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Old 02-06-2019, 08:00 AM   #1
Pafar
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Default WRX Low battery CCA

Searched and was unable to find anything on this.

I have been hunting a misfire on my 2001 wrx for the last few months. Its only really noticeable in boost. No CEL. So far I've replaced my injectors, fuel filter, spark plugs, tuner has checked coil packs and they are all good (not sure how he checked them, only know that he said they aren't the problem.) Ive had a quick check for boost leaks but the car still pulls hard just intermittently, as if its slightly jerking. The car was protuned with this slight misfire as i ran out of money on dyno day due to other issues.

I was looking around the engine bay today and noticed that my battery is only 330CCA. It starts the car ok, but could it be the culprit of the misfire? Also will changing the battery to one appropriately sized (I'm thinking like 650CCA or so) mess with the tune at all? Any insights appreciated. Thanks!
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Old 02-07-2019, 02:04 PM   #2
jkm5164
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Whats the battery reading? I don't believe you will get misfire because of a low battery. You can get all sorts of weird CELs that usually say things like "low reference voltage". I just got all these random CELs when it was very cold the other week. Battery was super low. Replaced it and it solved all the issues.
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Old 02-11-2019, 11:27 AM   #3
hrbutler52
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With the engine running, the alternator is supplying all the needed power, if it is working. A battery with more CCA will only make the starting easier. It will have no effect on your tune.
Check the voltage at the battery with the engine off and with it running. Running should be 13.5+V. Not running approx 12.5V for an fully charged healthy battery.
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Old 02-11-2019, 12:39 PM   #4
gagg maggot
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Default

Quote:
Originally Posted by hrbutler52 View Post
With the engine running, the alternator is supplying all the needed power, if it is working. A battery with more CCA will only make the starting easier.
This is an overly-simple and incorrect explanation.

The battery is your power supply and buffer. Your car electronics are made to run off of the battery, period. The alternator is just there to keep the battery charged. Your alternator is also sized to run with a specific size battery, running a smaller battery will eventually cause more wear and tear on the alternator and fry it just like running an oversized alternator without the appropriate load will eventually fry the alternator. Having a short in your battery or a bad cell will also fry your alternator, although it will do it faster.

It's entirely possible that the small battery is causing your misfire. Even if it is not, I would get it swapped out ASAP regardless. 330CCA batteries belong on motorcycles.

It also wouldn't hurt to inspect all of your grounds and power cabling for corrosion / bad contact.
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Old 02-14-2019, 02:35 PM   #5
TXwrxWagon
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no no no no no!!!!

One caveat to the following: vehicles since approx 2008 have CAN Bus micro-controlers that need specific voltage and resistance signals to properly function and those are outside the purpose of this discussion. We are Discussing a 2001 WRX (obviously EDM, JDM, or AUS) this is a generalization of the vehicle charging/operating system.

__________________________________________________ __________________

CCA = Cold Cranking Amps , This has ZERO to do with an engine running. A big compression engine (13:1-on up aka diesels, high hp race cars) need high CCA's to drive the starter to get past the compression stroke. PERIOD!!

that is why lower CCA's are reserved for smaller amperage draws. IE lawn mower, motorcycle, etc. Nothing to do with combustion engine performance.

Ever wonder why old race cars had that weird looking machine that they attached to the crank at the starting line with huge cables running to a battery cart? Yep.. Battery not needed.

The battery's ONLY responsibility and use is to store enough power to turn the engine over enough past the compression stroke to fire and run. PERIOD. the alternator and ignition work together at that point to keep the engine running.

Any automotive/motorcycle/combustion engine powered vehicle can and will run TOTALLY fine with the battery disconnected after starting. Not recommended for sensitive CAN and Electronic control modules, but the car will run totally fine w/o a battery.

This is a tried and proven way of for sure testing for a shorted battery or a dead alternator in the field:

jump/start the car. Carefully disconnect the POSITIVE cable from the battery (effectively removing it from the vehilce) the car will run just fine. If it fails, the alternator is not producing enough amperage to supply the vehicle's needs nothing to do with the battery. End of story.

Alternate test. Disconnect and remove the battery and attach an adequate jumper pack to both the POS/NEG cables and the car should and will start. Take the jumper pack off, once started. no battery, no jumper pack, it should and will run. Assuming the grounds, alternator and overall system are in check. Again nothing to do with the battery itself.

As long as the alternator is producing adequate voltage AND amperage for the current requirements and all grounds are adequate, no battery needed.

AMPERAGE is what is of concern. Voltage is an indicator the alternator is producing 12.3v-14.4v. Amperage is the draw of each circuit. So when adding stereo, lots of auxillary lights etc requires a bigger ALTERNATOR not more batteries. More batteries are more loads.

Now all that said.. IF and its a huge, quantum leap "IF", the battery has a intermittent short in a cell, poor connctions internally, yes the battery could be the cause. But it has NOTHING to do with battery rating or application. And the problem would immediately be shown by removing the battery from the situation. Again, not a function of battery rating or CCA's.

Think of it this way: a DeWalt or Milwalkee 12v cordless drill battery will turn on the iginition of a car. It will. Maybe for a minute, it has the voltage, not the amperage.

This is the sinlge most misunderstood system on the modern automobile.

More proof: power flows from the NEG to POS. Not POS to NEG. Let that soak in a second.

Meaning, The power is effectively sucked or drawn to the ground side of the circuit. This is why people are so amazed when they take a production "performance car" and upgrade the ground cables and power cables (sometimes called the "Big 3") and the lights are brighter, the car starts easier. Many cars improve MPG and even HP/TQ. Documented and proven. Remember: a production car is only as good as what the accountants allow them to spec to build it. that 6ga battery cable may not seem like a big deal, but $.67 more for 4ga cable and terminals times 500,000 cars adds up.

If you take a battery/alternator with a 0/2ga welding cable + cable (the size of an adult male's thumb) and then put a 10 gauge - cable. The 10ga cable will fry instanly trying to pass the current. Flip it. an 6ga or 4ga NEG ground cable can support a smaller 8ga POS cable. Not right, and not ideal. But it will work.

To the original post:

car off: measure battery voltage, should be 12.3v or higher.

car running: battery voltage should be 13.8v-14.4v not higher than 16v. Overcharge is just as bad as under.

If it passes the 2 above tests. either the battery or grounds (most likely) or various electrical connections.

Last note: I have recently witnessed a starter that showed no signs of going out, no signs of weakness, drawing residual power at all times and causing a misfire. Its totally a fluke (bad pun) but the problem was solved by checking grounds and found that the starter was essientially grounding out the coil side of the engine. Sucking power away from the driver's side coil packs.

~Rob
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Old 02-14-2019, 02:41 PM   #6
TXwrxWagon
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Quote:
Originally Posted by gagg maggot View Post
This is an overly-simple and incorrect explanation.

The battery is your power supply and buffer. Your car electronics are made to run off of the battery, period. The alternator is just there to keep the battery charged. Your alternator is also sized to run with a specific size battery, running a smaller battery will eventually cause more wear and tear on the alternator and fry it just like running an oversized alternator without the appropriate load will eventually fry the alternator. Having a short in your battery or a bad cell will also fry your alternator, although it will do it faster.

It's entirely possible that the small battery is causing your misfire. Even if it is not, I would get it swapped out ASAP regardless. 330CCA batteries belong on motorcycles.

It also wouldn't hurt to inspect all of your grounds and power cabling for corrosion / bad contact.
more specifically incorrect: any modern alternator is usually internally regulated to providing 2 things.

1. amperage to cover what is on/running
2. what the battery "requests" to charge.

Your description above would mean that a modern Cell Phone "Fast charge 2.0" wall cube would burn up a standard battery in any given phone. Not the case. It simply provides what is demanded.

To take ita step further:

Ever had the alternator belt on a car shred and you need to get 15 ore miles to a safe place or home? Turn off the headlights, radio, drop the windows, turn off a/c etc. conserve power. The battery can only hold out so long.

Same applies to low fuel: if I am cruising at 75mph and see I am low on fuel, if I back off the gas to 50mph I'm more likely to make it to the station. Gas tank only has so much fuel.

~Rob
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