Underdrive Pulleys

[Z2TT]

Be careful when looking at Dyno Comparisons, if there done on different days they might not be totally accurate.

I'd say anything that reduces the rotating mass will help but you need to ask a few members who have actually done the

upgrade on their personal cars and ask them.

[Kroozin]

If I was chasing ever little bit light wheels would well out do the under drive IMO

[Bazza96]

Okay guys, thanks for the help and opinions and stuff, but this is for the motor, will get to lightness later.

And Z2TT, man I totally agree with you, but like.. on a N/A I6.. Yeah maybe couple of different results, but 9.5rwkw I dont think is just a 'good day'..

Like I said.. on a N/a 6 anyway. But a turbo'd Vehecle, I'd agree.

Edited 11/08/13 10:45 AM by Bazza96

[Kroozin]

FYI (doin a wiki haha)

1. (Blue curve) Factory wheels: 20”x9.0” with Pirelli 275/40-20 tires weighing 68 lbs combined per rear wheel. – Max hp: 371 hp, Max Torque: 375 ftlbs - (Baseline)

2. (Red curve) Aftermarket wheels: 20”x9.0” with Pirelli 275/40-20 tires weighing 72 lbs combined per rear wheel – Max hp: 369 hp, Max Torque: 373 ftlbs - (A [-] loss of 2 hp and 2 ftlbs)

3. (Green curve) HRE wheels: 20”x11.0” with Nitto 315/35-20 tires weighing 60 lbs combined per rear wheel – Max hp: 380hp, Max Torque: 384 ftlbs - (A [+] gain of 8 hp and 9 ftlbs and that is running a 2” wider wheel/tire combo)

Conclusion:

The engine obviously still cranks out the same amount of hp and torque, the lighter HREs simply waste less of it before it gets to the ground. Also interesting to note is that the gains are not just peak gains, but gains across the entire rev range. If they had done a braking test, we would have seen similar results as the rotational inertia effects also have a significant effect on how much energy is used to stop the wheel/tire combo vs. stopping the car. We talk about these effects all the time and focus on designing lightweight wheels with low rotational inertia, but it isn’t every day that you get to see real hard data showing the true effects.

[Bazza96]

Far out! that's interesting, I have 20" Advanti Chromes haha.

Reckon they'd weigh as much as BA XR6 ones? :D

[ratter]

the 20's even if the same weight as factory 18's will still slow the acceleration rate

[ratter]

http://www.fordxr6turbo.com/forum/topic/85925-under-drive-pulleys/

[Bazza96]

Besides that dyno graph, does anyone have personal experience with Underdrive pulleys?

What sort of gains?

[ratter]

doesn't the dyno sheet show gains?????????

[Bazza96]

Yeah, I had already seen it before man.

And that's a V8 isnt it?

I was looking for I6 gains man, unless that's in HP and that's a cammed and tuned I6.