Then why does the service maual have you mark its orientation before removing it?

Anyone have a dyno chart with before and after?

 

Why does the service manual say not to use the same head bolts over but the chevy manual for repairs under warranties say to use them again? Well it all goes back to the fact that the manual is written for more than one engine at a time and they do not key the balancer so in the original install it goes in where ever.

Maybe I asked the wrong question.

With all the UD pulleys and replacement stock pulleys that have been sold for the ls series engines since 1997, where is the one person who had any of the problems you list....thats one person Iasked for with engine failure do to being out of balance, warm ac, bad charging system, low power steering assist, hot running temps, ect?

My cousin has 86k on his motor that has an UDP.

The stock motor is internally balanced for the rotating assembly. That means a zero balanced pulley and clutch assembly is a zero balanced set-up. I checked the UD pulley for balance. It was zero and cost me 25 bucks to find out.

 

Have you tried the search feature. All these questions have been tossed about for years and always with the same outcome. 9-10 rwhp and that is noting that an out of balance engine would have lower HP.

If you are that worried about it may I suggest an HPI superdamper. They are made to balance out, out of balance engines and have a 10% UD rating on some. All the positive and no vibration worries.

Also be sure to let all the tuners know including Lingenfelter, that all the motors they build are going to fail from the pulley. I don't know any tuner that doesnt use them.

 

Are we talking about the longevity of the aftermarket underdrive pulley causing deteroiration on the engine? If that's the case, it's certainly not worth it.

 

The Underdrive pulley mod is a solid proven perf gain, I have run them on a lot of my past vehicles and love them, the only problem is your Warranty can be totally void when doing this little mod.

I know from experience I had a 1999 GMC2500 Suburban w/lift kit K&N intake, Borla exhaust, Headers and Underdrive Pulley, They refused warranty work on my A/C after they discovered the Underdrive pulleys

 

I'm not sure why your so defensive about this, but if you note in ALL my above posts I state that it MAY cause those effects. This forum is used by many people considering different modifications and possible risks associated with them. It is important in my mind that people understand why a modification leads to improvement and what possible sacrifices they may be facing. Also, it takes a much larger sample size as well as more precise testing method to ensure that no one will ever have a problem (this is the testing GM did to determine what pulley to use). Just as I would never state that everyone will have a problem, it is irresponsible to state that no one will have a problem. Overall my opinion is that they are on the lower side of risks, but personally would not get one.

Also, I know that the HP gains are posted all over the place, but that is HP at one specific RPM which is pretty useless, in order to really know the gain you need to see the chart over RPM range (or possibly 0-60, 1/4 mile). Also, even the best dynos are only repeatable to 1% and most dyno's you rent are around 2.5% or more, which on Corvette is about 3.8-9.5 HP. So, a gain of that could easily be normal test to test deviation. While I was in college we dyno'd cars all the time with aftermarket mods. In nearly all cases of air filters, spark plugs (split fire), computer tuning, we couldn't confirm any gain in HP. We never did any underdrive's while I was there. The largest confirmed gains were from significant mods such as exhaust/significant intake/heads/cams/valves. If you notice on the forums, those mods usually post dyno charts while others just post some HP gain.

I work in MI for an automotive supplier and know that a lot more than what most people think goes into vehicle development. The requirements of making a vehicle operate in all the conditions/options to a certain requirement have a large effect on the end results. For instance, if a vehicle with low electrical option content was only going to be used in low temperature regions, you could probably get away with a smaller pulley than a high electrical option vehicle used in high temperature regions with inclines. Therefore, while you and others may not have a problem it doesn't mean that no one will have a problem. People also have different tolerances of things as well as different habits. The loads at idle for someone with a fully contented car while blarring their stereo, both heated seats going, HVAC on full, etc.... are different than others.

Another example would be of the powersteering system. The power steering rack will have some kind of specified pressure requirement with a range given, the racks made by the supplier should fall in this range. The pump will have a specification to output a specified pressure range at a certain RPM, once again they will have a range. Variation in product will always occur and different racks and pumps will be matched up at the plant; ideally even the rack with the highest pressure requirement will work with a pump with the lowest pressure output. Engineers usually use statistical tools to ensure full compatibility for product varation. In addition, they also have requirements for long term durability of the system. Nearly all the power steering complaints I've seen have been high effort at idle, most cases even a small increase of RPM remedies the situation. My G/F's piece of Sh** Toyota is like this now and wasn't when she first bought it. Obviously if a underdrive pulley was put on her car the problem would have occured sooner (and an overdrive pulley would solve it). Same problem on many cars I've seen over the years.

The bottom line is that to me it is important for people to realize what possible effect of slower acc. drive and to know what to look for after doing the modification. That way, people can decide on their own if it is right for them.

Finally, if anyone is interested, I can easily setup a statistical test that will tell you with 90%, 95%, or 99% confidence if you got that improvement. Higher percentages will require more testing obviously....

 

If GM or anybody else thought they could get 10hp just by making the pulley smaller without any adverse affects, I'm sure it would've come that way. In spite of what some people think, they are not idiots.

On the other hand, there may have been more benefit from UDP's years ago. The AC on a Corvette shuts down on WOT anyway. So the AC is not an issue. If I'm going to the track, I turn off the heated seats, AC, stereo, headlights, etc. So the Alternator is not an issue. If I'm on the track, I want all the cooling power I can get, so I'll leave the waterpump alone. So the only real advantage might be from the steering pump which probably doesn't need to be cranking at 4 or 5k rpms to give full assist. I doubt that alone is worth any real hp gains. So if anything, get an oversize pulley for the steering pump. A lot easier to install too.

You might want to hear from those who have UDP's but it's just as important to hear from those who don't. It's nice to know their reasoning on why they passed on that mod. It MAY apply to you.

 

No they're not idiots, they just can't figure out how to keep the stock pulley on the engine.

Why so defensive....because in EVERY thread about this topic someone comes along without a singe proven example of their theory. They say how they have automotive expertise and they have a friend that had one on some honda (or toyota as above). Give me a break already. Do a search. Find the car that lost 9rwhp on the dyno if you think the gains are too small to measure (if it is the 9hp tolerance you should have occasional cars losing ower)

The dyno charts show a gain everywhere in the rpm band. Show some proof already and on a corvette not a toyota. Everyone I know of that has one had nothing but good results with it period (even with 1000 watt amps pounding loud music). PLEASE GIVE ONE EXAMPLE OF SOMEONE THAT HAS IT AND HAS PROBLEMS WITH IT. PROOF. Mine is all the people with positive results.

Lingenfelter, vette docs, A&A, LG, ECS...are they idiots?....well they all use them in HARSH conditions and they have no engine failures to date or adverse effects....but since chevy, the company that has a 50k car that cant even register the amount of fuel in the tank half the time...they are the standard since they didnt use the UD pulley.

Wel anyway guys if you are going to post again, please show even one person that had any of the issues you talked about...JUST ONE.

Everyone that used it: good results-none bad

Guy s that don't use it: theories of how it may be bad but no examples of someone with a problem...no one.

Why if it doesn't hold true in practice....for anyone. Guys that don't have it just spread the same false rumors that were proven wrong by those who use it. What is the basis for the opinion and why should it supercede say..Lingenfelter?

 

Your points are well taken but there's also no proof that anyone got a 10hp gain. I didn't say it didn't give any gain at all, I only said if it was compared with a car with all the accessories OFF, the gain would most likely be minimal at best. And I don't know anyone who ever put a Lingenfelter car on the track either. So it might very possibly affect the cooling capacity.

 

At least say it might not affect cooling capacity since you bring nothing to the table as far as data.

MTI tested it and got 9rwhp and every tuner uses them including cartek and vette docs. You going to say their cars don't go on the track? 21 century sent a forced induction car to the N/S blowout as did at least one twn turbo car they built. So since we can find that tuner cars with it can and have run without overheating can you put the BS about the cooling capacity to rest already? I haven't heard anyone complain that their car ever ran hot from using one. Did you?

I got 10.1 average on 3 pulls
All pulls were done with the accessories in the same manner for baseline and modded.

As soon as you test this then you can offer it as fact:
I only said if it was compared with a car with all the accessories OFF, the gain would most likely be minimal at best

Who runs the accessories when they dyno their car anyway?

 

I would be careful of thericker he dont even own a vette and trying to sitr the pot on mbworld about RenntechV12. This is the same guy claiming to have s500 and really s430 = BIG *** POSER http://www.mbworld.org/forums/showth...&highlight=hps

Get yourself a vette then come on the board to talk vette talk until then go back to mbworld.

And get off RenntechV12 and ted baldwins back you big POSER!

 

total agree, this only comes from someone that has never done it before. wants to know the truth without a dyno? there is no way shut down the power steering pump, just take the damn belt off and try to spin it the power sterring pulley by hand compare to other pulleys and you will see if that pulley will spin at all. if the lost of power steering at idel and that that bother you....you need to go to the gym, any 10 year old kid can turn the steering wheel even with under drive pulley.

 

Hmmmmmmmmmmmmmmmm! Should I or shouldn't I??? One says yes and another says no. Maybe I'll skip this mod and just buy the Z06-now, if I can only figure out how to get all that money????????

 

I installed UDP's on my RX7 twin turbo R1, never really felt any performance difference, but I never had it dynoed. I also never had any problems with anything associated with them either. I will probably not do this on my C6 based, at least not right away.

 

Put it on the Z06 too.

 

You would never feel 9rwhp unless its on your go-kart.