Jakor

+1

Efficiency. A 1.3l n/a rotary engine in a perfect world would make (numbers are not important) 500hp at 100% volumetric efficiency ("perfect world" not taking into account resonance/friction/heat/noise/etc.. think beginning physics as noone takes air friction into account when two objects are traveling at each other and collide. thus "perfect world") Now add rotor's spinning, there's 10% (50hp) add an intake another 20%(100hp) exhaust takes 20%(100hp) another 10%(50hp) for all the belts/fan/pumps off the crankshaft, then 10%(50hp) goes into creating all the heat/noise. Add it up, 500hp-50-100-100-50-50=150hp Now add 20%(30hp) drivetrain loss 120whp.

So in our "imperfect world" our engine makes 150hp and 120whp. Now if we go through and make improvements to the intake/exhaust and drop them from 20% to 15% loss, that's a 10%(50hp) overall gain or 200hp and 160whp. Now take the drag out of the drivetrain from 20% loss to 15%(30hp) 200hp and 170whp.

This is realistically how it works. My numbers and percentages are all off of course.

Think of it this way. If 1.29l (must have room for fuel in there too ) requires 0.01l of fuel in one cycle to remain stoich, how much energy (btu's) does 0.01l of fuel have? Multiply that number by 0.0003929 to convert to hp/hr's then determine the length of time it takes to make one rotation (based on rotation's per minute rpm). If you do all the math and unit conversions, you can find the max hp number for the engine at a certain rpm assuming 100% volumetric efficiency (which can go up or down) and an exact proper tune. Everything else is loss that you are recovering.

dj55b

iTrader: (2)

I'll dig out my dyno sheets for that one and prove you wrong. I did a test of stock vs Racing beat aluminum flywheel on my car just for curiousity sake and see if we actually would see anything and we did. From 2500-3000 rpm we saw a gain of 15ft-lb. And all the way through out we saw an average of about 2 whp gain. I had about 7 runs done before the flywheel. Last 2 being just to confirm the numbers, and then we did 3 after the flywheel was changed just to make sure it wasn't a fluke with the dyno. All 3 runs showed more power in the bottom end of about 15ft-lb and then about the same power gain all the way through out.

rnz520

iTrader: (10)

According to the laws of conservation of energy, Energy cannot be created or destroyed, on transformed from one to another. A lightweight flywheel will transform the energy needed to rotate the flywheel to energy used to turn the wheels, therefore increasing horsepower at the wheels.
The same can be said about all other "power increasing" mods, they take energy used to do something else and then transform it to do another job.
All a free flowing exhaust does it turn the energy used to push the gases out to energy used to move the flywheel, therefore the wheels; wrapping that exhaust in heat wrap will transform the heat energy that the exhaust would otherwise put out into energy used to move the flywheel, therefore, the wheels.
Therefore, a lighter flywheel will increase horsepower at the wheels by increasing drivetrain efficiency.

Black91n/a

A lightweight flywheel doesn't transform the energy, it just sucks up less than the heavier one.

Modifications to the intake, exhaust, porting, etc don't work like that. True they can reduce pumping losses, which will give an increase in performance, but they increase the volumetric efficiency of the engine, which pulls in more air, which requires more fuel, so you're making more power overall at the engine. A car with a properly designed header and exhaust system will provide more power than if you left it off alltogehter, by your theory that's impossible.

Jakor

I wasn't aware that backpressure was good for these cars. I have more power with my y-pipe/mufflers off. (hmm maybe it's the fact that the car is lighter...)

Well on second thought the exhaust *could* act kind of like the dynamic chamber causing vacuum to suck the air out. But then who makes a short runner exhaust? All you would need is to the length of the first or second pulse with a turndown...

Ok speaking of that, anyone have an exhaust that only runs just behind the "driver" for autox? SP requires at least that long of exhaust.

ultimatejay

iTrader: (1)

Impossible.Obviously you don't believe me, just read the quote directly from Mazdatrix that I put up. Do you think a well known rotary company would put up false info on their website that millions of people read?

rotorholic

iTrader: (53)

What makes Mazdatrix smarter than anybody else? There are many racers in here that are doing things that Mazdatrix or racing beat have never done before, there research was all done in the 70s and 80s.....Mazdatricx own dragcar bearly ran high 9s with a 3 rotor/supercharged+NOS full chassi racecar.

Black91n/a

You're misreading the Mazdatrix quote, and I'll say this, it's not very clear, not very well worded. A flywheel is an energy storage device, therefore it absorbs energy. The hevier and larger diameter it is, the more energy it'll absorb for a given amount of acceleration. With a lighter unit, it absorbs less energy, letting more get through to the wheels, giving more wheel horsepower under acceleration. I'm a mechanical engineer, you're obviously not, so how about you sit down and be quiet, because you're wrong.

dj55b

iTrader: (2)

I think you might of not read it properly.

"The actual horsepower of the engine does not change related to the weight of the flywheel. However, to increase the engine RPM, and accelerate the car, all rotating weight (as well as the entire car) must be speeded up. This requires power, and the heavier the part, the more power needed to speed it up. The less power needed to speed up the flywheel (and rotors, clutch, driveshaft, wheels, tires, car, etc.) the more power available to speed up everything else. The question we are asked frequently - "How much more horsepower will my engine have with a light flywheel" - is not the right question, because the answer is NONE. What you will have is more available horsepower to accelerate the car and yourself down the road."

It clearly says that it doesn't increase the horsepower of the engine, which we don't question, but then it does clearly says that more hp is available to accelerate the car (aka to the wheels) which is what a dyno reads. A dyno engine doesn't read the direct HP to the flywheel. Thats why there's Flywheel HP and Wheel HP which flywheel we all know is about 15% more HP. With your theory, it would mean that flywheel and wheel HP should be the same. When we remove weight from the drive terrain, the lower the loss to the wheels and hence more power to the wheels. I don't understand how you still argue. Have you done a comparison yourself? Because like I said I have myself!

ultimatejay

iTrader: (1)

Why don't you do a quick Google search on this subject and then come back here and tell me what you found.

It's a drivetrain component. You can't make more hosepower by lightening a drivetrain component. It allows the engine to work less which will accelerate the car faster. Here's simpler terms for you over achieving engineers. You take 100lbs out of your car. Does that make more hosepower? NO, does it make your car accelerate faster? YES. Why? Because your engine does not have to work as hard to move the excess weight. GET It?

Black91n/a

NO ONE is saying that it makes more power at the engine. All it does is not suck up as much power to accelerate as the stock flywheel, letting more through to the wheels, giving you more WHEEL horsepower, which is all that really matters in the end anyway. That's been said here time and time again, but either you're not listening, or you have a problem with reading comprehension.

dj55b

iTrader: (2)

I'm done trying to explain ... thats all I've been trying to say also which is why I highlighted those 2 quotes from Mazdatrix. I guess he can't read the lines and inbetween the lines.

TwoFun

it alway amazes me on how the torque curve keep climbing till 7500rpm, how do you do that?
typical torque curve peaked lower and around 5k-5.5k

farberio

iTrader: (7)

But that will not show up on a dyno. Think of it this way, the dyno gives you the maximum power the car has made.

We both agree that the 'raw' engine power does increase, thus, on a dyno you will never see an increase because it measures a power at a given RPM, not power over time.

Yes, you will have a faster car with a lightweight flywheel. Yes, more power is available on the ground. BUT, because the dyno is not a real world driving test and only a measure of engine power, you wont see the increase on the dyno...you just wont.

If, for example, (i think that if) you measured both cars in their actual times to accelerate you would see the same curve, just the one with the lightweight flywheel more scrunched up.

farberio

iTrader: (7)

And



For gto and his evil henchman

drewski86

I don't under stand why this is still being discussed. A chassis dyno does not measure engine power. Put a stock car that you know engine output of on a chassis dyno and see what makes at the wheels. There has been dyno proof posted and you still disagree. Here it is again incase you missed it.

http://g35driver.com/forums/1746676-post24.html

You don't see racers running light weight flywheels, aluminum(or fancier) drive shafts, low drag transmissions(with 1:1 top gear if you want to get deeper into it), etc. because it sounds cool on paper. Drivetrain loss is real.

rotarygod

iTrader: (1)

To whoever said it, backpressure is NEVER good for an engine. Ever!

A flywheel does not increase engine horsepower. We need to consider a flywheel as a part of the drivetrain and therefore factor in how much power it takes to move. We all know that you don't make the same power at the wheels as you do at the engine due to losses in the drivetrain. The flywheel is a part of this and factors in to some of that loss. A flywheel can never help you gain power. It can only help you consume power before it gets to the wheels.

Think about this. How much power is a drivetrain consuming? Is it 12% with a heavy flywheel? If we install a light one and now our drivetrain loss is only 10%, that's a gain at the wheels even though at the engine it stays the same. We reduced losses through the drivetrain through a loss in mass that needs to be moved. It's that simple.

Going back to the person who said a flywheel is like an exhaust or intake and that it can't free up any power, that's plain wrong. A different exhaust or intake can absolutely make more power through a change in VE. If you change VE, you are also changing the amount of air and fuel needed to make a certain level or power. Even if the statement was made from a conservation of energy standpoint that says you are only using the same amount of air and fuel regardless of power and that it's energy was only divided to different locations such as heat, pressure, power, etc..., even that is wrong as a change in VE changes that. A flywheel doesn't change VE. An exhaust or intake can.

rotarygod

iTrader: (1)

Not true. When measuring on a chassis dyno, all of your drivetrain losses affect the final result. Since the flywheel is a part of those flywheel losses, it shows up. It is calculating the time it takes to accelerate a known mass and displays it in reference to rpm or speed. If you have less drivetrain loss to overcome, it will accelerate the dyno faster which means more power at the wheels.

An engine dyno is a measure of engine power. A chassis dyno is a measure of the power that actually gets to the ground. There's a difference.

ultimatejay

iTrader: (1)

I guess there was a communication problem because I was talking engine dyno not chassis dyno. And even with a chassis dyno the number would probably not even register or would be very low. Once the weight of the stock flywheel starts to spin at a high rate of speed inertia takes over and the amount of horsepower vs a lightweight flywheel would be very minimal.

Jakor

Ask them about the toe steer bushings, they'll tell you you have to buy the whole carriage or their own eliminators. You *can* get the stock bushings by themselves if you really want them.

@rotarygod: backpressure closes exhaust valves on piston engines (ok, so I guess you can get some stronger exhaust valve springs I don't know much about them boingy things just the mazda that goes vrrrrrooooommmmmm ) It also is obviously required to spin a turbo =p

I thought my example was quite accurate at the top of this page talking about how most mods affect the efficiency and therefore power output of the engine but drivetrain mods affect the wheel horsepower. Weight is just the resistence of which the power is used to move, and affects neither engine or wheel horsepower.

Honestly this thread sounds as absurd as honda ricers thinking they'll beat you because they have a 1.6l or a 1.8l to your 1.3l... I guess some people will never learn.

slo

iTrader: (1)

216 WHP is really good, back in the 90's I went to a dyno day where there were several FD's and FC's. Most of the stock FD's made right around 215 WHP IIRC. To do that without any turbo's with what is in essence at least the same engine is an excellent feat.

dj55b

iTrader: (2)

Are you reading all the posts? did you see the g35 post of lightweight flywheel and clutch combo getting 13 whp and 17 ft-lb increase? Even in my session of the increase in power I would still had to retune my engine to make up for that. My engine builder told me that had I re-tuned my engine that day to compensate for the lighter weight i could of maybe seen about 8-10hp in the top end.

Trots*88TII-AE*

iTrader: (11)

Congrats on the accomplishment!

Now, last I checked, the only people who care what their engine puts out are V8 guys. The only power that matters is power to the wheels, everything else is bragging rights. Does a lighter flywheel increase power to the wheels? yes. Are there reasons to stick with a heavier flywheel? Yes, for certain purposes. This is like arguing that fat 19" wheels don't affect performance. Rotating weight = drivetrain loss = less useable power. I think that people are arguing about apples and pears here...

GtoRx7

iTrader: (5)

I accomplished it through a lot of testing with exhaust lengths and collector sizing mostly. And then even with pipe sizing after the collector. Everything on the car must match up pretty close, intake, exhaust, port style to get a desired result. The main most important factor is to CHANGE ONE THING AT A TIME! If I only listened to my advise years ago! Once your in the zone it will "come up on the pipe", and the engine sound is beautiful with a V-tec noise change the moment it occurs. Carlos Lopez used to tell me about how it would sound, and I never understood what he meant. I am glad I have friends like him to talk to. Guys like RotaryGod are very helpful as well. Be one with the sponge..... absorb everything and execute with a plan!

rotarygod

iTrader: (1)

Exhaust pressure does not close exhaust valves. If anything it would try to keep them open. Rising cylinder pressure from decreasing space can close them though.

Here's something to think about. It is in fact possible to have a turbo engine that has less exhaust pressure than intake pressure. It is not impossible so I'm going to also disagree that it is required to spin a turbo. It isn't. It's a side effect. Spinning a turbo doesn't revolve around backpressure. It's all about velocity. This is also why smaller exhausts make better low end power than larger ones. It's not the pressure. It's the velocity. Backpresure is bad. Velocity is good, to a point.