Cost of turbocharging

[Killerbee]

: 110% to 120% drive pressure to boost pressure ratios once the turbo has spooled up. .

IOW... 2.1-2.2 drive pressure ratio? IIRC they are 2.5-3.5 stock.

if so much restriction was removed, I might have expected bigger EGT reduction would be observed.

Back to your vane angles...I have never seen 40-50 to produce 28 psi boost (stock vehicle).

is it safe to say, with redesign vane position can't really be compared apples-apples? I didn't think of that before asking the question.

 

[Fingers]

Clarification:

1.1:1 - 1.2:1 drive to boost ratios after turbo is spooled with the new vanes on my truck with my tune. Stock turbo was 1.4:1 -1.6:1 same truck, same tune. This varies a huge amount from truck to truck depending on tune, add ons, so on and so forth. For instance, the stock tune keeps the drive pressure high while in highway cruise by commanding a lot more vane and boost than is needed.

One reason I have not pushed these is that to get the best from them, you have to tune towards their advantages. And I don't have all those bases covered yet.



Tip in pressures are about the same so far. I'm working on that, but it is a harder nut to crack.

 

[Killerbee]

Clarification:

1.1:1 - 1.2:1 drive to boost ratios after turbo is spooled with the new vanes on my truck with my tune. Stock turbo was 1.4:1 -1.6:1 same truck, same tune.

was all that 3:1 data from PUSU incorrect?
(45 psi for 15 psi boost)

what compressor side mods do you have?

 

[Fingers]

Tuning.

Stock tune, which I haven't run in......a long time, calls for more boost than the exhaust can support in the cruising RPM ranges. So the commanded vane position is way closed stock and the drive pressures get out of hand. JMO. Using an A/F PID in EFI as a guide, I have turned the boost way down for most of the cruising range.

As I posted before, unless there is fuel burning in the exhaust pipe, turbo charging does not produce a net gain.

But...what do I know.

 

[WolfLMM]

Has this been done with any reportable results

Stainless Steel. Wrapping is a waste IMO. Headers and up pipes need to be built from material that does not aborb/conduct heat well.

 

[Fingers]

And what would that be? Unobtainium?

Everything absorbs heat. Some faster than others, true. But they all conduct. However, if you slow down or stop the dissipation on the outside, you also slow and/or stop the absorption on the inside.

Insulating the outside WILL keep more heat in the exhaust. Now you have to make the pipes out of something that can tolerate the higher temps...Stainless is the only reasonable way to go.

 

[ROGUE GTS]

And what would that be? Unobtainium?

Everything absorbs heat. Some faster than others, true. But they all conduct. However, if you slow down or stop the dissipation on the outside, you also slow and/or stop the absorption on the inside.

Insulating the outside WILL keep more heat in the exhaust. Now you have to make the pipes out of something that can tolerate the higher temps...Stainless is the only reasonable way to go.

With steel prices these days the more exotic metals (inconel, titanium, etc) are becoming more of a viable option.

I can't even get a quote on stainless material that is good for more than 3 days.

 

[Killerbee]

Clarification:

1.1:1 - 1.2:1 drive to boost ratios after turbo is spooled with the new vanes on my truck with my tune. Stock turbo was 1.4:1 -1.6:1 same truck, same tune. This varies a huge amount from truck to truck depending on tune, add ons, so on and so forth. .

still unable to really digest this. At 26 psi (40 psi MAP) the compressor on a stock LLY (stock intake) requires 150 HP or thereabouts from the turbine.

The best drive ratios I have ever heard of don't approach the values you are reporting Jon. Just thinking.

 

[ROGUE GTS]

still unable to really digest this. At 26 psi (40 psi MAP) the compressor on a stock LLY (stock intake) requires 150 HP or thereabouts from the turbine.

The best drive ratios I have ever heard of don't approach the values you are reporting Jon. Just thinking.

Really? Big turbo stuff regularly gets under 1:1 pressure ratio on the turbine vs compressor.

Just gotta let it breathe.

 

[Brayden]

Housings that will get you close to 1:1 are going to be very laggy.

 

[dmaxtruck]

I'll bite!

First, the "Free Lunch" only happens when there is still fuel burning in the exhaust stream. If the combustion process is done when the exhaust valve opens, the engine has to do all the work to push the gases out of the exhaust tube.

However, if there is still flame in the charge, the engine only has to push the pre-expanded portion into the pipe.

Food for thought...:cool2:

They need to keep the turbo spooled at all times, so the placed an additional mechanical fuel injector directly in the exhaust manifold that would dump raw gas in when the let off the throttle Of course there was somthing like a 4 foot flame out the pipe around turns but it worked! Keeped the turbo spooled (and exhaust glowing!)They dominated with those cars! Cool stuff!

1/3rd to 1/2 of the fuels caloric value typically exits as waste heat out the exhaust.

The turbine is a device that does a heat/velocity-to-work conversion with lousy efficiency. The exhaust temp and pressure on the other side of the turbine is less than on the inlet. That means the potential energy of hot fast moving exhaust, which must exist with or without a turbo, is being used. It is a partial recovery of energy that would otherwise go straight to the atmosphere as heat.

It is analogous to hydro dams. The vertical and gravitational movement of water thru turbines makes for work that can used to make electricity.

The thread may exploit what things can make this process of work conversion more efficient (turbine or compressor), or to bring light to parasitic losses that can be eliminated...this has no impact on process efficiency, but rather reduces load, IMO that is the best way to improve the process.

Ok so basically what we're looking at here is making the difference between the two sides of the turbo greater, as the greater the difference between the two in terms of heat means a greater potential energy.

Assuming everything you've said is true it would seem to me that to get greater potential energy from the turbine side you would want extremely hot compressed air coming out of the exhaust manifolds and as big of an exhaust tube as possible post turbine. The bigger the difference in air density before/after turbine is better as the compressed air wants to go back to natural density and the only place to expand is post turbine. Similarly, the bigger the difference in temperature before/after turbine is better as the cooler air post turbine will want to absorb the excess heat coming out of the manifolds.

Assuming all the above is true, the bottom line is that a free flowing and very cool exhaust combined with highly compressed and really hot air coming out of the manifolds will yield a greater potential energy for the turbine to convert.

Is that basically what you guys are saying here? I don't know any of this to be true or false for myself I'm just trying to logically follow your arguments to their conclusion.

 

[Killerbee]

its seems to me, if you can reduce backpressure, as has been discussed, then to maintain the same boost, you have also increased turbine efficiency, and created a larger temp differential across the turbine.

I say this is necessarily true, because if no compressor side changes are made, the shaft experiences the same exact stress/HP load, as this is defined by the cold side mechanism...independent of the hot side in all respects.

That work must come from the turbine. If it is not coming from backpressure, then it is coming from heat, and Jon has created a bigger free lunch.

Is it safe to say, that the vane/turbine configuration in any VVT, is a compromise that requires the designer to determine what area of boost he wants to optimize?

 

[Fingers]

Just throwing this out there.

The turbine is a momentum converter and generates it's power from the speed change in the exhaust flow. Back pressure is parasitic. More akin to drag on a plane wing. You don't strictly have to have it, though you can't get away from it.

The restriction created by the vanes and the power generated by the turbine are not directly related. For instance, you can greatly restrict flow with the vanes and generate almost no power.

Ideally, and this is just my opinion, the vanes should be used for two thing and otherwise be as invisible to the flow as possible.

One is to spool the turbine when the exhaust housing can not support the situation. This is way less efficient than the housing, but an acceptable trade off for the extended range.

The other is to trim the flow reduce boost. Actually, I think a waste gate is better for this function since it does not generate back pressure in the process.

 

[McRat]

Dunno, both velocity and mass of the gas stream that drives the tubine blades is assisted by backpressure. The denser the gas, the more "wallop" it has and the faster a sound wave can move (pulse).

What it totally unnecessary is heat, but it's the only way we have of generating backpressure. If backpressure was zero, the turbine would only rotate because the compressor wheel was restrictiong intake flow.

 

[Killerbee]

Just throwing this out there.

The turbine is a momentum converter and generates it's power from the speed change in the exhaust flow. Back pressure is parasitic. More akin to drag on a plane wing. You don't strictly have to have it, though you can't get away from it.

The restriction created by the vanes and the power generated by the turbine are not directly related. For instance, you can greatly restrict flow with the vanes and generate almost no power.

Ideally, and this is just my opinion, the vanes should be used for two thing and otherwise be as invisible to the flow as possible.

One is to spool the turbine when the exhaust housing can not support the situation. This is way less efficient than the housing, but an acceptable trade off for the extended range.

The other is to trim the flow reduce boost. Actually, I think a waste gate is better for this function since it does not generate back pressure in the process.

This is saying what I wanted to say, or was leading up to. I agree. I do believe there is a lot of merit in manufacturing a VVT with a wastegate. IMO this would solve several issues inherent in electronic closed loop feedback compression.

 

[Killerbee]

just wondering Jon if you have an opinion, if the VATN stocker is optimized for a specific range of boost, or maybe better, a specific vane angle range?

This is getting useful now.

 

[Fingers]

Dunno, both velocity and mass of the gas stream that drives the tubine blades is assisted by backpressure. The denser the gas, the more "wallop" it has and the faster a sound wave can move (pulse).

What it totally unnecessary is heat, but it's the only way we have of generating backpressure. If backpressure was zero, the turbine would only rotate because the compressor wheel was restrictiong intake flow.

The mass of the exhaust flow is fixed.

Velocity and pressure trade off with each other. The faster the flow, the less pressure and vice versa with fixed mass.

Pressure does not drive the turbine. Flow does. Pressure is more due to restrictions in the system. Think intakes for a second. Ported heads require less boost to flow the same mass.

Heat is what expands the gasses. At any given pressure, more heat means more velocity. Reducing the pressure and keeping the same temp means more velocity too.

 

[Fingers]

just wondering Jon if you have an opinion, if the VATN stocker is optimized for a specific range of boost, or maybe better, a specific vane angle range?

This is getting useful now.

Boost is probably the wrong metric. I think mass flow and I don't have good number for that though I have seen the turbo "turn on" rather well in certain ranges. Guess I will have to look more closely at it.

 

[WolfLMM]

And what would that be? Unobtainium?

Everything absorbs heat. Some faster than others, true. But they all conduct. However, if you slow down or stop the dissipation on the outside, you also slow and/or stop the absorption on the inside.

Insulating the outside WILL keep more heat in the exhaust. Now you have to make the pipes out of something that can tolerate the higher temps...Stainless is the only reasonable way to go.

Not sure how to take that. I said WELL. But I think you know what I meant. Inconel is a good option but there are better options. Something that wrapping will never achieve. Wrapping may help keep heat in, but what happens when you melt the manifold. Material upgrades are neccesary A low thermal conductivity material can be used to form the inner wall or whole manifold/pipe. Which can provide a uniform heat flux boundary condition and good insulation on the wall to prevent heat loss from the Inside/hole/channel to the outside ambient. Like I said before you need a manifold that doesnt conduct heat WELL. Sometimes you have to look outside the automotive industry to find new ideas/materials.

 

[WolfLMM]

But, It takes pressure to generate flow. The more pressure in the system the more energy you have to drive the turbine(depends on how you use it). It is a neccesary evil. Everybody here knows that Im sure