# Megasquirting a 2001 MK4 Golf



## T3Bunny (Mar 30, 2005)

This will be an exploration thread to begin with. I have lived with a Megasquirted 2.0 ABA for over ten years now. I ABSOLUTELY LOVE IT! So I am exploring the 2.0 idea first. 

I might have a 1.8t avalible for "free" if I want it. Only small problem is, it is in an Audi A4. The amount of effort and additional parts to make it work, might not be worth it. And I do love the "you shouldn't do that" underdog projects. Still, the 1.8T is a very viable option if it would only require me getting stuff like the DP and intake from a MK4. Over many years of owning (and working on) boosted cars I have discovered the weak points of DIY turbo systems is usally the downpipe... If the 1.8t becaomes a free or almost free choice, it is likely going to win. 

I had so many more questions as I started writing this out, but I finally had a moment of Googling clarity and decided to search for "Megasquirting MK4 Golf" and suddely was finding all the answers. In fact, the threads were in this forum, so I moved and changed this post to go here instead of the MK4 forum. 

I hear lots of talk about coding out and deleting things. Is there a good source thread where this is discussed in more detail? And can an engine ECU basically be coded to be "dumb"? By that I mean just how much can you code out of it? Lets explain my background thoughts on this... 

So what I think I am wanting to do it to retain most of the emmissions controls via the stock ECU, but give control of fueling and spark over to a MS3. And code out anything that doing so (after it is properly tuned) would cause this lack of fuel/spark control to set codes for. IE delete things like long term trim codes butperhaps retain codes like missfire detection. 

My car is DBW, so that means it is a CAN networked system, yes? It seems that the DBW module is seperate from the engine ECU. Obviously, I want to retain this function. 

I will likely have some more questions, but I have ideas now where to look so we will start with these.


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## need_a_VR6 (May 19, 1999)

The actual answer to this is quite long, but...

A parallel install with the ms handling the fuel, ignition, boost etc is possible. Leave the stock ecm for dbw and obd. You need to do a lot to the stock ecu for it to be “happy” after the parallel install. I will not share details of that but it can be done. The stock 1.8t ecu is pretty powerful and of you understand it enough to make it “happy” for obd you can probably tune it like standalone (although not as flexible).


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## T3Bunny (Mar 30, 2005)

Paul, are "happy" conversations frowned upon here like they are in the MS forums? Obviously I plan on a lift kit, putting 36" tires on the car and never driving it on the streets again, obviously... :laugh: I would realy like to hear your thoughts on this, let me know if I need to call you? 

While I don't "need" to (living in FLorida), I like the challenge and kinda want to retain as much as possible of the emmissions stuff on it. 

Actualy, I found a couple threads you were posting up information in on here and that is when the peices started to make sense to me. I am super comfortabel tuning MS and have all the tools to do so. 

If I put the 1.8t in, the stock ecu almost makes more sense. If I stick with the 2.0 already in there, I need something tunable. Since I have a MS3 with all bells and whistles and can wire up a car for MS in my sleep plus know the platform inside and out (although you have me beat as I am certain you actualy do tune MS cars while your asleep lol) it is a lot of win for running MS.


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## need_a_VR6 (May 19, 1999)

Any conversations on the stock ecu topic will have to go elsewhere. Mostly because my business is offroad use only so no reason to fool w obd


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## T3Bunny (Mar 30, 2005)

[video]https://youtu.be/34ag4nkSh7Q?t=6s[/video]

Well, I will drop you a text or call sometime to pick your brain on the MS side of things. I am pretty sure I will have a few questions there before this is all over! Your posts in other threads again were what convinced me this could be much easier than I thought to pull off. In fact, I am going to put a couple links up here while I have them open to save for future referance.

MK4 Megasquirt Questions

VW MK4 2.0L Sequential Setup

Let me ask some specific questions right now though.

1) Since I have a late 2000 DBW car, it is a CAN networked car correct?

2) If so, can I network the MS in so that it "CAN" :sly: grab the information from the stock ECU like coolant, iat, and O2 readings? I think the 02 sensors are already widebands in this car (I need to verify this). This would make it a super simple hardware hack/install. 

3) Again if it is CAN, what else can be grabbed over the network? I have not messed with this aspect of MS3 yet and find it pretty interesting. I also plan on gettign the Perfect Tuning CAN gauge sometime soon, that thing is epic!


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## need_a_VR6 (May 19, 1999)

The ms side is simple imo

1) yes

2) maybe but I have never heard of anyone doing that, not sure all the info you want is on can or able to use remote can info for data, like clt/iat is hardcoded inputs in ms, but generic sensors can come over can

3) you can grab anything there if you know the can id, i have done mk4 but only as a can broadcast to the cluster


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## T3Bunny (Mar 30, 2005)

Paul, I have more questions! 

I DID NOT go with the 1.8t setup, I stuck with the 2.0. I love the 8v motors and already have all the go fast goodies to bolt right into and onto this engine. I just finished swapping the engine and transmission from a manual donor car, into an auto shell. I got the worst of the stuff swapped over, but I have hit some roadblocks now that using the MS would potentially solve. While these questions aren't all directly MS related, they influence my decisions as to how far to go and in what direction. 

Okay first off the car in question is a 2001 Golf with the AVH engine. I now understand this is basically an AEG motor, with the DBW (drive by wire). So yes as need_a_vr6 stated it is a CAN car. I mention this again as stated above due to the CAN opening up some very interesting possibilities for gauges and data into the cluster or into a CAN gauge like that Perfect Tuning one. I would LOVE to send this info into the cluster, but at the moment I do not have the right cluster to do so. Not an expensive issue to solve though.

1) Does the DBW even need to be retained for anything on this car? 

I have an AEG throttle body, would need cable and pedal assembly, not a big deal. Probably simpler than finding the 0-5v signal the MS needs. This is a base model and as such does not appear to have any traction control other than the basic ABS functions. If disabling DBW kills my ABS, then that is a problem I have to solve.

2) If I have a dead ABS from disabling the DBW, is this a simple swap in the ABS module from the AEG car? 

I doubt it, nothing on these cars is "simple" swap in of parts it seems. But it would be nice... 

3) Other than to retain a pretense of control over emissions stuff and OBD, do I actually need the stock engine ECU for anything else? 

While a parallel install isn't the hardest thing to do, I am leaning towards a simpler full on MS install. A parallel install really only works if I leave the stock harness in place, and gut a spare ECU and harness (that I already have from the swap). 

It looks like I have to eliminate SAI and EGR anyways, once I change the exhaust manifold. This barely leaves any need for the stock ECU, unless it has to be there to broadcast/interperite the other modules? 

4) You mentioned broadcasting to the MK4 cluster. There are some interesting CAN gauges for the MK4 clusters. Is it a pretty simple matter to get one of these seeing the MS3 data? 

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I am at a "stuck in the mud point" with this car. I got everything sorted out and swapped except the interior auto to manual wiring. At this point if I have to pull the dashes to swap over the last little bit, I may need to farm it out, or just dump the cars. I am running out of time and patience. More importantly, motivation.

The part that is messing with me is the clutch pedal switches, especially the one that goes into the cluster. WHY does it go into the cluster?! It is for the engine ECU... Anyways, hoping that looking forward to the MS install will get me the motivation needed to push through this little issue.


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