Stahl Headers Not Doing L28 Headers Anymore

[johnc]

You need a fixture to weld headers otherwise you have no idea where the primary outlets end up. Collectors can be purchased from SPD, Burns, or others.

[Xnke]

Yep, I'll make a jig to do it. It's not rocket science to weld one up, just takes thought and patience.

 

And yes, that does include the collectors to the secondary tubes; I have to provide the secondary collector.

[ollie]

I snuck an order in on June 2 for 1.5" primaries and 2.25 collector with Judy. At the time, she said that was their last set of 1.5" pipes...

[Xnke]

Yep. I placed my order for 1 5/8" pipes this last tuesday. You're going to be lucky to get it in a month, because they don't have any more 2.25" collectors...I tried to order them and they said they were out, but would have more in the middle of july.

 

So, the packing list includes:

 

L28 Square Port Flange

 

1 5/8" Primary tubes

 

2.5" collectors

 

2.5" collector bend

 

You know, those Stahl headers look awful close to the old Clifford header...the only difference being that the Clifford has 3-bolt flanges on the collectors, where the Stahl has a bend and two parallel pipes.

 

Stahl Header:

 

 

Clifford Header:

 

Edited June 17, 2011 by Xnke

[Leon]

Surprisingly, I've never noticed that! Really makes me want to install my Clifford header, but the flange is warped...

[ollie]

So the process with Stahl has been very cool...I've been dealing directly with Jere and he had me make a template of my head...turns out it matched their flange quite well but it is cool that my header will be matched well to my particular e31 head. They don't want you to do any grinding of the flange at all to port match so it truly is a custom header. There is a ton of good info on their site. Sounds like mine is being built now.

Edited June 23, 2011 by ollie

[josh817]

I'm kind of confused on what is included for $280 and the type of welding. When you guys say tubes do you mean just 6 primaries? Maybe the primaries are cut into sections so its like a puzzle trying to figure out what piece in what order on whichever primary?

 

I already have a flange and collectors, just need some tubes :]

[Xnke]

I just got my parts today, I'm going to go take a photo for you.

 

Ok, here are two photos. You really can't mess it up badly, all the tubes are labeled. I might replace the collectors with different or better units...these look a little "rushed".

 

 

Edited June 28, 2011 by Xnke

[josh817]

Wow. All that for $280 thereabouts? I'm curious if I can get just the tubes without the flange and collectors.

 

Here are some tips for fabricating. Getting those round tube ends into the square ports on the flange nice and flush:

 

That is part 4 of 6. I watched all of them and everything before part 4 is basically how to mock up the bends and such. Since you already have the bends you don't really need that part.

Edited June 28, 2011 by josh817

[Xnke]

No, the price was more than 280$. Jere said it'd be 260$, plus shipping...Judy quoted me a much higher price. All told, shipping included, the parts in the photos came out to be 365$.

 

So far, JohnC, I haven't needed a jig. the header tubes are bent such that you CAN NOT assemble the header wrong, it just won't work. The only variable that I will need to jig for is the distance from the flange to the first bend; and that will wait till I get the car back in MY shop instead of my buddy's shop, 45 minutes away.

 

But what I'm saying about it being not possible to put it together wrong...here's what I mean.

 

start with the #4, #5, and #6 tubes, and tie-wire them together where the primaries fit parallel, going into the collector. They have a kick bent into them that will only let them fit one way...don't try to line up the cut tube ends, they don't line up.

 

Lay them out on the table, with the flange, so they are roughly lined up with the holes.

 

Make the minor adjustments to the bends needed to get the head sides of the primaries where they need to be, square to the head. I had to tweak the large radius bend in #6, it was a little tight. #5 was fine. I squashed the tube ends just enough to get them into the flange, and had to cut and turn #4 a few degrees, because it was twisted a little and I don't have the tools to twist that tube without kinking it. Now, all the tubes come together and fit each other properly, and fit into the head flange correctly. I tacked up the three tubes, and tie-wired them together tightly in four spots.

 

Take Note! I have the tubes tacked to the header flange for JIGGING ONLY!!! I am NOT going to be welding the tubes in until I get the flange bolted in the car, and can snake the primaries in and make sure they are tilted correctly to clear the frame...I have a spare block and head laying on the work table right now, to make sure the tubes clear the block. That DOESN'T MEAN the tubes will clear the steering shaft!

 

The #1, #2, and #3 tubes will be a little trickier, but again, they will only fit together ONE WAY. The only angle that you can adjust is the angle that the tubes meet the flange, and that should be square in two axis, so it's not really adjustable. The only distance you can adjust is the distance from the head flange to the first bend, which you can do from trial assembly in the car a few times. It may not be necessary, really...mine looks long the way it's tacked up now, but it's not THAT long...and it'd be really really easy to get to the bolts as-is.

[johnc]

You will need a jig to make sure the completed header hasn't moved out of position due to welding distortion. That parts may all fit together just fine and only go together one way, but the collector outlets could be out of position by inches after everything is welded together. That header is a fairly tight fit near the steering shaft and at the collector outlets near the floor pan. If the outlets are pointed the wrong way or moved outwards you may not be able to get a "Y" on it.

[Tony D]

Thin tubing welded distorts and moves flanges John?

 

Say it isn't so!

 

You will only make the mistake once...

[Xnke]

Sure, that's understandable. The only spots I'd be worried about welding distortion are at the head flange, and you're right...the possibility is significant. Welding the primaries into the collector can be done fairly cool, since they are thin.

 

Same thing happens to .093" CroMo tubing when welded too hot into FSAE Baja runners too...only then the whole frame skews and you're NOT going to move it short of cutting and welding again...Been there, done that. Crew even made a T-shirt with the statement "But Joel, I measured six times, and cut twice!" on it. (Joel was the Mechanical Engineering Department Head, and oversaw the FSAE teams.)

 

My initial reaction to your statement about the jig was more to the tune that I'd never be able to get the tubes placed correctly, which is why I responded as to how it only fits one way. Now I've looked at the photos some more and see the worry about the floor pan. I figure it'll clear the steering shaft, as it's not a full 1-3/4" unit and Jere said there was a 1-7/8 tube version available as well, so if there was enough room to make those fit then the 1-5/8 ought to be less fussy to fit. We'll see. I definitely will measure six times and cut twice.

 

I have called Cone Engineering today and spoke to a gentleman about getting a pair of 3-1 and a 2-1 merge collectors, transition cone, and the bullet vanes to match, for a very reasonable sum of money. MUCH better pricing than SPD or Burns, however there is more assembly required. The Cone Engineering collectors are 9* merge units, as opposed to the approx 20* units supplied by Stahl. I'll use them on another project in the future I'm sure.

Edited June 28, 2011 by Xnke

[josh817]

Would it be logical to insert the primaries into the collectors and then weld? This way you are heating only one primary, so the other two are holding everything true and preventing distortion?

 

 

Xnke, the price you mentioned is still pretty darn good for us who don't mind doing the work to piece it together. I'm interested to see your progress.

 

 

JohnC, I forgot about bullet vanes and transition cones. I'm curious about the importance of a bullet vane. I've read about them before but it didn't seem like a major design flaw if you didn't have them. I don't think I have them in my collectors but I would be willing to cut the secondary tube off to weld one in. The transition cone I presume is this:

 

You had posted this picture in another thread when discussion megaphone tips. Everyone was saying the best setup is no pipe to the back of the car but rather a cone on the end of the header after the secondary merge. Does that cone still help even for those who run a pipe to the back of the car or out the side of the car in front of the rear wheel?

[Xnke]

I tacked the primaries up to the header flange this evening, and then when I got them all aligned tacked the tubes up where they lay alongside each other in six places, on each set of primaries. When the car comes home Thursday I'll pull the intake and exhaust, and start fitting them.

[Tony D]

You guys may want to go to Burns Stainless and check out their Header Fabrication article.

Traditionally you start at the head, and tack weld to the outlet flange, and then stitch/weld the tubes in a manner so as to minimize warpage. But generally having a set start and end point rigidly set allows you to go from one end to the other tacking and then welding.

 

I would NOT recommend starting at the collector and going backwards, or 'working from both ends to the middle'!

 

I don't even want to relate why I feel so strongly on that last point, but let's just say you don't want to end up like a couple of my past endeavors!

 

[josh817]

I hear yah Tony. I don't know about Xnke's collectors but mine slide on and springs hold the halfs together. I figured sliding the tubes in so you know all three tubes will fit at that end and then tacking onto the flange. Compared to tacking one tube at a time and finding out that the tubes don't sit beside each other properly to allow the collector to slide on.

 

I'm just pulling this out of my ass... lol but it makes sense in my head!

[Leon]

You had posted this picture in another thread when discussion megaphone tips. Everyone was saying the best setup is no pipe to the back of the car but rather a cone on the end of the header after the secondary merge. Does that cone still help even for those who run a pipe to the back of the car or out the side of the car in front of the rear wheel?

 

Yes, it does. The megaphone is placed at the section of pipe where you want the resonance effect. The calculations are somewhat involved, but in a nutshell, the closer the megaphone is to the exhaust valve, the higher the design rpm range. Length and taper determine bandwidth and magnitude.

 

Our FSAE engine had a megaphone at a calculated pipe length and the muffler afterwards, also at a calculated length. Dyno showed very significant gains when combined with our intake design (10-15% across the board).

[josh817]

So, in another exhaust thread:

http://forums.hybridz.org/index.php/topic/100277-240z-headers/page__p__940204__fromsearch__1#entry940204

JohnC mentioned an 80% minor throat size compared to the tube size to the back. Granted, he was talking about a megaphone on the end of the exhaust I think, but I'm assuming right now that it applies to the megaphone on the end of the header too.

 

With that said, a 3" pipe to the back, would yield this where you can vary the length x to adjust the angle/taper.

 

 

Did you also squeeze the throat back down at the end of the megaphone, like in the picture I posted before? I read that it is similar to the stinger pipes we use to run on our 2 stroke karts in which the megaphone draws more fuel/air mixture into the cylinder and sometimes out the exhaust valve in the case of huge overlap. Then the squeeze of the throat forces the air/fuel that came out the exhaust, back into the cylinder, kinda supercharging it. With a tuned intake that has pulses of air/fuel hitting up against the backside of the intake valve, I can see 15% gain like you said. :]

Edited June 29, 2011 by josh817

[Leon]

So, in another exhaust thread:

http://forums.hybridz.org/index.php/topic/100277-240z-headers/page__p__940204__fromsearch__1#entry940204

JohnC mentioned an 80% minor throat size compared to the tube size to the back. Granted, he was talking about a megaphone on the end of the exhaust I think, but I'm assuming right now that it applies to the megaphone on the end of the header too.

John was speaking of a megaphone at the collector. One at the end of an exhaust pipe will have a much diminished effect.

 

 

Did you also squeeze the throat back down at the end of the megaphone, like in the picture I posted before?

We did not squeeze the throat down, as that will reduce performance because of an increase in pumping losses. As John has also mentioned, run as big of a pipe off the megaphone as possible. There's no point in creating pumping losses when you don't need to.

 

 

I read that it is similar to the stinger pipes we use to run on our 2 stroke karts in which the megaphone draws more fuel/air mixture into the cylinder and sometimes out the exhaust valve in the case of huge overlap. Then the squeeze of the throat forces the air/fuel that came out the exhaust, back into the cylinder, kinda supercharging it. With a tuned intake that has pulses of air/fuel hitting up against the backside of the intake valve, I can see 15% gain like you said. :]

The resonance effect is what 2-stroke engines use in order to have any sort of powerband, and the effect is similar on a 4-stroke. The physics of it aren't really like the way you describe, as a properly tuned exhaust "scavenges" the cylinder. The megaphone reflects compression waves all the way down its length, turning them into expansion waves. At a certain rpm bandwidth these expansion waves hit the exhaust valve just before it closes, drawing out more burned gasses, dropping the pressure in the combustion chamber, which then admits more air/fuel mixture.

 

Intake tuning is the opposite, with compression waves increasing intake pressure causing a "ram" (or "supercharging") effect. An intake bell-mouth is the analogue to an exhaust megaphone.

 

A properly designed intake-exhaust combo will do wonders!