Pulled spark plugs, does it appear the car is running lean? And paxton question.

Discussion in 'SRT10 and SRT10 Coupe Discussions' started by KDR83, Apr 28, 2012.

  1. KDR83

    KDR83 Enthusiast

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    I just bought my car about a month ago, the previous owner's mechanic put in the wrong spark plugs for a forced induction car so I put in some NGK 4291s gapped to .032. The plugs I pulled out have less then 2500 miles on them. I drove the car down from Indianapolis to Miami and went from Miami to Tampa and back once. I noticed a hesitation at higher RPMs thinking it might have been the spark plugs. I attached some pictures of the plugs, do these look like I am running lean?

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    Since I am bought someone elses modded car, I want to make sure everything is running right. I also noticed that I could not hear the intercooler pump turning on and the intercooler radiator is cool to the touch right after driving for 30 min so I need to diagnose if it's the relay or the pump itself. Anyone heard of these failing before?
     
  2. Greg Good Cylinder Heads

    Greg Good Cylinder Heads Enthusiast

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    It's hard to tell because the plugs have a lot of normal driving and idling on them.

    Plugs like that that have a super long side electrode are only good for stock engines. On a blower engine that long side electrode will glow red hot, it doesn't matter how cool the heat range of the plug is. The electrode is too long to transfer heat into the body of the plug.

    The 4921 plug is a 6 heat range. Too hot IMO for a power adder car. A better plug (IMO) would be the 4644, which is a 7 heat range (one step colder than what you have). If you're going to a standing mile race or something like that put in a 7173, it is an 8 heat range.


    4644 plug image. Notice how the side electrode is shorter. This is considered a typical extended tip plug.

    ngk-4644_w.jpg
     
  3. Steve-Indy

    Steve-Indy VCA Member - Great Lakes

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    I feel a little history MAY be helpful here.



    After finding this thread, and reading the statement: "the previous owner's mechanic put in the wrong spark plugs for a forced induction car" I thought that I would do a little checking since I know ALL of the folks involved.

    Originally, the 2nd owner of this car purchased it used with very low mileage from Woodhouse and was quite happy. Then, he decided to send it back to Woodhouse for some modifications...including a "safe, dependable" Paxton installation...WITHOUT "building" the motor around the system. Said owner (with whom I spoke this AM) remembers speaking specifically with Mark concerning use of the stock Champion RC 12 ECC plugs that Mark recommended be used in THIS PARTICULAR application. The time frame here was in the 2006-7 era (by
    2nd owner's memory, without pulling records).
    Said owner also noted that the PCM was reflashed at DC Performance by Dan who knew the specific application AND the fact that the stock plugs were being used.

    The 2nd owner had NO troubles as reported by the present owner...AND states that he never changed the stock plugs after the Paxton was installed.

    Owner number 3 also reports NO drive-abltity issues whatsoever (long time rally driver, SCCA formula driver, etc)...AND, had not changed the plugs before the inspection by a Viper Tech during the requested pre-sale compression check. The Tech actually suggested doing this since the plugs were already out ("no good deed goes unpunished"). Thus the RC 12 ECC plugs found by the current owner were merely replacements of the Woodhouse plugs placed at the time of the Paxton installation.

    The time frame noted above is important since MUCH MORE info and understanding of these systems has occurred as more and more Paxtons were installed the Gen III cars around the country...especially at Woodhouse and DC Performance. In over 7-8 years of Paxtons being placed on Gen III's, MUCH has indeed been learned concerning these systems and the various power levels/ applications that the owner wants and plans to use. Based on this accumulated experience, there may be other choices of plugs to be considered.


    A search using the words Paxton plugs (do NOT use quotes or parentheses ) will net many folks who have used "the stock plugs" in Gen III Vipers equipped with various forms of Paxton kits...seemingly all in the lower Horsepower range as I see it (less than 700 HP @ the rear
    wheels.

    This thread based upon the search above words will shed more light:

    http://forums.viperclub.org/search.php?searchid=510293http://forums.viperclub.org/search.php?searchid=510293

    It seems to me that the main issue here is prompt and correct diagnosis of the original problem described by KDR83...best accomplished by an experienced shop followed by the appropriate fix (Doug Levin comes to mind !!)

    I HOPE that this helps!!
     
  4. Greg Good Cylinder Heads

    Greg Good Cylinder Heads Enthusiast

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    I don't consider a Paxton Viper with a rwhp number approaching 700 a "low horsepower" car. If you factor in the power that the Paxton absorbs you're closer to 800 rwhp. That's not all that far from double the factory hp. Where does the extra power come from? Burning a lot more fuel, ergo more btu's of heat being released in the combustion chamber which the spark plug is directly exposed to. That changes the heat range requirements.

    We don't know that here is a problem with his tune being lean. He really needs to put a wideband O2 on the car to monitor his afr. Chris from DC mentioned the other day that he was recommending that his customers install the AEM fail safe wideband monitor on their cars.

    It's impossible to tell from the picture of his plug on a computer screen if he's slightly lean. That heat range plug, and projected as far as it is into the chamber, will just about always have a white tip on it unless the tune is way out in the weeds. He would have to put fresh plugs in, make two passes (one pass isn't normally enough to color a plug), cut it clean after each pass with no idling or low speed running, and then pull and inspect.

    I'm not saying that the tuners running stock plugs are doing it wrong, I'm just saying it's taking a risk *in my humble opinion*. A plug only needs to be hot enough to not foul at idle and cruising speeds. Any hotter, and there's a risk of pre-ignition at wide open throttle.

    i would like to see Doug chime in as well. I don't know what plug he has put in every single build, but I do know that a -8 NGK is one of his *favorites* for a street driven Paxton car. And that is a fact ;-)
     
    Last edited: Apr 29, 2012
  5. Steve-Indy

    Steve-Indy VCA Member - Great Lakes

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    Thanks, Greg...your opinions mean tons!! My goal is to encourage proper, professional, disciplined diagnosis of the "issue"...NOT just throwing easily installed parts at a perceived problem in a random fashion.

    As you might guess...I really have no personal experience and very little knowledge about such mods !! :)
     
  6. Greg Good Cylinder Heads

    Greg Good Cylinder Heads Enthusiast

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    I understand your point completely. It's not fair to accuse someone of doing something *wrong* if it is just a matter of a difference in opinion. I hope that I didn't come across that way.

    There seem to be two ways of looking at plug choice in the industry. One is to have the plug just cold enough to not cause pre-ignition. The other school of thought is to have the plug just hot enough to not foul. The two cover about 3 heat ranges, and several different tip lengths.

    I definitely think the 4921 plug that the op put in is too hot for a blower car. That's the main reason I posted in this thread. I don't want to see him break a ring land on a piston from pre-ignition. it doesn't take much to break a cast piston.
     
    Last edited: Apr 29, 2012
  7. KDR83

    KDR83 Enthusiast

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    Steve,

    Definitely did not mean anything bad by saying the wrong plugs were put in. Just after searching the forums it appeared there was a particular plug that was recommended and it appeared the vast majority of people recommend a colder plug then the stock heat range. I figured I would try this first since it was the most cost effective option and not to mention I wanted to put a plug in that gets often times recommended for a viper setup with a Paxton. I honestly don't want nor need any more horsepower out of this car but just want to do everything to make sure its running in tip top shape. I sent the pics of the plugs to Sean Roe and he said the car does appear to be running lean per the plugs and also recommended Doug Levin so I will give him a call. It also appears the pump for the intercooler is not turning on so hopefully we can diagnose both problems at once. The car may need a retune, it has been a while since it was tuned. Not putting any blame on anyone, just trying to get my car 100% so I can continue enjoying it for years to come :)

    Steve, it would be great if you could put me in touch with the owner that did all of the modifications, I would love to talk to him and just get some background on the car.

    Thanks,
    Krystian
     
  8. Steve-Indy

    Steve-Indy VCA Member - Great Lakes

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    Understand, Krystain...agree that you need to sort things...just hoping that well ment interventions don't muddy the waters, and cost more in the long run.

    I will pass along your request via e-mail...noting he does read and post regularly here.

    P. S. You should have seen just how fast your beast left our 08 in a rolling, 3rd gear pull from about 60 mph...Mr. "" left me so fast that I thought that I was going backwards...on a closed course, of course.
     
  9. 98intrigue

    98intrigue Viper Owner

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    Hearing this... I really want a ride, Krystian. It will be good for the adrenaline rush... but maybe bad for the pocket. Ha
     

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