Author Topic: Turbo plenum  (Read 106042 times)

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Offline Jonny Hotnuts

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Re: Turbo plenum
« Reply #150 on: November 06, 2008, 08:06:23 PM »
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I would think you would want the BOV as close the the plenum as possible. If the piping has a curve I would put it on the outside of the bend---due to possible wave hormonics.

If the intent of the BOV is to release potential energy to prevent compressor stall it would seem to me that the closer the BOV was to the turbo would be more effective. If in the case that you have a large amount of volume between the turbo and the throttle plates (this would be my case with a giant intercooler and lots of piping) there would be a few seconds (depending on how big the BOV was) before the compressor would stop seeing forward pressure after the BOV opened.


I am not saying you are wrong Sparky…..just wanting to figure it out in my head.
Anyone ever hear of running 2 BOVs…one on the plenum and one near the compressor?


Also, check out this sweet BOV mod.
http://www.youtube.com/watch?v=L1OQCK0YYTg
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Offline Rex Schimmer

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Re: Turbo plenum
« Reply #151 on: November 06, 2008, 09:50:08 PM »
John and Saltfever,
If the air is going thu the intercooler tubing in a laminar state then you have a boundary layer against the tube surface which at the molecular level means that the air molecule that is in actual contact with the tube wall is going very slow to not moving at all and as you go toward the center of the tube the velocity increases but the molecules are still lined up one behind the other in a nice laminar flowing column of air and the only molecules that can transfer their heat to the tube walls are the ones that are next to it and the ones flowing down the center never get the chance to drop their heat load because they never touch the tube wall. So John you are right that you want the air to be turbulent which means the molecules are in very random movement and continually hitting the tube wall and giving up heat.

In this case turbulence is your friend.

Rex
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saltfever

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Re: Turbo plenum
« Reply #152 on: November 06, 2008, 10:20:32 PM »
Thanks, Rex. Interesting and good explanation.  :-)

Offline jl222

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Re: Turbo plenum
« Reply #153 on: November 06, 2008, 11:11:28 PM »
  The only walls that I've ever seen that were straight on an intercooler were water passages, the air passages are similar to a normal radiator.

                           JL222

Offline SPARKY

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Re: Turbo plenum
« Reply #154 on: November 07, 2008, 12:30:58 AM »
Jhonny,---the air pressure has to spike in the plenum first and the bend----then as the compressor keeps delevering more air---the increasing pressure wave is going to have to back up to the compressor--the high pressure can't start at the compressor first as it has lower pressure volume downstream. We have not addressed the volicity and its sudden stopping that is going to start raising the pressure when it is forced to stop.
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Offline Jonny Hotnuts

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Re: Turbo plenum
« Reply #155 on: November 07, 2008, 11:15:29 AM »
Well the deal has been finalized.

I was able to get a good condition used Precision Turbo PT-2400.
It’s rated at 2400 HP (really about 1400 more HP rating than I need).
The thing goes for around 2500$....lets just say that I couldnt get a 1000 HP intercooler for what I paid for it!

Based on Rexs and others advice I will look into making a restrictor plate that I can block some of the core....that or put tiny vortex generators in front of each air passage!



Also:
Sparky.....
Im putting the BOV in the plenum.....thanks for the advice!

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"Sometimes it is impossible to deal with her, but most of the time she is very sweet, and if you caress her properly she will sing beautifully."
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Offline jl222

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Re: Turbo plenum
« Reply #156 on: November 08, 2008, 01:58:35 AM »
 Good choice on the intercooler, the formula 1 turbo cars ran big intercoolers one on each side on some.
Going from 70 degrees to 100 at bville is way more than 30 degrees when your compressing air.70 degrees 30psi at 14.73atm and 75% compessor efficiency is 327 degrees. [100 degrees.14.73psi=372 degrees]
 100 degrees 30psi 12.73psi [bville lower pressure and more pressure ratio to get 30 psi] is 404 degrees or 77 degrees hotter not 30. Spearco on their web site rates their intercoolers at 400 degrees.
 Sometimes mounting the blowoff valve comes down to the most convenient place,we have ours mounted on the pipe before the intercooler and on the old system on the intercooler box because we didn't have room anywhere else as soon as the throttle closes it senses a vacuum and vents the air and pressure instantly.
 Do you have to run a bov on turbos? We do on our centrifugals because of the direct drive. I think they use them on turbos to keep the turbo spinning when off the throttle.I don't think bovs were around for the formula 1
cars and their are a lot of turbo cars that don't use them.

                                         Good luck JL222

 P.S. Anybody can figure boost temps if you had Hugh MacInnes's book [TURBOCHARGERS] by HPBooks

Offline SPARKY

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Re: Turbo plenum
« Reply #157 on: November 08, 2008, 08:59:45 AM »
Jonny---sorry about misspelling your name---  :oops:  I will try to pay better attention :-P
Miss LIBERTY,  changing T.K.I.  to noise, dust, rust, BLUE HATS & hopefully not scrap!!

"Security is mostly a superstition. It does not exist in nature, nor do the children of men as a whole experience it. Avoiding danger is no safer in the long run than outright exposure. Life is either a daring adventure or nothing."   Helen Keller

We are going to explore the racing N words NITROUS & NITRO!

Offline Jonny Hotnuts

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Re: Turbo plenum
« Reply #158 on: November 08, 2008, 01:10:07 PM »
Quote
Do you have to run a bov on turbos? We do on our centrifugals because of the direct drive. I think they use them on turbos to keep the turbo spinning when off the throttle.I don't think bovs were around for the formula 1
cars and their are a lot of turbo cars that don't use them.

You car correct that you dont have to run a BOV for a turbo vehicle.
You are also correct that it keeps the turbo spinning.

When the throttle is released the motor stops making exhaust....so the driving force to the turbine is suspended. Because the throttle is closed and the engine is no longer accepting pressure and nothing is driving the turbine, all the pressure made by the turbo during WOT now tries to force the turbo to run backwards and can result in a broken turbo.

The BOV is supposed to give you a performance advantage by allowing the turbo to spool quicker after you hit the gas again. My reason is only to prevent compressor surge and hopefully a turbo that doesnt break.
(I have WOT clutchless shifting, the BOV wont open unless there is a problem or at the end of the run).

Quote
Posted by: SPARKY 
Insert Quote
Jonny---sorry about misspelling your name---    I will try to pay better attention 


No worries Sparkie!!!

LOL

« Last Edit: November 08, 2008, 01:12:04 PM by Jonny Hotnuts »
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Offline Jonny Hotnuts

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Re: Turbo plenum
« Reply #159 on: November 08, 2008, 01:16:21 PM »


Something else you could do with a BOV is to direct the output of the BOV back into the exhaust in front of the turbine. As apposed to venting to atmosphere the energy created and lost could be used to maintain higher turbo RPMs and improve lag times between shifts.

I have never heard of this being done.... but it should work.
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"Sometimes it is impossible to deal with her, but most of the time she is very sweet, and if you caress her properly she will sing beautifully."
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Offline Stainless1

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Re: Turbo plenum
« Reply #160 on: November 08, 2008, 01:34:39 PM »
Jnuts, the BOV also prevents boost spikes, when you close the throttle, that turns down the fuel, but does not immediately stop boost, boost actually rises unless released by the BOV.  Higher boost and less fuel, want to venture a guess what happens next... Don't be concerned with turbo lag in LSR, be concerned with intake temps, boost levels and A/F ratio... oh, and have fun...  :cheers:
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Offline maj

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Re: Turbo plenum
« Reply #161 on: November 08, 2008, 03:29:49 PM »


Something else you could do with a BOV is to direct the output of the BOV back into the exhaust in front of the turbine. As apposed to venting to atmosphere the energy created and lost could be used to maintain higher turbo RPMs and improve lag times between shifts.

I have never heard of this being done.... but it should work.

World rally car stuff
add some fuel and turn the turbo into a turbine for a second , turbo maintains its speed during gear changes...
hard on the exhaust turbine and not practicle in LSR but sounds cool...

Offline Jonny Hotnuts

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Re: Turbo plenum
« Reply #162 on: November 08, 2008, 04:00:48 PM »
It was just thinking out loud.
Wasnt considering doing it.

-
Quote
World rally car stuff
add some fuel and turn the turbo into a turbine for a second , turbo maintains its speed during gear changes...
hard on the exhaust turbine and not practicle in LSR but sounds cool...
Was this the reason I remember some turbo race cars shooting flames out the exhaust when shifting?
« Last Edit: November 08, 2008, 04:03:32 PM by Jonny Hotnuts »
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"Sometimes it is impossible to deal with her, but most of the time she is very sweet, and if you caress her properly she will sing beautifully."
*Andres Segovia
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Offline 1 fast evo 2

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Re: Turbo plenum
« Reply #163 on: November 08, 2008, 05:09:51 PM »
I hope I can add a little helpful info here.

Rex- you are rite about there needing to be turbulence to have intercooler eff. Most if not all good intercoolers have inside the tubes little air trips called turbulators that do just as you surmised, they break up the laminar flow which increases the eff. of the core.
The eff. of a core has to do with how well they balance the shape and amount of the turbulators which equals either better cooling or less pressure drop through the core.

J.H. - as far as the blowoff valve is concerned Sparky is rite on. In most auto applications you install it between the intercooler and the throttle body.
As far as having 2 blowoff valves you won't need that unless you are making over 850 hp to the wheels.
Also I would not try to vent the blowoff into the exhaust unless you want some cooked parts. If anything you can vent the blowoff back into the intake.
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Offline Jonny Hotnuts

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Re: Turbo plenum
« Reply #164 on: November 08, 2008, 06:20:50 PM »


Here is the BOV mounted.
The unit is a HKS, even though this is a very popular and well respected unit I cant say I am real crazy about the construction. Seems cheap and the little chrome plastic section in the front is to give it that "High School kids Civic sweet bov whistle sound" is duke. 
I powder coated the housing to match the valve cover and removed the casting marks.

I feel better about it now.

Quote
Also I would not try to vent the blowoff into the exhaust unless you want some cooked parts. If anything you can vent the blowoff back into the intake

THis concept would have to be worked out and the use of conventional units would not be acceptable.

You would need something more on the lines of a wastegate (valving for heat) and a way to make sure the pressure being vented was higher then the pressure in the exhaust.

This was just an idea...nothing more.
« Last Edit: November 08, 2008, 07:07:28 PM by Jonny Hotnuts »
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"Sometimes it is impossible to deal with her, but most of the time she is very sweet, and if you caress her properly she will sing beautifully."
*Andres Segovia
(when Im not working on the car, I am ususally playing classical guitar)