Okay... I'm finally starting this thread. I assume it goes in this section even though it isn't the common lift-related posts.

So, I wanted to learn how to tune an engine and I've always been one to learn by doing. Therefore I did some looking and decided to megasquirt my 1987 jeep cherokee. There's not too much point in saying it's a Renix system seeing as it hopefully won't be much longer (although it is a great system in my opinion). I don't have too much time, so this has been slow getting going what with school and all, but I have most everything I need now, so I'm going to catch anyone who is interested up. Also, for all those who are going to post about how this isn't the best/cheapest/simplest way to get more power out of the 4.0 I invite you to read the first sentence of this paragraph again for I will be ignoring those posts.

I will begin all the following by informing you I am going into this as a complete noob... enjoy

The system I decided on was the MS II from DIYautotune.com. To save a couple hundred I got the assemble yourself version. Totally worth it. As you can see in the below pictures, they sent everything in separated baggies and had amazing instructions on the internet for assembly. I also bought the stimulator to bench test my MS II after I got it together and figure out if I screwed anything up (I think I did but more on that later). The MS II works through batch firing where I will have two banks of 3 injectors. The MS III supported sequential injection for up 8 cylinders, but I'm not looking to put my engine on a dyno and squeeze that last 1 or 2 horsepower of tuning the injectors, so the MS II at a $100-200 less was my choice.



the stimulator parts


the stimulator assembled



MS II parts



testing

Total of about 8-9 hours of soldering for assembly. But I moved from my dorm room to finishing at home as you can see in the last pic and I wasn't exactly rushing.

I'll post more later, just feel like taking a break from typing.

 

Not bad, if it helps you out in the parts dept any, the Renix used Chevy style MAP and other sensors if you need to upgrade or tune them with your injection system.

 

The megasquirt actually comes with its own MAP sensor, but yea, the versatility of sensors with megasquirt is another reason I chose it. I just need to figure what sensors I need to leave going to the stock ecu to let the auto trans continue to work fine. I want to feed it as many signals as I can, but obviously I can't share resistance based sensors (i.e. temp sensors, although I doubt the trans needs those).

 

The transmission only needs the TPS and kickdown cable.

 

I take it you're less an automotive guy, and more an electronics guy? I land somewhere in between and this is all new to me. I'm looking forward to seeing this done, I've been looking for other computer options for the Renix for a while. I love the system, but it just doesn't have that readout that I like so much.

If you don't mind shifting the trans yourself you could always get this: http://www.radesignsproducts.com/Rail.html that rail shifter eliminates the need for a tcm. freeing up the other sensors.

 

That is a SUPER tempting little dealio. I may get one before all this is said and done.

And I am actually more of an automotive guy, but I'm not afraid to work with electronics and things. I just learn as I go. And make plenty of mistakes along the way.

 

Subscribed.

 

Okay a little more info on what I've done so far. While building the board, you make a choice between two different circuits for the tach signal. You can populate both and there are jumper wires that make the selections. One is a Hall effect/optical sensor circuit and the other is a VR (variable reluctance) sensor. My plan was to use the hall effect sensor circuit and use the camshaft sensor (sync sensor). There were two reasons:

One, supposedly the hall effect circuit worked perfectly with the stimulator and it is a type of sensor where I could share the signal
Two, since it is a batch fire system, I only need to know rpms (the software can adjust for getting a cam speed and not crank speed) and not actual crank/piston position like you do for sequential

Well, I couldn't get a tach single reading when testing with the stimulator, so I switched to the other circuit. This worked perfectly. I think the hall effect circuit is bad, but I don't have an oscilloscope (or know exactly how to use one) to test the board.

All this is okay though, because the CPS is a VR sensor. So I tried to hooked it up straight in and couldn't get a signal. I also tried the cam sensor and switched different combinations of everything just trying to get a tach signal to no avail. I did find out through all this that even if I could get a signal from the CPS it wouldn't work with the software as the 4.0 has a 66-2-2-2 trigger wheel. So I recently sucked it up and bought a 36-1 trigger wheel from DIYautotune.com to eliminate that problem with the hope that I could solve the absent signal problem. I got the trigger wheel and took the CPS sensor from my parts jeep and did some testing. I took them to work and chucked up the wheel in the metal lathe and clamped the sensor to a parting tool with some very ghetto rigged wiring with jumper wires and a battery and alas... IT WORKED!! So the wheel and sensor will be mounted to the harmonic balancer.

I really wish I had taken pictures of the setup, but for some reason I always forget my phone has a camera. I may set it up again for photography reasons. maybe.

 

so far this is pretty interesting. I'm curious what gains the mega-squirt will provide. as it stands the renix system is pretty easy to work with.

 

Love this. So glad someone else is doing this first as I will be attempting this when I put my Stroker in.

So another question about the tach signal that you posted about in your other thread... I was just thinking, doesn't the distributor itself have a hall effect sensor in the bottom that you can pull a reading off of? I can't remember where I read that but I believe jeep dizzys do have a stator.

 

That's the camshaft/sync sensor that I mentioned. It was my original plan but as I said didn't work out. Mostly because I think I messed up that circuit on the MS board.

 

Well, as usual, life got busy and I haven't done too much with this lately. But here's another quick update. I purchased a trigger wheel from DIYautotune and did a quick ghetto rigged setup at work with a battery and a bunch of jumper wires where I put the trigger wheel on a lathe and clamped the TPS from my parts jeep to a parting tool and finally got an RPM signal! So, that wheel will go onto the crank and I'll have to make a bracket for the sensor. I've also cut part of the harness off my parts jeep to splice wires and make some longer with my own connections. I've also decided to take the harness for the injectors from the parts jeep also and run a separate set-up to switch between stock ECU and the MS. This has to be done because the stock ECU sends pulsed +V signals to each injector and the MS grounds out two batches of injectors with a constant +12V to each injector.

 

Thanks for the update... I am interested in seeing where this goes.

 

Why not use relays instead? Then you can seperate the two signals without interferance...

 

Boy,do you have patience.8 hours of soldering just to do MORE work & testing.

I lost interest when I saw crap hooked to that TV looking thing.I think it's called a lap top.

Seriously,I'm glad someone has the skills & drive to tackle something like this.