Silvia Club of NSW
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chasing for 220-240kw from S15.. what turbo??
https://forum.silviansw.com/viewtopic.php?f=1&t=29881		 Page 5 of 8
Author:  omg [ Tue Apr 08, 2008 5:24 pm ]
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mokompri wrote:
same compressor wheel though.. same everything really minus the wastegate

i really dont see the a big difference between the 2 wastegate options in terms of power/efficiency if any. for any given boost pressure thats desired they both have to bypass the same volume of exhaust gasses and will not be allowing absolute flow so as to result in a boost increase from stock wastegate levels.


I think you're underestimating how different the turbine housings are and how much difference they make.

Dave, you should've gone external gate and simply plumbed it back in, change the housing and do it properly rather than pissing about with the internal gate
Author:  badhairdave [ Tue Apr 08, 2008 5:46 pm ]
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Nah.

I had too many issues with the old setup once i started tracking it which was why i decided to ditch it in favor of the stock manifold and new smaller IW turbo.

Removing the whole lot for the 5th time after my 5th track day because the freshly machined manifold had warped again and ripped the rear most stud out of the head (again) was what decided it.

If i can't control the creep with an enlarged IW then i'll have to, but until i have exhausted that route, it stays IW.
Author:  mokompri [ Tue Apr 08, 2008 6:10 pm ]
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omg wrote:
I think you're underestimating how different the turbine housings are and how much difference they make.


please enlighten me :)

my understanding was that the housings were relatively the same other then the IW housing having a hole somewhere on the scroll which is where the IW is.

where exactly are you making the gains with external, or should i say where are you losing power with the internal ? does the housing flow better etc. im intrigued as to why it makes such a big difference, how much are we talking
Author:  splashman [ Tue Apr 08, 2008 9:06 pm ]
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The issue isn't with power in this case, it's with control. omg may have a real world example of power difference between the IW and EW versions, but I think it would be irrelevant in Dave's setup.

You answered your question when you mentioned they both have to bypass the same volume of gas. My understanding is that the actual size of the IW isn't allowing enough gas to bypass once it reaches 3k, causing the creep in pressure.

Thats a primitive explanation I know, but in the real world, this seems to be the issue.

edit: i just realised you were questioning the differences in housing vs power, not the creep issue.
Author:  badhairdave [ Tue Apr 08, 2008 9:43 pm ]
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I don't know that power would be significantly effected. I have no doubt the ex gate turbine housing is better for flow either. I think control is the biggest difference between the 2.

The garrett IW housing is by no means a bad thing. It makes most other internal housings look like rubbish, with the exception of the HKS specific gear which have massive gates. They look to have tried to optimise the turbine outlet at the expense of the wastegate flow though so great top end if it manages to make it there :).

The turbine outlet shape is identical to the non gated housing, it's simply the addition of a gate at the start of the scroll that does less than optimum things to the exhaust flow and, in all honesty, seems to be hideously undersized. It doesn't go close to controlling boost on my engine in the mid range. On the dyno it drops back to the set boost around 5k (i assume where the engine is breathing a lot more and so the turbo has to spin harder to make the necessary flow) but on the road i haven't seen it drop.

Image

Have a look at the position of the wastegate flap in relation to the scroll. There's obviously some not so nice things going on in there.

I think i'll take a few more happy snaps when it comes back off the car. Thank god you can remove a turbo on an rb without removing the manifold. makes like easy(er).
Author:  govich [ Tue Apr 08, 2008 10:03 pm ]
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Are you still running stock internals? if so, bloody hell they take some punishment, i need to man up etc..
Author:  badhairdave [ Tue Apr 08, 2008 10:30 pm ]
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you do.

stock internals are good for 300+rwkw if you keep knock away and the revs sensible
Author:  reaper [ Tue Apr 08, 2008 11:15 pm ]
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but revs are half the fun!
Author:  mokompri [ Wed Apr 09, 2008 9:51 am ]
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badhairdave wrote:
I don't know that power would be significantly effected. I have no doubt the ex gate turbine housing is better for flow either. I think control is the biggest difference between the 2.

The turbine outlet shape is identical to the non gated housing, it's simply the addition of a gate at the start of the scroll that does less than optimum things to the exhaust flow and, in all honesty, seems to be hideously undersized.

yeah boost control issues and being undersized put aside, as it shouldnt affect power potential. no doubt also that the external would also flow more, but again their purpose isnt to flow the max amount, flow is restricted so that you do get a boost increase ie a larger orifice would have the flapper open less then a relatively smaller flapper to give the same desired boost pressure.

anyways, the problem here is that the IW recieves its flow at a right angle from the flow of the exhaust running through the scroll. this is not ideal at all for flow. BUT, every external manifold i have seen, has this same same problem ie a pipe attached close the collector coming off at a 90 degree angle, again not the best for flow. in that regard they both are compromised in much the same way.

its just a matter of which one is worse and whether its better having this disruption to flow occurring in the manifold or in the exhaust housing.
Author:  govich [ Wed Apr 09, 2008 9:09 pm ]
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Chuck a T51R on it, you shouldn't have any boost related problems below 5000rpm then.

/valuable, relevant advice
Author:  Mr Bean [ Wed Apr 09, 2008 11:33 pm ]
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you gona machine "die grind" the wastegate port out urself? or pay gcg etc? shouldnt be more then $150 for gcg to do.
Author:  badhairdave [ Thu Apr 10, 2008 8:46 am ]
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I want the flap enlarged as well so i'll have to pay, otherwise i would have just attacked it myself.
Author:  marshy [ Thu Apr 10, 2008 2:14 pm ]
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just to let you all know i go tthe car back yesterday and it is very impressive.

the cams and gt2871R are a great combo its very responsive, and has a great mid/high range.

the car is only pulling 225kw on 18 psi would of likes a bit more but the injectors are pretty much at thier limit, so dont think i can really get to much more.
Author:  LISTEN 180SX [ Thu Apr 10, 2008 2:54 pm ]
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nice result mate. what injectors are you using?
Author:  marshy [ Thu Apr 10, 2008 4:04 pm ]
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thanks im using Nismo 555cc injectors, its using about 90% and sometimes peaking at about 94%
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