[canderson]

I am very interested in getting downipes for my 335xi (AR or UR catless) and trying to decide if the ceramic coating option is worth it. What is the benefit?

Cosmetic? Nobody will see them.

Rust protection? OK, but will they really rust out faster than the un-coated factory ones? They are stainless steel right?

Reduce heat transfer to engine bay? Won't the heat transfer already be better by getting rid of the factory cats?

Heat retention for exhaust velocity? Doesn't make sense to me. Cooling the exhaust sooner should cause the pressure to drop sooner and reduce back pressure. Why do I want to keep it hot and high pressure?

Given the cost of the pipes and install on an xi the extra cost isn't an issue, but I don't want to throw money away either.

[IlChengis]

I just got a used set of 3" catless DPs and am sending them out to JetHot to get their Extreme Sterling coating.

In our case aesthetics are obviously not the reason.

Personally I don't know whether or not the absence of cats in itself would cause a drop in temperature, but I have a feeling that the increased size of these pipes (they are *much* bigger than stock) will bring their surface much closer to the center tunnel, car frame and other components.

Add the fact that you'll be making more power and pushing the snails harder and I can easily see how that area will be much hotter than it would be with stock ones, catless or catted.

I have done some research and wound up going with JetHot, I got in touch with a solid guy there that emails back very quickly (I can give you the info if desired) and I was quoted $80 for a triple coat (inside and outside) of Extreme Sterling, their best coat right after the JetHot 2000 which is overkill for our application (and costs $210).

I say do it.

-Walter

[mycoupe]

Originally Posted by IlChengis

I just got a used set of 3" catless DPs and am sending them out to JetHot to get their Extreme Sterling coating.

In our case aesthetics are obviously not the reason.

Personally I don't know whether or not the absence of cats in itself would cause a drop in temperature, but I have a feeling that the increased size of these pipes (they are *much* bigger than stock) will bring their surface much closer to the center tunnel, car frame and other components.

Add the fact that you'll be making more power and pushing the snails harder and I can easily see how that area will be much hotter than it would be with stock ones, catless or catted.

I have done some research and wound up going with JetHot, I got in touch with a solid guy there that emails back very quickly (I can give you the info if desired) and I was quoted $80 for a triple coat (inside and outside) of Extreme Sterling, their best coat right after the JetHot 2000 which is overkill for our application (and costs $210).

I say do it.

-Walter

Do you know what the temps are of the pipes under roadrace conditions? The sterling is good to 170 degrees, right?

[IlChengis]

The sterling is good to 170 degrees, right?

1700F

Originally Posted by mycoupe

Do you know what the temps are of the pipes under roadrace conditions?

No idea, but I suspect way below 1700 degrees F. One way to get a close idea would be to shoot them with an IR thermometer while doing a couple of dyno runs. Some dynos are elevated, I presume it could be done.

-Walter

[stratplaya06]

On an XI the last thing you want is to ever touch those pipes again. I got AR ceramic coated and am very excited to get them put on.

The fact that the heat stays in the exhaust gasses (DPs are coated inside and out) and not radiated out into the pipe or engine bay also makes the exhaust flow better.

When it comes down to it, we xi guys throw some serious cash to get these installed, so why not spring for the coating? Any reduction in underhood temps is beneficial, especially for those with DCI's.

[dlbrooks18]

ceramic coating is worth it to reduce heat

[SoCaliBimmer]

Sometimes it's good and a lot of times it doesnt do much and starts flaking and coming apart after time, wrapping is a good option but can also catch on fire.lol. I think just leaving them stainless would be best..

[BrianMN]

Ceramic coating also helps keep exhaust gases inside hotter, letting it flow and exit faster

[Jeff@TopGearSolutions]

Originally Posted by BrianMN

Ceramic coating also helps keep exhaust gases inside hotter, letting it flow and exit faster

Truth....


My last car was Supercharged, my first set of headers were ceramic coated, when i switched to a polished stainless steel there was drastic heatsoak increase in the engine bay, thats when I knew ceramic coating was worth it.

[kanecvl]

Originally Posted by JPSlick

Truth....


My last car was Supercharged, my first set of headers were ceramic coated, when i switched to a polished stainless steel there was drastic heatsoak increase in the engine bay, thats when I knew ceramic coating was worth it.

I was wondering if anybody noticed a real difference. Sounds like the way to go especially with dci

[scalbert]

Originally Posted by canderson

Cooling the exhaust sooner should cause the pressure to drop sooner and reduce back pressure. Why do I want to keep it hot and high pressure?

Velocity drops which reduces scavenging.

[scalbert]

Originally Posted by IlChengis

One way to get a close idea would be to shoot them with an IR thermometer while doing a couple of dyno runs.

I have a few at the office as we use to represent Raytek; now owned by Fluke.

[IlChengis]

Originally Posted by scalbert

I have a few at the office as we use to represent Raytek; now owned by Fluke.

I am sure those are a tad bit more accurate than the Harbor Freight one I've been eying lately...

-Walter

[techlogik]

Do a search locally, you probably have a few places that do thermal/ceramic coating with some well known brands that will withstand 2400F.

It will help with heat, and last longer/protection.

They usually charge about under $100 locally for a set of downpipes and takes a few days.

Worth the money.