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Discussion Starter #1
As many of you know we were the first to sell the Jet-Hot coated GT-Spec Header direct from our inventory with no waiting while gaining the agreement from GT-Spec that they would honor their full two year warranty on headers coated by their authorized dealers.

We went with Jet-Hot for a very specific reason - their JH 2000 coating works constantly and consistently in pre-turbo exhaust applications. It is rated to 2250*.

Over the past few months I have seen users and competitors advocate other coatings. 90% of them I contact about the 1550* temperatures seen in pre-turbo exhaust pieces have stated that their coatings are not sufficient. There are only two or three that I have contacted that are willing to say that their specs would be sufficient.

Be very careful an aluminum coating that looks very good and works great on NA applications but is rated at 1200* constant and 1500* intermitent will not last. The coating company itself replied to go elsewhere:

No, Sorry..... You need **** Coating in ****.
Thanks,
*******
Anyone that wants us to forward the original email may contact me.

Just be careful out there and do your research - contact the coating company and ask them specifically will their coating work on pre-turbo exhaust pieces seeing extended periods of 1550* temperatures.
 

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The only way you'll run that hot, is if you have a cat converter in you uppipe.
The STI does not have a cat converter before the turbo.
 

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Ed is correct. 1500F is an entirely realistic sustainable temperature.

The other thing to consider with aftermarket coatings is what will happen if it fails, chips off, and ends up going through your turbine. My guess would be that only a major failure would cause damage to the turbine, but do you want to take that chance?
 

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Second that. It is easy to believe 1500 deg F. I had 4 thermocouples in my old BMW to synchronize the Hillborn throttle bodies'. Normally aspirated and 1350 deg F at the exhaust ports at full throttle.
 

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In a modern car (i.e. STI) a typical EGT would be about 750F. Depending on timing and A/F you might get it to increase about 400F. I not sure where you get you data from, but hey... if you guys want to spend your money go ahead.
 

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i agree that you would see temps in the 1500 range at WOT. i had an egt guage in my 91 AWD Talon and at WOT it always registered 1450-1500. 1650 was the redline so to say. anything over that might result in melted pistons. that was for the old 4g63 dont know what the tolerances for the revamped 4g63 in the evo are.
 

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Discussion Starter #8
dmpi said:
I not sure where you get you data from, but hey... if you guys want to spend your money go ahead.
On top of years of tuning turbos - 18 months of continually tuning Subaru - GBs of data logs - and good thermocouples. Those EGTs you are talking about are from NA applications or in C which usually are around 800* - decades of wrenching on those.

Even at stock pig rich levels you can see temps of 1250.

In a drag you may see upwards of 1600 on a drag tuned car - but sustained temps over 1550 are pushing for instance on a long straight of a track.
 

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Snax said:
Ed is correct. 1500F is an entirely realistic sustainable temperature.

The other thing to consider with aftermarket coatings is what will happen if it fails, chips off, and ends up going through your turbine. My guess would be that only a major failure would cause damage to the turbine, but do you want to take that chance?
The coating is on the outside of the header, I don't understand how it would go through the turbine.

-st
 

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Discussion Starter #10
For optimal performance we have Jet-Hot coat the inside and outside of the header. It keeps the heat in the exhaust gasses thereby keeping exhaust velocity high and underhood temps low. More and more companies are starting to offer internal coating as a result of the success many users have had coating internally and externally their headers and other exhaust components.

While flaking into the turbo is a concern (I suspect it breaks down at a microscopic level over time though) - my warning to investigate coatings you may select, relates as much to the damage the piping will suffer as certain areas break down more than others causing heat stress and fatigue from varying pipe temperatures. With the wrong coating pre-turbo you may bring about the premature death of your exhaust components.

This is one reason why many exhaust companies will not honor warrantees when their parts are coated. However, GT-Spec readily agreed to honor their 2 year warrantee when we have the headers coated by Jet-Hot, when we first approached them on the subject. Since that time we believe they have agreed to honor the warrantee when the header is coated by Jet-Hot by any of their authorized dealers. Though we believe we are still the only one to maintain a substantial inventory of them coated on a continual basis.
 

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ChargedPerformance said:
For optimal performance we have Jet-Hot coat the inside and outside of the header. It keeps the heat in the exhaust gasses thereby keeping exhaust velocity high and underhood temps low. More and more companies are starting to offer internal coating as a result of the success many users have had coating internally and externally their headers and other exhaust components.

While flaking into the turbo is a concern (I suspect it breaks down at a microscopic level over time though) - my warning to investigate coatings you may select, relates as much to the damage the piping will suffer as certain areas break down more than others causing heat stress and fatigue from varying pipe temperatures. With the wrong coating pre-turbo you may bring about the premature death of your exhaust components.

This is one reason why many exhaust companies will not honor warrantees when their parts are coated. However, GT-Spec readily agreed to honor their 2 year warrantee when we have the headers coated by Jet-Hot, when we first approached them on the subject. Since that time we believe they have agreed to honor the warrantee when the header is coated by Jet-Hot by any of their authorized dealers. Though we believe we are still the only one to maintain a substantial inventory of them coated on a continual basis.
Ah, that's the first I've heard of that. So the coating on the inside doesn't disrupt flow at all?

-st
 

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Discussion Starter #12
The coating is only a few mils thick and while it does have a surface to it is not much rougher than the existing raw stainless steel surface already in the headers. Jet-Hot claims their process does not result in runs internally and from as far in as I have been able to see their claims apper to be true. We can not see far around the bends on the passenger tubing which is the most complex but there is no evidence that there is any problem with their internal coating.

Coated vs. uncoated produces results that we feel justify the additional cost. The slightly slower spool up of uncoated headers is virtually eliminated - from tuned for OEM manifolds to tuned for the coated headers the differences between the two in spool up on many different turbos was statistically insiginificant on the 2.0L. Enough data has not been gathered on the 2.5L and 39 so far between uncoated and coated but all indications from our coated customers is that it is performing very well with regards to spool up and torque results.
 

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ChargedPerformance said:
The coating is only a few mils thick and while it does have a surface to it is not much rougher than the existing raw stainless steel surface already in the headers. Jet-Hot claims their process does not result in runs internally and from as far in as I have been able to see their claims apper to be true. We can not see far around the bends on the passenger tubing which is the most complex but there is no evidence that there is any problem with their internal coating.

Coated vs. uncoated produces results that we feel justify the additional cost. The slightly slower spool up of uncoated headers is virtually eliminated - from tuned for OEM manifolds to tuned for the coated headers the differences between the two in spool up on many different turbos was statistically insiginificant on the 2.0L. Enough data has not been gathered on the 2.5L and 39 so far between uncoated and coated but all indications from our coated customers is that it is performing very well with regards to spool up and torque results.
Once again, thanks for the info!

-st
 

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dmpi said:
In a modern car (i.e. STI) a typical EGT would be about 750F. Depending on timing and A/F you might get it to increase about 400F. I not sure where you get you data from, but hey... if you guys want to spend your money go ahead.

That's not correct, 1450-1550 running hard on a wrx or sti is normal
where did you tap into for your egt probe?

I did mine at the number three exhaust manifold between 3-6 inches away, otherwise you;ll get a faulty reading.
 

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I would argue that coating of the interior of the pipes is an improvement for protecting the turbo. Bare steel at those temperatures tend to scale and shed the flakes. SS, Inconels, and Hast alloys excluded...
 

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Discussion Starter #16
I can't think of any aftermarket headers made for the WRX/STi that aren't stainless off the top of my head. But that is a valid point for someone who makes their own, a coating that specs to the appropriate temperatures can only be a good thing. Oh there might be one who does not use stainless (can't think of them off hand right now) and I think they include a ceramic coating on all their headers.
 

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Sorry. I missed the fact that your headers were SS. I just remember back when Jet Hot was new and header paint was a joke.

Coated, why not use cheaper mild steel?
 

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Discussion Starter #18
Re: USDM STi Review in JAPAN

GT-Spec has them manufactured in SS. When we selected their headers we approached them with the intent of only selling them if we could do so with coating - it is the only way we would use them and we wouldn't deliver less to our customers. So we have them stop by JH on their way to us and offer them to our customers coated direct from our inventory for immediate delivery. Most GT-Spec dealers offer it as well but after sale and most sell them uncoated. We decided later to carry a very small amount uncoated for those who really want the polished SS and we are still holding stock from our first order of uncoated - we actually woulnd't mind never selling them as we are certain our customers are better served by the coated.

The GT-Spec 2 year warranty combined with the JH new part coating warranties make the higher cost of stainless pipes and welds worthwhile. We fully expect on average people will get 5 years of good normal usage from them and more if they have them recoated right at the end of the JH 1 time free recoating a few years out. There aren't many aftermarket turbo headers that can do that and even fewer mild steel ones even coated.
 
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