Did back to back dyno's today with my old Enkei RPM2's that weigh the same as track wheels and that I did all my old dynos with, then dynod with iforged wheels. Net result is a 3hp loss due to heavier wheels. not too bad.

 

Only 3 horses??? Man, guys act like it is so much more. I remember another trend noting that the 1/4 mile times only differed by hundredths of a second for these bigger rims versus smaller rims.

If I actually am racing a guy, and he beats me cause of his extra 3 horses, then I will have to bow down to him, lol.

 

that's cool that you didn't lose much..

I just wanted to remind people that even if two rims weigh exactly the same - if one is a 16" rim and the other is a 19" the 16" rim will still offer much better performance because most of the weight of the rim is on the outside and the further away that you place the weight the more it will slow your car.

 

Well, this has been said before. But the interesting thing to me is that really, the tires are the ones with all of the weight. Picked up my 17s with tires yesterday, and boy those things were back breaking heavy. You have to balance out that if both tires have the same circumference, the tires for the 16s have some addition weight too, especially full of air.

 

there is a world of difference between my iforged and 17" race wheels/tires, mostly due the the lower tire diameter though. stock is 26.7", and I run 25" on the track.

 

the weight takes away from acceleration not horse power.. dyno will not take that into account accurately

 

yes, and according to someone elses test here, I believe it was .2 in the 1/4 mile.

 

Yes and NO.
That dyno will take that into account because it is a DYNOJET 248C. They're an inertia dyno, which means it measures HP by measuring how long it takes to accelerate a known weight (the drum the wheels turn).
If you did it on a brake dyno i.e. "Clayton" it would not be taken into effect.
But that part of the puzzle that’s missing is what gear it was sampled in. I'm betting 4th due to the 1:1 gear ratio. The lower the gear the greater rotating weight makes a difference. If you do one in say second it will be a larger difference in HP.

2003z Thanks for taking the time to dyno with light vs heavy wheels. We appreciate all those who spend time and money to provide useful data
Gary

 

dyno'd in 5th gear, thats the 1:1 in the manual trans.

 

Wow, thanks for posting the results. I'm suprised that the HP effect wasn't a greater amount. Now when I go to the drag strip this friday with the Z car club, I'll just leave my I-forged "heavyass" Aero's on since they won't affect results too badly. I still can't understand why 20lbs per axle doesn't affect things a bit more.

 

Don't forget that you aren't dynoing the front wheels which are also heavier.

 

3 HP has to be within a standard deviation

 

I don't think so, all my dyno runs in each configuration were extremely close to each other. +/- 1hp

 

seems odd, hell just removing 40lbs from your car would give you a little somethin. removing it from the tires does nothing? tho it would be 6hp, cause as someone said, front and back, but still. I think its more than that, cause you then get the 40lbs moving foward rather than circular as well.

 

How many pulls did you do with the 17's, how much time to switch and how many pulls with the 19's? Is your 3hp loss an average of both tests of each wheel?

 

Ok, just FYI, I weiged my 19" iForged FS-6s before shipping, and they (F/R) weighed 25 and 27 lbs respectivly. Not bad for a 19" wheel, basically the same wieght as the stock 18"s.

 

yeah and forged 18s still fall in around 18lbs, so your not quite lookin at 10lbs per wheel. iforged might not be the best to call "heavy" there are far heavier. its just less light. but hell 6hp and 40lbs weight savings still aint bad, tho I do think its more than that. just not sure why it doesnt show up.

 

Didn't do any pulls with the 17s. I did 3 pulls with iforged, unstrapped the back of the car, jacked the rear and put my old 18" enkei rpm2's, )which I did previous dynos on and which weigh the same as Track rims), then restrapped the rear and did 3 more pulls with the enkeis. (tire sizes are both 26.7" diameter too)

What we have seen thus far is a 3hp difference on the dyno, and .2 in the 1/4 by someone else. Apparently wheel weight isn't as big a factor as it seems for everyday use. Yes, in an auto-x or drag race where 1/100ths of seconds count, or on an extended road course it can make a difference but not for everyday.

Finally, why is it that so many doubt or can't believe honest dyno/track results when people post them. Maybe I should just keep the info to myself. (not directed to you 350zmotorsports, who I quote above)

 

Thank you for the effort, 2003z. This is something I was real interested in, since our rims are almost identical. Everyone will deny results only cause it may cast their decision in doubt. After picking up some of the stock rims myself, I have learned that their is far more to worry about then the weight of the rim. Most of the weight is in the tire anyway, plus the tires are the farest thing away from center.

Now I am not discounting the value of being lighter. Just saying it isn't unholy to go a bit heavier to get a look that you prefer. Mind you, the iforged rims aren't real heavyweights, and going with some real heavyweights ain't for me.

 

I dont doubt the results, suprised maybe, but it sounds good. every little bit helps right?