Spark Plug Gap vs Coil Voltage

[JeremyH]

And to the op, my last bit of advice is you have been luckly so far running non-cooled boost and stock .045 gap. You may have run better times but you were definetly adding heat and uneeded wear and tear.

The plug choice and Gap are for driveability/tuneability and safety. I think trying to run a wider gap and try to increase spark energy on that setup is asking for trouble. If you want the car to run faster you should look elsewhere.

-My advice, run the proper gap (.032 for your setup) get the next size smaller pulley out of the classifieds for cheap and build an intercooler setup, can be done for 200-300$ easily.

This will allow you to safely run more timing from the much cooler iats at the same boost level. It will put you in the 400-425 rwhp range and knock .3-.5 tenths of your et. And did i mention its gonna be alot more reliable and safer! My 2 cents lol

 

[VTXFrank]

I don't think the OP is listening. It's going to take a blown engine before he figures out what we've been trying to tell him.

BTW OP, just in case you don't understand, when the coil manufacturer told you their coils can support .038, they mean not to go over that gap. .045 is definitely over what they recommend as a maximum gap.

 

[Five Oh Brian]

I don't think the OP is listening. It's going to take a blown engine before he figures out what we've been trying to tell him.

BTW OP, just in case you don't understand, when the coil manufacturer told you their coils can support .038, they mean not to go over that gap. .045 is definitely over what they recommend as a maximum gap.

I'm listening and trying to learn. Although, everyone has a different answer, so I'm left to use trial & error to get my answer. The coil manufacturer told me their coil can easily support at least .038, not a max of .038, for my setup.

As much as I'd like to add an intercooler to my setup, that is just plain not in the budget anytime soon. I know that would be ideal, but I can't do it now, so let's take that out of the equation. I'm running a very conservative 14 degrees of timing and a safe 11.6:1 A/F ratio at WOT.

I did not purchase aftermarket coils to add power. I bought them to cure spark blowout while running a wider spark plug gap (which some of you have said will net a more efficient combustion). The trick here is finding a big enough spark plug gap for the most efficient combustion while simultaneously not going so big to cause damage (via too much heat, detonation, or melted electrodes).

Again, I'll have to try a variety of spark plug gaps with the aftermarket coils to see what yields the best results for my setup. .028 cost me power. .045 is likely too big, so I'll try several steps in between until I dial in the right gap for my car.

Keep the feedback coming and I'll post my results after I try each gap. I'm truly trying to learn here.

 

[aznjpnboi86]

Brian,
John out at Horsepower Ranch said to gap them around 0.035 to 0.038. He said that 0.032" gap is only needed for 15psi+ in his book. I am going with my set-up back out to 0.040" since Edelbrock said my kit requires factory gapping which is 0.050".

 

[Five Oh Brian]

Brian,
John out at Horsepower Ranch said to gap them around 0.035 to 0.038. He said that 0.032" gap is only needed for 15psi+ in his book. I am going with my set-up back out to 0.040" since Edelbrock said my kit requires factory gapping which is 0.050".

Is this Jason with the blue '07 GT/CS? If Edelbrock feels that .050 is fine for your E-force blower, then I feel better running .045 this weekend at the track. The I'll have John dyno my car sometime this month at .045, as well. I'll gap down to .038 and compare results vs the .028 and .045 (both at the track and dyno) to get an answer as to what works best with my blower.

 

[Five Oh Brian]

Maybe some history on my car's progress will help....


I ran the supercharger for two years with FRPP 3V0 spark plugs (copper and one heat range colder) at .045 gap with stock coils. Dozens and dozens of passes at our local dragstrips and daily driven VERY hard with lots of WOT and redline.

Here is a summary of this year's racing data from my timeslips. The tighter gap hurt me more than I thought (glad I kept all the timeslips)...

• .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!).

Now I'm curious to see if adding back the wider gap will get me back the 4-5 mph I initially lost on top of the gains from the GMS coils. Not likely to see that much gain, but we'll know for sure this weekend after I hit the track again.

 

[Marc s]

I tend to run smaller gaps than needed due to my experience running my blown alcohol altered. I know, not apples and apples. However, the principles are the same. On my blown alcohol car I have run 24-30lbs of boost and a plug gap of .020 for years and never burned a piston. Last year I decided to experiment with plug gap to see if I could pick up power. Made test passes widening the gap .005 each pass. The car picked up power and did not show any higher EGT's. I got the gap to .035 and made my best pass of 6.67 @ 212. Came back, opened the gap to .040 and put holes through 3 pistons at 1/2 track. Everytime you widen the gap, it's like turning up the amps on your plasma cutter.

 

[bmaxwell]

The hp gain claims are bullshit, they may show a few hp which is most likely do to having failing stock cops. Just like putting in new spark plugs it can show hp on the dyno, but its just becasue the old ones are well old.

Damn I'm glad you said that they were doing a damn good job of advertising haha I was about to pull the trigger on buying them! So how do you know when your stock coils are going bad?? The car starts to run like garbage I would assume? I have been wondering why my car sorta bogs down and sputters a bit when it is cold but it will even do it pretty much until it is completely warm then i dont have a problem with it the rest of the day even if it cools pretty much all the way back down... I have to baby it like an old ass granny until it warms up. Not too big a deal just caused me to be slow pulling out in an intersection almost getting Tboned a few times lol

 

[Five Oh Brian]

I tend to run smaller gaps than needed due to my experience running my blown alcohol altered. I know, not apples and apples. However, the principles are the same. On my blown alcohol car I have run 24-30lbs of boost and a plug gap of .020 for years and never burned a piston. Last year I decided to experiment with plug gap to see if I could pick up power. Made test passes widening the gap .005 each pass. The car picked up power and did not show any higher EGT's. I got the gap to .035 and made my best pass of 6.67 @ 212. Came back, opened the gap to .040 and put holes through 3 pistons at 1/2 track. Everytime you widen the gap, it's like turning up the amps on your plasma cutter.

See, now that's the kind of info I'm looking for. Real empirical #'s and results. Thanks, Marc!

I just spoke with our service manager (at the Ford dealership I work at). He used to be our SVT Director in service, he owned/raced a 10-second Fox body Mustang, and owned/raced a pullied '03 SVT Cobra making nearly 20 psi boost. He's worked on plenty of modded supercharged cars (i.e. Ford GT's, Lightnings, GT500's, Terminators, etc.) I asked him about gapping and he said under .030 for big boost. I asked what would allow a bigger gap with a mild blower (like mine) and he said hotter coils. I explained that was the route I went and he feels that with hotter coils, that .045 is probably fine (or at least a good starting place to experiment with different gaps).

I certainly don't want to destroy anything; simply looking for that sweet spot for gap that is safe. My Vortech is only making 10 psi boost and I ran a .045 gap for 2 years without incident, so I'm thinking that is a safe gap for my particular combination. But, I still want to try a variety of gaps to see what my car likes best.

Arghh. Why can't there just be a simple, straightforward right answer?!?!

 

[Marc s]

My parts failure is not likely to happen with your car Brian. I run 12 to 1 compression, 34 degrees of timing, 30lbs of boost, a magneto which has more spark duration, and a lot of fuel volume and cylinder pressure. That being said, the physics are the same of what's going on in the combustion chamber. I think you will have spark loss before damage from increased cylinder temps and detonation. I don't think that aftermarket coils alone can create enough spark energy to create an issue. If the coils were significantly more efficient over the stock ones, I believe that increasing the spark gap with aftermarket coils would also create a lean condition, which they don't. The reason is, the engine needs X amount of spark energy to create combustion. And increasing that energy does nothing to improve combustion effinciency.

I first experienced this back in the early 80's when I raced my Stage 1 Buick. The car had an 11.5 to 1 455 and ran 12 flat. I had been trying everything to get the car in the 11's. I still had the factory single point re-curved distributor in it with the OEM coil. Friends at the track bugged me non stop to put a MSD distributor in it with a 6AL and MSD coil. My Dad who was a stock eliminator racer, told me it was a waste of money and I would not go any quicker. I finally broke down and did it. The ET's and MPH stayed the same. Why, because the stock ignition had enough spark energy to complete the combustion.

 

[JeremyH]

How much did you pay for the gms coils and 2 sets of spark plugs? I bet more than it would take to make an intercooler. Btw those gms coils are probably the shittiest version of aftermarket coils out there, and experience the most failures, seriously.

That money could have easily made an intercooler set up, your priorites are def not straight, ask these other guys if they tested gap with non-intercooled setups, its going to be alot less forgiving. Then again im one of those guys who would never ever ever run a power adder with out a cooler. Btw have you tried datalogging iats?

Badass intercooler, cheap and good quality been tested and used by many $79
http://cgi.ebay.com/ebaymotors/CXRa...ptZMotorsQ5fCarQ5fTruckQ5fPartsQ5fAccessories


Aluminum piping kit 2.5 or 3" comes with lots of piping, couplers and t-bolt clapms 50-75$
http://www.s197forum.com/forum/showthread.php?t=24885&highlight=springs


Anything else you might need they have all kinds of sizes of piping and coupler for cheap.
http://www.siliconeintakes.com/


Seriously man you can build and intecooler setup for $200 easy. Skip fast food for a month lol.

 

[Five Oh Brian]

How much did you pay for the gms coils and 2 sets of spark plugs? I bet more than it would take to make an intercooler. Btw those gms coils are probably the shittiest version of aftermarket coils out there, and experience the most failures, seriously.

That money could have easily made an intercooler set up, your priorites are def not straight, ask these other guys if they tested gap with non-intercooled setups, its going to be alot less forgiving. Then again im one of those guys who would never ever ever run a power adder with out a cooler. Btw have you tried datalogging iats?
Seriously man you can build and intecooler setup for $200 easy. Skip fast food for a month lol.

Dude, allright, you win. I fucked up in purchasing substandard crap for my car. I should have read every damn page of tech on this website before spending a damn penny of my money. Not gonna spend another dime until I get your permission. And the fast foods joints will all go bankrupt since I can't feed my fat ass there anymore. Happy?

 

[Five Oh Brian]

My parts failure is not likely to happen with your car Brian. I run 12 to 1 compression, 34 degrees of timing, 30lbs of boost, a magneto which has more spark duration, and a lot of fuel volume and cylinder pressure. That being said, the physics are the same of what's going on in the combustion chamber. I think you will have spark loss before damage from increased cylinder temps and detonation. I don't think that aftermarket coils alone can create enough spark energy to create an issue. If the coils were significantly more efficient over the stock ones, I believe that increasing the spark gap with aftermarket coils would also create a lean condition, which they don't. The reason is, the engine needs X amount of spark energy to create combustion. And increasing that energy does nothing to improve combustion effinciency.

I first experienced this back in the early 80's when I raced my Stage 1 Buick. The car had an 11.5 to 1 455 and ran 12 flat. I had been trying everything to get the car in the 11's. I still had the factory single point re-curved distributor in it with the OEM coil. Friends at the track bugged me non stop to put a MSD distributor in it with a 6AL and MSD coil. My Dad who was a stock eliminator racer, told me it was a waste of money and I would not go any quicker. I finally broke down and did it. The ET's and MPH stayed the same. Why, because the stock ignition had enough spark energy to complete the combustion.

Mark, thanks for the illustration. It all makes sense. However, I didn't buy aftermarket coils to go faster and I didn't believe a word of the advertising that says there's more power from changing coils. I did it to clear up the slight misfire and/or spark blowout. The alternative fix that everyone keeps pushing is gapping the plugs way down, but that cost me probably 30 hp. I'm not satisfied in giving up that kind of power if another relatively inexpensive fix exists - hence the $249 set of coils.

Sure, the simple solution may be getting an intercooler. But, I'm not handy enough to build my own intercooler, nor can I spend the $'s to have one done for me (kids in college, mortgage, and all that goes along with it). What's wrong with me wanting to make the most of the setup I have? I guess I'm done soliciting help with this issue, so thanks to everyone who responded. I'm gonna try running several different gaps to see what works best on MY car. Might not be the same as what everyone else runs, but that's okay. If the GMS coils puke, I've got the stock coils to fall back on, so no big loss there.

 

[JeremyH]

Dude, allright, you win. I fucked up in purchasing substandard crap for my car. I should have read every damn page of tech on this website before spending a damn penny of my money. Not gonna spend another dime until I get your permission. And the fast foods joints will all go bankrupt since I can't feed my fat ass there anymore. Happy?

Haha. Wouldnt take it that far.

I stopped eating out every day for lunch and buying drinks at the gas station, was $250 a month back in my pocket, thats mod money right there, thats why I made the reference.

Do your thing man, just giving you some good advice to make your car faster and safer for cheap. Everyones gota appreciate that!

You seem to over analyzing this whole thing man. They are plugs, gap them to the recommended spec and put em in, thats what this all comes down to.

 

[Five Oh Brian]

Update time. I went to Pacific Raceways to race today with the new coils and spark plug gap opened up to .045". I am very impressed with the results! Bigger gap (vs .028") improved my trap speeds by 2-3 mph!

New personal best from the 60' all the way through the 1/4 mile!!! 11.79 @ 113.92 backed up with an 11.85 @ 114.01. Worst run of the day was a 12.01 @ 113.42, which is still better than I had been averaging before I widened the spark gap.

 

[BruceH]

Nice runs Brian.

 

[Five Oh Brian]

Nice runs Brian.

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!

 

[Marc s]

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!

Brian, your car ran great today, good job. Mine pisses me off!. I poured 10 gallons of gas on it and lit it on fire.

 

[Five Oh Brian]

Brian, your car ran great today, good job. Mine pisses me off!. I poured 10 gallons of gas on it and lit it on fire.

As tempted as you were to light your car on fire, you & I both know it'll be fine after you go through the suspension and get the geometry right. You still ran 11.60 yesterday, which is decent considering how tough it is to launch with the current suspension settings. I can't wait to see your car run after you get the suspension kinks worked out - it'll be 10.80's all day long for you!

Thanks for your advice for my car. It's amazing how the little details can make such a big difference. I really didn't expect the car to run so well yesterday. I would have been happy running 11.9's and 12.0's, so running 11.79 and 11.85 was icing on the cake.

And it's great to see the trap speed coming up so I know my car is making more power now. Based on that 114 mph run and the 3,660 lb race weight (which includes me), that works out to roughly 385 rwhp (a 20 rwhp improvement with proper spark plug gapping and the GMS coil on plugs).

This winter you'll be sorting our your suspension and I'll be adding the water-methanol injection + CMCV delete plates. I suspect you'll still be much faster than me, but it's always great to compare notes and timeslips with you!

 

[max2000jp]

Update time. I went to Pacific Raceways to race today with the new coils and spark plug gap opened up to .045". I am very impressed with the results! Bigger gap (vs .028") improved my trap speeds by 2-3 mph!

New personal best from the 60' all the way through the 1/4 mile!!! 11.79 @ 113.92 backed up with an 11.85 @ 114.01. Worst run of the day was a 12.01 @ 113.42, which is still better than I had been averaging before I widened the spark gap.

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.