s5 n/a vs Renesis vs NSX volumetric efficiency
 

[QUOTE=arghx7;4036048]I thought you guys might find this interesting. Here is a comparison of volumetric efficiency vs rpm from a number of different engines. The graphs came from the manufacturer's papers released on the respective engines.

http://www.rx8club.com/attachment.ph...1&d=1311213678

The hashed pink line is the s5 n/a engine. Black line is the 6 port Renesis, and the Gray line is the 4 port Renesis. In the US the 4 ports were found on automatic-equipped engines for the first few model years. Those 4 ports were not like the 4 port engines on the previous turbo motors. The ports were very small--think 6 port engine but with only 4 ports. The increases in VE from the s5 6 port to the Renesis 6 port can be attributed to a few things.

1) much larger intake ports with significant changes in timing
2) a more sophisticated intake staging system. the secondary ports are staged by rpm instead of by throttle position like on the s5
3) a variable length intake pipe in addition to the VDI system we know from the s5

Now here is the volumetric efficiency curve of the original NSX with the C30A engine:

http://www.rx8club.com/attachment.ph...1&d=1311213678

The thicker line is the production NSX engine. The other line is a prototype, basically an NSX engine without VTEC which was used as a benchmark. The production NSX engine has VTEC to increase lift and duration by a fixed amount at the switchover point. This can be compared to the auxiliary ports opening on a rotary. The NSX also has a variable intake system roughly equivalent to the VDI system. The GS-R and Type R Integras also had both systems. Nowadays this technology is pretty ho-hum but at the time it was pretty sweet.

Amazing to see what 20 years of R&D can do... now if only the rotary came out the same time that the piston engine did, then how far along would we be?

if mazda can keep the dream alive, maybe it will be the engine of the future :)

cool info

[QUOTE=arghx;10713561]honda really knows how to make a good cylinder head/port!

mazda is good at weird things, cause they have done the rotary...

from http://www.mazda.com/mazdaspirit/sky...kyactiv-g.html

"In order to lower the temperature at compression TDC, reducing the amount of hot exhaust gas remaining inside the combustion chamber is effective.... ...Therefore, it can be easily inferred that the amount of residual gas has an major impact on knocking."

"internal EGR" has been in all the Rotary SAE papers and things for decades ...

something new to learn everyday.,.,.

It's impressive to see N/A engines getting over 100% volumetric efficiency!

this is bs you cant git over 100% ve without forced injection.

yes you can; by tuning the length of the intake runners so that you get a standing pressure (sound) wave in the intake system at a certain RPM, you can design it so that right before the valve closes (or port is blocked), the standing wave right at the intake port is at a higher pressure than the average ambient pressure, thus forcing more air into the engine than you could get otherwise. This is all a combo of valve/port timing, runner length, diameter & design, and using the pressure waves generated by other cylinders/rotors.

Basically its how you tune an NA engine to make power at a certain engine speed, and is a large part of the reason why an engine (that doesn't have VVA & a variable-length or valved intake system) can be so peaky; making lots of power at high revs but nothing at low revs. In fact, this is the origin of the word "Tune" with respect to engines; since the pressure wave dynamics in the intake is basically playing with the sound made by a combination of open & closed pipes (think a pipe organ), engines were "tuned" in the same way that a flute, pipe organ, horn etc were. Things have gotten a bit more sophisticated since then, but the basic premise is still the same.

Also, check your facts before calling BS

owned

Similar and opposite. Except we would all be on www.rpx7club.com (reciprocating piston experiment 7) and we would be saying that we like them because they are unique and would have been the choice if the same R&D was put them.

yeah well... just look at how amazingly the RX8 did and that was pushing the limits with current technology.

unfortunately to get real power it would need bigger displacement and the 16X now has nothing to go into.

Sure you can. The problem however is that volumetric efficiency isn't the only thing that matters. We also have mechanical efficiency and thermal efficiency as well. Don't forget how displacement factors into it.

BTW: It's forced INDUCTION not forced injection. I guess in a sense all fuel injection is forced since it is pumped through injectors. Carbs however only use the pump to send fuel to the bowl. It is through the suction created in the venturi that pulls fuel into the engine rather than forces it. You can do lots more to effect VE through intake manifold design with a fuel injected car so in a sense according to strictly what you said, rather than what you actually meant, the statement could be considered true.

i like how the rotary overlay puts the difference between old 6-port and new 6-port into perspective. that's pretty cool.

Honda, in my opinion, has always been ahead of it's time and regardless of all those who now HATE them so much, they make great cars and they should keep us ALL awake at night.

Another cool comparison; we ran our top mount turbo rx-8 turbo system with the 6 ports wired open, and closed( 4 port). As you can see very late intake closing hurts power below 6700rpms, but after that takes off like a rocket. Even under positive pressure well above 100% VE, port timing plays a big role in your powerband...

>_< Why do people keep saying that? Of course we have no idea what it will go into yet.. It doesn't even imply that it doesn't have a chassis..
</end off topic>

I was talking to Rob@Pineapple a couple weeks ago and he mentioned that the VDI effect [I think he said on S5 NA intake, but it might've been for RX-8s] can generate up to 0.75 PSI of positive pressure. Sounds pretty awesome to me!

More interesting things to consider...

Here's info on the Nissan VK50VE engine found in the FX50 crossover. Just like the VQ37VHR engine in the 370Z, it uses continuously variable cam timing for both intake and exhaust as well as continuously variable cam lift & duration.

https://www.rx7club.com/attachment.p...1&d=1321716433

blue line is the VE curve for the production VK50VE engine, using a tubular-style dual manifold for each bank. Yellow line is the VE curve for a prototype engine using log-style exhaust manifolds while also having no variable cam timing on the exhaust cam.

https://www.rx7club.com/attachment.p...1&d=1321716433

The Nissan continuously variable lift system, similar to BMW Valvetronic and Toyota Valvematic in what it accomplishes, can basically turn a cam from a 100 degree duration all the way to a 292 by changing the lift and duration profile at the same time:

https://www.rx7club.com/attachment.p...1&d=1321718212

Here's a little video of someone messing around with the VEL system on a 370Z engine

http://www.youtube.com/watch?v=a8P2V...layer_embedded


Getting back to rotaries... here is the VE curve of the NSU KKM 502 engine used in the Wankel Spyder, the first production rotary engine ever built. This engine had a single rotor with peripheral intake and exhaust ports. The carb was bolted directly to the intake port due to packaging constraints of the rear-engine configuration.

https://www.rx7club.com/attachment.p...1&d=1321716433

Here are some experiments Mazda performed when developing the 6 port system for the GSL-SE series 3 1st gen Rx-7. Note that little "l" is runner length after the plenum, big L is runner length upstream of the plenum.

Here is the "short style" prototype which has very little runner length and no plenum, like you'd expect from a carb type of setup:

https://www.rx7club.com/attachment.p...1&d=1321717036

Mazda played around with the intake port closing timing to see how that affected the VE curves with this short manifold setup:

https://www.rx7club.com/attachment.p...1&d=1321717036

Now here's another setup they did. This one used the more conventional 6 port intake system we are used to for the series 3 and series 4 engines. Mazda created a prototype manifold with a separator to see how the pulsation effects from the two rotors affected volumetric efficiency:

https://www.rx7club.com/attachment.p...1&d=1321717036

Here are the results (look at the "measured" lines) showing the change in VE from having the separator, which stops pulsation/interference from the two rotors, and from having no separator with a 2L plenum:

https://www.rx7club.com/attachment.p...1&d=1321717036

Here is the effect of different intake port closing timings on the volumetric efficiency for the engine with no separator (just like the production s3 and s4 n/a engines)

https://www.rx7club.com/attachment.p...1&d=1321717036

and here is a graph showing manifold pressure in the secondary port runners with intake port closing timing at 70degrees ABDC and runner length (downstream of plenum) 500mm. This is on an engine without a separator:

https://www.rx7club.com/attachment.p...1&d=1321717036

The whole point of all these numbers and charts and graphs is to figure out what are good port timings (intake close) and downstream runner length (little "l") and upstream runner length ("L"). There were some other calculations done for plenum volume as well.

-- On the series 3 and series 4, you had fixed "l" downstream runners, fixed "L" upstream runners, and variable intake port closing timing at full throttle through the use of the auxiliary ports.

-- On series 5 you had variable "l" downstream runners, fixed "L" upstream runners, and variable intake port closing timing. Series 5 and later used less plenum volume because it dampens the pulsation effects at high rpm.

-- On the 6 port Renesis you had variable "l" downstream runners, variable "L" upstream runners, and variable intake port closing timing.

This is all really cool stuff, but what is the relationship between volumetric efficiency and HP?

Or maybe a better question is, why is higher volumetric efficiency better? Other than it just being "more efficient", more efficient at what?

Volumetric efficiency tells you how well the engine is working as an air pump under given conditions. The better it can pump air, the more output it can generate with all other things held equal. Usually volumetric efficiency is going to be the % of air pumped into the cylinder compared to its theoretical maximum under some standardized conditions.

The whole point of porting a rotary engine, or changing out the cams on a piston engine, is to change the volumetric efficiency curve to make it pump air more efficiently in a certain range of operation. This normally leads to compromises: in the case of the rotary, late intake port closing will increase the pumping efficiency at high rpm and reduce it at low rpm. That's why the aux port system came about--it allowed multiple port timings suited to different speed ranges.

Volumetric efficiency is a bit sketchy term:) Technically, you can´t have more volume in cylinder than swept volume+clearance volume. Volume is always same. So we should rather talk about mass-metric efficiency or about ratio between air density in cylinder/air density in intake manifold.

Engine´s with high VE not only have high mass flow which on its own is basis for power, but due to lower pumping losses and lower internal EGR level, they have lower BSFC during this specific condition and hence are more efficient.

To the people who think that forced induction is increasing VE% - it doesn´t. Its increasing air density... Forced induction "can" change VE, but it works both ways - during favorable conditions like intake pressure higher than exhaust pressure its higher and vica versa. As always, its about making everything work as package:icon_tup:

the terms get thrown around a lot and they can be confusing