Good evening.
under full boost my sapphire seems to misfire hugely.its running a stage 1 and dark green injectors.accelerate slowly and all is good.new genuine ford plugs fitted.any help appreciated.

 

Firstly I question why you have those injectors. Stage 1 defines an increase in boost pressure, along with a suitable calibration (i.e. EPROM) for the same.

This makes me believe it may be more than stage 1?

This aside, misfires are a common issue, chiefly due to the antiquated ignition system.

When boost pressure is increased, as is cylinder pressure which is what results in the phenonium of the spark being "blown out".

What are your plugs gapped to?

Martin

 

Hi martin.thank you for taking the time to reply to my query.
my sappjire is a recent purchase and i was told it has 330 bhp.it was sufferig a misfire at idle so i replaced the spatk plugs and that sorted this issue.cant remember the gap.what gap should i be using to help eliminate this issue.

 

Yes, so as I thought stage 3, not 1

Standard gap is 0.25 in (6mm) but then... that is for a standard engine, which yours is not.

Do you know the ignition system is in decent order, so leads, rotor, cap etc. It all has to be perfect to stand a chance of being half decent on a tuned car.

If so you could try dropping the plug gaps slightly, which isn't ideal.

One easy mod you could do if all else fails is purchase a GRP A coil, which has a higher output.

Nirvana here is wasted spark, but that does not come cheap and not necessary in my experience.

Martin

 

Hi.just removed a spark plug and the gap is .035 about .9mm.do you suggest i reduce this to .025/.6mm.leads.cap rotor all replaced.so should be all good there.thanks

 

Yes, that is too big.

Like I say the figure I state if for a standard engine, so does not apply in this case so at the very minimum it would need to be this.

Martin