Spark Plug Gap vs Coil Voltage

[JeremyH]

Before you attribute your gains to plug gap, what was the DA during your trips to the track? A change in DA can easily account for the mph difference, especially in a non-intercooled car.

My vortech is gapped at .028 and put down 475 to the tires. It's been running like a champ for 3 years.

You are wasting your time with him...

 

[BruceH]

Thanks, Bruce! Still trying to run as fast as you and Marc S, but still have a ways to go. It's always good to see progress, though!

You are doing it with 364hp. Quite a difference.

 

[aznjpnboi86]

Man Brian, everytime you tell me about your passes, it makes me want to get the materials to drag (driveshaft loops, jacket, helmet). If you are hitting high 11's with 364 rwhp, I can even imagine what I would get with 420 rwhp/412rwtq. I went back to John and changing the gap bigger gained my another 12-15 rwhp. We will see about maybe next year.....

 

[Marc s]

Before you attribute your gains to plug gap, what was the DA during your trips to the track? A change in DA can easily account for the mph difference, especially in a non-intercooled car.

My vortech is gapped at .028 and put down 475 to the tires. It's been running like a champ for 3 years.

The DA was within 200' between the two days he ran the car.

 

[Five Oh Brian]

You are wasting your time with him...

Dude, what is your problem? I'm working methodically through minor details with my car to find what works best with my combination. What I have learned on the topic of spark plug gap and hotter coils is that my particular combination makes its best power with a wider gap than most of you run as long as I have more voltage to fire the plugs without spark blowout. Why does that bother you so much, Lightblade? You make it sound like if I don't follow your blueprint exactly, then I'm an idiot or not willing to learn. Quite the contrary, I've set my car up by using the overall advice of many people and a little trial and error.

 

[Five Oh Brian]

Man Brian, everytime you tell me about your passes, it makes me want to get the materials to drag (driveshaft loops, jacket, helmet). If you are hitting high 11's with 364 rwhp, I can even imagine what I would get with 420 rwhp/412rwtq. I went back to John and changing the gap bigger gained my another 12-15 rwhp. We will see about maybe next year.....

Jason, it's interesting to hear that your car responded well to more spark plug gap, as well. Is it running smoothly, though? How much gap did you end up with? Seemed like .045" was too much for your car, yet .030" wasn't enough. Did you find a happy medium?

You've gotta join us at the dragstrip sometime next season. It's a lot of fun and you can put all that power to good use.

 

[Five Oh Brian]

Before you attribute your gains to plug gap, what was the DA during your trips to the track? A change in DA can easily account for the mph difference, especially in a non-intercooled car.

My vortech is gapped at .028 and put down 475 to the tires. It's been running like a champ for 3 years.

As Marc S mentioned above, the weather was very similar (within a couple hundred feet of DA). I pull the weather data for every day that I race so that I can factor that in to comparisons between days and even runs done the same day. My best run from yesterday actually came when the DA was at its highest yesterday, ironically.

I have no doubt that your car runs like a champ at .028 gap. My car ran great at .028 for the last few months, as well. Much smoother than it did at .045 with the stock coils. However, even though it ran well, I was giving up power (as evidenced by lower traps speeds with all other variables held equal). Adding aftermarket coils (with more than twice the voltage) made the car trap higher and allowed it to run silky smooth once I gapped the plugs out to .45. The combination worked wonders for drivability and trap speeds).

So, here is a summary of this year's racing data from my timeslips with the only power variables being spark plug gap and coils...​

• .045 gap and stock 20K volt coils. Average trap speeds of 112 to 113 mph.
• .028 gap and stock 20K volt coils. Average trap speeds of 107 to 109 mph. So, with stock coils, just gapping down from .045 to .028 (absolutely no other changes) cost me 4-5 mph through the traps (ouch!).
• .028 gap and GMS 42K volt coils. Average trap speeds of 111 to 112 mph. The GMS coils got back 3-4 mph of the loss from the tighter gap (nice!).
• .045 gap and GMS 42K volt coils. Average trap speeds of 113.5 to 114 mph. Widening the gap netted me another 2 mph roughly.

In summary, I am 100% certain that a .045 gap with aftermarket coils is worth about 20-30 rwhp (maybe more) in my car vs .028 gap with stock coils. Looking at my recap above, we're talking about a 5-6 mph improvement in trap speeds between those 2 scenarios. That's very significant no matter how you disect it. And for those who hate GMS for whatever reason, please note that my car went faster through the traps with the GMS coils regardless of which gap you compare. As always, your results may vary, but I feel the GMS coils were money very well spent ($249).​

 

[aznjpnboi86]

Brian, the car is running absolutely amazing with the 0.045" gap and Accel COP. I gave up a little top end torque but gain top end power. Car starts up great and hasn't had any trouble codes. I think we can call the SCT change from Diablosport a success. There is no lag at any rpm and the car has the instant power I was looking for.

 

[max2000jp]

As Marc S mentioned above, the weather was very similar (within a couple hundred feet of DA). I pull the weather data for every day that I race so that I can factor that in to comparisons between days and even runs done the same day. My best run from yesterday actually came when the DA was at its highest yesterday, ironically.

I have no doubt that your car runs like a champ at .028 gap. My car ran great at .028 for the last few months, as well. Much smoother than it did at .045 with the stock coils. However, even though it ran well, I was giving up power (as evidenced by lower traps speeds with all other variables held equal). Adding aftermarket coils (with more than twice the voltage) made the car trap higher and allowed it to run silky smooth once I gapped the plugs out to .45. The combination worked wonders for drivability and trap speeds).​

So, here is a summary of this year's racing data from my timeslips with the only power variables being spark plug gap and coils...​

• .045 gap and stock 20K volt coils. Average trap speeds of 112 to 113 mph.
• .028 gap and stock 20K volt coils. Average trap speeds of 107 to 109 mph. So, with stock coils, just gapping down from .045 to .028 (absolutely no other changes) cost me 4-5 mph through the traps (ouch!).
• .028 gap and GMS 42K volt coils. Average trap speeds of 111 to 112 mph. The GMS coils got back 3-4 mph of the loss from the tighter gap (nice!).
• .045 gap and GMS 42K volt coils. Average trap speeds of 113.5 to 114 mph. Widening the gap netted me another 2 mph roughly.

In summary, I am 100% certain that a .045 gap with aftermarket coils is worth about 20-30 rwhp (maybe more) in my car vs .028 gap with stock coils. Looking at my recap above, we're talking about a 5-6 mph improvement in trap speeds between those 2 scenarios. That's very significant no matter how you disect it. And for those who hate GMS for whatever reason, please note that my car went faster through the traps with the GMS coils regardless of which gap you compare. As always, your results may vary, but I feel the GMS coils were money very well spent ($249).​

Did you datalog timing? What was your IAT at the start and finish of the runs? The knock sensors on these cars are very sensitive. I just have a hard time believing spark gap was your issue. Also, like Jim stated above the stock coils are more than effective at your power level.

 

[JeremyH]

Dude, what is your problem? I'm working methodically through minor details with my car to find what works best with my combination. What I have learned on the topic of spark plug gap and hotter coils is that my particular combination makes its best power with a wider gap than most of you run as long as I have more voltage to fire the plugs without spark blowout. Why does that bother you so much, Lightblade? You make it sound like if I don't follow your blueprint exactly, then I'm an idiot or not willing to learn. Quite the contrary, I've set my car up by using the overall advice of many people and a little trial and error.

The comment was due to the fact that he is wasting his time with that advice because yout are going to do whatever you want to your car. So instead of seeing every voice of reason make a comment and you saying i have aftermarket cops and I ran 2mph quicker, i made the comment.

Everybody knows wider gap and more spark energy energy will yield better combustion and a little more power, doesnt mean its the right thing to do on your setup. You really are playing with fire (pun intended lol)Just beacuse you dont have "spark blowout" doesnt mean everythings safe.

Your running too wide of a gap on hot non-cooled boost..., you think becauase you have aftermarket coils that everything is good and they are helping. The gms coils arent doing a damn thing, your actually getting away with the little bit wider gap due to running one heat range colder plugs. Is this good for the car? probably not, could it cause the plugs to go quicker or increase the risk on detonation, very much so. But hey man its your car, you dont care so no one else should, your not an idiot, never said that, you just seem a little distracted by those holy track times right now. Wont even get into the fact that the weathers cooler, as there are many factors here, and thats alll he said she said anyway.

My final point is you are playing with gap and spark like its a race car and your trying to squeeze every inch of power out of it regardless if its safe or reliable, its a street car that you are running some pretty nice times with, I would hate to see you mess it up because or something stupid like this. Do your thing man, and good luck! I will continue to be the voice of reason even though I know you dont want to hear it lol

 

[JeremyH]

As Marc S mentioned above, the weather was very similar (within a couple hundred feet of DA). I pull the weather data for every day that I race so that I can factor that in to comparisons between days and even runs done the same day. My best run from yesterday actually came when the DA was at its highest yesterday, ironically.

I have no doubt that your car runs like a champ at .028 gap. My car ran great at .028 for the last few months, as well. Much smoother than it did at .045 with the stock coils. However, even though it ran well, I was giving up power (as evidenced by lower traps speeds with all other variables held equal). Adding aftermarket coils (with more than twice the voltage) made the car trap higher and allowed it to run silky smooth once I gapped the plugs out to .45. The combination worked wonders for drivability and trap speeds).​

So, here is a summary of this year's racing data from my timeslips with the only power variables being spark plug gap and coils...​

• .045 gap and stock 20K volt coils. Average trap speeds of 112 to 113 mph.
• .028 gap and stock 20K volt coils. Average trap speeds of 107 to 109 mph. So, with stock coils, just gapping down from .045 to .028 (absolutely no other changes) cost me 4-5 mph through the traps (ouch!).
• .028 gap and GMS 42K volt coils. Average trap speeds of 111 to 112 mph. The GMS coils got back 3-4 mph of the loss from the tighter gap (nice!).
• .045 gap and GMS 42K volt coils. Average trap speeds of 113.5 to 114 mph. Widening the gap netted me another 2 mph roughly.

In summary, I am 100% certain that a .045 gap with aftermarket coils is worth about 20-30 rwhp (maybe more) in my car vs .028 gap with stock coils. Looking at my recap above, we're talking about a 5-6 mph improvement in trap speeds between those 2 scenarios. That's very significant no matter how you disect it. And for those who hate GMS for whatever reason, please note that my car went faster through the traps with the GMS coils regardless of which gap you compare. As always, your results may vary, but I feel the GMS coils were money very well spent ($249).​

I am not impressed.

 

[Five Oh Brian]

Brian, the car is running absolutely amazing with the 0.045" gap and Accel COP. I gave up a little top end torque but gain top end power. Car starts up great and hasn't had any trouble codes. I think we can call the SCT change from Diablosport a success. There is no lag at any rpm and the car has the instant power I was looking for.

Outstanding, Jason! It's taken awhile to get it right in your car, but it sounds like it's all worked out for the best now. You might just start driving your GT/CS everyday now, huh?

 

[Five Oh Brian]

Did you datalog timing? What was your IAT at the start and finish of the runs? The knock sensors on these cars are very sensitive. I just have a hard time believing spark gap was your issue. Also, like Jim stated above the stock coils are more than effective at your power level.

I did not datalog and I don't know what my IAT's were - sorry. My timing is very conservative, though, at just 14 degrees. At .045 spark plug gap and stock coils, I had misfire/blowout. Gapping down to .028 cured that, but also cost me power. With aftermarket coils, the .045 spark plug gap runs great. All the power is back and absolutely zero misfire/blowout. So, regardless of what Jim (or anyone else) says, my car obviously needed more voltage at .045 gap than the stock coils could provided.

 

[Five Oh Brian]

I should add one more variable from this past weekend's drag results. I ran my personal best ET's and trap speeds at a race weight that was actually 80 lbs more than usual. I normally take my passenger seat, rear seat, and trunk liner out, but left them all in this time and still managed to run faster. That 80 lbs likely cost me nearly a tenth in ET and at least 1/2 mph through the traps. I know; coulda, should, woulda, but worth noting none-the-less.

 

[JeremyH]

Congrats man those are great times, good luck!

 

[Five Oh Brian]

Lightblade, I know you think I'm driving a ticking timebomb. Keep in mind that I drove the car very hard for two years with dozens and dozens of passes down the 1/4 mile with a .045 spark plug gap (FRPP 3V0 spark plugs). I put up with the misfire/blowout for those 2 years. I suspect that was much harder on the car than running the same .045 gap now with hotter coils that prevents the misfire/blowout.

On a side note, I've been pondering water-methanol injection for quite awhile, and think I'll go that route this winter so that I can run a little more timing. The cooling and effective octane boost should allow for a safer running car while yielding worthwhile power gains. Our local tuner swears by water-meth and has used it on his own race cars extensively so he has a ton of experience tuning for it.

Ultimately, I want the car to run 11.50's and 11.60's consistently. I don't want to have to add a rollcage to the car (NHRA required at 11.49 and quicker), so I'm done modding after the water-meth goes in.

 

[Five Oh Brian]

Congrats man those are great times, good luck!

Thanks, man. We're all here to have some fun and get the most out of our cars.

 

[JeremyH]

Swearing by water/meth is an oxymoron as well lol, its impossible to call it 100% reliable or effective, plus you will get different temps in each cyclinder, just the nature of sprayin before the tb. Will it help to run a little more timing, yes. is it optimal/relaible, no, those are just the facts. why are you so against an intercooler?
(intercooler can be done for same price of a meth kit by the way and is 100% consistent and reliable, safer, the list goes on lol)

I know you have seen this thread. see post 17
http://www.s197forum.com/forum/showthread.php?t=36238

he ended up making an intercooler setup with my help for cheaper than it cost me ($300) and dropped a full second off his et.

And i know you have seen that thread as well lol
http://www.s197forum.com/forum/showthread.php?t=39925


If you were to do meth i would go with An AIS kit hands down.

 

[aznjpnboi86]

Lightblade, you are entitled to your opinion. When it comes to having a reliable car, I think both Brian and I would not have put superchargers on to begin with. Our tuner, John, has a strong reputation of tuning our cars and allows us to run safe without pushing the envelope. If our cars break, it gives us motivation to build up a new motor.

 

[Five Oh Brian]

If you were to do meth i would go with An AIS kit hands down.

I do prefer the AIS kit over the Snow kit from all I've read. Really like their trunk mounted reservoir and stainless lines. I suspect that's the kit I'll opt for. Or, I may just tap the windshield wiper tank and leave the trunk alone (I golf and need room in the trunk for my clubs).