wantboost

iTrader: (2)

Ok so we all know there are two popular styles of ported shroud compressor housings

"Bullet" drilled style. used mostly on Precision and Turbonetics turbos, Optional on a few Garrett housings. Holes can be drilled straight or at an angle. Also offered by ATP



Shown above on an "S" 6262 cover



Shown above on a Garrett TO4S cover. Offered by ATP as an option on some housings



Turbonetics' "Twisted" style

Then there's the popular Garrett "GT30R" style. I call it this because it became popular due to it's use on the GT30R turbo.



Shown above on a TO4S GT3582 cover



Shown above on a TO4E GT3076R (GT30R) cover


Similar style on a Precision 76HPS cover

so my question is which one performs better? I've heard arguments as to the pros and cons of each design but I've never seen any solid data, it has mostly been personal opinion.

The reason I'm asking is mostly I'm curious (as are a few others from what I gather) but also I'm about to swap to a ported shroud cover on one of my turbos and can have either style machined into the housing.

TIA

wantboost

iTrader: (2)

Another question is regarding the groove placement. on some turbos I see them level with or right below the primary impeller blades, on others level with or below the secondary impeller blades, or inbetween the two in the middle of the gap.

why do different companies place the groove in different locations on different compressor wheels? I know there's a science to it but I've seen two different covers place the groove in two different places on the same compressor wheel.

shawty22

I have a precision bullet compressor housing. I've noticed that you get a little turbo chatter when hitting lower boost, 2-5psi. Once I get up to 5-10+ psi you can really hear the ported housing work along with the BOV.

My buddy has the garret style on his 35r and from driving next to it, it seems to perform the same. Chatters a little on low boost but once you start building more the ported housing seems to work along with the BOV.

I am kind of interested in the science behind it. But from my expierence I've never had an issue, my buddy hasn't either.

wantboost

iTrader: (2)

Yea I mean if these companies are using these designs then I would imagine they have to work.

I've heard such theories as the Garrett style works better because it allows for more low pressure behind the groove and the air has a shorter distance to travel to be recycled... to the precision style doesn't perform as well because of the size of the holes to how far the air has to travel...

all of this has been personal opinion and conjecture though.

I do know why ported shrouds are used, like I said I'm just wondering why the grooves are located in different positions in relation to the compressor wheel.

it's only 65 bucks to have the bullet drilled style done on the housing I'm looking at, haven't inquired about the cost of the Garrett style.

I would imagine that given more machine setup and cycle time is needed that it would cost more, of course I can always bribe the head machinist at the machine shop I used to work at to do it lol

Dark_Teg

All a ported shroud does is widen the operating range. The Precision looks like its made that way for a bling factor. The garret design looks the most functional but that just my uneducated opinion.

wantboost

iTrader: (2)

Yea that's what a lot of other people have said, again however, if each design didn't work they wouldn't be utilized... at least that's what makes sense

I know about the wider operating range, what baffles me is how each company puts the Map Width Enhancement Groove "MWE" (Holset lingo but the best way to describe its purpose) is located in different locations.


I can't recall what brand or size turbo it was but it had two different ported shroud cover options, a T04E and a TO4S.. each housing had the MWE groove at a different point on the compressor wheel.

this is mostly what I'm interested about knowing, I'm wondering if the placement difference between certain housings and wheel sizes has to do with how much air the engineers want to bypass through the groove... I would ***-u-me that a groove placed lower on the wheel (in relation to the vertical plane) would allow for a higher bypass ratio

Dark_Teg

I would imagine moving the "MWE" moves the surge line on the map.

92cxyd

HE351ve turbos have very similar style to Precision 76HPS cover but with a silencer ring on it.
It barks when I have supercharge engaged and I let let go of the throttle.
Never notice a difference between styles except they help with surge.

tepid1

The bullet style housing you speak of is complete junk. It doesn't work nearly as well as the Garrett style ported housing. There are many tests out there do back this up. Do some searching and it's not that hard to find.

The whole purpose is to prevent surge. Some need to let more air out than others, hence the different placement.

TheShodan

iTrader: (14)

I know it always winds up being me, you, Tony the Tiger and a couple of others that will respond to this, but really its a matter of different styles of performing the same job.. preventing compressor reversion. So, for the purpose of this discussion we will use the measurement of theoretical "better" by simply looking at the inlet's ability to prevent reversion. I'm only basing my knowledge on personal experience in slight differences in power and inducer inlet temperatures. that's it. Outside of that, its a matter of preference, cost and availability.

This style is easier (less expense and less labor-intensive) than removing a portion of the housing cast and customizing a lower level shroud into the inducer. It functions minimally, but the problem is consistency in the drill process in some models. In some instances, the drilled portions don't reach the inducer bleed groove or go all the way through to the other side of the inducer portion of the housing, so its not nearly as effective overall.

Its also quieter than what the standard cast ported shrouds that Garrett uses. this is why you see the M24 and M33 casting numbers. Different material so that the ported shroud is cast into the housing itself. (this is also why its used more in the ball-bearing series for Garrett than the T-series that's converted.

GTK version was a bit more consistent (Its Turbonetics, they have the facilities to cast it more consistently) So, I'm less worried about that option. Its now a standard on the GTK but not the others. Notice I said "consistent". Doesn't mean "better"

That's an unmachined .60A/R standard GT30R. You can tell from the fact that they didn't machine the inner lip of the compressor inlet right by the compressor wheel. They just decided not to show the real image, that's all. But I see what you're saying.

That's the newer design Precision compressor wheel using an older style Ported shroud. We've found that this version of ported shroud encounter's a bit less turbulence than the standard ones used by Garrett now. About as much as 15whp gain when using the one that everyone likes on the standard GT3582R styles.


For example.


That's what is considered standard Ported shroud used by the GT3582R from Garrett from most stock. (This one has a GT3584R in this now)..



Notice how the secondary part of the splitter blade is just underneath the inducer bleed groove. You want to make sure that if doing a custom housing fitment with different wheels you give yourself no more than .65mm over the inducer bleed groove, or you basically eliminate the purpose of the ported shroud if using a splitter blade wheel. With the newer GTX 11 bladed single-blade styles, you get a bit more room from the splitter blade, but you still want to not cross over if you can help it.

Here's what the standard shroud on the GT3582R was around 2004, and what some of the designers are going back to, because there was less turbulence at higher boost pressures with this style. The change in pressure cavitation was a little higher with the newer units (even though they looked cooler) than with these circa 2004 units. This style was now machined in, and not part of the cast, so they are a bit more expensive to do as an aftermarket option than the previous.





Looks a little familiar with the newer Precision ones, yes?

The newer larger compressors use this style a lot more now, than the GT3582R version, now people are going back to the 2005 model because the lower amount of turbulence.



Here's a situation in which I was a little off my game here getting things to fit.
This one (below) was at the limit when this was utilizing an older Mark I Reaper compressor wheel into a GT3076R housing. There were no ill-effects according to the dyno for peak power, but after about 26psi of boost, I did notice that inlet temperatures were a few degrees higher than I would have liked (about 10-15 degree average with just a laser temperature gun). Midrange power was up, but top end power was down after 28psi-31psi of boost pressure. I think it was starting to show signs of reversion at that point because of the interference of the inducer bleed groove.




I think all-in-all its more of how the creator of the turbocharger views its particular use. Even though the differences are subtle, they can be a variant when it comes to durable construction, its more of preference now than anything else. But that's just how I see it.

TheShodan

iTrader: (14)

Same terminology that Borg-Warner uses. Just another word for inducer bleed groove.. Just sexier.

TheShodan

iTrader: (14)

That's not the type of surge it was really intended for: it was more for when the turbocharger is operating outside its normal efficiency range (more like the far right of a compressor map) when the compressor wheel has reached a hypersonic speed. It does do some prevention of air inlet surge from say, an under-operating BOV, but the "chatter" that you and your buddy are experiencing are simply the BOVs operating at sudden changes in vacuum to positive boost pressure. This could vary on mm/hg vacuum of the camshaft or other factors, but not from the compressor cover itself at such low levels.

But, you're right..

tepid1

Great info big daddy!

wantboost

iTrader: (2)

tepid, I searched but got nothing but typical internet forum bullshit and conjecture (we all know what that's like lol)

Mac, you basically told me what I need to know. I need to talk to you about machining a non ported shroud gt30r t04e housing for ported shroud (and some other things)... I could do it at the shop but the machines are backlogged and I don't feel like writing the program

And yea, after I looked at the pic for the 3582 I noticed it was a T04e 3076 cover... doh

riceball777

Here is my hta gt3582r

How does this style compare to the drilled style and the standard gt3076 style?




Here is my gtx3576r. Which style is better? I hear that the drilled style are the worst ones. Any truth to that?

wantboost

iTrader: (2)

Read TheShodans post, the drilled style are horrible

The first pic you posted is the best style, as it reduces turbulence at the compressor inlet among other things (covered in his post)

TheShodan

iTrader: (14)

Like I said, Riceball777. That "better" terms is really subjective. Both your HTA and your standard GTX is fine.


Standard TR3030R


TR3030R w/ machined Velocity stack shroud

wantboost

iTrader: (2)

See I want the style pictured in the last photo

I'm getting a 4" inlet t04e housing (gt30r style) machined for a 71mm wheel (2871/3071)

I already have the t04e backplate adapter... I'm testing a prototype billet 2871 replacement wheel for a company... supposedly flows 56lb/min. I know the turbine wheel will never support that power level but the company is curious. plus I'm going to cheat a little on the turbine side with ATPs "T25 Plus" housing.

Garrett T31 housing with a t25 flange, 2.5 vband outlet. still has the standard T31 volute in a .63 or .82

Turbo was free so I don't mind spending a little money on it, besides the wheel is free and it's getting VSRd.

I know the t04b housings will support decent power levels but I'm afraid on my application that making 20-25psi so low in the rpm range that I will inevitably have surge issues.

once I test the 2871 I will upgrade to something comparable to a 3076... Still aiming for midrange torque with the best response possible.

B and B

iTrader: (3)

Feels like I just tried to read a Spanish newspaper....
So much I don't know
watching Cosmos = Turbo design theory

Btw... Carl Sagan's original

wantboost

iTrader: (2)

Bahaha lol, we could start speaking in tech talk... then you'd really go wtf.

coming from running 5 axis mills and lathes, I can't imagine the work to machine a velocity stack style ported shroud into a housing... I can see the bullet style as being the easiest for obvious reasons and then the typical gt30r style being thr next easiest. it's when you start dealing with 5mm or smaller openings for the smaller ported shroud stuff that looks like a bitch.

the velocity stack style would be the hardest because you would need machine time on a lathe and a mill (4 axis at minimum, 5 axis preferred)

not to mention writing the program and setting toolpaths looks like a total bitch... since you have to leave enough material to not compromise the structural integrity of the housing or machine a hole into the volute, of course the hole, location depending, could always be welded over.

the fun part is my shaft speed sensor is going to protrude into the ported shroud area, making sealing the sensor a bitch if it's a narrow or velocity stack style housing. I guess when all else fails pack the hole full of Hondabond lol

tepid1

You shouldn't have the speed probe in the shroud area. It's better off elsewhere.

EDIT: I'll go ahead and correct myself. Technically, you mount this near and sometimes THROUGH the ported area.

wantboost

iTrader: (2)

Yea it's going to protrude through the bottom edge of the ported shroud area, at least that's according to Garretts technical drawings.

anywhere the sensor can go it will ultimately do this, at least on Garretts drawing for the GT30R style 4" inlet T04E housing.

My Holset has the sensor in the CHRA, reading a flat on the turbine shaft. I really do like this design but the CHRA was designed and cast this way, it just isn't feasible to do this to a Garrett CHRA.

Tepid, I did have a few questions for you regarding your setup in terms of your datalogging/data acquisition as well as your use of aluminum rods but for the life of me I can't remember them now lol. I'll remember them eventually.

tepid1

As for my Precision 7285 it doesn't go through the ported shroud area. Hence my initial comment. lol

I'm always here. PM me any time man. Better get that question out soon because in a couple month my son will be born and time will escape me.

TheShodan

iTrader: (14)

That's because it doesn't. Its almost a shame they would do that to a customer.

I guess I won't be seeing you again for about 6 months because of your newborn. I remember those days.

TheShodan

iTrader: (14)

Yep. This is before its converted to an HTA