tallguylehigh

Nothing that earth shattering, just an observation I made while reading through the new CAR magazine with the RX-8 on the cover. It said that the RX-8 weighs 1315 kg, which is excellent, its 2893 lbs to be exact (2.2 conversion). Then later on in the magazine, during an article about the Honda NSX Type R, the article says "It's 84 kg lighter (which has the same accelerative effect as adding 20 hp)," and it got me to thinking, compared with the Z, how much horsepower does the RX-8 have?

Ok, now I am going to try to mimic Buger with calculations, so stay with me.

The RX-8 weighs 2893 lbs, and the latest Z in C&D weighs 3363 lbs. Ok, the RX-8 has 250 hp and the Z has 287 hp. So if an RX-8 weighed as much as a Z and horsepower increased linearly with weight, how much hp would the RX-8 have?

Ok, 84 kg = 184.8 lbs = 20 hp

Since we know that, we can also determine the weight difference between the Z and the Rx-8, which is 470 lbs. So setting up a ratio:

20 hp/ 184.8 lbs = x hp/ 470 lbs.

Which gives an X value of 50, meaning that is an RX-8 was as porky as a Z, it would have ~300 hp Plus this doesnt factor in the other benefits of having a much lighter car.

The point has already been made, if so I'm sorry. Just an observation I made.

cueball

This has been pointed out before, but this is the most presise comparison by someone that i have seen. Good job. I am too lazy to do something like that, so i am glad someone eles did it for me.

revhappy

That's a good illustration of the effect of weight reduction on performance, but I think you might have slightly overstated the theoretical rx8 HP at the 350Z's weight. However, the reduction of weight will be equivalent to different amounts of HP at different weights.

For example,

Car A: 400 HP and 4000 lbs.

Power-Weight Ratio: 40,000/4000 = 10


Car B: 200 HP and 2000 lbs. 20,000/2000 = 10

After the 20lb. weight reduction the denominator on the lower weight car will have a larger percentage decrease, thus the ratio will increase more (less is truly more in this case!).


Car A: 40,000/3800 = 10.53

Car B: 20,000/1800 = 11.11

Thus applying that logic to the 350 Z example:

RX8 25,000/2893 = 8.64

350Z 28,700/3363 = 8.53

Theoretical RX8 HP at 350Z Weight: X/3363 = 8.64

X = 29,056 or approx: 291 HP

However, I think your weight for the 350 Z is a bit high. According to Edmunds, the track edition weighs 3225 lbs.


Theoretical RX8 HP at 350 Z Weight (Edmunds Track Edition):

X/3225 = 8.64
X = 27,864 or 279 HP

While this is fun, HP and torque at the wheels (in relation to weight) is what really counts. I can't wait until we get some DYNOS, I'm sure Buger will come with some very interesting calculations, graphs and analysis!

Quick_lude

Plus we're dealing with accelerating a fixed weight.. gearing is important too. If the RX-8 stays in the mid 2800 lbs and has 250hp, it should be very close to the 350Z acceleration numbers. Close enough to make it a drivers race.

Brian_RX

According to those evidences, the S2000 should bat the Z350, right?

BryanH

One advantage the Z has is torque. Torque builds horsepower more quickly as the revs rise.

Buger

Interesting thought tallguylehigh. I think that revhappy made some very good points though. Hopefully we will get some real information next week with the official launch of the rx-8.

The 3363 weight does seem kind of high for the 350z when looking at some of the other published #s for it. I think the weight/hp ratio of the rx-8 will be a little higher than the 350z (more weight per hp) unless Mazda surprises us with a higher hp # than 250.

I put the 350z specs in Cartest and the estimated 0-60 and 1/4 mile times came within 3 one hundredths (.03) of a second of the released times of 5.4 and 14.1.

The Cartest results for the various rx-8 permutations that I came up with come out to about 5.78 (0-60) and 14.45 (1/4 mile) based on the speed at redline info that one of the articles had and a weight of 2950.

The article had the rx-8 redline speeds at 37, 65 and 99 for the first 3 gears. The 350z redline speeds are approx at 38, 63 and 90. I believe the 350z will have a little bit better acceleration in the first 2 gears and a quite a bit better acceleration in gears 3 and up if the rx-8 is geared how I expect it to be.

While I expect the 350z to have better acceleration performance, I expect the rx-8 to have better braking performance, much better handling performance, have a higher quality interior and be much more practical in terms of seating and usable storage space.

Mazda has said all along that the rx-8 is being made to cater to a wider market than the traditional sports car. I would personally have loved seeing a new 2600 pound rx-7 that would have incredible acceleration to go along with incredible braking and handling. I would not have bought a new rx-7 though because it would not be practical enough for my family.

I believe the rx-8 was a smart move for Mazda because the higher volume of rotaries sold will make it financially feasible to produce a new rx-7 at a lower cost.

The release of a concept rx-7 next week would be a big way of demonstrating to the public (and some magazines) that the rx-8 is not the "new rx-7" but it really is a different line. I think it will also generate a LOT more buzz about the "return of the rotary". :D

I still feel that the ideal application of the Mazda rotary is in a small sports car. IMHO, Mazda should make the next rx-7 because it will be a different market than the rx-8 and no other car company can do something similar. :o :p

Brian

wakeech

tru dat dawg da rx7 be won inamillun. wot!!
en da RX-8 be sum uva fukki'n fing nawt to be rekoned wit bi sum pees of **** nissan. man word !

(some one had to eventually, right?? i figure it's my turn... jesus, i'd better take some sleeping pills, this simply isn't working out... )

tallguylehigh

Yeah, sorry about the weight of the Z. I was bored on New Years Day and decided to do some off the cuff calculations (I know, I'm a nerd :D ). And the source of the Z's weight came from the C&D comparo with the Z in it. I used this example because I wouldnt have to get up in order to get more information . Thought some clarafication was needed hehehehe.

Buger

Isn't Car&Driver the only magazine that estimated the weight of the rx-8 as being over 3000 pounds? (3000 - 3050?)

If they are in the habit of always adding 150 pounds to their weights, it would match with the 2900 estimate of many of the other magazines.

tallguylehigh

Yeah but this wasn't an estimate, this was data from a production car in a comparison test.

Buger

The tested weight will include the driver while the curb weight will not. Was the weight listed as the curb weight or the tested weight?

ilovepotatos

lmao at Wakeech.
Some of that material was mine!
My lawyer will be reporting to your door soon. I'll see you at the 7-11 at the top of Royal Oak hill.