Printable Version of Topic

Click here to view this topic in its original format

914World.com _ 914World Garage _ More megasquirt questions....

Posted by: "Z" Jun 22 2006, 11:19 PM

Not getting any response on the shop talk forum....project is a blown Type 1 motor. It's a stroker 92/82 displacing 2180ccm and it has the Hideaway turbo kit from CB Performance with a HEI ignition. We put on a Megasquirt-II instead of the Delco ECU to get more tunability. Now I am looking for some pointers for the ignition table. Here is what I came up with so far. Please give me some feedback.

IPB Image

Posted by: Mark Henry Jun 23 2006, 07:58 AM

I get a headache just looking at that table
I'm glad I picked a simpler system to program

I don't know if this helps but it's worth reading

http://www.sdsefi.com/techign.htm

Posted by: "Z" Jun 23 2006, 08:04 AM

Half the fun of these cars is building something unique....if it was easy it would be a Honduh....

I'll check out the link.

Posted by: DNHunt Jun 23 2006, 08:27 AM

Mike

I've never tuned anything with forced induction but, that seems like a lot of advance. Also with that stroke should you be pulling some advance out to acount for the high speeds at high revs.

I'll try and post my table later.

Dave

Posted by: "Z" Jun 23 2006, 04:23 PM

bump...

Posted by: TimT Jun 23 2006, 04:35 PM

I think you have way to much timing dialed in, also way to early.

We time turbo cars (911s) to have 24 deg total advance, sometimes 22

Im not familiar with the megasquirt system, does that table take into account the engines static timing?

Posted by: lapuwali Jun 23 2006, 04:53 PM

MS has a trigger offset value that you can set to anything you like, depending on where the trigger is statically timed wrt to TDC. The table values represent crank degrees with that offset value considered.

That's one thing about the software they get right. If you think of the most flexible, most sensible way to do it, they do it that way.

The SDS way of a RPM/degrees "map" and another "retard degrees based on vacuum" makes sense to people who are used to distributors, since that's exactly how a vacuum distributor works. The 3D map that MS uses allows more flexibility. If, for example, you want more advance at cruise, and you cruise typically at 3000rpm, with a MAP of 60kPa, you can set that, but have less timing at 3000rpm under boost. Setting more retard under boost as SDS does will do the same, but it will pull the same amount of timing at 6000rpm as it does at 3000rpm, when you may actually want to pull less (or more).

That said, more degrees of freedom means more ways of screwing something up, so the SDS philosophy isn't at all bad, just different.

As to the values in the table, 46 degrees seems insane to me.

Is this a hot street car, or a drag car, or what?

Posted by: "Z" Jun 23 2006, 05:23 PM

Hot street, with longevity in mind....

Posted by: "Z" Jun 23 2006, 05:26 PM

Even with only 5lbs of boost it's pretty quick. The old Delco/GM ecu just wasn't tuneable enuff and was WAY too FAT....

Posted by: lapuwali Jun 23 2006, 05:55 PM

I'd consider running a lot less timing, like 36 degrees as the max. Keith Duckworth used to be very pleased when any engine could run at peak performance with less than 25 degrees of timing. Engines with pretty crappy combustion chambers often need 10 degrees more than that. Any more, and you're most likely working against yourself. It will probably even run cooler. However, I know nearly nothing about Type Is, and absolutely nothing about turbo Type Is.

Those big jumps, like running 20 degrees at 1000rpm and 27 at 1300, at 90kPa, seem odd to me.

Posted by: "Z" Jun 23 2006, 10:15 PM

Killed the starter....so I'm toast until Monday when a new one can be installed.

Here's a new chart........

Attached image(s)

Posted by: Brett W Jun 24 2006, 12:05 AM

I am trying to read your settings. Change your boost settings to psi instead of KPa. Since I am not used to reading settings the way you have it I am probably going to reference the wrong areas. My maps are different.

First, is the timing synced with the engine. Are you showing total timing or are you supposed to add your base timing to the values in the map.

Next, why is there a weird dip right off idle? Where is WOT on this map? Up top right corner? If that is the case then you are probably about right on the timing. Remember you can run tons of timing at part throttle and cruise.

What do your plugs look like? What do your AFRs look like under cruise and boost. What is your static timing at the Dizzy?

Posted by: Mark Henry Jun 24 2006, 07:26 AM

Mike read this and email this guy, I know he'll share his maps and he has "real" MS turbo T1 experience.

http://www.msefi.com/viewtopic.php?t=7960

Posted by: ischmitz Jun 24 2006, 10:55 AM

Mark, this is the table from Minami over on the Megasquirt forum that you've mentioned in your link. He claims he has run up to 17PSI boost. Well, he uses water injection under boost to keep the charge cool.

Attached Image

Brett, the timing values are absolut. Megasquirt allows to set the static offset to make all values in the table real. We checked with a timing light and it is pretty close. The dip from 700 RPM to 1000 RPM is something I found in all Bosch Motronic maps. It prevents the engine from stalling by bumping up the advance once the RPM wants to drop below the 1000 mark.

To read this table and convert kPa to PSI think about the 100kPa line as WOT. Everything above the 100kPa line is boosted and as we go down to 40 kPa we have vaccum (closed throttle)

120 kPa = 2.9 PSI boost
150 kPa = 7.3 PSI boost
180 kPa = 11.6 PSI boost
215 kPa = 16.0 PSI boost

The fuel map will get tuned with an LM-1 as feedback. We will set the cruise area lean to make sure we can afford to drive it with 4$ per gallon here. Under boost it will be closer to 11:1 to make sure it does not burn the pistons. Megasquirt has the option to use the wideband O2 sensor signal and shoot for a target AFR depending on RPM and load. Once the map for fuel is dialed in we will put a narrow band O2 sensor in permanently. Hm, maybe I'll ask Mike to apply for a SMOG certificate with his friends at the DMV if he gets the oil leaks under control

Here is my latest rendition of the ignition map. I smoothed out some of the rougher areas. Remember that Megasquirt interpolates between RPM bins. I guess we just have to take it to the dyno and see how it does and then to the machine shop if it grenades....

Attached Image

What do you guys think,

Cheers,
Ingo

Posted by: Mueller Jun 24 2006, 11:13 AM

I see Ingo still hangs out with Mikey, some people just don't learn, hahahaha

Welcome Ingo,

I met you a few years at the Dunkles swap meet

Posted by: ischmitz Jun 24 2006, 01:35 PM

Mueller OMG, that was the same year at Dunkels when we paid MS Roadshit's trailer a special visit - and you brought my seats.

Mikey takes his meds more frequently these days. They took the edge off

Posted by: Brett W Jun 24 2006, 04:10 PM

I am not used to the Megasquirt console yet. Still working on my experimental MS car. Here is the way my maps look in Hondata. I find this program much easier to work with. My scale uses Mbar and PSI. You should be able to run without the "dip" since you have a TPS and much better ignition control than the early Bosch stuff.

That map looks about right. As you can see from my ignition map below I also run lots of timing at part throttle and light load.

Attached thumbnail(s)

Posted by: Mark Henry Jun 24 2006, 05:27 PM

Watch your head temps if you lean cruise....

On an N/A type 4 my temps go way up when I tried it. Wasn't worth dropping a valve for 1 or 2 mpg.
Not a watercooled.

Posted by: Brett W Jun 25 2006, 12:47 AM

Go out and try something. Take your 15-25% throttle cruising range and lean it down to 16:1-17:1. Crank your timing up to the high 30s to mid 40s and see what happens. Up your accelerate pump feature for that range of the map, so that you can help the transition from cruise to medium load range. I am talking about the range where your engine runs when climbing a slight grade, maybe 8% or so.

Posted by: "Z" Jun 26 2006, 12:34 AM

He lives just down the street....can't avoid me....