js4506

Whats your guys opinions on lighter wheels vs. Full Exhaust

Let me explain...
Im going to be upgrading( I know some of you wont call it upgrading) to 17" rpf1 wheels from my 17" stockers for the pure fact of shaving about 30lbs of rotating unsprung weight off my car. Im fine with the looks of the 17's, and added preformance beats looks in my book so please dont hate.

Also, im looking to add a true dual exhaust with test pipes, and most likely a 5/16 spacer at the same time as that.

So my question is, which one would be more "noticable" driving, the extra hp and torque acheived by the exhaust and spacer or the quicker acceleration and better handling of the lighter wheels, just out of curiosity

Sorry if this has been discussed before, it prolly has, I tried to do some search and couldnt find exatly what I was looking for

andrew's 350Z

iTrader: (3)

Ok, before davidv comes in. If ur going to get the exhaust and 5/16 spacer u won't feel a BIG difference in power, unless u tune it after u do the install assuming u have the DE because u have 17" oems. The lighter wheels I'm not sure. Never seen the difference in a dyno sheet.

js4506

Yeah sorry I have the DE and was considering a tune in with it as well.

Just trying to see what kind of difference each would make, how they compare to each other, etc. if that makes sense

I know neither of them are going to make substancial gains, by any means

s31t8n8

iTrader: (12)

No wheels + No exhaust = +250whp

terrasmak

iTrader: (8)

The wheels will be more noticable

dhwang80

iTrader: (13)

Or you could just lose 30lbs.. And get the exhaust

js4506

Thatd be just sprung weight though, which isnt near as big of factor

JPsZ

iTrader: (62)

30lbs unsprung weight has a bigger effect then removing 30lbs of regular weight. Not sure of the formula, I'm sure someone here knows what it is.

andrew's 350Z

iTrader: (3)

The only real way to tell is if someone dyno'd them. U know stock wheels vs rpf1

Get the exhaust and spacer, popcharger and tune. Then call it a day. My.02

js4506

Im considering doing this, because if im going to get the wheels anyways, i might at well get before and after dyno tests to get the results out there

js4506

Found these interesting

http://rav4world.com/forums/viewtopi...r=asc&&start=0

This first link is of a guy who did dyno before and after putting on lighter weight wheels. He found no significant changes on the dyno readings, but if you read the post on the second page of the link by member "rav4two" He explains why the dyno would show results like that, but there still should be noticable results in real life situations



http://forums.evolutionm.net/evo-dyn...ht-rotors.html

Then on the other hand, here is a guy who dynoed before and after switching to light weight rotors for the same principle and found a quite large gain in Hp and tq?

MaelstrØm

The lighter wheels on the dyno won't make much difference because the dyno cylinders have a large mass to them which is effectively combined with the wheel weight when they are rotating, so the dyno is not measuring what you really put to the ground.

When you accelerate on the open road, the mass of the road doesn't matter.

Arvin89

iTrader: (1)

I have a popcharger, 5/16 spacer and test pipes. And i definitely felt a big difference with my car. Sure if you dyno it, my results may be slightly better than stock, but you can definitely feel a difference in the way the car responds while driving. I dont care what anyone says, but your butt dyno will definitely feel a difference. And since your doing a full exhaust i think you may feel even more, also, the way your car sounds will also effect what you feel in some strange psychological/acoustic way.

And for the guy on the evo forum who noticed a huge difference with lighter wheels...maybe he forgot to mention he put a new exhaust on or something?

Lighter rotors would be considered unsprung weight, which would definitely effect handling and perhaps acceleration on solid ground, as your are able to accelerate faster because you have the same amount of power, just less weight to carry. But on a dyno.. it shouldnt have very much of an effect on hp or torque. Thats because the dyno is tested on rollers, so the vehicle is not moving any weight during the test, so the hp and torque should register roughly the same should they not?

I think this is the same thing maelstrom is saying, but im not sure because his is a bit more ambiguous.

billsrcursed

Are you tracking the car?

The answer to this question should solve your problem, I would think...

Spork

iTrader: (6)

Unsprung weight > Regular weight







There it is.

chitownpete

When I replaced my 18" stock wheels with Infinity G35 17" wheels I lost a total of 35 pounds and it made a very noticeable difference in 1st gear and a noticeable difference in 2nd. It wasn't in my head as I didn't even weigh my 18s at first since I thought they would weigh about the same. After a few drives I weighed the 18s since my car felt so different. At low speeds the car just responds a little quicker. I've kept my exhaust etc stock so I have no opinion on that.

SLIdEwAyZ25

iTrader: (1)

RX7's do the same thing when you change flywheels. the stock one weighs like 40 pounds and going to a 12 pound flywheel in first gear you gain around 30whp second gear like 15 to 20hp third gear like 5hp and then fourth and fith are exactly the same as before the flywheel was put on.


so the reason one guy noticed no gain is probably because he was in a high gear and the other person might have been in a low gear

kacz07

iTrader: (15)

Open up your intake and increase plenum volume. Get a larger than 5/16th" (3/8th", 1/2", 5/8th") spacer and Crawford or APS Tall Boy upper plenum. You may have to get a different strut tower brace for clearance, but you will see the best gains with those. They may be equal to the 5/16th" before an exhaust/tune, but once all tuned, your maximum gains will be realized.

kacz07

iTrader: (15)

Also, getting a freer flowing exhaust cat/test pipe, y-pipe, downpipe, and catback will save you more than 30lbs AND give you more power. Two birds with one stone.

2004Black350z

iTrader: (37)

seems wrong to me. If u buy exhaust/spacer and test pipes and cant feel a difference then u have something wrong with ur car/butt