quenching turboed exhaust

[fred slawson]

This thread is on the lines of helping the turbo spool up faster. If you ran a small line off of the compressor side to downstream of your turbo it would quench the heated air and cause its pressure to collapse. This would increase the delta P across the turbo allowing it to spool up quicker. The tricky part is not pressuring your tail pipe up with the relatively colder air. I think this could be engineered to a degree and the rest would have to be fine tuned of a dyno. Oh well there I go thinking outside the box with 4hours sleep. Maybe I'm just crazy.

[Mikael]

1. Pressure is what is allowing the turbo to spool, you don't want to decrease that.

2. Before the turbo has spooled, the pressure in the exhaust is greater than the intake side, so it will flow out of the exhaust slowing the spool even more.

3. Perpetual motion doesn't work, sorry.

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[pvtschultz]

I understand what he is trying to say and it is a very interesting topic. What Fred is trying to say is what has been used for over a century on steam turbines and steam engines. By injecting a cold air stream into a hot air stream, the exhaust will be drastically cooled, causing the pressure to drop substantially creating a greater pressure change across the turbine, theoretically allowing it to extract a lot more power from the exhaust stream. With the extra power it would be able to spool up much quicker.

The problems:

The lowest pressure that can be acheived is atmospheric, or 14.7 psia. Right after the turbo on a high flow exhaust the pressure isn't going to be that much more than that of the air around it, maybe in the neighborhood of 15 psia or so, maybe 16 psia. Therefore, change in the change of pressure across the turbo isn't going to sustantiat drawing enough air from the intake to cool the exhaust. On a steam turbine, a pump is used to bring the 6-7 psia pressure after the condensor to the 200-250 psia pressure of the boiler, in this case, it is going to be impossible to get less than 14.7 psia and still have exhaust flow.

I will give you props for the idea though, but in this case, I really don't see it working very well. I can do the math on this when I am done moving, but I don't see a change in thought from anything right now.

[fred slawson]

Cplshultz you are correct about not getting less than atmospheric pressure or you would have no exhaust flow. I fact if you had less than atmospheric you would have revision of flow. Were I work we use steam jets and steam turbines and that is were I got the idea for the project. I really would have thought that there would have been more pressure after the turbo something like 5psig. With temp off the compressor side being sub 100degrees F(with a 75% efficent intercooler) and I figured exhaust after a turbo would be 300degrees F. I wasn't thinking of going below atmospheric just inbetween turbine discharge pressure and atmospheric. By the way at 1 bar of flow it comes out to 717cfm I assume at 70 degrees F. Anyway I think I have most of the information correct I just don't have the discharge pressure curve or discharge pressure temp curve. Anyway I've rambled enough and I need to go to bed, just got off work. Thanks guys once again.
PS. Just had another thought. What if we made the tubing come in at a steep angel relative to the exhaust to make it a jet effect possibly pulling a vaccuum on the upstream side. I know go to bed.

[Mikael]

I now understand more what you're talking about- injecting the air AFTER the turbine wheel. Makes more sense, but some of the things i said still do apply.

[Arctc Wolf]

with a good low restirction exhaust, there wouldn't really be need to cool the air down. make sure the piping is at least 3" and that the muffler flows well, and u'll be fine.

[fred slawson]

Artic wolf I absolutely believe what you say about the 3" pipe. Just thinking of ways to spool up a T-61 turbo quicker. Trying to have my cake and eat it too. I also love thinking outside the box even if I don't actually do it. I see forums as a way to share and spark new ideas along with sharing triumphs and failures to me it is all gain. Any knowledge that pertains to the subject, good or bad as long as it is accurate. Time to get off the soap box.

[Arctc Wolf]

with lower boost levels, ceramic wheels spool a lot faster. these wheels are found in the R34 skyline turbo's. However, they can't withstand boost pressures above 17 psi, meaning that if out motor was completely built up, and as efficient as we could get it, we'd probly be able to use 15 psi w/ 9.0:1 compression(lower than max psi cuz it's smart to have some safety margin). also, Garrett has come out w/ newer wheels w/ better aerodynamics, spooling faster w/ a wider boost range. and as usual, ball bearing center sections are key to low spool up time. I stated in a tubro header discussion a few weeks ago that a tuned length header that is as close to the heads as possible will help spool up, and the shortest piping available from the air filter, through the turbo, piping, and intercooler will also help get power quicker.

[mattsv6]

the exhaust heat actually helps the turbine spool faster believe it or not. that is why you wrap the exhaust housing and down pipe. the motr heat in the housing the better "if it is kept in a reasonable sense". the only problem with this is that is contaminates the intake chrge air with excess heat and makes problems with detonation and pre-ignition. all you need to control the exhaust heat is proper fuel mixture and a high efficiency intercooler. if the air charge air temp is decreased, so is the exhaust!

[Arctc Wolf]

actually, wraping the exhaust keeps radiant heat away from the intake air, making it cooler. this is why ppl put heat shields over their turbo manifolds and their exhaust housings so that it keeps heat near that area. inconel it the best for exhaust housings, exhaust manifolds, and downpipes because of it's heat retaining abilities.

[mattsv6]

are you telling me that heat doesnt have any part in spinning the exhaust wheel?? remember, heat expands!!!

[fred slawson]

Artic Wolf I think he was talking about heat coming throuh the turbine body into the compressor side. What you both said makes sense if taken in its perspective. Peace brothers.

[Arctc Wolf]

no, 80% of the energy spinning the exhaust wheel is heat energy. I meant heat escaping the exhaust pipes, manifolds, and turbine housing will increase intake charge temps and cause less hp. it'll also spool the turbo slower, since the heat is being radiated instead of used to spin the turbine wheel.