MegaSquirt I v2.2 questions

[jordan]

I have just purchased the MegaSquirt I Programmable EFI pcb 2.2 kit http://www.diyautotune.com/catalog/m...bled-p-28.html and from my reading I am seeing certain things that I may need as an add on for it to work properly with 4 low impedance injectors and that is the megasquirt flyback board kit http://www.diyautotune.com/catalog/m...ecus-p-44.html is this entirely necessary?
They also suggest purchasing the megasquirt stimulator which of my understanding tests certain systems of the ecu as you go. Which I don't see why just the computer wouldn't be sufficient.
http://www.diyautotune.com/catalog/m...bled-p-30.html
are there any options of different throttle bodys that bolt on? would there be a major advantage to changing the TB?
For a relatively stock engine will the megasquirt offer the possibility of more power than the stock ecu would?
What would be a good wide band o2 sensor to go to?

[markandson]

If I understand the system correctly the stimulator/simulator generates signals as tho the unit was installed on a running engine so that you can see what you get on the computer that is attached to the system for programing purposes.

[RallyBob]

I have just purchased the MegaSquirt I Programmable EFI pcb 2.2 kit http://www.diyautotune.com/catalog/m...bled-p-28.html and from my reading I am seeing certain things that I may need as an add on for it to work properly with 4 low impedance injectors and that is the megasquirt flyback board kit http://www.diyautotune.com/catalog/m...ecus-p-44.html is this entirely necessary?
They also suggest purchasing the megasquirt stimulator which of my understanding tests certain systems of the ecu as you go. Which I don't see why just the computer wouldn't be sufficient.
http://www.diyautotune.com/catalog/m...bled-p-30.html
are there any options of different throttle bodys that bolt on? would there be a major advantage to changing the TB?
For a relatively stock engine will the megasquirt offer the possibility of more power than the stock ecu would?
What would be a good wide band o2 sensor to go to?

I believe you will need the flyback board kit for the Opel's low impedence injectors. I don't believe this is the case with the later units (Megasquirt 2 V3.0).

As far as the TB, you need a TPS for sure....Opel 1.9 EFI does NOT use a TPS at all, it uses a full-throttle enrichment switch (it's either on or off). So you either need to grab a TPS off a junkyard vehicle and graft it onto the Opel TB, or adapt another TB from another engine to the Opel intake manifold. I think the latter is almost an easier option.

I've mentioned it many times before that the 1991-1994 Nissan SR20DE throttle body is 5 mm larger, and is the same bolt pattern as the Opel's. You need to remove the 6mm studs on the Opel intake, drill them out and tap them for 8mm bolts, and then bolt the Nissan TB in place. Very simple swap.

Bob

[jordan]

Could the o2 sensor boss and wiring from the same nissan be used just to keep parts from many different cars to a minimum?

[Lasse H]

They also suggest purchasing the megasquirt stimulator which of my understanding tests certain systems of the ecu as you go. Which I don't see why just the computer wouldn't be sufficient.

Idea of Stimulator is saving (lots of) frustrating debugging time if (or when ) something goes wrong during the assembly of ECU. Of course one could try to manage without one, but at least I wouldn't dare as I've noticed it is surprisingly difficult to build even a simple electronic device without screwing up at least a little bit. (Or maybe it is just me... ) For example a solid state components can also get damaged by static electricity or overheating while soldering. It would not be nice (nor maybe even safe) to notice this if trying ECU first time with a real engine.

What would be a good wide band o2 sensor to go to?

I can't answer this, but just wanted to ask are you going to use it with this Megasquirt or what? I'm quite sure 2.2 doesn't support a wide band sensor. Wide band sensor needs quite a lot extra electronics to take care of it. Bowling & Grippo have designed Precision Wideband Controller which should do the trick AFAIK.

[Hiro]

I'm working on Megasquirt 2.2 right at the moment:
Test fits are OK on a stock 24E or a race 25E CIH,
Now I have to go for some road tests.
I purchased the ECU & relay board already assembled,
Temp probes are GM,
TPS is from a Omega 24E,
Injectors are either the std grey of yellow stuffs for a start.
I will use Megasquirt only for racing,
So no EGO sensor plugged nor MPG issue.
I think the first task is to choose a proper ReqFuel value & VE table,
Looks like the real tuning job is beyond.
Hiro

[RallyBob]

Could the o2 sensor boss and wiring from the same nissan be used just to keep parts from many different cars to a minimum?

The O2 boss on the Nissan is part of the exhaust manifold (iron). Are you trying to use the O2 for mileage or for tuning? Do you want to use an external wideband meter for dyno use, or for part-throttle tuning to stay stoic? At WOT the O2 is out of the equation, and AFIIK the Megasquirt-I can't use it anyway.

[spdkilz02]

The O2 boss on the Nissan is part of the exhaust manifold (iron). Are you trying to use the O2 for mileage or for tuning? Do you want to use an external wideband meter for dyno use, or for part-throttle tuning to stay stoic? At WOT the O2 is out of the equation, and AFIIK the Megasquirt-I can't use it anyway.

yea bob ur right on that one, the MS I cant use a wideband O2.

if you want to use that get the Megasquirt N Spark II

[jordan]

I was under the impression that the megasquirt I 2.2 utalized a wide band o2 sensor to replace the MAFS or does it get replaced with a narrow band o2 sensor, or something else all together?

[RallyBob]

Wideband is used for economy purposes, basically to try to hit 14.7:1 air fuel while cruising. Full throttle loading is a matter of tuning...the owner sets up the maps.

The primary inputs for the Megasquirt ECU are the TPS (throttle position sensor), air temp sensor, and the MAP (manifold absolute pressure) sensor. There's no air flow meter or mass air flow sensor involved at all in any of the Megasquirt systems. Those are used by the OEM manufacturers only.

[Hiro]

Some short update of Megasquirt 2.2 on my cars:

With my stock 24E (yellow injectors & std fuel pressure):
The VE table was generated using Opel output data/rpm & 24 Hg idle vaccum,
The calculated ReqFuel is high (about 24ms) but 22ms also works OK,
No problem to start the engine,
Warm-up & idle are OK without changing anything,
Revs nicely from idle to about 6000rpm.

With my race 25E (grey injectors & 3.5bar fuel pressure):
The starting VE table was generated with 160hp @ 6500rpm & 145lb.ft @ 4500rpm & 10 Hg idle vaccum,
The calculated ReqFuel (22ms) is too rich further lowered to 20ms is better,
No problem to start the engine,
Warm-up & idle are OK without changing anything.

Everything was OK from 2500 to about 5000rpm,
Then I wanted to rev higher at race levels (6500-7000rpm) but the engine suddenly starved & finally stopped.
Works OK again if the PW time threshold is changed from 1ms to 8ms which is unsane with low impedance injectors.

Opened the ECU & found transistor Q1 (TIP42C) burned,
So of course the injector output current is not nominal.
Will replace TIP42C & probably add resistors to the grey injectors to solve this problem.
Hiro

[markandson]

This is exactly why I haven't pulled the trigger yet to buy mine, I am still in need of some serious education . Besides the fact that I don't have an engine for it yet

[Hiro]

Road test today on a stock 20E CIH with yellow LE Jetronic injectors:
Megasquirt still works OK with the burned transistor,
Not used with the high impedance yellow injectors.
Fitting on the car very easy,
Starting & warming up no problem,
But the initial VE table computed for the 20E results in a very rough idle (much too lean).
Switched to VE table computed for stock 24E with ReqFuel 22 to 24ms,
Then no problem and had fun tuning/driving the car,
No lambda meter but plugs are nicely deep brown.
Hiro

[RallyBob]

Hiro, it sounds like you may have just maxed out the stock low impedence injectors on your race engine. Not enough fuel volume to feed that engine, so at 100% injector duty cycle you fried the resistors! Have you tried fitting larger aftermarket injectors yet? Perhaps try some of the low imp. Bosch '036' blue injectors, there's enough fuel for your engine (380 cc's).

Bob

[Hiro]

Hiro, it sounds like you may have just maxed out the stock low impedence injectors on your race engine. Not enough fuel volume to feed that engine, so at 100% injector duty cycle you fried the resistors! Have you tried fitting larger aftermarket injectors yet? Perhaps try some of the low imp. Bosch '036' blue injectors, there's enough fuel for your engine (380 cc's).

Bob

Hi Bob,
Yes I think you are right!
My old habit is to change only one thing at the time,
So I wanted to try Megasquirt first with my previous setup on the 2.5CIH,
Then upgrade the grey injectors for my others sets (250 to 350cc/mn).
Today I ordered the flyback board & some replacement TIP42C to solder,
But the grey injectors are the only low impedance stuffs I have now,
So let's say it's just to have the ECU fixed & upgraded just in case...
Cheers,
Hiro

[Hiro]

I was under the impression that the megasquirt I 2.2 utalized a wide band o2 sensor to replace the MAFS or does it get replaced with a narrow band o2 sensor, or something else all together?

Megasquirt 2.2 can be tuned by plugging a wide band O2 sensor:
On the Megatune enrichment page just select "wide band" & set the EGO switch point to 2.5 volts,
If you just use the WB sensor for monitoring (no close loop control) then set the EGO step @ 0%,
This way the ECU will not use the EGO data to adjust AFR.
Hiro

[jordan]

For those of you who are confused about the overall systematic workings of a programmable ECU take a look at this diagram, it may clear up some mysteries.

[Hiro]

Hi to all,
Some update about tuning Megasquirt I on my race 2.5 CIH:
Road tuning of a stock 20E CIH was a 30mn piece of cake work,
But of course tuning my race 2.5 is another story....
I swapped my grey injectors for bigger 350cc/mn ones,
Recalibrated the ReqFuel values & VE tables accordingly,
And track-tested several programs by "old style" monitoring of the plug colour (no wide band EGO sensor yet).
Generally speaking all my programs were much too lean:
I started the day with white plugs & a very low 5000rpm max,
Then by increasing little by little the ReqFuel from 12ms to 16ms,
Plugs turned to a nice tan colour but max rpm was still about 5300 only with poor throttle response.
Then I progressively increased the upper values in the VE table to reach 6000rpm with a better throttle response,
Still not able to run at WOT but time was short for more adjustements.
OK now I need to add about 2500rpm on top of the power band and I'm done,
Still a long road to go...
Hiro

[davegt27]

I would get a narrow band O2 sensor if you can’t afford wide band

People have used narrow band for years before the wide band sensors came out

I have two auto meter AF ratio gauges they work great for me (pn 4375)

I am also using a Super AFC (but this is on a Toyota L-jet)


My project: I have a MS but I want to play with stock ECU for fun (also will move back to Opel I hope)




Also we do plug cuts at the drag strip

That is were we run down the 1/4 mile and at the end (WOT but in your case whatever rpm you choose) cut the ignition off and coast to a stop then we check the spark plugs

Oh what fuel pressure are you using?

Davegt27

[Hiro]

Yes I have a narrow band EGO in hand to plug in ASAP,
Plug cuts is difficult to do here because the only place you're allowed to stop is in the pit lane,
Fuel pressure now is 2.5bar so easy to bump if required.
Hiro