Looking to get a set of underdrive pulleys for my 4.6L, witch set is better then the next and what is the cost up front. And will i get any MPG for putting them on? Thanks!

 

I have the set Troyer sells but I have yet to install them. They're dyno tested and proven to produce more horsepower, improve fuel mileage and give better throttle response. They were $225. I don't know what year you have, but if it's a 2002, they changed the amount of ribs on the pulleys mid way through the year so you have to check if you have 6 or 8 ribs on your pulleys.

2002-2008 F-series and Expedition w/8 ribs

1997-2003 F150 w/6ribs

 

I have a 98 with a 4.6L. are all underdrive pulleys the same? as in mustang 4.6 to f150 4.6 to Expy 4.6. And is there one company better then the rest, or is it like tires, pick what you like and have the money for?

 

Like tires to an extent. Some kits have 3 pulleys while some have 2 (no alternator.) The it Troyer sells has 2. I prefer 2 because what you're doing is changing the size of the pulleys to reduce the unnecessary drive of the accesories such as the power steering and the alternator. If you change the alternator, you're adversely affecting what you're trying to accomplish if that makes any sense. The alternator is going to spin at the same ratio (or close to) to the crank as it did before. Defeats the purpose. If you do a search, someone did an entire write-up of their Summit Underdrive pulley install on their Expedition, though I don't remember what year or engine. I think his only problem has something to do with the having a short vs long waterpump. He ordered the wrong one. I believe Troyer's kit is the ASP kit or something like that. As far as the Mustang's 4.6 compared to the F150 4.6, I have no idea, but the same motors to carry over from the F150 to the Expedition.

 

This write up by waterman?
https://www.f150online.com/forums/sh...d.php?t=316722

Also got the same kit (from Summit, 159+10 shipping), just still haven't installed the alternator pulley on.

BTW, it seems that the 2003 4.6 Expedition has a long style water pump, even though on the Summit site it says they are short style.

 

If i understand you a 2pulley kit is better than a 3pulley kit?

 

In my opinion.

 

Thank for all the help, now i can plan to get them soon.

 

I was digging around for that Summit Under Drive Pulley thread and came across a good explanation of what I was trying to say before...


Okay and I finally found the thread I was looking for. It was an 03 Expedition with the 4.6. Summit Racing UD Pulley Install W/Pics

 

Ok, I'm confused about the water pump and alternator pulley thing.

Let's assume you have a 2 pulley system, the crank pulley, and the water pump. So changing the crank pulley goes smaller. Now if I remember from middle school tech class, little pulley driving a bigger pulley makes the bigger pulley go slower, but it takes less force to drive it. Wouldn't putting on bigger water pump pulley make the "big pulley" even bigger, underdriving the water pump even further?

Kinnda like on a 21-speed bike. Assuming the pedaling gear (crank pulley) is on the biggest gear, and the back wheel gear (water pump) is on the smallest gear. Putting on a smaller crank pulley would be like shifting the pedal gear to the smallest one. The back wheel (water pump) spins slower, but it takes less effort. Now putting on a bigger water pump pulley would be like shifting the back wheel to the biggest gear. The back wheel goes even slower, but it takes even less effort to spin it.

Maybe I'm understanding it wrong? Another benefit would be you don't have to buy another belt

 

My brain hurts.....

 

hey i have a 3 pulley set from MAC, brand new. i might be parting with in a couple months...

 

It took me a little while to figure out just what EXACTLY you were saying but I understand it now. The only pulley that changes other pulleys is the crank pulley because it's the driving force. It slows everything else down. Once you change the water pump pulley, you're returning only the water pump to it's original ratio. The alternator is not effected because the water pump pulley isn't driving the belt, but rather only riding along it. The belt is still spinning with the crank, therefor spinning everything else at the same speed. If you put a smaller pulley on the water pump it will keep it it's current speed. If you put a bigger one on, it will speed it up because each rotation is covering a larger distance than before but the belt remains the same speed, therefore the alternator remains the same speed. If you took that 21 speed bike and somewhere between the wheel gears and the pedals gears, threw another small gear out there in between the two, the small middle gear is always going to retain it's same ratio with the crank (pedals.) Follow? It makes sense in my head.

 

LOL, sorry my post made sense in my head as well.

Hmm, I'll try again.

First a little picture. Again, this is assuming this is a two pulley system.


Number 1 in the picture is stock. For simplicity, let's just say that crank pulley (C in pic) and the WP pulley (W in pic) are both 1 inch in circumference, so a 1:1 ratio. For every turn C does, W does one turn.

Number 2 in the picture would be if you just change the crank pulley to a smaller one. So now, instead of being 1 inch, it's half an inch. So, the ratio is 0.5:1. For every turn the C pulley does, the W pulley does half a turn (0.5/1=0.5, small pulley driving big pulley = slow moving big pulley) Basically, this is the situation that happens to all other pulleys driven by the engine, like the power steering and the alternator (again, assuming that you only get a 2 pulley system.)

Number 3 in picture would be if you change the crank pulley to a smaller one than stock, and change the WP pulley to a bigger one than stock. C pulley is 0.5 inches and WP pulley is 1.5 inches in circumference, making the ratio 0.5:1.5. For every turn the C pulley does, the W pulley does 0.333 turns (0.5/1.5=0.3333) thus it is further slowed down, and it takes less force to turn it.

If you were to want to bring the WP pulley back up to stock speed, you would have to make it 0.5.

This is what I was trying to explain using the bicycle as an example, but I've never been too good at explaining things.:o Hopefully I did a better job this time.

 

My mistake came with thinking that the water pump pulley was also smaller to return it to stock. I'm still not sure that that isn't true. Your explanation would be correct I believe. A smaller crank and a bigger water pump would make the water pump turn even slower and not return it to the stock ratio. I thinking I definitely read something wrong in your post before. I could just go measure my pulleys tomorrow at work and then measure my pulleys on the truck to see the difference. I don't see why the water pump pulley would be bigger to return it to the stock ratio. That doesn't make sense to me.

I tried to get info off of ASPs website because I believe that is the kit Troyer sells, but all it says is that it's 25% Harmonic Dampner 26% Water Pump.