Mattc's Twin Turbo 104 conversion

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Ian B Walker

MB Enthusiast
Jun 7, 2003
300-24, saloon and coupe, E300 24 valve diesel estate
It was over a pint at Pammy's house one Christmas when Matt suggested I price out a twin turbo conversion. Being Christmas and having had a pint or so I immediately put the question in the booze at Christmas category. The end of January looms and the phone rings, its Matt wanting the worked out price. And so for the Booze Category theory :wallbash:. Told him I would get back to him with a figure, which I did some days later.

I knew where I could get the important parts i e Turbo kit. But the rest of the parts was going to be a tad awkward.

To start with. Obtain a really old cylinder block. This we managed to do. One with 315,000 miles on it. Madness I hear you all say, but wait. In a block that used there will be little stress left in it and we are going to load it with a lot stress. The block was examined by one of my machine shops and found to be perfect, no boring out needed. Just a honing.

The next step was to get hold of the turbo kit. One kit obtained, parts checked against the list. Parts missing :mad:. Never mind, what we did not have we could make or adapt. As an example. Con rods. The had to be shortened by 0.7mm. I went to my local machine shop (CNC) and discussed a way to machine 0.7mm out of the rods. One old rod supplied, machined and tested against a known good crank. Perfect. Using the same program 6 rods were machined.

6 Forged pistons were bought from a German supplier and 0.5mm was machined of the crowns. You may ask why? We have to lower the compression of the engine. The same supplier supplied 48 competition valve springs (104 heads have twin springs per valve), valve guides, gap less rings and heavy duty bottom end bearings.

The Block was assembled and all items necessary fitted. i.e. head, oil pump, sump, gearbox, stuff like that. We now come to the jigsaw bit. Exhaust manifolds fitted to head, turbo,s fitted to manifolds. Inlet manifold fitted to head, the removed. Something was not right. Call to Janner, who I hasten to add was more than helpful with pictures of pipework and the supply of a Split Second. More of that later.

The engine was test fitted to the car. Not very much room in there. Engine out and inter-cooler placed before fitting to check correct position. Pipework across the car fitted but the outlet to the inlet manifold proved to be a real test of brain searching. Matt has air con and the pipes get in the way. A little cutting , welding and fettling managed to get them positioned right. Now that the turbo outlet pipe had been fitted the inlet manifold fitting made sense. That was duly bolted to the engine. Whilst the engine was on the floor so to speak a new wiring loom was obtained and fitted to the engine. No way would you be able to fit one easily whilst the engine was in situ.

Now had come the time to fit the engine properly. It went in rather easily :eek:. Everything was hooked up and the split second (7th injector) was introduced to the engine. The water pipes were fitted and the radiator replaced with a new one. A call to Demon Tweaks brought forth some hoses for the turbo to inter-cooler (missing from kit).

Exhaust proved to be a real pain in the proverbial. The back pipe fitted ok ish but the front pipe we could not get on. Hours went by until it was decided to remove the engine mounting and fit the pipe. Ok job done or so we thought. Everything put back together and sit back and admire the work so far. Start the engine. Fired first time (as per usual). Behold, what is that we hear? Exhaust leak from front pipe. Engine mounting off and check joint. Straighten downpipe ring and re bolt. Engine back on mounting, restart engine. Exhaust leak :wallbash:. Ever had one of those days when all you want to do is throw your tools around? We had that day. Left car alone for a week and had some thoughts.

Ok so take the exhaust system off the car in its entirety. Examine all factory welded parts. Ahhhh there was the culprit. Cracked pipe by bell mouth. Tig welded pipe and refitted. Started engine and no leaks. Big sigh of relief.

The first drive was in the rain down the yard. Gentle acceleration to be met with wheel spin. Hmm this could be fun. Wait until dry day and put it on the road for real. 70mph and squeeze throttle pedal. Big whoosh under bonnet and I found that I was having a white knuckle ride. Matt informed and car collected.

Future plans. Bin Mercedes injectors and fit 20lb Mustang injectors (Mercedes ones are 15lb) Increase boost pressure to 0.7 bar. Fit limited slip diff.

Over to you Matt :D

I have pictures somewhere and will post them as I find them, also a vid of the con rod machining. Oh and I have no formal Mercedes Training so its bound to be wrong
"I have pictures somewhere and will post them as I find them, also a vid of the con rod machining. Oh and I have no formal Mercedes Training so its bound to be wrong"


Training or no training, you have built up a very good business and should be proud of it, you are clearly a very good "Engineer" who enjoys what you do, we all trip up over time at what we do..... you did......recovered, and picked yourself back up to create what you have today.... Hats off to you fella, you provide a top service oop norf...

Ah the joys of starting a project. Where do you stop? Traction is an issue in the damp-there is no electronic trickery to reduce power, it just needs a delicate right foot. Better rubber will help but only a little bit and I don't want to put wider wheels on and roll the arches- I want the car to remain looking stock.

Currently only on low boost (I believe Ian tested on the full fat 0.7 bar) and the power is addictive. She pulls strongly and from 3000 rpm the engine is really into its stride. A trip to Germany will have to be undertaken (hopefully no repeat of 20 years ago when I got caught doing 240km/h in a 100 zone) so I can tease much newer metal that will be surprised by its turn of pace.

Before then though the car needs suspense work so I will get round to that when I have the time.

All in I am very pleased with the work Ian has done. It all works as it should, what more could I ask for
Could one of the mods please change the title to "Mattc's Twin Turbo 104 conversion" Thank You.
How are the turbos arranged?

By that I mean does each one fed three pots or do they both feed all six? Some other way?
How are the turbos arranged?

By that I mean does each one fed three pots or do they both feed all six? Some other way?
They feed all six. Each turbo outlet feeds into the inter-cooler then one line from the inter-cooler feeds into the inlet manifold.
Ian, I know you have told me this before but if we change the injectors do we need to change the turbos too or will the injectors in themselves give extra power?

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