Oreif,
Lest we forget, BOTH of these places are trying to sell the things. 
I have the FS underdrive pulley, the weight difference between it and stock is virtually nil. There might be a few ounces, I didn't weigh them, but the FS one is simply stamped steel just like stock and not aluminum or some other lightweight metal. I'll grant that if the pulley was significantly lighter, you might feel the difference in how the engine revved, but that doesn't necessarily equate to more hp.
The pulley on the 2.8 isn't part of the dampner, so that's a moot point in this discussion which is how much benefit can be derived from underdrive pulleys on the 2.8 in the Fiero?
Well, first you have to determine how much is being used. If the battery is fully charged and there aren't a lot of accesories to load the electrical system, the alternator is drawing very little hp from the engine. It's not quite just an idler, but darn close. If you're at the strip, you can MAKE it an idler just by unplugging it. The water pump draws horsepower in proportion to rpm. I have no idea on what the power required curve for that is, but it won't be linear, it will increase at a higher rate at higher rpm. The question is, how much and how much difference can you have by slowing it down and still maintain adequate cooling at lower rpms.
My experience is, not much.
From your first site, with the dyno results, on the first two they claim a 7-8 hp increase at the wheels. Maybe so, I don't know what all accessories those belts are driving. I know what the Fiero's is driving, though, and it's not much. On the last dyno sheet on that site, they don't even have a "before" sheet, only an "after". On that they guessed at what the stock power was, and then they go on to say that a cat-back exhaust is worth 2-3 hp and an air intake (what that is, nobody knows) is worth 2-3 so THEREFORE their pulley must be worth 11hp? Not exactly empirical proof, IMHO.
On the FastForward site, I tried to find how small the pulleys were, they look smaller than the FS pulleys, but it's hard to tell. The Beretta also has a completely different belt system than the Fiero. Again, these guys are selling their stuff, to me that alone makes their tests at least something to look at with a jaded eye.
The Fiero drives two things that are under load. Water pump that's a fixed load and alternator that you can control by unplugging if you want, at the track. That's it. The point is, there's not much power that's being consumed there and therefore, not much that can be recovered by slowing it down.
I don't think we really have an argument here. UD pulleys can help as much as some claim, on some engines, I just don't see how the Fiero applications in the pushrod V6's are one of them.
John Stricker
| | | quote | | Originally posted by Oreif:
It all matters in the pulley design and the engine. Different engines react differently to changes. In the article they do mention that the "pulley" is part of the harmonic balancer.
Reducing this weight can damage the crank. (and per the article, several BMW's did in fact have crank damage.) The thing about removing the belt is flawed since most performance underdrive pulley's are smaller AND lighter which reduces the inertia.
A smaller and lighter pulley will have the same effect as using lighter wheels. The Fiero belt is only driving the waterpump and alternator, Not a power steering pump, tensioner pulley, and A/C and possible another guide pulley, All with a long belt. The Fiero also differs as the balancer and pulley are seperate parts unlike the Saturn and BMW engines in the article.
Here is a website that has dyno's from a Mustang with the 3.8L V-6 with a 7.8hp increase.
http://www.diaboliqueracing.com/pageasppulley.html And since were talking about using underdrive pulley's on GM 60* V-6's, Here is a place that sells them AND has Dyno'd them on a few 60* V-6 engines including the 3.4TDC and they are seeing 8-10hp gains on the dyno at the high end:
http://www.fastfwdperformance.com/uddyno.htm The fast fwd performance website is very informative on underdrive pulleys on 2.8L, 3.1L, and 3.4/3400 engines. Here are the pulley's they make:
http://www.fastfwdperformance.com/ud.htm |
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