Go Back   Team-BHP > Under the Hood > Technical Stuff


Reply
 
Thread Tools Search this Thread
Old 12th July 2013, 08:40   #16
BANNED
 
Join Date: Dec 2011
Location: Chennai
Posts: 818
Thanked: 1,647 Times
Default Re: Low compression ratio diesels coming up

Quote:
Originally Posted by Sutripta View Post
Check out

Any further developements on the Miller Cycle?
Highly probable. But as is the case with most manufacturers, details are never disclosed until the product has been in commercial production for some time. As of now,even the torque and bhp figures haven't been released!
VeyronSuperSprt is offline   Reply With Quote
Old 12th July 2013, 09:41   #17
Senior - BHPian
 
thoma's Avatar
 
Join Date: Oct 2011
Location: Kerala
Posts: 1,750
Thanked: 1,073 Times
Default Re: Low compression ratio diesels coming up

Quote:
Originally Posted by thoma View Post
I didn't fully understand, what exactly is enhanced /changed (if any) so that the compression ratio is found out that it can be reduced?

So, was it mostly for starting that the comp ratio kept higher earlier?
Okay, my question seems immature, reading just the Babbage article and not the Mazda one, as provided by @Sutripta. The article clearly explains:

Quote:
There are two main problems that have been preventing the spread of low-compression-ratio diesels regardless of these merits. The first is the fact that when the compression pressure is reduced, the compression temperature during cold operation is too low to cause combustion, preventing engine-start. The second is the occurrence of misfiring during warm-up operation due to lack of compression temperature and pressure.
Further, the gist of improvements that counter the above issues are

Quote:
The newly adopted multi-hole piezo injectors allow for a wide variety of injection patterns. Precision in injection amount and timing increases the accuracy of mixture concentration control, ensuring cold-start capability. Hardware-wise, the injector is a high-spec type capable of a maximum of 9 injections per combustion. Along with the three basic injections: pre-injection, main injection, and post-injection, different injection patterns will be set according to driving conditions. Definite engine-start even with a low compression ratio is attributable to this precise injection control and also the adoption of ceramic glow plugs.
and

Quote:
Any misfiring that may occur during warm-up operation after engine-start is prevented by adopting a VVL (variable valve lift) system for the exhaust valves. A single combustion cycle is sufficient for the exhaust gas temperature to rise. Given this, the exhaust valves are opened slightly during the intake stroke to regurgitate the hot exhaust gas back into the cylinder, which increases the air temperature. This promotes the elevation of compression temperature, stabilizing ignition.
thoma is offline   (1) Thanks Reply With Quote
Old 12th July 2013, 10:20   #18
BHPian
 
Diesel_convert's Avatar
 
Join Date: Aug 2012
Location: Bangalore
Posts: 146
Thanked: 149 Times
Default

Other than nox improvements, what other benefit?

Don't you lose thermal efficiency lowering compression ratio?

They can probably save weight elsewhere instead of the engine block by making it weaker. Lol 50,000 mile two year engine warranty anyone?

Switch to aluminum body panels maybe...
Diesel_convert is offline   Reply With Quote
Old 12th July 2013, 11:10   #19
BHPian
 
DWind's Avatar
 
Join Date: Apr 2007
Location: Singara Chennai
Posts: 775
Thanked: 168 Times
Default Re: Low compression ratio diesels coming up

As I understand, the new Diesel engines lower the compression ratio (for Nox Reduction and better combustion) but compensate for it by even higher rail pressure. can somebody confirm change in CR pressure?
DWind is offline   Reply With Quote
Old 12th July 2013, 15:07   #20
BHPian
 
Diesel_convert's Avatar
 
Join Date: Aug 2012
Location: Bangalore
Posts: 146
Thanked: 149 Times
Default

Quote:
Originally Posted by DWind View Post
As I understand, the new Diesel engines lower the compression ratio (for Nox Reduction and better combustion) but compensate for it by even higher rail pressure. can somebody confirm change in CR pressure?
I think the part about better combustion is misleading.

It's better combustion in terms of nox production not in terms of mean effective pressure or peak thermal efficiency.


You can see this in Mazda's graph about friction mean effective pressure, which I think is brake mean effective pressure.


Cr pressure, number of nozzles, number of injections only affects spray pattern and atomisation/ mixture formation.

The same advancement in cr technology can be applied to higher compression ratios with better results.


Sorry about the rant as an enthusiast I cannot get over losing efficiency over nox production.

Last edited by Diesel_convert : 12th July 2013 at 15:16.
Diesel_convert is offline   Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
Is it possible to increase the compression ratio pratheesh Technical Stuff 30 10th April 2010 17:58
Changing Compression Ratio & Gear Ratio adheesh Technical Stuff 7 3rd October 2007 09:54
Variable compression ratio engine! amitoj Technical Stuff 8 20th December 2005 21:01
Compression Ratio and NOS Ford Rocam Modifications & Accessories 9 28th June 2005 03:13
Vtec's compression ratio!!! Shan2nu Technical Stuff 8 7th May 2005 23:07


All times are GMT +5.5. The time now is 07:24.

Copyright 2000 - 2017, Team-BHP.com
Proudly powered by E2E Networks