Who here is running an MR2 alternator in their car?

[born2drv]

My alternators in the past have failed several times. I do run an aftermarket stereo however, nothing too crazy but if I lose an extra 10HP to keep everything operating properly so be it. I'd rather have 14.4V of clean juice then just say 13.5. +10HP is only like 0.08psi more boost anyways Since when is a supra efficient?

 

[NashMan]

hey hey umm the drag is the same dude no matter what ampage is coming out of it

talking to shop today about alts and asked about drag said there is no diff at all really in less it freaking cray mo fo one wiht life span of one year

I was being "nice"

If the stock Alt isn't keeping up think of the drag then going to a larger capacity Alt = even more parasitic loss so in the end just how much of that "free power" is left to move the car?

 

[IJ.]

Ryan: If your battery is going flat on a stock alternator it's NOT keeping up with demand and is maxxed out.

You install the Mr2 unit and it keeps up so HAS to be putting out more current, more current = more drag unless the Mr2 Alt is more efficient.

 

[NashMan]

ding ding thsu is why i don't think or plan to get a upgraded small cased mk3 alt

but i going down to the rebuild place this week end he mentioned some thing about a new crazy wind he has close to the same amonte of drag and more amps at lower rpms as well

but gonna find out more when i get down there

 

[Kylar27]

Never understood why people fit electric fans when there is a perfectly good mechanical one fitted from stock. Must be an astehtics thing:dunno:

You can free up a small amount of hp by eliminating the engine from turning the fan. Most cars can free up 5-10 hp

 

[Kylar27]

Ryan: If your battery is going flat on a stock alternator it's NOT keeping up with demand and is maxxed out.

You install the Mr2 unit and it keeps up so HAS to be putting out more current, more current = more drag unless the Mr2 Alt is more efficient.

Not trying to be a smart ass but do you have any facts on how much one alternator "drags" v.s the other, I'd put my money on the difference being negligible.

 

[Poodles]

You can free up a small amount of hp by eliminating the engine from turning the fan. Most cars can free up 5-10 hp

yes, but the amps used to power the electric fans negates this

the ONLY advantages to electric fans is:
- they don't run all the time, so amp draw isn't always on (stock fan clutch does this as well, but not to the same degree

- packaging (used in FWD cars as a traditional fan is impossible)

- can spin at full speed even when idling having more airflow (this is only for HIGH QUALITY FANS, not some ebay crap fans I keep seeing, the stock fan moves TONS of air)

- looks, clearance, bling factor, ect...

 

[turbotrev]

if your running a good stereo just throw a capacitor on it and itll do fine

 

[IJ.]

Not trying to be a smart ass but do you have any facts on how much one alternator "drags" v.s the other, I'd put my money on the difference being negligible.

If the larger capacity alt is supplying more current than the smaller one it has to have more drag......

Is this such a hard concept to grasp?

 

[Larry_A]

If the larger capacity alt is supplying more current than the smaller one it has to have more drag......

Is this such a hard concept to grasp?

Never give up, never surrender!

 

[Poodles]

IJ needs a bigger hammer...

 

[IJ.]

Never give up, never surrender!

 

[Kylar27]

If the larger capacity alt is supplying more current than the smaller one it has to have more drag......

Is this such a hard concept to grasp?

Like I said, its not that I dont believe you, but where is your proof? Got any numbers to back up your theory?

 

[Kylar27]

yes, but the amps used to power the electric fans negates this

the ONLY advantages to electric fans is:
- they don't run all the time, so amp draw isn't always on (stock fan clutch does this as well, but not to the same degree

- packaging (used in FWD cars as a traditional fan is impossible)

- can spin at full speed even when idling having more airflow (this is only for HIGH QUALITY FANS, not some ebay crap fans I keep seeing, the stock fan moves TONS of air)

- looks, clearance, bling factor, ect...

I have seen articles where they dyno a car before and after. There was a small like 5-10 hp difference. Where is your proof that the amps used to power the fans negate the power gained from removing drag on the engine.

Does anyone have any proof besides just saying it is so?

 

[figgie]

Not trying to be a smart ass but do you have any facts on how much one alternator "drags" v.s the other, I'd put my money on the difference being negligible.

it is fact

basic alternator function

the stator field is not constant instead it is being adjusted by the load it is seeing (Hence why you have the round plug in the back of the alternator). So if the alternator has a higher current capacity it is not magically coming from no where. The input current to make the higher stator field has to be greater this mean there is more load on the alt. Period.

Read up

http://www.autoshop101.com/forms/h8.pdf

I will quiz you on it later on.

BTW this is from Toyota and not so willy neely drive by night shop.

 

[figgie]

also to add

this really is SIMPLE physics.

no even taking the magentic field portion into consideration at first.

There is drag on the engine to spin the alternator. Why? The Rotor has mass. An alternator that has a higher amperage has a bigger rotor which means more mass = more drag since in the real world means the bearings are seeing more weight and friction increases thereby taking more power to overcome. THis is the mechanical part.

On to the electric portion.

Having an alternator of a given size (say 50A) causes a load on the engine because the minute the magentic field on the stator comes online due to the battery voltage, it presents a load on the engine (get a magnet and a piece of iron for example of a load). Increase the amperage to 100A by rewinding the coils, now you have essentially doubled the load the stators exherting on the rotor.

NOTHING to include engines comes with free anything. The energy must come from somewhere and in this case it is the engine.

 

[Poodles]

I have seen articles where they dyno a car before and after. There was a small like 5-10 hp difference. Where is your proof that the amps used to power the fans negate the power gained from removing drag on the engine.

Does anyone have any proof besides just saying it is so?

simple, the fans didn't kick on on the dyno, and they usually don't use any serious fans that flow even close to what the stock fan on our car will flow at idle...

 

[3p141592654]

The equation is simple:

Divide the fan power (Watts) by the alternator efficiency and you have your drag in Watts (convert to HP by dividing by 746 W/HP).

 

[3p141592654]

By the way, a typical Lundell type auto alternator has an efficiency of 40 - 50 %.

 

[Kylar27]

Some very good points here. I like to play devils advocate sometimes so dont take anything personally. Its good to look at both sides of a topic.

I still think it would be interesting to see a dyno sheet with some real numbers so we can find out how much "power" the bigger alternator actually steals.

edit: Yes I realize one of you is probably going to throw out some formula to calculate the difference, but I would rather see it on the dyno. Then you know for sure how much real world hp was sapped.