[naz200]

Hi guys,

Just looking for opinions what might be causing the misfire at top end. The dyno results are below

null_zps281952e4.jpg Photo by naz200 | Photobucket

null_zps46c0d0c8.jpg Photo by naz200 | Photobucket

null_zps04ba668c.jpg Photo by naz200 | Photobucket

It is running -9's, 750cc inj and power fc MAP sensors. It has heat range 8 plugs but standard coil packs. The car has been mapped at 1.6 bar and fuelling is ok but boost suddenly drops at two points when misfiring begins.

Is this the kind of symptom seen when coilpacks are the issue? There is no misfire at 1.3 bar and it makes 470 flywheel bhp at that boost.

Any opinions would be appreciated.

Cheers

Naz

 

[naz200]

Also, it was mapped on the road and plugs were upgraded due to top end misfire with heat range 7 plugs.

 

[[email protected]]

What do you have the plugs gapped too ?

 

[nailsgtr600]

As Jamie says...

 

[[email protected] M/S]

Shut the spark plug gap down will help as it is easier for the spark.

I would say it will be a coil issue thou.

Fattening the fuelling up will help as well.

 

[naz200]

They are 0.8mm but iridium so I'm wary of gapping them in case I damage them. They are the ngk iridium plugs bkr8 eix iirc

 

[[email protected] M/S]

They will close down easily, try them at 0.6mm if that helps I would say you have a coil failing

 

[naz200]

Thanks Mark, I will probably get some splitfires too.

Is the drop in boost seen at the same time as the start of misfiring a result of the loss of spark? Is this what normally observed with top end misfire?

 

[r32manhoolee200]

Defo coilpacksfailing under full load

 

[naz200]

Defo coilpacksfailing under full load

Cheers dude, will defo be investing in new ones soon. No rush at the moment in these conditions lol. I'm sure the gritters will be out regularly soon

 

[r32manhoolee200]

Yep lol dam uk roads
My brothers r34 suffered from same symtoms had a bad batch of coil packs ended replacing them twice from new

 

[naz200]

Which ones did he use? Everyone says splitfires are good but have also heard they dont last long

 

[r32manhoolee200]

Find out for you tomorrow

 

[r32manhoolee200]

Cant remember lol was three years ago will have a look tonight or tomorrow for you bud

 

[Raj32]

Give your current coil packs a clean. Take the boots off them and get some dialectric grease in between them.

I had the same issue, but giving the coil packs a clean worked.

It's because your spark from your spark plug is shorting out on the coil pack metal base.

 

[Raj32]

Try this:

/forum/210386-best-coilpack-test-fix-certainly-looks-like-cheapest

Put the GTR.co etc in as I can't (less than 15 posts I can put a link in)

 

[naz200]

Give your current coil packs a clean. Take the boots off them and get some dialectric grease in between them.

I had the same issue, but giving the coil packs a clean worked.

It's because your spark from your spark plug is shorting out on the coil pack metal base.

Thanks, I will try that and gapping my plugs to 0.6mm. I have a baffled twin turbo pipe going on so I'm interested in seeing any effect on dyno performance figures. If the misfire is still there then new coil packs will be bought in the near future.

Cheers

Naz

 

[Raj32]

It would be interesting to see if the baffled pipe does improve performance. I would suspect not unless you do suffer from turbo shuffle badly.. But please do let us know!

 

[naz200]

Try this:

/forum/210386-best-coilpack-test-fix-certainly-looks-like-cheapest

Put the GTR.co etc in as I can't (less than 15 posts I can put a link in)

These rails look like a good idea too

 

[naz200]

Turbo shuffle was eliminated when my car was mapped with map sensors on pfc djetro. Interested to see if it spools up earlier