean at some point in the RPM Range, and the MAF reading "Hops around" due to turbulence at other RPM's (4500-5000 or so) which can make the car feel like the power dips at that RPM range.
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Originally Posted by MalibuJack
I have the same "Dip" in power, the plugs are OK to run, the cooler heat range isn't going to hurt anything. The post above mine is correct about the "Cold stumble" its actually because when the engine is cold (for 30-120 seconds) it runs in OPEN LOOP, which is sort of like engaging the choke on an older car, it will stumble when its cold. This will happen on almost any car, but the 4g63 its pretty normals.
Ok.. with that said, the "dip" in power at 4800-5000 is likely the result of your open element filter. I've had one for some time on my car, there is some level of turbulence that these filters cause which affect the MAF reading, specifically at that RPM, and is likely the reason you feel it. Its a well known anomoly of these types of filters and the reason why many do not recommend using them.
Before swapping your plugs out for the stock heat range (which is also a good idea because your car is stock, but its not necessary) you can adjust the gap size to .026 (denso's should already be gapped at that, but you can run gaps from .025-.030)
Try putting your stock airbox back in (if you can) Its likely your percieved Dip will go away.
Ok.. with that said, the "dip" in power at 4800-5000 is likely the result of your open element filter. I've had one for some time on my car, there is some level of turbulence that these filters cause which affect the MAF reading, specifically at that RPM, and is likely the reason you feel it. Its a well known anomoly of these types of filters and the reason why many do not recommend using them.
Before swapping your plugs out for the stock heat range (which is also a good idea because your car is stock, but its not necessary) you can adjust the gap size to .026 (denso's should already be gapped at that, but you can run gaps from .025-.030)
Try putting your stock airbox back in (if you can) Its likely your percieved Dip will go away.
MalibuJack, Good advice as usual!
1. Check the gaps. Stock is 0.7mm
2. Reset the ECU and allow the car to idle for 15mins after.
3. Refit the airbox or at least the airguide!
I appreciate the help guys!!! 
You all provided me with some good info.
I took the Denso IW24's out today and replaced them with the stock NGK's. The Denso's are a very dark black on the ends, especially for only having them a few days. The Denso iridium tips were clean and free from carbon.
The stock NGK's have a nice light brown burn with very little to no carbon build up.
The car feel like normal with no dip at high RPM's.
Btw, the dip was never noticable with the stock plugs.
What do you guys think about running an S-AFC2 with the Denso IW24's? I was thinking that I could use the advantge of the Denso IW24's with the S-AFC2 and lean it out were needed. I figured the S-AFC2, Denso's and a Dyno should be worth about 20-25whp.
Anyone wanna chime in?
Thanks again!
-Tony
You all provided me with some good info.I took the Denso IW24's out today and replaced them with the stock NGK's. The Denso's are a very dark black on the ends, especially for only having them a few days. The Denso iridium tips were clean and free from carbon.
The stock NGK's have a nice light brown burn with very little to no carbon build up.
The car feel like normal with no dip at high RPM's.
Btw, the dip was never noticable with the stock plugs.
What do you guys think about running an S-AFC2 with the Denso IW24's? I was thinking that I could use the advantge of the Denso IW24's with the S-AFC2 and lean it out were needed. I figured the S-AFC2, Denso's and a Dyno should be worth about 20-25whp.
Anyone wanna chime in?
Thanks again!
-Tony
DR.,
I think I know what you are trying to do. But I think if it were likely to succeed mitsu would have done it. Trouble is the knock. If your thinking were correct you should be able to use an even more radical plug and tune even more agressively?
As you know mitsu dumps fuel to kwell knock, if as the posters above thought you are a bit lean already your ecu will be trying to dump fuel and retard timing to keep the knocks down. I wish I knew more about your S-AFC2. Does it allow fuel to come back if it sees knock?
I love reading plugs, and am amazed that the evo doesn't foul them right off the bat. They must have a very hot spark and a really well designed chamber. So everything I know about reading plugs seems to mean nothing with this car. If you have a light brown plug and it works well - stick with it.
Back to your tuning, as I see it the only way around the richness issue with the evo is to use water injection. Think of it as if you were running 100 octane fuel. You can dial in a good afr and timing. This is the route I am going to use. But then I am pretty certain my car Does run rich. After a track day it is dusted with soot. Once I have the WI and a piggy back hooked up I will have it tuned to where it should be. With the safegaurds in my wi and the piggy back I am comfortable I'm not going to buy a new engine.
Without the wi I don't think there is a lot of fuel you can lose especialy if you are already running on the lean side.
All that said I will be as interested as you to know how better informed tuners think.
good luck.
I think I know what you are trying to do. But I think if it were likely to succeed mitsu would have done it. Trouble is the knock. If your thinking were correct you should be able to use an even more radical plug and tune even more agressively?
As you know mitsu dumps fuel to kwell knock, if as the posters above thought you are a bit lean already your ecu will be trying to dump fuel and retard timing to keep the knocks down. I wish I knew more about your S-AFC2. Does it allow fuel to come back if it sees knock?
I love reading plugs, and am amazed that the evo doesn't foul them right off the bat. They must have a very hot spark and a really well designed chamber. So everything I know about reading plugs seems to mean nothing with this car. If you have a light brown plug and it works well - stick with it.
Back to your tuning, as I see it the only way around the richness issue with the evo is to use water injection. Think of it as if you were running 100 octane fuel. You can dial in a good afr and timing. This is the route I am going to use. But then I am pretty certain my car Does run rich. After a track day it is dusted with soot. Once I have the WI and a piggy back hooked up I will have it tuned to where it should be. With the safegaurds in my wi and the piggy back I am comfortable I'm not going to buy a new engine.
Without the wi I don't think there is a lot of fuel you can lose especialy if you are already running on the lean side.
All that said I will be as interested as you to know how better informed tuners think.
good luck.
It's not exactly what I'm trying to do, but close. I want to use the S-AFC to tune my car, but also have the Denso's for safety and the lil' extra HP. I actually want a conservative tune with a decent gain in HP.
Here's a link to the APEXi S-AFC 2. http://www.apexi-usa.com/electronics_safc.asp There's some useful info on the APEXi unit. It's a cheap alternative to laptop tuning, especially if you are basically stock.
As for my car, I went back to stock plugs and the car runs fine. I plan on buying the S-AFC 2 and then doing a baseline dyno w/ A/F and then I'll install the Denso's and with another dyno for comparison purposes. Finally, I'll run the S-AFC 2 w/ Denso's and some tuning.
I'll post results when I'm done.
I actually want a conservative tune with a decent gain in HP.Here's a link to the APEXi S-AFC 2. http://www.apexi-usa.com/electronics_safc.asp There's some useful info on the APEXi unit. It's a cheap alternative to laptop tuning, especially if you are basically stock.
As for my car, I went back to stock plugs and the car runs fine. I plan on buying the S-AFC 2 and then doing a baseline dyno w/ A/F and then I'll install the Denso's and with another dyno for comparison purposes. Finally, I'll run the S-AFC 2 w/ Denso's and some tuning.
I'll post results when I'm done.
