Megasquirt Progress, Main Board complete Options

[yarin]

Tonight I have completed building the main board for my MS II V.3.0 system. Thanks to those that have helped out. Once i'm all finished I will definitely post a complete "How To MegaSquirt a 914" website with pics and step by step. So far i'm still at the desk level. I've got 2.0 injection parts on the way.

I'll be using the following:

stock injectors
GM air temp sensor
stock fuel pump
summit racing manifold referenced fuel pressure regulator
stock injectors (i think 2.0s are on the way)
stock plenum / runners
stock CHT
MS Relay Board
Innovative WB02
High Current ignition driver
Stock dizzy with pertronix (hall sensor)
Stock Bosch Blue Coil
PWM Low impedence injector driver (no resistors)
Stock Cold start Valve (plan so far)
Stock throttle body with some junkyard TPS

Here is a pic of my board, took me a few hours a night every night this week. I took my time, double checked everything. So far so good!

I don't expect to have the system in the car for at least another month. I'm converting from carbs so I want to install steel fuel lines and clean some stuff up.

I'll be sure to post progress in the forums. (IMG:http://www.914world.com/bbs2/html/emoticons/smilie_pokal.gif)

[lapuwali]

QUOTE (DNHunt @ Feb 1 2006, 02:48 PM)

I understand the rising rate FPR but, I haven't found it necessary and I'm not going to mess with it. I've only had a few grips. The idle flucuates with alternator load (I can't imagine running AC) so idle control would be nice. Over run is difficult to tune but was very acceptable with the greater resolution of the Hi-res code. I suspect that will also be the case with MSII. The IAT compensation is off due to heat soak of the sensor in the plenum. Both idle control and air density corrections are being worked on by other people with similar problems. The basic B&G codes for fuel only give a nice replacement for D-jet with the benefit of tunability. Adding ignition control helps even more but, the system is not perfect and is still short of what most of us are used to with modern FI. All in all I've been very happy with my stuff. I've had to repair a couple of solder joints, replace 1 transistor and 1 MAP sensor in 3 years and about 8000 miles. The same board has been used with 3 separate engines and in 2 forms (feul only and fuel with wasted spark distributorless ignition). I can't begin to remember how many different code versions I've used.

Idle control really is a hard thing to do. Someone noted that the early GM ECUs they were hacking on devoted 1/3 of the code just to idling.

It seems a simple task: read the idle speed and adjust things to keep it at that speed. However, there's usually a lag between tweaking a knob and seeing the change in the idle speed, so a simple feedback loop will spend all its time hunting for the right idle speed. The trick is getting the cycle time of the "hunt" fast enough and in small enough steps that the driver won't notice it.

The current state of the art, as I understand it, is to vary ignition timing to alter idle speed, as that has the fastest response time. However, this doesn't work for "fast idle" for warmup (not enough usable range), so you need an air control valve, anyway. Now you're controlling idle speed two ways. As battery voltage fluctuates, injector response time changes, so you get different fuel flow rates depending on alternator load. It's a small effect, but significant at idle, so you have an independent variable controlling idle speed in addition to the airflow and ignition timing you have control of.

Now you know why even big auto manufacturers usually bought their injection systems from Bosch rather than build their own. It's a hard problem, requiring a lot of effort and research to solve. I'm sure Dave didn't mean to denigrate B&G's efforts, just pointing out that two guys doing this part time (now along with a dozen or so other volunteers making significant contributions) have done a pretty amazing job just getting close to what Bosch has spent nearly 40 years perfecting.

I'll be interested to see how you get on with MSII, Dave. The code is still very new, so I'm going to stay away for now. I'll probably just do fuel only for quite some time, since I have a Mallory to handle ignition. The new Microsquirt board may actually be a better bet than MSII, as it uses the same processor, but with far fewer parts on board, so it should be more reliable. The MAP sensor is moved off board, which is probably a net win, really. By the time I'm ready to jump to ignition control, Microsquirt will probably be on it's second version and fully debugged.