BBQdDude Posted February 22, 2017 Report Share Posted February 22, 2017 A friend in our car club and I have the same year and model car. Same tuning shop. Same bolt ons. Same temperature and humidity in the shop. I got mine tuned last month. He got his tuned last week. He posted the dyno and he ended up with 18WHP more than me. In talking with the owner via posts on FB he stated my "chart" was done in a 5th gear pull and the other members chart was done in a fourth gear pull. Now the question: Why would they use 4th and fifth gear in this scenario for quoting maximum HP and torque. The owner never responded to that question. Quote Link to comment Share on other sites More sharing options...
Geeto67 Posted February 22, 2017 Report Share Posted February 22, 2017 From my very limited experience in this.... typically when you dyno a car you want to do it in the gear that will yield a 1:1 ratio to get the most accurate reading. In most cars this is 4th gear (in some six speeds but not all it is 5th gear), but I don't know which gear that is in a 370Z. Let's assume the 370Z has a 1:1 4th gear, then if they dyno'ed the car in a 5th gear overdrive, and their dyno doesn't have the software to compensate for the overdrive (or they forget to enter it), then the hp reading will be higher rather than lower. Is it accurate? meh not really, Figure it is about a 5%-10% error between the two. Now if we assume 5th gear is the 1:1 ratio then running the car in 4th would mean a higher reading for the car run in 4th gear, assuming no adjustments were made to the dyno. Gears lower (numerically higher) than 1:1 are a torque multiplier and overdrives increase wheel speed - 1:1 is the the most accurate measure of hp and torque (it's the low valley - In underdrive the rolling road is going to measure a torque multiplication of 1.2 as 1, and in OD like 6th it will measure the faster wheel speed as a lower rear end gear than it is). I quickly google searched the ratios and found the ratios for a 2011 370 z are: 370's final drive is 3.692. Here's a complete rundown on the gearing... 1st - 3.794 2nd - 2.324 3rd - 1.624 4th - 1.271 5th - 1.000 6th - 0.794 Reverse - 3.446 Final Drive - 3.692 So the dyno guy who ran your car did the right thing. The guy who ran the other car (assuming it has the same gearing) didn't run it right. Remember the rolling road is a measure not of what the engine is making but what is getting to the ground through the drivetrain - so any funny business with the gears is going to skew the numbers. cue people to tell me I've screwed up the explanation, but the end result is the same - if it wasn't run in a 1:1 ratio and the dyno wasn't adjusted to compensate then it is inaccurate. Quote Link to comment Share on other sites More sharing options...
Dammit Charlie Posted February 22, 2017 Report Share Posted February 22, 2017 As much as this pains me to say it, Geeto is right. Quote Link to comment Share on other sites More sharing options...
RyM3rC Posted February 22, 2017 Report Share Posted February 22, 2017 Maybe he had dat super sunoco 94 in there? Some sneaky cheater NOS octane bewst in the tank? He had better synthetic oils than you did. And he probably drove around WOT all day beforehand to really clean it out for max powerz! Also I heard his tires were prepped for max dyno-queenishness. But yeah, apples to oranges without being in the same gear. I wouldn't lose sleep over something like that. Quote Link to comment Share on other sites More sharing options...
99StockGT Posted February 22, 2017 Report Share Posted February 22, 2017 Couldn't have said it better myself Geeto is completely right. Likely just due to gearing, though you DO have some margin for error on these things, A=A isn't always the case. Factor in mileage, fluids, etc can give a bump up or down here or there as well. Quote Link to comment Share on other sites More sharing options...
aussiek2000 Posted February 23, 2017 Report Share Posted February 23, 2017 Gearing aside, not all cars make the same power. Mine and a buddies G8 are very similar builds. But his car makes about 20hp more than me and runs .2-.3 faster in the 1.4 Quote Link to comment Share on other sites More sharing options...
Cordell Posted February 23, 2017 Report Share Posted February 23, 2017 Not sure why he would've dyno'd it that way. Maybe your car spun on the dyno, tuning can still be done in 5th and reduce wheelspin. Hard to say. Quote Link to comment Share on other sites More sharing options...
BBQdDude Posted February 23, 2017 Author Report Share Posted February 23, 2017 Geeto, thank you for that. it makes perfect sense to me. Thank you all for the input. Quote Link to comment Share on other sites More sharing options...
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