I thought now that the car has been completed for nearly 2 years that it is about time I posted a few "completed" pictures. I say completed due to finally getting the cross over exhaust I always wanted installed.
Hopefully the pipes don't take on any colour as they are ceramic coated mild steel. I seriously considered doing stainless but couldn't bear thinking about how much heat they give off. My original set of 4 into 2's went a dull grey but that was from the tuning sessions on the dyno.
Tip to all - Get your headers coated after initial dyno tuning and ECU setting up as this usually kills ceramic coatings.
You are the guru when it comes to tech stuff. Had I known this earlier I would have had the exhaust made in st/steel then had it glass bead blasted and electropolished. This gives a really nice easy to care for look.
First, let me say your GT looks fantastic. Kudos on a well built car.
I have to reply vis-a-vis your discussion about the "science" of the different metals. I think you're mixing up conduction and convection. Whether your headers are stainless or mild-steel, they will both get hot from the exhaust gases flowing through them. The "heat they give off" is the heat you feel from "convection". If you have stainless headers at 1000 Deg F and mild-steel headers at 1000 Deg F, and you hold your hand 1 ft away from each - guess what - you feel the heat from both as the same since it's the convective properties of the heat through the air. The differences in the metals are significant from the standpoint of corrosion, strength, etc. Now as for coatings - this brings up a different set of issues - is the coating reflecting any heat energy back? does it have any insulating properties? etc?
Anyway, just my two cents. Again - great looking GT.
Hmm, after reading my own response and re-reading the tech article, I thought I better clarify a bit.
The tech article mentions the thermal conductivity difference, but what he fails to mention is that after running your engine for any length of time, the stainless or mild-steel exhaust (assume both uncoated, un-insulated) will both hit about the same terminal temperature since it's the temp of the exhaust gases that is the heat source in the first place. Thermal conductivity only indicates how quickly the heat is conducted throught the metal itself in this example. Imagine you're holding a piece of metal rod 3 ft long with 1-inch dia cross section. Hold one end in your hand and put the other in a stream of 1000 def F exhaust gas. With the stainless - it'll take longer for you to feel the heat since it's thermal conductivity is lower. However, after some amount of time you'll feel about the same temp in your hand.
I think the property Kalun was referring to had something to do with the radiative properties of the different alloys. I agree that a surface at 1000°F will convect just about the same amount of heat no matter what the surface is made of (as long as the air's ability to remove heat doesn't exceed that of the metal's to acquire more energy through conductance).
I am not a metallurgist, but I assume there is a difference is the manner or properties of how they transmit in an emissive manner through IR radiation.
Someone (preferably knowledgeable) please chime in before I talk myself into a hole.
I'll leave the debate on the exhaust to those that know. I just had the exhaust made and coated to limit heat radiance as much as possible based on all the advertising blurb from HPC, jet hot etc, to look as good as possible for as long as possible and to resist corrosion.
I just installed 450lb rear springs (up from 350lb) but ordered the wrong length and this is as low as it can go - no preload in the spring. I will replace these along with installing stiffer front springs soon.