924Board.org

[Mike9311]

Depends and I am looking into this option already but local to us. By "us", local to you and I

The company I am approaching first can do both and were involved in a 718 rocket engine printing study. It looks like there would be some post process heat treatment and machining which I could handle no problem. So I hope to figure out with them what makes the most sense economically (printing a prototype or going with investment casting from the start)

As for the scan... Scans are typically not complete meaning they have holes and sometimes blemishes/artifacts. I am using the scan to generate a CAD model and will also find out how this model needs to be configured for whatever process is chosen.

There is a lot going on behind the scenes on this project and a few others

Also glad you got Dan's car. I actually drove it once and considered buying it as well. Love the 80 931
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1980 931 since 1989
1981 Ideola 931 Club Sport
1982 931 Entwicklungsfahrzeug
1979 924 NA ohne 650 mit 471
1982 931 Red Resurrection - 951 IC
1982 931 parts car / resurrection?
1980 924 NA (R&D lightweight)
1982 931 wana-be GTR race car

[jacobroufa]

Gotcha, definitely understand. It's so cool that things like this are in the works on a platform that most people don't even know about! Thanks for your effort!

[Mike9311]

Was off this particular project for a bit in favor of other 924 related work

The CAD model is almost done. Scan is laid on top of the CAD model in this pic.

In some cases the original housing might have a plane or hole slightly off axis so I will adjust the 'normal' of a plane or hole axis to favor a major axis. I am doing this to make machining easier in the end. This is why you see part of the model dominate over the scan and visa versa. (see the flange surface)

I know I haven't posted much lately. Just wanted you guys to know I am still on this and other things


_________________
1980 931 since 1989
1981 Ideola 931 Club Sport
1982 931 Entwicklungsfahrzeug
1979 924 NA ohne 650 mit 471
1982 931 Red Resurrection - 951 IC
1982 931 parts car / resurrection?
1980 924 NA (R&D lightweight)
1982 931 wana-be GTR race car

[Mike9311]

Here i am checking the deviation of my scan to CAD process. I can adjust the tolerance if I think its critical


_________________
1980 931 since 1989
1981 Ideola 931 Club Sport
1982 931 Entwicklungsfahrzeug
1979 924 NA ohne 650 mit 471
1982 931 Red Resurrection - 951 IC
1982 931 parts car / resurrection?
1980 924 NA (R&D lightweight)
1982 931 wana-be GTR race car

[Cedric]

This is a great project, I hope you will pull this through, if you want i can take a look at the tongue section of the turbine housing, just to see how it looks today and if there is any thing you can do to reduce the cracking. Its a common area on a turbine housing to crack, and we worked alot with Holset and Garett to get this right (at my job) when new housings were designed.
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1980 924 Turbo
www.instagram.com/garagecedric/

[Mike9311]

Nothing is finalized just yet but you and I are on the same page. I have been trying to find pictures of that area on modern turbos. Found a few but most marketing material doesn't concentrate on that spot. Thanks for putting a name to it too, its perfect

That area gets thinned out too much on the 4.10. Its not as bad on the 6.10 but it didn't need to be

I'll post a picture of a cross section when I get a chance. There is room there to round that area off
_________________
1980 931 since 1989
1981 Ideola 931 Club Sport
1982 931 Entwicklungsfahrzeug
1979 924 NA ohne 650 mit 471
1982 931 Red Resurrection - 951 IC
1982 931 parts car / resurrection?
1980 924 NA (R&D lightweight)
1982 931 wana-be GTR race car

[Mike9311]

This one I was looking at seems knife edged too. I was thinking more rounded off and filleted



Edit: cross section of scan and cad by the tongue. In reality there is room here for a nicer fillet. (also room for 8.10 or twin scroll but that bridge is miles away)


_________________
1980 931 since 1989
1981 Ideola 931 Club Sport
1982 931 Entwicklungsfahrzeug
1979 924 NA ohne 650 mit 471
1982 931 Red Resurrection - 951 IC
1982 931 parts car / resurrection?
1980 924 NA (R&D lightweight)
1982 931 wana-be GTR race car

[Cedric]

Its a tricky area to get right, sometimes its better to have thinner material in the tounge, so the crack propagates into it instead of out to the housing as we have today.

On that housing it looks machined, pretty similarly to our housings. It kinda is impossible not to have it machined, when you do the machining for the turbine wheel it gets machined at the same time, because you cant cast the tounge with enough precision to have it very close to the wheel. You will loose turbine efficiency if you arent close with the tounge, so its a tricky situation. Radius from the tounge out the sides towrds the walls are also something you can adjust a bit.

Otherwise its something in the casting or heat treatment process that is the issue with our housings. Or a material upgrade to get better durability. We already have a really really good NiResist D5S material in the turbine housing, which is proper high grade for cast irons. If we would like something better it would be some kind of cast steel like HK30, hard to cast but even better high temp properties.

I wonder why there is a step in the turbine outlet (appart from the groove for the gasket ring). It would be best to have a smooth passage over to the downpipe if possible.
_________________
1980 924 Turbo
www.instagram.com/garagecedric/

[Mike9311]

Thanks Cedric

When its closer to the finish line I'll show you how it looks. I like the part about controlled crack propagation and especially the part about efficiency. That part for sure I didn't know so I was just trying to look at as many modern examples. A few years back I was looking at possibly making a manifold as well and HK30 showed up in my research. Haven't picked a material yet but your input will help for sure

Recently I had to analyze why a machine frame component kept cracking under repeated stress reversal and failed repair attempts. Before I looked at it, the customer kept welding additional bracing to the original piece but cracks kept forming. It turns out it was their material, combined with poor welding and the lack weld post treatment. We cleaned everything, drilled holes at the end of the cracks, and re-welded. The important part came next. We then cleaned up the welds (especially the root areas) and peened everything, putting it all into compression.

I am wondering now if shot peening would help us here. Never thought of it for exhaust components but it should be the same
_________________
1980 931 since 1989
1981 Ideola 931 Club Sport
1982 931 Entwicklungsfahrzeug
1979 924 NA ohne 650 mit 471
1982 931 Red Resurrection - 951 IC
1982 931 parts car / resurrection?
1980 924 NA (R&D lightweight)
1982 931 wana-be GTR race car

[Mike9311]

Update: I have countless untold hours into this and sometimes I take a break for sanity's sake. However, I am tired of the cracked 4.10 collection
I have (6-7 cracked housings) and need a solution without taking my one perfect 4.10 or my one perfect 6.10

First test model has been created and for those who work with CAD, you will understand the battle when dealing with odd surfaces.

Also, thank you Cedric, you have me super deep into Tongue theory which also had me testing how true was the original 6.10's volute leading to the tongue. It isn't.

I had hoped to have a printed model for spin comparison testing this past weekend (comparing my 6.10 to an original) but I have been hard at work bringing my CAD model down from 79000+ errors to 360 errors as of this morning. Printer just doesn't like it. I am close now though. I keep dividing myself daily with an aluminum torque tube project and various other projects on the silver '82 which needs to be ready mid-April...anyway...Need to work too

Keep in mind this model does not have all the fillets yet. Only where its important


_________________
1980 931 since 1989
1981 Ideola 931 Club Sport
1982 931 Entwicklungsfahrzeug
1979 924 NA ohne 650 mit 471
1982 931 Red Resurrection - 951 IC
1982 931 parts car / resurrection?
1980 924 NA (R&D lightweight)
1982 931 wana-be GTR race car

[Fasteddie313]

Wow that looks nice!
_________________
80 Turbo - Slightly Modified

[Mike9311]

Thanks!

Another two hours on it this morning. found some errors and, like programming, corrected one and went back 300

Will update
_________________
1980 931 since 1989
1981 Ideola 931 Club Sport
1982 931 Entwicklungsfahrzeug
1979 924 NA ohne 650 mit 471
1982 931 Red Resurrection - 951 IC
1982 931 parts car / resurrection?
1980 924 NA (R&D lightweight)
1982 931 wana-be GTR race car

[Mike9311]

Literally sat on my butt all day and worked on the CAD. Soon a breakfast was done until now at almost 8 PM

Licked my issues. Printing has begun. 24 hours from now I will have it for a test fit. In plastic obviously
_________________
1980 931 since 1989
1981 Ideola 931 Club Sport
1982 931 Entwicklungsfahrzeug
1979 924 NA ohne 650 mit 471
1982 931 Red Resurrection - 951 IC
1982 931 parts car / resurrection?
1980 924 NA (R&D lightweight)
1982 931 wana-be GTR race car

[Dutch924-racer]

Fantastic work!!!
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937 trackday car
Series 2 engine
951S turbo and intercooler
Fast road camshaft
Forge recirculation valve + boost controller

[Mike9311]

Thanks!

Up to the tongue and the print looks good. Might have laid it down in a different orientation but I ran out of time last night. Just wanted to get the printer going. 11 Hours and 18 minutes left

Can't wait to test fit... This is killing me after all this work
_________________
1980 931 since 1989
1981 Ideola 931 Club Sport
1982 931 Entwicklungsfahrzeug
1979 924 NA ohne 650 mit 471
1982 931 Red Resurrection - 951 IC
1982 931 parts car / resurrection?
1980 924 NA (R&D lightweight)
1982 931 wana-be GTR race car