Originally Posted by justnspace

that's my signature! lol

and you wont gain horsepower from a 1lb pulley. not sure what the accords were using, but here the 3g and 4g's have been using the XLR8 1lb stock diameter pulley for more than 10 years. but we've done the math and there's basically no gains from a 1lb pulley.

Originally Posted by justnspace

yeah, the car will rev up faster!
and I couldnt tell you if that's worth it for you, only you can!

Originally Posted by echodigital

I was thinking about the this part - I don't know if it's the same as you mention in your post....

https://acurazine.com/forums/4g-tl-p...pulley-943379/

Originally Posted by JakeF

That's one of the threads I read about it. There were a few on the accord forums too and a few comments by the guy who posted this video that talk about noise with the AC after adding the lightweight pulley. Faster revving and less driveline weight sounds good but a whining AC doesn't.

Originally Posted by Hyphology

A few people have the stock size lightweight pulley and thinks it's worth it and have had no issue. The j is internally balanced as well.

Originally Posted by Cross-Hair

You bring up a lot of good points. Some of which I can address, some of which I'm probably not fit to. I want to explain that I'm a mechanical engineer not an auto expert. The calcs were simply there to show what results a lightweight pulley COULD create (a theoretical maximum) and wrote a little disclaimer near the end saying that actual results would most likely be lower.

As far as the CAI and TB spacer... that's not really the point of my post. You could say the same thing of driving your car on cool night and it feels like a beast, then you install the CAI/TB spacer and drive the car on a hot, humid day and it feels like you actually lost power. The point of this was to show that regardless of the butt dyno showing different results as different times, the calcs show that you should see an increase in performance (all other things being equal of course).

On to the reving speed... It's really a question of kinetic energy to tell you the truth. I'll use a linear example to show my point (easier to understand than rotational).

Does it take the same energy for a car to go from 0mph to 20 mph as it does to go from 20mph to 40mph? Not having experience with a car, most people say "yeah, it's just a 20 mph difference." But it actually comes down to kinetic energy.

Ek = 1/2*m*v^2

That's half of the mass times the velocity squared. So in each case (0-20 and 20-40), mass is the same so I'll leave it as a variable. To calculate, you take the kinetic energy at the final speed minus the kinetic energy at the initial speed.

Ek.0-20 = 1/2*m*(20^2)-1/2*m*(0^2) = 200*m

Ek.40-20 = 1/2*m*(40^2)-1/2*m* (20^2) = 700*m

So the ratio actually shows that it takes 3.5 times the energy to go from 20-40 as it does from 0-20. This can drastically be seen if you take a look at a car's 0-60 time vs it's 60-120 time (though at these speeds drag is also heavily at play since it's also based on velocity^2).

This concept applies to the car in the same way. The engine actually takes more energy to accelerate at higher rpms. And while more fuel is dumped to account for that energy, there is a limit. Try it in a more noticable (slower) gear like 4th or 5th on a highway. You'll notice that accelerating (at higher speeds) will show a quicker rev near the lower rpms and a slower rev near the higher rpms. Again, this is from a mechanical point of view and the car in practice might actually be able to supply enough energy (fuel) to keep the rise linear, but since the energy required is the square of (angular) velocity, it would quickly need to start dumping pretty significant amount of fuel.

The undersized pulley actually makes a fairly small difference believe it or not. As far as moment of inertia, it's a 15% or 20% radius reduction. While this will result is a decently lower moment of inertia (since radius is squared) your required power/torque is already so small that at most it will make a ~0.5lbf*ft of torque difference. Again, percentage wise it's decent... but nothing you'll even notice.

As far as driving loads, that is actually not as helpful as you might think. If you've played with an alternator assembly and you give it a quick spin, it will free-spin for ~30s. The bearings reduce friction and it's a magnetically coupled device (friction being very minimal). While it's true that as it generates energy, the magnetic fields will actually resist its spinning, it should be fairly minimal for the power it provides. As far as the A/C, as far as I know it's similar to a clutch-type setup (please correct me if I'm wrong). Meaning that if the A/C is off, there is basically no load on the engine from it. You probably shouldn't be racing/sprinting with your A/C blaring anyway. It's easier to press the "OFF" button rather than get a smaller pulley.

I really can't speak for the pump because I'm not 100% familiar with the in-and-outs of how the car responds to load changes in the power steering pump. Sorry, maybe someone else can shed some light on this.

Again to re-state this, it was merely just to show the mechanical power that would become available from a reduced pulley weight. This will also effect several other things I haven't even included in the original post. Theoretically, the lighter weight would also allow the car to rev-match faster and thus shift faster (though again, not 100% sure how the car reacts in actuality). On the downside a heavier rotating mass actually stores more kinetic energy which can be utilized and beneficial ways. A fly-wheel for instance can stores extra energy that makes for a stronger launch. Again, there are a lot of things I haven't included (and probably even more that I'm not aware of), but this was just strictly to show the math/science and what the pulley can achieve.

That being said, I'm not trying to sell this product by any means. Personally, $$/hp, it seems like the J-pipe is still a better (first) buy since it's more linear with rpm/load on the engine (constant gains regardless of which gear you're in) as opposed to the crank pulley which has progressively worse results as engine speed and gears increase.

Hope this cleared some things up. Again, let me know if this wasn't very clear.

Originally Posted by justnspace

here's the math involved:
https://acurazine.com/forums/3g-tl-p...g-read-790020/

I trust the calculations and it shows that 1st gear will gain the most and every gear after that, gains diminish.



basically, at the price point it's not worth it.

Originally Posted by CruzanTLSH-AWD

Basically what my tuner said.

Originally Posted by JakeF

What mod's are worth the price according to your tuner?

Originally Posted by CruzanTLSH-AWD

I don't have the FWD but I have seen guys with the V6 Accord hurting feelings with the ZDX intake manifold and TB. You can also find cams for the J35 as well. I would make those investments along with being fully bolted on. It seems with a tune guys with the K&N short ram makes gains as well BUT you need a custom tune accomplish to gain that potential.

Here is the link to the one of the upgrades https://www.heeltoeauto.com/intake-m...dswap.j37.html

also getting your lower intake runners port and polish ain't a bad idea.