Hello everyone,

I have been reading through a lot of threads about the Megasquirt but I still have some questions left over about it. I have assembled a megasquirt (v3) in the past, but never installed on into a car myself. At the moment I am looking at saving some time and buying the prebuilt 3.57 here:

http://www.diyautotune.com/catalog/m...ase-p-171.html

I see in the FAQ that you need to build a conditioning circuit for the CAS, make modifications to the LED, and IAT bias resistor in order for the MS to be ready to run on the 13b. Since the 3.57 board is surface mounted and looking at the picture of the board from the website I posted I am left wondering how I would be able to make these modifications on this unit?

Next thing, I assumed that all the modifications I posted above are in order to use all the stock components on my current engine, is there anything I am missing out that will need to get replaced with GM sensors (such as TPS, Boost Sensor "MAP", ect..) that you guys can point out to me? Also wondering if I do need to use a GM full range TPS, how you guys mounted the guy on the engine (also applies to other sensors I might need).

Finally, the reason I am going with the 3.57 is because I have read that it requires less modifications for different components, is there any reason I should not get the 3.57 and just go with the v3?

I think these are all the questions I have at the moment. Thanks.

 

Why not just buy an assembled V3? The 3.57 really shines when it doesn't need any modification. For example, running a 60-2 with wasted spark on a 4 cylinder. We have to modify so much to run the rotary that the surface mount board would just be an unnecessary pain in the butt.

You can use your S5 TPS as it is a full range pot on it. Even the narrow range bit will work but it will make setting up the accelerator pump a bit annoying. If you use the GM coolant and air temp sensors then you don't need to swap bias resistors.

 

Ok, I figured when I read here somewhere where it says it says the 3.57 doesn't require modifications for certain functions, that it meant it would apply to rotary engines also (I was hoping this would simplify things).

So besides the coolant and air temp sensors I can pretty much just use everything else I have correct? If I do modify the V3 board for the stock IAT sensor (swapping the bias resistor like the FAQ states) is there also something else I need to modify for the coolant temp sensor? I didn't see anything about that in the FAQ.

 

The v3.57 doesn't require pullup resistors (they're built-in I believe), and doesn't require anything special for the idle valve anymore. But it does still require that you run a few wires back to the db37 from the LEDs (there are now jumper holes for those, no more soldering to the - lead of the LED). You have to have an lm1815 board as well with the 3.57, as it has no proto area.

IMO it is easier to make a 3.57 board work, but it costs considerably more.

For what it's worth, my PnP units are all 3.57 boards now.

Ken

 

Do you sell PnP units that run off the 3.57?

 

Yes.

I still recommend doing your own harness though. The harnesses on most rx7's are very worn and fragile.

Ken

 

Ok, I will PM you when I am ready to get that, I was planning on using the generic megasquirt harness that diyautotune sells I have already seen how crispy my current harness is : )Thanks!

 

I also recommend building or modding your own MS. You'll learn how it's done, so if something breaks, you're capable of fixing it.

Ken