20B FD Qs

[Spartacus]

True true he is mental I would have given up on Rx7s years ago with the luck he has had, I need rub some of my car luck onto him, then all you V8 guys can be as quick as me lol :rollin

But isn\'t there a problem with your car?:wiggle

[BlitzBoy]

Nope no problem with my car runs like a swiss watch, but if I want to run quicker then 10.46 I need to run more boost therefore I need a better clutch.

I can still go out and run mid to high 10s now with my current setup, but where is the fun in that? bored now and want to run quicker, so a better clutch is currently on its way so I can increase the boost

[Spartacus]

Nope no problem with my car runs like a swiss watch, but if I want to run quicker then 10.46 I need to run more boost therefore I need a better clutch.

I can still go out and run mid to high 10s now with my current setup, but where is the fun in that? bored now and want to run quicker, so a better clutch is currently on its way so I can increase the boost

Fair enough, out of interest how does the gearbox and diff cope?

[BlitzBoy]

The gearbox has been fine has not been touched, I run a Mazaspeed Powerplant frame to cope with the increased power, solid engine mounts,I run a Kaaz 1.5 way diff for the last 3 years with a diff brace, not really rocket science to get reliable in the drivetrain stakes, hopefully if I do crack 9s it be interesting to see how long the stock box will last.

[Kash_]

Here you go 2-rotor vs Ls1 V8 RX7 - both have roughly the same power...

[Kash_]

Also a rotary engine has less moving parts than a piston engine which means less friction, which mean less transmission loss and means quicker acceleration.....

Torque isn\'t everything it just gets you moving it\'s HP that builds up speed :Thumbsup!

[Spartacus]

Also a rotary engine has less moving parts than a piston engine which means less friction, which mean less transmission loss and means quicker acceleration.....

Torque isn\'t everything it just gets you moving it\'s HP that builds up speed :Thumbsup!

mmmm no details of power, weight, tyres etc etc in that race though?

Also where are your facts re less friction? Wouldn’t it depend on the size of the moving parts and the amount of friction for each of them? Any facts on this?

I thought transmission losses were gearbox and diff etc, as when you say that a 20b with 500rwhp would be quicker than a V8 with 500rwhp does that not negate any transmission losses as they have both been measured at the rear wheels?

Now I would have thought that torque would have been quite important in drag racing as if what you say is correct that "torque is what gets you moving", isn’t that the idea?

I\'m happy to consider hard facts rather than wishful thinking:cheers

[Kash_]

Wikipedia

All such engines have the potential to improve on the piston engine in the areas of:

Higher power-to-weight ratios.
Mechanical simplicity.
Less vibration.
Sealing system has no revolutions-limit; piston rings fail after the engine\'s revolutions-limit.
While typically larger than the piston of an engine of corresponding capacity, a rotor may perform many strokes per revolution. The ....el produces twelve strokes per revolution of the rotor (four strokes per chamber times three chambers) (although the spindle rotates three times faster than the rotor or three times over the twelve strokes), as opposed to two strokes for each crankshaft rotation of a single-cylinder single acting piston engine.

[Rzla]

You don\'t state the fact that at TOTB the v8 rx7 had significantly more power than the other rx7s there though do you? How much was the v8 running? 550 or 600? Or more?
 
Talking about circuit racing is ridiculous. There are so many factors to take into consideration so it is not a fair comparison of which car is quicker. Straight line is a better indication of which car is quicker.
 
How much power was Craig running at time attack? And whifbitzs time attack rx7 more often than not was quicker than the v8. Whifbitz was running 1.3 most of the time... if he unleased 1.6 bar he had game over, not to mention he never used race fuel. Pump fuel FTW and he was still quicker.
 
Anything to manipulate the situation to try and convince rotary owners that a v8 conversion is better!
Pistons are for.... you know how the saying goes

[Kash_]

In the video both cars were using slicks, similar weight and V8 had NOS and a bit more power and definately more torque...

It\'s not wishful thinking more like using basic logic.... if there are more moving parts i.e. piston engine there will be more friction :Thumbs-up

http://www.drivingsports.com/site/2008/12/rotary-vs-piston-engine-equivalency/

A piston engine has to reciprocate, involving wholesale changes of direction and lots of surface area friction, and there is a quite involved valvetrain mechanism to operateâ€"meaning there are hundreds of parts dancing in synchronicity just to make the thing work. Two steps forward, one step back. Volumetrically, however, rotary engines are superstars. Without a valvetrain in the way and while breathing through relatively large ports, rotaries tend to better fill their chambers and thus realize a higher proportion of theoretical capacity. So, while being less efficient per unit of fuel consumed, rotaries generally compensate for it by moving more air/fuel per unit of rated capacity. Another area of consideration is that this good breathing is advantageously used at higher RPMs to yield high horsepower without necessarily high peak torque, so a rotary engine’s torque has a longer lever, so to speak (i.e. mechanical advantage of RPM). This good breathing also takes place over a relatively wide RPM range, so the torque tends to be very linear, which certainly helps drivability.

[Kash_]

Torque vs Horsepower :driving

http://ezinearticles.com

You\'ve probably heard various racers and engine builders/tuners talk about torque vs HP. Some say "torque is what moves the car", others say HP is all that matters. Well, you\'ll have to put me in the latter camp, because HP is the most important. Torque is how much twisting force you are putting on the drive shaft, typically measured in ft lbs. Horsepower is multiplying this twisting force by RPM (how fast you can keep applying this force).

If we didn\'t have gears, than torque would be more important. That\'s because in any 1 gear, the torque peak is where the car accelerates the quickest, producing the highest Gs. The torque peak can be important for launching the line, but after that HP is all that matters.

To summarize, it is HP through the correct gear ratio which produces best performance. If you are building an engine, you want the highest average HP through the RPM range you will be using.

[od404]

In the video both cars were using slicks, similar weight and V8 had NOS and a bit more power and definately more torque...

It\'s not wishful thinking more like using basic logic.... if there are more moving parts i.e. piston engine there will be more friction :Thumbs-up

http://www.drivingsports.com/site/2008/12/rotary-vs-piston-engine-equivalency/

Unfortunately where lubricated surface are concerned, basic logic doesn\'t necessarily apply.  Friction in dry contact is very dependent on the surface areas and contact forces involved (lots of lightly loaded parts can produce less friction than one highly loaded part for example).  When considering lubricated joints even more complexity is added as you start to introduce oil film thickness which has massive effect on your friction.

It is also almost impossible to measure the total friction within an engine so the whole rotary has less friction than a piston engine argument is pretty mute in my eyes.

Rotary 1 - 1 Piston

Volumetrically the rotary is far superior to the piston engine as it is a lot more free flowing, this means that your pumping losses during one engine cycle are less (ie less work/power required to pull/push air in and out of the engine).  

Rotary 2 - 1 Piston :Thumbs-up  

However, we need to remember that due to the shape of the rotary\'s combustion chamber, it loses a lot of heat energy during combustion, this reduces the thermal efficiency of the combustion process.  The result of this is less work/power done by the air/fuel mixture than the same mixture in a piston engine.

Rotary 2 - 2 Piston

In my eyes piston and rotary engine are pretty even from a fundamentals point of view.  The rotary has some great points going for it and if it can overcome the fundamental thermal efficiency issues it has I feel it can become more successful as a consumer engine.  As it is, it would seem that only nutters like us know the joys of driving one :3gears-rh



And the on the whole torque vs power issue.  Consider Le Mans for the past 3 yrs where Audi/Peugeot have been running their diesel LMP1 cars under the same power and weight regs as the petrol cars, yet they have been winning quite convincingly....   Part of this is down to fuel efficiency, but if you watch them pulling out of Arnarge in 2nd gear you realise that the extra low down torque helps A LOT!  And basic physics tells us that power and torque are very closely linked so I feel dismissing one over the other is a bit silly as they are both as important as each other

[Nik da Greek]

^^^ sense at last!

Since, as has previously been pointed out, power is a product of torque (turning force) multiplied by revs...if your engine makes little in the way of torque to begin with, you then have to make it produce that lesser torque value more often to overcome the deficit. This means a high-revving lump with all the disadvantages that brings, such as increased heat, added mechanical strain, etc. Rotary engines suffer from high-rev issues less than piston ones due to their very nature, the lack of reciprocating mass to slow and stop every cycle, the less moving parts that can interace unpleasantly with each other if the timing\'s out, no valve springs to float or bounce, no valves or rods to stretch, etc, etc.


....but even rotaries have a rev limit, so it\'s not like you can just have tiny amounts of torque and make up for it by spinning to infinity (and beyond lol). Nothing works in isolation. Why can\'t we just accept that v8s and rotaries are both excellent power plants, and go about producing the same end result ( a stonking quick car!)in very different ways?

[antnicuk]

here here, more sense.....   ^^^^^^^^^^^^^

as for friction,  lol,  if you have a measured outcome ie 500 rwhp, then friction and transmission losses have already been taken out leaving 500 rwhp.

[Rzla]

For some reason when you get v8 rx7 owners they think their car is far superior as they have a v8 lump in it (not all but most) and they talk trash about the rotary (again some not all).
 
If the v8 was put in another car I could not care less, but one car it does not belong in is a rotary born car when so many piston guys trash talk the rotary engine.
 
Regardless of what you say the v8 guys came on here to gloat about the v8 being quicker at TOTB and indirectly rotary bash. They never specified the facts which i stated above.
550 at the wheels you said ant? If his car was not faster than the other rx7s I would burn it, because none of them were anywhere near that power at the wheels.
Let a rotary with similar power race him, lets see who wins.
 
Again the v8 does NOT belong in the 7. It is not called PX7, it is called Rx7 for a reason.