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Common turbo issue's

  #1  
Old 10-03-2012, 09:29 AM
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Common turbo issue's

Im in the process of putting a turbo kit together for my Jazz. I was just wondering if there are any common issue's when boosting these cars?

I know there isn't that much space for the turbo and it's pretty close to the clutch and brake lines. Has anyone had any problems (heat wise) with this?


Thanks for the help.
 
  #2  
Old 10-03-2012, 01:41 PM
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soudns liek your peicing together a kit. we cant say what issues there are since we have no idea what your kit will consist of.

heat is always bad. get the reflective heat tape from DEI. cover everythign behind and above the turbo with it, even the engien harness. better safe than sorry.
 
  #3  
Old 10-03-2012, 02:39 PM
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I am indeed, Sorry for the vague nature of my post...im used to NA honda's, so this is completely different from what im used to.

The kit is going to be pretty basis as im not after big power.

List so far is

FMIC
2" intercooler piping
t25 turbo
Custom tubular manifold
2.25 exhaust
re-circ dump valve
crv injectors or stock
Dastek piggyback ecu

Would wrapping the turbo mani and getting a heat blanket for the turbo help? So pretty much cover most things in the vicinity of the turbo then?
 
  #4  
Old 10-03-2012, 03:07 PM
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If you are using a T25, and you are making your own manifold.. do one of two things.

Provision for an external wastegate mounted off the manifold, either dumped to atmosphere or recirculated 12-18" downstream.

Or port the hell out of the internal wastegate hole on the turbine housing and use at least 2.5" ID downpipe.

Boost creep is a real problem.
 
  #5  
Old 10-04-2012, 11:24 AM
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Originally Posted by DiamondStarMonsters View Post
If you are using a T25, and you are making your own manifold.. do one of two things.

Provision for an external wastegate mounted off the manifold, either dumped to atmosphere or recirculated 12-18" downstream.

Or port the hell out of the internal wastegate hole on the turbine housing and use at least 2.5" ID downpipe.

Boost creep is a real problem.
If he keeps the exhaust fairly restrictive (like not going to a 3" exhaust), he shouldn't have any boost creep with a t25 from something like a Nissan sr20 motor. The china chargers are another story.
 
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Old 10-04-2012, 11:34 AM
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Why on earth would you use a restrictive exhaust to combat boost creep?

Post-turbine backpressure is multiplied by the turbine expansion ratio and is additive to Pre-turbine drive pressure.

On a tiny T25 from the SR20, if you have 2:1 drive:boost ratio, which is common and you have significant enough restriction to fight the gasses trying to bypass the turbine through the waste-gate port... you are killing efficiency of the turbine to transmit energy to the compressor.

That is in turn hurting the engines VE, and on an NA cam with significant overlap like ours and an exhaust manifold with an open collector you are going to have reversion through the intake valves, increased chamber temperature and a not quite inert, hot contaminant constantly entering the cylinders under boost where you need it clean, cold and clear as much as can be achieved.

You are also increasing both IATs and EGT. This lowers the knock-threshold and commands a less aggressive timing and fueling scheme.

All of these things are a big no-no in general, and especially on a pump gas car. You will be making less power per psi boost as a result. Spool will be increased significantly as well. This further hurts transient response and low/mid-range torque production.

That approach is so fundamentally flawed it's not funny and should never be offered as advice.

Lyon was using a Nissan T25, ask him how bad the creep was, even on his small exhaust.

What did he end up doing? Porting out the hole and unshrouding the internal gate's inlet port on the volute side.
 

Last edited by DiamondStarMonsters; 10-04-2012 at 11:38 AM.
  #7  
Old 10-04-2012, 11:58 AM
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Originally Posted by DiamondStarMonsters View Post
Why on earth would you use a restrictive exhaust to combat boost creep?

Post-turbine backpressure is multiplied by the turbine expansion ratio and is additive to Pre-turbine drive pressure.

On a tiny T25 from the SR20, if you have 2:1 drive:boost ratio, which is common and you have significant enough restriction to fight the gasses trying to bypass the turbine through the waste-gate port... you are killing efficiency of the turbine to transmit energy to the compressor.

That is in turn hurting the engines VE, and on an NA cam with significant overlap like ours and an exhaust manifold with an open collector you are going to have reversion through the intake valves, increased chamber temperature and a not quite inert, hot contaminant constantly entering the cylinders under boost where you need it clean, cold and clear as much as can be achieved.

You are also increasing both IATs and EGT. This lowers the knock-threshold and commands a less aggressive timing and fueling scheme.

All of these things are a big no-no in general, and especially on a pump gas car. You will be making less power per psi boost as a result. Spool will be increased significantly as well. This further hurts transient response and low/mid-range torque production.

That approach is so fundamentally flawed it's not funny and should never be offered as advice.

Lyon was using a Nissan T25, ask him how bad the creep was, even on his small exhaust.

What did he end up doing? Porting out the hole and unshrouding the internal gate's inlet port on the volute side.
Pardon my ignorance for offering advice on what is most definitely a low power build (using stock injectors) and is probably going to run a 5psi wastegate. Clearly boost creep is guaranteed as someone else has experienced boost creep before. Thank you again.
 
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Old 10-04-2012, 12:09 PM
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Ignorance doesn't deserve a pardon.

It's precisely because it is intended for relatively low power and low boost, and that they will likely not have enough fuel system or a tune provisioned for extra airflow and the added heat that comes with that such things are important to clear up.

Someone melting parts, lifting the head or windowing the block could well be the result of following misinformation.

Boost creep was experienced with the same turbo, on a 2.25" exhaust. You can search his threads to find the damage that ensued. Boost creep is not a function of where the turbo was manufactured either.

Sarcasm and mild butthurt aside, this stuff is to be taken seriously when there are thousands of dollars at stake.

You responded directly to my post like you were correcting it, here's me correcting you with facts and experience with the platform.
 

Last edited by DiamondStarMonsters; 10-04-2012 at 12:13 PM.
  #9  
Old 10-04-2012, 12:38 PM
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Thanks for all the information guys.

I know a 2.25 system isn't ideal for the set-up, but i want to keep the noise levels down as much as possible and im not looking for huge power. Just a nice bump from stock.

From what i've gathered, porting out the internal wastegate hole and combining that with a 2.5 downpipe i will eliminate the chance of boost creep? Even with a 2.25 system.
I want to make sure that the car is super reliable.

I'll be using a t25 from an s13, so not any cheap crap off ebay.
Aside from Neukin, is there anywhere else that offers turbo manifolds? I know i said i was going the custom route, but if i can cut down the time the car is off the road that would be awesome.
 
  #10  
Old 10-04-2012, 02:15 PM
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The difference in noise will be negligible, and certainly outweighed by the greater cross section going to 2.5"

If you are concerned with noise a proper resonator and muffler will take care of that. The turbine wheel its self muffles sound. Sound is energy too, and is part of what is transformed to torque on the shaft that turns the compressor wheel.

The greater the pressure and temperature drop across the turbine wheel the more efficient the setup is on multiple levels. This means more power per psi boost pressure and cooler intake temps which means more spark advance, and thus lower EGT as well.

Porting the internal wastegate hole on the Nissan T25 is necessary.

The relationship of waste-gate flow to boost pressure is an inverse proportion.

More boost means less exhaust gas has to bypass the turbine.

Less boost means more gas has to bypass the turbine.

One look at the port area behind the internal gate's flapper should make this an obvious necessity. The 2.5" pipe will make you more likely to creep if the port is unmodified because it creates a larger pressure drop across the turbine wheel which makes your setup more efficient, but it has also reduced the post turbine drive pressure that would otherwise be forcing the waste-gate closed along side the actuator.

The proper remedy is to port the waste-gate hole. The band-aid that hurts the rest of your setup, its efficiency and reliability would be to keep a restrictive pipe.

Use the 2.5" ID downpipe. For the small inconvenience of having to unbolt the turbine housing, port and clean ... you are gaining a wide variety of advantages in doing so.

To go with the band-aid fix you are creating many more less than obvious problems that will hinder performance, reliability and require a much more conservative and accurate tune.

Nobody at this point offers a manifold for the GD or the GE specifically. If you have a first gen (GD) just continue with your plan to have a custom manifold made, it will be most likely better flowing than the Neukin unit.

If you have a GE, you have an integrated manifold, and I would still have the head to manifold pipe custom fabbed. Or you can use and modify the bolt holes on an R18 Turbo Collector.
 
  #11  
Old 10-05-2012, 11:15 AM
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Dude, thank you for all the info..........slowly wrapping my head around everything.
I feel far more confident going into this whole process with all your input!
 
  #12  
Old 10-13-2012, 03:25 AM
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Tubular manifold? If you can pull that off with the limited space please post pics
 
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