What size external gate for a GT35R?

[Kevin Jewer]

Spike is almost ALWAYS strictly a function of the boost controller's response time. I'm not surpeised that you don't get any spike without the boost controller hooked up, the wastegate and it's actuator are very good at their job. I'm not sure what you mean by your second question.

 

[paul s]

I'm running 38mm Turbosmart gate with 7psi(17psi is on order) spring and 60-1 turbo. The boost stays at 6psi from 3000rpm in 4th to redline with no creep. But at the same time with the 7psi spring the max boost is limited to ~23psi with Blitz R boost controller. The wastege is off the manifold.

 

[Turbo Monk3y]

35R + turbonetics Manifold and tial 38 running 25-29psi holds rock solid even with the weird location on the Turbonetics manifold...

 

[Boosted98gsx]

I dont care about the thing running 25 psi. I know it can do that. I'm talking about it being able to handle the exhaust flow to keep the boost around 18 or so.

 

[Turbo Monk3y]

I dont care about the thing running 25 psi. I know it can do that. I'm talking about it being able to handle the exhaust flow to keep the boost around 18 or so.

Who runs 18psi nowadays sheesh welcome to 1999

 

[Boosted98gsx]

Who runs 18psi nowadays sheesh welcome to 1999

It's my only car. I like to keep things relatively civil on the street.

 

[definitiveno]

How about for a gt30/40r? I bought a 44mm tial with a straightline tubular.


In a semi-related topic what would you guys prefer for a daily? GT30/40r with .63 turbine housing or GT35r with .63 turbine housing. I have been looking at a GT30/40R with .83 turbine housing but I am not sure that would offer any benefits over the formentioned GT35R....

 

[d j]

I think a lot of people do not realize or understand that the more boost you run, the smaller the wastegate you need.

with that in mind, wouldn't ya over-run / over flow the exhaust exit on the wastegate?
lets assume racer-x runs 10psi for daily driving but fills up with race-fuel for the track on weekends.... running 30+ (or 40 in my case) wouldnt you be shoving more ehxaust through the wastegate than it was designed to handle (in turn causing creep by not allowing the gases to exit 100%). on that same token/quote...

...a few rules
1) to build pressure, the gate remains closed (to direct all exhaust to the turbine)
2) to keep pressure, the gate opens (to bypass the turbine) & releases excess exhaust

so as result of the valve being small, an amount of the excess exhaust is being routed to the turbine - causing additional boost / creep / spike, right? there is a reverse affect if your gate is too big.

i guess i'm not understanding how a smaller gate/valve is better in higher exhaust ouput cars (RX7 for example).

...sorry for the hijack

 

[tstkl]

the idea is that since you are running higher boost, and your turbine wheel is spinning at a faster rpm, more energy is needed to maintain said speed. Therefore more exhaust must be directed towards the turbine wheel for higher boost, and less goes through the wastegate. BUT, the car IS running under more boost, so therefore more exhaust gases are being created. Personally I think, as long as you go big, you should be fine. I know someone is going to come in here and say bigger is not always better, but in my opinion, there is almost no physically possible way in which a bigger wastegate will hurt performance. The spring in the wastegate is regulated by the intake manifold pressure, so if the wastegate lets by too much exhaust and the turbine wheel slows down, the intake manifold pressure drops and the wastegate closes again, causing the turbine wheel to speed up again.

 

[Eagle 5]

Best example of this I can find is one that FP uses on their site. When talking about their FP3052/ 3065 turbos and using the tial 40mm wastegate. They say boost can be set as low as 14 psi without creeping. Meaning the minimum boost you could run with that turbo/ wastegate combo is 14 psi. Anything less and it will creep to 14 psi. Run any higher boost than 14 psi and it will not creep. Run a larger wastegate and you could run less than 14psi since its able to bypass more exhaust gas.

Another example would be, say you have a turbo set to run 15 psi with whatever wastegate. Well, you go out and it hits 15 psi but then creeps to say 17 or 18. Well your wastegate can not bypass enough exhaust gas so the turbo creeps (duh, this is nothing new here) So, you set your boost controller to 17 or 18 psi, turbo hits that boost quicker now and it doesn't creep. You run 20 or mor psi, turbo will not creep.

Same thing with the externals or internals. The larger the wastegate the LESS boost you can run without creeping. Once you started running more boost beyond the "creep point" (ya, i made that up...i hope) you will not creep but only hold there. Other than boost dropping off if the turbo just can't handle it. Ya more exhaust is created but you need more of it to keep the turbo spinning at the higher turbine speeds.

Maybe that helps explain. For in the case of the guy running 10 psi on the stret and 40 on the track, well ya, you will need a bigger wastegate to run 10 psi. But if you ran say 20 on the street and 40 at the track, you would not need as big a wastegate.

Hopefully that helps expains why a large wastegate is not always needed. It all depends on how low of boost you want to run and with what size turbo.

Note: Completely disconnecting a wastegate has a much different affect. In the case of a big16g I had. With the wastegate disconnected it would build about 3 psi. However with it connected, the minimum boost I could run was 14 psi. I'm sure you guys can figure out why but with the wastegate disconnected, enough exhaust gas was never made to get the turbo spooled up enough because exhaust gas was always being bypassed.

 

[d j]

Best example of this I can find is one that FP....

alright so what i dont know (rather, overlooked) is a situation where racer-x wants to run low boost (v8 guys for example).

So what we're saying is...
- If your application specfics call for 8psi or less then a smaller gate IS NOT suited for the situation due to over flowing the gate valve as where a larger gate wouldn't over flow/run with exhaust gases.

is this right? i've always overlooked the 'need' for low boost;

 

[Eagle 5]

alright so what i dont know (rather, overlooked) is a situation where racer-x wants to run low boost (v8 guys for example).

So what we're saying is...
- If your application specfics call for 8psi or less then a smaller gate IS NOT suited for the situation due to over flowing the gate valve as where a larger gate wouldn't over flow/run with exhaust gases.

is this right? i've always overlooked the 'need' for low boost;

The example here would be to look at the honda guys (or anyone else with an aftermarket turbo kit running low boost really) They have fairly large turbos but only put out maybe 5-10 psi on their stock blocks. No where near what the turbos in those kits can usually handle. They also have large wastegates because they need to be able to bypass enough exhaust to keep the turbo from creeping any higher or building any more boost.

 

[Mark S.]

Whoever on here is telling you that smaller wastegates are needed for bigger turbos deserves to have their dsm privileges revoked. The more boost you're running and more air you're flowing the more exhaust gas is created, therefore you need to get a bigger gate to safely alleviate the excess gas. If a gate is used that's too small you'll get too much gas still going through the turbine which has a compounding effect and continues to build more boost, the more boost you build the more gas goes back through the turbine... it's a vicious circle of engine destroying pressure. ON that note I AM running a tial 38 on my agp rs65 (gt35 wheel), however when I up it to big boost levels (>30 psi) I'm going to go to a 44.

 

[Eagle 5]

Maybe I worded it wrong but I didn't say a smaller wastegate is needed on larger turbos. I said a smaller gate is needed for higher boost levels. Ya for large turbos you will still need a large wastegate, th size of the wastegate needed depends on what boost levels you are running and with what turbo.

That explain what I was saying earlier any better?

 

[Mark S.]

no... you're still wrong. even for higher boost levels you need a larger wastegate... that's why mitsu internal gates start to creep when you raise the boost. Let me break it down for you like this. The more power you plan on making, whether it be through a larger turbo or more boost on a smaller turbo the bigger wg you'll need.

 

[tstkl]

mitsu internal gates start to creep once the restriction on the gases passing through the turbine wheel becomes less than the restriction on the gasses attempting to make a 90 degree turn into the wastegate opening, which is still blocked by the flapper because it doesn't open fully. Mitsu wastegates suck PERIOD.

the reason why higher boost require smaller wastegates is COMPLETELY logical. The turbine wheel is spinning at a higher rpm to create the higher boost level desired. This means there is more friction on the shaft, and more exhaust gases should be directed toward the turbine wheel rather than around it. As boost increases, so does internal friction and the need for a larger percentage of the exhaust gases to be directed towards the turbine wheel.


I still will be making the personal choice of going with a decent sized wastegate, because I like running low boost around town and stuff.

 

[Boosted98gsx]

Alright i'm just gonna throw a TiAl 44mm on there just to be sure I can run daily drivable levels of boost.

You guys honestly dont need to go over the theory 20 times in the same thread.

 

[Slippi84]

no... you're still wrong. even for higher boost levels you need a larger wastegate... that's why mitsu internal gates start to creep when you raise the boost. Let me break it down for you like this. The more power you plan on making, whether it be through a larger turbo or more boost on a smaller turbo the bigger wg you'll need.

Wrong he's right I know several guys that ran 60-1's and bigger on 38mm externals off the mani. You know the reason this was ok because they ran no less than 20psi daily. By the way 60-1 was the smalllest turbo of the guys I have in mind the largest was a t67 just so you don't come back with well my rs65 is bigger and flows more than a 60-1.


You can regulate plenty of exhaust gasses with a 38mm wastegate you just have to place it either off a runner or even better the collector.

 

[Eagle 5]

Wrong he's right I know several guys that ran 60-1's and bigger on 38mm externals off the mani. You know the reason this was ok because they ran no less than 20psi daily. By the way 60-1 was the smalllest turbo of the guys I have in mind the largest was a t67 just so you don't come back with well my rs65 is bigger and flows more than a 60-1.


You can regulate plenty of exhaust gasses with a 38mm wastegate you just have to place it either off a runner or even better the collector.

That was another part I forget to mention was location of the wastegate as well can affect how well it works. I plan to get a 3065 with the 40mm wastegate that attaches right to the turbine housing. Everything fits well and I can run as low as 14 psi with it. Which for tuning purposes and what not would be good. I can get a good tune with it and then start upping the boost slowly etc.

 

[Mark S.]

Just because you CAN run a 38 with a big turbo and run high boost all the time doesn't make it the right way to do it. Theres still a point when you're making way too much exhaust gas for that poor little 38mm to pass and where does it go? Yup right through your turbine which has an effect of building more boost. Maybe I should tell my friend running a t04z with a hardblock and methanol that his big ass tial is the wrong way to go and instead he should really be using a old school turbonetics 35 mm gate... or hell maybe even an internal setup... that'll work quite well... What i'm basically saying is sure you can run a big turbo with a small wg... but you're a real dumb shit if you think it's the right way to do it.

 

[Kevin Jewer]

With externals it doesn't hurt to go bigger, but the WG blowing open can stillbe a problem. At any rate, you're missing the point that the size of the turbo has nothing to do with the size requirement on the wastegate. Neither does hardblock or methanol, but you don't need me to tell you that. Please read the thread again.

 

[Slippi84]

Just because you CAN run a 38 with a big turbo and run high boost all the time doesn't make it the right way to do it. Theres still a point when you're making way too much exhaust gas for that poor little 38mm to pass and where does it go? Yup right through your turbine which has an effect of building more boost. Maybe I should tell my friend running a t04z with a hardblock and methanol that his big ass tial is the wrong way to go and instead he should really be using a old school turbonetics 35 mm gate... or hell maybe even an internal setup... that'll work quite well... What i'm basically saying is sure you can run a big turbo with a small wg... but you're a real dumb shit if you think it's the right way to do it.

You are totaly right that it might not make it the totaly irght thing to do but a wastegate is to regulate boost if it does that then there is no right or wrong way and by the way I have a friend with a 700hp typhoon on internal wastegate setup just food for thought

 

[FFTEC]

I happen to run into this question with my customers all the time. The
only sure fire way to choose a wastegate size correctly is to have
tested it personally. I've done a writeup on wastegates and it just so
happens to relate to the <a href="http://www.fftec.com/articles.php?article_id=151">GT35R</a> .63 turbine housing on a 2.0L and 2.4L
with a <a href="http://www.fftec.com/articles.php?article_id=151">tial 38mm wastegate</a>. This test was done with only one variable changing and that is engine displacement both setups are equipped with 1bar wastegate springs. Any one of the highlighted test will take you to the test.<br /><br />
You should run a <a href="http://www.fftec.com/articles.php?article_id=151">44mm wastegate.</a><br />

 

[greentrbo_95gst]

I happen to run into this question with my customers all the time. The
only sure fire way to choose a wastegate size correctly is to have
tested it personally. I've done a writeup on wastegates and it just so
happens to relate to the <a href="http://www.fftec.com/articles.php?article_id=151">GT35R</a> .63 turbine housing on a 2.0L and 2.4L
with a <a href="http://www.fftec.com/articles.php?article_id=151">tial 38mm wastegate</a>. This test was done with only one variable changing and that is engine displacement both setups are equipped with 1bar wastegate springs. Any one of the highlighted test will take you to the test.<br /><br />
You should run a <a href="http://www.fftec.com/articles.php?article_id=151">44mm wastegate.</a><br />

I've had similar experience with my GT30r (4" inlet, .82 A/R) and 38mm wg. No matter how much boost the car ran it always had issues. Go bigger term relates to some of the items. Bigger is not always better; however, if ti comes to the wg get a 44mm and it will fix a lot of the tuning boost related problems.