Twin charged bp

[Advancedynamix]

That was my remedy for the problems we were having with dual gates on a twin turbo. This was the first of many systems I built like this and it ended up being one of those, "duh, why didn't we think of that sooner" designs. Haha.
Anyway, back on topic. The truth is that most modern turbos, even without an ideal wastegate setup, are less of a restriction than the factory catalytic converter and/or muffler. This is common knowledge to anyone who has installed a higher flow exhaust on their modern turbocharged car or truck. Therefore, in this discussion of exhaust pressure being looked at as lost HP, replacing the muffler with a turbo might work well if you live in Florida. The rest of the 49 states aren't so lucky. :p haha.

[sketchman]

So what was the exhaust pressure pre-turbo vs boost pressure on that one Charlie? I wasn't saying that turbos aren't more efficient, but that it still does take energy to create pressure. How does valve overlap help? Not doubting, just curious.

[TominMO]

Maybe back pressure is a poor way to explain it, but it's such a commonly used word that most can relate. Dynamic compression ratio is affected by the flow rate of the exhaust and intake. At low intake velocity, say partial throttle or low rpm, it's beneficial to have less air exiting the engine. This does affect scavenging, it also affects the tuned pulse and it affects the dynamic compression ratio of the engine. This is part of the theory behind variable valve control and variable exhaust control. Also, it is notable to mention that with increased exhaust velocity and heat the turbine will require less pressure to operate. This is why wastgate placement is very critical in a well designed system. As the turbocharger accelerates, it becomes more efficient and requires less pressure. If timed correctly, this works together with the engines requirements for exhaust flow. Matching the correct turbocharger to the engine is of utmost importance for may reasons.
A turbocharger takes pressure, velocity and heat to do it's job. However, the exhaust energy that is being expelled is being wasted on a naturally aspirated engine. The turbocharger is simply using wasted energy. This is why it is considered free HP. A properly designed turbo system will not make less HP than an N/A engine when not under boost, even when the accelerated air charge is being diverted under partial throttle opening (properly built systems use a diverter valve, not a blow off valve). The Turbochargers compressor also works differently than a screw type supercharger. A turbo is a centrifugal supercharger. This type of charger uses kinetic energy to build boost. This is a much more indirect load than a typical screw pump. The Turbo only becomes a restriction after it has already started increasing the airflow through the engine. There is very little parasitic loss, but Sketch, you are right, there is no transfer of energy that is 100 percent efficient according to the most basic laws of Physics. However, using energy that is otherwise wasted to increase the engines dynamic displacement is as close to free as you can get on this planet, unless you could figure out a way to utilize a solarthermal powered turbine on your engine. Heck, anything is possible.

Above is what Charlie wrote

Below is how it sounds to me:
渦輪增壓器是一種利用內燃機運作所產生的廢氣通过由定子和转子组成的结构驅動之空氣壓縮機（Air-compressor）。與機械增壓器功能相若，兩者都可增加進入內燃機或鍋爐的空氣流量，從而令機器效率提昇。常見用於汽車引擎中，透過利用排出廢氣的熱量及流量，渦輪增壓器能提昇 內燃機的馬力輸出。
一般車用內燃機在加裝增壓器後重量都會增加，所用作克服慣性的能量會上升。因渦輪增壓器大部份時間都是利用引擎排出之廢氣驅動，所以較由引擎曲軸（Crankshaft）驅動之機械增壓器佔優。但因引擎於低轉運作時廢氣流量較低，渦輪增壓器达不到一定 转数表現未如理想，出現渦輪遲滯（Turbo-Lag）現象。但随着科技发展，涡轮增压器已实现过早介入，提高了低轉速时发动机效率。

[sketchman]

lol

[Advancedynamix]

Valve overlap helps with scavenging, plus it's a result of more duration. This all effects the amount of air that the engine can displace. It is true that there is no replacement for displacement, but bore and stoke are only part of the equation once that piston is doing it's thing.
With a typical turbo system, you can't run the same amount of exhaust duration and overlap as you can with an N/A engine because of the pressure between the turbine and exhaust valves. I can't comment on any details of that build because that's not my proprietary information to disclose, but I can say it is possible to run radical N/A cams on a turbocharged engine if you design the system for it. I've worked with Garrett's Air Research department, here in Phoenix, to develop many of the turbines that you can now purchase in the GTX line of turbos. I was just the guy running the test cell, not one of the number crunchers. But it was the opportunity of a lifetime for a 25 year old boost addict. What I saw taught me the little known facts about centrifugal air pumps, and that many of the turbine and compressor maps that are available are only static guidlines without many of the magic variables like exhaust gas expansion due to heat rise in a venturi (hint hint). The trick is to use the turbine to aid the engine with too much valve overlap for proper dynamic compression at lower engine RPM, not to assume the turbine is something that is simply in the way of the exhaust flow. If that were the case airports would be full of large funny looking busses with wings. Fortunately, the turbine is not a flow restriction.

[sketchman]

Food for thought. Thank you.

[ZephTheChef]

Good stuff. What's your take on compressed air directed at the compressor wheel through nozzles for quicker spoolup? I know I can sure get a turbo singing pretty good with a blowgun and shop air (granted, with no load on it). I've heard all sorts of crazy antilag methods (afterburner setups with retarded ignition timing, propane or co2 or compressed air injection into the exhaust manifold, etc), but compressed air directed at the cold side seems like the least likely to do harm to anything (assuming you've got an adequately dry and clean high pressure air supply).

I am certain that any kind of additional antilag would be pointless on my car with the 20psi or so that the supercharger should make on its own, but it is still interesting to think about.

[Advancedynamix]

Centrifugal compressors work great as a secondary compressor, which is the reason for my suggested setup earlier in this thread. Engineers have been compounding centrifugal pumps for at least a century now.
As far as using external means to help spool the turbine, I like what water/meth injection does. Think superheated steam turbine.... taking free HP to a whole new level. On my B6t car I had to jet my water meth down because I was having major overboost issues. On the stock wastegate, and the smallest jet that my stage 2 kit came with I was creeping rapidly to almost 22psig. Zoinks scoob! Babababoost! Haha

[bhearts]

I don't really understand over boost, but I literally have a wire holding my wastegate shut and it doesn't seem to want to go over 12psi. Hope my gauge isn't sticking at 12. Babababoost

[bhearts]

That should be a required word starting now when anyone talks about turbos

[ZephTheChef]

Yeah, you don't have to sell me on water/meth, lol. Love the stuff. Just worry about the compressor wheel if spraying pre-turbo. And as a secondary concern, condensation/freezing in my sub-zero refrigerated air/water intercoolers (although in practice, temps are probably more like 50-60 degrees F...I have managed to hit 0 F and start slushing my coolant in the chilling tank though). Also probably not a good idea with a MAF in blow through.

[bhearts]

Yeah, you don't have to sell me on water/meth, lol. Love the stuff. Just worry about the compressor wheel if spraying pre-turbo. And as a secondary concern, condensation/freezing in my sub-zero refrigerated air/water intercoolers (although in practice, temps are probably more like 50-60 degrees F...I have managed to hit 0 F and start slushing my coolant in the chilling tank though). Also probably not a good idea with a MAF in blow through.

I think he's talking about the rusty wheel, the one on the hot side

[bhearts]

So I bought a miata b6 today. I was having a discussion with Zeph, but do you guys see any issues with hanging a 35lb m90 from the head as long as I brace and support it well from the bottom like the factory mani is

[Advancedynamix]

That should be a required word starting now when anyone talks about turbos

Haha! Deal!

Yeah, you don't have to sell me on water/meth, lol. Love the stuff. Just worry about the compressor wheel if spraying pre-turbo. And as a secondary concern, condensation/freezing in my sub-zero refrigerated air/water intercoolers (although in practice, temps are probably more like 50-60 degrees F...I have managed to hit 0 F and start slushing my coolant in the chilling tank though). Also probably not a good idea with a MAF in blow through.

If you spray pre turbo, it should be as fine a mist as possible. Surging the compressor with water in it will do bad things to the wheel for sure. Probably not a good plan to wet the MAF. I'm not sure what the freezing temp of a 50/50 blend of water and methanol is... Dragonhealer probably knows off the top of his head, maybe he will chime in. I guess you could possibly bring new meaning to the Snow Performance name. haha.

I think he's talking about the rusty wheel, the one on the hot side

I was talking about a typical system where the injector is between the compressor and intake manifold, but yeah, it really gives a boost to the exhaust pressure and velocity. It also makes the exhaust charge heavier, which also aids in the production of babababoost.

So I bought a miata b6 today. I was having a discussion with Zeph, but do you guys see any issues with hanging a 35lb m90 from the head as long as I brace and support it well from the bottom like the factory mani is

Should be fine. You could use a bracket from a FWD B6d or T. That bracket is way overbuilt to stabilize the intake manifold and starter. I think Japan needed to use up some steel when they designed the brackets on these B series engines. Even the B3 has a ridiculous amount of steel bolted to it.

[bhearts]

http://www.andysautosport.com/products/gude_performance__MCZS01.html

I found this cam. Hearing Charlie talk about increased overlap with low back pressure turbo setups has got me thinking. And since I'll have the supercharger attached first, what if I like it by itself, and don't need turbo babababoost?