MTX alternator question

[nkb93]

I'm going to use 3.0L accessories when doing my ATX to MTX swap. The donor SHO is a '90, so its alternator is only 90 amps compared to the 130 amp unit that's currently on the ATX.

A few questions I'm hoping to get cleared up:

1) Will I notice much of a difference between 130A and 90A output? I have an aftermarket stereo, but nothing too crazy (400W RMS total output).

2) How does the wiring harness for the '90 alternator differ from the '93 ATX alternator? Is the '90 internally regulated?

3) Would it be significantly easier/better to use a '94-95 3.0L alternator? I think this requires some different bracketry, right? If so I'll need to start looking for these parts..

thanks,
Nate

 

[Ace]

well not only would you have to change the harness to use the 94 95 alternator but i think the brackets are different too....the later alternator is totally different from the 90 you have...the 90 amp should be fine for what you are doing..

 

[nkb93]

Alternator wiring pinout

What are the pinouts for the two alternators ('93 ATX and '90)?

I tore down the MTX donor car this weekend to remove all of the stuff I need for the atx to mtx swap.

I was hoping it would be a direct plug-n-play between the '90 alternator and the ATX wiring harness, since I'm keeping all the stock ATX wiring (as much as possible). However, the alternator from the '90 has a two wire connector, whereas the '93 ATX has a three wire connector.

I think it'll work out, just need to figure out how to merge the two connections.

As an aside, are the '90 and '93 MTX alternators the same connector? My '93 Helms manual shows the 3.0L SHO alternator as a three pin connection. Just curious.


Thanks in advance,

Nate

 

[element913]

1) The ATX alternator is a 120 amp unit. You will notice a slight loss of power (if it is under load).

2) The 89-93 MTX alternators are all internally regulated (with a 2 wire connector). The 94-95 (and maybe atx?) alternators are externally regulated with the regulator mounted directly on the alternator (outside), these have a 3 wire connector and a 2nd, single wire connector. The difference is simple, one of the wires on the 3 wire connector goes into the single wire connector (for the stator) so you still ultimately have only 2 wires needed (yellow, regulator power and green/red, battery light indicator). You also have to change the fusible link for the voltage regulator power wire, and you might require an increase in the size of the alternator + wire (I think its a 10 gauge on the 89-93 for 90 amps, not sure about 94-95)

3) Because of the single belt serpentine setup used on the ATX motor, The pulley will probably have to be changed on the ATX alternator (not sure) and the ATX bracket for the alternator will use a different engine mount, for a different subframe (I believe).

I wrote a short How-To for the 94-95 Alternator Upgrade here:
http://www.shoforum.com/showthread.php?t=48847

Hope it helps,
Mike

 

[ManySHOs]

I would not attempt to install an ATX alternator on an MTX engine or try to swap the pulleys without anticpating some modifications. I'm building on top of what others have said here and adding my own.

89-93 alternators are 90a units. In mid 93, the alternator was slightly redesigned; the front case half is bored out differently to accomodate a different size bearing. The armatures appear to be identical but because the front case half is different, the pulleys cannot be swapped between these two designs because the pulleys will rub on the housing. (I'm just supplying extra info here). These alternators are interchangeable with all 89-93 3.0's.

94-95 3.0 was a 140a design (3G alt) which is supposed to provide better voltage regulation under load. If you want to swap this to an earlier mtx block, you need the front cast iron mounting bracket, the alternator to AC compressor bracket and of course the alternator and pulley.

93-95 3.2 atx were 120a designs which I know almost nothing about.

I used to drive a 94 atx with the 120a unit and I now drive a 93mtx with a 90a unit. I have UDP's on the 93 (or "had" them) and the same stereo that I had in the 94 atx. I don't see any differences.

I considered installing the newer 3G 140a alternator but time constraints prevented me from going ahead with the project. The engine is now in the car so I'll probably never do it.

Ian

 

[nkb93]

Thanks for the info, guys.

I'm swapping all the accessories from the 3.0L ('90 model) over to the 3.2L similar to what is done on a typical 3.2L MTX swap, I assume. Not planning to use any 3.2L accessories, so no worries about fitment with the MTX brackets.

I'm trying to figure out how to reconfigure the wiring to make the 3-wire ATX alternator harness work with the 2-wire '90 alternator. So, one of the terminals on the '90 alternator is the battery light indicator and the other is regulator power (which is then internally fed [regulated] to the stator field)?


-Nate

 

[ManySHOs]

Thanks for the info, guys.

I'm swapping all the accessories from the 3.0L ('90 model) over to the 3.2L similar to what is done on a typical 3.2L MTX swap, I assume. Not planning to use any 3.2L accessories, so no worries about fitment with the MTX brackets.

I'm trying to figure out how to reconfigure the wiring to make the 3-wire ATX alternator harness work with the 2-wire '90 alternator. So, one of the terminals on the '90 alternator is the battery light indicator and the other is regulator power (which is then internally fed [regulated] to the stator field)?


-Nate

Because you are doing an ATX to MTX swap, I'm not sure. When I put a 3.2 into my mtx, I just used the appropriate engine wiring harness (MTX) and that issue was taken care of for me. It sounds like you are trying to use the ATX wiring harness?

You might want to post this question with another topic heading under performance mods. Something like "ATX-> MTX swap wiring q's" is bound to get attention from those who have done this.

Shoaz should have some insight.

good luck
Ian

 

[nkb93]

Because you are doing an ATX to MTX swap, I'm not sure. When I put a 3.2 into my mtx, I just used the appropriate engine wiring harness (MTX) and that issue was taken care of for me. It sounds like you are trying to use the ATX wiring harness?

You might want to post this question with another topic heading under performance mods. Something like "ATX-> MTX swap wiring q's" is bound to get attention from those who have done this.

Shoaz should have some insight.

good luck
Ian

Right, I'm trying to keep all the ATX wiring harnesses where possible. Shoaz has been a great source of info for the swap process, however he fabbed up custom brackets so that he could use the ATX accesories.. I'll try posting as you suggest, I think someone with a wiring diagram of both the '90 and ATX alternator circuits could easily determine how to make them compatible. Maybe it's time to pony up for a Helms EVTM.

 

[element913]

I am not sure you can do that as the Engine Computers are different (They have different pin configurations Im assuming). Since they have shift points and all that extra stuff (As well as additional sensors). I recommend that you use the 3.0 Harness. It really is not worth the trouble to use the ATX harness (unless you are trying to avoid taking off the intake manifold and fuel rail). When I did my 3.2 swap I had the 3.2L injectors cleaned and balanced at a local fuel injection shop (and to my surprise, one of them was bad and had to be replaced), had I not done this (it only cost me $100 for the test, and $100 for a brand new injector) I would have basically had a dead cylinder right from the start. I really recommend that you have the injectors inspected, while the engine is out of the car and everything is easy to get to. You are also aware that you have to grind/saw down the side of the front head right? Since the extra work is so much easier while the engine is out of the car you should do as many services as you can (even a 60k doesnt hurt).

-Mike

 

[nkb93]

I am not sure you can do that as the Engine Computers are different (They have different pin configurations Im assuming). Since they have shift points and all that extra stuff (As well as additional sensors). I recommend that you use the 3.0 Harness. It really is not worth the trouble to use the ATX harness (unless you are trying to avoid taking off the intake manifold and fuel rail). When I did my 3.2 swap I had the 3.2L injectors cleaned and balanced at a local fuel injection shop (and to my surprise, one of them was bad and had to be replaced), had I not done this (it only cost me $100 for the test, and $100 for a brand new injector) I would have basically had a dead cylinder right from the start. I really recommend that you have the injectors inspected, while the engine is out of the car and everything is easy to get to. You are also aware that you have to grind/saw down the side of the front head right? Since the extra work is so much easier while the engine is out of the car you should do as many services as you can (even a 60k doesnt hurt).

-Mike

Thanks for the advice.. I'm definitely going to do all the maintenance while the motor is out, it's amazing how much more fun it is to work on when you have easy access. It took about 30 min to totally strip the 3.0 of its accessories, brackets, covers and crank pulley. Wouldve taken me several hours with it in the car, I imagine.

I'm debating the harness swap, mainly because I'm not 100% sure that the 3.0 harness I have isn't damaged. The engine will run fine using the ATX computer even without the ATX tranny hooked up (others have done this, such as Shoaz in his orange race car). The problem is the check engine light and O/D lights are flashing all the time, so I was going to disable them (and have a switch for the CEL so that I could check the codes every now and then).

If I end up wanting to run a 3.0 computer in the future, I have the wiring diagrams for the 3.0 and 3.2 PCM pinouts, so it would be straightforward to effectively turn the 3.2 harness into a 3.0 harness (but probaby a PITA).

I've got the sawzall ready for the alternator boss on the front head.

-Nate

 

[ManySHOs]

Thanks for the advice.. I'm definitely going to do all the maintenance while the motor is out, it's amazing how much more fun it is to work on when you have easy access. It took about 30 min to totally strip the 3.0 of its accessories, brackets, covers and crank pulley. Wouldve taken me several hours with it in the car, I imagine.

I'm debating the harness swap, mainly because I'm not 100% sure that the 3.0 harness I have isn't damaged. The engine will run fine using the ATX computer even without the ATX tranny hooked up (others have done this, such as Shoaz in his orange race car). The problem is the check engine light and O/D lights are flashing all the time, so I was going to disable them (and have a switch for the CEL so that I could check the codes every now and then).

If I end up wanting to run a 3.0 computer in the future, I have the wiring diagrams for the 3.0 and 3.2 PCM pinouts, so it would be straightforward to effectively turn the 3.2 harness into a 3.0 harness (but probaby a PITA).

I've got the sawzall ready for the alternator boss on the front head.

-Nate

Personally, I'd get an mtx harness. You'll need the PCM, the main harness that connects to the PCM and the engine harness that plugs into the main harness. Make sure that the main and engine harnesses are from the same year or they may not mate. There was a changeover somewhere between gen1 and gen2.

If you want the higher output alternator from the 94-95 mtx's, try to get all the stuff from a 94 or a 95.

Keep us/me posted. This is good stuff.

Ian