Show full size 924Board.org
Discussion Forum of 924.org
 
 FAQFAQ   SearchSearch   MemberlistMemberlist   UsergroupsUsergroups   RegisterRegister 
 ProfileProfile   Log in to check your private messagesLog in to check your private messages   Log inLog in 
 Technical FAQ924 FAQ (Technical)   Technical924 Technical Section   Jump to 924.org924.org   Jump to PCA 924 Registry924 Registry

ROW S2 931 reliable 300whp How is it done?

 
Post new topic   Reply to topic    924Board.org Forum Index -> 931 Discussion
View previous topic :: View next topic  
Author Message
mads_gedebuk  



Joined: 16 Sep 2009
Posts: 23
Location: Kogsbølle, Denmark

PostPosted: Wed Apr 18, 2018 8:50 pm    Post subject: ROW S2 931 reliable 300whp How is it done? Reply with quote

Hi all

While i'm waiting for my new workshop to be finished i'm starting to plan the performance upgrades i want to be done on my 931.
The goal is to make 300whp and 1100kg.

This is not a budget build(i want it to be done right) but i don't want it to get all crazy so i guess there are room for decent turbo, internals and ecu.

I'm an aircraft technician and F16 crew chief but are currently studying mechanical engineering at university. I have(well soon again) a well equipped workshop with lathe, mill, MIG and TIG.

The build limits so far:

LHD
Stock G31
EFI
Internal wastegate
Stock turbo location
FMIC placed in front lower valance(maybe air/water)
No A/C
96 octane
Street legal(Denmark)



Please only post proven ideas as i wrote, this is not a budget build, but i will not be making a test mule for the Internets enjoyment

Looking forward to hear your ideas or just linkt to build post that send me in the right direction.


/Mads

www.bruunsgarage.dk
[/img]
_________________
931 Current status: bits and pieces
Back to top
View user's profile Send private message
morghen  



Joined: 21 Jan 2005
Posts: 7832
Location: Romania

PostPosted: Wed Apr 18, 2018 10:57 pm    Post subject: Reply with quote

What do you want to use the car for? Or is it just an exercise to see a number on a dyno plot?

I used a K27/k26 hybrid turbo that gave a dramatic and impressive power delivery on the 2L S2 engine.
_________________
red 924 and not red 924
Back to top
View user's profile Send private message Visit poster's website Yahoo Messenger MSN Messenger
mads_gedebuk  



Joined: 16 Sep 2009
Posts: 23
Location: Kogsbølle, Denmark

PostPosted: Thu Apr 19, 2018 12:16 am    Post subject: Reply with quote

morghen wrote:
What do you want to use the car for? Or is it just an exercise to see a number on a dyno plot?

I used a K27/k26 hybrid turbo that gave a dramatic and impressive power delivery on the 2L S2 engine.


I want to use the car for hooning around and occasionally track day stuff. so i guess it's like a fast street car i want to build.

I have read into the K27/k26 option and my car already have something similar on it now. But i want a more modern integrated wastegate setup like some of Holset turbochargers.

I like the packaging and weight gains of the more compact turbo designs.
_________________
931 Current status: bits and pieces
Back to top
View user's profile Send private message
morghen  



Joined: 21 Jan 2005
Posts: 7832
Location: Romania

PostPosted: Thu Apr 19, 2018 12:52 am    Post subject: Reply with quote

Right, then HX35 +VEMS but I think its a very tight squeeze in the stock location...perhaps move it forward a bit...you need to do a custom manifold to benefit from the new turbo anyway.

Regarding the K27 hybrid, how similar? the different wheels and compressors make a world of difference...as well as the turbine you used and the amount of advance you run off and on boost.
I ran the smallest inlet K27 compressor and wheel with the #6 turbine and the ECU from a Carrera GT, that was quite a bit of difference to the normal turbine, car drove 265km/h but you needed to ride the boost wave to be effective.
_________________
red 924 and not red 924
Back to top
View user's profile Send private message Visit poster's website Yahoo Messenger MSN Messenger
Carrera RSR  



Joined: 08 Jan 2010
Posts: 1551
Location: Somerset, UK

PostPosted: Thu Apr 19, 2018 5:46 am    Post subject: Reply with quote

Hi Mads

One proven result for reliable 300+RWHP is a full GTS motor from Mittelmotor in Germany. Uses forged pistons 8.0:1 CR, MLS HG + ARP studs, their own head design, warmer cam, K26 26xx 6.10 turbo, GTS fuel metering and CIS..... NO EFi , GTS intake manifold, FMIC in front of the radiator, stock waste gate but circa 1.4bar I believe, stock waste gate can be made in to adjustable dual port, NO standalone ECU just a programable electronic distributor

https://www.mittelmotor.de/cms/en/4-10-rennsport

Vid of engine build and car. https://www.youtube.com/watch?v=STVYcsejP5c&t=4s

Car runs in FIA Historique racing with circa 395bhp (crank?). Came 6th or 7th behind their own 914/6 and 911 Carrera RSR's at Nurburgring last year. So proven results. Won't be cheap but looks and retains original parts and look

If I knew then what I know now, my money would be spent on their motor versus the £5k on my engine rebuild and further £2-3k on other performance enhancements under the bonnet.

Steve
_________________
1980 931 - forged pistons, Piper cam, CGT turbo, 951 ducted FMIC, custom intake, Mittelmotor dizzy & cam pulley, H&S exhaust, GAZ Gold, Fuch'ed, Quaife LSD
Now www.924board.org/viewtopic.php?t=34690
Then www.924board.org/viewtopic.php?t=31252
Back to top
View user's profile Send private message
Carrera RSR  



Joined: 08 Jan 2010
Posts: 1551
Location: Somerset, UK

PostPosted: Thu Apr 19, 2018 5:58 am    Post subject: Reply with quote

Or drop in a 2.2 5 pot AAN Audi motor for 400+bhp

https://youtu.be/UbBow08jRjY
_________________
1980 931 - forged pistons, Piper cam, CGT turbo, 951 ducted FMIC, custom intake, Mittelmotor dizzy & cam pulley, H&S exhaust, GAZ Gold, Fuch'ed, Quaife LSD
Now www.924board.org/viewtopic.php?t=34690
Then www.924board.org/viewtopic.php?t=31252
Back to top
View user's profile Send private message
Cédric  



Joined: 27 Aug 2004
Posts: 1717
Location: Sweden

PostPosted: Thu Apr 19, 2018 6:21 am    Post subject: Reply with quote

Sorry, but mittlemotors numbers are not correct, the 26xx wheels just can't flow that much, they seem to use very large corrections on the dyno numbers aswell, anyway, not a discussion for this space. Though they obviously make good power, but it isn't exactly the most simple or cheap solution.

According to my simulations a Mitsubishi td07 #7 combined with a 19t compressor should make a really nice responsive turbo for 300-340hp. The mitsus are very well regarded among us who works with this. Would try to keep it on the exhaust side for minimal exhaust manifold volume. Preferably twin scroll. Though td05 is a beter choice they are much harder to come by.

It's possible on the stock manifold aswell as Joakim has proved with almost 400hp on it,but not optimal, I think his rewelded manifold with garret flange is for sale btw, maybe the turbo aswell, would be close to bolt on.

Add a light port and cam to your list, will make it easier to get the power at the top end.
_________________
´79 924
http://www.garaget.org/show.php?car=211
´80 924 Turbo
http://www.garaget.org/?car=160275
Back to top
View user's profile Send private message MSN Messenger
Cédric  



Joined: 27 Aug 2004
Posts: 1717
Location: Sweden

PostPosted: Thu Apr 19, 2018 8:37 pm    Post subject: Reply with quote

If you can find one a TD05 16g Twin scroll turbo would be my preferred weapon of choice. The TD05 have larger wheels and better efficiency than the 04s, at a higher price point though. A well proven turbo for these kinds of power levels.

Making it twin scroll would be a preferred solution for an engine like ours with fixed cam timing. Then you will have good separation between the banks, thus low levels of residual gases in the cylinders, this will make it possible to go for much more aggressive timing. And also make it possible to use far more aggressive cams when it comes to overlap and exhaust duration. This was shown on Joakims engine, which ran much better with the TS manfold and had much lower EGTs. Its the one in the video below. Though a log TS manifold would most likely made similar results, and is much easier to build.

https://www.youtube.com/watch?v=Maae0lF1mXs

I made some simulations in the 931 model on the twin scroll subject, but i dont have the data in front of me now, i think the trends were similar to this mag tests, that was disregarding any cam or timing poissibilities.

http://dsportmag.com/the-tech/twin-scroll-vs-single-scroll-turbo-test-the-great-divide/

I would keep the standard intake manifold, not worth the work to build a different one, its pretty ok in std form

Here you can see the IC im putting in my car, it was in Joakims car before, he ran 400hp with this one, even though its not at all an optimum design, it shows there ais lots of room up front for a pretty big one.

_________________
´79 924
http://www.garaget.org/show.php?car=211
´80 924 Turbo
http://www.garaget.org/?car=160275
Back to top
View user's profile Send private message MSN Messenger
924RACR  



Joined: 29 Jul 2001
Posts: 8099
Location: Royal Oak, MI, USA

PostPosted: Thu Apr 19, 2018 11:16 pm    Post subject: intake building Reply with quote

I'm actually planning to build/mod a new intake, at some point... I have a stock 931 intake we cut the top of the plenum from. I plan to build a new plenum on the runners with the throttle up front, like the GTS, to fit well with the 951 FMIC I want to graft in.

Shouldn't be too bad, just a bunch of aluminum welding, not having to remake the runners/mounting flange...

I don't plan the turbo swap and exhaust change, at least not yet, still stock CIS for a while, so not the same power targets, however.

I've got plenty of much more powerful cars available to me, no need to make a mess of my one fun little street car to make numbers!
_________________
Vaughan Scott
Webmeister
'79 924 #77 ITB racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype
Back to top
View user's profile Send private message Send e-mail Visit poster's website
mads_gedebuk  



Joined: 16 Sep 2009
Posts: 23
Location: Kogsbølle, Denmark

PostPosted: Thu Apr 19, 2018 11:52 pm    Post subject: Reply with quote

I knew about the twin scroll so was already moving toward that direction so i guess i'm still going with the HX35...

CIS is out of the question. There are no support locally and i don't want to spend half of the building time trying to compensate for an outdated system.

AAN is also a no go, due to Danish tax. If the engine is swapped the guvernment see the car as it has lost its identity so import tax have to be paid... like 25k$

What have people done to the internals. I have been through the forum and can see that people try all sorts of combination, but what need to be done on it?

Obviously pistons but which? and how about compression ratio?
Then how about rods? are the std. forged rods adequate?
Head work? cam? solid lifters, big valves...?

I guess the list goes on...

I just want to make a good build sheet made, so i have something to work from so i can start to acquire some of the key parts.
_________________
931 Current status: bits and pieces
Back to top
View user's profile Send private message
mads_gedebuk  



Joined: 16 Sep 2009
Posts: 23
Location: Kogsbølle, Denmark

PostPosted: Fri Apr 20, 2018 12:02 am    Post subject: Reply with quote

Great idea about using the runners of the original intake manifold... I guess it could be done to resemble the CGTR intake.

I also have an aluminum foundry at home so considerate casting one myself but i would be a lot of work to get it right due to shrinkage and such plus the core would be a nightmare to make.

My daily is a 2006 Mercedes S500 so want my 931 to be the complete opposite. The S500 is really lazy and detached but obviously fast.

My turbo have to be involved but faster than the Merc therefore 1100kg and 300whp.
_________________
931 Current status: bits and pieces
Back to top
View user's profile Send private message
Cédric  



Joined: 27 Aug 2004
Posts: 1717
Location: Sweden

PostPosted: Fri Apr 20, 2018 12:32 am    Post subject: Reply with quote

Why anyone would chose a HX35 for such an application over a TD05 is puzzling.

Rods seems to hold up, at least if you keep RPMS sensible. Joakim has Verdi rods, almost half the weight of the std ones, at a cost though, i wouldnt for a 300hp car.

Forged pistons is definitely a good thing to have here, people run JE, CP, Omega etc

Is it a track car or street car? Makes a massive difference.

Dont forget about radiatior and oil cooler upgrade, which you most likely would want.
_________________
´79 924
http://www.garaget.org/show.php?car=211
´80 924 Turbo
http://www.garaget.org/?car=160275
Back to top
View user's profile Send private message MSN Messenger
mads_gedebuk  



Joined: 16 Sep 2009
Posts: 23
Location: Kogsbølle, Denmark

PostPosted: Fri Apr 20, 2018 4:14 am    Post subject: Reply with quote

As i wrote the car is just for hooning around and occasionally trackdays i like to think of it as a hot rod style 924.

It will have fibreglass panels, plastic windows and roll cage but just because i think it is cool and enjoy the engineering that goes into making it.

Concerning cooling i plan on shifting to an aluminum radiator and larger oil cooler.

Great to hear that the stock rods can are proven to hold up to that power figures!
_________________
931 Current status: bits and pieces
Back to top
View user's profile Send private message
Lau Christophersen  



Joined: 17 May 2013
Posts: 99
Location: Denmark/Copenhagen

PostPosted: Fri Apr 20, 2018 4:17 am    Post subject: Reply with quote

Hi Mads.
The internals in my engine is standard rebuild 924 N/A block with pistons, just milled 2mm down, and then the standard 931 rebuild head on top.

CR = around 8,3:1.

Then I bought a VEMS EFI setup with wasted spark from Peep(Raceboy on this forum) from Estonia.

The turbo will be placed on the drivers side of the engine, ot is a turbo from a 2,9 CRDi engine. (Cheap, maybe i will chanhe it later).

Then an alu flywheel and a pressure plate from a 911 together with a custom made friction plate. The weight of the cluth assembly is around 40 % less than original.
_________________
-76 924 (PARTS)
-77 924 (PARTS)
-77 924 converted to 924S
-79 924 Turbo Carrera GT look (PARTS).
-79 924 Turbo with VEMS and 951S suspension and brakes
-81 928S manuel +30 cm widebody kit
-82 924 (SOLD)
-83 928S auto


Last edited by Lau Christophersen on Fri Apr 20, 2018 6:32 am; edited 1 time in total
Back to top
View user's profile Send private message
Cédric  



Joined: 27 Aug 2004
Posts: 1717
Location: Sweden

PostPosted: Fri Apr 20, 2018 5:06 am    Post subject: Reply with quote

If you feel rich you can buy a GTS manifold from sweden for about 18k sek ex VAT from our rally friends

I would wait with the manifold though, far down on the list.

If i remember it I will run different intake runner length in my simulation model and you will see how we can move around the power curve. I think i have a mitsu 300hp 931 model already set up
_________________
´79 924
http://www.garaget.org/show.php?car=211
´80 924 Turbo
http://www.garaget.org/?car=160275
Back to top
View user's profile Send private message MSN Messenger
Display posts from previous:   
Post new topic   Reply to topic    924Board.org Forum Index -> 931 Discussion All times are GMT + 11 Hours
Page 1 of 1

 
Jump to:  
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 vote in polls in this forum


Powered by phpBB © 2001, 2005 phpBB Group