dastallion951

well considerin the fact that apparently the rx8's ignition system is now known to be weak........especially in FI applications....wouldnt it make since ur upgrading the coils plugs n wires, to also upgrade the battery preferably to an optima battery, since our battery is known to be weak..........??? just my thoughts......

lurch519

battery is only there to start the car. thats it. period.

TeamRX8

iTrader: (25)

think so, disconnect the battery after you crank it and see

MazdaManiac

iTrader: (3)

The battery acts as a stabilizer for the electrical system.
Without it, the available current for operating such minor things as your entire EMS and ignition system will be insufficient.

BTW - Why do people feel the need to add things like "that's it. Period." to the end of their posts?
Even if the data presented is of absolute certainty in the situation in which it is applied, its "absolute" nature can always be put asunder and those that don't believe in its certainty will not put any more faith in the presenter just because of his certainty of its absolute nature.
Putting "period" at the end of an assertion only makes you suspect.
Period.

mysql101

^ End of story.

lurch519

i apologize in adding ""that's it. Period."" to the end of my post.

as to the statement that the battery acts as a stabilizer for the electrical system, that is partly correct, wherein if you are putting addtional load on the electrical system, ie extra lighting, upgraded audio systems, etc, then yes the battery can act as a supplemental energy source when the available output of the alternator has been surpassed. if the battery was there to provide power to the system to the ems and ignition system, then the battery would be in a constant state of discharge, and would eventually run out of stored energy.

this can be seen in vehicles with larger car audio systems that do not have high output alternators, where the battery initially can have a full charge, but after a while of playing the system at elevated levels, even keeping the engine at cruising rmps, the voltage in the system will drop down, and eventually the vehicle will stall as there is not enough power to keep everything running.

and please dont take this as me trying to bash you MM, i have the utmost respect for you and the knowledge you have. i will freely admit i dont have the accumulated knowledge on rotary engines, let alone motorsports in general that you have, but i have been selling and installing car audio at a specialty retailer for almost 10 years, so i do know a thing or 10 about electrical systems in automobiles.

lurch519

i have, no problems

MazdaManiac

iTrader: (3)

The neutral electrical load at idle is about 14 amps. The generator output at idle is about 15 amps. The generator ramps up significantly with RPM.
Turn on your dome light (1.5 amps) or your headlights (about 12 amps) and you will be in an interesting scenario.

Plus, without the battery, any change in load would mean some significant Alzheimer's for the PCM. (Not to mention the car-b-que that would ensue after a while from the melting integral regulator that requires a battery as ballast.)

No disrespect to you, either. However, I have yet to meet a radio installer that could change a light bulb without pictorial instructions, so I don't particularly engage that claim as a credential.

lurch519

You're right. I forgot about all that. But then, If you left the car running at idle, with the lights turned on and the stereo turned up, then the battery should die after a period of time.

No disrespect taken.

MazdaManiac

iTrader: (3)

As you load the system down, the drain causes drag on the generator which the PCM compensates for by opening the throttle to keep the idle speed up.

lurch519

ahhh, yes, now i see the light.

and even though the throttle opens up a little, there will be a momentary drop in available current. i shoulda thought of that earlier, but that is the nature of my mania, i sometimes miss the little details.

i knew about the drag, its one of the reasons why you cant build a perpetual motion machine from a generator driven by an electric motor powered by the generator.

thanks mm.

MazdaManiac

iTrader: (3)

Yeah, a car would be a perpetual motion machine - if it weren't for those pesky hydrocarbons!

Actually, I haven't really thought about why Mazda went with a generator instead of an alternator on the '8. I'm sure there is a good reason.

lurch519

I don't know, but looking at the electrical schematic, it is referred to as a generator, but it is generating AC current as seen by all the diodes referenced in the schematic.

MazdaManiac

iTrader: (3)

Yeah. It is an interesting device.
Instead of having a commutator setup like a normal generator, it has a bridge rectifier like an alternator.
In fact, it has a stator and a wound armature, so I don't know what the hell is going on there.

O'Renesis

The RX-8 uses an 'Alternator' not a 'Generator'. At least that is what it is called in this part of the world. Why Mazda call the alternator a generator I do not know, although it could be called an AC generator. But it certainly is an alternator in my RX-8. Looking at the wiring diagrams for the car it shows a star wound stator and full wave bridge rectifier. This alternator outputs 3 phase AC power and is converted to +/- 12VDC by the rectifier.

"battery is only there to start the car. thats it. period."

I dont think that is correct. My understanding of the battery and alternator is that the power for the car is run from the battery as well as starting the engine. The alternator/generator is used to charge the battery. Obviously the battery cant be removed, because it would be very difficult to start the engine without it , but once started the electrics will work OK, just. Without the battery the voltage would not be stable and would fluctuate with revs and load. The battery can deliver a very high current instantly without relying on the engine revs. If the total current drawn from the battery exceeds the alternators maximum charging capacity the battery will eventually go flat.

Oh,I forgot to say, I like this mod, nice job

MazdaManiac

iTrader: (3)

The main defining difference between the "alternator" and the "generator" are the internal method for generating current.
A generator uses a fixed magnetic field with a rotating coil (armature). An alternator is the opposite (the coil is stationary).
On the '8 there is a rotating coil even though there is a bridge rectifier.
I need to take one apart to see what is going on.

O'Renesis

The whole subject of alternators and their use in the automotive industry is a vast subject and somewhat off topic here. An alternator can have a rotor made using a magnet or more usually a wound rotor. This wound rotor is connected to the cars electrical circuit through a slip ring and carbon brushes. The usual reason for using a wound rotor is so that a varying magnetic field can be achieved and consequently a varying voltage output from the alternator's stator coils. This varying voltage is needed as the cars current/load varies according to demand.

dastallion951

k sorry we all got off topic from this DIY...........however wouldnt it make sense.........if ur goin FI........ there was a TSB about our weak batteries...........n now more recently more of us r startin to realize how insufficient our ignition coils on it are.......so my point was like the creator of this thread upgraded his coils.........to twin fire ones..........wouldnt it make sense to upgrade to a battery with higher cold cranking amps, higher cranking amps, and a faster recharge time...........??? im no electronics genius but i got the generality down......n im not tryin to diss anyone im just sayin wouldnt it make sense..........????

dannobre

iTrader: (3)

Batterys suffer from a problem.....as the CCA capacity goes up...they get larger and heavier.

The usual compromise is choosing a battery that fulfills the needs....and doesn't sink the ship so to speak

I wish it was in the RR corner of the car...like a lot of the BMW's...it would help to offset some of the L side weight bias...esp with my large *** in the drivers seat

dastallion951

hahaha dannobre well from what i remember besides the optima battery for as far as cca capacity to weight ratio..........there was a battery i believe its called the braille racing battery, supposed to weigh like 10-15 lbs or so.........n supposed to have high cranking capacity, now i dont know the longevity on it so dont quote me, but its supposed to be up there on battery life with optimas.........have u heard of them???

dannobre

iTrader: (3)

Ya...TeamRX-8 has one in his car. There are exceptions to every rule

dastallion951

cool cool........he would be the one to ask about how much it costs...........im takin my car to riverside mazda for before it was an intermitten misfire.........now it happens at WOT im sure the coils r fried.........n im gonna replace the battery soon n wanna reliable one but also wanna save some weight.

swoope

iTrader: (5)

and i just did a google search from stuff copied from you post..

http://www.google.com/search?q=brail...ient=firefox-a

like this is hard!!!

get out of this thread.

good luck.

beers

dastallion951

thanx swoope good lookin out........

jeffe19007

MM, I would guess that the RX-8 has an alternator. i have seen Japanese manuals refer to them as generators before, and I think that they use that as an inexact term, like the Renesis is a 'engine' (don't know why I think that way).

The automotive generators I am familiar with (now I date myself) would not charge at idle. I understand that was the primary reason for a change to alternators in the early to mid 60s.

As to whether the battery is needed and how it is used, may be a design point. That 60 Chevy I had needed to survive on the battery at idle to support the car. Lights would dim, radio would sag etc. Today's cars start even if you have the headlights on. I would not consider doing that on that old Chevy.