punchdrunk

So previously I ran a decat on a 60mm exhaust. The car would smoke at idle and when reversing so I swapped the decat with an HFC - problem solved.

But I then decided that I wanted a T1R V70R header back exhaust and installed that at the weekend. Surprise surprise the dreaded smoke returned

I also noted that the inside of the exhaust tips has turned black since fitting. I'm assuming the car is running rich with the decat although it doesn't smell rich.

Thinking about this further it may be the header that is causing this problem as I can recall that the issue only started when I swapped the header - I now have a Buddyclub race header.

I haven't done a compression or leak down test although the car recently dyno'd at 202rwhp on a dyno dynamics. Mileage is 64k

Any thoughts or suggestions appreciated

SilverS2kF22C1

White smoke or grey/blueish smoke? White smoke is usually coolant, grey/blueish smoke is oil.

How is your oil level after you drive a few hundred miles (KM)?

punchdrunk

Thanks for your input.

The car doesn't lose coolant, but the smoke is definitely white. In fact quite a thick plume of white smoke then nothing for the rest of the journey.

Being an AP1 it burns oil for fun, but no more than usual. No leaks or funny noises from the engine.

The smell is of hydrocarbons. Soot in the exhaust is perhaps a sign the car is running rich and the plume of smoke is unburned fuel

suzuka-blue-s2k

If I remember correctly, black smoke means your running rich, so that wouldnt be your problem. Silvers2kF22C1 is right, the white smoke is antifreeze burning. Blueish smoke is oil burning.

So your burning antifreeze somewhere, possibly the headgasket.

SilverS2kF22C1

With your mods on a AP1 I don't think you are running all that rich if at all.

With a test pipe the car is going to 'stink' more.

If you are burning a bit of coolant it would smell like rotten eggs.

Does it do it only after it has sat for a bit/cold motor?

punchdrunk

Interesting comments there.

Loss of coolant or overheating is not an issue. There is no oil residue in the expansion tank/coolant. I don't suspect head gasket failure.

The issue is only present with a decat.

No smoke with the stock cat or the Berk HFC.

The smoke is a kind of lingering smoke which then turns to a plume with more gas. The smoke is white.

I've had a car with headgasket failure before - the smoke is constant and the car will be losing coolant. No such problem here.

The issue, this time round, manifested itself a short period after the car had been left for 10 minutes or so after a hoon. It didn't repeat itself although the smell of hydrocarbons was intermittent and strong.

Am I barking up the wrong tree suspecting the header?

SilverS2kF22C1

yeah, I don't think it is a fault of the header.

I am leaning towards a valve seal issue. Basically oil leaking down into the combustion chamber or even into the exhaust runner, when it sits and it burns off when you start the car.

With a test pipe it is going to stink no matter what, some cars smell worse then others, and by stink smell like fuel/hydrocarbons.

punchdrunk

Good point.

Valve stem seals would normally be bluish smoke. I'm not sure a cat/hfc can mask a stem seal issue, but I could be wrong there.

The valve clearances were checked and adjusted 5,000 miles ago.

How can I check for valve stem seal problems?

Thanks

SilverS2kF22C1

Could be the PCV too not sealing all the way too.

ronnuke

That white smoke is what the catalytic converter's job is to remove. Once you remove the cat, it no longer does that job and you have the hydrocarbon effluent. It is not a problem unless you are worried about global warming.....