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YOUR RESEARCHInstalled Tarett Underdrive pully...
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Install so i don't have a baseline
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I've got a cargraphic on my car that the PO installed so I don't have a baseline but I wouldn't remove it.
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If a 3% change in power really changes your life, I recommend also always running with an empty fuel tank.
Replace dynamics and how the car delivers the power
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Also we have been talking about the fact that it does not make more power but changes the dynamics and how the car delivers the power.
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If a 3% change in power really changes your life, I recommend also always running with an empty fuel tank.
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I'd say it makes the car feel more responsive, sounds like the same debate of a LWFW not making power but changing the way its delivered.
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You're running all the other accessories at a lower speed, so they are doing less work, so the engine has more power available to devote to the wheels.
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As the title suggests I installed this pulley today.
http://www.tarett.com/items/996-997-...erp-detail.htm
I was originally going to do it while I had the engine out and was doing a bunch of other work, but decided I had bitten off quite enough at the time and didn't want to add to any potential trouble shooting after the fact. Needless to say that once I had everything sorted (CEL finally went off) and the RSS guy posted about a sale on the underdrive pulley I decided to give it a go. The problem with the RSS pulley was price - once adding in the pulley, new bolt and the new belt, even with the 10% discount it was more expensive than the Tarett (actually:**Please note this part is manufactured by Eisenlohr Racing Products**). In any case, everything I've gotten from Tarett has been top notch and their service is terrific so, they got the nod - nothing against RSS...
Long story short, I'm really happy with it. The car just seems to take off so much easier/smoother and gets up and goes a little quicker with what seems like less "drag". It doesn't feel "more powerful" per se, just smoother - definitely worthwhile! The only caveat being that if I want to lock the crankshaft for any reason, I'll have to remove the UDP and put the stock one back on (the smaller pulley blocks the boss where the locking pin goes) - hopefully I won't have to do that anytime soon
I watched a vid on YouTube with a boxster, zero horsepower gain.
also remember you are under driving your water pump and some of the block paths have low flow even stock, underdrive risks even more hotspots..
"file" would be a gross understatement. You have to cut off at least a 1/4" of the boss, and then grind a little more for the pulley to lie flush against the end of the crank. It's a very close fit. You'll also need some kind of small right angle tool to do this mod with the engine in the car. A Dremel tool won't fit and a full size electric grinder won't either. I wound up using a small right angle whistle grinder and it just made it.
As for under-driving the water pump, I haven't heard of any problems with that, but it's certainly something to keep an eye on...
Only on tick over - once you are up and going not much difference - plenty conversation here by folks who have used them.
https://rennlist.com/forums/996-foru...-pulley-2.html
+996 on not hearing or reading about any under drive issues. They have been around for awhile and the issues would have surfaced by now.
I've got a cargraphic on my car that the PO installed so I don't have a baseline but I wouldn't remove it.
Could a Boxster really be a good comparison? 2.7 (or even as S at 3.2) vs. 3.4 or 3.6
I'd say it makes the car feel more responsive, sounds like the same debate of a LWFW not making power but changing the way its delivered.
Power gain is a misnomer. You are freeing power that would other drive the ancillaries. It's a mathematical certainty that if you use x% less power to drive accessories, that % power is available at the wheels. Anyone who argues that is a f******g dunce.
The Tarrett UDP is the ONLY mod in ~20ish years of modding cars I will go on the record as vouching for...well, that and a $10k roots blower y'all would not be interested in.
This thread is a marketing agent's dream!! "Well you see, it's not so much that it's more 'power', per se, but doesn't it make you FEEL more powerful? By the way, can I interest you in a time-share?"
Dyno chart showing proven results or it didn't happen. It's either more power or it's not. Feelings are too easily influenced by Light Wallet Syndrome. The truth is it IS more power. It has to be. You're running all the other accessories at a lower speed, so they are doing less work, so the engine has more power available to devote to the wheels. The problem is that it's such a small difference it's hard to prove, because if you dyno the car on 2 different days, other factors like temperature and humidity could skew the results almost as much as the pulley diameter. If it adds 10 hp, that's 3%, and only at the peak, it's less everywhere else. If a 3% change in power really changes your life, I recommend also always running with an empty fuel tank. With ~100 less lbs in a ~3000 lb car, that's another way to shift your power-to-weight ratio by 3%. FOR FREE!
So by this logic you're saying: lower gearing with the same amount of horsepower can't/won't make you quicker in a drag race? Uh, yeah ok, good argument. And, no it's not more power - the dyno proves that... Oh the empty gas tank is very illustrative as well...you must be a smart guy
My point is that it's such a small difference in power, who cares? It IS more power to the road, period, I don't know why people are arguing about whether it is or not, and instead talking about how it "feels". If you reduce the amount of power you're sending to accessories, without altering the engine, the engine has more power available to send to the wheels. Fact. The dyno test in that Youtube video is misleading since it shows almost zero change, but it proves that the amount of power gained is so small that it's tough to measure and thus not worth arguing about. This pulley is not a substitute for buying a 911 Turbo.
If you're in the camp that this is a great mod and it's worth spending the money and risking a change to the original design, go for it and enjoy.
If you're in the camp that this part is dangerous to use for the engine, or overpriced, skip it, and know you're not missing out on much.
In daily driving the difference is silly to talk about. On the track bigger gains in lap time will be made by changes to tires, suspension, or dropping weight.
Under drive pulley compared to a turbo??
Also we have been talking about the fact that it does not make more power but changes the dynamics and how the car delivers the power.
If you're in the camp of not liking the mod then that's fine, don't rain on someone else parade. People have been adding under drive pulleys for years without failure. Jake likes the UDP so i'm good:
https://rennlist.com/forums/996-foru...ml#post9869391
I think you forget that he is also a salesmen of them. His whole purpose on this board is to drive sales. He is not the god that many on this board think he is. He's a businessman.
I don't know Jake personally, and he's never done any work for me - so I don't have any "skin in the game" so to speak. This being said, he seems like a highly principled business person as well as a highly skilled mechanic/developer of products and processes - some of which he's kind enough to share here without compensation (and often insults and other dispersion's - granted he can be a bit prickly at times). While he's not shy about promoting himself or his business when he sees fit, it hardly seems to be "shameless self promotion" to me. Of course everyone is entitled to their opinion.
One, I've argued with Jake a bit, so I'm not a huge fanboy. Two, he's more carguy, mechanic and engineer (not the book kind either) than businessmen. And honestly, he has good business because he delivers quality. He isn't here to sell us squat. In his own often rough around the edges way, he is trying to and actually helping people. I look forward to taking his classes someday.
Give it more time to set in. you've only been here 6 months, ive been listening to his banter for years and years. Somehow people still worship him for it. It just gets old after awhile. /rant off
I do get a chuckle out of the "modes of failure." I can come up with infinity.... #137,216 jump curb, punch hole in oil pan, lose all oil, IMS siezes instantly, kaboom. #321,997 while worrying about what oil to use owners sweats profusely into oil fill tube. Highly alkaline body sweat cause corrosion which creates oil to foam excessively during next track day event, kaboom!
But all in all, I really think Jake wants to help others.
The main drive pulley dictates the speed of all the other slave pulleys on a serpentine belt system. A smaller drive pulley has a smaller circumference, thus the belt will rotate fewer rpms than with a larger pulley.
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