tooter 2.7 intake manifold spacer...

Except that people have done back to back dyno runs with different weight wheel/tire combinations and have found significantly lower results with heavier tires. The dyno doesn't care about the front tires, the effect isn't cut in half.

http://www.luxury4play.com/lamborgh...ects-wheel-tire-weights-wheel-horsepower.html

Green = 60lb wheel/tire pair
Blue = 68lb
Red = 72lb

 

Well, there ya go. My dyno guy was right. I tried my best to get it as nit-free as I could, wad. So go for it.

 

The effect of tire/wheel weight will be more or less pronounced depending on the acceleration speed on the dyno. If the dyno were to hold the speed in a locked position the weight would make no difference, allowing it to accelerate more rapidly would increase the effect. Tire diameter will make no difference on dyno numbers other than the weight acceleration factor. As for the 'half the tire not moving" theory that only applies to actual on the ground vehicle acceleration, on the dyno the wheel's entire weight is accelerating and therefor every pound counts. If one is to think of the lower half of the tire as not moving foreword then you must also consider that the top half of the wheel is moving foreword twice as fast as the car....in the end I think it all washes out as being the entire wheel's weight accelerating; not factoring in tire slip.

Unless you meant only half of the wheels meaning because the front two are motionless, then of course yes.

All that crap asside....I believe tooter's goal with this is part throttle efficiency/performance and therefor the full throttle dyno run is only able to verify if full power was affected across the curve and has nothing to do with his goal of increasing drivability. There was a tiny gain, and an assumed gain from the wheels, we could say he's probably about even. If the part throttle gained efficiency then that's what is important. It would have to be dynoed at normal driving acceleration loads before/after to see that. This is probably going to wind up being a product where the assometer is going to determine how good it is and it won't be a hot-rod product so much as a driving feel and possibly MPG thing. Lengthening intake, as well as exhaust runners, generally add low rpm and loose high. A perfectly tuned runner is only tuned for a narrow rpm window and anything outside is no longer in tune. Also, the more perfectly tuned that rpm window is, the more negative effect it'll have outside that window (ram effect). Like everything else with engines, there are compromises. Now that we have a variable cam, if one had a way to make his own variable intake and exhausts the package would really start to come together. Variable compression and connecting rod length might bring the piston engine to a whole new level of perfection.

 

Yes of course different wheel weight will adjust dyno numbers because lighter are easier to turn and frees up rotational mass.

Better point: why does this even matter. Tooters dynos were done with the same wheel tire combo.

 

I believe they were changed before the dyno test of the spacer and therefore the debate on the accuracy of the dyno info.

 

It had to due with tooter originally comparing a dyno run he did after many mods prior to the spacer with a dyno run he found of a pre-runner. He was making conclusions about the increases of his mods against a pre-runner that has much heavier wheels/tires than his aftermarket wheels/tires.

Never had anything to do with the latest dyno runs as already states a few times.

 

I guess I got lost. My understanding is that the wheels were changed between his previous run and the spacer run. If nothing but the spacer was changed why did you challenge his numbers for the spacer, or is it his header/intake numbers you were challenging?

If the wheels weren't changed in between then none of this matters and the spacer numbers stand undisputed.

 

My understanding is the current wheels were on for both runs.

Still not disputing the spacer numbers, as I say again.

It was comparing his dyno with his wheels to a pre-runner dyno run.

 

Ahh gotcha. It was the timing of seeing it with the spacer stuff and I thought the debate was over the tires altering the spacer numbers.

 

Exactly the same wheels and tires for both dyno runs.

The dyno guy gave me really good advice on what to expect from his many years of experience. He accurately predicted exactly what would happen.

 

So far there has been no debate or nitpicking, just a misunderstanding about the wheels.

So your dyno guy was wrong.

 

Ok.

 

So he predicted a newbie on the forum would potentially call someone out based on his own mistake and then get a 'beer cheers' from a veteran?!? Damn, he is scary good!

 

He was genuinely prophetic...

 

I never realized the HP and TQ curves never "swapped" at a given rpm on this motor

 

Very observant...

That's because the speed limiter cut off the engine at 4,800 rpms when we did 4th gear runs. The crossover point is at about 5,250 rpms. Here's a 3rd gear run we did to beat out the speed limiter. It shows the crossover...

 

Not observant enough apparently because I did not notice the RPM cut off on the dyno above lmao

 

It's easy to do. I don't pay any attention to the top of the charts either because with our engines there's nothing going on over 4,700 rpm.