Turbo BS Thread

I do suppose that even a down stream heat source would slow exiting exhaust down though creating more back pressure... No such thing as a free lunch

 

I already mentioned releasing a burst of compressed air at the turbine for instant spools guys everyone will think that little compressor under the hood is for airing back-up at the end of the trail

 

Haha a pneumatic solenoid valve. That would be funny.

 

The math to test this out isn't too difficult. It's been a quick minute since I last did these calcs. Maybe if I have time I'll make a spreadsheet water vs exhaust gas.

I just take a set mass of exhaust at like 1500F and add a small mass of water that you know will turn to steam. Make a plot of adding water until you can't turn it all to steam. There might be a sweet spot of exhaust to water ratio. Then I get to see if my pressure increased as the exhaust cools and water heats up. There will be a whole bunch of assumptions to start.

Probably assume turbo is running at 15 psi.
Then I get to make a guess of typical turbo back pressure between the head and turbo @15 psi boost.

 

I think a simple water/meth kit would suffice. 200 to maybe 400cc of injection between the head and turbo would do it. Waste water and rust in the remaining exhaust system would be a drawback.

Even an expansion chamber behind the turbo then necked down to the rest of exhaust could be beneficial. Like how 2 stroke motors are set up. Put a 4-5” ‘test pipe’ on your 2.5-3” exhaust.

 

I do not expect rust would increase at all, after all, combustion of one gallon of gasoline creates CO2 plus about one gallon of H2o, from the chemical reaction of burning fuel. Most of what we see coming out of the tailpipe is water vapor. Also why it's more visible in the cold. The vapor must give off its heat, in order to condense back to visible liquid, and is easier to loose heat in the cold.

 

I don't follow, how does this help?

On a 2-stroke, the exhaust has a chamber that is at a length specific to the target RPM, for peak power.

WARNING: the following is my understanding of how and why a 2-stroke benefits from a tuned pipe! And closes with why I thought it worthy of another long winded message. Please don't ban me for this, as it speaks only to those that do not already know.

On a 2-stroke, after ignition, the exhaust port opens first, and gets the waste gas moving (quickly, almost speed of sound), then the opening of the intake port follows, so both intake and exhaust ports are open, straight across the top of the piston, such that the momentum of the exhaust gas creates a suction, pulling charge mix into the chamber, for the next ignition.

Because the ports open and close directly off piston travel; the exhaust port not only opens first on piston downward travel; but necessarily closes last on the upstroke.

This is where the tuned pipe comes in; the specific distance from port to the echo plate (neck-down) of the pipe. The exhaust enters the pipe as an explosive pulse, this pulse takes time to travel the length of the pipe, until reaching the echo plate where it (mostly)bounces off and reverses direction. The trick here is to adjust the length of the tuned pipe so the the echo arrives at the exhaust port, just before the port closes (intake port is closed here, so no escape across the piston). this is a high pressure wave, focused at the port by the tapered pipe, STUFFING (exhaust?) gasses backward into the chamber at the last second, increasing compression by increasing the volume above the piston.

OK now the most important detail, remember when the piston was down, and both intake and exhaust ports were open straight across the piston? The momentum of the exhaust gasses not only pulls charge mixture thru the carb. and into the chamber, but that charge mixture closely follows the exhaust charge clean across the piston and into the exhaust pipe too. So when the echo comes along to SHOVE gasses back into the closing exhaust port; the exhaust pulse is actually shoving charge mixture back in, not spent exhaust! This is why tuned pipes on a 2-stroke can make such a huge difference, with careful shaping the size and timing of the echo, to dial in more power, at the target RPM.

I hope this is new to someone reading here, as I can remember when I understood this for the first time, for my snowmobile, and how it had previously baffled me why pipes were so oddly shaped, and made such a difference. It also gave me an aaaHaaa moment, because a friend neighbor a model boat, with a 2 stroke engine, and added a tuned pipe with hope to make it faster. But the pipe was too long and could not attach directly to the motor, so he added a 180 deg. u-bend pipe and added the tuned pipe to that. That motor would not run at all; and neither of us had any idea as to why. I now think the pulse was arriving back at the chamber when the piston was at the bottom, and so was back-flowing through the carburetor, and ruining the mixture. We lost touch, so I have no idea if he ever figured it out.

 

Would the AFR's need to be understood as a new "safe" equateable AFR with the moisture added into the mix?

 

I must be thinking of something else. I knew this. Large pipe/chamber off combustion chamber for hot gases to expand into then cool some before off to the smaller diameter exhaust. Maybe more for N/A engines than boosted to help facilitate better flow.

 

If you are talking about injecting water into the exhaust, then no, the addition of water will not impact AFR readings, and there is no impact to combustion.

If you are talking about water/meth injection to the intake, then Yes, sort of. The injection will cool the intake charge, and reduce the potential for pre-ignition. As boost increases, we use a richer mixture to do the same thing, as the additional fuel vaporizing helps to cool intake charge temperatures, and richer mixtures burn cooler. So we use rich mixtures for detonation prevention after a point. With the water injection, the need for rich mixture as anti-detonation, moves farther up the boost and RPM curve.

 

My word of moisture is congruent with steam, as questioned.

Being that this is about injecting "steam" into the exhaust, pre-turbo, which also means pre-WRAF sensor, and if steam is a vapor (with some small amount of moisture) that is then introduced between the head and the sensor, it would then be no different in one simple regard as an exhaust leak is the same space. Which will screw AFR's depending on the severity, as there can be additional air being introduced.

In this theoretical implementation, I foresee the injection of that steam vapor skewing the AFR's. One would only need to test to prove/disprove.

 

Ah. I concur. A long tube/sidewinder type manifold with o2 sensor upstream of water injection is called for. Otherwise would skew what is monitored for AFR.

Or put o2 in manifold and direct inject into the turbine housing.

 

OK, as you begin with a boiler tank of water with air space, so after boiling, the steam will displace that air into the exhaust, at least initially, and the oxygen in that air would knock off the sensor reading.

But after a time, the air would be gone and only steam would follow, till the boiler cools again and ingests more air. boiling water does not release oxygen, so I don't see how the steam alone can cause trouble for the O2 sensor. And after the boiler is under pressure, there is no way for fresh air to enter.

An exhaust leak allows oxygen containing air into the exhaust, which gets read by the sensor.

Combustion creates copious amounts of water vapor (steam) as the result of the chemical reaction; so the sensor can handle (and ignores) steam.

 

I was gonna say that looks like corrosion from sitting with water in the bore.

 

Nearly finished with the down pipe, just a few minor things to square away now

 

Can anyone help me with getting a pin-out for the cluster gauge wiring connectors for a 2020? I decided to install the Boost and AFR gauges in the cluster lens, and now I need to be able to dim them. They are the VLS gauges, so they have a dimming function, if I can feed it a Headlight +12v signal. The only thing I found so far that is alive with the headlights is the green indicator in the cluster. It seems everything else is divided by high or low beam.

With a pin-out for the cluster, I may be able to kill that darn flashing seat-belt reminder too.

Help appreciated!

 

https://www.tacomaworld.com/threads/tapping-the-dash-lights-circuit.413945/page-2

 

Thanks @MadTaco461 , i actually want the pinout for the cluster. I would need to reverse engineer the gauges, and take over control of the LEDs in order to use the trucks dimming function. what i will try first is just using the dimmer already built into the gauge.