The Porsche 924 Owners Club

Dedicated to the Porsche 924
Forty Years of the Porsche 924 Turbo
It is currently Wed Feb 19, 2020 1:49 am

All times are UTC [ DST ]




Post new topic Reply to topic  [ 83 posts ]  Go to page Previous  1 ... 4, 5, 6, 7, 8, 9  Next
Author Message
 Post subject: Re: So this turned up today
PostPosted: Mon Jan 01, 2018 8:16 pm 
Offline
Club Member
User avatar

Joined: Tue Mar 21, 2017 10:01 pm
Posts: 386
Location: Sweden
Model: 924 turbo
Dyno numbers looks completely of the charts. Very unrealistic loss numbers and wheel numbers are very low, if they were in kW it would make more sense.

I don't think the torque drop is that bad at all, power is increasing all the way to 6k. Looks god for that boost level.

The biggest reason of the very pronounced drop of on turbo engines is not primarily the volumetric efficiency, even though it definitely makes it harder. The biggest reason is the turbo death spiral, the compressor efficiency goes down which in turn demands more turbine power, which creates more backpressure, and as the revs climb the worse it gets even worse since turbine efficiency will get lower due to the ever increasing PR, which in turn makes for an even more closed WG, which creates more backpressure, you get the point. That will create alot of so called pumping work for the engine and also lots of residual gas in the cylinders.

In this case i would definitely go with a size up on the turbo before cam if more power is the goal, small turbine and hot cam is a bad combination. But first of all go to a better dyno and have a good reference car with me.

Rock on, a very cool car!


Top
 Profile  
Reply with quote  
 Post subject: Re: So this turned up today
PostPosted: Tue Jan 02, 2018 10:35 am 
Offline
Club Member
User avatar

Joined: Fri Jun 20, 2008 6:51 pm
Posts: 4032
Location: Europe > Romania
Model: none
CedricN wrote:
The biggest reason is the turbo death spiral, the compressor efficiency goes down which in turn demands more turbine power, which creates more backpressure, and as the revs climb the worse it gets even worse since turbine efficiency will get lower due to the ever increasing PR, which in turn makes for an even more closed WG, which creates more backpressure, you get the point. That will create alot of so called pumping work for the engine and also lots of residual gas in the cylinders.


I have no dyno charts to back me up but What Cedric says seems right to me.
My K27 + #6 hybrid is more efficient than this turbo at about the same boost level and the push in the seat is very strong all the way up..it never tails off.
I'll have to test my new GT + billet up to that RPM in the 931 to see how it behaves.


Top
 Profile  
Reply with quote  
 Post subject: Re: So this turned up today
PostPosted: Tue Jan 02, 2018 8:39 pm 
Offline
Club Member
User avatar

Joined: Tue Mar 21, 2017 10:01 pm
Posts: 386
Location: Sweden
Model: 924 turbo
morghen wrote:
CedricN wrote:
The biggest reason is the turbo death spiral, the compressor efficiency goes down which in turn demands more turbine power, which creates more backpressure, and as the revs climb the worse it gets even worse since turbine efficiency will get lower due to the ever increasing PR, which in turn makes for an even more closed WG, which creates more backpressure, you get the point. That will create alot of so called pumping work for the engine and also lots of residual gas in the cylinders.


I have no dyno charts to back me up but What Cedric says seems right to me.
My K27 + #6 hybrid is more efficient than this turbo at about the same boost level and the push in the seat is very strong all the way up..it never tails off.
I'll have to test my new GT + billet up to that RPM in the 931 to see how it behaves.


Wheen im back at work in February i can do some simulation runs on my 931 model with different sized turbine and compressor, also cams and show how it affects performance. If anyone is interested..


Top
 Profile  
Reply with quote  
 Post subject: Re: So this turned up today
PostPosted: Tue Jan 02, 2018 9:42 pm 
Offline
Club Member
User avatar

Joined: Sat Jan 30, 2010 11:13 pm
Posts: 15872
Location: Somerset
Model: TheOnly Way Is Turbo
CedricN wrote:
If anyone is interested..


Absolutely :food:

_________________
Steve - Joined: Sat Jan 30, 2010 10:13 pm......think I have lost far too much time in this forum.........
1980 924 Turbo Series 1 - Alpine White & Guards Red
Omega forged pistons, lightened and balanced bottom end, ARP studs + Cometic MLS HG, Piper fast road cam, K27/26 3257 hybrid turbo, 951 ducted FMIC, Custom intake manifold, Mittelmotor dizzy & cam pulley, Adj boost - dyno’d at 225bhp @ 1.0bar on previous CGT turbo, Zeitronix ZT2 & Phormula KS4 knock sensor, 944 turbo all alloy radiator, Hayward & Scott custom tapered race exhaust, GAZ Gold coilovers, Fuch'ed up, Quaife LSD
2017 VW Passat Variant GTE Advance
2015 Nissan Leaf Tekna


Top
 Profile  
Reply with quote  
 Post subject: Re: So this turned up today
PostPosted: Tue Jan 02, 2018 10:20 pm 
Offline
Club Member
User avatar

Joined: Tue Mar 21, 2017 10:01 pm
Posts: 386
Location: Sweden
Model: 924 turbo
Carrera RSR wrote:
CedricN wrote:
If anyone is interested..


Absolutely :food:



Maybe ill start a wishlist when i start it up. Can start with td04 turbo, cams, manifolds etc just a matter of time and imagination :) I hope 931 modifying isn't completely dead yet, but the market doesn't help..


Top
 Profile  
Reply with quote  
 Post subject: Re: So this turned up today
PostPosted: Tue Jan 02, 2018 10:36 pm 
Offline
Club Member
User avatar

Joined: Sat Jan 30, 2010 11:13 pm
Posts: 15872
Location: Somerset
Model: TheOnly Way Is Turbo
CedricN wrote:
Carrera RSR wrote:
CedricN wrote:
If anyone is interested..


Absolutely :food:



Maybe ill start a wishlist when i start it up. Can start with td04 turbo, cams, manifolds etc just a matter of time and imagination :) I hope 931 modifying isn't completely dead yet, but the market doesn't help..


I'd love to see where the pros and cons and sweet spots are for a variety of turbos for a 924. From stock to mild and wild upgrades. You can then hopefully chose which one is best suited to your own cars. Currently too much guess work unless you go to Mittelmotor with a wad of cash as it appears they have tested a few options and know the outcomes

_________________
Steve - Joined: Sat Jan 30, 2010 10:13 pm......think I have lost far too much time in this forum.........
1980 924 Turbo Series 1 - Alpine White & Guards Red
Omega forged pistons, lightened and balanced bottom end, ARP studs + Cometic MLS HG, Piper fast road cam, K27/26 3257 hybrid turbo, 951 ducted FMIC, Custom intake manifold, Mittelmotor dizzy & cam pulley, Adj boost - dyno’d at 225bhp @ 1.0bar on previous CGT turbo, Zeitronix ZT2 & Phormula KS4 knock sensor, 944 turbo all alloy radiator, Hayward & Scott custom tapered race exhaust, GAZ Gold coilovers, Fuch'ed up, Quaife LSD
2017 VW Passat Variant GTE Advance
2015 Nissan Leaf Tekna


Top
 Profile  
Reply with quote  
 Post subject: Re: So this turned up today
PostPosted: Sun Oct 14, 2018 10:21 pm 
Offline
Club Member

Joined: Tue Jul 29, 2014 1:28 pm
Posts: 1385
Location: emsworth hampshire
Model: 924 gt 924 n/a
One year :woohoo:
Attachment:
20181003_110404.jpg
20181003_110404.jpg [ 3.49 MiB | Viewed 3269 times ]

_________________
https://porsche924.co.uk/forum/viewtopi ... 24&t=14424
https://porsche924.co.uk/forum/viewtopi ... 24&t=21262
https://porsche924.co.uk/forum/viewtopi ... 24&t=22223


Top
 Profile  
Reply with quote  
 Post subject: Re: So this turned up today
PostPosted: Sun Oct 14, 2018 10:30 pm 
Offline
Club Member
User avatar

Joined: Sat Jan 30, 2010 11:13 pm
Posts: 15872
Location: Somerset
Model: TheOnly Way Is Turbo
johnboy wrote:
One year :woohoo:
Attachment:
20181003_110404.jpg


And still one of the best, if not the best looking CGT rep :nod:

_________________
Steve - Joined: Sat Jan 30, 2010 10:13 pm......think I have lost far too much time in this forum.........
1980 924 Turbo Series 1 - Alpine White & Guards Red
Omega forged pistons, lightened and balanced bottom end, ARP studs + Cometic MLS HG, Piper fast road cam, K27/26 3257 hybrid turbo, 951 ducted FMIC, Custom intake manifold, Mittelmotor dizzy & cam pulley, Adj boost - dyno’d at 225bhp @ 1.0bar on previous CGT turbo, Zeitronix ZT2 & Phormula KS4 knock sensor, 944 turbo all alloy radiator, Hayward & Scott custom tapered race exhaust, GAZ Gold coilovers, Fuch'ed up, Quaife LSD
2017 VW Passat Variant GTE Advance
2015 Nissan Leaf Tekna


Top
 Profile  
Reply with quote  
 Post subject: Re: So this turned up today
PostPosted: Mon Oct 15, 2018 12:37 pm 
Offline

Joined: Thu Aug 16, 2018 12:13 pm
Posts: 136
Model: 996TT
Congratulations :beer:
If you get fed up with it please let me know ;-)


Top
 Profile  
Reply with quote  
 Post subject: Re: So this turned up today
PostPosted: Thu Mar 28, 2019 2:48 pm 
Offline
Club Member

Joined: Tue Jul 29, 2014 1:28 pm
Posts: 1385
Location: emsworth hampshire
Model: 924 gt 924 n/a
In theory the last time I need to get an mot so where better to get it done porsche :nod:
Attachment:
20190328_110545.jpg
20190328_110545.jpg [ 3.23 MiB | Viewed 2225 times ]

Pass :party:

_________________
https://porsche924.co.uk/forum/viewtopi ... 24&t=14424
https://porsche924.co.uk/forum/viewtopi ... 24&t=21262
https://porsche924.co.uk/forum/viewtopi ... 24&t=22223


Top
 Profile  
Reply with quote  
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 83 posts ]  Go to page Previous  1 ... 4, 5, 6, 7, 8, 9  Next

All times are UTC [ DST ]


Who is online

Users browsing this forum: No registered users and 18 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
© 2009-2019 The Porsche 924 Owners Club - Powered by phpBB