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350Z power output seems low in the example??

EFI Tuning Fundamentals

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Hi,

I've got to the video on table resolution and the 350Z shown in the example produces approx. 200hp @ 6100rpm. I understand that the power output isn't really the point of the video but could anyone help me understand why this is significantly lower than what a stock 350Z produces at peak? I thought it might be that the throttle doesn't seem to be wide open or that whp is just that much lower but I'd just be guessing. The tuning world is all new to me so any help from some more experienced members would be really appreciated :)

Thanks

I havent seen the video you are talking about, but I would hazard a guess that it is being measured on a chassis dyno whereas you are comparing it to factory-quoted power figures which would be measured at the flywheel with many of the parasitic losses removed. 200HP at the wheels sounds about right for one of those in my experience. On a chassis dyno you lose power through the transmission, diff, driveshafts, cv's, the tyre/roller interface, all the dyno bearings and roller linkage etc. Also, most chassis dyno control systems only have quite basic inertial torque compensation so during a ramp run not all of the power that is lost into accelerating all the heavy rotating drivetrain parts such as the flywheel, diff, wheels etc is considered.

It also underlines the importance of comparing like to like - by that I mean doing any comparisons of tuning, or other changes, on the same machine, preferably with the same operator. There can be significant differences between machines, even the same make and model, and different operators may have different ways of doing things - for example the engine temp's, the gear used, etc.

This is a good question and there's a lot of misconception about the purpose of a dyno in the tuning scene.

A chassis dyno shouldn't be used to give peak power figures. There are many factors that will affect the numbers shown in the dyno software, like the dyno type (load cell vs roller weight, inertia vs eddy current), the way the car is strapped down, outside temperature, to name a few more than Adam and Gord pointed out.

A dyno is a comparision tool between runs. A good one will give repeatable numbers between them. If you don't do anything to the calibration and you do two runs back to back, you should have the same numbers and curve shape. Once you get to know your dyno and if you work on the same cars with similar mods, you will start to get trends and then you can start to interpret power figure, like if you're 30 whp under what your used to, it could indicates a problem with the car.

Finally, here's a video about why you have to be careful trusting power numbers. Of course, it's made with humour, but the point is that it's very easy to manipulate them!

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