Maximum HP

Discussion in 'Other Manufacturers' started by AudiTT, Mar 26, 2008.

  1. SlowHands

    SlowHands Hypermiling Ironman

    Count me in as a mostly well sorta mostly reformed motorhead. Sure I have xgauge that reads torque and another that reads hp... but that's for the curiousity of seeing well how much er little torque or hp does it take to push this brick through the air at 45 mph or whatever. The little gremlin on my shoulder MADE ME dig to about 1/2 throttle in 5th gear at about 45mph in the iCDTi cuz I just had to know... and yep that thing pulls real nice :D

    I raced both legal and not so legal, great gobs of fun for sure. Hypermiling has been great gobs of fun ... still going for maximum but just a different maximum.

    I agree w/Mr. Bill on doing a real dyno instead of street dyno.
  2. AudiTT

    AudiTT Member

    I know that this is the wrong forum to talk about peak HP but when I did a search on ScanGauge I got this forum. Now the gauge can be used to monitor mpg as all of you indicate, but it can also be used to monitor many other useful automotive functions, such as:

    TPS: Throttle position sensor 0-100%
    fIA: Intake Air Temps (Temperatures at the intake manifold)
    fWT: Coolant water temperature
    HPR: Horsepower
    VLT: System Voltage
    IGT: Ignition timing (advance)
    LOD: % Power request
    Closed/Open loop: Fuel management and transition point from O2 control to WOT
    STF: Short term Fuel trims (Idle % on Block 32)
    LTF: Long term Fuel trims (Partial throttle on Block 32)
    OX1: #1 O2 sensor output, 0-100
    OX2: #2 O2 sensor output, 0-100
    MPH: Digital speed reading from Speed sensor
    RPM: Digital RPM's

    I get 28.7 mpg on my TT pushing it like I stole it. That is an economy that makes me proud without trying any harder.
    I am sorry if I have offended anyones sensitivities about what makes me personally happy but that is why God created colors. We just happen to get our kicks different ways, and I can readily see how getting a better mpg than the next person can be a real challenge and a lot of fun, but I'm not ready yet to give up my toy.

    I am not trying to convert you to my way of thinking, I was just asking a question of a group of people who are very savvy about the workings of the ScanGauge.

  3. shifty35

    shifty35 Well-Known Member

    Trying a pull uphill will distort readings, because the horsepower calc makes assumptions using vehicle weight and acceleration rate. You have to be on a perfectly flat surface for this to work.

    If this is not how the calculation is done, then it's probably not accurate anyway.

    Try posting in the SG2 forum under hardware - someone there may be able to help you write an X-guage to capture maximum HP reading.

    I've tuned many, many Hondas (ecu chipping, A/F, etc) and I can attest a dyno is the way to do serious tuning. A number from the SG for HP is pretty much meaningless unless you can make changes and perform the exact same pull in the same weather conditions with the same weight in the car.
  4. phoebeisis

    phoebeisis Well-Known Member

    I kinda wonder about just what the HP reading is.You could make a pretty good guess on the horsepower from the fuel used/sec.Most modern cars have about the same compression,have very little valve overlap,and they spit very little unburned fuel out the tailpipe.
  5. AudiTT

    AudiTT Member

    Thank you Ben,
    I'm sure that you're right. I have done all of my road testing on perfectly flat surfaces. I'm not sure if you're familiar with Ross-Tech's "Butt Dyno" approach @:

    but it really gives good results because it includes wind resistance, which the shop dyno does not, on top of the standard mechanical losses & friction. It does this by the deceleration part of the data gathering.

    I have used this approach and I get 225 wheel HP. This corresponds to the Vag-Com (from Ross-Tech) torque, and therefore HP, calculation of also 225 HP.

    The ScanGauge results, I'm told, gives "Crank" HP. On my indeterminate runs I get 275 HP. This is right in line with a 20% drivetrain loss for the TT quatro.

    It all stacks up and the data corroborate each other. I will be doing a shop Dyno test in the near future but haven't gotten around to it yet.

  6. AudiTT

    AudiTT Member

    Hi Charlie,
    You're right, but it is easier to measure the amount of air flowing into the engine. The following quote gives a good approximation for HP based solely on the amount of air that the engine can swallow. The more air that the engine burns stoichiometrically with fuel the higher the horsepower.

    "Your peak airflow should be roughly 0.80 times your horsepower. So, if you have a stock 150 hp 1.8T, expect around 120 g/s. "


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