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Hi everybody!
I'd like to know what would be the pros and cons of installing a downpipe on the 1.2 TSI 8v EA111 (CBZ*) engine.

The most important thing to me is TORQUE. I don't want to loose torque at low revs. I want to feel the turbo kick at ~1800-2000rpm.
Do you think that a proper custom remap will be able to give me the torque peak at the same revs I have now? or the torque curve will inevitabily move at higher revs, due to the lower exhaust back-pressure?

What diameter would you suggest?
With or without a sport cat?

Considering the original downpipe has a diameter of 47,5mm, I am thinking about doing a downpipe of 50mm (not too much larger than the original), with a 200 cells sport cat, placed under the front subframe (far enough from the turbo).

What do you think about it?

I think the pros are that it won’t harm performance much, if at all.

The cons are that it will cost you money and have little measurable effect on performance.

You are talking about a mild tune where exhaust diameter is not really critical.

Best to spend the money uprating other areas.

Thank you for your answer.
At the moment, I've already upgraded all the rest (air intake, cat-back exhaust, suspensions, bushings, brakes, headlights, steering wheel, instrument cluster, radio, etc.).
I really enjoy my car as it is now! But if there's still a mod that's really worth doing, I'd like to go for it.

I've always been curious about the downpipe, but I'm a bit afraid of worsening the performances and regretting this mod.

I hope you’ve arranged for the intake to breath cold air from outside. That hot air circulating under the bonnet is very bad for power production. You want dense oxygen rich air to give you a Big Bang. The hotter the air the less power you produce hence intercoolers, cold air scoops etc.

If you look at old pre fuel injection racing cars you might notice that they often had different exhaust systems for different tracks. Power tracks demanded large diameter pipes whilst tracks where torque and flexibility were paramount more modest diameters were employed. The physics still apply although most car manufacturers over specify to allow for engine upgrades, capacity changes etc without having to retool.

Sadly accountants have as much input into car design as engineers, something demonstrated by recent VW antics.

Enjoy your mods, there’s something special about driving a car you have specified and worked on yourself.

Yes! With the help of a friend, I designed and printed a custom plastic intake conveyor, which allows the engine to breathe air directly from the outside (the OEM conveyor forces the engine to suck hot air from the engine compartment).
Thanks to this mod, air intake temperatures dropped about 20°C and performances definetely increased.


I think the downpipe is the last mod I could do for the engine.
I watched many YouTube videos of other people who did this mod (not only on the Polo, but also on the Seat Ibiza) and it seems like they all reached about 150hp. But no one says a thing about the torque figure, which is what really concerns me...

Have you remapped your engine yet? That custom intake also looks quite nice!

Thank you!
Yes! I already have a custom remap.
133hp and 233Nm are the actual results.


As you can see, I have lot of torque at low revs and I really don't want to loose it.
If someone could show me that a donwpipe de-cat (or with a 200 cells sport cat) enhanches the torque curve at all ranges (and gives the engine a nice bump in power), I'd go for it without any further doubts.

P.S. I've never talked about exhaust sound till now, because I'm not primarly looking for an increasement in loudness and/or in tone. But obviously I'd like it to be louder than now.

Well done, that intake adaptor looks really good and puts most pro jobs to shame.

I’ve seen 3D printing in use at the Morgan factory, I guess I’ll have to get off my fat backside and look further into it myself, whilst you are never too old to learn new techniques it sometimes feels like it!

Thanks for giving me the incentive.

You're welcome!

If someone else could share his/her experience and solve my doubts, I'd really appreciate it.

This might be of interest to you. I'm with your thinking, the engine does OK at moderate to high rpm, but a little more torque/push would be welcome low down in rev range. Making gains further up the rev range is relatively easy, but as you say, even without any "physical" modifications the bottom end performance is sacrificed for higher hp at higher rpm.

I don't know what your driving style is but but for myself I would be looking for gains in the low to mid range where I do most of my driving. From what little I've read, unless you start spending large amounts of money you are going to be in the 135-145hp with the 1.2Tsi. At those outputs 47.5 mm looks to be OK. What gains you could expect from a performance cat is a bit more of a mystery. Personally I'd talk to the people doing the re-map first to get their opinion on the best way to improve torque at the bottom end.

Tube OD Tube Radius Tube ID Radius Tube Area Max CFM Max HP

2.00 1.00 0.94 2.75 315.84 143.56

2.25 1.13 1.06 3.53 405.94 184.52

2.50 1.25 1.19 4.41 507.32 230.60

3.00 1.50 1.44 6.47 743.96 338.17

3.50 1.75 1.69 8.92 1025.76 466.26

4.00 2.00 1.94 11.76 1352.73 614.88

https://www.clown-shoe.com/single-post/ ... right-size

I can't remember where I read it but on turbo cars having a little back pressure on the engine side of the turbo can help low end performance. It can give you a greater pressure differential across the turbo which helps at low rpm.

Good stuff though Jay-Jay, your post are always interesting

Thank you, wolfie!
It's really interesting to see how the diameter changes depending on the maximum power output.

This is the dyno test of Rodrigo Garcia's Ibiza 1.2TSI (check him out on YouTube) with a de-catted 2,5" downpipe:

He told me his turbo pressures are the same I already have right now (1,2bar of peak and 1,1bar of constant): this makes me think his ECU map is not pumped.
As you can see in the dyno graph, his engine got almost the same results as mine (~130hp and 220-230Nm) and the torque curve shows that torque increases quickly at low revs, almost as fast as on my engine.

I guess that if he'd have installed a smaller downpipe (2" or 2,25") and if he had a more pumped ECU remap (1,3bar of peak and 1,2bar of constant), he could have gained more torque even at low revs, without sacrificing power at high revs.

My personal tuner suggested me to go for a 2,25" downpipe with a 200cells sport cat placed under the front subframe, for keeping some back-pressure in the exhaust.
But he never did this mod to a 1.2TSI EA111 engine, so he can't guarantee for any (good or bad) final performances result.

Jay-Jay wrote: ↑Sun Jun 30, 2019 11:58 pm Yes! With the help of a friend, I designed and printed a custom plastic intake conveyor, which allows the engine to breathe air directly from the outside (the OEM conveyor forces the engine to suck hot air from the engine compartment).
Thanks to this mod, air intake temperatures dropped about 20°C and performances definetely increased.


I think the downpipe is the last mod I could do for the engine.
I watched many YouTube videos of other people who did this mod (not only on the Polo, but also on the Seat Ibiza) and it seems like they all reached about 150hp. But no one says a thing about the torque figure, which is what really concerns me...

The 3D printed intake plumbing looks really good. The placement of this piece is what makes me think about any modification to be done to intake part to accommodate this inside engine bay. Also, pictures of the installation will be highly appreciated.

No modifications needed.
But we are O.T. here.
Let's continue on my Polo's topic.

Jay-Jay wrote: ↑Sun Jun 30, 2019 11:58 pm Yes! With the help of a friend, I designed and printed a custom plastic intake conveyor, which allows the engine to breathe air directly from the outside (the OEM conveyor forces the engine to suck hot air from the engine compartment).
Thanks to this mod, air intake temperatures dropped about 20°C and performances definetely increased.


I think the downpipe is the last mod I could do for the engine.
I watched many YouTube videos of other people who did this mod (not only on the Polo, but also on the Seat Ibiza) and it seems like they all reached about 150hp. But no one says a thing about the torque figure, which is what really concerns me...

Hi jay,

Is it possible you can share with me the printing details?
Thinking of doing one but cant find any details about this.

Thanks!!

I'm sorry, but I can't, since it's my and my friend's project and we are selling custom intake convejors online (via FB, IG, forums, etc.).
If you are interested in buying it, you can contact me via DM.

Since this topic is specifically related to the 1.2TSI Downpipe question, I ask everybody to be In Topic as much as possible.
For any further questions about other arguments, write a post on my Polo's topic or contact me via DM, please.