Jmc007

"This Relative Horsepower Calculator determines the relative torque and horsepower available at any temperature, barometric pressure, humidity, and altitude. The calculations are derived from public domain information, SAE J1349 Revision, June of 1990. The calculator shows you how much the air conditions on any given day will alter the horsepower of a normally aspirated internal combustion engine."

Relative Horsepower Calculator

Here is an example for my car (2005 SS-SC, 2.9" pulley, K&N filter, 42# injectors, shorty header, stock DP, 2.5" custom catback) for this very afternoon in Canmore, AB at around 2:00 PM, some data logged on the Aeroforce Interceptor (MAF lb per min) and other data from the Weather Network or from driver information center (air temp).

Outside Air Temperature: 64 Degrees F
Ambient Barometric Pressure: 29.88 Inches Hg
Ambient Relative Humidity: 18%
Physical Altitude: 4350 Feet

From the above website calculation:

Calculated Relative Horsepower To Rated: 86%
Calculated Dynamometer Correction Factor: 1.163

From Aeroforce: 26.65 lb per min (MAF) @ 6918 RPM (cut-off set at 6900 RPM)

26.65 lb per min x 10 BHP per lb per min = 266.5 BHP (uncorrected)
266.5 x 1.163 (correction factor) = 310 BHP (corrected)
310 BHP x 0.85 (drivetrain loss is 15%) = 263 WHP.

Other data as recorded on the Aeroforce Interceptor:

Max boost: 12.3 PSI
Boost pre-supercharger: 0.3 PSI (vacuum)
Injector: 13.2ms @ 6918 RPM (76.1% calculated duty cycle)
02 sensor voltage: 910 mv (commanded 12.0:1 AFR with HP Tuners)
MAF: 9433Hz
Knock retard starting at 0.3 degrees from 6271RPM up to 2-3 degrees at cut-off
Fuel octane rating used is 91 only.

That is it for today.

mrbelvedere

iTrader: (3)

nice write up man good to see you back

Staged07SS

iTrader: (25)

Nice!

Subd....

Jmc007

Did another pull tonight ... picked-up 9 whp and all the Knock Retard gone up to 6900 RPM, only by switching from 91 to 94 octane. Calculated and corrected WHP (from datalogging and adjusted to weather conditions) went from 263 to 272.

Jmc007

Did another pull with same setup (and same tank of gas), in quite different weather conditions:

Colder 64.4 degrees F (ambiant)
30.3 in HG (air pressure)
Humidity 33.5%
3510 feet altitude

28.53 lb per min (MAF)
880mv
Coolant temp 176 degrees F
IAT2 around 150 degrees F

"Dyno" correction factor (from formula in post #1): 1.108

Calculated horsepower: 269 SAE WHP; that is pretty consistent with last pull which was 272 SAE WHP. Now I hope to be able to do the next test with the Weapon-R intake, and possibly with their Ram Air setup as well. Results soon to come ...

Jmc007

And one last pull before to install the WR intake, again in quite different conditions. Still running 94 octane, now commanded 12.25 AFR and rev limiter adjusted to 7000 RPM, still on stock timing:

53 degrees F (ambiant air temperature)
29.68 in HG (air pressure)
Humidity 62%
3367 feet altitude

28.53 lb per min (MAF)
850mv
Coolant temp 176 degrees F
IAT2 lower around 125 degrees F

"Dyno" correction factor (from formula in post #1): 1.117

Calculated horsepower: Roughly the same as before at 271 SAE WHP. Gotta love the corrected numbers ...

Staged07SS

iTrader: (25)

I'm filling up with Sunoco 260GT100 this weekend.

I will have to post my results in this thread once I perform some logs.

I enjoy reading your updates.

Jmc007

Hey Staged07SS any results with the Sunoco race fuel?

Staged07SS

iTrader: (25)

Yes.

I will post them tomorrow

DCOBALTSS

iTrader: (1)

On the interceptor let say it tells me 366hp how do i correct that?
i was in fourth gear full throttle

snoftall

Not sure how accurate this is going to be if you are boosted...I don't think I would trust this as being a good representation to calculate or estimate horsepower...

Jmc007

The key is by using the right multiplication variable (lb per min. per HP) which does differs for boosted applications and normally aspirated applications. Again all of this is theoritical, but ambiant air is affected by barometric pressure and temperature in the same way for both applications.

In regards for the question for the Interceptor HP, I would be curious to know from which sensor it is extrapolated, but I do not have this feature on my older model Interceptor.

Staged07SS

iTrader: (25)

The interceptor takes its horsepower reading from the MAF sensor.

My interceptor has almost always showed the same horsepower readings no matter what mods I've done to the car. I tend not to use it, because it isn't very accurate.

I will be running some more tests this afternoon after work. It will only be in the 50's today so I'm interested to see what my car will be flowing. On normal warm days (mid 60's - mid 70's) my cars flows 35.03 lbs/min. On cooler days (low 50's - low 60's) I have logged 36.41 lbs/min.

I'm starting to like using trap speed to determine power. I took my car out on the turnpike Monday, and ran it through the gears with my properly calibrated Gtech Pro RR.... With a shitty 2.334 60' time I ran the following:

9.1 in the 1/8th mile, but it was at 85 mph, and

13.833 in the 1/4 mile at 108 mph.

Elevation was 1350', humidity was 30%, and pressure was 28.5

My mph puts me around 270-280ish horsepower (270-280ish is right around what I dyno'd last year).

Staged07SS

iTrader: (25)

Here are my results with Race Gas/High Octane Mode:

Date: 10-21-11
Intake Air Temperature: 55 Degrees F
Ambient Barometric Pressure: 29.93 Inches Hg
Ambient Relative Humidity: 48%
Physical Altitude: 1087 Feet

From the above website calculation:

Calculated Relative Horsepower To Rated: 99.8%
Calculated Dynometer Correction Factor: 1.002

From Aeroforce: 36.14 lb per min (MAF) @ 6970-7250 RPM (Rev limiter set at 7250 RPM, shift point is 7000 RPM)

36.14 lb per min / 0.108 = 334.6296 BHP (uncorrected)
334.6296 x 1.002 (correction factor) = 335.2989 BHP (corrected)
335.2989 BHP x 0.85 (drivetrain loss is 15%) = 285.004 SAE WHP

Other data as recorded on the Aeroforce Interceptor:

Max boost: 16.3 PSI
Fuel octane rating: Sunoco 260GT100 (CAM2) High Octane Mode
Timing Advance: 26.5*
Knock Retard: 0.0

Mods:

H62 Hybrid Blower
GMR Stage 3 76mm (2.992") pulley
GMR Stage 3 PCM
GMPP 42 lb/hr injectors
Modified Airbox with K&N E-0777
Badmab Shorty Header
Modified Stock Downpipe
Corsa Catback Exhaust

These results are very close to what I dyno'd last year. Not bad!!

Micro

JMC007, the work you did is comparible to some data I gathered and discussed in this thread:
https://www.cobaltss.net/forums/2-0l...epower-135111/

I like what you have done.

Staged07SS

iTrader: (25)

Nice thread man.

I also have my Gtech Pro RR setup to read horsepower and torque very well.

Sometimes I'll get an erratic reading, but 99% of the time it's spot on.

Horsepower readings on the Gtech Pro are much lower than you would see even on a Mustang dyno. I tend to ignore the hp/tq outputs, and look more at the graphs & times.

Jmc007

Nice results man. I knew your corrected numbers would be higher than mine. H62 and 100 Octane vs M62 and 94 octane.

Jmc007

Yes I think it could be similar, but it seems a bit easier using the website's calculator which is derived from SAE J1349 procedure.

Jmc007

Got the Weapon-R installed (will test soon "dyno" numbers soon):

https://www.cobaltss.net/forums/6111744-post10.html

Jmc007

Here is the first test done this morning (10:30 AM) with the Weapon-R; looks like not much changed since the other tests with previous drop-in filter. Yesterday I had reset the PCM by disconnecting the negative terminal of the battery for about 2 hours. So now I still see up to 0.2-0.4 PSI of vacuum (pre-supercharger) from mid-range to WOT. Still running on 94 octane fuel. Test always done in 2nd gear:

Outside Air Temperature: 44 Degrees F
Ambient Barometric Pressure: 30.02 Inches Hg
Ambient Relative Humidity: 63%
Physical Altitude: 3415 Feet

From the above website calculation:

Calculated Relative Horsepower To Rated: 91.8%
Calculated Dynamometer Correction Factor: 1.09

From Aeroforce: 28.53 lb per min (MAF) @ 6900-7000 RPM

28.53 lb per min x 10 BHP per lb per min = 285.3 BHP (uncorrected)
285.3 x 1.09 (correction factor) = 311 BHP (corrected)
311 BHP x 0.85 (drivetrain loss is 15%) = 264 WHP.

Other data:

IAT2 around 142F
Coolant 178F

Guess it is time to give some more timing advance; still running on the stock timing table :

Staged07SS

iTrader: (25)

Thanks