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Old 07-15-2020, 12:33 PM   #1
volvulus
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Default D24T: Swapping Turbinehousing from 0.36 to 0.48

Right, where to start. Hello, glad I found this place!

I have a 1986 745 with VWs D24T and a Garrett 466088-1 with stock 0.42/0.36 A/R. I recently thought (long story), that the membrane of my wastegate control unit went bad and since it seemed that the membrane itself is not easily replaced, I clicked "buy now" for a unused turbine housing with an A/R of 0.48, since I didn't know what that number meant by then.

Now it has arrived and I have read into it and now I wonder, if it makes any sense at all to go the extra mile and replace the (actually perfectly fine but old'n'rusty) 0.36 housing (if removable without further damage) with the bigger one while not replacing anything else (exhaust, downpipe,...). It's a case of "now that I have bought it, I want to use it."

Problem is, I can't find any specifications about (forgive my inadequate choice of words here, no native speaker) 0.42/0.36 response rpm and at which rpm it reaches its "maximum", nor for the 0.42/0.48 combination. I understand that smaller housings kick in earlier but max out at a given rpm.

But, for every day usage (nothing crazy, no racing, no nothing, just city traffic + long distance on the Autobahn), do I ever reach the RPM at which a 0.48 housing would give me ANY benefit (more power (even if not noticable), longer life due to less backpressure, ...)

Since there were Volvos that came with a 0.42/0.48 combination, I figure that there has to be some kind of reason behind it. Maybe the one I inherited was designed to be "quick enough for stop&go in city traffic and "okay" for long-distance / Autobahn? Maybe, a 0.48 A/R turbine housing would shift this compromise more towards Autobahn and make my diesel more like an aspiration engine in lower rpm?

I really hope, my problem comes across, since this topic is new to me and I don't have all the words. So please, be gentle and kind enough to explain your turbo-slang if you should use it.

Much appreciated, cheers.
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Old 07-15-2020, 12:47 PM   #2
culberro
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Most of my experience with smaller diesel turbos is with them on Mercedes OM617 engines and VW 1.6-1.9L engines.
The "poppet" style wastegate that you have on your turbo is extremely prone to failure. Not just from the diaphragm leaking, but also from the wastegate valve getting stuck in the housing. Even after a full disassembly and rebuild, the wastegate poppet is usually bent or the stem too rough to continue to operate without sticking again... sometimes even after a few days!

I highly recommend the swing valve style of wastegate that comes on the later Garrett turbos. You can find pictures of them here: http://www.superturbodiesel.com/std/...d.php?tid=2516

To address the turbine AR question, that all has to do with how the car is driven. I really like the larger AR turbine housings (0.48 T3) even on the smaller Vw 1.6 engines. There might be a time to boost delay of a 100-200 RPM with the larger AR, but the mid and top end power is substantially improved.
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Old 07-15-2020, 01:15 PM   #3
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Thanks culberro, I'll look into the swing valves. Thing is, the poppet-one is the one I got, it is unused and will probably and hopefully outlive my > 500.000 kilometers car - although the ZF22 transmission has been replaced recently and the engine has been changed at around 450k, where a ~178k engine was put in.

With all that said, I'd like to keep the costs low.

Back to turbine housing: Thanks for your experience and estimation! The car is driven carefully. No kickdowns, nothing life-threatening, really. Me and my brother share it when in town for everyday business and when hitting home, which is a 400km ride. So mostly city traffic and patient long distance cruising at around 2.500-3.000 R/min, being our "top end". If our "top end" however doesn't even reach the midrange you're talking about, I see no point in biting my teeth on the rusty connection between turbinehousing and trunk group (that's what google translate calls it).
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Old 07-15-2020, 02:07 PM   #4
dl242gt
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Use the .48 new stuff. Messing with the old stuff is not good. The change before boost onset won't be bad and the engine mid power and top power as on highway cruising will be better. Plus with the better flow it won't retain as much heat so it'll probably last a bit longer.

To change only the turbine housing on the engine may be possible if you can get to the ring of retainer bolts. But if they are too hard to get to take the turbo off the engine.
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Old 07-15-2020, 05:04 PM   #5
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Maybe not worth the $, but of the old-skool T3 options, the cosworth .48 or ATP turbo WG housing with a larger downpipe, while it requires some modification/alternate downpipe / downpipe connection is more reliable, spools faster and flows better than that miserable poppet-style WG .36 the D24T cars came with.

Service easier with a band clamp stud-less/gasketless connection too.

Cheaper than a newer/faster spooling turbo in some ways to stick with the old design T3, but doesn't perform as well as more modern turbos.

I found the cosworth .63 turbine housing spooled about as fast as the regular vol-void swing valve .48, not sure if a cosworth gas-car application .48 would be comparable in a diesel application to the .36...
At least the gas car casting/app better of the exhaust housings would likely last more or less indefinitely on the average diesel temp EGT...probably...
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Old 07-15-2020, 05:23 PM   #6
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Quote:
Originally Posted by volvulus View Post
Thanks culberro, I'll look into the swing valves. Thing is, the poppet-one is the one I got, it is unused and will probably and hopefully outlive my > 500.000 kilometers car - although the ZF22 transmission has been replaced recently and the engine has been changed at around 450k, where a ~178k engine was put in.

With all that said, I'd like to keep the costs low.

Back to turbine housing: Thanks for your experience and estimation! The car is driven carefully. No kickdowns, nothing life-threatening, really. Me and my brother share it when in town for everyday business and when hitting home, which is a 400km ride. So mostly city traffic and patient long distance cruising at around 2.500-3.000 R/min, being our "top end". If our "top end" however doesn't even reach the midrange you're talking about, I see no point in biting my teeth on the rusty connection between turbinehousing and trunk group (that's what google translate calls it).
By "trunk group" do you mean the exhaust pipe between turbo and muffler (commonly called a "down pipe), or the manifold between the cylinder head and the turbo?

A 2.5"/63mm exhaust pipe after the turbo is about the minimum of what you would want.

With the rev limit of smaller deisel engines being pretty high (5000R/min for the D24), you should be running a larger turbine housing. It'll make everything happy at highway speed. Less heat, cooler air from the turbo.. all meaning more power with less stress on the engine.

For reference, a 0.48 AR Garrett from a OM617 was making ~5psi of boost on a vw 1.6L diesel while going down the flat highway. The stock KKK turbo (very small) had to make ~10psi of boost at the same speed.

A chinese/ebay T3 turbo with a 0.48 housing and swing valve wastegate should be an easy and cheap upgrade for your car. Though I'm not sure what modifications you can legally do.
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Old 07-15-2020, 06:22 PM   #7
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I use the .48 cosworth housing on my T3 in the 82 turbo. When I installed it at first I thought everything was the same. Full boost at about 3500rpm. But then I noticed it had useful boost as low as 2200rpms which was much lower rpms with more torque, than it was with the stock .63 T3 swingvalve housing.
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Old 07-16-2020, 08:53 AM   #8
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Thank you all.

Quote:
Originally Posted by dl242gt View Post
To change only the turbine housing on the engine may be possible if you can get to the ring of retainer bolts. But if they are too hard to get to take the turbo off the engine.
I already managed to pull the turbo off the engine, no bolts harmed.

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Originally Posted by culberro View Post
By "trunk group" do you mean the exhaust pipe between turbo and muffler (commonly called a "down pipe), or the manifold between the cylinder head and the turbo?
Now that I am a bit deeper into the terminology, I guess I mean the center section or the CHRA. So I am struggling to pull the turbine housing from the CHRA. I already started soaking it from the exhaust side with WD40, trying to let it penetrate the heat shield, as demonstrated in this video: https://www.youtube.com/watch?v=LH748NFWfKY

What I tried then was using the old stud bolts from the T3 flange and two locked nuts with the backplate of the turbo as an abutment (?) to press the two parts apart. It's not easy though since whatever I am using as a wedge between the backplate and the nuts is rotated away when unscrewing the bolts. Do you get the picture?

Note: one site has moved slightly already, I can tell this because the exhaust weel won't turn without touching the housing any longer, so I better get the opposite site to move next. Any advice? This technique looks a bit more sophisticated than my attempt: https://www.youtube.com/watch?v=cZczKlXkJZ0

I have no ability to heat it thoroughly, what I could try is freezing it with a couple of hits with lighter gas, which worked brilliantly on the stud bolts. But it already moved, so I guess I'm getting there.

Quote:
Originally Posted by dl242gt View Post
I use the .48 cosworth housing on my T3 in the 82 turbo. When I installed it at first I thought everything was the same. Full boost at about 3500rpm. But then I noticed it had useful boost as low as 2200rpms which was much lower rpms with more torque, than it was with the stock .63 T3 swingvalve housing.
Another point for the .48 housing, onset at around 2200 would be acceptable, I guess at the moment it should be around 1800..


Edit: Question: Besides, are all the relevant bolts & nuts standard or is there anything metric on Garretts? Might be the age&wear on the stud bolts, but they went in a little bit harder into the threads of the connecting bolts (housing/CHRA).

Last edited by volvulus; 07-16-2020 at 09:05 AM..
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Old 07-16-2020, 04:48 PM   #9
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I use a 3lb sledge hammer to remove the housing. I literally had the beat it off. Plus you still have to be careful of the turbine wheel. But so far I've used the hammer to remove a couple. I moved hammering it from side to side so it would come off some what evenly.

You'll be fine with the boost onset. Your engine has much higher compression, six cylinders, and a bit more cc. Swing valve actuator just requires a bracket to bolt on the compressor side. You may need a couple of slightly longer bolts on the ring of bolts for the compressor side to bolt on the actuator bracket. Find a port on the intake manifold to connect the hose from the actuator.
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Old 07-28-2020, 05:54 AM   #10
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Hello there, it's me again. I want to thank you all for contributing to this thread so far.

I failed to remove the housing from the CHRA with the mini-press method (see above videos) because the aluminum compressor plate ripped apart as I had no chance to place the mini-press elswhere. So, new OEM CHRA has arrived and I will connect the .048 turbine housing with the new CHRA and the old compressor housing.

Let's talk about pressure control for a minute, yes? I can't really get my head around the schematics of how this is realized in my wagon. I'll describe the old configuration:

1. Intake (before compression):
a) main intake coming from filter,
b) another intake coming from the crankcase ventilation,
c) a third coming from the intake manifolds pressure control/relief valve.
Inside the compressor, still before compression, there's
d) a small hose going to the wastegate actuator.


Image: upper hose = 1.d), lower hose = 2.a)

2. Intake (after compression):
a) a small hose leading towards the wastegate actuator,
b) output towards the intake manifold.

3. Intake manifold:
a) outouts to the cylinders, obviously,
b) output to the pressure control/relief valve and
c) a small output to the injection pump control.


Now, my new setup has no 1.d) which to my understanding provides negative (edit: may be atmospheric pressure as well) pressure on the wastegate actuator membrane, since it is in front of the compressor. This connection may have two functions (please tell me if I'm wrong/correct with either one of them):

a) it prevents the wastegate from opening too early as the spring may already give way slightly to small pressure (not fully open though)
b) it helps closing the wastegate faster when boost pressure drops by bringing the membrane into resting position (what would this be good for?)
c) both apply.

The question that came up is: since my new setup lacks the connection 1.d) towards the wastegate actuator, because the new wastegate actuator (0.48 turbine housing) has no such thang, does that mean that (depending on spring load) the actuator may open the wastegate earlier compared to my original (now broken) setup?

Now, note that the pressure control/relief valve has no exclusive connection to the wastegate actuator, so the pressure at 3.b) and 2.a) should always be the same as they share the pressure from the intake manifold / compressor output.

Now, what does the pressure control/relief valve actually do? From what I've read about it (albeit not concerning a D24T), it shall prevent pressure buildup at the wastegate actuator membrane so that boost pressure can build up until a certain pressure is reached, or am I confusing different approaches of pressure control here?

From what I've read, this prevention is realized by opening the control valve and thus draining pressure from the intake manifold "back" to in front of the compressor (1.c)). But if that's true, then how on earth shall boost pressure ever be increased unless the valve is closed? And when does it close and why (eletromagnetically controlled, my guess is by the ECU, if my 700 has one). And when both the pressure control/relief valve and the wastegate actuartor share the same pressure, then why do we need both of them in the first place?

Somebody please? I'm a bit lost. My only concern is, that with my new setup, I'll add a misconfiguration to the pressure control system.

Cheers.

Last edited by volvulus; 07-28-2020 at 06:46 AM.. Reason: adding image for clarification, corrected order of paragraphs for better understanding
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Old 07-28-2020, 03:10 PM   #11
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Quote:
Originally Posted by volvulus View Post
From what I've read, this prevention is realized by opening the control valve and thus draining pressure from the intake manifold "back" to in front of the compressor (1.c)). But if that's true, then how on earth shall boost pressure ever be increased unless the valve is closed? And when does it close and why (eletromagnetically controlled, my guess is by the ECU, if my 700 has one).
Nope. No ECU on your D24T 700. Did you see any control wires to the valve?


What was the original problem you are trying to solve?
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Old 07-28-2020, 04:12 PM   #12
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Originally Posted by volvulus View Post
Somebody please? I'm a bit lost. My only concern is, that with my new setup, I'll add a misconfiguration to the pressure control system.

Cheers.
The pre-turbo hose (1d) is used to reference post air filter pressure. This keeps the turbo from having issues if you have a really dirty air filter. It's common on industrial diesel engines. This is the first time I've seen it on a car.

You just need to attach the 2a hose from the positive pressure side of the turbo to the actuator, this is just as it was before.

Leave the 1d connection on the actuator without a hose on it, and without a plug or cover.
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Old 07-28-2020, 04:15 PM   #13
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Go D24T.com to find out about alllll D24T tunings
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Old 07-29-2020, 03:26 AM   #14
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Originally Posted by tintintin View Post
Nope. No ECU on your D24T 700. Did you see any control wires to the valve?


What was the original problem you are trying to solve?
Hello, thanks for clarification. There are wires on that valve, but I haven't traced them to their destination/origin yet. Let me get you a picture (see part no 11):



Browsing my spare-parts webshop, this part is called "boost pressure control/relief valve". But if so, how does it control boost pressure? A friend said it's most likely a security valve if my wastegate stops working. In that case, the wires may be connected to a switch which will in case of activation do something, switching on a warning light or you name it. So it does not regulate boost pressure after all perhaps.

Original problem in tldr: massive oil loss, lack of experience, lack of money to pay workshop, lots of learning by research/doing. 1. assumption the CHRA was done (which it wasn't), 2. assumption my wastegate actuator was broken, bought a new turbine housing with a larger A/R (0.48 compared to original 0.36) on ebay - when it arrived I noticed, my old actuator is still working but then I wanted to put the new housing for its minor advantages to use.

Couldn't get the CHRA off the old turbine housing though. When trying, the aluminum compressor plate suffered cracks and so the original CHRA was finally done. So I ordered an aftermarket CHRA. The new turbine housing has a different wastegate actuator with no "reference line" between actuator and post airfilter intake (see culberros post, see images in previous post).

This made me cautios if I can now simply put everything back together with the new turbine housing without re-adjusting any other part involved. Also, I wanted to test the above valve for (mal)function but couldn't quite figure out how, since I don't fully understand what it does and when it acts.

Last edited by volvulus; 07-29-2020 at 03:49 AM..
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Old 07-29-2020, 03:29 AM   #15
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Quote:
Originally Posted by culberro View Post
The pre-turbo hose (1d) is used to reference post air filter pressure. This keeps the turbo from having issues if you have a really dirty air filter. It's common on industrial diesel engines. This is the first time I've seen it on a car.
Interesting, so this should've kept my turbo from having issues, since my air filter WAS really, really dirty. Let's play this through: air filter is dirty, throughput decreases, air intake decreases, boost pressure is harder to reach and/or plateaus on a decreased level, intake will suck more air from the crankcase ventilation (hence maybe also increased oil polution in the intake system). Pressure post air filter drops, the reference line (1.d), see image in previous post) communicates this drop in pressure towards the actuator, which then in turn opens less quickly in order to establish boost pressure. sounds reasonable, if I'm not wrong. Am I?

Quote:
Originally Posted by culberro View Post
Leave the 1d connection on the actuator without a hose on it, and without a plug or cover.
It's the other way around, I'm afraid: the new actuator housing has no such connection for the reference line but my old compressor housing obviously still has, now I wonder if I should block it's opening. (No 12. in the image below). Next question is: can I somehow exchange my actuator (housings) on this turbo? I already opened the backplate of the turbine housing and can see the wastegate valve, it has a hex socket but when trying to unscrew it, it just turns endlessly in both directions. Exchanging these would enable me to keep the pressure reference functionality explained by culberro.


Last edited by volvulus; 07-29-2020 at 04:11 AM..
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Old 07-29-2020, 03:55 AM   #16
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Originally Posted by TurboDutch View Post
Go D24T.com to find out about alllll D24T tunings
Thanks, will totally check that out, too. But so far your expertise has helped a lot already!
Cheers.
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Old 07-29-2020, 09:40 AM   #17
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I don’t think you really need the reference from #12 (1.d)
Just run the boost reference from pressure side of the compressor housing to the actuator (#11, 2.a)

You are making this more complicated than it needs to be
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Old 07-29-2020, 03:02 PM   #18
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Quote:
Originally Posted by volvulus View Post
Hello, thanks for clarification. There are wires on that valve, but I haven't traced them to their destination/origin yet. Let me get you a picture (see part no 11):


That is an overboost sensor and the wires go to a simple warning light on the instrument panel. No logic circuitry involved.
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