intercooler tank design question

[ptuomov]

“If you are so wise and know where the improvements in turbocharger response have come from in say....the last 10-15 years, where have they come from?”

I don’t know. If I were to guess, I’d guess that variable valve timing would be the most important contributor to the wider power band and better perceived throttle response. The overall turbocharger control logic would be the second guess. The improved combustion modeling and engine control that allows for higher compression ratio would also be a factor. Compared to 1980’s, pulse turbocharging with minimized exhaust manifold volume and separation of pulses would be a factor for some engines. Electronically controlled valve(s) in the turboback exhaust would be a contributor. Note that I am saying these are (what I guess) the main contributors to the improved throttle response perception, not necessarily to some more specialized definition of turbo response.

[LoganD]

“If you are so wise and know where the improvements in turbocharger response have come from in say....the last 10-15 years, where have they come from?”

I don’t know. If I were to guess, I’d guess that variable valve timing would be the most important contributor to the wider power band and better perceived throttle response. The overall turbocharger control logic would be the second guess. The improved combustion modeling and engine control that allows for higher compression ratio would also be a factor. Compared to 1980’s, pulse turbocharging with minimized exhaust manifold volume and separation of pulses would be a factor for some engines. Electronically controlled valve(s) in the turboback exhaust would be a contributor. Note that I am saying these are (what I guess) the main contributors to the improved throttle response perception, not necessarily to some more specialized definition of turbo response.

A '97 Toyota Supra Turbo has VVTi, sequential turbocharging, electronic wastegate actuation, electronic surge valve control, etc. It has much worse "throttle response" than even a cheap turbo engine such as the one in a VW GTI, not to mention worse torque and hp/l. The '97 Supra Turbo engine has ~8.7:1 compression, the VW GTI engine has ~9.3:1. It's higher, but not a super large amount or anything. A VW EA888 doesn't have a ball bearing turbo, and it doesn't have some super advanced turbine or compressor setup. It's a very cheap engine in modern terms.

So, what's the secret?

[ptuomov]

I don’t know what’s the secret. But I’d say that the variable valve timing degrees of freedom have increased. I also suspect that valve and ignition timing control strategies are now much better in reducing turbo lag than they were in the 1990’s.

[ptuomov]

Now I don’t want to overstate the case. We stopped on the upsizing of intake side piping when we got the compressor to intake manifold pressure drop to that 10 kPa (from memory it ended up at 1.4psi).

[Kevin Johnson]

...
So, what's the secret?

Looked at some eBay listings and the stock intercooler piping setup for the VW is substantially shorter and more direct than for the Supra.

[ptuomov]

...
So, what's the secret?

Looked at some eBay listings and the stock intercooler piping setup for the VW is substantially shorter and more direct than for the Supra.

I think LoganD is 100% right that the car factories have focused a lot on reducing the unnecessary pressure loss in the intake boost piping.

[BLSTIC]

How much inertia does the vw turbo have compared to the 2JZ primary turbo? Compared to the power it's capable of supporting and the engine driving it?

What's the throttle mapping like on the 2JZ compared to the VW (IIRC the 2JZ were electronic throttle with a cable backup, somehow)? My NCP10 Echo had great throttle response (if gutless, but what it had it delivered instantly), but the later Yaris with a bigger-but-otherwise-identical motor and an electronic throttle is an unresponsive mess

(I don't actually know, just posing reasonable questions)

[LoganD]

The secret is that they worked hard to reduce two volumes: the volume between the exhaust valve and the turbine, and the volume between the compressor outlet and the intake valve. Turbines operate on pressure drop, so when you open the throttle you want it to take as few engine cycles as possible to increase the exhaust backpressure pre-turbine. Similarly, you want as little volume that the compressor needs to fill so that it takes as few compressor revolutions as possible to achieve a pressure target. This is why the turbines are mounted directly to the head now, and this is why air to water charge air coolers are so popular.

This is really basic physics people, PV = mRT. You reduce volume (V) and then it takes less mass (m) to reach a desired pressure (P). Go look at a compressor map, it's always rated in mass flow, or mass per unit time. You reduce that mass requirement, it takes less time.

There have been aerodynamic improvements in both turbines and compressors in the last 20 years, but they aren't as huge as you'd imagine unless you pay for fully machined compressor/turbine wheels. You're limited on what you can do with wheel shape by mass production methods on low end turbocharger systems, yet they get great throttle response. Reducing pre-turbine exhaust volume and post-compressor induction volume is BY FAR the best way to improve turbocharged engine response with a given turbocharger.

[n2xlr8n]

Drive a turbocharged car from 1995 and drive one from 2019 and you tell me which has better "throttle response". Most of that improvement is due to intake volume reductions.

This is very, very simple volume flow stuff.

Respectfully, I'd say the improved boost response of modern engines comes primarily from variable camshaft timing.

On the other hand, I personally like small, short exhaust tubing leading into my turbo and the shortest section of boost piping possible.

[ptuomov]

I agree that there’s been a lot of focus on reducing the pressure loss and reducing volume on the boost side. But BMW still uses front mounted air to air intercoolers for many models despite that greatly increasing the required volume compared to air to coolant intercoolers.

The exhaust changes have been dramatic. Now, the exhaust volumes are much smaller and the flow and pulses seem to be better directed towards the turbine. This I think is clearly visible when comparing the 1980’s Porsche and modern BMW turbo engines.

So yes they’re doing it and it has to help, but the question is about the magnitudes.

[LoganD]

Drive a turbocharged car from 1995 and drive one from 2019 and you tell me which has better "throttle response". Most of that improvement is due to intake volume reductions.

This is very, very simple volume flow stuff.

Respectfully, I'd say the improved boost response of modern engines comes primarily from variable camshaft timing.

On the other hand, I personally like small, short exhaust tubing leading into my turbo and the shortest section of boost piping possible.

I mean you can have your opinion, but it's wrong. I'm not going to continue to argue about this though, I do this for a living and if people aren't going to listen to facts then there's nothing I can do. I'll say it again, I literally design OEM engines for a living.

I agree that there’s been a lot of focus on reducing the pressure loss and reducing volume on the boost side. But BMW still uses front mounted air to air intercoolers for many models despite that greatly increasing the required volume compared to air to coolant intercoolers.

The exhaust changes have been dramatic. Now, the exhaust volumes are much smaller and the flow and pulses seem to be better directed towards the turbine. This I think is clearly visible when comparing the 1980’s Porsche and modern BMW turbo engines.

So yes they’re doing it and it has to help, but the question is about the magnitudes.

BMW also have engines where the turbine isn't mounted directly to the cylinder head. The reason BMW have to do this is that their engine development budget is MUCH smaller than say, VW, and so they can't make a different intake manifold and turbine housing for every vehicle the engine needs to package in. The only reason they run air to air intercoolers on some of the engines is for COST REASONS.

Want proof? Look at the BMW M3 engine, one of their flagship high performance models, it's got an air to water intercooler. When it counts and they can spend the money, they run the air to water. M5? Air to water.

[n2xlr8n]

I mean you can have your opinion, but it's wrong. I'm not going to continue to argue about this though, I do this for a living and if people aren't going to listen to facts then there's nothing I can do. I'll say it again, I literally design OEM engines for a living.

I'm not arguing, for the record.

I'll agree that an OEM engineer is far more educated than I regarding this subject.

[Kevin Johnson]

This is why the turbines are mounted directly to the head now, and this is why air to water charge air coolers are so popular.

Yeah, I saw that in the newer VW castings but that engine class covers a fair period of time. The contemporary manifolds were fairly similar and then VW moved to the integrated turbine in the manifold casting and finally the integrated head and manifold. The duct work is what stood out to me without being too unfair to Toyota.

The hysteresis or memory of the system would relate to what is called lag or transient response, I guess.

Actually, I was more interested in the concave ribs Toyota put in the Supra tank ends. Looks very deliberate.

[lewy-d]

What OE engines have you designed?

[ptuomov]

BMW also have engines where the turbine isn't mounted directly to the cylinder head. The reason BMW have to do this is that their engine development budget is MUCH smaller than say, VW, and so they can't make a different intake manifold and turbine housing for every vehicle the engine needs to package in. The only reason they run air to air intercoolers on some of the engines is for COST REASONS.

Want proof? Look at the BMW M3 engine, one of their flagship high performance models, it's got an air to water intercooler. When it counts and they can spend the money, they run the air to water. M5? Air to water.

Those Behr intercoolers on M5 are great.

I think BMW M5 also has a complete pulse separation on the exhaust side. The exhaust manifold has more volume than some other hot-in-the-V engines, but I believe keeping the pulses separate more than compensates for the additional volume.

Other than a couple of exotic manifold systems, minimum volume log exhaust manifolds are the standard now -- if the housing isn't cast to the head.