Mega squirt.... Talk to me

[si.]

I'm crap with electronics for a start so I need a 'dummies guide'

This is a budget build always has been but if I can't sort out the engine that I have to a more usable drive able state I may have to blow the budget and start saving for a proper engine and ecu setup

My current set up consists of

M20b25 high comp engine but now with .2mm head gasket
Vernier pulley for valve clearance due to cam same with thicker HG
300deg cam with a very long duration
6 branch header
2 1/4" exhaust

Due to the cam this runs incredibly lumpy at idle but high revs it's sings and shifts along nicely

Is mega squirt something that can be used to get the best out of this and if so how, and what do I need to do

If it can would it then also be able to cope with itb's as this would be my next step with this set up??

Thanks in advance

[steed]

The 300 Deg cam will limit any engines ability to have a smooth idle. with a mega squit it might be able to make it slightly less lumpy but i doubt it would eliminate it.

On the ITB front, yes megasquirt would be able to handle this, altough it may take a bit of fettling. There is a decent megasquirt setup on a standard(ish) E12, see here: http://www.bmwe21.net/forum/viewtopic.php?f=3&t=21955

[si.]

I know it will never be a smooth idle just want to make it all work a bit better/get the best out of it

I'll have a look at that thread

[Jeroen]

Bertje is doing a great job there, knows what he's doing

[BertjeConti]

Megasquirt is a option, but not an easy route to go.

Everything in megasquirt is tunable, so for a tuned engine it is a good option to get the most/best out of it.

There are a lot of complete megasquirt diy kits available, but wiring is alway difficult. check http://www.msextra.com/

If i was you i would get my hands on a second engine bay wiring loom and use that to build your new megasquirt wiring loom. Never cut your original wiring loom, so going back to motronic is always a possible option.

You'll definitely need to change the TPS sensor, because the stock TPS only gives only a contact closed and wide opened throttle. Megasquirt needs a TPS sensor that reades all throttle positions.

MAP sensor (manifolt air pressure) on the stock intake manifolt is a perfect solution (and you can ditch the air mass meter, which is restricting the air flow), and the megasquirt can drive the auxilary air valve for a decent idle at all circumstances (during the warming up), with ITB's this isn't possible !

ITB's and a MAP sensor (manifolt air pressure) is difficult, because there isn't a decent intake manifolt with constant pressure. I know there are solutions with a canister and vacuum connections to each ITB, like this:

Google "ITB MAP"

But i've read that megasquirt has a "ITB Mode", in this mode not only the MAP is used to determine the correct VE, but alse the TPS plays a role in this.
Search the MSExtra forum for "ITB mode".

Another thing to take in mind is a wide band O2 sensor, with a wide band O2 sensor Megasquirt gives opportunities for auto tuning. check the tunerstudio pages for that.

Megasquirt gives a lot of tuning possibilities to get a decent idle.

first thing to do is read a lot on the internet....

[BertjeConti]

Bertje is doing a great job there, knows what he's doing

"Bertje" is another E21fan here, but i think Jeroen means "BertjeConti"

[Jeroen]

I sure meant you, and with your MegaSquirt thread already linked I reckoned he would be able to find you haha!

[si.]

Been doing lots of reading and my brain is starting to implode...... But im gradually getting there

Ill get hold hold of another m20b25 loom and start looking into exactly where i need to start

Im definatly going to go down the itb route hopefully with a set from RHD Engineering in Australia

[Bullet Ride]

It's not necessary to get another wiring harness if you buy a plug and play unit. I have built the DIYPNP kits for two M20 powered E30's (one turbo and the other a 2.8 stroker with ITBs) you can build a kit up leisurely over a weekend and they have base maps on their website that'll get your car up and running.
https://www.diyautotune.com/catalog/index.php
https://www.diyautotune.com/diypnp/apps ... 25-mt.html

[si.]

Cool, i take it that you mean an off the shelf pre built ecu and loom, basically the more i can do myself hopefully the less it will cost which is a must

Im still saving atm aswell the itb kit is going to cost about a grand, but im hoping to pick up some of the smaller parts along the way

[Bullet Ride]

Assuming that your car has the Bosch 55 pin plug for the ECU... then all you need to do is plug it into the box and run a vacuum line for the MAP sensor and you're up and running. To eliminate the AFM you'll need an IAT sensor, but even that doesn't require modifying the wiring loom, you can just push spade connectors into the AFM plug. Putting in a wideband O2 sensor is the only part of the install that requires cutting and splicing into the factory loom.

You can either buy a PnP unit which is pre-built, or buy the DIYPNP unit which requires you to assemble it. Both plug straight into the factory loom..