S/C Horsepower: Do the Math

[Baxman]

Our VX comes with 215 hp from the factory. This measurement is taken at the flywheel, I believe. Horsepower to the ground is actually ~165 hp, but hp ratings of all vehicles are typically the higher flywheel value.

John Finnell (dynamometer testing) tells us that the the Alpine S/C "rear wheel gain is 47+ hp".

Since ~25% of the flywheel hp is lost to drivetrain friction, then the blower produces a gain of ~59 hp over stock at the flywheel where hp is measured/rated by manufacturers.

Therefore, the VX with only the S/C modification should be rated at 278 hp. If the same formula can be applied to torque: 288 lb/ft.

Experts? John?

[Tone]

I will split the cost of a DynoJet run with someone who has the SC installed so you can see the real number that is produced on your vehicle. Check this link for a facility near you - http://dynojet.com/lauto.shtml

Remember, you will need to disconnect your front driveshaft unless you use a 4WD Dyno even if you have the TOD disconnect installed.

[Baxman]

The dyno run is ~$200?

How much trouble is it to disconnect the front driveshaft? If its not a PITA, I'll do it!

Here is FeatherFoots (John Finnell) reply from V-Mag:



close - very close.
Isuzu said that the FW HP was 285HP. our calcs showed 280 with the stock exhaust.

Add the PV and the 18 becomes 22FWHP on a NA engine. At the same percentage gain (27.4%) that then becomes 28 HP showing a total of 308FWHP.

Based on those figures a claim of 300+ HP would be ligitimate. That also is the same number (extrapolated due to speed limiter in the ECM) my 5.3L GMC is putting to the ground with just exhaust work.

Butt dyno sez probably so. All I know is that the SC makes for wide eyes from others when used judiciously.

[Tone]

$70 - 8-10 bolts - easy.

[Baxman]

Found a shop near me with a DynaJet. They charge $95 + $70/hour for R&Ring the front D. shaft. I'm having it done on my lunch hour on Friday. How long should I expect R&Ring the DS to take?

[Tone]

5 minutes to remove the DS. Look forward to the results. Email me the run(s) and bill and I’ll paypal ya. Thanks!

Just a thought, it would be nice to have a run with the SC belt disconnected that would give some approximation of a baseline w/o SC and confirm that the vehicle can operate if you were to loose the belt.

[Baxman]

I'll do it. The OEM intake manifold looks pretty sophisticated, how much difference might there be between the S/C'd engine w/o belt vs the stock set-up?

Rick

[Tone]

There could be a substantial amount of difference not to mention the effect of the rotors freewheeling. But I have a baseline run on mine with just the muffler and airfilter change so we’ll be able to calculate the difference pretty easily and it will be good info to have. Some have promised to dyno before and after the SC install but none have been able to.

My own kit should be here in the next week or so and I’ll be able to lay the runs on top of each other to get a true comparison when I dyno mine.