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Old 23rd February 2012, 13:38   #1
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Default Difference between Polo R Cup's 1.6 TDI and Vento/Rapid's 1.6 TDI

One obvious difference is that the Vento/Rapid's engine comes mated to a 5-speed gearbox (vs.) The Polo R cup's engine is mated to a 6-speed box

Itís also public knowledge that the Polo R cup uses a PiperCross Replacement Air filter as standard (in the regular air intake box), but that shouldnít affect power/torque too much.

But does anyone know if there are actual differences in engines b/w Polo R Cup's 1.6 TDI vs. Vento/Rapid's 1.6 TDI? (fuel rail / injectors, turbocharger, etc.)

From specs:
both engines are 1598cc, direct injection, common-rail, turbocharged & intercooled diesels
both engines have the same bore/stroke of 79.5/80.5mm
both engines use the same DOHC, 4 cylinders, 4 valves per cylinder setup
both engines use the same compression ratio of 16.5:1
both engines churn out identical torque figures of 25.5kgm @ 1500~2500rpm

The only noticeable difference I see on paper is:
The Vento/Rapid's 1.6 TDI engine is rated 105bhp @ 4400rpm (vs.) The Polo R cup's engine is rated 129bhp @ 4400rpm

Sources:
Skoda Rapid review, test drive - Review - Autocar India
VW Polo vs Polo R Cup car - Feature - Autocar India

I suspect the Polo R cup has vastly different ECU programming affecting various engine performance factors, but I wonder how the Polo R cup makes higher horsepower, but NOT higher torque.

Please share if you have more info.
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Old 23rd February 2012, 14:58   #2
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Default Re: Differences b/w Polo R Cup's 1.6 TDI vs. Vento/Rapid's 1.6 TDI

I've had a peek into the race car's engine bay.
That turbo definitely looked larger than standard.
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Old 23rd February 2012, 16:56   #3
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Default Re: Differences b/w Polo R Cup's 1.6 TDI vs. Vento/Rapid's 1.6 TDI

It does run a stock replacement pipercross filter, but IMHO that would make only a nigligible difference it at all on the performance.

The Cup car runs the same engine as the 1.6 Vento. Absolutely stock.
Just the exhaust muffler has been modified to provide a slightly throaty note.

Only the tuning is different. The engine map was specifically created for the cup car and that is what results in the higher power figures. The map is built for power and engine life has been compromised. The Cup car's engine is only rated to run about 8000 kms AFAIK.

The RPM limit is around 4700 rpm and that I think its same as in the Vento engine. Thus, the torque has to be higher (because Power = Torque x Engine Speed). So, I feel its a mistake by Autocar that they have mentioned same torque figures.
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Old 23rd February 2012, 18:56   #4
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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
It does run a stock replacement pipercross filter, but IMHO that would make only a nigligible difference it at all on the performance.

The Cup car runs the same engine as the 1.6 Vento. Absolutely stock.
Just the exhaust muffler has been modified to provide a slightly throaty note.

Only the tuning is different. The engine map was specifically created for the cup car and that is what results in the higher power figures. The map is built for power and engine life has been compromised. The Cup car's engine is only rated to run about 8000 kms AFAIK.

The RPM limit is around 4700 rpm and that I think its same as in the Vento engine. Thus, the torque has to be higher (because Power = Torque x Engine Speed). So, I feel its a mistake by Autocar that they have mentioned same torque figures.
Thanks for the response. Autocar does have their data right though.

Check this: Volkswagen Polo Cup India
To quote a snippet from that page: "The Volkswagen Race Polo which will be seen racing for the first time on the Indian tracks at the Polo Cup comes with a 1.6L R4 common rail diesel engine with an output of 130 HP@4400 rpm and torque of 250 Nm@ 1500-2500 rpm"
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Old 23rd February 2012, 22:14   #5
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Default Re: Differences b/w Polo R Cup's 1.6 TDI vs. Vento/Rapid's 1.6 TDI

Quote:
Originally Posted by kryptonite View Post
... I wonder how the Polo R cup makes higher horsepower, but NOT higher torque.
Its because whats written on paper is PEAK torque.

After that point is where the differences begin! The Vento's toque curve starts to drop much more rapidly than the Polo R Cup car's.

To add some perspective to this : We can figure out how much torque was produced at 4,400 RPM using this formula (since we know the HP produced) :
HP = TORQUE (in lb-ft) X RPM / 5252


I drew this out on a graph, which makes it easier to understand :

Name:  xA9ki.png
Views: 11781
Size:  20.1 KB

cya
R

Last edited by Rehaan : 5th March 2012 at 12:25.
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Old 24th February 2012, 08:09   #6
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Default Re: Differences b/w Polo R Cup's 1.6 TDI vs. Vento/Rapid's 1.6 TDI

Quote:
Originally Posted by Rehaan View Post
Its because whats written on paper is PEAK torque.

After that point is where the differences begin! The Vento's toque curve starts to drop much more rapidly than the Polo R Cup car's.


Thanks! makes sense.

Do you know if there are changes to any engine components, Or is all of this just accomplished through a re-map?

Last edited by Rehaan : 24th February 2012 at 08:58. Reason: Shortening quote
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Old 24th February 2012, 11:48   #7
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Default Re: Differences b/w Polo R Cup's 1.6 TDI vs. Vento/Rapid's 1.6 TDI

Quote:
Originally Posted by kryptonite View Post
Thanks! makes sense.

Do you know if there are changes to any engine components, Or is all of this just accomplished through a re-map?
Remap only. No change to any components
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Old 24th February 2012, 18:16   #8
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Default Re: Difference between Polo R Cup's 1.6 TDI and Vento/Rapid's 1.6 TDI

This is another case where only the peak torque has been taken for comparison, and not the torque spread.

The low end torque of the older diesels is similarly underrated. Older generation diesel cars exhibited higher torque at low RPM compared modern engines. So if you took the peak torque, they had poor figures. But drive them at low speed on steep bad roads and you are amazed at the performance.
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Old 25th February 2012, 00:29   #9
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Default Re: Difference between Polo R Cup's 1.6 TDI and Vento/Rapid's 1.6 TDI

Quote:
Originally Posted by Aroy View Post
This is another case where only the peak torque has been taken for comparison, and not the torque spread.

The low end torque of the older diesels is similarly underrated. Older generation diesel cars exhibited higher torque at low RPM compared modern engines. So if you took the peak torque, they had poor figures. But drive them at low speed on steep bad roads and you are amazed at the performance.
I didn't quite understand. Which context are you referring to? Please do elaborate
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Old 25th February 2012, 13:14   #10
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Default Re: Difference between Polo R Cup's 1.6 TDI and Vento/Rapid's 1.6 TDI

Quote:
Originally Posted by kryptonite View Post
I didn't quite understand. Which context are you referring to? Please do elaborate
I think Aroy was pointing out the fact that, even though the older gen diesels had very low torque figures on paper, the driveability factor was much high, hence the practicality. ie, just having higher torque figures on paper (on a narrow rpm spread) doesn't matter much.

Torque, consistent over a wide rpm range should give better performance and practicality. That is what the remap has made the polo engine into.

In short: The more the area under the torque curve, the better.
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Old 25th February 2012, 21:10   #11
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Default Re: Difference between Polo R Cup's 1.6 TDI and Vento/Rapid's 1.6 TDI

Quote:
Originally Posted by dhanushs View Post
I think Aroy was pointing out the fact that, even though the older gen diesels had very low torque figures on paper, the driveability factor was much high, hence the practicality. ie, just having higher torque figures on paper (on a narrow rpm spread) doesn't matter much.

Torque, consistent over a wide rpm range should give better performance and practicality. That is what the remap has made the polo engine into.

In short: The more the area under the torque curve, the better.

Thanks for clarifying dhanushs, and for your previous response Aroy.

Yes, I do comprehensively understand the torque spread portion of the equation; one of the reasons why the Laura 1.8 TSI is that much fun to drive right from the word go - all the way till its redline ;-). I got momentarily confused in the middle about how older diesel tech is related to the Polo R cup's engine

BTW - if any of you are interested in looking at my Rapid's dyno graphs (Stock & +Tuning box maps), feel free to navigate from this index here in my ownership thread: http://www.team-bhp.com/forum/test-d...ml#post2595142

Appreciate the responses again, everyone! Thanks
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Old 5th March 2012, 10:23   #12
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Thumbs up Re: Differences b/w Polo R Cup's 1.6 TDI vs. Vento/Rapid's 1.6 TDI

Quote:
Originally Posted by Rehaan View Post
Its because whats written on paper is PEAK torque.

After that point is where the differences begin! The Vento's toque curve starts to drop much more rapidly than the Polo R Cup car's.

To add some perspective to this : We can figure out how much torque was produced at 4,400 RPM using this formula (since we know the HP produced) :
HP = TORQUE (in lb-ft) X RPM / 5252


Representing this graphically, which makes it easier to understand :

Attachment 892953

cya
R

That is a really flat torque curve, even just 300 RPMs short of redline its delivering a lot of torque. I am not sure We'll be able to get all the details of a car designed for races but this kind of torque delivery might be something worth considering in large-ish cars where even a smaller capacity diesel might be enough.
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Old 5th March 2012, 12:24   #13
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Default Re: Difference between Polo R Cup's 1.6 TDI and Vento/Rapid's 1.6 TDI

The graph in the post above is something that i drew myself.

Here's the actual Vento TDI power graph from the brochure :

Difference between Polo R Cup's 1.6 TDI and Vento/Rapid's 1.6 TDI-vento-tdi-capture.png

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Old 7th March 2012, 10:01   #14
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Default Re: Differences b/w Polo R Cup's 1.6 TDI vs. Vento/Rapid's 1.6 TDI

As Rehaan has summed it up very nicely, same peak torque & higher peak power means that only top end is improved. Which is ideal since it is meant for racing. Till 3000-3500 RPM may be both the cars feel same. Anyone here has driven both?

The Polo cup with the extra bit of power & 1 extra speed (transmission) is one hell of a car I guess.


Quote:
Originally Posted by jalsa777 View Post
The Cup car's engine is only rated to run about 8000 kms AFAIK.

The RPM limit is around 4700 rpm and that I think its same as in the Vento engine.
8000 Kms. Are you sure. Did you miss a zero by any chance.
The RPM limit cant be 4700. It is well above 5K.
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Old 7th March 2012, 10:21   #15
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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
As Rehaan has summed it up very nicely, same peak torque & higher peak power means that only top end is improved. Which is ideal since it is meant for racing. Till 3000-3500 RPM may be both the cars feel same. Anyone here has driven both?

The Polo cup with the extra bit of power & 1 extra speed (transmission) is one hell of a car I guess.

8000 Kms. Are you sure. Did you miss a zero by any chance.
The RPM limit cant be 4700. It is well above 5K.
I haven't driven the Vento, so can't comment on the first point. 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.

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.

The RPM limit is 4700. Here's proof:
Name:  Polo R Cup_RPM.jpg
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Size:  35.3 KB

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.
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