WackyRotary

where the heck did that come from? No, actually holley and holley regulator.

Your right about dyno proofing. I have had access to a chassis dyno, eddy current dyno, and engine stand dyno back in the day when I was in college. However, small changes like a fan and a electric fan show VERY little in the difference department. Ofcourse a true test with a engine stand dyno would be the best test.

Actually, you don't even need to bother dyno'ing it to get your proof. Unless your measuring the difference in interia improvement with the fan/fan clutch off, the 1/4mile will ofcourse improve.....ever so slightly.

You could run a electric motor with the stock fan/fan clutch attached and measure what horsepower is needed to turn it by measuring the current draw of the motor with amp meter in line and adjust motor rpm by using a potenimeter(spelling). This is how they determine friction hp on a engine by spining it with a huge power electric motor with no fuel/ignition with the throttles fully open and see what the hp draw is to spin it, you'll find it is a linear relationship with rpm.

Anyway, typically the big industrial fans use 1/4hp-1/2hp motor range and they blow as much if not more then a black majic fan's cfm in some cases. If you ever stand infront of one, YOU KNOW they are pulling more CFM then the stock fans with the engine at 4000rpm+.
So one gets the impression, a stock fan CAN'T take much HP to spin. Well if you do the math, you'll find that 1hp=746watts. So a 1/4hp motor is =187watts...and a 1/2hp motor = 373watts.

So a typical aftermarket 12v fan is usually 30amps at full blast, so you got 360watts or .48hp. Thats why you'll have a hard time convincing anyone a mustang fan draws 45hp. A fan that robs 45hp on a chassis water brake dyno test(that measures torque@steady rpm, NOT A interia dyno(which measures time to accerate the rollers), would put out a amasing amount of CFM.

Oh, and electric 45hp fan would put out a amasing amount of CFM and would be 33570watts.

mar3

iTrader: (8)

The Carter fuel pump thing is a running joke with me and every time I see a reference to it being used. Sorry for the cheap shot, it was late...hell, it's later now...I'm glad this shift is for only one week...

nopistonsforjoe

how does the victoria british fan compare to the black magic? is it really worth the extra hundred bucks?

mperformance

Damn it I got a Carter too....I love it!!!
HAHahhahaha

BTW electric fans suck!!! I will be reinstalling my trustworthy mechanical fan again...only that I'll keep the electric just in case by the condenser.

SilverRocket

"Wise man 1"? You're the smart guy who insists on persisting to argue a point which is absolutely incorrect.

Read it and weep smart guy...

http://www.gruntled.com/Dellorto/Page2.JPG

Racing Beat dynoed my exact setup, and I do mean my *exact* setup, at 53.6 % more horsepower than stock at 7k rpm. Assume a 100hp stock engine and that's 153.6 hp. Add my 10hp electric fan, according to your vastly intelligent logic, and that's 163.6 horsepower.

Although oops, maybe I better subtract some horsepower for my shitty Carter fuel pump eh? How much would you say Mar3, around 10hp or so? You seem to be very good at guessing. I remember reading one time that a Corvette had a Carter fuel pump and it resulted in a 500 hp loss. Guess I should make an arbitrary guess based on nothing to do with RX-7s and make up some number to apply to my situation. Yeah, nothing like some sound logic.

Look I know that there are little differences from one motor to another, and RB might be a little optistimic, so I'm being conservative and saying I think I have around 150hp. I'm talking flywheel, not to the wheels. My acceleration times back this up.

Look man, it doesn't take a rocket scientist to tell if you've accomplished a 10hp increase. However, if your car feels no different, and your quartermile times are no different, you can say with a nice degree of certainty that the e-fan didn't do ****! Which it didn't

mar3

iTrader: (8)

You have to dyno your car. What someone else did don't count. No dyno time, I suspect... Even the IROC cars that are assembled by the same guys using identical templates and parts for all 30 or so engines say that there are variances up to plus or minus 10 HP (wow, where did that come from??) amongst the engines even though, technically, they're all the same. (Why are some ant piles more fun to kick than others?) hehehehe....

SilverRocket

Broke students can't afford dyno time for no good reason other than just to "know". But don't worry, when I can, I'll let you know about my 150hp to the flywheel Good point about the dyno, and I agree with you that I can't assume I have any exact amount of horsepower just because someone else built a similar engine and it tested at that level. There are certainly variances. But I think I can be fairly confident to say I'm within the neighborhood I think I am, given all the evidence I have in support of that. And also, I have to justify my purchases

And I'm still right that electric fans don't do ****

CrazyJoe12a

Yeah, but the mech. fans sound like air raid sirens

I got rid of mine just for that

mar3

iTrader: (8)

And gained 35 HP to boot...damn, ya can't beat that!!

RICE RACING

This may not be the most scientific test for this thread, but when I ran a mechanical/hydraulic fan the loss of power when the fan engadged was VERY noticable...

Usually the fan would come on up a hill during a long incline (high water temp) causing the fan to "start" upon starting there is a very noticable drop in engine power! When maintaining a constant speed up a hill, as soon as the fan engadges it would wipe of 5 kph of the steady state speed.

Different application to a rotary but same size fan with similar cooling capacity.

I estimate the loss of power to be in the region of 10bhp at least between the fan working and free spining.

RXcetera

What a stupid thread. If I cant notice a difference with the fan on or off and my times on a drag strip arent affected, then who cares about dynoing the car?? Mar3, I love how you assume you know better because of your little G-tech numbers... where are YOUR dyno #'s with this 10hp gain??

And comparing some 5.0 test to a RX-7? Wtf is that? Stupid.

Acuspeed

Before this gets out of hand, I just want to say ...

everyone relax a bit. It's just an online car forum, it's not life or death ...

Thanks

SilverRocket

We're all cool, we're just playin

mar3

iTrader: (8)

Another interesting ant-pile. I didn't assume anything. Based on a percentage of HP lost from a well-documented and published dyno run, I speculated that a similar percentage should be lost for any internal combustion engine. It's all the same air, same burning and same parasitic drag and friction loss, anyhow. That's why the rotary is such a gas pig even though it's only got 3 moving parts associated with mechanical transfer of power from chemical combustion. And, guess what, hot dawg? My G-Tech meter said I had 135 HP when I did a run in the local community college parking lot on a nice Sunday. A dyno run a year later showed 113 HP at the rear wheels. How much is lost in a manual tranny? Do the math and save up for a G-Tech, it is a worthwhile little toy...

RXcetera

Who here truly beleives that it takes 45hp to spin a fan on an engine?! Do you realize how much power 45hp is? Honestly, I wouldnt be suprised if the fan on an RX-7 takes LESS than a hp to spin to 3000rpm. Yeah, that's my opinion, but it's an opinion founded on logic and experience (10 yrs on RX-7's).

BTW, I have pretty much the exact same car as Silverrocket with the exception of a Dual RB exhaust (he has the full short primary setup), I have smaller diameter wheels and tires and... or yeah, he runs the BLACK MAGIC fan while I have the stock mechanical one. Back to back drags showed that my car has the jump on his until about 70mph and then he slowly catches up and passes. Durring our testing, I pulled my fan off and continued dragging. The result? Nothing. It did absolutely nothing and the results stayed the same. This is one example, but there are many others. I'm all for electric fans, they're a better option in my opinion... but the day I blame a loss to someone on their electric fan and their "10 hp" advantage is the day I retire from RX-7's.

maxcooper

Here is a link you guys might enjoy reading...
http://www.carnut.com/ramblin/_dyno.html

On my T2, the fan used to noticably slow the car off the line sometimes. I think it was the clutch getting stuck or something (and thus not representative of a properly-functioning unit), but it did take a lot of power.

-Max

mar3

iTrader: (8)

Now that's two scientific dyno studies. Apparently, it's time for you to hang up the keys. I guess I know a little more than you thought. I'm not Rotary-centric. I'm a gearhead and I've been doing the gear-head thing for 22 years now. You tend to hear it all and see the truth of things given that kind of time span. Sure, a 12A won't lose 45 HP trying to turn its mechanical fan, but did you note the 8% loss figure at 4500 rpm in the dyno run given on that 350. If they had told me their 350 was cranking out 358 HP, I would've speculated they were losing 36 HP (358 X .10= 35.8= 36...so you understand where I "guessed" that number from...) to the fan. They lost 40, so I was on the conservative side. Again, I'm supported by science and you are just babbling, interesting ant pile no.2... WTYM...

Jason Guthrie

quote:
--------------------------------------------------------------------------------
When somthing requires electricity from the alternator, it puts more drag on the engine.
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Well... yes it is. It has been thoroughly discussed in the miata boards by engineers(some students) about how ANY electrical use/load uses power which ultimately comes from one source, your engine. There are dynos of cars with stereo systems that steal 1-2+hp. You may not notice it on an explorer, but it is there. I never notice it on my miata but I have the AC button to **** me off. Now that takes noticeable power away. It has been said to be 10-15hp on the miata. Bottom line, it always comes back to basic physics. Nothing is free.

Manntis

turning an AC compressor pumps a gaseous refrigerant, therefore greater drag.

An alternator saps virtually the same amount of engine power via the belt whether it's a high or low draw - the armature is spinning in magnets to generate the power.

It's true that nothing is free. You must run the engine in order to create the mechanical motion to generate the electricity. However an alternator, like the horsepower of your engine, is rarely operating at peak output. Causing a greater draw on the alternator simply wears it out much faster.

mar3

iTrader: (8)

If you read the link on the 350 dyno session, you'll see they did the alternator thing and found a "measly 1.28 HP loss" from a big juice alternator pumping out 65 amperes! Clearly, the electric fan is the way to go...

Manntis

I can see the logic of HP loss from a mech fan vs. electric though.

A mech fan has to push the blades through the air, causing a drag on the pump or similar drive component in addition to all the other resistance on that component.

An electric fan takes advantage of the high torque characteristics of an electric motor and draws on surplus power from the amp not required by the battery or other systems, therefore it's virtually free power. Virtually.

If the Mustang's fan saps 35-45hp it's grossly underengineered, but then this is a 2002 'muscle car' that still uses live axle, pushrods, and skateboard steering.

Best thing to do is perform the mods you think work for your car be they exhaust, electric fan, or those 'go faster' 300 lb fibreglass body kits and be happy with it.

fter all, those soccer moms in Sport Futility Vehicles think I'm an idiot for driving a teeny tiny two-seater, mods or no mods, when in their eyes their vehicle is just so superior.

SilverRocket

Mar3,

You can argue all you want, but you're still wrong. Theory is theory, but it doesn't mean **** when things are proven in practice. Rxcetera, myself, and countless others have proven in practice that electric fans do not add significant levels of horsepower. You, on the other hand, continue to obstinately argue your theory, based on nothing but speculation adapted from something you read about a completely different car. You've never done any dyno runs to support your opinion, an opinion that flies in the face of the vast majority of RX-7 owners' experiences. Not only that, but you're insulting us as if we're any less "gearheads" than you are. If you pulled your head out from where it is right now, you might notice that you're actually achieving quite the opposite of your intentions.

Unfortunately the same goes for all you guys that are speculating things about mechanical fans and their potential additions to parasitic horsepower loss. I don't care about theoretical possibilities in generality; the question here is whether or not electric fans free up noticeable horsepower or not *ON FIRST GENERATION RX'7s*. The answer is no, they don't. I challenge any one of you to try removing your fan and going for a drive - you'll find, just as those of us who *have actually done this test and aren't just pulling ideas out our asses* have found, that it makes no discernable difference at all. I'd love to say it did, because I dropped $400 on an electric fan, but nope, it sure doesn't.

I'm finished with this thread; it's not an argument anymore when certain stubborn people throw logic out the window. I feel like I'm explaining things to a pre-schooler, who just doesn't get it even he's told 10 times over and over again. So you go on thinking what you think, it won't change the fact that you're wrong

mar3

iTrader: (8)

I'm not...I speculated 10 HP and I guess I'm going to have to get on a dyno to show you that you couldn't tell 10 HP from 2 HP from your ill-padded butt dyno...I never said you'd drop a second from your quarter mile times and the 45 HP loss was from a healthy 5.0 cranking out in excess of 440 HP. I never said the 45 HP was to be experienced from a rex. Just like most mods, the increases to be seen are in percentages of what the engines potential is. The potential is a function of how much air and fuel that engine can usefully ingest. It's not the same for a 1.1 L 12A and a 400cid Pontiac. So gains and losses can reasonably be speculated by sliding variables based on displacement and rpm and levels of modifications. The fact that I could come so close to the 350 dyno numbers bears this out. When I do the dyno run on this '84 GS (or is it '84 GSD??), that will bear me out as well. Remember, there was a time when the whole world was proclaimed flat by the community and they also believed they were right...preschooler, indeed...make your cheap shots at least on an intellectual plane if you want to impart a lasting shot...

What kind of playin' is this, anyhoos? You raisin' any kids to think this is socially acceptable playing?

SilverRocket

Nope, guess not, since the results you came to were wrong

I really still believe that you're over-thinking this; seriously, try it and you'll see. If you've actually gone to an electric fan as you say, I just don't understand why you think you gained 10hp. If so you've imagined it Do you really believe this, or are you just having fun arguing a point?

This is the kinda playin' I do since I just started a new job that begins at 6am every morning... I be a tired, cranky rotorhead by the time evening rolls around Every night I come home and good ol' Mar has something new for me... lol. And naw, no kids, I'm still a kid myself

RXcetera

I think that's why Mar3 does it too . That must be why this "22 years of experience" gearhead was pming little old me for advice at one point .

Silver, you raise a good point about theory vs practice. It's interesting that science has become so important to our society that real world results dont really matter anymore. It's as if what makes sense on paper MUST make sense in the real world. It's been proven time and time again that going to an electric fan DOESNT increase acceleration on a 1st gen RX-7... isnt that all that matters?? What's the point of arguing this with theories if in the real world they dont hold true?

I often think that way about 1st gen RX-7's. On paper, they dont amount to much, but once you actually drive one...

BTW, are you meeting up with us after Indy tomorrow?