21 replies to this topic

[moog101]

Micron hae recently brought to market a new method for construcing exhaust header. They basically force water into narrow walled stainless steel tubing, which is held in a pre-designed mould. Obviously this means they can have some pretty wild designs for speeding up gas flow and moving pressure waves about.

The headers (in conjunction with a race end-can) are yielding about 10-15% power increases on the new Suzuki GSX-R 1000, for which no other can manufacturer has even seen an increase at all.

The technology seems to work, and the potential is quite exciting, to my mind at least.

Can anyone tell me if this method is used in F1, and if not, why not?

[moog101]

http://www.micronexhausts.com/main.htm

go to 'new products' then 'hydratech' or 'serpents'

[MRC]

This is called hydroforming and was not developed or thought up by Micron, nor are they the first to use this forming technique.

I read some of a book once on F1 car construction. The focus of the book was a Bennetton F1 car (if I remember correctly) from the 90's. They were welding tube bends together to form the header. From the welded seams appearing on headers nowadays, on an F1 car, I would assume that the construction method has not changed.

[Cory Padfield]

MRC is absolutely correct.

Hydroforming would be perfect for forming three-dimensional bends in tubular exhausts. Unfortunately, this is another example of how low-volume F1 usages do not merit expensive tooling investments.

Cory

[moog101]

but the power, the power, why not if there is an apparent power gain

oh, and I am sure that Micron are the first to offer it to the masses

[marion5drsn]

Exhaust Pipes; The problem of manufacturing exhaust pipes is not necessarily of power. It is the bending of the pipes so as not to thin the pipes on the outside of the curve. The old method was to fill the pipe with a low temperature metal that would melt at the boiling point of water. Then bend the tubing to prevent rippling the pipe on the inside of the curve. When bending the pipe the inside wall always gets thicker and outside gets thinner. Proper welding of the joints shouldn’t be at big problem using modern welding techniques. I think I wrote of this when MS’s suspension collapsed at Monaco. Proper fitment of the joints should prevent a lot of the rough edges inside the pipe as the outside is of little consequence. I notice that the advertisement didn’t mention any welding of the pipes! Just how did they join the pipes together? There aren’t any dealers in the Los Angeles area so I can’t go to a dealer and observe the joint. Altho I must admit that it is an interesting advertisement! Certainly the exhaust is one the big contributors to the large power output. If one makes a linear layout (chart) of the exhaust using about 320 degree duration cams it is readily apparent that a lot of thought has gone into the making of the exhaust pipes. The ones I’ve seen pictures of are much longer than I had visualized. Yours M.L. Anderson

[MRC]

Sand bending is another technique that was used to bend tubes. You fill the tubes with sand and block off the ends and the sand helps the tube from pinching.
Even mandrel bent tubes will have a thinner wall on the outside of the bend. The do keep their diameter and shape however to a high degree.
I believe that the latest Corvette exhaust has some hydroformed pieces. I think Borla makes it, but I'm not positive. Some sections of production truck frames, etc have been produced by hydroforming.
I'm not an expert on hydroforming, but I also believe that there are some limits on what kind of crazy bends and whatnot that you can do. It seems like hydroforming is utilized when complex variations in some sort of tubular cross section are needed.
Also, I have never seen a motorcycle muffler (except a BMW) that could even remotely considered anything but dead simple (read - low tech).

[imaginesix]

It's actually the frame rails of the Corvette that are hydroformed. And now the new GM SUVs are getting hydroformed frame rails too.
I believe they are made by Magna.

[moog101]

I'm not talking mufflers (which do not have to be 'High Tech' because the **best** exhaust has no muffler, just a nice straight, properly tuned length - ie: like motorbike cans) I am talking HEADERS! The article mentions no welding because none occurs! the sections from header to pipe to can slips together and is held gas tight with springs. Very easy to change lengths quickly & easily. The minute steps in the walls where they slip together are aligned to not upset the flow - they present no 'edge'.

[MRC]

It appears to me that they are welded in some areas. The collector in the picture for the "Hydratech" sure looks TiG welded to me. Also the header flange bosses (part that presses onto exhaust seal) look turned and welded onto the main tube.
Amazingly, for an aftermarket company, Micron seems to have enough of a clue to spend some money in the right place and is running WAVE. I suspect 95% of the power gains are due to some guy running WAVE models for each engine, and has little to nothing to due with the pipe construction method.
As for decent race headers that are constructed by the cut and weld method; most are internally purged before and during welding. Argon is typically fed into the inside of the tubes to completely purge out all air. This results in a completely smooth and oxide free weld, inside the pipe. While, there is a very slight reduction on diameter, the internal weld is completely smooth, needing no after clean up or grinding. This is done with all good race headers, along with dairy and pharmaceutical grade equipment.
I also don't see how lenghts of pipes for this header would be easy for them to change if they are paying for hydroforming tooling. Can't be too cheap.

[desmo]

Argon purging the interior of the tubing- sounds like TIGing Ti tubing, although done there purely to prevent oxidization. How does argon purging help create a smooth weld inside the pipe?

Wouldn't any company manufacturing headers use WAVE or a similar simulation software to help design them?

[MRC]

When you weld SST (and don't purge the inside) you will get a black crusty surface at the weld. Some people use some kind of flux, but it doesn't give the same results. As the heat penetrates the weld joint, the outside is shielded by your shield gas, the other side is forming oxides, even slightly ahead of your bead. Oxides don't stick together too well. With internal purging, you also get full penetration with less heat input.
I have also known some people that will internally purge roll cages when doing AISI 4130. I will weld some 321 SST tubing and some 4130 tubing, each with and without internal purging. (Hopefully I can do it this weekend). Then I will slice them and take a picture. I'll see if I can get them posted up on this forum, then you guys can be the judge.

As far as WAVE goes, yes, anybody with $100,000 and plenty of time to construct a model would love to use it. I have used WAVE for two years and I can tell you that a lot of time goes into just building the model. Furthermore, these guys must have to get their hands on each engine they are making a header for, since I highly doubt that the manufacturer's are jusst going to give them: port shapes, flow coefficients, combustion data, etc, etc. I'm just suprised that an aftermarket company would have the $100k to spend on a liscense per year. I don't think many aftermarket companies can afford this. Seems like money well spent to me.

Mark

[desmo]

Thanks MRC I'd love to see those. I have a friend who has welded Ti for a local bicycle company here and I've watched him weld up Ti tubesets with a TIG and plugs stuck in the ends of the tubes with a hose running through them to the Argon tank. He says once you figure it out, it's no harder really than TIG welding Al or Steel. For Ti, not purging the interior of the tubes is simply not an option as the weld zone will become oxidized resulting in a faulty weld. Would the weld be any stronger using argon in the interior with steel?

[MRC]

I can't say that I've done any pull tests are any fatigue tests with internally purged joints. However, like I mentioned before, you get a good clean weld all the way through. I can't see how the non-purged welds will be as crack resistant in fatigue or have the same strength as those being purged.
I worked with a guy who made NHRA approved roll cages and he said that internally purging the tubes made them less likley to crack at the weld or the heat effected zone.
I completely agree with you on purging Ti alloys when welding. I did a Ti fuel cell (for methanol) and didn't have the inside purged well enough and it developed some cracks later. (Although it was some weird alloy Ti-5Al-2.5Sn)
Should I have those pictures posted in a new thread? Thanks.

Mark

[bergwerk]

Originally posted by MRC
I believe that the latest Corvette exhaust has some hydroformed pieces. I think Borla makes it, but I'm not positive.

Borla doesn't have the technology to make anything of the sort.

[Cory Padfield]

MRC,

Why do say weird alloy? Ti-5Al-2.5Sn is used frequently because it is a simple single-phase alloy with inexpensive alloying additions.

Cory

[MRC]

Cory, you seem correct that Ti-5Al-2.5Sn is a common alloy. I got the stuff locally and it was 'leftover' material from a previous job. The guy said it had good chemical resistance and that it was a uncommon alloy. My mistake. After a little research today, I found out that titanium is very crack sensitive to Methanol, but has very good chemical resistance otherwise (apparently, even with other alcohols). Probably good part of why it cracked.
Also found out that Arvin makes the exhaust for the Z-06. They didn't mention any hydroforming. Guess I'll have to lay off the hukka for a while.

[desmo]

MRC, as usual great stuff. Post the pics anywhere you'd like, I'd still like to see them. I'd never heard of using argon to purge the interior of a steel weldment but if one is going to use inert gas on the outside of the weld why not on the inside as well? Surely it couldn't hurt.

[desmo]

Here's a good short read in PDF on the Timet exhaust components used on the Corvette Z06.

http://titanium.net/...tNewsletter.pdf

It's good to see Ti finding it's way into relatively reasonably priced cars. Hooray for Chevy leading the way.

[MRC]

Here are the pictures of some weldments with and w/o internally purging, as promised. Sorry it took so long. The round tubing is 1.750" x .035" 321 SST tubing. The square tubing is AISI 4130 steel tubing, 1" x .035". The 321 SST was welded with 347 rod. I did one weld with and one without internally purging for each tubing. The internally purged welds should be on the right (silver in color). All welds were done with Argon inside & out, and with a gas lens. Heat settings were also not changed between purged and non-purged welds. This was just something quick and dirty with minimal prep. The welds were not cleaned after welding. It took me some help from someone else to get these on here.

[Engineguy]

Originally posted by imaginesix
It's actually the frame rails of the Corvette that are hydroformed. And now the new GM SUVs are getting hydroformed frame rails too.

...and the frame tubing on the new water-cooled Harley V-ROD. Hydroforming is getting real popular real quick in the auto industry.

[desmo]

MRC, thanks for posting those, fantastic. I am quite surprised at the very obvious differences apparent. I'd never heard of internally purging steel tubing when welding it, I thought it was just a Ti thing.