RPIpower

Is this question based on sarcasm or are you really asking?

skelevirus

either way idk?! lol what does it mean? is it like the difference in 3;73 to 4;11 ring n pinion on a rear end?

RPIpower

How many rotations on your ac pulley, power steering pulley, etc compared to your crank pulley is efficient? You want your AC pulley to turn 3 times per 1.5 turns? You gotta know these things. Even with a 16% underdrive, we see a very slight increase in engine oil temp. I cant even imagine why anyone would want to go 30% without looking forward to some costly repairs in the next couple of years.

Rab Dog

30% underpully = RPI Oilcooler to keep temps down!

Not matter what you do RPI will have to be involved in one of the mods!!

acuteperformance

I'm really asking.

RPIpower

Thats fine and I dont mind answering these types of questions to anyone that asks me but dont you think its unfair to the customer if you offer something to them that you dont understand?

I really liked 5series.net before but this forum seems to be taking a step in the wrong direction as far as quality of posts, vendors and discussion. I really hope things work out better here so that people can still come to this forum for valid and legit info rather than a bunch of fictional information that gets passed on from reader to reader.

Reducing the diameter of the crank pulley will throw off the turn ratio between the crank pulley and the other pullies that it is designed to turn. "Underdriving" too much can cause a strain or inefficiency in the accessories that are powered by the other pullies (i.e. ac, ps, etc.) RPi is not the only manufacturer that found a 16% is what is safe for the M5. Dinan, Rogue, Evo all use similar underdrive %s. With underdriving the crank pulley too much you are making the crank pulley turn more before it makes one rotation on the other accessory pulley, causing your accessories to run less efficiently. I wont be surprised if people start killing batteries due to inefficient charging either. This happened with a very popular brand pulley that I had with my Nissan. I had to replace my alternator 3 times in 2 years.

acuteperformance

Maybe this isn't the right place to have this discussion, but since you're calling me out...

If you take a look at what I sell and what I actually push hard, it's products that I've tried on my very own car, companies that provide excellent customer service, and/or companies that I trust. With that said, if a customer comes to me and adamantly wants another product, I'm going to sell it to them and most of the time, I will tell them hey, I've never used this product and I don't know much about it, but I do know about company X and their product, but if you're absolutely sure you want it then I'll sell it to you.

I don't know where in this thread I might have offended you or RPi but I feel like you've taken a few jabs at my online business and integrity in your last few posts (or I could be reading into things since like you said, online conversations carry no tone). You have a quality product no doubt and I'm constantly raving about you on other forums: bimmerfest, 6speedonline, m3post, 5series.net, mbworld, and m5board. You are very knowledgeable about your products and I ask you questions publicly so you can show that not only is RPi putting out quality products, but they can back it up with knowledge and experience. How else are we all supposed to learn if we don't ask question after question?

That's all.

Michael
Acute Performance

RPIpower

I have told you before that I am here to help and edumacate others. I dont like just selling something but I tell people I sell stuff how and why it works and why it works better than others. With that, I dont sell any and everything to people that ask for it. THats not to say that what you do is wrong. But if one of my products is compared on a public forum, I will come out and explain. You should know that I have always said it the way it is. I wont sugar coat something or pussy foot around a situation. If you asked me about something, I would answer you. My posts were merely a response to your comment about comparing products and saying which one is better without any backing at all. My posts about internet companies was not meant to be directed just to you. Its how the industry has become and its what has driven a mass amount of BS products to come on the market. After a while, all it does is hurt the performance auto industry.

acuteperformance

LOL, when I said that I was implying OTHER companies don't back it up. You are one of the few manufacturers that do and provide information.

cbpmark

Thanks all, wow this post went a few different directions I was just simply asking can you really see 10-15 HP gains from a underdrive pulley? I usually dont trust companies stating HP gains - but knowing RPI and using the products currently - I am sure that the dyno numbers are correct. With that said RPI it is!!) Ill be adding the GT exhaust and tune shortly as well. Thanks all for your real world info on products.

BTW whoever on this board is from RPI great development on the scoops, seems others are cheating off your design. Any thoughts on a East Coast shop??!! $$$$ would come a rollin in....