Boost Blowing Out The Spark?

[IN 05 NT]

hey guys i heard a little about blowing out the spark on turbo cars...but dont know exactly what might be hapening,

atm my car dirves fine a erevs the whole range smooth until i full boost it,

when i come hard on boost the gaiges still reads 14-15psi....

but the car starts to full on hesitate....and sounds like its miss firing madly

i cracked a few old platinum plugs a few weeks back.....cracked the ceramic around the electrode and was causing a missfire, after hitting the rev limiter hard at a motorkhana

i since changed the plugs with just your ordinary off the shelf plugs, (as its a few weeks order time for platinum plugs for the 1g,)

the plugs i used were factory gapped to 1,1mm, and teh facttory 1g plugs are gapped to 0.8....so i regapped the cheapies to 0.8,

it was running fine for a few weeks up until recently...last few days,

does this sound like blowing out the spark?

i'll pull the plugs later...if i get thru polishing the beast for the show tomoz....

cheers, blake

[oldcorollas]

blowing out the spark is a convenient way to say it is difficult to ignite the more compressed mixture... but more people understand it if you say it is blowing out

bending the electrodes dwon from 1.1 to 0.8 may not be the best thing for them, as the electrodes are no longer larallel (on the surfaces facing each other).

you can buy cheapy plugs with a number of different gaps... at least in NGK..
standard is actually 0.8, but they are made in 1.1 (and specifiedas that in their part number)

there was a thread a while ago talking about the best gap for boosted spark, but i forget the words of wisdom.. 0-7-0.8 ish?

perhaps you could try getting some 0.8 gapped ones and going from there... is the heat range the same as the pt's?

pull plugs out, check they have not opened up etc etc....
and maybe limit boost a bit lower for the time being?

[clubagreenie]

Slightlt OT Stu but I've always checked and regappped plugs. They never seem to come right, added to plugs suiting more than one application (L9YC efi vs non efi Range Rover = 1.1mm vs 0.9mm).

Having said that I've always set them with a feeler gauge, tapping v lightly straight down, so keeping them parralell. But champion make a gauge about the size of a fifty cent piece but round with a tapered edge that I have also used and the amount of adjustment required shoudn't move it that much.

But then there was the apprentice who wanted 8 new plug tips as the ones they came with weren't the right gap so he "took them off" to replace them.

[YelloRolla]

I would be inclined to look at the spark plugs after a run under full load and doing a reading. As you have stated that you cracked the porcelain of the platinum plugs I am concerned that you are running too lean.
Unlike an AFR reading from your local dyno, it won't tell you what the AFR's are, BUT if it is excessively lean, then you can tell right away - White = catastrophic.
Edumacating what colour to look for is difficult over teh web. I like my plugs to look like my nice strong cup of coffee.
Also what heat range are you running? NGK with heat range 8 is the warmest that I would go.
OC is on the money for mine - gapped at 0.8 is enough (a bit closer if you go up in the boost).

[YelloRolla]

But then there was the apprentice who wanted 8 new plug tips as the ones they came with weren't the right gap so he "took them off" to replace them.

now that is GOLD.

[IN 05 NT]

hmmmm,,,,,i'll wind down the boost again and try that, i cbf to pull the plugs out today...hands are already foobar after just applying the polish....still got to wipe it down

so you guys agree that it most like ly is the plugs?

the heat range was the same, same reach...all the same ecept not paltinum and had to regap,

blake

[oldcorollas]

for mine - gapped at 0.8 is enough (a bit closer if you go up in the boost).

i was trying to remember your words of wisdom

if all you changed was plugs, then maybe...

but you said it was also misfiring before, which is why you pulled them out?
but you also said it was running fine for a while.. so it is probably a plug issue, now that they have lost their new and clean-ness

pull out one plug.. see what it looks like... give you ides for tomorrow

[YelloRolla]

I run 0.7 on my car, but I run 22lbs boost (only low boost at the moment )

[IN 05 NT]

I would be inclined to look at the spark plugs after a run under full load and doing a reading. As you have stated that you cracked the porcelain of the platinum plugs I am concerned that you are running too lean.
Unlike an AFR reading from your local dyno, it won't tell you what the AFR's are, BUT if it is excessively lean, then you can tell right away - White = catastrophic.
Edumacating what colour to look for is difficult over teh web. I like my plugs to look like my nice strong cup of coffee.
Also what heat range are you running? NGK with heat range 8 is the warmest that I would go.
OC is on the money for mine - gapped at 0.8 is enough (a bit closer if you go up in the boost).

*looking at the NGK book....

1g plugs,....BCPR6EP-N-8

plugs i used, (for RB30) BKR6E-11

B= thread diametre, BK, BC are both 14mm

R= resistor

6= heat range...2-10..... 2 being hottest.....10 being the coldest

E= thread length, both 19.mm.


theres to many to type...but you get the gist there a bit different....

time to polish

[xero]

a mate at work has a silvia running about 22psi of boost on his sr20, and he had this problem for a little while... he gapped them all the way down to a bout 0.2 - 0.4 to recitfy it...
it work as a bandaid solution till he got that sort and a better tune...
now hes running at about 0.6 - 0.7 with the same boost

[kingmick]

either close up the gap on the plug till you reach the right compromise or get an msd 6a etc to boost spark. It is a very common problem in older boosted engines with coil and dizzy.
It is a problem as old as boosted engines, no rocket science to it at all, you either boost the spark or close the gap.

[YelloRolla]

^^^
Amplifyling the spark is always a good idea, but I would think it best to determine the reasons for the mis-fire prior to spending too much money.

[IN 05 NT]

what are the MSD's worth...ive heard little about them.....

[peedman]

Ive got one sitting under my bed. $200 from the US, just the base model MSD6A.

[oldcorollas]

but do you have coil-on-plug on the 1G anyway?

all you need is for enough spark energy (or potential difference) to be able to create an inonisation path in the compressed mixture. most modern cars are able to do that already.
big old V8's with a single coil trying to fire 8 plugs find it hard..