[Research project] ECU modifications without remap

zeWaardt · Apr 27, 2023

Good evening!

I’ve started a little research project. I want to make my SLK faster, just like how I make every car I own a bit faster

One important part of this, is ECU remapping. Tossing on a pulley to spin the supercharger faster and installing a more beefy intercooler is one thing, but you’ll be lacking fueling especially at the top of the rev range.

Unfortunately for me, there are no tuners in my area that want to work on a car this old. Also, any future modifications I make will mean going back to the tuner and paying a nice bill.

This is geared specifically towards the facelift SLK230. On the pre-facelift it was possible to replace the fuel pressure regulator on the fuel rail to help out with fueling. The post-facelift has the fuel regulator built into the fuel pump assembly. It’s still possible to modify this, but it’s a bit harder.

Having experience with ECU programming myself, I decided to look at things I can do myself. Now this will be a very slowly updating topic, but I thought I’d let you ride with me and see where things go. I’d love to mess with this car a bit more and see how far I can get.

I have previously built an Arduino based throttle body injection ECU for my old-timer Skoda. It worked using a DIY crankshaft position sensor and trigger wheel and a throttle body from a 1998 Opel Astra 1.6.

I used 5v sensors so I could easily read them using my Arduino, used a H-bridge to control the idle air motor in the throttle body and used a MOSFET to trigger the fuel injector.

It then ran using a pre-programmed map, no o2 sensor. Basically an electronic carburettor. I implemented some very basic idle learning, but the rest of the map was trail and error from modifying an existing map for a similar engine.

Now back to the Mercedes. Unfortunately getting the required stuff to remap the stock ECU myself costs a real pretty penny. I’m looking at piggyback solutions. Either through a piggyback ECU, or an Arduino based system I can develop myself.

These are the goals I’m looking to achieve:

Alter injector duty cycle when under boost to fix the leaning out that occurs when installing a bigger pulley
Keep the Mercedes ECU in full control during cruising, as the engine is running mostly atmospheric or under very light boost during these scenarios.
Alter ignition timing for a 98 octane tune.
Possibly, obtain control of the recirculation flap to stop the ECU from pulling boost.

There are different ways I can achieve this, but there are also hurdles.
The Mercedes ECU is pretty picky and pretty smart. If it detects anything is off, it will immediately throw a code and possibly throw the car into limp mode.

Let’s first look at fueling.

A common way to try to get a car to inject more fuel, is by modifying the MAF signal to the ECU. This won’t work on the Mercedes. When installing a pulley, the car is already aware of the extra air that is flowing, but due to it reverting back to a simpler base map under WOT and full boost it’s not really taking these values into account that much.

A second issue is boost cut. Above a certain voltage from the MAF sensor, the ECU will go into limp mode as it considers it an overboost situation. Therefor modifying MAF signal going into the ECU is not really viable.

Another method, and the method I want to try is modifying the injector duty cycle. When the car is going WOT and above a certain RPM, I’d like to capture the injector pulse signals coming from the ECU and post-process them. Let’s say the ECU is saying the injectors should open for 5ms every x amount of milliseconds. I want to read this signal, and apply a correction factor to it. So let’s say, I’ll add 0.5ms to it.

The actual signal going to the injectors will be 5.5ms. The ECU will be none the wiser any of this is happening. The only important bit here is only apply the correction factor during WOT and full boost, but keep the Mercedes ECU in full control during any other part of the drive.

This should hopefully keep it from registering it and adjusting the fuel trims if my theory that the car isn’t looking much at the O2 sensors during WOT is correct.

How am I going to do all of this? I’m not sure. I was thinking of using an Arduino to sniff the signal and either have it pass it through unmodified (during cruising) or pass it through with the correction factor during WOT.

Another option is to use an off-the-shelf piggyback ECU that is capable of driving the injectors. Either solution will enable me to build a new map that gets applied on top of the Mercedes stock ECU map.

One thing I don’t know yet, is whether the Mercedes is using batch fire or sequential injection when at WOT. (whether it fires all injectors at once, or controls them individually).

Many cars revert to batch fire under high load. Does anyone maybe know how the Mercedes ECU does that? If not, I’ll hook up a scope to the injectors some day.

As for timing, I have not looked into how I might achieve that.

That’s it for now, there are no doubt people smarter than me on this forum so drop your thoughts if you have any!

If in the end I can make this work, I’d like to share all the information about it so anyone can replicate it themselves.

zeWaardt · Aug 17, 2023

I've updated the diagram in post 28 with the most recent changes. This might not be a permanent, but I'm gonna use an NGK smart coil that takes easy peasy 5v low level signals from the Speeduino to spark the plugs. Later on I'll probably find a suitable coil-on-plug solution to declutter the engine bay, but this'll get the prototype moving.

Now that I know that a 45hz 12v PWM signal is all is needed to command a pre-facelift bypass valve, this will be my initial plan. I may or may not switch to a mechanical blow-off valve later if either I can't get this to work, or for coolness factor. I like mechanical things. Shoot me

I figured out the VVT in this engine is a simple on-off signal. I don't know the frequency of it, but this can be found through trial-and-error.

I feel like I got all the most important bits now to get the engine to start. Now comes the annoyance of wiring everything in without causing the car to explode creating a crater larger the Tsar bomb.

zeWaardt · Aug 22, 2023

So I've gotten most parts of the wiring loom, a (supposedly) suitable ignition coil, a bypass valve.

Now waiting on the actual ECU itself. It's still stuck in customs, hope that doesn't take weeks. Can't wait to get started!

zeWaardt · Aug 30, 2023

Woo yeah! Everything has come in today!

Since I don't have a pigtail for the pre-facelift bypass valve, this is my solution for the time being:

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I'll epoxy-fill it so the wires stay in place while I look for a proper connector.

So first order of business was trying to install the wideband oxygen sensor. Without that, tuning is essentially impossible.
So here sits the O2 sensor:

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That's pretty tight! Even after removing that heatshield there is barely any space. While I do have an O2 sensor socket, this traditional socket isn't gonna work here...

Tire Wheel Automotive tire Automotive design Tread

A quick Google search told me that you need a special tool for this. Because why would you design a car in a way that it can be serviced with existing tools? I truly despise it when they go out of their way to design something in such a way that it can only be taken apart using special tools. The original tool for this costs over a €100.

All they would have had to do is rotate the sensor 90 degrees and you would be able to use a normal socket on it.... Like how the rear O2 sensor is.

This all comes back to my experience with German cars in general, and my favourite joke (or complaint) about German cars:

Two German engineers come together.

"Hans, that looks fantastic. Great job!........ Hold up wait, you made a terrible mistake."
"Huh, what is it?"

"You accidentally made this easy to service, we gotta redesign it so it is near impossible to service and everyone who works on this will want to jump of a bridge!"

I tried using a closed-end wrench slipped over the sensor's cable and then over the sensor, but it's STUCK. Like, STUCK stuck.

Fortunately I found a clone of this tool on Amazon for a much more realistic €20 and ordered that, but I'm not positive that this is gonna get the sensor out without breaking things.
This is a rather big annoyance, but one that was to be expected. O2 sensors are simply always a pain in the behind.

The tool will likely drop in my mailbox tomorrow, that should allow me to put a big breaker bar on it. Let's see if putting some pressure on it with that breaker bar and smacking it with a hammer helps it come loose.... Or I launch the entire exhaust system into low orbit, that's also a possibility.

260DET · Aug 31, 2023

One essential quality needed when working on a Merc. A sense of humour

zeWaardt · Sep 2, 2023

Welp, gave it another go...

The tool was virtually useless. Due to the weird angle you have to work at, you end up pulling the socket sideways upon applying any real torque. I bet it works great if the sensor hasn't been in there for two decades.

So, the sensor stripped. Well scheiße.

First off, bravo Mercedes for making this stupidly complicated. I'd like to say a lot of bad words but that is generally not welcome on most forums and online servers 😅.

So, that thing is REAL stuck in there. It's always one thing completely blocking you from progressing. I need to figure out a way to get that thing out of there, otherwise I'd be better off drilling another hole in the exhaust to put the wideband sensor there while letting the original one chill where it sits.

I think I'm gonna end up taking the entire exhaust off, as there is no space to get an angle grinder in there to grind the sensor off.

Frustrating for sure!

zeWaardt · Sep 3, 2023

I’ve come up with what I’m gonna do.

I’m afraid that the bolts that hold the exhaust to the manifold will snap if I try to take the exhaust off which will instantly render the car undrivable (well, at least according to my local laws

), so I’m gonna drill a second hole in the exhaust and add a second bung so I can have both sensors installed simultaneously. With the car on jacks I’m pretty sure I’ll have enough space to maneuver my welder underneath the car.

This has the added benefit of keeping the OEM ECU happy with it’s OEM O2 sensor, which will help for my future attempt of trying to make the OEM ECU not realize it’s not actually in control of the engine and hopefully prevent check engine lights from being thrown.

I’m trying the “player 2 with controller unplugged” approach, where the OEM ECU thinks it’s doing a banger job running the engine while actually not being in control at all, keeping the OEM ECU’s emissions monitors alive and making it easier to pass smog inspection. While the OEM ECU is highly skeptical of any sensor values and will throw codes if any sensor value is even slightly off, it does not seem to check at all what’s happening on it’s outputs.

This has been what has made it possible for people to put mechanical bypass valves on this engine. With the pre-facelift ECU, it will get all pissy if you do this without doing it in a specific way but the facelift ECU just cares about the sensor values making sense. It will keep happily running the engine even in the most dire conditions. Injectors unplugged, ignition wires unplugged, all sensors unplugged except for either the crank sensor or the cam sensor, and it will continue to attempt running the engine. It will even run the engine without the crank sensor as long as the cam sensor is in place and vice versa. It’ll run like , but it’ll run

Otherwise I’d have to revert the car to stock for the inspection, solely for the fact that the ECU won’t give it the green light for emissions. The way I’m installing the Speeduino makes this an easy process (just unplug the Speeduino and plug the OEM injector and ignition cables back in) as I’m making a shared system where both ECUs read from the same sensors.

260DET · Sep 4, 2023

Thanks for the explanation, this would apply to R171's too I guess, it makes sense from a engine reliability aspect. All the talk about the impossibility of running an aftermarket ECU in conjunction with the stock ECU may be questionable then. I'd like to do that with mine rather than get a tune although I'm told that this can be done remotely What's required my end for that I do not know.

It's good to see someone on this forum doing something other than embellishments, not a popular thing to say but 😃

zeWaardt · Sep 4, 2023

260DET said:
Thanks for the explanation, this would apply to R171's too I guess, it makes sense from a engine reliability aspect. All the talk about the impossibility of running an aftermarket ECU in conjunction with the stock ECU may be questionable then. I'd like to do that with mine rather than get a tune although I'm told that this can be done remotely What's required my end for that I do not know.

The only thing that I should really clarify is that no cooperation between both ECUs is happening: The standalone ECU is fully in control of the engine and the OEM ECU kind of just exists. You could remove it entirely and the engine will still run, but you'll lose a bunch of functions such as the gauge cluster, cruise control, transmission control. That's really the only reason why we're still keeping it. We don't need it for the engine to run, rather we need it for the rest of the car to keep functioning 😜

I should also clarify, with "OEM ECU" I mean the original Mercedes-Benz ECU.

I haven't really completed anything yet, but this is essentially how it all works:

You will need a standalone ECU. I chose to use a Speeduino, but you may use a Megasquirt or whichever ECU you prefer.
You will then disconnect most outputs from the original ECU. This meaning, the injectors, the ignition system, the supercharger bypass valve and the variable valve timing solenoid.

The Speeduino will control these, and thus actually be responsible for running the engine.

The throttle body will remain connected to the original ECU. This is a safety precaution as the original ECU has many failsafes to prevent a runaway condition. This will also keep cruise control functional, and in theory (this is what I'm gonna test) also should keep the traction control and ESP alive. From my own experimentation the throttle body control of the OEM ECU will keep working under all and any circumstances, as long as the OEM ECU has power and is physically connected to the throttle body.

All the engine's original sensors will both connect to the original ECU and the Speeduino ECU. This means that both will be getting identical data.

Now you will have to tune the Speeduino ECU from scratch, you essentially have a blank slate to start with. You will need to tune the engine so it runs similarly to stock under low load and cruising conditions. The emissions monitors of the original ECU will work normally as long as all the values the original ECU sees from the sensors are within it's tolerance. This shouldn't be difficult to achieve as you would normally tune for a 14.7 to 1 air/fuel ratio under low load conditions. Since the OEM ECU uses a narrowband O2 sensor, it isn't actually able to measure the air/fuel ratio under high load, as under these high loads the air/fuel ratio will fall outside of the window the O2 sensor can measure. A narrowband sensor can only measure between approximately 14 to 1 and 15 to 1 ratios as it's solely intended to maintain 14.7 when cruising. When you step on it, the ECU will command an air/fuel ratio that is somewhere around 12 to 1, however it has no way of checking that this is actually what occurs, so it simply does not use the oxygen sensor, goes into open loop (meaning it won't be checking any emissions either) and run the engine based on some calculations it makes.

The Siemens ECU used in the facelift model is quite tolerant to changes in boost pressure, it mostly ignores it however. This is why the engine will end up running lean when installing an oversized crankshaft pulley; it simply does not have a fuel map for the increased boost pressure.

You will tune the Speeduino ECU using a wideband oxygen sensor to run safe air/fuel mixtures across the board, and do any tuning that you like to make the engine faster such as increased timing. Since it's you yourself that's tuning the Speeduino unit, you'll have to make sure you tune it safely. The original ECU can't do anything about it if you run for example too much timing advance and get severe detonation. This means that yes, you can blow up your engine if you do not know how to tune the engine. You will require the skill to tune the engine!

I aim to make fuel and ve tables available to significantly reduce the amount of skill required to make a nicely running engine, however you'll still need to know some basics so you don't blow up your engine!

As long as you tune the Speeduino ECU so that the values emitted by the sensor make sense to the original ECU, it will not complain. Since the original ECU can't actually see what the ignition timing is or what the pulse signals to the injectors are, it can't interfere with them or complain about them. It can only look at the "results": aka the O2 sensor, the MAP sensor etc.

What is important to understand is that the original Mercedes ECU is only in control of the throttle. Apart from that, it can't do anything since it's connections to the injectors, ignition system and supercharger bypass valve have been severed. It's on you to tune the ECU so that it runs the engine well enough to keep the stock ECU happy.

You will need to fool the original ECU a bit, you'll have to connect something to it's outputs. It will detect if the injector cables are unplugged (open circuit codes), so you could connect them to dummy injectors (cheap China units) or suitable resistors. The same thing goes for the ignition system, the variable valve timing solenoid if you choose to control it yourself, and the supercharger bypass valve. For the bypass valve, you could just have the original valve hang around somewhere in the engine bay with the connector connected. It'll be all flappity flapping while not connected to anything.

This is what I mean with "player 2 with controller unplugged" strategy. Just put dummy controls on the original ECU so it thinks it's actually commanding fuel injectors etc.

If you get all of this right, in theory the original ECU will not realise anything is off and throw no codes.

This is what I'll be working on, for now it's all theory and we'll see in the near future whether that theory works in practice. I also aim to produce base maps usable for anyone to start tuning their facelift R170 SLK230 however this basic theory can be applied to any car in existence.

If your car is simpler than a Mercedes, you'll likely not need to bother with this at all. Just yank the original ECU out and run only the standalone. Unfortunately we drive complex cars, so we have to be a little more considerate.

This theory will work for any car you wish to maintain the original ECU, for example if you want to retain OBD2 emissions monitoring.

260DET · Sep 5, 2023

Great explanation, it's all understandable and all makes sense. As you likely know for some cars, particularly Japanese, an extra ECU called a piggy back can be fitted while retaining the original ECU. Not sure how tuning is done but I assume that only the piggy back is relevant. I guess that if emulators were available they could be used instead of the idle original injectors et al.

The only problem that could arise is with the auto transmission not getting all the necessary inputs from the engine?

zeWaardt · Sep 5, 2023

A piggyback works way different.

A piggyback works to modify the signals to and from the engine.

For example, it modifies the value from the MAP sensor to the ECU to fool the ECU into injecting more fuel, or it offsets the crankshaft position signal a few degrees to fool the ECU into advancing the timing a bit.

The Mercedes ECU is too smart for this. It recognises when you start playing with the signals and then goes into limp mode. This is the first thing I tried, but it just doesn’t work. If you alter the VR signal from the crankshaft position sensor in any way, the ECU rejects the signal and the car will refuse to start. The ECU throwing a code for a crankshaft position sensor fault. I’m not sure how it does it, but it probably compares the waveform to what it knows it should look like, and if the waveform isn’t perfectly regenerated when it’s being modified it assumes the sensor is faulty and refuses to run the engine out of safety, as a bad crank sensor can cause severe engine damage if the ECU applies the wrong ignition timing.

Modifying the MAP or MAF sensor value will not give you much benefit as the ECU doesn’t look at them all that closely when under max boost. You also only get very little range to play with before the ECU throws a “performance/range” error for the sensor.

The reason a piggyback works on those Japanese cars, is because the ECUs in those are rather dumb compared to the Mercedes ECU and simply don’t detect the modifications to the signal. You can fool the signals all you want and the ECU will do all it’s calculations with the modified data as designed. Different numbers in = different numbers out.

Furthermore a piggyback, when it does work, gives only limited tuning ability. It will not allow you to change how the supercharger bypass valve works in the case of our engine and might not be able to give you a lot of timing control before even the dumbest ECU realises that there is a significant discrepancy between the camshaft position and the expected crankshaft position.

Therefor replacing the ECU, or tuning the original ECU is the only real option for our Mercedeses if you’re really looking to make some power. I decided to go with replacing the ECU for a standalone unit as I just couldn't figure out how to tune the original ECU. I did try to ask some tuning shops, but they all didn't want anything to do with the car. And truly, that wouldn't have been really what I wanted as that would mean I'd have to smack €300 for a new tune everytime I change something about the engine. That would rapidly exceed the costs of just putting my own standalone ECU in there. So now if I decide to go crazy in the future and install a bigger blower or even a turbo, I can do it all in-house.

Remember that we’re driving a Mercedes with a pretty smart computer system, they aren’t as easy to fool as a late nineties/early 2000’s Honda ECU.

zeWaardt · Sep 15, 2023

@Alex.M-oneeleven You might find this one interesting, I remember watching your videos about using a traditional mechanical blow-off valve.

I ordered a cheap one to play with (mostly intended to go onto another car) so I tossed it onto mine.
One of these cheap toys:

The facelift model of the car tolerates the valve quite well. It runs kinda funny at first but the ECU seems to adapt to the valve and after driving a few minutes it will play quite happily with it.
Unfortunately I learnt that the millimeter is after all just an opinion, and their millimeter is a bit smaller than my millimeter so the valve wasn't a good fit onto the piping of the SLK so I kept getting boost leaks and eventually heard a nice bonk as the valve departed the circuit and decided to smack it's head against the bottom of the hood.

I first installed it just as it came, with a vacuum line running straight to the intake. Problem that popped up is that the valve would close too soon and inconsistently causing the car to suddenly start building boost when barely touching the throttle. This would cause the engine to stumble and you could hear the supercharger surge.

I eventually installed a stronger spring and a checkvalve to prevent boost from pushing onto the diaphragm from the topside, pushing it closed prematurely. The engine played quite happily with this but it was absurdly loud. Car sounded like some JDM machine.

Here's what a blow-off sounds like with this valve:

IMG_9226

Watch "IMG_9226" on Streamable.

streamable.com

While I was happy to see the OEM ECU on the facelift car to quite quickly learn to work with the valve, it's poor fitment made it ultimately useless as I kept getting massive boost leaks. It also seems pretty tricky to get it adjusted just right that it stays completely closed under boost (and the boost pressure itself doesn't push the valve open) while also not having the valve fluctuate during low throttle.

I'd personally say it's a useless upgrade, it makes the car louder and gives very satisfying blow-off noises but it's harder to tune and really doesn't do anything for power.

I'll stick to the electronic valve! I can always adjust it to get more blow-off noises if I want to

I might play with it for giggles once I manage to get the Speeduino fitted, but the electronic valve is just nice as you can very precisely program when you want it to open and how much to open.

Alex.M-oneeleven · Sep 16, 2023

Try the valve with a manual boost controller and a small vacuum circuit, I had the same problem.

The valves all close far to fast and that is what throws off the standard ECU, I found the way to over come this was to use a manual boost controller in a small vacuum circuit, if you check out my write up of the videos I think I explain how to plumb it all together. So basically the vacuums needs to be released fast but applied slowly this can be done using two check valves and a manual boost controller.

This shows the circuit in operation..

ado81 · Sep 15, 2023

Hello
Interesting story here by zewaardt👍🏻
I have just started my upgrades to my 230k.
Last weekend I installed the pulley to the crankshaft and worked and welded an exhaust system of my own in July-august. This week I ordered a much larger intercooler also. My question here is simple. Do you, or anybody else, have a link to or recommendation for the make of the fuel pressure regularor? My model is a pre-facelift-98.

zeWaardt · Sep 15, 2023

Hey, I specifically focus on the facelift model as it's a bit different from the pre-facelift model.

The pre-facelift model is already very well documented.

I have not done any other supporting mods on my car, that's what I'm working on now. A fuel pressure regulator isn't as easily changed in the facelift model and the ECU in the facelift model seems more tolerant to changes as well, making it not as big of a deal if you don't change out the regulator.

I'm focussing on retuning instead. The purpose of the fuel pressure regulator is to get more fuel in despite the computer not ordering to inject any more. I'm changing the computer in mine so I can command the fuel injectors to inject as much fuel as I want (well, as much as they're capable of).

For your car, a fuel pressure regulator would be a good upgrade to keep your air/fuel ratios in check. I have no link to one, as that upgrade does not apply to my car. For my car it would work differently.

zeWaardt · Sep 16, 2023

That’s the fun bit, the facelift model functions totally normally after installing a single check valve and a stronger spring.

The engine was shaky at first, but the ECU rapidly adapted and then it ran fine. I can demonstrate if you wish!

The only reason the valve didn’t work for me is because of poor fitment.

I’m gonna continue using the electronic valve as I can directly control it using the Speeduino, just makes everything easier.

Alex.M-oneeleven · Sep 16, 2023

That's awesome if you can make a speeduino operate it, I don't have that level of electronic or coding skills it would be awesome if you could make a speeduino control a pre facelift valve too.

zeWaardt · Oct 3, 2023

@Alex.M-oneeleven I wasn't able to make the pre-facelift valve fit onto my facelift intake yet so I played with the mechanical valve for a bit.

It's weird.

I tried making a vacuum delay valve as you suggested, that completely fixed the running issues but with that installed the engine for some reason makes no power.
I don't have a boost gauge so I can't be sure if it's leaking boost, but I don't hear any hissing coming from the valve. It seems to close completely.

My old method of simply using a checkvalve to block airflow towards the vacuum port of the valve makes the engine run identically as with the vacuum delay valve.

If I hook it up straight with a vacuum line, the engine overboosts at low load (low rpm + low throttle) and starts misfiring but on WOT the power is fantastic, if I hook it up using the vacuum delay valve the car runs great but seems to lose a third of it's power. I tried shimming the spring for more spring tension as well (need a vice to get the thing screwed back together now) but it makes no change.

I'll hook up an electronic boost gauge from one of my other cars later to verify I'm not leaking boost. I don't hear any boost leaking from the valve. It's a pretty loud thing and even with it cracked open just a tiny bit the hissing is very very loud. It's weird. More experimentation required.

Alex.M-oneeleven · Oct 3, 2023

The vacuum set up is a very fine line with adjustment, I managed to make it work as well as the standard valve would but with no benefit other than it was not using the electronic valve.

If I remember right two check valves are required with a manual boost controller, so the key is to slow the closing of the valve, I used a butterfly valve so there was no restriction when venting as the maf was so sensitive to it. I believe the only way to make a valve work is by using a butterfly type valve as I've had no success with any other type of bypass/Bov. Basically the valve can open fast but if it closes too fast it causes bucking and misfires.

zeWaardt · Oct 3, 2023

Hmm alright.

Alex.M-oneeleven said:
Basically the valve can open fast but if it closes too fast it causes bucking and misfires.

The facelift ECU seems much more tolerant and opening and closing speed does not matter much, the only thing that makes for a problem is when the valve closes prematurely and causes overboost at low load. I seem to have the opening and closing correct right now, but when the valve closes and the engine builds boost it loses power in some way. So I have no problem with how quickly the valve snaps open or close, just at which level of vacuum it starts closing. Too little spring pressure or too much boost on the vacuum line and it starts closing too soon, causing it to close as soon as engine rpm goes above 1500rpm which makes the car start misfiring.

Seems like the ECU in this car is unhappy in a different way. I feel like I have everything set now that the valve remains open when it should remain open, and closes when it should close however the engine is not allowed to get maximum power.

I don't know how the pre-facelift valve operates, but the facelift valve only actions between 90% closed and 100% closed really. When you let off the throttle, the butterfly valve never opens more than just a tiny bit so there is always significant restriction when venting. The only time the valve opens more than just a crack is when there is a malfunction and the car goes into limp mode. Then the valve opens all the way. The valve also actions very quickly. If you step on it, it snaps close in milliseconds and when you let off it snaps open again in milliseconds. I attached a scope to one of the potentiometer outputs to figure out how this valve likes to work.

The facelift bypass valve weirdly enough looks like it's an identical component to the throttle body; it looks the exact same and even has the same connector.

The facelift car also has a MAP sensor. While it still has a MAF sensor, I found out through experimentation that the MAP sensor is more important to how the car runs than the MAF sensor. Unplug the MAF sensor and the car runs basically fine, unplug the MAP sensor and it can't work out the air/fuel ratios correctly anymore. There is no noticeable difference in how the car runs when you unplug the MAF sensor.

When I have the time tomorrow I'll take the boost gauge I have from another car and put it on this one to see if it really is building boost properly, or whether it's losing the boost somewhere. When you step on the throttle, you initially get a nice throttle response but then it just goes bland and the engine feels weird, sounds different and becomes very lazy. As if it's restricting power, though no limp mode is triggered. The engine also doesn't misfire or buck at all, it runs 100% smooth. It just makes no power. It's faster than when it's running atmospheric, but it feels like it's being held back.

MattHam · Oct 13, 2023

hello, are you able to detail how you plum in the boost garage as this is something I’ve been interested in for ages but not sure how/where to plug in the vacuum line! Thanks

zeWaardt · Oct 13, 2023

I split off the vacuum line from what I think is the evap canister.

It has a check valve (one-way-valve), I put a line from the intake manifold to a t-piece, then end #2 goes to my electronic boost gauge, and end #3 goes to the evap canister with the check-valve placed in between.

There are other lines you can tap into, but this one was easy to reach. Not sure if it's the best one, but it seems to do the job for me.

Due to busy work life and health issues I haven't had much time to continue testing the mechanical bypass valve yet, that's still underway.

zeWaardt · Oct 25, 2023

Unfortunately I've had a bit of a slowdown with the car, it's developed some issues which I think I can thank to it's high mileage (it does have almost 380k km after all). It's temporarily off the road and I'll have to repair it. It had some issues in the pipeline needing to be fixed, but last week it broke down on me and I've decided to take it off the road for a while as it's not really reliable to drive right now.

It'll be back on the road before the end of the year hopefully. Gonna take all those little things that have been bugging me for a while and just get 'm all done in one go.

zeWaardt · Nov 16, 2023

Well.... I'm sorry guys, it looks like this got cut short before I was able to finish it.

Wheel Tire Automotive parking light Car Land vehicle

As it was parked on the side of the road, someone crashed into it and sent it barrelling into my daily driver (the red car).
The Mercedes is totalled, the MG5 will probably be in the repairshop for a while.

Of course just after I fixed the leaky radiator hoses, MAF sensor, camshaft sensor, shift linkage and some interior bits.

I'm at a loss for words really... RIP.

[Research project] ECU modifications without remap

IMG_9226

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