dynos suck
The dyno numbers look good. Nice to see some posted!
As far as gearing... the higher gears will cut the torque down, but the power band will keep the same shape (the engine makes basically this or that at each rpm, and that remains constant) Typically you can get higher horsepower numbers from higher gears.
I'm not exactly sure how some dynos compensate for gearing, as no car has a true 1:1 gear typically, so that would mean every dyno would be off by a certain amount, but that is not generally an accepted belief, and as far as I know it does actually modify out the numbers slightly to compensate for gearing.
As far as the title of the thread... you are exactly right. Dynos do pretty much suck. Reason being there is typically a 5 hp variation in each run and so forth, so for minor variations (like CAI) you'll have a really hard time finding a good correlation. If you don't believe me, go run your car 8 times 1 hour a part on a dyno and then compare. You'll see variation. Since I doubt anyone is going to do that on an actual chassis dyno you'll just have to trust me or something. But there is a certain amount of variation in every dyno (some better dynos it is less than 5 hp... but probably around 2 hp)
Additionally, dyno tuning is actually not truly accurate. The reason being that even with advanced dynos like Mustangs that apply load to the wheels past intertial loading (which is all a dynojet does) it still does not truly simulate what the road does to the car, nor the weight transfers and so forth. Often people will tune on the dyno and then run on the street and find the car runs somewhat poorly, or is not as powerful as they expected. On a dyno you can't simulate all the dynamic loads that are present on the street, nor can you simulate the way the air flows over and through the car and alters the way the engine gets air and sees loads at given speeds. That is why the best way to tune is by knowledge, on the street, with a driver who covers all the types of car usage (roll ons, hard acceleration, mild acceleration, shifts, etc). A dyno can be helpful to allow you to identify where in the area of 12-13 afr your engine makes peak power, but then you need to try and tune the car to make those afr's and so forth. I can tell you from experience tuning a car that even something as simple as a different gear will actually cause the way the engine is loaded to result in different afr's. That is a nuance you probably won't see on most dyno tunes and so forth.
So yeah... dynos are good for benchmarking where you are, and finding out how your modifications are helping you along, and for getting a general idea of how two things may compare. But they certainly are not the bible for how a car performs. And for the record. 1/4 mile times are even worse for judging car performance. There is a reason one guy can have a 2 second 60' and another guy have a 3 or 4 second... in the same car.
As far as gearing... the higher gears will cut the torque down, but the power band will keep the same shape (the engine makes basically this or that at each rpm, and that remains constant) Typically you can get higher horsepower numbers from higher gears.
I'm not exactly sure how some dynos compensate for gearing, as no car has a true 1:1 gear typically, so that would mean every dyno would be off by a certain amount, but that is not generally an accepted belief, and as far as I know it does actually modify out the numbers slightly to compensate for gearing.
As far as the title of the thread... you are exactly right. Dynos do pretty much suck. Reason being there is typically a 5 hp variation in each run and so forth, so for minor variations (like CAI) you'll have a really hard time finding a good correlation. If you don't believe me, go run your car 8 times 1 hour a part on a dyno and then compare. You'll see variation. Since I doubt anyone is going to do that on an actual chassis dyno you'll just have to trust me or something. But there is a certain amount of variation in every dyno (some better dynos it is less than 5 hp... but probably around 2 hp)
Additionally, dyno tuning is actually not truly accurate. The reason being that even with advanced dynos like Mustangs that apply load to the wheels past intertial loading (which is all a dynojet does) it still does not truly simulate what the road does to the car, nor the weight transfers and so forth. Often people will tune on the dyno and then run on the street and find the car runs somewhat poorly, or is not as powerful as they expected. On a dyno you can't simulate all the dynamic loads that are present on the street, nor can you simulate the way the air flows over and through the car and alters the way the engine gets air and sees loads at given speeds. That is why the best way to tune is by knowledge, on the street, with a driver who covers all the types of car usage (roll ons, hard acceleration, mild acceleration, shifts, etc). A dyno can be helpful to allow you to identify where in the area of 12-13 afr your engine makes peak power, but then you need to try and tune the car to make those afr's and so forth. I can tell you from experience tuning a car that even something as simple as a different gear will actually cause the way the engine is loaded to result in different afr's. That is a nuance you probably won't see on most dyno tunes and so forth.
So yeah... dynos are good for benchmarking where you are, and finding out how your modifications are helping you along, and for getting a general idea of how two things may compare. But they certainly are not the bible for how a car performs. And for the record. 1/4 mile times are even worse for judging car performance. There is a reason one guy can have a 2 second 60' and another guy have a 3 or 4 second... in the same car.
holy heck that's a thread transition!!!!
I have no idea. Typically you want to alternate sides and angles. and progressively add to the spec you torque to until you hit the recommended. But other than that I got nothing!
Please post a seperate thread or do some searching... this is a hell of a thread jack and is typically frowned on a bit.
I have no idea. Typically you want to alternate sides and angles. and progressively add to the spec you torque to until you hit the recommended. But other than that I got nothing!
Please post a seperate thread or do some searching... this is a hell of a thread jack and is typically frowned on a bit.
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Jun 6, 2015 08:50 AM