Horsepower to weight ratio, I'm puzzled

7125 Views 56 Replies 23 Participants Last post by Titanium Dreams, Mar 5, 2013

jestmaty

Discussion Starter · Feb 28, 2013

At my Miata club meeting tonight, I talk to a long time member who is now temporarily in a 2006 BMW 330i. That thing weighs the same as a '13 SXL, has a 13.5 lb/hp ratio (the optima has 12.3 lb/hp) and is reported to go zero to 60 in about 5.5 seconds. Our SX & SXL's are 6.1? I GUESS it could be the six speed REAL manual gearbox on the BMW... but still. His car felt soooooo strong and quicker than my Optima. Granted, I just turned 2k miles in my optima and am on a week old first synthetic oil change, maybe I can really start to FLOG the cr*p out of it now and see if my butt has the same feel as the BMW grunt

1 - 20 of 57 Posts

NilVlrod

· #2 · Feb 28, 2013

Is that BMW rear wheel drive? That would make a big difference.

jestmaty

Discussion Starter · #3 · Feb 28, 2013

Yes.. boy did it squat when he romped on it

jestmaty

Discussion Starter · #4 · Feb 28, 2013

And I was wrong.. a tad... the times are 5.8 and 14.5 quarter mile.. guys over at turbosonata are reporting 14.4's 1/4 mile passes

richysh

· #5 · Feb 28, 2013

Well, bmw has better weight distribution, it's a RWD, probably better gear ratio, and it's a inline 6. AND it's a BMW lol

nappydrew

· #6 · Feb 28, 2013

The gear ratio makes a lot of difference.

jestmaty

Discussion Starter · #7 · Feb 28, 2013

nappydrew said:
The gear ratio makes a lot of difference.

Ya know... I could find that out... BMW has 6sp manual, OPtima has 6sp automatic/manumatic, I'm off to compare transmission and final drive ratios between the two...

jestmaty

Discussion Starter · #8 · Feb 28, 2013

Ohhhh....

1st gear BMW=4.35, Optima 4.65, difference of 7%
2nd gear BMW=2.50, Optima 2.83 difference of 12%
3rd gear BMW=1.67, Optima 1.84 difference of 9%
4th gear BMW=1.23, Optima 1.38 difference of 11%
5th and 6th are essentially the same on both cars

Final drive BMW 3.15, Optima 2.88

I can't remember at the moment, but I think the lower the number, the lower the engine revs while cruising down the freeway?

That FD might account for a substantial difference?

Sorry if this is irrelevant to pretty much everything, but I was just floored at how powerful that 3.0ltr, 255 hp BMW felt over the optima... the printed 0-60 and 1/4 miles numbers speak for themselves as both cars are pretty much the same in both categories.

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fondupot

· #9 · Feb 28, 2013

Whats the torque and hp specs on the BMW inline 6? Im guessing it has higher torque numbers if it "felt" a lot stronger. Plus being rear wheel drive and having better weight distribution as other have pointed out will make a vehicle feel a lot different than our front heavy optima's.

ozzie

· #10 · Feb 28, 2013

Yeah our cars are definitely set up for the EPA; especially the final drive ratio. That's why these car are rated so high in highway mpg, even if we can't achieve it in real world driving .

bobad

· #11 · Feb 28, 2013

jestmaty said:
I can't remember at the moment, but I think the lower the number, the lower the engine revs while cruising down the freeway?

Correct! Had me going there for a minute.

jestmaty

Discussion Starter · #12 · Feb 28, 2013

BMW 255 hp @ 6600rpm, 220 torque @ 2750.. for the record, his 6yr old BMW is riddled with minor, nagging problems throughout. For instance, his power retracting mirror quit working correctly last night at our meet up. It folds past it's stop point and points straight toward the front of the car. When he presses the button to close it up, it works. Again, when he 'opens' the side view mirrors, the driver's side mirror won't stop at the dent where it's supposed to... it point straight ahead

Bunch of other stuff too

bh_trade

· #13 · Feb 28, 2013

Most car mags consider BMW to rate their engine output very conservatively yet none of them have ever accused Hyundai/Kia of doing such. Throw in a more aggressive gear ratio and no surprise whatsoever that a 255 hp Beemer smokes a 274 hp Kia of equal weight

RedHotDamn!

· #14 · Feb 28, 2013

bh_trade said:
Most car mags consider BMW to rate their engine output very conservatively yet none of them have ever accused Hyundai/Kia of doing such. Throw in a more aggressive gear ratio and no surprise whatsoever that a 255 hp Beemer smokes a 274 hp Kia of equal weight

^this, + RWD vs FWD launching

e-squared

· #15 · Feb 28, 2013 (Edited)

Like everyone is saying, it is all about torque multiplication to the ground. That is why I had to keep telling the dealer that my 240hp Altima was quicker 0-60 than the Optima. And of course they would come back and say "But this has 274hp". Hp does not accelerate a car, torque does and multiplying it more helps the most. (I will wait for the debate on this.)

The other thing that people forget about is that you will never have 269lb-ft of torque at 1750rpm (limited boost in 1st and 2nd) and then you will never go back to that rpm with max boost. Oh and the other thing, the wheels would be spinning if this did happen.

Tino Grad

· #16 · Feb 28, 2013

Acceleration is almost entirely a function of torque and the gearing. I dare say if the gear ratios were the same and the Optima turbo was a manual - different story.

RedHotDamn!

· #17 · Feb 28, 2013

e-squared said:
Like everyone is saying, it is all about torque multiplication to the ground. That is why I had to keep telling the dealer that my 240hp Altima was quicker 0-60 than the Optima. And of course they would come back and say "But this has 274hp". Hp does not accelerate a car, torque does and multiplying it more helps the most. (I will wait for the debate on this.)

The other thing that people forget about is that you will never have 269lb-ft of torque at 1750rpm (limited boost in 1st and 2nd) and then you will never go back to that rpm with max boost. Oh and the other thing, the wheels would be spinning if this did happen.

just to note, compressor surge would be occurring if peak boost (17.4 psi in manifold...2.4 PR on compressor map) was met at 1750 rpm

Also, OP... You did not multiple final gear ratios..they have a stronger/more aggressive first, we have a stronger(but shorter) 2nd, equal(only .02 off) 3rd. I know on our cars you just almost reach 60mph in 2nd, but not quite. So with they're longer 2nd gear (paired with stronger 1st gear) they are hitting 0-60 in 2 gears, ours are right at/after 3rd shift.

jestmaty

Discussion Starter · #18 · Feb 28, 2013

bh_trade said:
Most car mags consider BMW to rate their engine output very conservatively yet none of them have ever accused Hyundai/Kia of doing such. Throw in a more aggressive gear ratio and no surprise whatsoever that a 255 hp Beemer smokes a 274 hp Kia of equal weight

I suppose he's much more involved with the BMW forums, as we are with our Optima forum and I even asked if the "under the counter" talk about understated hp numbers ever come up. He never answered me, but I suspect by my butt-o-meter that there is more hp than 255 in the inline 6! Red Hot, Tinograd, e-squared all brought up fantastic points... thanks for informing me a bit more of the dynamics regarding acceleration and torque. Lastly, I forgot that the boost is limited in 1st and 2nd in the optima

071K

· #19 · Feb 28, 2013

If acceleration on the street is your goal, you're using the wrong tool. My 07' GSXR 1000 (with several performance mods), has 1.75 lbs/hp. Shifting at redline in 1st gear nets 135 mph. Potential 1/4 mile time is in the low 9 sec range, top speed is 200 mph +, 0 - 60 is somewhere around 2 seconds. All this for less than 1/3 the price of my SXL. I quote the 1/4 mile time as "potential" because I'm not a drag racer and don't have the necessary skill to launch it at the strip.

bobad

· #20 · Feb 28, 2013 (Edited)

e-squared said:
Hp does not accelerate a car, torque does and multiplying it more helps the most. (I will wait for the debate on this.)

Mostly agree, but it needs pointing out that a 6 speed transmission equalizes things somewhat. The car with less torque and the same HP will have to shift at higher RPM. Still, the car with the most torque and RWD usually wins.

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