A friend of mine approached me about doing a small welding project for him. Before we get into the specifics I think some background information is in order. This particular individual of whom I speak of is no ordinary guy. If this guy could under go a heart transplant and get rid of his God given pumper in exchange for a turbocharged straight six he would do it in a heartbeat (I mean a power stroke) This guy eats, breaths, and sleeps horsepower.
His obsessions are not limited to one particular area, I mean if it burns hydrocarbons he either wants to thrust his right foot into it or twist the grip till it falls off. The guy goes from Mustangs, to RX7s, to street bikes, and even to trikes. OK…the trike doesn’t actually run but trust me that thing is freakn’ fast in his own mind. This guy collects turbochargers to make sure he stocks one for every single internal combustion engine he owns including his lawnmower.
From the time I have known him the vast majority of his attention has been given to his 1989 E30 BMW. There is one thing I know for sure about horsepower and that is a person can never have too much. My friend is no exception to this rule. However I have to give him credit for he is willing to work for it. By that I mean he pioneers his way to his wants. He does all his own work and modifications and is willing to accept failure. Once he has had his fun, and failure, it’s time to move on to bigger fun and, possibly, bigger failure. By failure I simply mean pushing an internal combustion engine to it’s “I have given you everything I got” limit and “there is nothing left for me to do but explode”. I think he uses the Edisonian approach to its quintessential core. He does his research, he theorizes, he plans, and he organizes however when he gets to a point where laws of nature can’t be calculated there is nothing left to do but “give it a shot”
OK, I think you get the point. Onto the nitty gritty and more about the welding project. He is looking to upgrade the turbocharger he previously retrofitted onto his M20 2.5 litre 6 cylinder in his BMW E30. He had a smaller one and it had done its time. He is upgrading to a Holset HX-35 turbo and coupling it to a BD Power 16 cm2 housing. Where do I come in? He needs a 3” stainless steel V-band clamp flange welded to the BD Power cast steel housing in order to couple his exhaust to the turbo. My first reaction to his request was hmmmmm…I’m not sure this is possible. Cast steel to stainless steel? I don’t know about that.
Now I know there are people out there that say they can “weld” anything. However in some cases the term “weld” is used pretty loosely. Anyone can point a MIG gun at something and pour molten metal onto it however this, in my mind, does not constitute welding. I needed to know if this was theoretically possible in the professional welding world. By that I mean is it possible to get a scientifically correct weld between the 2 metals. So I did some research and this is what I think I know. Technically, it seems that the process of welding stainless steel to cast steel is not actually possible. The professionals whose opinions I read said that they would not guarantee the weld, most of these professionals had lots of experience and spoke intelligently about the topic. Then there was a whole different group of people who said that the process is totally doable, unfortunately none of this individuals came across having extensive knowledge in regards to the finer aspects of metal fusion. So I decided to follow in my friends foot steps. Let’s take the Edisonian approach. I agreed to give it a go however he would have to be willing to accept my failure. He said he was good with that, I’m unsure I believed him.
The game plan was this. My friend agreed to give up one of his turbos he had stashed away (it was one he was probably going to retrofit onto his washing machine) so that I had something I could practice on. Here’s the set up I used; my Miller Syncrowave 180 SD TIG welder set to 120 amps, a 2% ceriated tungsten, pure argon set at 18 CFH, and a 309L stainless steel filler rod. I set out to make a few practice runs. Before welding the turbo I used a combination of MAPP gas and oxygen to preheat the cast. I used the MAPP gas simply because it was what I had available to me. I was shooting for a preheat temperature of between 300 – 400 degrees Fahrenheit. I could only get the turbo up to 240 degrees. Once it was heated I lay down a test weld. Like butter! It flowed great and the puddle control was fantastic. Only after about an inch of weld I wanted to add in a stainless aspect. I hunted through the metal pile and found a small chunk of 304 stainless steel. I plasma cut out a radius to fit the contour of the turbo housing. Through down another pre heat session and then melted some 309L stainless rod to the two of them. The filler flowed really nicely and the puddle was well maintained between both the cast steel and the stainless scrap. I got this covered, give me the real stuff now.
When it came down to the real deal there was nothing to it. I preheated the BD Power housing to 240 degrees and then started laying down the beads. I alternated between 3 different spots in order to keep the heat well distributed. I finally was able come full circle and complete the weld. Upon inspection everything looked great. No slip ups and no warping.
In the end I am not convinced it is a technically “sound” weld however I am certain his new bigger turbo is going to blow up long before my weld does. I think it worked out well and wouldn’t hesitate to do it again.
An addition to this post, that is not welding related, is how the extra combustion pressures are dealt with when turbocharging an engine. An area of weakness when increaseing cyinder pressures is the head gasket, they take a beating. A modification that is made to the M20 engine is the insertion of stainless steel wire into the deck of the block circumfrencing each cylinder. The deck is cut “in car” with only the cylinder head removed using a special cutter being driven by manual efforts. The cutter used was made by Isky Cams model 100 GRM. It is simply a cutter mounted to the outside of a boring bar that allows you to set your depth of cut and circumfrence. Once set you just drop the tool into the cylinder, it’s pins ride on the deck and you manually cut grooves around each cylinder. The width of groove is determined by the cutting blade width and is .035″ which then allows a .040″ Stainless Steel wire to be wedged in. The inserted wire adds support to the existing steel head gasket and helps to prevent blow outs. Cool hey?