external wastegate sizes....

[Sydneykid]

Bump, because it might save me answering a whole pile of PM's

cheers

[SirRacer]

just to throw an interesting (i hope) problem into the midst

for example im planning on putting out 350 rwkws in my rb30. i will be hopefully running about 22/25 psi to do that.

if the above formula is correct(everything else sydneykid says generally is) what is the perfect application for me if im going to have different boost levels. for example an around town level and a max power level

should i simply focus on the wastegate for my better application and put up with the lag around town (where i dont need it)?

[Sydneykid]

just to throw an interesting (i hope) problem into the midst

for example im planning on putting out 350 rwkws in my rb30. i will be hopefully running about 22/25 psi to do that.

if the above formula is correct(everything else sydneykid says generally is) what is the perfect application for me if im going to have different boost levels. for example an around town level and a max power level

should i simply focus on the wastegate for my better application and put up with the lag around town (where i dont need it)?

Why do you want to run 2 boost levels? If you don't want to go as fast, don't press the throttle down so far.

cheers

[SirRacer]

running 350kws in an a31 cefiro with 235 tyres isnt going to allow for a lot of traction

my reasoning behind it is that if i could limit the boost pressure maybe when driving around town i would still be able to nail it and get half usable power, without the car going completely sideways on me

i think a bit of right foot control may be the better option. something i definitley need to work on however and im quite content on flat down

[Craved]

HAHAAHAHA i remember this thread now..

im runnning 294 rwkw with a 38mm wastgate @ 18psi

so i didn't need th 22 psi you stated way back when..

issues with spark breaking down, and wastegate sticking ..

new WG and splitfires to go in now..

the sticking wastegate means i really dont know how the response is as it changes everytime we ran it on the dyno..

--------------------

one thing though, no matter what it seems to drop boost up top, even with the ID3...

would you suggest running the WG pressure feed from the plenum rather than the compressor outlet pipe?

[DjeMz]

No one really talked about a rb25 + hks 2535 combo

im currently running 16psi, was on 18 but was spiking way too much (up to 22, dropped back to 18 n made 240rwkw)

my questions:

which size external gate would be best to hold 19psi

is 19psi safe with 2535

do i need an ebc or will the gate control it all?

/end noob questions

[h2k]

I have about 550-600hp on my RB25DET engine with GT4088R turbine. I tried running a 38mm tial wg but at high rpms the gate got to small and could not limit the boost pressure so it went up to 2.0 bars of pressure after 5500rpms. So I changed to a 50mm wg and now I can limit the boost down to whatever I set the springs to, all the way up to 8000rpms. So if you are after high power, but still retain a reasonable boost for regular fuel octane(1.6bar), you need a big enough wg and for that a 38mm wg will be to small. a 44mm will propably do, but a 50mm gate will be slightly overkill as long as you stay under 700hp.

[Lithium]

I have about 550-600hp on my RB25DET engine with GT4088R turbine. I tried running a 38mm tial wg but at high rpms the gate got to small and could not limit the boost pressure so it went up to 2.0 bars of pressure after 5500rpms. So I changed to a 50mm wg and now I can limit the boost down to whatever I set the springs to, all the way up to 8000rpms. So if you are after high power, but still retain a reasonable boost for regular fuel octane(1.6bar), you need a big enough wg and for that a 38mm wg will be to small. a 44mm will propably do, but a 50mm gate will be slightly overkill as long as you stay under 700hp.

Yep. I think the "more boost, smaller gate" theory is a bit whack. You basically need enough wastegate to drop the turbine pressure sufficiently to stop spinning the turbo more. GT4088R on an RB25 is an interesting combination - what is the spool like?

[h2k]

Yep. I think the "more boost, smaller gate" theory is a bit whack. You basically need enough wastegate to drop the turbine pressure sufficiently to stop spinning the turbo more. GT4088R on an RB25 is an interesting combination - what is the spool like?

In low gears it's pretty slow, I geet boost at 4500rpm and then it just explodes with power. But in 4th gear I get 1.5bars from 4000rpm. Im running a pulse split\divided exhaust manifold so it helps spool-up alot

[TTOBES]

Hey Sydneykid

That was a superb writeup with some excellent information...

How does your principle/formula relate to internal wastegates and why do so many people have problems with them??

Can you predict internal gate performance/problems using this formula??

If a turbo is, as you said, near optimum for the boost and horsepower required (that is correctly sized for the application) and used at high boost levels at or near to it's potential, then it needs a smaller wastegate to control boost levels.

Wouldn't an internal gate be able to control boost in this case??

Also you mentioned that an external wastegate with a flapper type valve flowed more than any of the poppet style valves.

Does this also apply to internal gates as they are a flapper type??

If so, would an internal gate flow more than an equivalent size external gate??

See what happens when you make me think!!

Cheers

Bill

[discopotato03]

Craved the compressor map for the Garrett GT3082R (GT3040R) is the same as the GT3582R (GT3540R) because they both use the same compressor wheel and housing . You mentioned that your turbine housing A/R is 1.12 so if its a HKS GT3040 the compressor wheel is 50 rather than 56 trim so don't bother with the GT3582R's map . Garretts GT4082 map at the turbobygarrett site would possibly be closer though it uses a GT40 comp cover so who knows .

I also think the wastegate size from boost pressure theory is hogwash . To a degree exhaust mass flow can be estimated from inlet air flow so basing wastegate size on on an inlet air flow reference seems more logical to me .

H2K , yep a GT4088R is pretty big for an RB25 but for a large turbo its way to go I think . As Geoff Raicer would say they are useless in single scroll turbine housing form and are twin scroll standard . This forces you to use a T4 twin port flange exhaust manifold which is as it should be .

Twin scroll turbo systems (I think anyway) change the whole world the engine see's on the exhaust side so what works with wastegates is also different . Geoff tends to use two external gates with his pulse divided exhaust manifolds (when cost is no issue) so obviously having a lot of valve area is not the issue it is with single scroll turbine housing set ups . I think the reason for this is that the divided manifold has greater pressure and flow fluctuations so you need greater bypass area to vent the gas when its under less pressure . The single scroll housing has more consistant pressure and flow across its single nozzle so if the gate use is too big the sudden pressure drop when it opens is going to cause the turbine (and therefore the compressor) speed wise to do eratic things .

2 more cents spent , cheers A .

[TTOBES]

Hey Sydneykid

That was a superb writeup with some excellent information...

How does your principle/formula relate to internal wastegates and why do so many people have problems with them??

Can you predict internal gate performance/problems using this formula??

If a turbo is, as you said, near optimum for the boost and horsepower required (that is correctly sized for the application) and used at high boost levels at or near to it's potential, then it needs a smaller wastegate to control boost levels.

Wouldn't an internal gate be able to control boost in this case??

Also you mentioned that an external wastegate with a flapper type valve flowed more than any of the poppet style valves.

Does this also apply to internal gates as they are a flapper type??

If so, would an internal gate flow more than an equivalent size external gate??

See what happens when you make me think!!

Cheers

Bill

Bump...

[Craved]

Craved the compressor map for the Garrett GT3082R (GT3040R) is the same as the GT3582R (GT3540R) because they both use the same compressor wheel and housing . You mentioned that your turbine housing A/R is 1.12 so if its a HKS GT3040 the compressor wheel is 50 rather than 56 trim so don't bother with the GT3582R's map . Garretts GT4082 map at the turbobygarrett site would possibly be closer though it uses a GT40 comp cover so who knows .

swapped down to the 0.87 rear housing, running the tial 38mm gate without a boost controller, steady 14psi from go to redline.

starts around 3500 and all in by 4200 (road use only - no dyno run after rear housing change-yet) so that cut me down 800-900 rpm

[T04GTR]

yeah im using a atleast 10 year old garrett 42mm one. and its awsome!! been on 3 cars now. used to be on "freaky" pac rx3 ehhe it holds anything over 1.1bar dead flat all the way to redline. (with a boost controler) now its suporting 1.6 bar and 376awkw no probs.

[MBS206]

So, I'm bumping this up, as the last part I'm chasing down at the moment, is a wastegate.

I'm looking to make around 340RWKW at about 24PSi, and also have the ability to drop down to around 18PSi (Around 290RWKW if my calcs work out, they're only rough)

So, I'm attempting to calc it all out, but I'm getting confused at the boost correction part...

So let's apply it to your car;

340 rwkw = 544 bhp

480 bhp = 49.5 lbs of airflow = 49.5 mm wastegate

After that, I get lost...

Note, that above calcs might well be wrong!

[R31Nismoid]

Turbosmart 45mm or the i think 55mm Tial would slot into that nicely.

[driftmeister]

Nice write up SK.

Im fitting a T04E (50 or 53 trim) with around 38mm WG that came with the HKS Cast manifold for my R34GTT. My mechanic mention the WG is too small for running hi boost. Internal is stock other than the thicker metal head gasket (1.5mm i guess) and seals changed while the turbo is going in.

What boost is efficient for this turbo? Not enough cash to get a bigger Wg atm.

[KISIN]

rb30det (about to be built)

gt4082 - can get 1 for cheap-ish and also can get a tial 38mm wg.

max boost atm will be 14psi, hoping for ~270rwkw ?

Would the 38mm do the job fine at 14psi ? Eventually will push closer to 20psi+ after a forged rebuild.

(PS: Sorry, i did try using the formula, but as i have no experience what the 30det with a 4082 would make on certain psi, i wasn't able to calculate properly...)

Edited January 9, 2008 by KISIN

[bubba]

My 44mm TiAl gate arrived yesterday.. man it's shiney

Can't wait to start putting it all together, hopefully the gate is big enough.. I'm only wanting to push 300rwkw out of the GT35R for now.

[CeJay]

ok hang on I though 1kw was 1.34 hp, how are people getting figures of 340kw = 540hp?

kW: kilowatt. 1kW = 1.34hp. EU countries such as Germany prefer to use kW

http://www.pistonheads.com/gassing/topic.a...h=&t=186006

and from SK's early response

300kw * 1.34 = 402 bhp not 480 , even if you factor in driveline loss it doesn't add up, couldn't find any other stickied wastegate thread either.

so someone tell me if I'm f**king up the calculation