Hi Gang,

I really need some expert advice ASAP. The track season has hit Vancouver and will be in full force this Friday. Of course my problems will not be worked out by this Friday, but I would like some ideas and help to have the car at full speed soon. That being said....

I have a 93 240SX with a SR20DET Conversion running a Garett T03/04. My motor is built and has all forged bottom end. I bought the car like this for a really good deal and am hoping to actually use it's potential unlike the guy who spent 20G's on it and left it unfinished.

One of the problems were that it had stock injectors, so I have ordered a set of 700cc nismo injectors along with a Adj. FPR (Thanks to eBay) and they should be coming soon.

My next and most important problem lays in my Ignition system. The shop who built this car didn't do their homework. They put in a Holley Commander 950 Stand alone ECU (which is fantastic and I love being able to do real time tune). They also put in a MSD Midget 6412 Race igntion, which is also fully stand alone and programmable. The problem with this ignition is that it was made for Midget Racing and none N/A 4bangers. It does NOT allow for boost retard. I can program a retard timing curve but it's throughout the whole RPM range. I can't make it retard only under boost.

My Holley Commander 950 Manual States the following in regards to Ignition wiring:
"Crank Trigger CD Ignition Systems - The Commander 950 can control the timing on any engine that uses a crank trigger (magnetic or Hall effect) and capacitive discharge ignition box."
"Non-Computer Controlled Inductive Ignition Systems - Any inductive (non-CD) ignition system (most stock ignition systems are inductive) can be used to provide an RPM signal to the Commander 950. These systems will not allow the Commander 950 to control ignition timing. Points ignition and the Mallory Uni-lite systems fall into this category."
"Magnetic Pickup Distributors with Mechanical Advance - Standard Magnetic pickup mechanical advance distributors such as a Holley or MSD can be used with a CD ignition system. The C950 will not be able to control timing. "

That being said, what do you guys think I can do for ignition? I would love to be able to just control timing and retard from the Holley. Can I hook up a Crank Trigger CD Ignition system? If so, wtf is that? lol.

My current MSD box is worth over $500 bux, so I'm sure I can sell it and get the right ignition for my application. I'm hoping to run 450-480RWHP but I can't do this without boost retard right? Heck, I don't even know where I can read my current timing curve.

Thank you much in advance. If I've missed some information, please let me know. I appriciate any help at all.

Cheers,

Houman.

If the ECU allows you to compile maps in 3D form then you should have the capaicty to build ignition maps based on TP, Load (MAP), or a combination of the two.
The ECU will rely on a 0 to 5volt square wave (digita)l input and this is why the "will not work" combinations Holley describe, will not work. They are 0 to 12volt peak to trough analog signals. The other reason the ECU will not control those types of configuration is because the the inductive tyoe ignition circuits are "delayed" relative to crank position to accomodate for coil saturation time (dwell).
Get rid of the Holley ignition module and if you can, build the maps off of the ECU. If you want a higher voltage to the plugs, hten the standard MSD capacitive discharge systems, fired from the ECU will be fine enough. Because it is CD the saturation time is ot an issue and the offset in crank position is marginal.
The better CD systems are NPN type transistor controlled as opposed to the 99% if the market being PNP controlled.........another issue, but one that will not have impact on what you wnat to do.

If the ECU allows you to compile maps in 3D form then you should have the capaicty to build ignition maps based on TP, Load (MAP), or a combination of the two.
The ECU will rely on a 0 to 5volt square wave (digita)l input and this is why the "will not work" combinations Holley describe, will not work. They are 0 to 12volt peak to trough analog signals. The other reason the ECU will not control those types of configuration is because the the inductive tyoe ignition circuits are "delayed" relative to crank position to accomodate for coil saturation time (dwell).
Get rid of the Holley ignition module and if you can, build the maps off of the ECU. If you want a higher voltage to the plugs, hten the standard MSD capacitive discharge systems, fired from the ECU will be fine enough. Because it is CD the saturation time is ot an issue and the offset in crank position is marginal.
The better CD systems are NPN type transistor controlled as opposed to the 99% if the market being PNP controlled.........another issue, but one that will not have impact on what you wnat to do.

Thank you for your reply.... The ECU does allow for 3D mapping, yet I haven't tried that. I'm not even sure if the damn thing is hooked up right! lol. The car runs decent under 12 PSI right now...

ANyway, I don't have a Holley ignition module, I have the MSD midget. This is where I'm confused. When you said get rid of it... Do I just get rid of the box? or the box and coil pack? I guess I need to know how the stock ignition is wired/setup so I can rewire to stock, then just add an ignition box for better spark.

Thanks again.

Either way the ignition module will take its trigger timing (crank timing) from the ECU. If you can 3D Map then the best combination will be a load (MAP) and TPS position relative to rpm type mapping.
You need to ensure the map has resolution that will be sufficient to take the motor through the rise and peak of the torque curve. Also that the retard function is map site specific and not generic to any single input variable.
Not too sure what the MSD Midget is but if it's CD and you can programme it to just fire on command without any correction or independent mapping then it should be able to work just fine.

that's the thing. This MSD Midget is stand alone ignition and it's not hooked up to the ECU. When I try to pull the spark map from the ECU, i get 0's... The MSD midget has two megnetic triggers on the crank. I need to get rid of it i guess.

Maybe you or someone else can be kind enough to check out my ECU and MSD instructions to see what I need to do and if they COULD work together. I'm not very technical when it comes to this stuff. Much thanks.

ECU:
http://www.holley.com/950-104.asp (instructions on the buttom right)

MSD:
http://www.msdignition.com/ignition_14_6214.htm (description)
http://www.msdignition.com/pdf/6214_frm22773.pdf (pdf instructions)

The ECU can do what you want. The MSD unit cannot with the efficiency you need.

MSD 6412: It has a dual magentic trigger, one for identification of TDC and the other for each cylinder. It uses the cylinder refferences to calculate rate of acceleratin and crankshaft position. It uses the TDC #1 refference to determine where each cylinder is relative to a designated starting point.

Holley 950: The ignition maps are showing 0's because the installer thought he could use the MSD 6412 to control ignition point independently. If it were NA the problem would not be as big; however as the motor is FI the ignition needs to respond to three variables, MAP, TPS and RPM. Now the 950 is pseudo 3D in that it allows TPS and RPM (Alpha-n) or Load and RPM (Speed Density). You have to run Speed Density, however you will still be limmited because the relationship between speed (rpm) and density (MAP) is not a linear one. The ideal 3D maps will allow you to correct speed density based on TPS because the MAP Sensor is upstream the throttle plate and therefore the down stream pressure is lower (hence the Volumetric efficeincy changes). In short the ECU is not a tru 3D system.

What you need to do is replace the Magnetic Trigger signal from the crank shaft to the MSD, to the ECU instead. The ECU will control the ignition curves by then processing and sending the ignition output to the CD System. it does not appear that the MSD 6412 will allow for a passive interface (simple on off commands from the ECU). A regular old MSD 6A, or my suggestion would be Crane HI6, would be the way to go.

The Magnetic Trigger should be useable as input to the ECU, however the very same signal is generated by the OEM Distributor or Cam Sensor. The ECU needs the same timing signals as MSD 6412. I am sure you can wire the Mag Sensors accordingly, however the Dist or cam Sensor will be more accurate as the relative speed is 1/2 that of the crank and therefore the ECU has a more TIME to calculate position and generate an output. My personal prefferance is the Cam for this and the other reason that the front of the crank oscilates and there si a certain amont of signal scatter as a result.

Simply get the signal from the Cam or Crank or Distributor in 5vdc Square Wave form to the ECU, then let the ECU trigger either a CD driven single coil or standard non-amplified coil. You will have to rely on the Distrributor to place the high voltage signal to the respective cylinder. Because the distributor will be used the ECU timing will be out by the accuarcy by which you place the distributors timing. The ideal would be have multiple signal outputs (2) and run a wasted spark system with two coils. This will allow you to place the ignition point independent of peripheral mechanical systems which will have timing offsets.

Hope this helps.

thank you for your reply. it's a HUGE help!