Garrett GT20 Project

[306Puggy]

Hi martyn92. If I did it that way I would only have 6mm of thread holding the thing on which seems a little on the low side to me. Hence I am going to get studs sorted, gonna drop the plate and bolts off on Thursday, hopefully get pics up on Friday when I get it back :biggrin:

[Dum-Dum]

It'll hold fine as long as the bolts are sufficiently tight and have sufficient tensile strength

Bolt head is 4mm deep thread is M8. Not sure how to work out the angle though?

What is the diameter of the very widest part of the bolt head and youll be able to work it out.

basically;
diameter of top of bolt head - 8mm (for an M8 thread) = a
a/2 = x which will be the bottom side of a right angle triangle
y = 4mm which is the height of the bolt head and the vertical side of a right angle triangle
z= the 3rd side of your triangle

you need to work out the angle between x and z and this will be the angle of countersink you need.


Its maths you did in secondary school and thought youd never ever need to use for the rest of your life lol

[306Puggy]

Heh, makes sense why I don't know it lol! I am fine until anyone mentions numbers, which is why I can't make heads of tails of things like compressor maps even if I can understand the general concept of things.

As for the tensile strength of the bolts it doesn't say whether they are 8.8 10.9 at all. Well, they are actually screws, to be fair. But they are M8 screws so must be fairly beefy? They've got a phillips head anyway so I wouldn't be able to bolt them up tightly. I did ask for some M8 countersunk bolts but they only had these big screws.

Edit: If only I could have got torx or allen versions of the same screws then I wouldn't need to have had them welded in place because I would have been able to tighten them up and then bolt the plate to the mani.

[Poodle]

Don't think like that, just because its big doesnt mean it's strong. Ive sheared an m12 bolt one-handed with a 1/4" drive ratchet, and ive briefly (accidentally) put my whole weight on a single m8 bolt that was fine. Pay the extra pennies for proper, rated bolts/set screws. Those look like disc grub screw to me, which need bugger all tensile strength. If youre getting them welded in you dont need countersunk heads anyway, just grind the head off a normal bolt and weld the shaft in place.

You wont be able to thread the existing hole for your bolts anyway, as if the bolt fits through the hole now then the hole is already too big to tap for that size bolt.


EDIT: in fact pellowe will tell you all about using properly rated fixings and fittings, wont you pellowe.

[darrenjlobb]

Good work mate,

Havent had chance to read all the posts in full so not sure if you are already planning to, but if I was you, id put them counter sunkbolts in, and weld them all / grind back flush, so there effectivly just studs welded to the plate then, will make it stronger, and stop the damn things from spinning! Can put together in any oder then, whats what ive always done anyway

Dont forget to use some exhaust paste either on each surface

Good job though so far

[Scott]

That's some good progress There's some awesome advice in here as well so be sure to give everyone rep who has been helpful!

[Dum-Dum]

As for the tensile strength of the bolts it doesn't say whether they are 8.8 10.9 at all. Well, they are actually screws, to be fair. But they are M8 screws so must be fairly beefy? They've got a phillips head anyway so I wouldn't be able to bolt them up tightly. I did ask for some M8 countersunk bolts but they only had these big screws.

They are set screws mate. The difference between a set screw and a bolt is a bolt has an un-threaded length between the head and the thread whereas the set screw has thread all the way up to the head.

Tensile strength is important as some cheap bolts and set screws are made of cheese. Are they stainless or mild steel and did the packet have any numbers on it?

If I was you, id put them counter sunkbolts in, and weld them all / grind back flush, so there effectivly just studs welded to the plate then, will make it stronger, and stop the damn things from spinning! Can put together in any oder then, whats what ive always done anyway

This sounds like a good idea.

[306Puggy]

The screws are machine screws, probably the same as these ones:

http://www.ebay.co.uk/itm/Machine-Screws...4ab02104df

I was hoping to get them welded tomorrow but those were hard enough to find locally. There are some setscrews on eGay which are 10.9 rated but I want to get this thing welded up tomorrow so I can get on with clocking it. Not sure what to do now :/

Thanks for all the really great advice!

Edit: Just found these in screwfix:

http://www.screwfix.com/p/socket-counter...tAodpVMAqw#

I can see that it says 10.9 as well :d

Edit 2: Can't find them in 30mm though

[Dum-Dum]

If your definately gonna get them welded you want to speak to your welder before getting stainless screws for your mild steel plate.

[306Puggy]

Hmm...looks like I might have to get some regular M8 bolts then. I tried screwfix and toolstation for countersunk M8 30mm bolts and they didn't have them anyway.

[Matt]

Looking good mate, any more pictures? Going to have a good read of this later

[306Puggy]

Right, last update until next week. Dropped the plate off at the welders today to get the studs welded. In the end I sacked off the set screws and got some regular M8 30mm long 8.8 tensile strength bolts. He said to expect it done on Monday so there won't be anything until then. He did seem quite confused by my intentions though.

I also clocked it today which was literally a case of loosening the bolts and then turning the compressor housing with my hand. Being quite a new turbo, there was no rust or difficulty at all.

You can now see that the turbo is in relatively the right position compared to the exhaust flange:



One question, should I tighten all the bolts once I have set it up on the manifold or should I leave all but one slack so that once I get it on the engine I can have room for adjustment? Would there be enough access down the back of an XUD block to retighten the bolts? There are 5 around the circumference of the compressor housing. Also, would I need some form of high temperate thread tight on the bolts as well? It is one thing to simply tighten up bolts but to apply thread tight would make it impossible I think.

Edit:

Also found this blank off plate for the specific engine that this turbo is off (Vauxhall z20) but it is a bit pricey:

http://www.ebay.co.uk/itm/Forge-Turbo-Re...20d48b60b4

But considering I got the turbo for £65 pounds it might be worth it? Or would it be cheaper to have one fabricated?

[Dum-Dum]

Clocking looks spot on mate, there wont be space to tighten it on the car but you could fit, chack/adjust then pull it off again to tighten the bolts.


As for the recirc id just make a plate, you still got that 6mm plate aint you.

[306Puggy]

I used the 6mm plate for the adapter plate lol! Do I need thread tight on the compressor housing bolts though?

[cwspellowe]

Thread lock? Wouldn't hurt. Just make sure you get them all tight enough that the housing doesn't have any chance of moving, but DON'T overtighten them as its an ally housing and will strip the threads making a life a total PITA.

Clocking looks to be off though tbh. The face of the manifold sits at roughly 30degrees from vertical, so as it is your compressor outlet will be pointing straight at the bulkhead. Depending on the size of the housing you may be ok, you'll probably find you need to rotate the outlet a bit more to the left (as you look at that picture)

8.8 bolts will be fine, they won't be under a huge amount of tension, not like wheel bolts or suspension parts. You're only bolting a few kilos onto a flat face. If you want to go overboard you can get gasket sheet you can cut to fit your mating faces but as Darren's said, slap some exhaust paste around it and you'll be grand.

Forgive me if i've missed this though, but what elbow are you using? For your sake I really hope you aren't using a 306 elbow? You want a nice fat elbow onto the downpipe or you'll really hold the turbo's flow back.

[306Puggy]

Heh, no I was already warned about the 306 elbow being too restrictive. The exhaust outlet is 3 inches in diameter but it doesn't have a flat surface to mate to?

See what I mean?

[Piggy]

use the original gt2052 elbow...slice/cut off the flange and have a new elbow and down pipe with flex made up from that flange

[Dum-Dum]

Again make a plate for it then get a 3" 90* elbow welded on or even better a 3" V-band connector so you can get the angle perfect on the car.

[306Puggy]

use the original gt2052 elbow...slice/cut off the flange and have a new elbow and down pipe with flex made up from that flange

Not sure where to find one? I was hoping to use some standard 3 inch exhaust pipe but I am intrigued by the idea of using the original elbow for it. I have searched eGay for "Garrett gt2052 exhaust elbow" but it shows exhaust elbows for Renault 5 turbos!

Searched for "Garrett exhaust elbow" as well but none of them are the right fit.

Again make a plate for it then get a 3" 90* elbow welded on or even better a 3" V-band connector so you can get the angle perfect on the car.

That is a really good idea about the V clamp! Thank you.

[Dum-Dum]

One of the reasons people have been using Mercedes turbo as their outlet is almost identical to a 3" v band fitting

[306Puggy]

Heh, this are the things you find out as a project goes along

Edit: Just reading this yank off road forum, post number 17 says not to use a 3 inch exhaust elbow pipe? Says the turbo needs a bit of back pressure? Would you guys agree?

http://forum.ih8mud.com/diesel-tech-24-v...er-3b.html

[Poodle]

I can't think of any scientific reason for a turbo to need back pressure, no.

[Dum-Dum]

Nope the engine needs a little back pressure which the turbo gives it. The turbo doesn't need back pressure so a 3" down pipe will be fine. You'll want to drop to 2.5" or 2.25" as there really isn't alot of space for a 3" system under the 306 although it is possible.

[Stephen]

My exhaust is 3'' straight through and it's fine

[Piggy]

I would think 3" is a bit large for the application, and could be costly.

2.25"/2.5" is plenty

[Dum-Dum]

Yeah 3" is a definite price hike over 2.5"

[Jonny81191]

3" pipe just cost me best part of £150 including a backbox. Gotta weld it all now

[Dum-Dum]

£150 is about what I paid for the bits for my 3" system on the black one. 3 x 45* bends, 1m straight and a box from Ashley

[306Puggy]

Right then, time for an update! Good and bad news I'm afraid

Firstly, got my adapter plate back from the welding bloke. Really nice job if I may say so myself!





Also made up the first blanking plate for the recirculation system with the offcut from the adapter plate:



In situ:



Marking out the template for the blank off for the actual valve:



Not cut it yet, gonna invest in a decent hacksaw!

But wait, what is that? There's a problem in the engine room captain!

Looks okay, doesn't it?



Except for the fact that it's on the piss:



This is going to make lining up the downpipe nigh on impossible, so I will need to put the adapter plate on the piss on the mani to get the turbo straight. Bit of a bodge

The reason I couldn't line the turbo up by measuring is because it didn't have a straight edge anywhere on the exhaust inlet flange, so I had to do it by eye. It looked okay at the time!

Does anyone have any suggestions how I could measure the new holes for the mani to make the turbo straight? If I do it by eye again the turbo might still be on the piss, then I will have to start from square one with a new adapter plate! And it was all going so well...

[Tom]

For the exhaust downpipe you might be best getting the turbo fitted and running then drive to your welder and get them to tack up the exhaust on the car that way you know it will be perfect. I done like you and made a plate on the bench then made the downpipe on the bench and when you think about it with all the angles involved you have a slim chance of getting it to fit without it on the car :p Just my 2p