Quote:
Originally Posted by sperry
I'm not trying to say that coating the DP is bad... I just don't see that there's any massive benefit to it, at least not when compared to the cost.
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On a car running a CAI and a FMIC I probably wouldn't suggest somebody send their downpipe to us to be thermal coated. I'd tell them that the results probably would not justify the expense for them. While the post-turbo exhaust under boost happens to be a heck of a lot higher than 600 degrees (and there are plenty of guys running EGT probes post-turbo who have posted results all over the Subaru forums), I also don't think having a coated or wrapped downpipe is going to matter enough for exhaust gas velocity reasons to really justify doing it. However, of course, everybody's budget is different and the possibility of seeing gains plus having a nice, black downpipe is more than enough justification for a lot of people with a larger wallet than I.
With a short ram and/or a TMIC the coating or wrapping is ABSOLUTELY worth the time and expense. Most people purchasing their first downpipe are going to have a top mount intercooler on the car for quite some time, possibly for the rest of their ownership of the car. There are many, many more cars running TMIC's with turboback exhausts than cars where the owner spends the cash to upgrade to a fmic setup. Most cars with mild turbo upgrades up through 20G or so in size don't even do fmic. AND.... most FMIC setups end up running short rams anyway (although the intercooler is a more pressing issue when it comes to engine bay heat and obviously direct heat from the dp).
Anyway, on pre-turbo exhaust parts, we have seen repeated spool-up and response benefits to our coating. Maintaining the heat and energy inside of the exhaust gas going through the headers (especially with aftermarket steel ones!!!) and the uppipe absolutely translates into a measurable spool increase of up to ~300 rpm. It is regularly seen that with a non-coated stainless header, your spool-up gets quicker after a couple of pulls... this is due to the exhaust heat soaking into the header. We don't see that with coated headers so you get the quickest possible spool right off the bat. ....oh and the coating we do on turbine housings in conjunction with the P&P is also very effective at quickening spool-up and increasing response. Usually they'll hold boost towards redline better as well....
There are literally dozens of posts from different customers online with before-and-after measurements of underhood temperatures. Most people can't do this though because they weren't running an aftermarket downpipe prior to purchasing ours... few people swap between parts so there aren't that many opportunities to actually do non-coated vs coated temperatures. For most, the extremely obvious difference before-and-after kills their motivation to do scientific testing. Just with your face and your hands when you open the hood, it's as obvious as opening the fridge and opening the [hot] oven. The difference is not something small, it is
HUGE. We're talking underhood temps going from a couple hundred degrees down to only a little above ambient. It is blatantly apparent, and there's plenty of non-biased commentary online to back that up. It has been years since we were actually asked to show numbers and I don't have data anymore. We do, however, have an STI in the shop with our downpipe
uncoated on it so that's a good opportunity for us to get some fresh numbers on underhood temps and intercooler temps in various situations (while driving at different speeds and different amounts of full throttle time, after idling for 2 minutes, 5 minutes, 10 minutes, etc). Truly, I'm not super motivated to take the time and effort to do that though. We haven't seen a direct request for this sort of information for years. Again, it's SUCH a big, night-and-day difference that it isn't even a question in most peoples' minds.
btw -- there's a thermal dispersant coating that we do for anything metal that you want to
radiate heat as efficiently as possible, and it's pretty trick stuff. Can increase the efficiency of an intercooler or radiator by up to 20%. Race teams also use it on brake calipers, oil pans, cylinder heads, transmission cases, oil coolers, intake manifolds, etc... as long as there's good ambient air flow over the part, it will shed head faster than uncoated. We've shown on FMIC cars (one local GT30 STI in particular) that it really does work shockingly well. Post-intercooler air temps were actually getting down to exactly ambient, which was never the case before the coating.
So I wouldn't claim it's for everyone. sperry, if you asked me if you should coat your downpipe I'd say it's probably not worth the time and effort to take it off and ship it back and forth to us plus the cost of the coating because of your setup. If you were running a TMIC, I'd tell you to do it. Either way, it's obviously up to you because whether the $100 is a lot or a little isn't something I can decide
Jeremy