Gruppe-S v2 header review + DIY coating instructions

[bugblatterbeast]

I finally gave in and ordered a gruppe-s header and a can of thermal barrier coating. I believe Crucial racing uses Techline MCS followed by a top coat of BHK. I decided to use just the BHK coating as I didn’t want to handle hexavalent chromium. To get a bit more insulation I slapped on some ceramic loaded silicone paint overtop the BHK (after curing).

Coating instructions:

1) Separate the header and sandblast with 120 grit aluminium oxide grit. You do not want to use glass bead as a rough open pore finish is needed for adhesion. To get the header separated you need to beat it apart using a rubber mallet (Jon @ TDC’s Tip). If you are really anal about scuffing the insides thoroughly, you can get an old speedo cable and attach a foam sanding pad to the end of it. Chuck the other end in a drill and run the rotating sand pad up the pipe.

2) Wash the header. I used soap and water followed by an acetone bath.

3) Hang the header bits so that all sides can be reached with the spray gun.

4) Set the gun pressure to~30psi. You need a HVLP gun to get a good finish. Spray till the surface is just wet

5) If you have a non food oven, use it to bake the finish. I didn’t so I used a heat gun. I started with the gun shooting down the collector pipe, then had it blow through each of the openings for the head side ports. With the collector taped shut and hot air blowing into the driver side ports, I was able to get 300+ degree air coming out of the passenger side ports. Curing took about 1 hour per opening.

6) Step back and enjoy your handy work. Installation is much easier if you mask off the slip joints and O2 sensor bung before spraying.

Quantities : For those wondering how much BHK to order, I used ~4oz to do the header inside and out. If you a spray gun with lots of overspray, you will need to budget for more. It took about 3 lbs of grit to blast the header and 2 liters of acetone for the wash.

Fit and Finish: The headers were pretty well made. The welds were even and tidy. Inside the various ports, the pipe had also been welded to the flange and subsequently machined. The merge collector was quite smooth but shorter than optimal due to the stock uppipe flange position. The outside of the pipes had been polished to a mirror finish, nice but not necessary. The insides however had not been cleaned thoroughly. Anyone using these headers right out of the box should make sure they wash and blow them out completely. I pulled a solvent soaked rag through the pipes 4 times before it came out free of metal shavings and grinding debris.

Installation of these headers was quite simple. At first they header wouldn’t go on because the flange to flange separation was too small. All that was needed to get them on was loosening of the slip joint bracket and 3 hits with a rubber mallet. Once the separation was adjusted all three flanges lined up perfectly. Initially there was a small leak, which was fixed when I re-torqued the nuts after the first heat cycle.

These headers do not provide a mounting point for the passenger side grounding strap. There is a threaded hole on the passenger side cylinder head where the strap can be attached (the driver side has a similar hole with a ground strap attached). The hole is M8x1.

The stock undertray will burn with these headers, even if they are coated. The problem is the flexibility of the undertray. At speed, the tray gets pushed up and contacts the pipes. A small insulating pad and some aluminium foil fixes this problem.

Initial driving/tuning impressions: The sound of the exhaust is changed quite a bit by these headers. The rumble at idle is significantly reduced. It is still there, but not as obvious. Between 2000-3000 RPM, the exhaust is a bit louder but more mellow in tone. From 3000-redline the exhaust is also a bit louder but angry rather than mellow sounding. Pre tuning, the turbo did spool a little later, maybe 200-300 rpm later but the top end was noticeable faster and smoother. After fiddling with the tuning a bit (I’m not done yet) I got the difference down to ~150rpm compared to the stock manifold. The VE of the engine has definitely improved. Before adjusting the boost tables, boost was down 1 psi from 3k to redline yet the mass flow rates were up. Also, before tuning, the engine started knocking a bit a 3k and 4k rpm (increased cylinder filling with no adjustment in fueling/timing). Calculated load has increased about 5% from 2500-redline with a couple percent drop below 2000. Clearly, more fiddling with the tuning is in order…..

[looneycanuk]

I finally gave in and ordered a gruppe-s header and a can of thermal barrier coating. I believe Crucial racing uses Techline MCS followed by a top coat of BHK. I decided to use just the BHK coating as I didn’t want to handle hexavalent chromium. To get a bit more insulation I slapped on some ceramic loaded silicone paint overtop the BHK (after curing).

Coating instructions:

1) Separate the header and sandblast with 120 grit aluminium oxide grit. You do not want to use glass bead as a rough open pore finish is needed for adhesion. To get the header separated you need to beat it apart using a rubber mallet (Jon @ TDC’s Tip). If you are really anal about scuffing the insides thoroughly, you can get an old speedo cable and attach a foam sanding pad to the end of it. Chuck the other end in a drill and run the rotating sand pad up the pipe.

2) Wash the header. I used soap and water followed by an acetone bath.

3) Hang the header bits so that all sides can be reached with the spray gun.

4) Set the gun pressure to~30psi. You need a HVLP gun to get a good finish. Spray till the surface is just wet

5) If you have a non food oven, use it to bake the finish. I didn’t so I used a heat gun. I started with the gun shooting down the collector pipe, then had it blow through each of the openings for the head side ports. With the collector taped shut and hot air blowing into the driver side ports, I was able to get 300+ degree air coming out of the passenger side ports. Curing took about 1 hour per opening.

6) Step back and enjoy your handy work. Installation is much easier if you mask off the slip joints and O2 sensor bung before spraying.

Quantities : For those wondering how much BHK to order, I used ~4oz to do the header inside and out. If you a spray gun with lots of overspray, you will need to budget for more. It took about 3 lbs of grit to blast the header and 2 liters of acetone for the wash.

Fit and Finish: The headers were pretty well made. The welds were even and tidy. Inside the various ports, the pipe had also been welded to the flange and subsequently machined. The merge collector was quite smooth but shorter than optimal due to the stock uppipe flange position. The outside of the pipes had been polished to a mirror finish, nice but not necessary. The insides however had not been cleaned thoroughly. Anyone using these headers right out of the box should make sure they wash and blow them out completely. I pulled a solvent soaked rag through the pipes 4 times before it came out free of metal shavings and grinding debris.

Installation of these headers was quite simple. At first they header wouldn’t go on because the flange to flange separation was too small. All that was needed to get them on was loosening of the slip joint bracket and 3 hits with a rubber mallet. Once the separation was adjusted all three flanges lined up perfectly. Initially there was a small leak, which was fixed when I re-torqued the nuts after the first heat cycle.

These headers do not provide a mounting point for the passenger side grounding strap. There is a threaded hole on the passenger side cylinder head where the strap can be attached (the driver side has a similar hole with a ground strap attached). The hole is M8x1.

The stock undertray will burn with these headers, even if they are coated. The problem is the flexibility of the undertray. At speed, the tray gets pushed up and contacts the pipes. A small insulating pad and some aluminium foil fixes this problem.

Initial driving/tuning impressions: The sound of the exhaust is changed quite a bit by these headers. The rumble at idle is significantly reduced. It is still there, but not as obvious. Between 2000-3000 RPM, the exhaust is a bit louder but more mellow in tone. From 3000-redline the exhaust is also a bit louder but angry rather than mellow sounding. Pre tuning, the turbo did spool a little later, maybe 200-300 rpm later but the top end was noticeable faster and smoother. After fiddling with the tuning a bit (I’m not done yet) I got the difference down to ~150rpm compared to the stock manifold. The VE of the engine has definitely improved. Before adjusting the boost tables, boost was down 1 psi from 3k to redline yet the mass flow rates were up. Also, before tuning, the engine started knocking a bit a 3k and 4k rpm (increased cylinder filling with no adjustment in fueling/timing). Calculated load has increased about 5% from 2500-redline with a couple percent drop below 2000. Clearly, more fiddling with the tuning is in order…..

 

You know it is coming...

 

[LittleBlueGT]

Jon at TDC claims to tune headers so there is no lose in spool (vs OEM manifold and catless UP) hopefully you can do the same.

[bugblatterbeast]

good to know. I think I'm still running a bit richer than I need to during spool up. The tune is still pretty rough as I was in a hurry this weekend.

 

 

update: I almost have the setup spooling like the stock manifold with just an AVCS adjustment. The top end is better than stock and there is practically no loss of spool. I'm going to play with the tune a bit more to see if the last bit of spool up can be recovered. Based on the 16 street pulls I made last night, I've determined that you need a minimum of 5 identical pulls to get enough statistical certainty to discriminate the changes made by a 2 degree AVCS shift....

 

driving notes: the slip joints leak when cold. it takes about 30 seconds for the noise to diminish to quite reasonable levels and another 30 for it to go away.

 

update 2: peak loads are up from ~3.0 to 3.22 at lower revs and up to 2.8x at around 5300 rpm.

[mickeyd2005]

Where did you get the BHK coating from?

 

Did you take pictures?

[bugblatterbeast]

Where did you get the BHK coating from?

 

Did you take pictures?

 

I got the coating supplies from Caswell Canada.

 

I have photos but haven't gotten around to decimating them to a resolution that is acceptable on the forum. Truth be told, I wasn't going to bother as there isn't a whole lot to see. They are basically the gruppe-s headers in satin black. If you can point me to a freeware tool for re-sampling the jpg I'll get it done (right now I don't have any descent photo editing tools)

[Joon525]

I got the coating supplies from Caswell Canada.

 

I have photos but haven't gotten around to decimating them to a resolution that is acceptable on the forum. Truth be told, I wasn't going to bother as there isn't a whole lot to see. They are basically the gruppe-s headers in satin black. If you can point me to a freeware tool for re-sampling the jpg I'll get it done (right now I don't have any descent photo editing tools)

If you want to zip them up and send them to me I'll gladly resize them, zip them up and send them back to you.

[bugblatterbeast]

Thanks for the offers. I found a photo editor.

 

here are some pics. I decimated the resolution to 640x480 so they wouldn't overflow smaller screens.

 

note the masking of the o2 bung and slip joints

[mbacis]

Looks nice and good writeup.

 

Are there any unequal-length headers available that do not integrate the UP? I'd like to eventually go the header route, but I already have an UP and a header install would be rather simple if I didn't have to replace the UP.

 

EDIT: Just found that the Greddy STI header fits that bill.

[mickeyd2005]

whoo-hoo... reviews section is back up.

 

There are some unequal length headers here.

 

http://legacygt.com/reviews/showcat.php?cat=49

[TRS]

Looks nice and good writeup.

 

Are there any unequal-length headers available that do not integrate the UP? I'd like to eventually go the header route, but I already have an UP and a header install would be rather simple if I didn't have to replace the UP.

 

EDIT: Just found that the Greddy STI header fits that bill.

Nice collection of headers HERE.

[bugblatterbeast]

Looks nice and good writeup.

 

Are there any unequal-length headers available that do not integrate the UP? I'd like to eventually go the header route, but I already have an UP and a header install would be rather simple if I didn't have to replace the UP.

 

EDIT: Just found that the Greddy STI header fits that bill.

 

the gruppe-s is non-equal length. a big part of the reason I went with gruppe-s is the convenience of not having to pull out my uppipe. the second reason was TDC's favourable comments wrt the gt-spec header.

[NewScooby]

Nice write up. I ordered BHK from Caswell Coating to coat my Invidia UP and Down pipes.

 

I am dropping the pipes off at the sandblaster today (aluminium oxide grit). The sandblaster also runs a powdercoating business, so I am going to see if I can get him to spray the BHK for me and bake them for a decent price, or I will be doing the spraying myself.

 

How are you liking the header so far?

I will be porting and polishing the stock exhaust manifold when I install the UP/DOWN pipes and may go with a header down the road.

[bugblatterbeast]

So far I'm happy with the headers. I made a few more small adjustments to the AVCS around 3k rpm at light loads at the annoying sounds went away. I was definitely over-advanced in a few cells and exhaust reversion was becoming audible through the intake. Both the increase in output at light throttle and the measurements I did with a pressure transducer indicate the tuning is better now. At medium engine speeds I found that it was possible to do

AVCS tuning by observing the shape of the pressure pulses you see near the intake ports. I used the tap for the fuel pressure regulator to monitor the pressure (just shove the FPR hose into the compressor bypass vacuum line while tuning so FP doesn't go nuts). I'd post the plots but I can't get a trace dump from the scope I was using.

 

Also, the slip joints have stopped leaking while cold. I think they are bunged up with carbon now I'm acually happy they are there as the piping expands and contracts around 1/8" from blistering hot to ambient temperature.

 

Good call on having someone else sandblast for you. I was washing sand out of various orifices for days after....