[d3mon]

Great results!

I am still wondering why Volkswagen chose to combine the two cooling circuits? Did they really save much cost with that given that there are two pumps already in the system?

Or was the combined system needed because the mechanical pump alone can't keep the engine cool? Or because they somehow wanted to control the head & the block temperatures to different levels for optimum efficiency? (The diagram mentions this) Did you notice any changes in the coolant and/or engine oil temps after the mod?

[TheLizardKing]

Originally Posted by d3mon

I am still wondering why Volkswagen chose to combine the two cooling circuits? Did they really save much cost with that given that there are two pumps already in the system?

For a mass-produced car, even the savings from skipping an auxiliary coolant reservoir and the associated plumbing matter.

Originally Posted by d3mon

Or was the combined system needed because the mechanical pump alone can't keep the engine cool? Or because they somehow wanted to control the head & the block temperatures to different levels for optimum efficiency? (The diagram mentions this)

If you study the diagram closely, you will see that the two circuits only share the coolant reservoir. They have independent pumps and radiators. The mechanical pump and main radiator are responsible for cooling the engine. Suhaas's mod doesn't change that. It just:

1. Divorce 1 - moves the turbo from the secondary (electric pump) to the primary (mechanical pump) circuit, and
2. Divorce 2 - gives the secondary circuit its dedicated coolant reservoir.

The head and block temperatures determine at what point the main radiator enters the primary circuit. Nothing to do with this mod.

Originally Posted by d3mon

Did you notice any changes in the coolant and/or engine oil temps after the mod?

I am pretty sure there won't be any significant changes.

[suhaas307]

Originally Posted by Viraat13

That drop in IAT is huuuuge.
10/10 again for you man. Great research and insight, along with the data to back it up.
This neatly summaries the endless discussions on WhatsApp. Looking forward to your thoughts on this set up after some usage.

All credits go to Venkat and Chandru - Blackworks. Credits should be reserved for Akshay too, for the bet he placed with Venkat to find a sustainable solution. *Wink*

Originally Posted by Viraat13

One thing I'd like to point out, the cooling system is pressurised; now I'm not sure if the circuit running on the electric pump needs that pressure, but that's one thing to check before you start using a fabricated coolant bottle. Also another minor additional mod that you can consider: secondary low coolant warning. I'd done some reading about this a while ago, let me know if you want me to dig that out and send it to you.

Don't think there's any pressure as such, definitely not at the levels of the primary lines.

Venkat is exploring various options, from fabricating a tank to using a 2 litre (thermal) metal flask in lieu of the auxiliary reservoir. I'm leaning towards the flask.

Originally Posted by d3mon

Great results!

I am still wondering why Volkswagen chose to combine the two cooling circuits? Did they really save much cost with that given that there are two pumps already in the system?

Thank you!

The answer to this is below:

Originally Posted by TheLizardKing

For a mass-produced car, even the savings from skipping an auxiliary coolant reservoir and the associated plumbing matter.

Also, have a look at my take-aways and the olive anecdote. *Wink wink*

Originally Posted by d3mon

Or was the combined system needed because the mechanical pump alone can't keep the engine cool? Or because they somehow wanted to control the head & the block temperatures to different levels for optimum efficiency? (The diagram mentions this) Did you notice any changes in the coolant and/or engine oil temps after the mod?

The mechanical pump is more than sufficient to service the cooling functions of the engine generally. But an electric water pump was introduced because in essence, the circuits for the engine cooling system and the turbo/charged air are separate.

Moreover, the electric water pump features in the setup for one reason: idiot proofing the car.

Unlike the mechanical water pump that stops functioning the moment the car is switched off, the electric water pump continues to service the turbo's coolant line for a short duration after the car is shut down, in order to preserve the turbo in the event of a "hot-shut-down" of the engine.

Now that the electric water pump only services the coolant line for charged air, there is a very slight element of risk if I hot-shut-down the car - something I obviously wouldn't do and haven't done anyway throughout the car's ownership - so the element of risk does not exist for me!

Back in the day, some turbocharged cars were equipped with turbo-timers that would keep the car running even after the ignition was turned off - but this was subsequently done away with in the interest of emissions and fuel economy. This is where electric pumps came into the picture.

Turbo-timers are still available in the market, but none of them are designed to work with German cars. That being said, I'm not 100% sure of this.

Regarding your query on changes in coolant temps - it has remained constant so far, and as TheLizardKing mentioned above, there wouldn't ordinarily be any fluctuations in coolant temps as a result of this modification.

[shibujp]

Originally Posted by suhaas307

This hack is not breaking news in the world of engineering and in tuning circles – it’s usually referred to as a divorced coolant-circuit system. In this case, I have taken the liberty (much to Venkat’s dismay) of christening it – “Blackworks Engineering Double-Divorced Coolant-Circuit” – cringeworthy but I hope it catches on!

Interesting find that deserves top praise and good fix. One question I have, will this fix along deliver better performance to stock vehicles? Or is the IAT under control on a hot day with the stock engine no matter how hard you run it?

Drive on,
Shibu.

[suhaas307]

Originally Posted by shibujp

Interesting find that deserves top praise and good fix. One question I have, will this fix along deliver better performance to stock vehicles? Or is the IAT under control on a hot day with the stock engine no matter how hard you run it?

Drive on,
Shibu.

Hi Shibu,

Thank you for the kind words!

Yes, this modification will work for all GT TSIs, whether stock or modified. Stock TSI engines also suffer from heat-soak and won't perform to the best of their abilities when the ambient temps rise above 30-35 degree Celsius.

On the highway, the problem wouldn't be quite so severe if you are cruising, as you are constantly moving at speeds and thus the engine would benefit from a continuous flow of air, keeping the IATs in check somewhat. But the problem arises when you do hard runs and put the engine under load on the highways.

In the city, this modification should benefit greatly as these cars tend to sit in traffic for prolonged periods of time and short bursts between traffic lights would further compound the problem, resulting in a severe spike in IATs.

It is recommended that you open up the intake pipe to the grille though, as all stock GT TSI intakes draw their air form the engine bay. the 'Euro Duct' should help with this.

[TheLizardKing]

Originally Posted by suhaas307

It is recommended that you open up the intake pipe to the grille though, as all stock GT TSI intakes draw their air form the engine bay. the 'Euro Duct' should help with this.

Slight correction: Some time after 2017, VW India has started supplying the Euro spec air intake as stock. I found this when I had to get a new one after my MY 2015 GT TSI had an accident.

[Sankar]

Originally Posted by suhaas307

3) The engineers at Volkswagen are not stupid. They knew exactly what they were doing when they engineered this motor. They may have left something on the table for the enthusiasts, but the real reason for this compromised system is – cost! Every penny counts! Ever heard of the American Airline olive from the 1980s, that saved the airline company $100,000 a year by just deleting one olive from every salad that was served to each passenger on the airline?

They are not stupid, they wanted to keep coolant flowing through the turbo after the engine was shut down, if so required. The coolant pump can be run by the ECU and can run till the temperature is within the set limit. Based on which TSI engine it is the run time are set different. if VW wanted to put the turbo on the main coolant circuit (like how it was done here) they then will have to use another electric aux pump on the main circuit to keep coolant running through the turbo once engine is shut down.







https://www.briskoda.net/forums/topi...turbo-cooling/

Originally Posted by suhaas307

So, what was going on? Members on the forum have gone to great lengths to explain the nuances of the GT TSI’s coolant setup, so here are the highlights:

Unlike many other turbocharged cars, the 1.2 TSI utilizes a cooling system that is, in theory, a very efficient setup. There is a primary radiator that is used to cool the head, the block, the throttle body, etc. The coolant that is used to cool these components is pumped through circuit No. 1 by a mechanical water pump. And then you have another radiator that is responsible for cooling the turbocharger and the charged air. The coolant for the turbo and the charged air is pumped through circuit No. 2 by an electric water pump.

Yes, see the post below.

https://www.team-bhp.com/forum/offic...ml#post3122519 (Volkswagen Polo 1.2L GT TSI : Official Review)

I wondered (then) why VW plugged the hot turbo in the electric pump driven line which also serviced the watercooled intercooler. Unless ofcourse they wanted to pump water through the turbo's core when engine is shut down.

[Sankar]

PS: No need for another expansion tank really even if you want to do this, single tank is more than enough. What is needed is another ECU switchable electric pump on the turbo's coolant line. If VW deemed it necessary to have an electric pump on turbo's coolant, circuit unlike their old 1.8 TPI engines, better to use one if its a daily driver.

[suhaas307]

Originally Posted by Sankar

They are not stupid, they wanted to keep coolant flowing through the turbo after the engine was shut down, if so required. The coolant pump can be run by the ECU and can run till the temperature is within the set limit. Based on which TSI engine it is the run time are set different. if VW wanted to put the turbo on the main coolant circuit (like how it was done here) they then will have to use another electric aux pump on the main circuit to keep coolant running through the turbo once engine is shut down.

I wondered (then) why VW plugged the hot turbo in the electric pump driven line which also serviced the watercooled intercooler. Unless ofcourse they wanted to pump water through the turbo's core when engine is shut down.

Thank you, Sankar.

I should have expanded on that point further in the main post, but if you had flipped over to the next page you would have noticed this:

Originally Posted by suhaas307

The mechanical pump is more than sufficient to service the cooling functions of the engine generally. But an electric water pump was introduced because in essence, the circuits for the engine cooling system and the turbo/charged air are separate.

Moreover, the electric water pump features in the setup for one reason: idiot proofing the car.

Unlike the mechanical water pump that stops functioning the moment the car is switched off, the electric water pump continues to service the turbo's coolant line for a short duration after the car is shut down, in order to preserve the turbo in the event of a "hot-shut-down" of the engine.

Now that the electric water pump only services the coolant line for charged air, there is a very slight element of risk if I hot-shut-down the car - something I obviously wouldn't do and haven't done anyway throughout the car's ownership - so the element of risk does not exist for me!

Back in the day, some turbocharged cars were equipped with turbo-timers that would keep the car running even after the ignition was turned off - but this was subsequently done away with in the interest of emissions and fuel economy. This is where electric pumps came into the picture.

Turbo-timers are still available in the market, but none of them are designed to work with German cars. That being said, I'm not 100% sure of this

Originally Posted by Sankar

PS: No need for another expansion tank really even if you want to do this, single tank is more than enough. What is needed is another ECU switchable electric pump on the turbo's coolant line. If VW deemed it necessary to have an electric pump on turbo's coolant, circuit unlike their old 1.8 TPI engines, better to use one if its a daily driver.

Ideally VW should have given it two aux-electric water pumps, (one for the turbo cooling line and the other for the charge cooling line), to supplement the main mechanical water pump (for the rest of it), and maybe even a larger reservoir to make it work well. But VW is known to indulge in cost cutting. I'm sure you're no stranger to that.

I did mention the workaround that this entails in the same post, i.e. to keep it running for a couple of minutes after a hot run.

Could you help me understand how a single reservoir would work in this scenario? Or do you feel a larger one could work better?

[venkyhere]

Originally Posted by suhaas307

3) The engineers at Volkswagen are not stupid. They knew exactly what they were doing when they engineered this motor. They may have left something on the table for the enthusiasts, but the real reason for this compromised system is – cost! Every penny counts!

Exactly. That is single point about which I have a Q.

Even without a divorced ckt (which will need another tank), the VW engineer who designed the coolant system could have easily kept the turbo as part of the main coolant ckt, and only charge air cooling for the electric pump driven ckt - still sharing the same expansion tank. Instead of two 'parallel' paths (one to the water-to-air IC and one to the turbo water jacket), the electric pump would have had to serve only one path (water-to-air IC). The crank driven mechanical water pump would have had one additional "serial load" item, viz the turbo's water jacket, alongwith radiator, engine channels, oil cooler etc - everything else remaining same.

Why didn't VW do that ? wouldn't have changed existing cost.

That is why, I have a fear that there is some engineering reason (beyond the hot-shutdown-of-turbo reason) that is hiding itself. Not trying to undermine your's or Blackworks' effort or the sheer brilliance of the idea, but trying to dive really deep into the technicality of "why did they design it the way it is in stock form". To me, it seems it couldn't have been for saving costs alone.

[Tassem]

As a huge fan of the Polo - GT TSI, GT TDI and of course the GTi, I thoroughly enjoyed your recap of everything you've done to your car. After a long time, I found myself having read an entire thread!

You've also given Blackworks a new customer. I'd be reaching out to them for possibly a straight pipe setup for my D'max. Like you, I've pretty much done all that's possible. But like you, I keep discovering new things to do every single time I think I'm done

Would love to catch up with you sometime. I've been on the look out for a GTi, but the added practicality, not to mention much lower cost of entry, makes the GT TSI very appealing to me.

[shoaib3030]

Originally Posted by suhaas307

You may want to check out my latest update below! *wink wink*



I did consider this briefly, but the problem with the valvetronic vacuum actuated cut-out is the straight-through-like exhaust note, which sounds fine on ....

Stay tuned for more updates.

This was such a great read! Thank you for posting this. I love the experimental approach. "Maybe this? Maybe that? Let's go try it out on NICE. Hey! It works!" This is in fact what makes great products.

Also, I experienced the same issues with my TSI but now I'm glad that there's a new christened solution for this

I've been making a checklist of things that I want to get done on my car. This will make the list!

[vinay5795]

Loved the post truly man. I was pondering about tweaking my Vento TDI but was sacred about the DSG going kaput. And the thing about changing hoses to make the car essentially cooler is pure genius. I didnt know the cheeky VW guys wanted the car to not be mod friendly. I was under the impression that VWs are a modders wet dream.

[suhaas307]

Originally Posted by venkyhere

Exactly. That is single point about which I have a Q.

Why didn't VW do that ? wouldn't have changed existing cost.

That is why, I have a fear that there is some engineering reason (beyond the hot-shutdown-of-turbo reason) that is hiding itself. Not trying to undermine your's or Blackworks' effort or the sheer brilliance of the idea, but trying to dive really deep into the technicality of "why did they design it the way it is in stock form". To me, it seems it couldn't have been for saving costs alone.

Hi Venky,

I understand your concern.

We looked into all possible reasons as to why they had done this, and we are of the opinion that Volkswagen may have left something on the table for:

(a) enthusiasts to tap into the potential, and

(b) Volkswagen themselves to make a more powerful version of the same 1.2 TSI engine, without altering the capacity - by simply employing the same divorced-circuit hack, adding an additional electric pump for the turbocharger, and tweaking the map further. This alone would have unlocked a healthy amount of horsepower.

But then they decided to ditch this engine altogether and start afresh - with the EA211 - same configuration 1.2 TSI 4-cylinder turbo - albeit with forged internals, dual-overhead camshafts (DOHC) and 4-valves per cylinder - (16 valve unit).

Originally Posted by Tassem

As a huge fan of the Polo - GT TSI, GT TDI and of course the GTi, I thoroughly enjoyed your recap of everything you've done to your car. After a long time, I found myself having read an entire thread!

You've also given Blackworks a new customer. I'd be reaching out to them for possibly a straight pipe setup for my D'max. Like you, I've pretty much done all that's possible. But like you, I keep discovering new things to do every single time I think I'm done

Would love to catch up with you sometime. I've been on the look out for a GTi, but the added practicality, not to mention much lower cost of entry, makes the GT TSI very appealing to me.

Thank you, Tassem! Your D-max would benefit greatly from well-thought-out upgrades. Please do not hesitate to drop me a PM. We can schedule a meet-greet. I'm always up to meet fellow enthusiasts.

Originally Posted by shoaib3030

This was such a great read! Thank you for posting this. I love the experimental approach. "Maybe this? Maybe that? Let's go try it out on NICE. Hey! It works!" This is in fact what makes great products.

Also, I experienced the same issues with my TSI but now I'm glad that there's a new christened solution for this

I've been making a checklist of things that I want to get done on my car. This will make the list!

Thank you, Shoaib!

Originally Posted by vinay5795

Loved the post truly man. I was pondering about tweaking my Vento TDI but was sacred about the DSG going kaput. And the thing about changing hoses to make the car essentially cooler is pure genius. I didnt know the cheeky VW guys wanted the car to not be mod friendly. I was under the impression that VWs are a modders wet dream.

Thank you, Vinay! The fear of the DSG going kaput is always in the back of my mind, but I've learned to make my peace with it.

Originally Posted by Sankar

PS: No need for another expansion tank really even if you want to do this, single tank is more than enough. What is needed is another ECU switchable electric pump on the turbo's coolant line.

Hi Sankar,

I looked into this suggestion of yours, about not requiring another expansion tank and that a single tank is more than enough, as it seemed to be an interesting idea.

But upon further inspection, I had realised that you are wrong and the suggestion was entirely incorrect! An auxiliary tank is extremely essential for this hack to work.

In fact, without this auxiliary tank, the entire purpose of this hack would be defeated, making this modification a completely pointless exercise!

Allow me to explain:

(1) In stock form, both primary and secondary cooling circuits eventually use ONE coolant reservoir/tank.

(2) If we use the same coolant (from the ONE reservoir) that's pumped and circulated throughout the engine, we are essentially trying to cool the charged air using hot coolant! How pointless is that!?

(3) However, if we use a separate tank to store coolant that is separate from the main circuit, the new tank will circulate coolant through the secondary line that is now dedicated to cool charged air only. Keeping the coolants separate would ensure that the secondary line gets coolant at ambient temperatures circulated through it.

Here is conclusive proof for you:

Coolant temps in the primary coolant reservoir, after a 15 km drive:


Coolant temps in the auxiliary coolant reservoir, after the same 15 km drive, on the same day:

Originally Posted by Sankar

If VW deemed it necessary to have an electric pump on turbo's coolant, circuit unlike their old 1.8 TPI engines, better to use one if its a daily driver.

VW deemed it necessary to have an electric pump on the turbo's coolant lines to prevent the turbo from long-term degradation as a result of hot-shut-downs, as I have mentioned repeatedly prior to your posts. It was done to "idiot proof" the car. Again, at the risk of repeating myself, the simple work around to this is to keep the engine running for a couple of minutes after a hot run, in order to allow the turbo to cool down - a practice that i have followed and is also recommended on this Forum here - https://www.team-bhp.com/tech-stuff/...o-charged-cars

Sankar, from your posts, it appears that you have entirely failed to understand this modification and its purpose? If you are having any difficulty, please don't hesitate to post your clarifications here and I can help explain. (Or you could alternatively PM me, but I would not recommend that as it wouldn't benefit the larger community if your clarifications are addressed privately.)

__________________________________________________ _____

UPDATE:

With some free time over the weekend, Venkat called me over for:

1) Taking measurements of all pipes, hoses and the coolant-plumbing circuit.

2) Studying the auxiliary reservoir with the intention to find a permanent solution.

I had ordered a bunch of parts, including a coolant reservoir, a bunch of clamps and the entire coolant hose-network from Boodmo last week. But with no sign of the the parts being shipped for another two weeks, we were anxious to get the work done with and not leave it in the state that it was in.

Venkat proposed using a thermal flask in lieu of the temporary coolant tank, the only requirements were:

(a) To engineer a bracket and mounting point for the bottle

(b) bore a hole at the bottom of the bottle, weld a nipple to the bottom for the coolant circuit connection.

It did not take long to achieve these targets:

Attachment 2012181










The carpeting on the bulkhead / firewall is secured using a screw and a washer. We repurposed this to install the mounting plate and bracket for the bottle by simply unscrewing it, mounting the bracket and reusing the same washer.



The results:



The time it took to weld the nipple and figure out a mounting solution for the bottle allowed Venkat to further examine the coolant circuits. We discovered that the existing circuits were long enough to be used for the re-routing exercise without the need for additional parts - scraps or otherwise!

Thus, the re-routing exercise commenced, and the bottle was mounted as well, and it took us only an hour or so to complete the job. The results are fantastic, as the circuits now look factory-spec and I'm certain your average VW service advisor would be hard-pressed to find any changes from a glance or even a quick examination:



In fact, I'm sure they would ask me if I am missing a water bottle because I may have lost it in the engine bay!

[Dr.Naren]

It's really a great work. I have seen many tuners struggle to make good power with 1.2 TSI, thanks to super high IAT. This hack / engineering is working really well, thanks for all the hard data like IAT, Coolant temperature etc. I believe only thing to take care of is not to switch off the engine immediately after hard driving

Suhaas, I have a doubt if Frank Mehta's Coolant cooler was actually a divorced circuit.

https://www.team-bhp.com/forum/modif...my-gt-tsi.html (Upping the Cool quotient: Add-on Coolant Cooling system on my GT TSI!)