Temps from vehicle to vehicle don't matter as long as they are consistent for the same vehicle from test to test.

 

unless he has aftermarket guages on both vehicles he will not know .
My experience suggests that temps are pretty stable in the 85-90C range until you do a few WOT runs back to back . That tends to take you up to 100C pretty quickly but 2-3 mins of cruising will stabalise it again.

 

pretty sweet and all, but if you really want to get this picky on stuff. Then technically aftermarket turbos don't do squat either. Without 30 or more identical dyno runs, who can be sure if you aren't just getting a fluke run?

Over 5% variation, perhaps, but who has launched a consecutive 30 run analysis to be sure?

Sweet

 

An important variable is start time. If 2 throttles are pushed by 2 separate people, 1 throttle will be pushed before the other. That car, given the rising nature of the rotary torque curve, will experience acceleration earlier than the second car. By the time the second car has started accelerating, the first car has begun climbing it's torque curve. Given 2 cars with identical torque curves and gearing, the car which hits the throttle first will out accelerate and out distance the second car. Mixing drivers and repeated runs, possibly with a slight disadvantage given to the modified car would minimize this.

 

indeed, this has been taken into account. Which was why we did repeated runs and switched cars. Hope to have some solid info for you guys next week.

 

Best bet is rolling start in third gear.

 

I like hands-on stuff, too.
But if the math doesn't align, I suspect the experiments were wrong, not the math (unless I did the math, in which case all bets are off since I can't count past ten without taking off my shoes).

If the math says A+B=C and the experiment comes out A+B=D, then there was probably something wrong with the way we measured A in the first place.

 

so - is that your hand in your avatar ?

 

Well whenever my scanguage 2 and AP pulley get here, I will see if there is any difference in numbers. I'm also using a G-Timer, which gives HP numbers in addition to 0-60 and 1/4 mile times.

But as for theory, underdriving the accessories would appear to logically give gains, like Brettus mentioned.

Enough people appear to have AP pulleys that you would think that if there was some kind of damage being done from underdriving that it would have surfaced by now.

Also one of the main points of the pulley was speed in which you could get to higher rpms and reducing parasitic drag.

However, the feeling of being able to rev the engine easier may only be a placebo effect and may not translate into significant HP gains. Another point, may be that the pulley is effective only under certain circumstances.

I would think pulley gains would show up a bit in 0-60 or 1/4 mile numbers, in passing "speed up" and "slow down" situation in traffic, or have some positive effects at sustained 100mph speeds.

An additional 5HP may not mean much in the 0-60 or 1/4 miles, since there are so many other factors to getting a good time. But, in certain situations, like you just slowed down because of a bike getting in your way and then you speed up to past some cars, the pulley's effect may show up. Or it could be a placebo type of an effect where "feel" of revving faster shows up and makes you think your faster.

Anyway the theory of how underdrive pulleys work seems pretty well established. I think how you attempt to say that they don't work on an RX-8 is to show that the accessories that are being underdriven are insignificant to the RX-8's overall performance.

If whatever is being underdriven has no effect on performance, can you then not say that a underdrive pulley does not work?

If whatever is being underdriven does effect performance, than can you not say that there would be some gain from an underdrive pulley?

Also, how would an underdrive pulley cause damage to the accessories that its underdriving? If it does...

 

g-tech really isn't the absolute best thing you could use either... I see what you are saying, however I think basing it off the g-tech will also just cause more arguments between all of us haha... Frankly, as you said there are way too many factors for the g-tech to be able to calculate such a minor gain. Maybe we'll see something however I remain suspect on those devices.

 

Underdrive pulleys are out there for any number of cars. They can be linked to decreased engine cooling and poor idle electrical performance in cases. These effects are more or less design parameters. Turn the alternator and water pump slower. An alternator raises it's resistance at low RPMs to increase it's amp output to match draw. At X% less than what should be idle speed in some cars, the alternator has difficulty running accessories. These are all drawbacks that can be identified in other cars. There isn't really the deep pool of experimentation to proove whether things like this may surface. All Rx-8's are not created equal. Joe Bob with his 32" sub running an underdrive pulley on a weak alternator will likely have issues. Maybe the alternator for the Rx-8 is perfectly happy at the decreased idle rpm. Have you ever heard of someone ruining an alternator by running too many amps through the stereo without using a capacitor?

While, in all likelihood, underdrive pulleys do increase available peak power, there can be definite drawbacks to them that give them a power at expense. I personally would favor lightweight, sexy pulleys that do not underdrive. Then again, I'd also like a waterpump that doesn't cavitate.

 

I'll say it again because it seems to be getting passed over with impunity -
An under-drive pulley really shines on a car with hydraulic power steering.
The RX-8 is not such an animal.
The PS pump is a huge drag (and one of the driving forces behind why Mazda chose electrical steering for this car in the battle to get the horsepower rating up).

 

UD pulley is a step towards performance and away from a cosmetic mod like a sub. Which is why I took my 500w 10w7 sub out the day I installed my pulley.

at idle I get 12.9 volts, exactly my battery output from my PC680.

While driving, it gets to be around 13.6 volts at around 3000rpms and stays there no matter how high I rev.

All this was measured on the NAV.

Either way, its not a problem, took the pulley on a 2200 miles roadtrip along with putting an additional 4K on it and havent had a problem.

I took out the underbattery tray when I installed my battery in the washer location, tested it on and off. No noticible gains in temp while at idle and crusing at various speeds.

One thing is that I notice cooling(water temps at 195-200ish) even when at 6K-7K rpms on the interstate. Even when I push the hell out of it, water and oil like to be at 200 each. At idle though temps do shoot up until the fans kick in. Which is where I think that removing the under battery tray does its best good, by allowing the whole engine to bask in the fans' goodness.

 

end rant......................

 

You think blowing hot air onto the engine is a good thing ?

 

hey, it's only 200 degree air.

 

I have the Ram Air duct sealed to my REVi, true cold-air.

I wouldn't recommend removing the underbattery tray if someone was using a short ram intake for just that reason.

 

what has the battery tray got to do with the ram air duct ?

 

Its wont blow hot air into the engine directly when at idle.

unless you think of course that the 200 degree temps of the air coming off the radiator will somehow increase the temps of the 1000+ degree engine.

either way, no battery under tray = good.

 

Yeah, removing the battery tray or airbox tray is a bad idea.

You want the air from the fans to blow toward the motor, not the hood, so that it goes around and out of the engine compartment.

 

but the hood is not vented, so it would still displace it out via the same route

 

After filling the compartment with 220 degree air.
You would be surprised how good the convection is under the hood with all of the OEM plastic in place.

 

your right about that one. I could probably cook hot pockets or something while I drive around.

 

I'm thinking the test didn't happen ?

 

rescheduled for sunday, we had massive rain here thursday and didn't want to test in a downpour ^^