GM DIS vs. HEI

CHEVY250 · Post by **CHEVY250** » Fri Feb 18, 2005 5:28 am

Hello,

I have a CHevy 250 inline 6.
I'll be getting a megasquirt in the summer but in the meantime I'd like to upgrade my ignition from a 4 pin HEI with vaccuum advance to GM DIS.

I understand the GM DIS system has it's own limp home mode without input from the ECU, does it control it's own advance in this mode?

Can I get rid of my ditributor and put in the GM DIS if I don't have the megasquirt yet?

Thanks

jsmcortina · Post by **jsmcortina** » Fri Feb 18, 2005 5:52 am

The GM DIS like HEI7 will run at base timing (e.g. 10BTDC) when in limp mode. This would get you home if something went wrong but the car would run very badly and have no power.

You need an ECU to control either system.

James

CHEVY250 · Post by **CHEVY250** » Fri Feb 18, 2005 9:53 am

What does the MS base its timing advance on? on the vehicles tach speed? I don't get why the modules couldn't have been made to control this on their own.. but whatever.

Oh well I ges I'll have to get the MS before summer!

although I'd still have to wait for MSII because I want to have the idle adjustment feature available.

(i can run the MS solely for spark advance in the meantime right?)

Thanks

ChevelleFan · Post by **ChevelleFan** » Fri Feb 18, 2005 10:34 am

Stock MS was designed for fueling only. Spark and IAC control comes with MS-II.

The spark advance is based on RPM and MAP, much the same as a conventional dizzy. At a certain RPM, more advance is dialed in (mechanical advance) and at low-load, even more advance is dialed in (vacuum advance).

If you were going to do the project in stages, it would probably be best to start with the fuel side and then do the ignition when MS-II comes out.

-Dave

78Spit1500Fed · Post by **78Spit1500Fed** » Fri Feb 18, 2005 11:38 am

ChevelleFan wrote:Stock MS was designed for fueling only. Spark and IAC control comes with MS-II....

Not quite; Stock MS was designed for fueling only; true. But you can get very slick spark control with the stock MS hardware and new firmware, namely MegaSquirt 'n Spark-Extra.

IAC control is also possible with a standard MS and an add-on board called MSIAC, but it's hard to come by these days.

If you MUST have IAC control, it would be better to wait the 3-4 weeks it will take for Bruce to get MSII to the masses.

-Brian

TurboCamaro · Post by **TurboCamaro** » Fri Feb 18, 2005 3:04 pm

Brian,

Do you have anymore information on this MSIAC? If there was a schematic of it and how to interface it with MS then people could make it on their own. Where did it come from? I did a search on the board but couldn't find anything.

Thanks!

TurboCamaro · Post by **TurboCamaro** » Fri Feb 18, 2005 3:09 pm

Is this what you were talking about?

http://autos.groups.yahoo.com/group/ms_iac/

78Spit1500Fed · Post by **78Spit1500Fed** » Sat Feb 19, 2005 7:52 am

TurboCamaro wrote:Is this what you were talking about?

http://autos.groups.yahoo.com/group/ms_iac/

That's the one. There are schematics, BOM and even a PCB layout, I believe on the files section of that site.

From what I hear it worked really well, but since it was being integrated into MSII and UMS, they dumped it and stopped producing boards. I'm sure someone out there who has MSIAC will be switching to MSII, and won't need their board anymore. Perhaps you can pick one of those up?

-Brian

MegaScott · Post by **MegaScott** » Sat Feb 19, 2005 9:12 am

Can I get rid of my ditributor and put in the GM DIS if I don't have the megasquirt yet?

The GM DIS still requires a crank trigger wheel and vr sensor be installed right? If you are going through all the trouble of installing a crank trigger, why not go with EDIS? you can use an EDIS6 module off a 90's Ford Ranger or Explorer and you will have no trouble interfacing that to Megasquirt. Lots of those running, and it runs very well I might add!!.

Tried running my EDIS in limp mode the other day (while trying out Multispark, which isn't supported on my module) yes it runs, it ran like it had maybe 10HP! went out of limp mode, and it was like someone hit the nitrous button!!

Point is, yes you could run your engine with just a DIS module hooked up, but at a fixed 10BTDC you really aren't going to create any real usable power unless you have a Megasquirt or other computer, to run it properly.

jeep45238 · Post by **jeep45238** » Sun Feb 20, 2005 11:03 am

The GM DIS is run off a reluctor wheel that triggers a magnetic sensor all based off of the crankshaft.

My saturn project has a wheel between the 3 and 4 cylinders, and the ignition modual powers 2 coils with wasted spark for the 4 cylinders.

I'm anxiously awaiting the MS II for ignition control, but have also been eyeballing the Megasquirt and Spark Extra big time lately.

Let's just say that 20 psi, T3/T66 hybrid, water injection=big power, but with ignition control.....can't wait.