staticlag

Link to the DIY is found on page 3 or https://www.rx8club.com/showpost.php...9&postcount=34

Just arrived today from Vividracing.com, took me about 45 minutes to install.

It came with no instructions but it was simple enough to figure out. Contents of box were: 2 belts and 1 aluminium pulley.

Weighed on a fishing scale, the stock pulley assembly minus the bolts was right about 2 lbs. Agency Power pulley was .5 lbs! and much smaller at that!

For the install I needed:

10mm
12mm
17mm

Breaker bar & torque wrench.

The AP pulley came with HEX style bolts and I don't have HEX bits for my 3/8" socket set (or maybe I do, I dunno). Edit: The HEX bolt size is 5mm. So I found a L HEX wrench that fit and used a small piece of pipe as a cheater bar. So just a note is that you need a HEX set for your socket wrench or some similar tool to install with the suppled bolts(which were much smaller and lighter than the stock).

I had to undo the aluminum MAF holder for my REVi but I could easily work around the REVi itself with the rubber accordion attached still to the TB.

I tightened the belts to about stock tightness and took a quick drive around the neighborhood. No CELs, after the engine warmed up a bit I played around, but it was 1:30pm and there was traffic and its ~83 degrees here so I'm going to take it out tonight and give kelly (my rx8) a real test

The car reved noticibly faster than stock in neutral, while in gear I could definetly feel more pull starting at around 3.5K but I didn't go WOT in traffic. At 4K crusing for about 2 minutes I turned on the A/C and it was still cold but a bit warmer than usual (My A/C was usually freezing cold). It was still plenty cold for me and I never use A/C anyways.


Taken with Cell Phone:

Top (stock) Bottom (AP Underdrive):


Side by side(The AP is 1 piece, stock is 2 pieces):


Installed AP:


Link to the DIY is found on page 3 or https://www.rx8club.com/showpost.php...9&postcount=34

crimson-rain

Nice. I'm thinking about getting some of these and would love to see how they perform.

One question, will this setup cause a problem if you have a subwoofer and amp? The amp is not all that powerful and the sub is only a 10".

whenson417

Awesome write up.
That silver pulley looks nice. I opted for the blue one. I am glad to hear other people are getting the same results I got. Agency Power is using my dyno chart on their website. I have before and after dyno's but for some reason I always have problems at the dyno so I feel my car never lays down the maximum hp it could. One thing I did differently in during my install was that I removed the battery and battery tray rather than taking out my aluminum maf holder. It may have taken longer but it helped me see better in the dimmly lit garage I have.

staticlag

Good question, but, I took out my JL 500 watt amp yesterday in preparation for this install so I have no way to test. AP says the alternator is 20% underdriven so that would give you about 80 amps usuable maximum. I really wouldn't advise an underdrive alternator setup like this one if you're looking to power any massive sub a small amp might be okay though.

toxin440

Hmmm okay im going to be a n00b and ask what exacly do these underdrive pullies do? From my limited (but expanding) knowledege of cars it looks like you are changing the diamater of the round part to do what.... put less drag on the engine to power other components?

Any info would be appreciated because this looks like a cheap/easy mod to do for a little more power.

army_rx8

does't really make the engine more powerful...supposidly it reduces the power loss due to the accesories running. i'm still on the fence as to how much it frees up. i've heard freeing up 1 pound of rotating mass can be equated to roughly (not exact here just used to put things in perspective) 1 hp. but i believe that hp is at the crank..not the wheels. most bang for the buck when it comes down to lightening..would be flywheel...and rims/brake components (i.e. rotors). but i havne' ttried the underdrive pullies..most seem to like them and say they help out...so who knows.

but i haven't bothered to research any of this so take all i've said with a grain of salt

XDEEDUBBX

Many people that get pulley's don't feel much gain with them. I think fanman dynoed and only got 1 hp from it. But if it revs up quicker thats good.

staticlag

Okay, just got back from a spirited drive...

and....

Wow! For $144. this is the best mod you can do! Car feels much more responsive and pulls harder in every gear. In third at 4.5K I just tap the gas and I instantly shoot forward! First gear just zings by! First pulls much harder and more smoothly, bogging down is reduced!

Drove 4 people around using the A/C and it wasn't a problem at all, everyone in the car was nice and comfortable with the A/C on '3' and it was 92 today! Revs drop quicker, but it really makes the car easier to drive.

Later on there was a g35 on the road, and lets just say that he might as well have been driving a 92' 4 door honda civic.(thats probably the culimnation of all the mods though)

Cost and benefits this should be the first mod someone does! Honestly!

All I need is for my flywheel to get here and its going to be rev-tastic

DRKSYDE

iTrader: (1)

If you look at Wesley's Dyno from th AP site it shows 8.1 whp gain. Just an FYI.

http://www.vividracing.com/catalog/p...bd80d491c8bb8b

Fanman

The last people you want to believe are vendors, and the last vendor you want to believe is Vivid Racing. If you look at Wesley's dyno in another thread he gained 1 whp on the top end (more through the midrange), and now they show that same dyno, but it has been doctored up to show 8.1 whp. Looks like somebody's re-touching up dyno plots.

https://www.rx8club.com/series-i-aftermarket-performance-modifications-23/pulley-pulleys-pulleys-90154/

I got 1-2 whp across the board with my SR Motorsports pullies, and they were claiming 12 hp.

swoope

iTrader: (5)

this would be the last mod i would do..... maybe after the exhaust spinners....


beers

DRKSYDE

iTrader: (1)

Good point! I didn't even think about that. Kinda like the Nology plug wires myth too huh!?

Thanks for the other perspective.

DRKSYDE

iTrader: (1)

Wesley,

Could you post your own personal before and after dyno's for comparison to the manufacturer one?

staticlag

First of all, those two graphs compare 2 different runs, one compares 12 & 13 and the other compares 10 &13. Second of all, both show about 5hp through most of the low end. One shows about 10-15 torque gained in the low end and the other shows 8.1 hp gained at the top. Either way there are gains and its definetly more than 1-2hp.

So my statement stands, for $144 and 30-45 minutes of in your garage work this is definetly the first mod someone should do! What are the alternatives? 3.5 hp for a $650-$700 exhaust? 2-5 hp for a $350-$500 intake?

Fanman

So you're going to tell us that there is a difference between one run and another of 1 hp vs. 8 hp ? I'm not really talking about the low end. They look like the same dyno graph, but one shows basically the same power curve/dyno and shows 1 hp gain, the other shows 8 hp gain. Doesn't this bother you ? You don't see exhaust dynos showing 3 hp one run and 25 hp the next run....with the same exact power curve. Also, a 1-8 hp gain, and a 10-15 ft.-lb. tq gain is absolutely not consistent with this engine. Never seen it. Pretty much see a 1 to 1 hp to tq gain, or less tq gain than hp given the nature of this engine. It shows more like a Mustang GT dyno.

You can believe what you want to believe. No skin off my back. Just posting my dyno results, and relaying my experience. It's not like I don't have pullies on my car, and I am just bad mouthing it because I think I know what they are like. I actually have them, and I am giving my opinion on it. And you are not going to notice 2-5 hp gain. That has more to do with wishful thinking on the seat of the pants then actual gain. The human body won't be able to tell a difference of 1%-2%.

rexi

Obviously not all pulleys are created the same.Most of the people on this site that have either unorthodox or agency power pulleys seem happy with them. HOWEVER, for some reason, some people who have the SR pulleys dont seem quite as convinced???????.

Just my thoughts. Maybe time to try a different brand before completely passing them off as worthless.

Regards
Rexi

Fanman

You're not going to get a huge amount of difference between pully sets, unless you drastically underdrive them, in which case you will kill your alternator, or AC. This isn't a Mustang GT, where you have a 20 lb. harmonic balancer, and you can take off 5-6 lbs. You are talking about the stock pullies weighing a few lbs. at best. You aren't going to have one set that is 3 lbs., and the other one 8 lbs. I do like seeing people's experiences with their pullies & seat of pants perspectives, but would like to see several people dynoing out their cars and showing good proof of real gains. When Whenson posted his gains in the other thread it was a lot more believable, but then all of a sudden the same/similar dyno shows up, but with 8X the hp gain...OK. If you believe in the product, and want to get then knock yourself out. Just don't get too mad when somebody posts a contrarian view to the matter & shows some evidence to the contrary. Again, let's see some more dynoes (not from the vendors, but real RX8 owners that have no financial interests in the product). That would be great.

toxin440

see the arguing posts for things like these pullies confuses semi-n00bs like myself. I read a few threads about people raving abou them, then see threads about people saying they are useless.

I'm slowly in the process of saving up some money for mods (almost everything except going FI) and pullies were originally on my list, but now I don't know what to think. For about 150 bucks... thats not bad but just gotta keep in mind thats 150 bucks that COULD be going towards my RP Supercat, or RB exaust.

r0tor

iTrader: (1)

this forum is full of reviews of products with results being reported that are more placebo effect then anything... take every review with a grain of salt

Nemesis8

iTrader: (3)

Only one pulley? The Unorthodox replaces all three.

yiksing

Underdrive pulleys helps your water pump to keep a constant flow especially at extensive high rpm use. Some also keeps your alternator life longer.

swoope

iTrader: (5)

so the aftermarket knows better than mazda on part life????

yes if you have a car that just does track time underdrive make sense.....

but if you drive you car on the street, not so much.....


beers

Beodude123

If you only have lightened pulleys, with the stock being so light, you won't notice a lot of difference. But when you throw underdriving into the mix... It can change quite a bit.

whenson417

Sorry for the delay, I have been out of the loop and just happen to notice a lot of concern about the dyno chart that Vivid Racing has posted. Just to let everyone know, they did not doctor or change that dyno chart in any way. It is just the same now as it was on the day I sent it to them.
Unfortunately, when I took my car to the dyno, the first chart they handed me was different than the first one emailed to me. I called Dynolab and had Arthur email the correct one and passed both along to Agency Power. For some reason (marketing reasons more likely) they chose to post the chart with the maximum hp gains, not the one that shows the gains throughout the rpm range. The chart they posted does appear to have some funky vibe about it because of the dips not matching up. The only thing I can think that could cause this is Dynolab may have had one run saved on a hp vs. rmp setting and the other on a hp vs. speed setting so the may not have lined up once placed on the same graph.
My thoughts on the pulleys, you would have to shoot me before I will take these off of my car. I do not believe these things create much or any power but what I do believe they do is allow my engine run at maximum power under any condition. I notice that when my car had old plugs, it produced more hp and tq in the lower rpm range, more so than when I put in new plugs. I dyno'd after I replaced the plugs and saw that my car made considerably less power in lower rpm's but there were extra ponys in upper rpm range.
About a month later I replaced my coils because they were burned out and noticed more power so I did another dyno to see where I was sitting. For some reason the first run was the best I had during that session so that is the chart I took home. I then installed the pulley about a week later and noticed the extra power in the lower rpm range. I took my car to the dyno again to see what was there. Not a whole lot extra in the top end (1-3hp) but there was about 10 or so gained in the lower range which makes me believe the pulley allows the car to run at maximum hp all through out the rpm range. Its like the pulley is giving me the best of both worlds, more hp in the lower and upper rpm range.
It all just could be a fluke and believe me when I say that my dyno's have some discrepencies like not being performed on the same day, same tank of gas, back to back to back. But hey, my car is my daily driver with just over 40k on the odometer and I do not work in a shop or have any affiliation with Vivid Racing or Agency Power. I just offered them my dyno chart because I was hoping to help out other potential buyers who want to know if they are buying a piece of crap or not. Hell if someone offered to give me a turbonater, I would test it on the dyno and if it posted gains then I would send them a copy of my chart as well. I just like trying to help everyone out.

oh yeah, here are all my dyno charts, i may have more posted in the dyno chart thread. I would explain which one is which but Atlanta Bread Company is closing and I do not have internet access at my house so I have to cut it short. Feel free to PM me if you have any questions.
Best regards.

staticlag

Small rev video while at stop light: