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lightweight underdrive pullies


turbopath
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Anyone interested? I've used these on other cars with good results. I've got a CNC lathe lined up to crack out some pullies out of aluminum. I'm going about 20% smaller on the crank pullies. I won't be able to get exact prices until I find some spare pullies to take to the shop. There will be a steel sleeve over the seal end of the pulley as prior experience shows that the front seal can wear out the aluminum.

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I can do whatever someone wants to send me...

I'll get some better price estimates once I can get a pulley down to the cnc guy. There are a few shops around, so I'll take my time and get the best price. The prices drop significantly the more I have made as they have to set it up etc. I'd like to do a set of pullies eventually, like crank, alt, and ps. With my saturn pulley, the aluminum crank pulley weighs something like 4lbs and factory one weighed in around 15+. That's a particularly heavy one because it used weight to dampen noise. It got a little noisier with aluminum, but the crank was still safe. I'm planning on getting some kind of damper on there to keep the aluminum from vibrating on the path. I just haven't decided on a material yet.

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yes it will...plus underdrive pulleys are intended to be kind of a kit and run less power through your accessories via smaller/lighter pullies, therefore robbing less power from your motor. The crank pulley actually has the least to do with the equation.

 

I've been wrong before though.

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The point is to prevent harmonics during operating rpms, so whatever is on the end just has to be able to absorb them. The only engines I've seen grenade were due to extra long cranks in an inline 6 with harmonics that resonated at 7k rpm...exactly where the engine spent most of its time on the track. German precision for ya.

 

The crank pullies make a big difference as a whole because they are what turn the entire assembly. So if you reduce their size 20%, you just slowed down all of the accessories by that amount. Most companies offer just a crank pulley, or a combo of crank, alt, and water pump. The alt pullies are usually lighter and a little smaller to keep it at an ideal speed at idle. I actually gained 8whp on my other car from the pullies and revved just a hair quicker from ditching the 15lb weight on the crank. What I found interesting was removing the belt altogether resulted in lost hp. I'm guessing that alternator cranks out some serious juice. Regardless, I'll let my motor be the guinea pig since I have to replace the t-belt anyway. If it grenades...I'll build another.

Edited by turbopath
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The most memorable way to find out why engineers used the design they did is to do your own "engineering" and see what happens!

ya, so far all I have found is improvements (and then made them) in my other car. Dumb engineers didn't even have oil drainbacks in the pistons... I'm pretty sure I'll get some good results with this.

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ya, so far all I have found is improvements (and then made them) in my other car.  Dumb engineers didn't even have oil drainbacks in the pistons...  I'm pretty sure I'll get some good results with this.

 

 

Weren't you selling your pathfinder because it runs like absolute crap after your mods??

 

 

SOrry guys, Pathfinder VG33's are not meant for ANY type of horsepower.

 

If I were to throw money away, i'd be lighting my blunts with flaming benjamins, not installing lighter pulleys on a Nissan SUV.

Edited by FUELER
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no, that was 98silverpathy...and the vg33 can make a crap load of power. The problem is no one here besides 98 had the balls to do it. If you don't believe me...check out what some RX7 guys have done to the "hopeless" VG33 (they intentionally got the VG33 for the extra displacement over the VG30det.) The hp numbers will surprise you.

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Could that be because pistons aren't supposed to have oil on top of them in the first place?

No, the drainback holes go behind the oil rings...for those who don't know about motors, that's below the compression rings. Without them, you end up burning more oil than you would otherwise. The long hole in the bottom ring of this piston is an oil drainback. The engine would always burn oil with 205 compression on each cylinder =no blowby. It just had nowhere for the oil to go. Cylinder walls and wristpins get oiled either by squirters or the crank flinging oil up to the bottom of the walls...and the oil control rings drag the oil up the cylinder walls. The point of a drainback is to keep too much of it from getting past the compression rings.

21191.jpg

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I don't think it's got much to do with "having the balls" to build an engine for power, it's got more to do with the amount of time, money and work involved. 99.9% of the people out there are only capable of (or willing to attempt) bolt-on work and haven't got the time or money to tear an engine down completely, replacing stock internals and doing a lot of work on an engine that will simply be used in their daily driver.

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