Having had the PowerStation equal length headers fitted last week (to my MY03 STi, Milltek, EcuTek)- which look great, and stainless and shiney (and changing colour nicely!).... I thought I wanted the undertray refitting...

However, general concensus seems to be to leave the undertray off - for cooling - but wrap the headers.

Currently, the tray is off and they are naked steel. This looks great, and if it's not going to cause problems I'd probably like to keep it like this - unless I'm seriously losing out on the power front.

I've had a quick look around and can't see anything that is likely to get soooo close to the headers that it would melt (wires, fan shrouds etc.) - so can't see a problem leaving it as it is....

Any advice as to what I should do would be much appreciated - or comments that will put my mind at rest, to leave it as it is, or even to refit the undertray would be appreciated.......

Thanks

Shades

 

You will be losing on the power front, no question, also on the spool up front.

Also your underboonet temps will be higher plus your headers will no doubt travel very close to your oil filter and heat your oil up unnecessarily.

I WOULD NOT leave them unwrapped.

 

Hmmmmmm..... just been discussing this with Rich at the Powerstation.

His serious recommendation is NOT to wrap. Two main reasons:

1. The wrap doesn't stay put or tidy for very long with normal use. It degrades and needs replacing every 8-10 months to maintain effective wrapping / tidyness. It's not cheap stuff....

2. Without wrapping, the headers get VERY hot. With wrapping, they get SERIOUSLY SERIOUSLY hot - to the point that it hardens the steel and potentially causes longevity problems with heating/cooling down causing the headers to crack.

He did mention that, if I were driving a race / rally car - then wrapping would be a good idea to squeeze every available pony from the engine..... for a road car, they never wrap.

The Spec C has factory heat shields on it's headers - which is obviously the ideal - but I can't see making and fitting custom heatshields for the PowerStation headers (whatever make they are) being anything other than massively un-cost effective......

So - under-tray and wrap both staying off - for the time being...

Anyhow - they look much prettier like that

Shades

 

Just to ask...

Is anyone else happily driving around with unwrapped equal length stainless steel headers, and more than happy to be doing so with no adverse effects??????????????????

 

Mine has undertray off and wrapped. Wouldnt leave em unwrapped, can cause huge underbonnet temps and heat the oil in the sump.

Also, wrapping makes them more effective as it causes them to keep the heat inside and causes the air to move faster etc.

Everybody I know has em wrapped. And if you wrap em properly it will stay put.

 

Would never use stainless unwrapped either. Mine's been on for over a year & don't look any worse for wear.
I'd disagree with the heat cylcing/hardeing thing - or rather would look at it from the other side: no wrapping gives far higher heat cycling (temps will go from 850C down to 400 within 30s without wrap, but will take 10 minutes or so with), also the heat loss through the system without the wrap will give a far larger temperature gradient across the whole length, again causing weakening.
The headers go very very near to many feed pies, the radiator... you really want the heat in not out.

 

I've heard that using stainless steel headers unwrapped can actually melt adjacent wiring. Besides, the heat cycling argument doesn't wash for me either. I would rather the pipework cooled down slowly rather than quickly. It's the rapid thermal gradient that would cause problems, either from changes in metal crystallinity or due to expansion/contraction. I'm wrapping my headers!

 

One other thing: once the headers are wrapped I'm going to apply heatproof paint to the lagging. That should keep them neater by reducing the amount of road muck and oil that can adhere to the wrapping.