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  • #16
    Originally posted by John
    So, my recommendation
    would be on any power number you read figure in 10% error and
    if its a dynojet, subtract 20% for real world power.

    John
    A dyno is really best used as a check against itself -- in other words, do a baseline run. Then, make whatever modifications you're testing (e.g. adjusting fuel maps), and run again on the same dyno. The resultant number vs. the baseline will give you a relative idea of that modification's merit. Comparing any dyno to any other dyno yields nothing more than ballpark data -- even the same dyno on different days can yield different result (even accounting for humidity/temp etc.).

    One thing to consider when looking at dyno numbers is which correction factor was used -- STD reads the highest numbers, while SAE numbers are a little more realistic (for example, 259 STD HP is equal to 248 SAE HP). Most people tend to post STD numbers.

    I think John's 20% reduction on dynojet numbers is wrong. A good-running, stock-engined E30 M3 with a chip will generally record around 160 SAE RWHP on a Dynojet 248C. Using a 17% correction factor for flywheel HP, this yields about 193 HP, which is probably pretty close to correct.

    Mustang dynos are great for tuning because you can lock the RPM to help tune load at given RPMs -- thus they are a great tuning tool. But, you can't compare Mustang numbers to Dynojet numbers (as I said above, you can't really even compare Dynojet numbers to Dynojet numbers).
    Jefrem Iwaniw

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    • #17
      This thread is interesting. I also just had Stu at Schatz and Krum dyno my 2.3, and the baseline was quite low at about 150 @ the wheels. We also just did a unichip/MAF conversion, and picked up nearly 25 whp (I'll post the dynos when I get them).

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      • #18
        Originally posted by vlksdragon
        This thread is interesting. I also just had Stu at Schatz and Krum dyno my 2.3, and the baseline was quite low at about 150 @ the wheels. We also just did a unichip/MAF conversion, and picked up nearly 25 whp (I'll post the dynos when I get them).
        So your base was 150 HP, and your final was about 175 HP right? You have any other mods that would give you roughly 12 HP difference than my peak? Im guessing that we would be in the same HP league since both our AFM's were removed. If you are basicly stock, then I may have an angine problem.

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        • #19
          Originally posted by wookie1976
          So your base was 150 HP, and your final was about 175 HP right? You have any other mods that would give you roughly 12 HP difference than my peak? Im guessing that we would be in the same HP league since both our AFM's were removed. If you are basicly stock, then I may have an angine problem.
          150 is kinda low, do you have the EVo cam gear?

          IMHO, removing the AFM is good for about 10% across the board on HP and about 15% on LOW end torque, and about 100% on FUN factor!

          Do not click
          At least it's German

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          • #20
            It is interesting to ask which numbers are "true" accurate horsepower readings, which are low, and which are inflated.

            My engine on the Mustang dyno put out 203. Add 17% drivetrain loss, which should give about 238 flywheel horsepower. The same as a Sport EVO.

            But my engine is pretty much exactly a Sport EVO copy, except with much higher (11.6)compression and hotter (Schrick) cams.

            IF all is well, shouldn't my motor be noticeably beyond sport EVO spec as far as output? Or are the BMW specs for the Sport EVO inflated? Or is the Mustang dyno underating my engine?

            Stu at Schatz and Krum estimated at the time of the test that my motor would have around 260 flywheel horsepower. Where does he get that, when his own dyno only measured 203 at the wheels? I am sure there is not that much loss through the drivetrain.

            I agree numbers in themselves don't mean much, but on the other hand not knowing what is the accepted standard makes it hard (impossible) to accurately compare anything.
            Last edited by Ironhead; 12-04-2003, 02:59 PM.

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            • #21
              Ironhead,

              If you add in about 20% drivetrain loss, you should be making about 254 HP at the flywheel. Now I'm not sure that this is the correct number, but it does somewhat agree with Stewarts number of 260.
              However, I feel that 20% losses might be a bit on the high side too. Even at 17% losses (which I figure is closer to ideal), you would have around 245 HP at the flywheel. If you do a similar analysis on my numbers than I should be, according to the dyno making about 196 HP (17% losses) or 203 HP (20% losses) at the crank with the alpha n conversion. Both of these additionally seem on the low side.

              This may account for the fact that his dyno is reading on the low end since both you and I should be making better power than what our numbers tell us.

              Im thinking about going to Dynospot in the Bay Area soon so I can get some dynojet numbers for comparison. Yes I know that the numbers are really useless for comparison unless you dyno on the same machine/conditions/calibration etc., but Id like to see for myself how I stand on a different machine that has done many S14s in the past.

              The primary reason I went to Stewarts place (besides that he is a friend of mine and general nice and knowledeable guy) was to tune my setup with a constant load with a wideband O2. I feel that I have accomplished at least that portion of that, so anything number wise from here on out is simply bragging rights and personal interest.

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              • #22
                Originally posted by Ironhead
                My engine on the Mustang dyno put out 203. Add 17% drivetrain loss, which should give about 238 flywheel horsepower. The same as a Sport EVO.
                Oh, I forgot to mention that your conversion from wheel HP to flywheel is not correct. (I'm not trying to insult your inteligence I promise! Its just a common math error)
                I think that this has also been stated in a recent thread here, but Ill say it again.
                You originally stated that 203 HP should be 238 HP at the flywheel at 17% losses (203 * 1.17) = 238
                The problem is:
                If you multiply 238 HP by .83 (or 17% losses) then you dont arrive at the original number of 203, you instead get 198 HP. Why? Because you need to multiply by the inverse of that number ie: 203 * ( 1 / .83 ) or 203 * (1 / (1-.17) = 244 HP
                244 * .83 = 203, see now the numbers work out

                Its that fraction / multiplication thing.
                Multiplication: 1/5 * 1/8 = 1/40 = .025
                Division: (1/5) / (1/8), you must first flip and multiply to get the answer: 1/5 * 8/1 = 8/5 or 1.6 You can do this easier by taking the inverse and multiplying which is why the above formula works.
                Sorry Im not a math teacher, so this may seem confusing.
                Last edited by wookie1976; 12-04-2003, 03:50 PM.

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                • #23
                  Im thinking about going to Dynospot in the Bay Area soon so I can get some dynojet numbers for comparison
                  Yeah I have thought about doing the same thing. Not so much for the dyno results, but I am thinking of having a custom chip burned. Who do you think, Dynospot or Schatz and Krum for that?

                  I see your point about my math. You are right.

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                  • #24
                    best thing to do is this, find one shop with one dyno, and always use that. starting from stock to the day you put on the last HP mod. peak numbers are whatever, all dynos are off if you compare them, but if you use one dyno, the gains from a mod are all you should be looking for, who cares if you only made 163 wheel hp,what if you gained 25 whp from the AN? yea, 163 seems low, but how does the car feel? does it pull? compared to a stock car?
                    "Just road, seat, ASS; THE END!" - Jeremy Clarkson
                    "If you had a choice between a million dollars and world peace, what would you get for your E30 M3?" - ItsNotTheNissan
                    onfirelabs.com twitter.com/suga_shane

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                    • #25
                      Yes the car definately pulld harder than it did stock. I also gained many other side benifits like snapier reving and improved startup. I agree on the point that one dyno is good to stick with to see overall changes in mods. I fully intend to return to Stew's place for any further HP after mod. comparisons. I just wanted to see how far off the numbers were between a dynojet and the mustang.

                      Hey Ironhead,
                      A few of us E30 M3 freaks were thinking about going down to dynospot sometime after the holidays. If there is a large group of us, they might charge a lower group rate. Let me know if you are interested and Ill call to see if I can work out a better price. Besides, its an excuse to hit the highway in group caravan.

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