What are the specific problems with the Crossfire that makes it resistant to accepting a turbo kit? Many have mentioned the ECU...I would like to have specific reasons for what needs to be resolved within the ECU to make the turbo kit work properly. I have a company who says they can turbo my car and give it 400 rwhp on a single turbo, plus get it done in roughly 3 weeks, for $6,000 - $7,000. I would like this thread to focus on highly specific problems with making the Crossfire work with a turbo. Please feel free to use technical jargon. The goal is to be able to show this thread to my builders to show them that this car is a beast to tune. I have consistently warned the company that this vehicle is not easy to work with, but they are not worried because they mentioned they would be using a stand-alone unit. I don't know anything about ECU stuff, but the builders do. Thanks.

 

Simple. Turbos require more fuel and require major engine timing adjustments. Nobody that I have found has the source code for the ECU to adjust the timing or the FMU to subsequently adjust the Fuel/Air ratio except for Kleeman, Renntech & Carlsson.

IMO the only way they will be able to get your engine to run at all with the installation of a turbo is to gain access to this software or rig a piggyback system.

If these guys have never worked with a Mercedes engine electronics, they're going to have one hell of a time...

 

Thanks HDDP...I knew you were going to be the first one to answer this post. You answered my question just the way it should have been answered. If anyone else has something else to add, PLEASE feel free to add on.

 

Well your also gonna have some issues mounting the turbo and fabbing up new headers and exhaust system.

Also 400 hp on the N/A motor might be pushing the limits of the crankshaft, connecting rods, C/R most definitely will have to be lowered, and the rear axles might have to be swapped for the SRT6 axles. Not sure how much power the Limited axles can take before a CV joint fails?

I think your bill at the end of the conversion will come close to $10,000.

 

They definitely would need to piggyback a fuel controller or use the separate stand alone computer to control the engine.
The problem with the stand alone is that the transmission and shifter computers talk to the engine computer. So does the ESP.
See any red flags yet?
By what my techs tell me, the computer on a naturally aspirated car doesn't really care about intake air pressure (or density). It simply measures the volume of air going into the engine.
The computer does not know what to do with extra air so it's not going to give you more fuel. Detonation will kick in and the computer will take all the fun away before you get the chance to scatter the engine all over the road.
The piggyback controller will have to force more fuel into the engine to make up for the extra air. There are a few different crude ways to do this but the best is a true computer controlled setup.

 

That's not strictly true, the system has to take density into account. It is the mass of air entering the engine that is measured not the volume in order to inject the correct mass of fuel. The system can also compensate for a certain level of additional airflow, but no where near enough to allow for turbo charging.

 

pretty much what feets said.

as far as dynamics statement -- the intake manifolds should be plenty sufficient for a turbo -- as far as what i've heard, the rear end, crankshaft, and connecting rods, of this car are setup to handle 450 rwhp *believe someone said that was a response from kleeman, brabus, or startech* as dynamics said c/r would def need to be lowered.

 

Woody, these engines have an air flow meter but I didn't see a manifold pressure sensor when I was looking through the engine electronics at work today. They're only on the supercharged engines by what I can tell.
There may be a barometric pressure sensor mounted in the engine compartment. That would not measure engine vacuum.
The air flow meter will measure air movement only, not density. It's nothing more than a heated wire with known resistance values. The faster the air moves across it, the more it cools off. That changes the resistance and the computer responds accordingly.
Low throttle opening and low air movement equals reduced fuel. High throttle opening means increasing air flow and more fuel.
*** Maybe that will make sense to those not familiar with engine electronics.

JP... boost is a fickle mistress. You can super/turbo charge a high compression engine. It will make good power but the boost must be tightly controlled to avoid detonation and the previously mentioned engine scattering event. I'm sure a properly done setup could take 6 or 8 psi but intercooling would be necessary above that.
The flip side of boost is that you can double the output of a motor and only increase the peak internal stress by 20% to 25%. This is because the compressed air charge takes longer to burn than the looser less dense air charge. The pressure peak is a wee bit higher but the power comes from the longer burn. That big fat slug of boost will push a little harder at it's peak force but will still be applying more pressure as the piston moves. 90 degrees of crankshaft rotation will see a naturally aspirated motor dropping to 15% or 20% of it's peak pressure while a super/turbo charged engine will still be at 60% or more of it's peak pressure. It only pushes a little harder on the piston but it pushes hard longer than nature does. That makes power.

Most hot rod engines fail from high rpm. Internal engine stress goes up astronomically as engine speeds increase. The lightweight piston puts a couple hundred pounds of force on the connecting rod at low rpm but that can increase to a rod-stretching 3,000+ lbs of force near redline. That's like having another Crossfire hanging from the end of each connecting rod.
The force increase is a factor of a square. Double the RPM and the force quadruples.

These bottom ends are plenty stout. As long as the maximum rpm doesn't change then you should be fine with moderate boost.
If you do something that causes detonation, you'll shatter the pistons, break rings, and very possibly fail the engine in a John Force manner. Our engines have detonation sensors but don't rely on that to save your bacon.

I use a detonation sensor on my hot rod. If that big 440 starts to rattle under boost, the computer yanks the timing out right now to save the motor. I've ruined a set of pistons, damaged a very beefy cylinder block, and destroyed a cast iron cylinder head because of detonation.
It's not pretty. That one cost me $2,800 but only because I could score a new motor at the salvage yard for $150. Do that to your Crossfire and you're gonna be out a BUNCH more than that.

 

i don't think anyone here is planning on anymore than 7 psi. i know i haven't been, if so and assuming they can get a turbo on this mb engine i am sure they know the compression must be lowered *even i knew that* ... but all those percents make me realize why i always decide to keep my vehicles naturally aspirated.

 

What happened to that one guy who said he was gonna put out a whole twin turbo kit together for us? I guess he figured it couldn't be done for $2,500 and gave up, he still hasn't posted any pictures of the car he claims to have completed.

I think for the money it's gonna cost to do the whole turbo thing, you might as well drop in a 5L benz motor and leave it normally aspirated, imagine the big torque of that monster, and reliability too!! it's the best of both worlds! why **** around?

Big donk!

 

I think you probably misunderstood my point. Yes, the system's primary method of metering is the airflow meter but that is taking density into account by measuring the mass of air passed, not just the volume - you can have a massive volume of air that has low mass which will require less fuel than a smaller volume of higher mass. Combined with the MAF is the IAT which is further compensating for density due to temperature.

The N/A cars do have a MAP sensor (see the pic of mine below) for determining engine load since throttle position is not necessarily an indication of airflow. At low revs you can open the throttle wide open but you won't have high airflow but you will have low MAP indicating high load. Similarly at cruising speed you may have moderate airflow but a small throttle opening and higher MAP indicating a low load condition. This is more important for ignition advance control than fuelling but the ECU does take it into account.

The map is the device with the green writing on it.

 

It certainly does appear to have a MAP. I just looked at the applications again (gotta love working Saturdays) and it shows the MAP only applicable to the 112.960 and 112.961 engines. Those are the supercharged motors used in the SLK32. The N/A SLK320 motor is the 112.947.
Either MB has overlooked another error in the catalog or there's another change in the engines.

*** did I mention that it's a rainy Saturday so we're twiddling our thumbs?
I dug through the engine harness for the 112.947 motor and found a wiring connector for the MAP. I guess I know where the problem is.

 

Good to hear you are putting the 'thumb twiddling time' to good use.

Yeah, the MB/DCX documentation does have some anomalies. I have found several connector pin-out annotations to be wrong in the service manual. Its not really a problem for techs just swapping out components but a real pain when you are trying to tap into specific signal pins to check waveforms etc. I think HDDP has also had issues with incorrect part numbers on the SRT brakes.

 

As one of the chip guys posted earlier, many times people modify the Mass sensor to trim the fuel at a particular gm/sec reading, I haven't looked to see if the Crossfire is voltage driven per gm/sec or frequency driven like the corvettes...

My supercharged lt4 396 vette is making in excess of 600 hp at the crank: www.ndneyes.com/mo
I've also tossed around the thought of a centrifugal on my crossfire. Many corvette owners do run up to 8 pounds of boost (even with 10.5 :1 CR) with a centrifugal using a msd ignition that can retard the timing up to 15 degrees at WOT. They either add larger injectors and fuel pumps to allow the ECM to increase fuel as needed with a FMU or a boost a pump to bump up the fuel pressure under boost... As posted before as well you need to watch your AFR but you could monitor that with a PLX 300 - 500 wideband O2 sensors. Also using water methanol injection to cool the intake charge dramatically reduces the extra fuel that is sometimes needed for cooling to keep the engine from detonating...

Just some thoughts any ways...

Hope this helps,

mo