14 replies to this topic

[85SiHybrid]

Ok, so today I got into a very intresting conversation about the Squires Turbo Systems (the turbo is mounted in the rear of the vehicle where the muffler goes). Anyway he was trying to tell me that since the turbo is in the rear, that the exhaust would not spin the turbo as fast as it would if it were closer to the engine ie. right off the exhaust manifold due to the expansion of the heated exhaust coming from the cylinders.

My view point is this, the amount of air coming out of the engine is the same weather it be at the manifold or the end of the exhaust, however the velosity will be different depending on the exhaust system design, causing a bit of lag.

The only thing that is going to make the turbo spin faster is more air flow through the turbine side of the turbo.


Any thoughts?

Cj

Edited by 85SiHybrid, 04 May 2005 - 05:58 PM.

[bombayscrx]

i agree with your side of the argument

[CRXdan]

That is correct, it woudl take more time now for the turbo to spool because not only do the charge pipes need to "charge with air" but the exhaust system now has to fill itself with enough air to push the turbo the speed it normally would go if it were on the manifold.

I dont like the idea of running 10 foot oil lines to the turbo and haqving a turbo underneath the car which coudl easily get damaged over a bump.

[C_piddy]

this arguement has been posted on HMT and honda tech alot.

i agree with you.... turbo's are more efficent where the exhaust gasses are expanding, think about the heat and the presure that is lost. all that energy is going into heating the exaust.

chris

[5150CRX]

guys don't forget that alot of the energy that the turbo uses is heat energy...not just the gas volume and the gas velocity....that's why it is Ideal to have the turbo as close to the head as possible...the further you get from the motor the more the exhaust gasses cool down.... when the cool down the gas actually gets more dense...efecctively decreasing the volume of the exhaust gasses present...the whole PV=nRT idea. also as the gasses cool down, and become for dense...they slow down and the over all potential energy of the systems suffers loss to cooling...i hope this made some sence...even I don't understand what I'm thinking most of the time

[85SiHybrid]

guys don't forget that alot of the energy that the turbo uses is heat energy...not just the gas volume and the gas velocity....that's why it is Ideal to have the turbo as close to the head as possible...the further you get from the motor the more the exhaust gasses cool down.... when the cool down the gas actually gets more dense...efecctively decreasing the volume of the exhaust gasses present...the whole PV=nRT idea.  also as the gasses cool down, and become for dense...they slow down and the over all potential energy of the systems suffers loss to cooling...i hope this made some sence...even I don't understand what I'm thinking most of the time

<{POST_SNAPBACK}>

So how does heat enery transfer into flow to create pressure on the turbine wheel? The heat is merley a byproduct of incomplete combustion, so I dont get that part.

I see the turbo needing to be closer to the head for shear velocity of the exhaust/unburnt fuel being pumped out of the combustion chamber to drive the turbo since it is still expanding, and traveling faster as it comes out of the cylinder, but how does it cooling down throughout the rest of the system change the actuall amount of exhaust that still has to be put through the turbo?

Aidan, I appreciate the insight here, just trying to understand your theory. Also what is the PV=nRT idea.

Cj

Edited by 85SiHybrid, 04 May 2005 - 09:39 PM.

[loco84]

guys don't forget that alot of the energy that the turbo uses is heat energy...not just the gas volume and the gas velocity....that's why it is Ideal to have the turbo as close to the head as possible...the further you get from the motor the more the exhaust gasses cool down.... when the cool down the gas actually gets more dense...efecctively decreasing the volume of the exhaust gasses present...the whole PV=nRT idea.  also as the gasses cool down, and become for dense...they slow down and the over all potential energy of the systems suffers loss to cooling...i hope this made some sence...even I don't understand what I'm thinking most of the time

<{POST_SNAPBACK}>

So how does heat enery transfer into flow to create pressure on the turbine wheel? The heat is merley a byproduct of incomplete combustion, so I dont get that part.

I see the turbo needing to be closer to the head for shear velocity of the exhaust/unburnt fuel being pumped out of the combustion chamber to drive the turbo since it is still expanding, and traveling faster as it comes out of the cylinder, but how does it cooling down throughout the rest of the system change the actuall amount of exhaust that still has to be put through the turbo?

Aidan, I appreciate the insight here, just trying to understand your theory. Also what is the PV=nRT idea.

Cj

<{POST_SNAPBACK}>

cool air is dincer whitch flows slower.thicker air slower than thin!
DON"T TRY THIS ..put your hand on the tip of your exhust. you can kind of plug it right!? put your hand over your down pipe after the header, you ain't going to plug it!
but I still don't see why moving a turbo to after the header would make that much a diffrence.you could bottom out on it if your car is droped!! as long as you have the intake piped as close as close as you can to the turbo your not going tohave that much lag!on a t25-28 ..

[bigk3000]

doesnt a longer pipe from the turbo to the intake manifold cause lag.. it takes longer for it to compress

[C_piddy]

think about all the energy that is lost threw heat... the exhaust gasses are still expanding close to the head, ever seen a motor run with out headers? fire shootes out, well that heat can be lost by being absorbed threw the exhaust and transfered to the air under the car. still energy that could have been harnessed by the turbo when it's close to the head.

that's my understanding any way.
i am sure that when you are talking about a v8 big block then maybe at 4000 rpm you'll reach boost at like 5 psi lol, but emagin idle, the engine is probably having a hard time sucking air threw the turbo, i could see you loosing alot of bottom end or even a ritch condition because of it.

i am sure that our puny honda motors can't uses these, just too unefficent.... if there were really gains and efficency then why do you see all factory turbos up front by the head.

also think about the intake, and emagine a rain storm lol can anyone say hydrolock aswell as a blown turbo?

and think about the oil and return, you would have to create you own stand alone oiling system..... just retarded... apsolutly retarded.


chris


chris

[C8V6C]

Id think you'd let off the gas...but your car would kee going...since its "finishing" the rest fo the pressure that was all the way through the piping?

[C_piddy]

nah turbos need the engine to be under load to build boost. so whenyou let off your no longer boosting.

chris

[5150CRX]

PV=nRT

Pressure times volume=n(the number of moles)times R(the universal constant) times T(temperature)

basically from this equation.....the numbers of moles of exhaust gas stays constant, the universal constant stay constant, but the temperature changes. on the other side of the equation the volume stays constant, but the pressure will change proprtionally to the temperature, if the temp drops the pressure drops as well

[wessider]

While reading this post the thought that crosed my mind was that heat cause cleaner cumbustion. the closer to the manifold the turbo is the cleaner it will stay...my exhuast is pretty black and nasty at the back. Add mufflers which are designed to slow exhaust gas and create turbulance and that would mean less efficiency.
I would agree with the other side of the argument. The theory behind intakecharge pipping design rules would carry over; the more 90 degree bends and longer the lenght of the charge piping the more the lag time and less volume/flow rate would be the result.

[incubusfan21]

I'm sorry but I have I hard time beleaving that the lag would be an issue. Because in a race situation you would all ready be spooling because you have to rev to launch. Correct? And as far as the issue of heat I don't consider it a factor either, because I know that you should run an iridium plugs which make the burn cooler. But please correct me if im wrong.

[paul barela]

I,ve talked with the STS guy at the race track and he's was a idiot bragging about his yellow ITR w/rear mount turbo. I just wanted to slap the guy up side the head with a copy of Maximum Boost (by Corky Bell) and tell him to read it!!! His old race car was cool. It was a carmen gia w/a porsce engine and a T4 turbo, he would give people a couple second lead and then chase them down. That car ticked off a lot of people he raced.