boost source Size Garrett gt28 gen2

[timmy94]

Tried to make 1/8npt threads into compressor house of the turbo for my EBC. Threads got fu#ked and ended up with and elongated hole, so I do have good amount and nice threads 90% of the hole but 10% I only had 1-2threads there and rest of it is flush on that side of the hole..

So my idea is to do M12 x 1.25 to AN4 with braided lines instead of 1/8npt to 4mm vacuum silicone hose. 
and hopefully get a better thread.

M12 is quite big and AN4 is a little bit bigger than 4mm (4.9mm inner diameter braided PTFE hose).

but this should work. Thoughts?

Otherwise I will weld and adapter onto the turbo. 

 

Edited August 13 by timmy94

[GTSBoy]

If there's enough meat in the housing where you want to put the M12 adapter, then do it, but be aware that if/when you f**k that up you'll probably be repairing it before doing anything else.

I'd just drill it out and tap ina 1/4" thread. No need for rocket surgery when the next most obvious thing will do. You could throw a 1/4 x 1/8 bush in there and use the same fitting you intended to use.

[timmy94]

3 hours ago, GTSBoy said:

If there's enough meat in the housing where you want to put the M12 adapter, then do it, but be aware that if/when you f**k that up you'll probably be repairing it before doing anything else.

I'd just drill it out and tap ina 1/4" thread. No need for rocket surgery when the next most obvious thing will do. You could throw a 1/4 x 1/8 bush in there and use the same fitting you intended to use.

ok.

Yea, then I would need to remove the turbo and weld an adapter on to it instead, if I fuc* this one up.

 

[TurboTapin]

11 hours ago, timmy94 said:

ok.

Yea, then I would need to remove the turbo and weld an adapter on to it instead, if I fuc* this one up.

 

You just need to remove the compressor housing, not the entire turbo. I would not be drilling and tapping anything with the housing still on anyways. 

[timmy94]

6 hours ago, TurboTapin said:

You just need to remove the compressor housing, not the entire turbo. I would not be drilling and tapping anything with the housing still on anyways. 

Impossible to remove the housing while turbo is installed on the manifold on the engine. So I have to do it anyways. I plugged it so there will not be any debris in there. Will vacuum aswell 

[TurboTapin]

15 hours ago, timmy94 said:

Impossible to remove the housing while turbo is installed on the manifold on the engine. So I have to do it anyways. I plugged it so there will not be any debris in there. Will vacuum aswell 

I'm surprised to hear that, but then again, I haven't dealt with a low mount turbo in years. I'm presuming it's a space restriction issue. Cheers!

[timmy94]

On 15/8/2025 at 2:05 PM, TurboTapin said:

I'm surprised to hear that, but then again, I haven't dealt with a low mount turbo in years. I'm presuming it's a space restriction issue. Cheers!

Probably gonna remove manifold and turbo. I’m not sure if I can get M12 x 1.5 air tight. Could use high temp Loctite 246 or something similar, but I don’t know. Maybe it’s just best to remove everything again and weld an 1/8NPT on there instead.

[MBS206]

3 hours ago, timmy94 said:

Probably gonna remove manifold and turbo. I’m not sure if I can get M12 x 1.5 air tight. Could use high temp Loctite 246 or something similar, but I don’t know. Maybe it’s just best to remove everything again and weld an 1/8NPT on there instead.

Why are you so adamant on going M12?

Why not follow Brad (GTSBoy) suggestion.

You're talking moving from a 1/8" size, to a 1/2" effectively. 4 times bigger. Why skip the commonly available sizes in between?

The bigger you go, the more likely you are to strip the threads out at a later date, as guaranteed, someone will put a huge spanner on the M12 and really tighten it up, and you're only in thin wall, so not a lot of threads to engage!

[timmy94]

2 hours ago, MBS206 said:

Why are you so adamant on going M12?

Why not follow Brad (GTSBoy) suggestion.

You're talking moving from a 1/8" size, to a 1/2" effectively. 4 times bigger. Why skip the commonly available sizes in between?

The bigger you go, the more likely you are to strip the threads out at a later date, as guaranteed, someone will put a huge spanner on the M12 and really tighten it up, and you're only in thin wall, so not a lot of threads to engage!

1/8NPT drill size = 8.7mm. Since the hole got messed up by me, it’s probably around 9mm. 
 

So 1/4” NPT would be next step. A drill size of around 11mm would be preferred there which is not way of my M12 (drill 10.5mm and tap M12 threads) 

[Dose Pipe Sutututu]

Just throwing around ideas, does it need to be in the compressor cover?

Why not the hot side piping?

[GTSBoy]

On 14/08/2025 at 9:20 AM, GTSBoy said:

You could throw a 1/4 x 1/8 bush in there and use the same fitting you intended to use.

Because pipe threads for pipe things. M threads for bolt things.

Throw some teflon sealant onto it and dust your hands off knowing you did the right thing, instead of going twice around the block to achieve a result using the wrong things.

Of course, all of these solutions are ignoring the fact that the minimum thread pitch we're talking about here is 1.25mm, with the 1/4" in NPT or BPS being out around 1.4mm. You will need to know that the boss you're tapping has enough thickness for at least a few threads. That's one of the reasons that 1/8" is commonly used - because the pitch is <1mm.

And why would you look to use 1/4" NPT in a BSP country anyway? Ugh.

[timmy94]

10 hours ago, GTSBoy said:

Because pipe threads for pipe things. M threads for bolt things.

Throw some teflon sealant onto it and dust your hands off knowing you did the right thing, instead of going twice around the block to achieve a result using the wrong things.

Of course, all of these solutions are ignoring the fact that the minimum thread pitch we're talking about here is 1.25mm, with the 1/4" in NPT or BPS being out around 1.4mm. You will need to know that the boss you're tapping has enough thickness for at least a few threads. That's one of the reasons that 1/8" is commonly used - because the pitch is <1mm.

And why would you look to use 1/4" NPT in a BSP country anyway? Ugh.

So M12 and sealant should be fine? 
 

NPT ” because that’s what I had and what I could get atm. 

[timmy94]

10 hours ago, GTSBoy said:

Because pipe threads for pipe things. M threads for bolt things.

Throw some teflon sealant onto it and dust your hands off knowing you did the right thing, instead of going twice around the block to achieve a result using the wrong things.

Of course, all of these solutions are ignoring the fact that the minimum thread pitch we're talking about here is 1.25mm, with the 1/4" in NPT or BPS being out around 1.4mm. You will need to know that the boss you're tapping has enough thickness for at least a few threads. That's one of the reasons that 1/8" is commonly used - because the pitch is <1mm.

And why would you look to use 1/4" NPT in a BSP country anyway? Ugh.

I do have loctite 243 and 246 and a few more models. I could drill it now in place and make new threads for m12 and order an4 - m12 coupling and fit that to the turbo. Run a braided hose to the EBC which I could get a an4 to 1/8npt 

[timmy94]

11 hours ago, GTSBoy said:

Because pipe threads for pipe things. M threads for bolt things.

Throw some teflon sealant onto it and dust your hands off knowing you did the right thing, instead of going twice around the block to achieve a result using the wrong things.

Of course, all of these solutions are ignoring the fact that the minimum thread pitch we're talking about here is 1.25mm, with the 1/4" in NPT or BPS being out around 1.4mm. You will need to know that the boss you're tapping has enough thickness for at least a few threads. That's one of the reasons that 1/8" is commonly used - because the pitch is <1mm.

And why would you look to use 1/4" NPT in a BSP country anyway? Ugh.

I also used NP

 

12 hours ago, Dose Pipe Sutututu said:

Just throwing around ideas, does it need to be in the compressor cover?

Why not the hot side piping?

That’s were it’s seems to be the best place to fit it? All schematic shows also that it’s should be referenced from the turbo housing. But idk, I do see high hp cars without any connection or anything to their turbos, so I really don’t know how they connect their things

[GTSBoy]

29 minutes ago, timmy94 said:

That’s were it’s seems to be the best place to fit it? All schematic shows also that it’s should be referenced from the turbo housing.

Totally equivalent. Stock often goes from the comp cover because that's where the actuator is also installed and the factory needs 2" of hose to make the connection - and it comes as a pre-assembled unit.

29 minutes ago, timmy94 said:

But idk, I do see high hp cars without any connection or anything to their turbos, so I really don’t know how they connect their things

They totally have a boost reference from somewhere between the turbo and the throttle(s).

36 minutes ago, timmy94 said:

So M12 and sealant should be fine? 

Oh, jeez. Just do it in M12 then. We don't actually care that much. I would expect any such AN converter fitting to rely on an o-ring or some other seal onto a flat surface under the flange of the hex**, because bolt threads are no intended to provide a pressure seal. unlike..... pipe threads.

**which also requires a suitably flat and smooth surface on the turbo's boss to provide the seal.

[TurboTapin]

On 17/08/2025 at 6:51 AM, timmy94 said:

So M12 and sealant should be fine? 
 

NPT ” because that’s what I had and what I could get atm. 

No M12 and sealant will not be fine. Use NPT like everyone including GTSBoy keeps saying. 

[GTSBoy]

14 minutes ago, TurboTapin said:

Use NPT like everyone including GTSBoy keeps saying.

Well, actually I would appreciate it if the car world could get away from using that terrible North American thread form, and use BSP. But yes. Pipe thread all the way.

Point of order - the Japanese do NOT use NPT. Their pipe threads are The Japanese thread form, which is same same to BSP.

[TurboTapin]

1 hour ago, GTSBoy said:

Well, actually I would appreciate it if the car world could get away from using that terrible North American thread form, and use BSP. But yes. Pipe thread all the way.

Point of order - the Japanese do NOT use NPT. Their pipe threads are The Japanese thread form, which is same same to BSP.

I live in Quebec. Our license plate slogan is "Je me souviens" Translated is "We will remember" as a reminder to when England conquered us and that we must never forget what they did. Long story short, BSP is unheard of here due to being an English design.

I'm surprised our nazi anti english government office the OQLF hasn't kicked in my door yet just talking about it, yet alone imperial anything. 

 

 

 

[GTSBoy]

25 minutes ago, TurboTapin said:

Long story short, BSP is unheard of here due to being an English design.

No. BSP lost to the cultural/technical imperialism of living next to Trumpistan. Face it, Robertson screws were better and still pretty much lost out to the yank stuff.

The Europeans hate the Brits and they don't use NPT. NPT is just as "imperial" as BSP is, being based on those useless inch thingos. Just done differently. 

[TurboTapin]

Just now, GTSBoy said:

No. BSP lost to the cultural/technical imperialism of living next to Trumpistan. Face it, Robertson screws were better and still pretty much lost out to the yank stuff.

The Europeans hate the Brits and they don't use NPT. NPT is just as "imperial" as BSP is, being based on those useless inch thingos. Just done differently. 

Robertson was a Canadian inventor, and it absolutely reigns supreme here. 95% of our screws are Roberston. It's literally the only option you can buy off store shelves. What would it have lost out too? I believe it's also very popular in the US. 

My reference to imperial was pointed to both NPT and BSP.