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WEASEL149
Joined: 19 Aug 2005
Posts: 595
Location: UK, Sheffield
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 Posted: Tue Nov 13, 2012 8:36 am Post subject: The Ultimate Turbo for the 931? |
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Hybrids, Garretts, Holsets?
Let's say you had an imaginary exhaust manifold that would take any turbo.
What is the ultimate turbo for the 2.0L engine?
What would suit the characteristics of the engine?
Something that would spool early and yet maintain power to redline?
Efficiency at very high boost?
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Grenadiers
Joined: 20 Feb 2007
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Location: Nelson, WI & Prescott, AZ
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| Posted: Tue Nov 13, 2012 9:14 am Post subject: |
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See 924 GTR.
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morghen
Joined: 21 Jan 2005
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Location: Romania
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| Posted: Tue Nov 13, 2012 7:54 pm Post subject: |
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The 997 VTG turbine controlled by a smart ECU.
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WEASEL149
Joined: 19 Aug 2005
Posts: 595
Location: UK, Sheffield
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| Posted: Tue Nov 13, 2012 7:58 pm Post subject: |
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| morghen wrote: | | The 997 VTG turbine controlled by a smart ECU. |
Yes, that would make things interesting!
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morghen
Joined: 21 Jan 2005
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Location: Romania
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| Posted: Tue Nov 13, 2012 11:51 pm Post subject: |
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coming to think about it...i'm rebuilding a 931 engine at the moment(slow project) and i know of a guy who changed his 997 vtg turbos to something bigger...i'll ask for a price.
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WEASEL149
Joined: 19 Aug 2005
Posts: 595
Location: UK, Sheffield
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| Posted: Wed Nov 14, 2012 2:44 am Post subject: |
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Yes do it, you would be the first for sure.
Alternatively, twin sequential turbo set-up?
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morghen
Joined: 21 Jan 2005
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Location: Romania
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| Posted: Wed Nov 14, 2012 3:08 am Post subject: |
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i was thinking about a twin charge setup but it would be complicated and additional weight and parts are not a good thing.
As far as the 997 turbo thing goes on....i might go that route if i get to buy VEMS. And to do that i'd have to sell my 924 CGT DITC...
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Cedric
Joined: 27 Aug 2004
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Location: Sweden
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WEASEL149
Joined: 19 Aug 2005
Posts: 595
Location: UK, Sheffield
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| Posted: Wed Nov 14, 2012 3:37 am Post subject: |
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When I get my engine back together I think I'll be happy with 250 - 325hp 
Nice choice of Turbo Cedric. That does look like it would be perfect for a modified 931.
I'll have a closer look at the compressor map later 
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WEASEL149
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morghen
Joined: 21 Jan 2005
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Location: Romania
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| Posted: Wed Nov 14, 2012 5:04 am Post subject: |
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The BorgWarner EFR turbo sounds great for a 300HP 924 
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Raceboy
Joined: 01 Mar 2004
Posts: 2327
Location: Estonia, Europe
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| Posted: Wed Nov 14, 2012 5:31 pm Post subject: |
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The best turbo for high-power, good spool setup is either 997 VGT twins or Holset HE341VE VGT turbo.
With Holset there is a controller for it and it is controllable with VEMS also after doing some programming to the firmware, though controlling 997 turbos is different and I have not yet seen anything suitable.
Also, HE341VE is MUCH cheaper than 997 turbos at the same time supporting more hp.
I was considering many-many options when choosing the turbo for my Gulf engine and my goal was that the turbo should blow enough air for 400-450 hp and have decent spool (full boost @3000-3500 rpm) and came up with HE341 (not VE which marks VGT turbine).
It is much more modern than Garret GT series (GTX is its contemporary) and costs ten times less than BW EFR.
Also, there are no turbos in the market that would beat Holset in reliability, sort of important to me.
| Grenadiers wrote: | | See 924 GTR. |
This K27/29 hybrid that GTR used is ancient and obsolete, it spooled at around 5000 rpm and was ok for Le Mans long straights with its sub-3000rpm powerband but not even worth the consideration for someone who wants some kind of usability from its 931. I had K26/28 hybrid on my Gulf and its spool was at ~4400 rpm, efficiency was mediocre at best.
Only useful for restoration or accurate replica.
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morghen
Joined: 21 Jan 2005
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Location: Romania
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| Posted: Wed Nov 14, 2012 6:19 pm Post subject: |
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Hmm...a 931 with VEMS and Holset HE341VE VGT turbo all programed nicely should be a real rocket. I wonder what would be the 0-100km/h times with a propper gearbox(say the 951S gearbox or a vw passat TDI gearbox)
ok, so i've decided..i'm selling my 937 DITC and buying VEMS
anyone want the DITC?
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Raceboy
Joined: 01 Mar 2004
Posts: 2327
Location: Estonia, Europe
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| Posted: Wed Nov 14, 2012 6:32 pm Post subject: |
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Don't just rush into it, the firmware revision to support maps for VGT turbo is in the development and not ready yet.
Also, you should build an engine block also suitable for it (with strong pistons, head studs etc). 300hp is fine for a stock engine but 450 hp is definitely not and 300 hp for HE341VE is wasting its potential.
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WEASEL149
Joined: 19 Aug 2005
Posts: 595
Location: UK, Sheffield
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| Posted: Thu Nov 15, 2012 2:53 am Post subject: |
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This is all very interesting - I'm glad I started the thread now.
When my engine is up and running again, the next step would be to look at changing exhaust/manifold and turbo so this thread is great for ideas.
It seems the best way of releasing power and retaining reliability is to 'move with the times' and take advantage of technology improvements.
I didn't realise your K28 spooled that late Raceboy, I expected it to hit full boost at 4000rpm with the #6 hotside. How large is the compressor wheel?
Regarding engine block/bottom end strength, I hope I've covered all the bases - forged pistons, ARP headstuds and con rod bolts. The con rods appear to be strong - how much power until they let go?
Regarding your inlet temps with the K28 @1.4bar - how much more boost do you think you can run with the Holset and achieve the same inlet temp?
Morghen, at what rpm did you say your K27 hit full boost, I can't remember?
Do you know anyone who has tried the VW Passat TDI gearbox in a '24? Seems a better place than a Passat for it 
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