Turbocharged 1986 420 SEL

Has anyone out there integrated a turbocharger onto a 420 SEL?
Is there an aftermarket retrofit kit available? I see that there is room where the two exhaust manifolds join at the bottom corner of the engine. I think the plumbing can be done.

[sixto]

Turbos are generally mounted high so oil can flow down to a level above the level of oil in the sump. Twin turbos might turn out to be the easier way to go. I don't know if the firing order supports twin turbos or if it even matters.

Since it's obviously going to be an involved task, consider swapping in a late 70s M100 (6.9) or early 90s M119 (5.0). Check out this website:

http://www.mbcoupes.com/memberscars/T/satishtummala/satishtummala.htm.

Sixto
91 300SE
81 300SD

I discounted the twin turbos because I would have to modify the exhasut manifolds. I could easily [SIC] mount a single turbo on the flange were the two manifolds join enroute to the tailpipes/exhaust manifold. As for the oil, I would not rely on gravity. I need a pressurized oil line (availability/location unknown) somewhere off the engine going into the turbo and returning (possibly) to the valve cover.

[sixto]

Have you tried the performance paddock and hot rod forums?

You don't want it to drain upwards because you're putting an additional hindrance on the pressure feeding the turbo. Plus you'll coke the oil that will inevitably sit in the turbo when you turn off the engine.

There might be sufficient flow and pressure from the port where older M116/7 engines feed the mechanical oil pressure gauge.

I guess I don't know how a 420SEL exhaust system looks. In the 450SEL I used to have, the exhaust pipes didn't come together until after the transmission. The exhaust charge would be pretty cool at that point. Ideally, you want the exhaust charge right out of the head so it's packing as much energy (heat) as it can.

See if the folks at www.forcedperformance.net or www.turbochargers.com have worked on any M116/7 engines.

Sixto
91 300SE
81 300SD

[mreid]

Just some info on turbos. Unless you are going to pump the return oil from the turbo there must be 0 and that means '0' back pressure on the return line other wise you will get serious leakage past the bearings and likely bearing/seal failure.

[sixto]

Bigger might be better.

In US trim:

M116 (420SEL) 200hp
M117 (560SEL) 240hp
M100 (6.9) 250hp
M119 (500SL) 320hp

I doubt the cost/performance ratio of turbocharging your 420SEL will be better than just selling your car and buying a 560SEL... whether or not you consider resale value. An M119 would be an absolute steal based on the same ratio.

More questions for turbocharging:

- how will you get more fuel to match the airflow?
- what's the capacity of the M116 system?
- is it just a matter of installing a bigger fuel pump and FPR?
- will an M116 idle with an M117 fuel system?

- how long will the transmission last?

- will W116 or R107 exhaust manifolds fit a 420SEL?
- some early 70s engines have cats in the engine bay, might be a good
spot for turbo/s

This is fun. I'm sure a turbocharged 420 would be even more fun.

Sixto
91 300SE
81 300SD

I appreciate any comments to my project since it helps me with all the issues.

Turbo oiling: to achieve zero backpressure perhap I could run the return into the oil dipstick hole at the bottom of the engine. ( I am assuming that is where it is.)

Fuel Mods:
I believe that the electronic fuel-injection system relies on oxygen sensors in the exhaust to determine if the air-to-fuel ratio is correct. I am assuming that 420's stock fuel injection system will automatically increase the fuel flow if a turbo is added. I have been told that this will work, but am unsure whether the stock fuel pump is adequate.

Timing Mods:
I am assuming something has to be done to advance/retard the engine's timing to suit the turbo but don't know what and/or how to do it.

I am assuming that the turbo will have capability to monitor its output pressure (atm+ 6 to 8 psi boost) and will activate its internal wastegate to bypass the turbo if boost gets excessive.

[sixto]

Turbo oiling -- the oil source will be more difficult to solve than the oil return. The dipstick might be a possible location, but you wanted to put the turbo on the opposite corner of the engine.

Fuel mods -- a lot of research is required here. Not much is published on how much fuel the system can deliver. You have to make sure you don't introduce more air because the results won't be cheap to fix.

Timing mods -- If your engine has a knock sensor, you can probably leave the timing alone.

Most internal wastegates can be modified to open later but not sooner. An external wastegate can make up for that. Fortunately, air is metered after the turbo on a KE system so you don't have to worry about recirculating 'wastegated' charge.

I saw a picture of the 420 exhaust system at timevalve.com. That is one ugly precat. I agree that a turbo should take its place

Have you considered replacing your air pump with a Paxton or Vortech supercharger?

Sixto
91 300SE
81 300SD

[Richard Wooldridge]

Hi there,
I don't think you would be satisfied at all with a home-brew turbo installation. In the first place, engines that are turbocharged have fairly low compression (6 - 1 or so) so the turbo can ram more air/fuel charge into the combustion chamber to make more power. If you try to turbo your engine without changing the pistons to lower compression ones (are they even available?), all you will do is cause detonation, which will destroy your engine in short order. I have had some experience with turbocharged engines and even with adding a turbo (but only on an off-road racing vehicle), and I can say from experience that you will be sorry you ever tried it, if you do. The turbo requires an UNIMPEDED return flow to the pan for the used oil. (minimum 7/16" pipe, 1/2" is better.) The oil cools the bearing, and the return oil is quite hot. Usually turbos require a full flow on the supply side to the bearing, which is actually an aluminum bushing on most turbos - the shaft just "floats" in an oil bath. (read "larger capacity oil pump") There really isn't much of an oil seal on the exhaust side of the shaft - there is a sealing ring, but it isn't up to handling any pressure. On the intake side there is a seal, but it will blow out if the oil return is impeded. The engine's advance curve must be radically altered to allow the varying combustion pressures not to detonate - I doubt if the knock sensor setup could handle it. In my opinion, a bigger engine would be much better and last much, much longer.

Richard Wooldridge
1983 300D/4.3L V6
Etc....

The W126's don't have a knock sensor which will make the ignition side difficult. Why not look at a Euro 560SEL motor and use that as a transplant? My 560 is rated at 315hp I think.

Cheers
Matt.