Aerochargers TT more testing
- Thread starter DDozier
- Start date
People who move in to the flight paths don't get to complain about the constant airplane noise, they shouldn't be able to with our race car tracks. If it bothers you don't live there!
Actually as the diameter of exhaust gets smaller, the exhaust will be hotter and moving faster. This is ideal for getting a great cylinder fill event before/during boost is coming on, if the camshaft is up to the task.
The ideal exhaust system would start out small diameter and gradually open to maintain a high exhaust gas velocity with as little pressure as possible behind the turbocharger.
So for pretend fictional example, if I had a pressure sensor in the exhaust downpipe, I would want it to read as close to atmospheric as possible (or even less), which might be possible anywhere from 1.25" to 4"+ diameter exhaust plumbing while between 900 and 3000rpm. The 1.25" plumbing will give a better cylinder fill, and thus more low end torque in that range. The same concept applies to naturally aspirated engines, who's exhaust systems are exposed to the same exact atmosphere. (Also, as a side note, the shape and material of the exhaust, for reasons particular to sound frequency, may also have an effect on cylinder fill in N/A applications where the turbine tends to block such effects) However, once 3000rpm is reached (or whenever the pressure begins to climb above atmosphere) we would want the diameter to increase to keep the pressure minimal while maintaining exhaust velocity.
A device such as a cut-out that moves to open position based on a 1psi~ set diaphragm watching the downpipe would probably work... but the potential for gain would be offset by the additional complexity (MORE moving parts in the exhaust system?) it depends on the application.
Except they lived there first lol
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I'm aware of most of this but we are talking about variable vane turbos. That changes things. Also when I say lower back pressure producing more power I'm talking about upper end power. You said a lot here but I guess I am unsure of your point. I'm just saying perhaps some power is being given up at the same PSI in order to keep it quiet. But I don't even know what the exhaust is... Hence my question.
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well of course it would be interesting if we knew what the pressure is in our exhaust systems, but few people monitor this detail or stand to gain little more than an idea. Your guess is as good as anybodys what the real pressure differential is that exists along a length of tube, after or before any engine without measuring it directly at enough points.
Look in Dave's gallery for a pic. I remember seeing one there, or in CL65 Captains gallery. It was an x-pipe design with bullet cats... but that may have been replaced now.
The variable vane turbos don't change anything. Vane position is dictated by a controller. Reducing exhaust backpressure downstream of the turbos is beneficial to these, like any other system. Inertial gas flow downstream of the turbo has little impact on the impeller... at least on my testing with an Aerodyne.
Dave
the exhaust path is quite simple on my setup. 2" OEM Double Walled Headers, to 2" mandrel bent connecting pipes, to 2" turbo inlet flange, to 2.5" turbo outlet flange, to 2.5" in/out hiflo cats, to 2.5" X pipe, to 2.5" in/out 12" straight through SS Muffler, to 2.5" to 3.5" polished stainless tips.
The attached pics are of the Wailing Banshee setup, it did not have an X pipe or mufflers, sounded cool but would have got me kicked off every track with sound restrictions. The fabrication picture is easier to see what was going on with the routing of the pipes as the ceramic coating makes the picture harder to see what the pipes are doing.
As far as back pressure or lack of it effecting the performance of the system, the exhaust change from the original design to the final design did not require any tuning changes and the new design resulted in a +/- 2 whp change at any point in the final pull on the dyno and could just as likely been a result of being on the dyno on different days. The replacement exhaust is nearly as free flowing as the no-muffler setup was. The mufflers used are a straight through design with very little restriction. The added x-pipe and mufflers combined to offer the large reduction in sound. The change from the first design to the 2nd design had little effect on performance with a +/- 2whp change in the dyno run, and that could just as easily been the difference in day the dyno runs were done on. The X pipe and the mufflers combine to reduce the overall sound level of the system but the mufflers are straight through in design and offer very little restriction vs just having a 2.5" pipe in place. If you were to remove the cats then the power would likely increase but so would the sound level.
Final version with X pipe and mufflers:
Dave
The attached pics are of the Wailing Banshee setup, it did not have an X pipe or mufflers, sounded cool but would have got me kicked off every track with sound restrictions. The fabrication picture is easier to see what was going on with the routing of the pipes as the ceramic coating makes the picture harder to see what the pipes are doing.
As far as back pressure or lack of it effecting the performance of the system, the exhaust change from the original design to the final design did not require any tuning changes and the new design resulted in a +/- 2 whp change at any point in the final pull on the dyno and could just as likely been a result of being on the dyno on different days. The replacement exhaust is nearly as free flowing as the no-muffler setup was. The mufflers used are a straight through design with very little restriction. The added x-pipe and mufflers combined to offer the large reduction in sound. The change from the first design to the 2nd design had little effect on performance with a +/- 2whp change in the dyno run, and that could just as easily been the difference in day the dyno runs were done on. The X pipe and the mufflers combine to reduce the overall sound level of the system but the mufflers are straight through in design and offer very little restriction vs just having a 2.5" pipe in place. If you were to remove the cats then the power would likely increase but so would the sound level.
Final version with X pipe and mufflers:
Dave
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I just noticed you have it all wrapped. Hows the wrap holding up? how do the plumbing manage it? Does your car see rain? Usually wet wrap on exhaust plumbing is a bad combo. So I am wondering how you manage that... maybe just dont drive it when it rains ? 
Intensely curious because I myself have a 100ft roll of pure crushed lava rock wrap... and I am debating... using it. Only thing stopping me is rain/fear of rust.
Intensely curious because I myself have a 100ft roll of pure crushed lava rock wrap... and I am debating... using it. Only thing stopping me is rain/fear of rust.
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Considering each turbo weighs 15lbs and the mounting system is about 5lbs, mufflers, pipes, cats, tips are about another 15-20 total, intercooler dry is 2.5lbs, heat exchanger 1.5 lbs, pump, brackets, hoses, reservoir are another 10lbs. These are just guesses at the weight but if you use these numbers and offset them with the OEM exhaust and cats, I would say the net difference is something like 30lbs. I do not really know but I do know that my car corner balanced right at 3050lbs with 5/8 tank of gas, bilstein shocks, Tarox BBK, 17/18 wheels, 235/275 NT01, Twin Turbo, Custom Gauge Cluster, and all OEM interior and exterior body parts other than the front spare tire and holder.
Dave
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I just noticed you have it all wrapped. Hows the wrap holding up? how do the plumbing manage it? Does your car see rain? Usually wet wrap on exhaust plumbing is a bad combo. So I am wondering how you manage that... maybe just dont drive it when it rains ?
Intensely curious because I myself have a 100ft roll of pure crushed lava rock wrap... and I am debating... using it. Only thing stopping me is rain/fear of rust.
The pipe is 304 stainless and is ceramic coated inside and out, then wrapped. The car only sees rain on track days that rain. In the beginning the wrap would stink like crazy anytime it got wet and the exhaust was hot but after about 10 times of getting wet and hot that has gone away. I am not sure the wrap is really doing much since the pipe is coated but considering my polished stainless tips are anything but shiny from the intense heat after many track sessions I am sure those wrapped mid-pipes are getting plenty hot and if the wrap had any moisture in it after a track session and cool down in the pits it would be gone.
Dave
You going turbo, turbo?
Probably. If dave ever writes me back lol.
Dave Dozier (too many Daves here) I sent you an email. Did you get it?
I'm sure it will be worth it when Dave releases his kit!
The weight difference in this system vs. OEM is pretty even when it's all said and done. Just finished building my system that is similar to Dave's. I'm running the smaller 53 frame Aerodyne's from the original Corky Bell system. I've got Dave's brand spanking new intercooler mounted in the Intake Manifold. As my turbos are a wee bit smaller than his, I'm able to plumb them straight to a muffler and use the muffler hangers to hold the system up. By removing the spare tire (I'm running a BBK on 17's/18's so there is no need for a spare) I've broken even on the weight. I'm also adding a flex fuel sensor so I will have a tune for pump 91 and another for E85. If I combine the fuels, the sensor will tell the ECU just how much ethanol is in the fuel line and pull back on the tune accordingly. Hoping to finish the tune next week. Anxious to see what we end up with.
I sent an email back today with a few questions for you.
Dave
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I'm sure it will be worth it "IF" Dave releases his kit!
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I am almost as anxious as you are, keep me posted!
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- 17 December 2014
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Dave. Did you ever re dyno on the quicker vane spool setting?
I have not, I should just so I have the data. However, for my use of the car I can not see any benefit to spooling any faster than I am now. I mainly use my car for track days and that means I am almost always above 4k RPM if I am doing it right.
Dave
Dave
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