What is your REAL power to weight ratio?

[rdane]

A little food for thought on the Subbies lovers. They might well be easier to drive in the short term


3.0 liter '79 SC
weight 2625# 14.34 lb/hp
factory 179hp SAE (actual at the wheels was 183hp on my 3.0)
0-60 mph, sec 6.3
1/4-mile, sec@mph 14.7 @ 92

STi
weight 3300# 13.75 lb/hp
300 hp (240 at the wheels) rated from a 20% loss
0-60 mph, sec 4.87
1/4-mile, sec@mph 13.23@104.6


964 C2
weight 2976# 12.4 hp/lb
250 factory (actual 240 at the wheels)
0-60 5.5

3.4 liter '79
weight 2400# 10.7 lb/hp
263 hp (223 at the wheels) rated from a 15% loss
0-60 mph, sub 5 sec (measured)
1/4-mile, sub 14 sec @ 100 (estimate)

BBII
weight 2400# 9.87 lb/hp
chipped 964 3.6
286 (243 measured at the wheels) rated at 15% loss

[mb911]

I admit to being a dummie some times what does BBII mean? Anyhow that looks impresive with the 3.4 I would bet you could get into the high 13s with that ratio. If you had it to do over would you go the 3.4 route?? I have been seriously considering that or the turbo route. Just asking

[rdane]

The fun and fast rebuilt 3.0s are 2400# and 195hp at the rear wheels with a compression bump, SSis and a set of 964 cams.

Makes them 12.3/1. Drop it to 2238 like Eric's and it is 11.47.

Not much to look forward to in fun cars when a SC sells for 10/15K these days
Whos driving a Very light SC?

Ben, BBII is Jack Olsen's car which many judge their own projects by. It is an early '70s body, lots of fiber glass with a 964 3.6 transplant.

If I were to do it again (same budget) I would go to a 3.4 Motronic single plug. More options and easier HP gains starting with Motronic and the 3.2. Basically you can get more for the buck starting with a 3.2.

The down side for me was I already had a very nice 3.0 that had some money into it and needed a valve job.

[dwightp]

Good question!

REAL mass (weight) includes driver, too.

[rdane]

Driver weight is also the easiest and most often changed.
Not really anything the factory would plug into a hp/weight calculation.

Call it a 200# driver.

3500# STi = 14.58
2600# 3.4 = 11.65

I would bet the driver in the STi I ran into weighted a good bit under 200#.

[Grady Clay]

Guys,

REAL power-to-weight means measuring the rear wheel power on a dyno that you can somehow calibrate. I think this is very difficult on a chassis dyno. The only corrections should be the standard SAE adjustments for atmospheric conditions and those should be carefully measured.
The weight should be measured on calibrated scales and the cars in the same condition; say exactly so many gallons of fuel, driver in place or not, spare tire? Tool kit & jack?

The guys who do this professionally, where the calibration is traceable to NIST go to extreme lengths. Of course they never rely on a single measurement but apply statistical techniques on many samples.

Otherwise you are comparing oranges to tangerines.

Best,
Grady

[Craig 930 RS]

My 79SC -- 2490 lbs (1/2 tank gas) , 280 hp at the wheels = 8.89 lb/hp

In the FWIW dept:
A very well driven (and slightly hp/track tire modified) STi was just a *tick* slower on the track acceleration-wise this past Friday 11/5 at Portland Intn'l.

[rdane]

Thanks Grady I see your point. Just don't think the STi numbers are all that impressive compared to many of the cars on this board.

3.0 liter '79 SC
weight 2625# 1/4 tank of gas, 14.34 lb/hp
183rwhp on same dynojet

3.4 liter '79
weight 2400# 1/4 tank of gas, 10.7 lb/hp
223rwhp on same dynojet

3.6 liter '79
weight 2455# 1/4 tank of gas, 8.76 lb/hp
280 rwhp on the same dynojet

Giving a stock STi a huge benefit of the doubt this is what it still looks like.

STi
weight 3300#
300 hp @ crank
11lb/hp using the very optimistic crank numbers

Of course a "slightly modified STi" might be an STi like one here in the PNW that "on a 4WD dyno (was) putting 358hp to the wheels."
That would be a STi at 9.2lb/hp

But then we have Juan's little turbo play toy if anyone really wants to run up the numbers of subbie vs "street" 911

[JonT]

My 3.6 SC with me in it 2900lbs
270 hp 3.6
=10.74 lb/hp

[Craig 930 RS]

A stock STi produces amazing HP AND torque numbers.......but IMO is a complete pig compared to a 964 series and earlier 911 weight-wise.
The crux of comparing numbers *must* be power to weight.
Unfortunately comparing those numbers requires exactly what Dane states --- different vehicles on same dyno for a comparison.
--------------------------------------------------------------------------
I couldn't get a bead on what the HP increase the WRX had.

Had to be perhaps close to 400 hp to almost stay with 330hp and 2500 lbs.

[WydRyd]

Weight ~2600lbs @ ~600 FWHP.

Weight will drop when I replace bulky OEM bumpers and 930 Tail.

[rdane]

found these notes of trivia for the STi.

They can pump them up to 500 HP with factory add ons. They hold a total of 15.9 gallons of gas which relates to a total of 100# if the car is topped up.

Now we have a 3300# car (gas or no gas) and 500 hp with a very optimistic 20% drive train loss. That makes it 425 RWHP and 8.25lb/hp.

Hurray 40K$ STi beats 25 year old SC!

What kind of a 911 turbo will 40K buy you these days?

[Joe Bob]

290 hp @ crank with a 2800 lbs cab....3.6 with a NBD chip and headers.....

[Craig 930 RS]

MikeZ -

Cool! Can you post your dynamometer chart?

[RarlyL8]

SC with mildly upgraded 930 engine.

6.8 lb/HP (FWHP)

[Craig 930 RS]

RarlyL8, can't access your site

[pwd72s]

I'd say a lot depends on whether or not I'm in the car...

[RallyJon]

Hurray 40K$ STi beats 25 year old SC!

Congratulations--you're convinced! I've never seen someone bench race so hard...

[rdane]

[RarlyL8]

Sorry, the site is down. I need to fix that........