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Garrett Internal Gate

Don Dada

By Don Dada,
in Engines & Forced Induction

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R31Nismoid Grand Master

R31Nismoid

Posted
Posted

I was going to say 28mm :rofl:

Near enough!

I cant remember 100% but i think someone here got it machined out to around a 32-34mm size and them changed the flapper as it wasn't sealing perfectly.

Was a while ago now, i'll have a search later and see if i can find something. I can't remember for the life of me who it was at present

hypergear Grand Master

hypergear

Posted
Posted

The bigger the hole is. The harder it is to hold boost up the top. Best to not drill it out too much. Most Garrett IW housings had the hole match machined refer to the CHRA at the sort of perfect size.

hypergear Grand Master

hypergear

Posted
Posted

well force = Pressure x area

Means there is greater force transferred to the actuator while its trying to pull the wastegate flapper shut.

So at high RPMs back pressure over comes actuator's spring load and force the gate open it self.

Once that happens you will have a boost drop. and that is not due to boost controller.

How ever on the other hand the turbo will boost unlimitedly if wastegate whole is too small. So best is to run a external gate. Lot better boost control, and steady power to red line.

I'm currently working on a project, which allows screamer pipe to plum back into certain area of the turbine housing. So we can have a externally gated turbo that bolton without any modifications to dump pipe or manifold.

R31Nismoid Grand Master

R31Nismoid

Posted
Posted

Ye ok so force = P x A

However with...

1x heavy duty actuator

1x upgraded flapper

1x decent EBC to aid in control and

1x correctly set pre-load...

I'm really not seeing how this would be a major problem for a GT30 internally gated (with some porting should someone so like to do so). It certainly was not a problem for the user who ported their int gate (still looking for the thread)

You are already bleeding air as well to control boost so there is not the absolute max pressure being realised either.

The only time i've heard of internal gates blowing open was on the GCG OP6 hi-flows, and the reason for this was not supplying an upgraded actuator and preload being poor.

Meaning the gate was flapping open before boost was even being created and thus resulting in boost coming on around 4500rpm give/take.

ANYWAY - A proper Garrett IW rear does not need porting.

In my searching for the porter... i found a person i'd forgotten... Darren has GT35, 350rwkw if memory serves me correct... internally gated, don't get much better

http://www.skylinesaustralia.com/forums/Ga...porting+turbine

http://www.skylinesaustralia.com/forums/Gt...porting+turbine (last post)

QWK32 Veteran

QWK32

Posted
Posted (edited)
GT35's are 32mm

correction, 36mm. i checked lol.

on the topic of wastegate sizing, even porting it out to 38-40mm, surely this wouldn't cause an issue with top or low down boost control? aren't most external gates that are recommended around that size anyway? i can however understand the theory behind going too big on the port size of the wastegate, in either blowing open early or "bouncing" when first opening.

Edited by QWK32
R31Nismoid Grand Master

R31Nismoid

Posted
Posted

The internal and external gates do operate a tad differently with regards to how they open.

Only is like a door hinge, one is pure up/down valve.

So ye, you could see some issues in that regard once open you have a lot of force on the outside side of the flapper (int gate), where external is far more distributed/uniform

tridentt150v Grand Master

tridentt150v

Posted
Posted

also, if you think about it, one becomes a straight through tunnel with no restriction, in the other the air has to flow around the poppet valve and stem. Looking at both designs, an external wastegate is always a bit larger [they generally start at 38mm] because it has to overcome more turbulence. Just looking at the wastegates, not how the air gets there or what happens once it passes through the wastegate. No proof, just my thoughts??

discopotato03 Grand Master

discopotato03

Posted
Posted

Strictly from an actuators point of view the larger the diameter of the can/diaphragm/spring the better .

Note how external wastegates are generally not small in this area .

Also as mentioned the external has no swing valve arm to multiply force against the actuator .

A lot depends on boost and exhaust manifold pressures , if the exhaust (turbine inlet) pressure rises markedly faster than boost pressure then the pressure/area force eventually overcomes the waste gate actuator and forces it to open . Its trying very hard to tell you that the system is not running in regulation . Just another indicator that high boost pressure does not guarantee reliable high horsepower .

A .

Don Dada Mentor

Don Dada

Posted
  • Author
Posted

Just wanted to know as a reference really......

So many ppl are getting probs with boost control i just wanted to know what was the average size of the internal gate and if using an ext 38mm will still be too small and cause creep

As mention before we know ext gates are more efficient because of its larger diaphragm, ability to change springs,valve type etc. but i think factors like exhaust manifold pressure,type of manifold and turbine a/r also has a significant part to play when it comes to boost control

So i don't believe the concept that if Fred gets good results using a 38mm ext gate that means Larry will have good results too using a 38mm ext gate even though they are using the same specd turbo on the same engine but on different manifolds, have different dia exhaust, same type but different sized a/r turbine etc. etc...

And for sake of this discussion lets use........and u guessed it........ the Gt3076 :)

R31Nismoid Grand Master

R31Nismoid

Posted
Posted

Well the example of Darren's car, making over 300rwkw, with a larger GT35... would all seem to point it should be OK.

What most people have drama's with is when they go with Garrett housings, but machined ones - not the ones designed for the turbo in quesiton.

The GT30-IW rears so far all seem to be fine, same as the GT35 ones.

limpus Mentor

limpus

Posted
Posted
Well the example of Darren's car, making over 300rwkw, with a larger GT35... would all seem to point it should be OK.

What most people have drama's with is when they go with Garrett housings, but machined ones - not the ones designed for the turbo in quesiton.

The GT30-IW rears so far all seem to be fine, same as the GT35 ones.

That was what i was lead to believe too until i went with a GT3076R 0.82 IW on my 2JZ...boost crept up to 18psi by redline...2 dump pipe designs and 1 slightly restrictive catback later...i finally managed to get it to settle at 16.5psi at redline...

limpus Mentor

limpus

Posted
Posted
You are talking about a factory 3 Liter engine there and a 0.82 A/R GT30 turbine housing is not big by 3L standards .

Rather than me guessing where did in come on boost with the 2JZ . May have been a case for the larger 1.06 A/R GT30 IW housing .

A .

That is true...and i remember us speaking about it too...however the rb30det boys seem to run the same turbo without much hassles...if anything they had issues with the standard actuator not holding boost...

On the 2J it made 18psi by 3200rpm with the 0.82 rear...i did consider the 1.06 at one point but the issue seems to be under control now...

Don Dada Mentor

Don Dada

Posted
  • Author
Posted
What most people have drama's with is when they don't go with Garrett housings, but machined ones - not the ones designed for the turbo in quesiton.

The GT30-IW rears so far all seem to be fine, same as the GT35 ones.

I think u left out a word there....

I wouldn't say that is entirely true however.... kinda which made me start this topic in the first place

This was posted in a thread recently

http://www.nissansilvia.com/forums/index.p...t=270&fcat=

100% Garrett....ext gated, and still having creep issues

Not sure what size the turbine a/r is tho.....

R31Nismoid Grand Master

R31Nismoid

Posted
Posted

Reads ok to me...

Just because a car has gate creep, does not mean its the housing. Infact that's pretty much the late port of call in my book (if its the correct housing)

Likely too soft of a spring/actutor, poor manifold design and similar issues.

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