Notices
Series I Tech Garage The place to discuss anything technical about the RX-8 that doesn't fit into any of the categories below.

Rx-8 vs NSX volumetric efficiency

Thread Tools
 
Rate Thread
 
Old Jul 20, 2011 | 09:09 PM
  #1  
arghx7's Avatar
Thread Starter
Registered
 
Joined: Apr 2005
Posts: 654
Likes: 4
Rx-8 vs NSX volumetric efficiency

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.



Black line is the 6 port Renesis, Gray line is the 4 port Renesis. The hashed pink line is presumably the 89-91 Rx-7 engine which is the logical benchmark for the Renesis. Note that the Rx-7 engine does have 6 ports and a VDI system. However it does not have a variable fresh air duct, and the secondary ports are mechanically staged by throttle position instead of by a computer controlled shutter valve. Now here is the volumetric efficiency curve of the original NSX with the C30A engine:



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 the Renesis. 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.
Attached Thumbnails Rx-8 vs NSX volumetric efficiency-rx8_ve.png   Rx-8 vs NSX volumetric efficiency-nsx_ve.png  

Last edited by arghx7; Jul 20, 2011 at 09:14 PM.
Reply
Old Jul 20, 2011 | 09:43 PM
  #2  
MazdaManiac's Avatar
Banned
iTrader: (3)
 
Joined: Oct 2003
Posts: 16,386
Likes: 27
From: Under my car
I find both of those charts to be highly optimistic and, being that they are manufacturer-provided, my pessimism is well founded.

I'm sure the line slopes are pretty accurate (though the Honda line is highly "optimized"), but I can tell you that from actual experience with both of these motors that neither ever actually achieves a functional Ve over 105%.
Reply
Old Jul 20, 2011 | 10:05 PM
  #3  
nycgps's Avatar
Out of NYC
iTrader: (1)
 
Joined: Jun 2005
Posts: 19,881
Likes: 36
From: Planet Earth
I thought the highest VE for Rotary (13B, at least) is around 85% ? Cuz the chamber is constantly moving away ?

the graph is showing like 105 ?
Reply
Old Jul 20, 2011 | 11:26 PM
  #4  
arghx7's Avatar
Thread Starter
Registered
 
Joined: Apr 2005
Posts: 654
Likes: 4
Originally Posted by MazdaManiac
I'm sure the line slopes are pretty accurate (though the Honda line is highly "optimized"), but I can tell you that from actual experience with both of these motors that neither ever actually achieves a functional Ve over 105%.
They are using different methods and equipment than you.
Reply
Old Jul 21, 2011 | 12:59 AM
  #5  
monchie's Avatar
I HATE SPEEDBUMPS!
 
Joined: Nov 2007
Posts: 8,549
Likes: 8
From: Las Vegas, NV
Interesting...
Reply
Old Jul 21, 2011 | 02:22 AM
  #6  
MazdaManiac's Avatar
Banned
iTrader: (3)
 
Joined: Oct 2003
Posts: 16,386
Likes: 27
From: Under my car
Originally Posted by arghx7
They are using different methods and equipment than you.
Different "methods and equipment"?
Ve is a simple thing - it is the ratio of actual air ingested to displacement.

I'm using the same "methods and equipment" as Mazda and Honda (only without the need for marketing hype).
Reply
Old Jul 21, 2011 | 10:06 AM
  #7  
arghx7's Avatar
Thread Starter
Registered
 
Joined: Apr 2005
Posts: 654
Likes: 4
pics of the engine dyno and research lab in your garage?
Reply
Old Jul 21, 2011 | 10:27 AM
  #8  
MazdaManiac's Avatar
Banned
iTrader: (3)
 
Joined: Oct 2003
Posts: 16,386
Likes: 27
From: Under my car
Originally Posted by arghx7
pics of the engine dyno and research lab in your garage?
Apparently, you do not understand how to measure Ve.

If you are suggesting that Honda and Mazda have to cheat to get those numbers...
Reply
Old Jul 21, 2011 | 10:56 AM
  #9  
TeamRX8's Avatar
Registered
iTrader: (25)
 
Joined: Apr 2005
Posts: 26,933
Likes: 2,139
We understand how to measure it, but we also understand that your methods and equipment are not the end all exclamation point to the subject
Reply
Old Jul 21, 2011 | 11:16 AM
  #10  
MazdaManiac's Avatar
Banned
iTrader: (3)
 
Joined: Oct 2003
Posts: 16,386
Likes: 27
From: Under my car
Originally Posted by TeamRX8
We understand how to measure it, but we also understand that your methods and equipment are not the end all exclamation point to the subject
I think we may be missing the point here...
Reply
Old Jul 21, 2011 | 11:49 AM
  #11  
TeamRX8's Avatar
Registered
iTrader: (25)
 
Joined: Apr 2005
Posts: 26,933
Likes: 2,139
I think we can all accept that you are incapable of providing the ideal resources to test the ideal engine under the ideal conditions with the ideal equipment

otherwise if your point is that most owners will never see those numbers from their production engine then we can accept that too

the question is, can you accept that a few elite builders have on occasion seen numbers exceeding the chart?
Reply
Old Jul 21, 2011 | 11:54 AM
  #12  
Flashwing's Avatar
3-wheeler
 
Joined: Dec 2005
Posts: 2,734
Likes: 1
From: Phoenix
Originally Posted by TeamRX8
the question is, can you accept that a few elite builders have on occasion seen numbers exceeding the chart?
Even a broken watch is right twice a day.
Reply
Old Jul 21, 2011 | 11:58 AM
  #13  
MazdaManiac's Avatar
Banned
iTrader: (3)
 
Joined: Oct 2003
Posts: 16,386
Likes: 27
From: Under my car
Originally Posted by TeamRX8
the question is, can you accept that a few elite builders have on occasion seen numbers exceeding the chart?
Oh, absolutely.

But these charts are for stock, OE engines in situ.
Reply
Related Topics
Thread
Thread Starter
Forum
Replies
Last Post
BillBertelli
NE For Sale/Wanted
4
Mar 19, 2016 03:01 PM
Brokegang
New Member Forum
27
Jan 3, 2016 12:45 PM
arexatemate
RX-8 Parts For Sale/Wanted
2
Oct 9, 2015 06:23 PM
Chapsy
RX-8's For Sale/Wanted
1
Sep 22, 2015 09:57 AM
Tsurugi
New Member Forum
0
Sep 7, 2015 08:27 PM



You have already rated this thread Rating: Thread Rating: 0 votes,  average.


All times are GMT -5. The time now is 08:02 PM.