Time to go Stage II!

[turbofabricator]

Donnie......I'm looking forward to your fabrication of manifold and headers. On the header issue.......remember, that there are guys runnning 200+ mph using mildly ported cast iron Chevy truck manifolds. There just isn't much in power gains going crazy on header development. Anything you build will still be just a log manifold. It ends up dead ending into the turbine. We've got guys on here runnning in the 9's with the crap pile stock headers. I would have NEVER thought that was even possible 20 years ago.
I really do look forward to your build, though. If nothing else, they'll be crazy cool looking and surely won't hurt power. Pictures....LOTS of pictures. Your thoughts?

 

[Alky V6]

Donnie......I'm looking forward to your fabrication of manifold and headers. On the header issue.......remember, that there are guys runnning 200+ mph using mildly ported cast iron Chevy truck manifolds. There just isn't much in power gains going crazy on header development. Anything you build will still be just a log manifold. It ends up dead ending into the turbine. We've got guys on here runnning in the 9's with the crap pile stock headers. I would have NEVER thought that was even possible 20 years ago.
I really do look forward to your build, though. If nothing else, they'll be crazy cool looking and surely won't hurt power. Pictures....LOTS of pictures. Your thoughts?

I've gone over my thinking on the subject of pulse tuning with turbocharged engines enough times that I'm not going to go into it again on this thread, unless someone is really interested in getting into it. The sim is showing gains by going with a tuned system compared to a simpler header that I just can't ignore. The same sort of thing the sim teased me with when I put the Stage I configuration together. All I can offer is that the tuned system on my Stage I project sure didn't hurt anything, and wildly surpassed all expectations, including those of the sim. I'm going to follow the same line of thought with the Stage II project, and we'll see what we end up with. At the very least, like you stated, it should be an eye catcher.
Pictures? Of course!

 

[turbofabricator]

How is the pulse "tuned" when it crashes into a spinning turbine that has it's own frequency. Each turbine blade has a resonance different from the others. I've always wondered how we can possibly calculate the pulse tuning when it crashes into a turbine. That is probably why a helicopter can fly when on paper its a "bird blender". I see some real high end calcualtions done everyday in the commercial aviation field that requires big Titainium straps to "fix" that the computer models were WAY on. Hell, were almost five years behind because some of the most powerful computers in the entire world (and thier programmers, too) really screwed the pooch. Not trying to talk you outta doing, of course. I like to see innovation. I hate going to Buick events and every car there looks like the one next to them. I also love discussing the pros/cons, why and why nots of doing what we do. I've been out in the shop with buddies until 3am discussing exhaust valve opening timing. Only to feel dumber than when we started. And then....sometimes things work better when they shouldn't.

 

[Alky V6]

How is the pulse "tuned" when it crashes into a spinning turbine that has it's own frequency. Each turbine blade has a resonance different from the others. I've always wondered how we can possibly calculate the pulse tuning when it crashes into a turbine. That is probably why a helicopter can fly when on paper its a "bird blender". I see some real high end calcualtions done everyday in the commercial aviation field that requires big Titainium straps to "fix" that the computer models were WAY on. Hell, were almost five years behind because some of the most powerful computers in the entire world (and thier programmers, too) really screwed the pooch. Not trying to talk you outta doing, of course. I like to see innovation. I hate going to Buick events and every car there looks like the one next to them. I also love discussing the pros/cons, why and why nots of doing what we do. I've been out in the shop with buddies until 3am discussing exhaust valve opening timing. Only to feel dumber than when we started. And then....sometimes things work better when they shouldn't.

This is exactly what intrigues me about working with the sim. I'm well aware that chances are real good that a sim cannot account for every variable involved in the gas flow of a 4 stroke engine, let alone a turbocharged engine. Especially, the level of sims that are affordable to the general public. But, when you test a sim and the real world result far surpasses the predictions of the sim, you have to sit back and wonder, can this sort of sim under-estimation be repeated?
When I think about pressure wave tuning with a turbocharged engine, I really don't think much further than the turbine housing. You're right in that the turbine housing becomes a major restriction to flow, but what about the space volume of all the other piping joined together at the turbine housing? We have 6 lengths of tubing. Two sets of three tubes joining to one short collector per set, and then Y-ing together at the turbine housing. An exhaust valve opens and pressure is quickly introduced into one of the tubes. What happens next?

 

[Alky V6]

A column of exhaust gases shooting down an exhaust primary tube has inertia. We first have to understand that exhaust gases have weight. And anything of weight that is moving has inertia associated with it. This is the basis of the principle of inertia tuning.
Now, what if the primary tube already has a pressure in it before the exhaust valve opens? What primary tube on the surface of the earth doesn't have some pressure already in it? Even with the engine not running.

 

[turbobitt]

This is exactly what intrigues me about working with the sim. I'm well aware that chances are real good that a sim cannot account for every variable involved in the gas flow of a 4 stroke engine. Especially the level of sims that are affordable to the general public. But, when you test a sim and the real world result far surpasses the predictions of the sim, you have to sit back and wonder, can this sort of sim under-estimation be repeated?
When I think about pressure wave tuning with a turbocharged engine, I really don't think much further than the turbine housing. You're right in that the turbine housing becomes a major restriction to flow, but what about the space volume of all the other piping joined together at the turbine housing? We have 6 lengths of tubing. Two sets of three tubes joining to one short collector per set, and then Y-ing together at the turbine housing. An exhaust valve opens and pressure is quickly introduced into one of the tubes. What happens next?

Pressure pulse tunning has been the subject of debate in Don's last few threads. Although I don't agree his thoughts on this I would still like to "recalibrate" my thoughts on the subject to say that pressure pulse tunning would be more effective on the intake side. Still think gains in most turbo applications would be minimal.

In a high RPM application such a this build, I would think not to discourage the thought of pressure pulse tunning since it may be a little more benificail for 9000+ RPM's, but again thinking of the intake side for high speed cylinder fill.

Allan G.

 

[Alky V6]

What will start the exhaust gases flowing down the primary tube is the pressure differential between the cylinder and the exhaust system. I don't care if the exhaust system is at atmospheric pressure or 70 psi. When the exhaust valve opens, the exhaust gases ARE going to be moving out of the higher pressure cylinder and down the exhaust primary tube. The exhaust gases will be moving down that primary tube at a certain velocity. The weight of the exhaust gases and the velocity of the column of exhaust gases traveling down the primary tube will give it a certain inertia value.

 

[Alky V6]

Pressure pulse tunning has been the subject of debate in Don's last few threads. Although I don't agree his thoughts on this I would still like to "recalibrate" my thoughts on the subject to say that pressure pulse tunning would be more effective on the intake side. Still think gains in most turbo applications would be minimal.

In a high RPM application such a this build, I would think not to discourage the thought of pressure pulse tunning since it may be a little more benificail for 9000+ RPM's, but again thinking of the intake side for high speed cylinder fill.

Allan G.

Most people will argue that because of the high pressures in the exhaust system commonly associated with turbocharging, pressure pulse tuning doesn't occur in the exhaust system. Yet, Allen is saying that pressure pulse tuning on the intake side is possible. Even with the intake manifold at high boost pressures.
Why would pressure pulse tuning be able to occur in a high pressure intake manifold, yet not occur in a high pressure exhaust system?

 

[Alky V6]

What will start the exhaust gases flowing down the primary tube is the pressure differential between the cylinder and the exhaust system. I don't care if the exhaust system is at atmospheric pressure or 70 psi. When the exhaust valve opens, the exhaust gases ARE going to be moving out of the higher pressure cylinder and down the exhaust primary tube. The exhaust gases will be moving down that primary tube at a certain velocity. The weight of the exhaust gases and the velocity of the column of exhaust gases traveling down the primary tube will give it a certain inertia value.

When the exhaust pressure column is near done exiting the cylinder, the inertia of the just expelled exhaust gases column will create a sucking action at the rear of the column. That is going to happen. There is no way to argue around that. What sort of pressure range that sucking action occurs within will be higher in a turbocharged application compared to a n/a application, but none the less, it will occur. The reason for picking out a certain primary tube diameter and length is to make sure that sucking action occurs at the right time in the overlap timing of the camshaft.
Remember, in my configuration, I am going to have more average intake boost pressure to average exhaust back pressure. When that sucking action in the primary pipe is timed to occur at the exhaust valve during overlap, I'm assured that the pressure at the exhaust valve during the sucking action will be below the pressure of the intake charge beginning to enter the cylinder. This will translate into better evacuation of exhaust gases still trapped in the combustion chamber during overlap, and ultimately, improved VE.

 

[Alky V6]

That covers inertia tuning. Is inertia tuning the same as resonance wave tuning? Or, is resonance wave tuning another thing separate from and on top of inertia tuning?

 

[Alky V6]

When a reflective wave is generated and travels back up the primary tubing, where and when is that reflective wave generated? At the end of the primary tube? In the collector? At the end of the collector? At the turbine wheel? After the turbine wheel? At the end of the exhaust dump pipe?

 

[Alky V6]

Has anyone ever held their hand over the end of an exhaust pipe on a turbocharged engine while it was running and felt the pulsing of the exhaust? Did the turbo cancel out all the pulsing in the exhaust system?
I don't know about you guys, but the pulsing occurring at the end of my exhaust system is very pronounced. The box I use to collect the fumes vibrates from the pulsing.
Where there is vibration, there is pressure pulsing.

 

[Alky V6]

Ken, ya got me goin'.

 

[norbs]

This is thread way above my technical skills, however I do agree we have pulses on the exhaust at the tail pipe...so Donnie might have some merit on pulse tuning..

 

[Alky V6]

Before I go any further, I'll let everyone know that I'm going with exhaust header dimensions that the sim favors. That doesn't necessarily mean that the primaries are going to be long like the Stage I headers were. In fact, the sim is favoring short primaries with this build.
There's about a 60hp difference between using long tube and short tube primaries.

 

[Alky V6]

The sim is giving me the impression that the exhaust header system itself is the restriction. The sim wants the exhaust header system out of the way so that the cylinder can simply blow down as quickly as possible, minimizing pumping losses.
That's interesting when the exhaust header piping becomes more of an exhaust restriction than the turbine wheel/housing.

 

[turbobitt]

The sim is giving me the impression that the exhaust header system itself is the restriction. The sim wants the exhaust header system out of the way so that the cylinder can simply blow down as quickly as possible, minimizing pumping losses.
That's interesting when the exhaust header piping becomes more of an exhaust restriction than the turbine wheel/housing.

This is where the sim falls short. The header will act as an expansion chamber. Changing this expansion chamber can greatly effect the energy input to the turbine. I don't think the sim will account for this. I think there is power in keeping the primary tubes on the smaller side so that the turbine can capture as much energy as possible. Key is controling velocity without sacrificing flow. If I had my choice, I would make my primary tubes smaller for my application.



Allan G.

 

[Alky V6]

Key is controling velocity without sacrificing flow. If I had my choice, I would make my primary tubes smaller for my application.



Allan G.

The sim is showing that you are correct. There is a balancing act between keeping exhaust velocity up, but not so high that the exhaust system becomes the major restriction in the system. Even though the primaries are shorter, the ID and exact length is still touchy. And, surprisingly the collector length and diameter is touchy, too.
The Buick Power Source book suggests, for Stage II turbocharged road racing and oval track racing, a primary tube ID of 1.875" and a length as short as possible. Also, the collector mating to the turbocharger should be as short as possible. No suggested diameter was given for the collector. The horsepower levels for those applications around that time period were around 700-800 hp.
Now consider that we're planning an application where the target hp level will be 1400-1500 hp. Should the primary tube ID still be 1.875"? I don't think so. Plus, the sim shows that 1.875" would begin to choke the engine. My application will be taking advantage of crossover in the combustion chamber, so piping size becomes even more critical.

 

[Alky V6]

For a target 1400-1500 hp, primary tube ID should be at least 2.0". Even as large as 2.125".

 

[Alky V6]

Here's an idea. Treat the exhaust primary and collector tubing as one long, stepped primary pipe.