Underdrive pulley

[Petrus]

I live in the sunny south of Europe, hardly ever have the fan on at all, don´t have much lights on either and no sound system fitted.
As such I could do with an ´underdrive´ (i.e. larger) pulley on the alternator.
A smaller pulley on the crank would dictate a smaller waterpump one and has less traction so better not.
Anyone fitted a diferent alternator pulley?
Any EU (UK) source for one?

[Carolyn]

Yes but.  The power required to turn the alternator varies with the load.  The bigger the load (served by the battery), the harder the alternator works to keep the battery up.  Can't see a massive advantage to a bigger pulley.  Not like a supercharger....

[Petrus]

Yes but.  The power required to turn the alternator varies with the load.  The bigger the load (served by the battery), the harder the alternator works to keep the battery up.  Can't see a massive advantage to a bigger pulley.  Not like a supercharger....

Totally true.

Regardless of the load though is the weight of the rotor. The lower the reduction, the lower the power spent on speeding it up.
I have not measured the diameters but it lóóks like the generator  turns about 3 times crankshaft speed and it is  not a lightweight thing.
Slowing it down basically has a comparable effect to taking some weight off the flywheel.

It would have no effect at constant speed.


p.s. how much does the rotor weigh? 3 kg.?
Although the diameter is small, it doés need to be sped up.
I would quite like to slow it down some 30% at least.

I find it surpring there is so little availeble.
The MWR I would prefer to avoid;  tax/shipping plus it is US made. 
An Italian tuner offers one for 100€ and that is a bit steep.

[Petrus]

Done some rouh calculations and I think it worthwile.
A véry simple modifacation which would not even need a belt change yet ís effective.
The only negative is that it will raise the (engine) revs of max output of the generator.

Asked Boris if he could look into it.

Meanwhile found reasonably priced ones accross the atlantic but with taxes and shipping it becomes silly for a simple pulley.

While Boris thinks about it will ask around locally.
If possible I´d prefer to support the car club source because of the nature of that.

One obeservation:
It is claime that it gives apower gain with evidence by a dyno-bench. Yes that is true BUT no, it does not give more hp. The dyno-bench is an acceleration-bench which then calculated the hp generated. Because the engine needs to accelrate less mass it will thus ´measure´a power gain.  If it were a bráked bench it would not give any gains.
So no, it does not increase output but it will make the engine more lively AS IF it has 3, 4 hp more.. Again, like a lighter flywheel but without the negative in the way the engine runs or the stall chacteristcs.
Considering how difficult it is to squeeze extra hp from the n.a. 1zz I am going for it.

[105e]

If the pulley was 3 foot across then yes i could see it,or if the engine was only 50cc,  but something so small on a 1.8 i just cannot see that either the car or driver would notice any difference.

[jonbill]

If the pulley was 3 foot across then yes i could see it,or if the engine was only 50cc,  but something so small on a 1.8 i just cannot see that either the car or driver would notice any difference.

I agree. And i haven't weighed it, but no way is the alternator pulley 3kg. 300g maybe. I'd put a tenner on it

[Nvy]

Alternator pulley is so small that you cant care less for it. 5cm diameter tops. Id guess it weights nothing. If you want to do such mod you can replace 1zz water pump with 2zz water pump. It does the same you explained, needs to be driven less times to deliver the same performance.

[Carolyn]

It's not the weight of the pulley that Petrus is concerned about.  It's about maki ng it easier to move the inertial mass of the alternator rotor, (which is a chunky bit of kit).

However.  The idea that reducing the inertia of the overall engine package is not the same as lightening the flywheel, doesn't hang together for me.  Anything that makes the engine spin up quicker, also makes it spin down quicker.

I know you are one for 'marginal gains', Petrus, but I think I'd find this margin hard to justify in terms of expense and work vs a very marginal return.

Each to their own though.

[105e]

It's not the weight of the pulley that Petrus is concerned about.  It's about maki ng it easier to move the inertial mass of the alternator rotor, (which is a chunky bit of kit).

 Yes buy you can spin it up with your fingers pretty easily and as he says very little electrical load to make it harder.

[Petrus]

However.  The idea that reducing the inertia of the overall engine package is not the same as lightening the flywheel, doesn't hang together for me.  Anything that makes the engine spin up quicker, also makes it spin down quicker.

The difference is the ´rubber band´ it is attached to.
Where the flywheel is bolted to the crankshaft and thus equalises small variations caused by the stroke phase and con rod/crank angle, the rotor has a long stretch of rubber attaching it. To put it is other more direct words: The flywheel pushes the pistons through the compression, the rubber band will give.

So the effect on acceleration/decelleration is comparable with a lighter flywheel but the effect on the smoothness of the engine is not.
Thus comparable advantage with a bit less of the downside.

The chunky bit of kit will be spun up to less speed = sapping less energy = making the engine just that bit livelier without lowering the stall speed a lot.
The compromise I was looking for when looking at lighter flywheels.
Again; nothing more or less than reducing the effort to spin up the chunky bit of kit which is the rotor.

Remember that this rotor is spinning at thréé times crank revs! The force needed to accellerate it, to put the kinetic energy in, is to the power of that.
Yes it also deminishes that load on the belt.

[Petrus]

I know you are one for 'marginal gains', Petrus, but I think I'd find this margin hard to justify in terms of expense and work vs a very marginal return.

It will do more than taking the sound system out and I thought/think that worthwhile too ;-)

[jonbill]

It's not the weight of the pulley that Petrus is concerned about.  It's about maki ng it easier to move the inertial mass of the alternator rotor, (which is a chunky bit of kit).

However.  The idea that reducing the inertia of the overall engine package is not the same as lightening the flywheel, doesn't hang together for me.  Anything that makes the engine spin up quicker, also makes it spin down quicker.

I know you are one for 'marginal gains', Petrus, but I think I'd find this margin hard to justify in terms of expense and work vs a very marginal return.

Each to their own though.

He did state the rotor weighs 3kg and needs to be spun up!
Although indonalso agree with your objection.

[Petrus]

Although indonalso agree with your objection.

She does not object. Just differs in opinion about whether it is worth it the effort. That can and will be said by most people, even enthusiast, about a lot of my efforts and it misses an important point: For mé a lot of the fun is in the figuring something out, the tinkering, the modding itself already and if it has ány positive effect, then that is a bonus.

Also; a lot of little things do add up to a big thing: No, taking the seakers out of the doors  definitely makes no noticable difference BUT my car is some 150 kilos lighter now and that is just as definitely quite noticable. Worth the effort? That is beside the point; it makes mé smile :-)

Bottom line is that no, no first hand experience here and no, no ´local´ source.

[jonbill]

Although indonalso agree with your objection.

She does not object. Just differs in opinion about whether it is worth it the effort. That can and will be said by most people, even enthusiast, about a lot of my efforts and it misses an important point: For mé a lot of the fun is in the figuring something out, the tinkering, the modding itself already and if it has ány positive effect, then that is a bonus.

Also; a lot of little things do add up to a big thing: No, taking the seakers out of the doors  definitely makes no noticable difference BUT my car is some 150 kilos lighter now and that is just as definitely quite noticable. Worth the effort? That is beside the point; it makes mé smile :-)

Bottom line is that no, no first hand experience here and no, no ´local´ source.

Sorry, I meant objection as in argument. I do understand you do this because it pleases you. We all do I think.

[Petrus]

Sorry, I meant objection as in argument. I do understand you do this because it pleases you. We all do I think.

Thank you; I am not as finely tuned to the finesses of synonyms as you native speakers ;-)

Meanwhile found a source for Ralco RZ pulleys in the Netherlands.

Sent them an email. Might give it a go.

[Alex Knight]

I'm using the MWR Underdrive pulley in my 2ZZ:

https://www.monkeywrenchracing.com/product/mwr-underdrive-pulley-lotustoyota-2zz-water-pump/

[Petrus]

I'm using the MWR Underdrive pulley in my 2ZZ:

https://www.monkeywrenchracing.com/product/mwr-underdrive-pulley-lotustoyota-2zz-water-pump/

Thank you for responding Alex and for the link.
Do you notice a difference?

[m1tch]

I looked at underdrive pulleys on other cars, they work mainly for the waterpump to stop cavitation at higher RPMs, if you live in a very cold place you should be able to get away with town driving and lower RPM driving with an underdrive pulley.

Basically fit one if you are always above 6k rpm or live in a cool enough country that you don't need a huge amount of flow.

Another option would be to simply not run a mechanical water pump and run a Davis Craig pump.

[Carolyn]

Others will correct me if I'm wrong. (They always do!!)

BUT

I'm pretty sure the 2ZZ water pump does not fit the 1ZZ.

[Petrus]

I looked at underdrive pulleys on other cars, they work mainly for the waterpump to stop cavitation at higher RPMs, if you live in a very cold place you should be able to get away with town driving and lower RPM driving with an underdrive pulley.

Basically fit one if you are always above 6k rpm or live in a cool enough country that you don't need a huge amount of flow.

Another option would be to simply not run a mechanical water pump and run a Davis Craig pump.

That is the waterpump or the crank pulley yes.

A smaller crank pulley would also spin the ac pump (if fitted) less.

Indeed it does not Carolynne. Ditto waterpump pulley; is different. Ditto crank pulley; the 2ZZ has a harmonic balancer and fitting a solid aluminium one is not a good idea. No such issue on the 1ZZ. That being as it is, fitting only the alternator one avoids any problems with either crank or waterpump ;-)

[Alex Knight]

I'm using the MWR Underdrive pulley in my 2ZZ:

https://www.monkeywrenchracing.com/product/mwr-underdrive-pulley-lotustoyota-2zz-water-pump/

Thank you for responding Alex and for the link.
Do you notice a difference?

Hard to say, as I had the engine out to do a lot of maintenance & upgrades at the same time.

I'd be amazed if anyone could notice the back to back difference though.

I only fitted it to reduce the chance of any potential high RPM cavitation, as I do a lot of track days.

[Petrus]

Have ordered the MWR alternator pulley from a Dutch distributor:

https://www.rideround.nl/shop/3-341-929/mr2-multiriem-systeem/mwr-underdrive-dynamo-pulley.html

Slows the alternator down with only 25% so it should not give electrical issues and is probably not noticable but hey, the n.a. 1ZZ  has no excess horses so marginal gain it is.
The equivalent of 2 kg. off of the flywheel with less of the stall issue.

[jonbill]

Have ordered the MWR alternator pulley from a Dutch distributor.

Slows the alternator down with only 25% so it should not give electrical issues and is probably not noticable but hey, the n.a. 1ZZ  has no excess horses so marginal gain it is.

Won't the 1zz struggle at idle with a 25% underdrive alternator?

[Petrus]

Won't the 1zz struggle at idle with a 25% underdrive alternator?

Struggle with what or in which aspect?

[jonbill]

Won't the 1zz struggle at idle with a 25% underdrive alternator?

Struggle with what or in which aspect?

I mean not output a higher voltage than the battery, so the car will be running off the the battery not the alternator at idle and the battery light will come on, no?