Your looks more along with what I would think though. Seems odd to not go full charge power until you go above 160 load? It's not based off the normal loads either and it comes from some variable calculated in the sub-routine that calls up the IPW calc sub and that variable isn't used in too many places. Maybe I'll look at it more tonight and see if I can figure out what that variable is.

I would think there would be some kind of battery voltage feedback in this too though? I'm not sure how these alternators work though as older ones just simply put out what ever current is needed to produce the desired voltage up to their maximum current capacity.

Ever since I replaced my alternator with a new OEM unit, I've had a battery light on below 1500 RPM. I noticed the pulley on the replacement alternator is larger then my stock alternator but figured it's the correct P/N from Mitsu so it should be correct. The alternator cycles off-on often during idle which can't be good for the diodes/regulator. Pretty damn annoying too as the lights dim with the fluctuation. It would be nice if these maps can fix it.

 

Thanks for all the help. I'll try to get my tuner to help me get to the bottom of this at some point.

03WHITEGSR....... The replacement alternator I installed had a larger pulley on it as well. I installed it with the larger pulley and it seemed to produce less juice than the stock alt. I have since swapped the pullies and it made a noticeable difference in power production. I still would like my lights to dim less than they do with voltage drop but I'll have to wait and see if I can crank up the juice.

 

Any chance this could be another trick to net some mileage?

With out lights, radio, or any real electronics it should be possible to shut off the alternator for sprints on the highway, watch the voltage and turn back on before it drops too much. Especially those of us without small batteries.

I'm assuming this might also be some kind of factory power trick such as shutting off the alternator at WOT like many Euro cars do. Does our car do that? I'm assuming yes but I have no idea.

 

Can anyone confirm if the car has some other routine that shuts off the Alternator at WOT?

According to these tables (rom 88590015 V7) my car is not turning off the alternator at WOT. I haven't logged this but the highest rpm cell is 2000 and from 20 load up it's charging.

Wouldn't it be possible to rescale that map so that after 3000rpm the values above ~120 load are 0.0? I wonder how much power is lost powering the alternator at WOT.

On the 88590015 rom is there a way to log this value with evoscan?

 

Just so you know the G terminal is the only terminal on the alternator that controls current flow. I believe the other table is used for monitoring purposes and should probably not be changed.

The operation of the G terminal being 100% is grounded and 0% is ungrounded. When grounded the alternator is supposed to drop to minimal output of 12.3 volts and when ungrounded the alternator is supposed to achieve 14.4 volts.

There are probably other conditional tables where the table we currently have is ignored.

 

I'm basically looking to do 2 things....

1: Shut off the Alt at WOT to gain back some power.
2: Shut off the Alt at cruise to save mileage when watching the volts.

I mostly care about #1, but #2 is intriguing... I know most care little about mileage here.

 

I don't think #1 is a very good idea on a turbo motor. The ignition system has a hard enough time keeping up even with a healthy charging system on a low power car. Maybe sub 350HP you would be ok, but anything above there and I'd worry it's going to have misfire issues.

Add a big fuel pump and a powerful ignition system that you get on a high power car and you are going to want to get all the current you can out of it just to insure the engine runs properly.

Another thing to realize, the alternator only puts out as much power as the car needs and regulates voltage more than current. Under cruise, it tries to maintain about 14.0VDC once the car is up to temp. The G-terminal is a maximum current output at that point and even if it says to put of 50A, if the car only needs 10A to maintain 14.0V, that's all the alternator will produce. Now if the car needs 80A at that point, then because the G-terminal is saying to cap it at 50A, the alternator will only put out 50A and the voltage will drop to whatever level matches that 50A requirement.

 

So the Alternator G Terminal Dead Zone simply defines the maximum draw of the Alternator....

What about the other table? Is that just for efficiency checking by the ECU in order to throw a code for a failing alt? I figured that table actually manipulated the field, but if it doesn't do that, what is it for?

Quite a few cars shut off the alternator at WOT, what I was hoping for was a table that references the battery output which holds a multiplier value used in the normal rpm-vs-load alternator charge maps. That way I could turn it back on if the values are out of whack by adjusting the multiplier. I wonder if such a table exists or something similar.

Once again, I know people here care little about mileage, but the guys turning off alternators on the highway usually have a cheap source of batteries and they happily kill them with such deep charge cycles. Basically they have a few wired in series that can run the car for about an hour or so without the alternator running. However their car can't adjust the alt through the ECU, so they keep pulling belts and such which I'd never do. I'm simply curious what it might do for our car if I had 2 batteries in the trunk wired in series. If I could shut off the alternator for a 35 minute drive at 60mph and turn it back on when getting off the highway it might work. Some guys changing belts and such are seeing over 10mpg difference by just bypassing the alternator on their Geo Metro. That's a small motor like ours.... obviously the gains might be smaller, but for the work involved it's practically free.

 

The FR input is a monitoring wire from what i understand so the ECU probably looks for the wire to have some voltage on it or it throws a code.

You could attempt this manually by using a relay of some kind and a switch in the car hooked to the alternators output terminal to the battery. Should be relatively straight forward but i doubt your gains will be all that impressive. Comparing a super light low powered car to a much heavier evo isn't going to be realistic.

 

So perhaps that table could be used to at least prevent the CEL when manually switching off the alt.... hmmmmm.

I know the gains are going to be minor, but everything adds up just like weight reduction. I commute around 2 hours every day in my Evo at purely highway speeds. For me its a matter of driving my other vehicle (BORING) or driving the Evo to work. I also tinker and mess with everything so this is a fun way to waste time even if it's not impressive or popular.

Thanks for the help.... I might be doing some dis-assembly to locate any more alternator related tables.

My car battery is a basic stock sized battery, might even be stock but I dunno since I'm not the first owner. It seems to stay around 12.7 volts after I shut the car off and I'm able to sit and listen to the radio for over 30 minutes before I get near 12.4 volts. That has to be enough juice for a single few second WOT run. From what I've read about others doing this, it kills batteries by fluctuating the charge so much. Going from 12.0 to 12.5 is nothing. But 12.5 to 11.5 or lower everyday will destroy the life of the battery. I just so happen to have a cheap source of batteries so that doesn't bother me.

 

It's not really a matter of the battery not having the reserve capacity to shut off the alternator under WOT. It's simply the stock ignition system, despite being very good, likely takes a big hit in spark energy when voltage drops. Shut the alternator off and even if battery voltage holds at 12.6V, you have still lost like 20% of your spark energy. This low spark energy might not be enough to ignite the highly compressed and often overly rich air/fuel mixture found on a turbo car.

Add to it the voltage drop associated with pulling 20A on that battery to run a big fuel pump and you can see it's likely not going to work.

Only car I know that shuts off the alternator at WOT is the new M3s. But you are talking an N/A motor with an ignition system designed around running at battery voltage and not alternator voltage.

Also, running the batteries in series will mean you have a 24V system. That’s not going to end well. They need to be wired in parallel.


Don't get me wrong, I'd like to see it work. I've been in a few turbo cars when they have tossed the alternator belt before and it came with serious misfire issues. You knew something was wrong by just the difference in power delivery.

 

I think the best way to find out is to do it and dyno the car. After I get my truck out of the shop I'll have another vehicle to jump the Evo so i can get more experimental with the alternator.

I'll probably just try to shut it completely off at idle first so I can test it in the driveway. I'm still on the stock fuel pump and ignition system so it can't be that bad of a draw.

s/series/parallel I always get that confused now that I don't do electrical work everyday.

 

sorry to dig up an old thread, but does anyone have the mappings for 88580014?

cheers

 

So I am interested in this because these cars come stock with a standard flooded lead-acid battery. I switched to an AGM X2 several years ago because I also have a healthy stereo system pulling a lot of juice and the stock alternator only producing 90 amps just wasn't cutting it. The AGM battery has less resistance, so it can charge up faster compared to a flooded lead-acid battery. Which means less strain on the alternator when Im doing a 120 on I-84 through the S-curves in Eastern Oregon. HaHa just kidding. As far as I can recall, I never had any issues. However, about 2 years ago, I found a company called POWERBASTARDS that produce a 200 amp alternator that fits the evo 8/9. That alternator failed last week. Not the first aftermarket alternator that has failed relatively quickly. I discovered a couple of potential issues.

The first one came from Powerbastards, and that is that the alternator, controlled by the ECU, will only put out a specific range of voltage/current for charging the battery during operation. Which is true. To go extreme, Lithium batteries have a far different charging requirement than a lead-acid battery, along with there heat temperament. So I wouldn't be able to drop a lithium battery and expect the battery to charge. However, AGM batteries are still a lead-acid battery and although they do have different charging needs, their charging requirement are similar from what I have read. I should be able to drop it in and go with no issues, and that is what I experienced. The gentleman i spoke with was adamant that the charging requirements are that different that the ecu settings need to be changed. That being said, i have not had any issues using the x2 AGM battery to date and the problem i spoke of above was solved with a new alternator. Could the the alternator have failed prematurely because of the battery? IDK. In my mind, if there were going to be any issues, it would have been the other way around, I would have had issues with the battery. The alternator doesn't know what kind of battery it is charging and in this case the battery is easier to charge, so there wasn't any extra or abnormal strain to the alternator.

The other issue that I discovered is that these alternators are designed to produce voltage up to the stock rev limit. Taking the alternator on a balanced engine past the 7200 rev limit can cause premature failure. So the fix is the bigger pulley, but there bigger pulley will cause the alternator to run slower at idle as well. Is this enough to to cause issues? I don't know. Does it really matter at idle (unless of course you turn on your A/C)? Not sure. Along with that is the fact that many stock alternators, including the evo alternator, don't produce maximum current potential until something like 6200 rpm. What kind of problems would that produce? Seems logical to assume that the alternator is rotating slower in all RPM ranges to compensate for the Higher engine RPM. But Im not sure that would actually cause any problems.

But for arguments sake because i am by no means an expert in all the things going on in the ECU and the Battery charging needs. Access to those maps allow adjustment to those charging parameters, and hence allow proper charging of alternate batteries. Did anybody, figure out how to adjust those parameters?