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


Reply
 
Thread Tools Search this Thread
Old 7th March 2012, 10:57   #16
Senior - BHPian
 
oxyzen's Avatar
 
Join Date: Feb 2010
Location: Not fixed.
Posts: 1,026
Thanked: 265 Times
Default Re: Differences b/w Polo R Cup's 1.6 TDI vs. Vento/Rapid's 1.6 TDI

Quote:
Originally Posted by jalsa777 View Post
But the gearing is different and the gears would be more closely packed in (ratio wise) due to the six-speed box, so expect better usage of the available power.
Actually, we have never used anything above 4th gear on the Coimbatore and Chennai circuits.
That means it is not close enough. You only got to use 4.

Quote:
Originally Posted by jalsa777 View Post
The RPM limit is 4700. Here's proof:
And look at the torque; we don't downshift even at 2000 rpm. The diesel mill just pulls cleanly from even that low an RPM. This gives proof of a pretty flat torque curve.
Is 4700 the limit or you guys just up-shifted at that point. I am quite positive Vento revs till 5300. (Never tried it though)

Yes diesels pull cleanly from 2000 RPM but as per my limited knowledge goes, I think to extract the most from the engine it is best to keep the car around max power point. Maybe somewhere around 3500-4700. But during racing too many gearshifts stymie progress. Probably the reason why you went to 2000. Or is it something else.

Last edited by oxyzen : 7th March 2012 at 10:58.
oxyzen is offline   Reply With Quote
Old 7th March 2012, 12:04   #17
Distinguished - BHPian
 
dhanushs's Avatar
 
Join Date: Oct 2009
Location: Bathery/BLR
Posts: 3,446
Thanked: 4,057 Times
Default Re: Differences b/w Polo R Cup's 1.6 TDI vs. Vento/Rapid's 1.6 TDI

Quote:
Originally Posted by oxyzen View Post
That means it is not close enough. You only got to use 4.
Not really, maybe on-track , the speed @4 gear @4.7k is all you can accelerate to. Anything shorter would want more frequent gear changes, and time for a change when converted to distance is huge.

Quote:
Originally Posted by oxyzen View Post
I think to extract the most from the engine it is best to keep the car around max power point. Maybe somewhere around 3500-4700. But during racing too many gearshifts stymie progress. Probably the reason why you went to 2000. Or is it something else.
I think in these engines, its the massive pulling power you should use to propel your car.

jalsa777, can confirm.
dhanushs is offline   Reply With Quote
Old 7th March 2012, 16:03   #18
BANNED
 
Join Date: Nov 2011
Location: Bangalore
Posts: 169
Thanked: 1,224 Times
Default Re: Difference between Polo R Cup's 1.6 TDI and Vento/Rapid's 1.6 TDI

Ok, so I plotted 4 graphs - See attachments:

Dark blue = Torque measured from my stock Rapid i.e. 280NM peak @ 2169rpm (rated 250Nm @ 1500~2500rpm)
Light blue = Power measured from my stock Rapid i.e. 103Hp peak @ 3429rpm (rated 105ps @ 4400rpm)
- my dyno graphs are attached at the bottom of this post in my ownership thread: http://www.team-bhp.com/forum/test-d...ml#post2652242

Dark red = Hypothetical torque produced by the Polo cup; in this case I'm assuming the peak to be the same as my Rapid, and not the rated 250NM@1500~2500rpm
Light Red = Hypothetical power produced by the Polo cup i.e. 130HP @ 4400rpm

Quite a few assumptions were made, but I think this will do well for illustration purposes as it is to scale ;-)

Also feel free to play around with the attached spreadsheet, which was how I arrived at the graphs in the first place
Attached Images
 
Attached Files
File Type: xlsx Stock Rapid 1.6 TDI vs. Polo Cup 1.6 TDI.xlsx (14.6 KB, 296 views)
kryptonite is offline   (1) Thanks Reply With Quote
Old 9th March 2012, 11:10   #19
BHPian
 
jalsa777's Avatar
 
Join Date: May 2006
Location: Mumbai
Posts: 637
Thanked: 1,044 Times
Default Re: Difference between Polo R Cup's 1.6 TDI and Vento/Rapid's 1.6 TDI

Quote:
Originally Posted by oxyzen View Post
That means it is not close enough. You only got to use 4.

Is 4700 the limit or you guys just up-shifted at that point. I am quite positive Vento revs till 5300. (Never tried it though)

Yes diesels pull cleanly from 2000 RPM but as per my limited knowledge goes, I think to extract the most from the engine it is best to keep the car around max power point. Maybe somewhere around 3500-4700. But during racing too many gearshifts stymie progress. Probably the reason why you went to 2000. Or is it something else.
1. As pointed out by dhanushs, we are restricted by the length of the straights.

2. We shift at almost the red-line. Anything below that won't be optimal. So, 4700 RPM is the red-line.

3. Its all about the torque actually. You are pushed forward by torque. Thus, your gearshifts should be such that you extract maximum torque. In a diesel engine, there is plenty of torque from low RPMs, hence no need to downshift. If it were a petrol, things would be different. Also, in the polo's, if we were to downshift to second, we would have to upshift again very quickly without gaining much benefit, resulting in net loss of time.
jalsa777 is offline   (1) Thanks Reply With Quote
Old 23rd June 2013, 00:41   #20
BHPian
 
man_and_machine's Avatar
 
Join Date: Aug 2008
Location: Bangalore
Posts: 428
Thanked: 215 Times
Default Re: Difference between Polo R Cup's 1.6 TDI and Vento/Rapid's 1.6 TDI

Great discussion, OT, but highly impressive.
I was looking to study torque curves or various engines for a technical analysis and google landed me in their 2 link rank this thread! Great! There are hundreds of links of Diesel engine torque curves etc, but the google rating system which works on relevance links me up in their top 5 links my favourite Team-BHP link. When I went thought the thread, its a good case study on same bore/stroke giving different torque curves with stock engine block. Just wanted to share this little google rank surprise.
man_and_machine is offline   (1) Thanks Reply With Quote
Old 23rd June 2013, 10:09   #21
BHPian
 
d_himan's Avatar
 
Join Date: Nov 2006
Location: Bombay
Posts: 728
Thanked: 591 Times
Default Re: Differences b/w Polo R Cup's 1.6 TDI vs. Vento/Rapid's 1.6 TDI

Quote:
Originally Posted by jalsa777 View Post
AFAIK, 8000 kms it is. But I got to know this figure in a very casual discussion which i frankly don't even recall properly. But its in the where abouts for sure.
Wow, so there's always a price to pay when you fiddle around with the stock motor's torque curve..?
d_himan is offline   Reply With Quote
Old 12th February 2015, 01:05   #22
BANNED
 
Join Date: Nov 2011
Location: Bangalore
Posts: 169
Thanked: 1,224 Times
Default Re: Difference between Polo R Cup's 1.6 TDI and Vento/Rapid's 1.6 TDI

I remember starting this thread during the early days of my Rapid ownership. I guess I've come a long way.

Here's my write up on our Drag win at the Valley Run, 2015:
http://www.team-bhp.com/forum/indian...ml#post3643235

Hope you enjoy reading this as much as I did putting it together. Cheers!
P.S: Dyno graphs are attached ;-)
kryptonite 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
Vento / Rapid or VW Polo GT TDI Barron What Car? 66 15th March 2017 02:32
VW Vento Cup for 2015! Replaces the Polo Cup S2!!! Indian Motorsport 7 4th August 2015 16:29


All times are GMT +5.5. The time now is 22:33.

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