Porsche Enthusiasts Club Forum

Hi there. I'm here because Carrera RSR pointed me towards the "Jon Mitchell Garages Performance Parts" thread.
There was an interesting discussion near the end of that thread regarding 924 Turbo modification for more power/reliability.
The 944 Turbo seems to have been covered in detail regarding mods and development but the 924 Turbo has not - probably because it is a rare car now, and also because it is undervalued (IMO).

So, I've started a new thread as Jon Mitchell suggested in the other one, to pool ideas really (hopefully radical).

My own car is an early 1979 registered series 1. I've tried my hardest not to modify it too much over the years but eventually decided that I'm never going to sell it so what the hell, bring on the mods.

The only previous mods I fitted were:-

951 intercooler
951 rear exhaust section
Wastegate running dual port with a Blitz dual solenoid boost controller.
Crankcase breathing altered, running an old Turbo Technics breather kit with an oil catch tank.
Enlarged external coolant crossover pipe with slightly altered circuit to ensure adequate coolant flow from the back of the head at all times.
33% larger rad core and 944 coolant tank.

Suspension has mild modifications:-
200lb springs at the front with the later top strut mounts.
28mm adjustable anti roll bar at the front
968 3-way 19mm anti roll at the rear.
Poly-bushed wishbones.

Brakes are 986 monoblock 4 pot calipers at the front with standard pads.
Refurbished standard calipers at the rear with green stuff pads.
Goodridge stainless brake hoses all round.

Anyway, my story started again last year after finding a pinhole leak on the headgasket that pressurised the coolant system on boost. Not only that but a cam follower and lobe on number 2 cylinder were just starting to pit slightly so I decided to pull the engine.
This is when I decided to make more mods and do it longterm rather than get it back on the road as quickly as possible. My budget is tiny so I do things bit by bit and take on the work myself along with help from my father.

Current list of intended mods and acquired parts:-

Solid cam followers and lashcaps.
Custom AGAP camshaft ground on new cam core.
Custom inlet manifold to better suit the 951 intercooler (which will also receive minor mods) using full radius velocity stacks.
ARP headstuds to replace the Raceware ones.
I was lucky enough to pick up a cheap hybrid turbo that has been rebuilt (K3T) - this is basically using stock K26 #6 hotside with K27 compressor and housing (3070 compressor wheel).
Full engine management using VEMS ECU, wasted spark and 630cc flow-matched injectors.
Alloy 911 pressure plate and new clutch.
Second-hand alloy Pace radiator.

Any discussion or suggestions and thoughts are welcomed. There are probably many people on here with much more knowledge and experience than I

There may be a few, but I will guess that youre inside the top few percent.

Id suggest removing the original ignition and fuel systems and replace them with an integrated ECU - through optimisation alone youll be able to make significant gains, never mind the increased reliability.

Id also look at the antiquated turbocharger: something newer, more spinny and water cooled would be an enormous improvement. Perhaps something like an Impreza Mitsubishi TD05 turbo - able to pump enough air for over 300bhp, cheap, reliable and cheaply rebuilt and if you have a manifold built to suit, youll cut out another 931 achilles heel too!

As a side note: I have a 944 Turbo now, bit I was looking for a 931 last year, because it was a car that Id always regarded but never owned. Reading an old 931 vs. 951 article yesterday, I found that my eyes and my interest were drawn to the 924 Turbo. I almost bought the Earl of Marchs (as he was then) 924 CGT in 2000 and I will be very surprised if I dont buy one yet.


Simon

I'd be very interested in seeing a list of modifications with pros and cons against them with proven dyno bhp results, something that is very lacking in the depth of opinions within 924 forums. Also too many diverse things to do and not do. To much hearsay on bhp results, mainly from the US which are using a detuned set up in the first place.

I installed an S2 engine into my S1 car last month. This S2 engine with DITC and a 951 IC mounted under bumper in front of the rad produced 197bhp stock S2 0.65 bar. Installed in my S1 without DITC or FMIC produced 167bhp at stock S1 0.7 bar. The next task was to plumb in my IC which is mounted under the badge panel as per 951. Alas the engine let go just 20 miles into its maiden journey so we never got to see what the IC added both at stock 0.7 bar or at 1 bar. My expectation was circa 200 - 210 bhp at 0.7 bar and circa 230bhp at 1.0 bar...... Is this realistic running the S1 turbo and S2 slightly higher compression?

Although I thoroughly understand that adding EFI etc will add more bhp and reliability, I am in some respect happy in the short term to continue with the unreliable and untuneable CIS. However when funds are available will likely add this in the mix.

So with all my three engines, 2 S1's and 1 S2, all now broken I am about to embark on a full rebuild of one engine out of the three.

So as Wes has suggested some knowledge of tuning these cars over the years would be much appreciated here if possible.

Here's how my engine looked (mid install) prior to running briefly last month. When this engine comes out again I will be repainting the engine bay properly back to Alpine White. Work to the reposition the fuel dizzy and modify intake plenum currently in hand to improve IC pipework routing.



951 IC sat in modified 951 front end installed into my 924. Looking to add extra vent in front bumper and move front number plate to increase airflow into IC

A shroud will help I think, Steve. When you increase the airflow you need to ensure that it is all directed through the core. Im not sure how to achieve the increased airflow whilst keeping the cars current stock appearance, though. If it was a competition car Id move the registration plate onto the badge panel and cut the bumper, but even if you trial this on a replacement part, itll still need a lot of finishing to look even presentable...

Every time that I see your car I regret not buying the white over red series one from Pie Performance last year (max bid £931 ). Im sorry to hear that youve had these failures as yours is probably the nicest 931 that Ive ever come across.

When rebuilding your engine I think that you must know which turbo, fuel and ignition it will run. I wouldnt mix large turbo and high compression with original S1 or S2 'management'. If you want to build an S2-ish engine then run a small turbo and S2 fuel/ignition with it, then move onto something more adequate later, would be my advice - you can then change the turbo as youll be able to fuel it properly.


Simon

I have been looking for a 951 IC bumper duct to modify to incorporate the 931 badge panel vents and the bumper vent

I won't be using the S2 DITC in my car. I may upgrade to EFI later, just can't budget for another £1k for engine management in the short term

I am not fully set on the compression ratio yet, but if I run the S2 block and head the only way to reduce the ratio is to use a thicker MLS head gasket, something Jon suggested not to do in the previous thread and stick to a stock gasket.

I would prefer to at least use the bigger S1 turbo in the build at least over the fast spin up S2, if not combine the two. I am tempted to rebuild with the S2 compressor which will spin up quicker, and the S1 turbine which will exhaust more gasses more quickly. I know the S1 turbo is more laggy, but I like it when the punch comes in at 3000 rpm.

Although I am happy to modify this car, I have a mind to upgrade as per 'factory', similar philosophy to Jons. If Porsche built a 'Clubsport' 931, what would they have done. We do have the CGT, CGTS and Clubsport as inspiration and direction. I could have bought a remanufactured CGTS intake manifold earlier this year for £1000 but was a bit rich for me.

Thanks for the comments Simon. It's a shame its not going to be on the road this Summer, but when it is back, I intend it to be worth the wait.

Oh, and another option to consider, is a warmer cam/vernier pulley going to add anything to the build?

Excellent thread topic )

I have loved the 924 Turbo my whole career. Has the potential to be a real monster.

Would you like to benefit from millions of pounds of development to tune your 924 Turbo?, well, that has already been done for you.

Take a look at the 944 Turbo, Porsche took everything they learned from the 924 Turbo, Carrera GT/S/R and fixed a few problems and pushed technology forward some. But as with any evolution, some mutations happened which brought about new problems.

Apply some of these developments to a 924 Turbo, along with the benefit of 30 years further developments in technology and you can turn a 924 turbo into a very competent contender to run rings around even a mildly tuned 944 Turbo.

The first step in advising a spec, would be to ask the budget, you can achieve anything with the right budget. The second question would be the intended use for the car... A very different approach is taken to modifying a car for track or race, compared with a car for the road or fast road.

Probably a good place to start is to outline what I would like to do with one of my less loved of my two 924 Turbo's, which I may do earlier rather than later. If someone does what I am planning, I don't mind, I would just like a little credit for the ideas, which in many cases are the result of over 20 years of pondering. Much of my ideas are based on value for money, as well as performance and also flexibility.

One problem with the 924 Turbo, that Porsche as a company suffered for, was cracked exhaust manifolds. In the 944 Turbo they chose to relocate the turbo to the other side of the engine bay, allowing the use of longer primaries than the 924 turbos stubby primaries.

What I plan on doing is just what Porsche did with the 944 turbo, relocate the turbo to the other side of the engine bay, geometrically to exactly the same location as the 944 turbo and even using a 944 Turbo crossover for roughly 80% of this part of the exhaust. This has many benefits.

One benefit is the ability to use from a wide range of Turbo's developed for the 944 turbo, from the original k26/6 (plentiful and cheap) through to many hybrids, as well as everything that has been learned about the turbo for a 944 turbo over the years, the knowledge learned from tuning 944 turbos can be scaled to the 924 turbo application.

The other benefit is being able to use a complete 944 turbo exhaust system, the back section has always worked, but with this layout you could use a complete 944 turbo exhaust and even the likes of a fabspeed 3.0 inch exhaust system. Not to mention using a wastegate designed for a 944 turbo, such as a tial 38 or 46 with the 944 adaptions.

For the head to the 944 crossover to lead to the turbo, it should be quite easy to either custom fabricate primaries and collectors to either work with a complete 944 turbo crossover, or modify it where it goes from 2 to 1, to mate to custom manifolds or even perhaps the disposable (if damaged or crack) 924 NA exhaust manifold, which could at least be used for initial development to check the viability of the idea.

One other benefit of the turbo in this location is that it makes servicing or replacement of the turbo much more simple than the 924 layout. Especially handy in development of a car.

Lastly the crossover pipe design pre turbo has benefits of exhaust flow being more continuous rather than pulsed, which is not just kinder to a turbo, but allow more to be scavenged from the thermodynamics of the turbo, as well as causing more of an extraction effect on the exhaust ports prior to valve opening. The longer the runners for a turbo, as long as heat is retained in the exhaust charge, the better... there are no real drawbacks.

Now if you are going to benefit from this relocated turbo, with the alternator put back in the same location as the 924 NA, and as many are already doing, you use the 944 turbo intercooler, in the 944 turbo location, then it is not a bad idea to use the 944 pipe layout too and from the intercooler, which then allows the use of off the peg upgrades to intercooler and pipes.

Modifying the 924 turbo intake, to have its throttle body, again a 944 turbo one, to the same location as the 944 turbo physically in the engine bay will allow you to see the benefits again of the 944 turbo evolution, it is an elegant solution, reduces sharp bends to a minimum. Redesign of the intake manifold, to provide nice long runners and a tapered plenham chamber will be a nice improvement.

Next, I would possibly recommend the complete ditching of CIS injection, we have mastered it over the years, using modifications to the WUR and fuel metering head, along with electronic adjustable fuel pressures via the WUR plumbing, can allow a certain amount of fuel curve adjustment, which can be boost sensitive. However, why not benefit from something that is cheap and completely reverse engineered. A 944 turbo DME and KLR combo with maps completely changed to make them 2.0 924 turbo specific, perhaps hand in hand with a MAF sensor replacement of the 944 turbo airflow meter and the addition of a map sensor to bring in boost sensitivity and three dimensional mapping.

You could say use a complete stand alone system, but to be honest, for my own application, I am completely familiar with the DME and KLR software, which has already been and is being modified for flexibility, supporting a 924 turbo with it, will just require a fuel rail being fabricated, the flywheel modified. Combine this with the cheap available 944 turbo DME and KLR ecu's, and you have knock detection, EFI reliability and most of all for me, 30 years of development of the ecu and software.

Just like a 944 turbo, the pre turbo intake would include a dump valve.

Add to this the knock monitoring equipment we have for the 944 turbo, for safely narrowing the safety margin between safe and detonation limits, with individual cylinder knock sensing and automatic individual cylinder retard and re-advance following an event, you can run more boost than normally safe.. this will also work with CIS, which we have been doing on 930 turbo's for a while now as well as EFI on 944, 964-2, 993 and 996 turbo's.

Transmission wise, I think I will be going for a hybrid transmission, 944 Turbo hardened 1st and 2nd, 944 S2 LSD diff in a pre 85 housing, allowing the use of the standard 944 NA rear beam and transmission crossmember. The snail shells are getting hard to get parts for, and the 944 transmission is more user friendly.. another evolution to take advantage of

Engine wise, the modifications to the 24 turbo head would be minimal, the bottom end would be given a good blueprinting and treated to a set of H-section con rods and custom forged pistons with nickel ceramic coated bores.

The cast iron block of the 924, mated to the 924 turbo head, will make for an extremely strong bottom end, which if kept away from detonation will allow some massive boost pressures to be used without issues. And before anyone starts, boost pressures do not cause head gasket failure, detonation does... manage ignition and fuelling with detonation detection and the sky is almost the limit with power.

Budget for this will not be massive, all experimental, but a guy needs a hobby.

I say this setup will work well.. We will find out later in the year )

Wow! Thanks everyone for contributing to the thread - so there are people out there that love the good old 931 as much as me

944 Man wrote:Id suggest removing the original ignition and fuel systems and replace them with an integrated ECU - through optimisation alone youll be able to make significant gains, never mind the increased reliability.

Id also look at the antiquated turbocharger: something newer, more spinny and water cooled would be an enormous improvement. Perhaps something like an Impreza Mitsubishi TD05 turbo - able to pump enough air for over 300bhp, cheap, reliable and cheaply rebuilt and if you have a manifold built to suit, youll cut out another 931 achilles heel too!

As a side note: I have a 944 Turbo now, bit I was looking for a 931 last year, because it was a car that Id always regarded but never owned. Reading an old 931 vs. 951 article yesterday, I found that my eyes and my interest were drawn to the 924 Turbo. I almost bought the Earl of Marchs (as he was then) 924 CGT in 2000 and I will be very surprised if I dont buy one yet.

Simon

Hi Simon. I am replacing the ignition and fuel systems with standalone VEMS engine management. I think with the level of boost and standard cast 7.5:1 pistons my tune needs to be spot-on to avoid detonation or the pistons will turn to jelly.
I had thought of using a modern turbo but budget won't allow it for now but it's something I intend to return to eventually. I just couldn't afford a custom exhaust manifold and modern turbo so the K26/K27 hybrid seemed a good compromise and came up just at the right time.
I love 944 Turbos but marriage would be at risk if I bought one of those as well as the 931

Carrera RSR wrote:I am not fully set on the compression ratio yet, but if I run the S2 block and head the only way to reduce the ratio is to use a thicker MLS head gasket, something Jon suggested not to do in the previous thread and stick to a stock gasket.

I would prefer to at least use the bigger S1 turbo in the build at least over the fast spin up S2, if not combine the two. I am tempted to rebuild with the S2 compressor which will spin up quicker, and the S1 turbine which will exhaust more gasses more quickly. I know the S1 turbo is more laggy, but I like it when the punch comes in at 3000 rpm.

Although I am happy to modify this car, I have a mind to upgrade as per 'factory', similar philosophy to Jons. If Porsche built a 'Clubsport' 931, what would they have done. We do have the CGT, CGTS and Clubsport as inspiration and direction. I could have bought a remanufactured CGTS intake manifold earlier this year for £1000 but was a bit rich for me.

Oh, and another option to consider, is a warmer cam/vernier pulley going to add anything to the build?

Steve, your compression will mainly be set by the pistons. If you are going custom-forged then you'll be able to specify the dish in the piston crown. The other thing that will raise CR slightly is how much your head has been skimmed.

Regarding the different K26 turbos, I would go with the S1 turbine housing (#6) to reduce back-pressure and it'll also help keep EGT's under control. The S2 compressor (2664) would be the best choice from the stock turbos as it's efficiency is better than the 2470. The 2470 compressor wheel hits peak efficiency between 3500rpm-4500rpm. It was sized okay for a standard car but increasing the boost tends to turn it into a heat pump and overspin it.
If you can find a 951 250hp turbo (the K26/8) you can bolt your S1 turbine housing to it and then you basically have a compressor wheel very close to what the 924GTS has.

The stock cam is good for up to at least 225hp, and most say it's fine up to 250hp. Above this then it's probably worth looking at but it's probably best to progress other things first IMO. In fact I agonised over whether to change the cam spec but needed a new cam anyway...

jmgarage wrote:I have loved the 924 Turbo my whole career. Has the potential to be a real monster.

Would you like to benefit from millions of pounds of development to tune your 924 Turbo?, well, that has already been done for you.

Take a look at the 944 Turbo, Porsche took everything they learned from the 924 Turbo, Carrera GT/S/R and fixed a few problems and pushed technology forward some. But as with any evolution, some mutations happened which brought about new problems.

Apply some of these developments to a 924 Turbo, along with the benefit of 30 years further developments in technology and you can turn a 924 turbo into a very competent contender to run rings around even a mildly tuned 944 Turbo.

Hi Jon. I think your ideas about using OEM 951 parts are excellent and well-conceived. In fact if I had read your ideas 12 months ago I would have probably asked for your help in possibly pursuing the same route but I have already invested a bit too much in the parts I already have.
I love your potential monster comment, that really inspires me to get mine sorted out now

jmgarage wrote:One problem with the 924 Turbo, that Porsche as a company suffered for, was cracked exhaust manifolds. In the 944 Turbo they chose to relocate the turbo to the other side of the engine bay, allowing the use of longer primaries than the 924 turbos stubby primaries.

What I plan on doing is just what Porsche did with the 944 turbo, relocate the turbo to the other side of the engine bay, geometrically to exactly the same location as the 944 turbo and even using a 944 Turbo crossover for roughly 80% of this part of the exhaust. This has many benefits.

One benefit is the ability to use from a wide range of Turbo's developed for the 944 turbo, from the original k26/6 (plentiful and cheap) through to many hybrids, as well as everything that has been learned about the turbo for a 944 turbo over the years, the knowledge learned from tuning 944 turbos can be scaled to the 924 turbo application.

The other benefit is being able to use a complete 944 turbo exhaust system, the back section has always worked, but with this layout you could use a complete 944 turbo exhaust and even the likes of a fabspeed 3.0 inch exhaust system. Not to mention using a wastegate designed for a 944 turbo, such as a tial 38 or 46 with the 944 adaptions.

I think once I have this iteration set-up with the engine management etc. I will eventually make a new exhaust manifold and move the turbo to the other side. It is after-all a PITA to mess with the turbo stuck down the side of the engine so just making it more accessible definitely appeals to me. A 3 inch exhaust system would really be nice!
I'm glad you've mentioned Tial wastegates as I'm considering getting a 38mm one. I intend to vent the wastegate straight to atmosphere via it's own small tailpipe and remove the first primary silencer from the exhaust. The idea was then to shorten the wastegate "J" pipe running from the exhaust manifold. Some of the Tial gates are very small and even have watercooling built into them plus it would be new with good parts availability.

jmgarage wrote:Next, I would possibly recommend the complete ditching of CIS injection, we have mastered it over the years, using modifications to the WUR and fuel metering head, along with electronic adjustable fuel pressures via the WUR plumbing, can allow a certain amount of fuel curve adjustment, which can be boost sensitive. However, why not benefit from something that is cheap and completely reverse engineered. A 944 turbo DME and KLR combo with maps completely changed to make them 2.0 924 turbo specific, perhaps hand in hand with a MAF sensor replacement of the 944 turbo airflow meter and the addition of a map sensor to bring in boost sensitivity and three dimensional mapping.

You could say use a complete stand alone system, but to be honest, for my own application, I am completely familiar with the DME and KLR software, which has already been and is being modified for flexibility, supporting a 924 turbo with it, will just require a fuel rail being fabricated, the flywheel modified. Combine this with the cheap available 944 turbo DME and KLR ecu's, and you have knock detection, EFI reliability and most of all for me, 30 years of development of the ecu and software.

Again, I would have considered all this before buying my standalone. Unfortunately I know nothing about the DME and KLR, especially changing the maps. I really like the individual cylinder knock sensing - this to me is the best part and really clever of Porsche considering it's 80's tech. Porsche are true pioneers with turbo tech just like Saab were back in the day with their APC system (which is also still coveted and used on other modified cars).
One question I have is, can you calibrate the knock-sensing? I know that normally knock frequency changes slightly between engines of different physical size eg.bore size and engines of different specification.
With the VEMS ECU I will have to calibrate the dual knock sensors. Normally people induce knock at a safe engine speed and record the sound through a PC soundcard so they can set the knock detection frequency to match the engine. Others have just hit the block with a large spanner and recorded the frequency

jmgarage wrote:The cast iron block of the 924, mated to the 924 turbo head, will make for an extremely strong bottom end, which if kept away from detonation will allow some massive boost pressures to be used without issues. And before anyone starts, boost pressures do not cause head gasket failure, detonation does... manage ignition and fuelling with detonation detection and the sky is almost the limit with power.

Thank god you've mentioned that - I've been banging on for ages about boost pressures not blowing headgaskets. There's been a number of europeans who've successfully run high boost (2 bar and 1.9bar). Steve Bassington ran 1.5bar+ to achieve 393hp - further optimisation would have netted him at least 420hp!
There's that guy Bruce from Bradford who runs up to 32psi using low compression VW LT van pistons and NO wastegate. He also runs 8 injectors and 2 CIS fuel distributors (nightmare!). His power must be colossal for 2.0L...

I believe the OEM cast pistons get a bit of unfair stick - any piston will die from detonation, you just have to be spot-on with the tune with cast pistons. I would run forged but can't afford it right now and my OEM pistons are mint.

Anyway I'm getting carried away now and must go for my dinner
Please keep this going everyone. The discussion is much appreciated and feeds my obsession with 931's and forced induction!

Id suggested a TD05 and a new manifold as upgrades which were potentially cheaper than original kit, although didnt know that youd already got a trick turbo... The ECU was suggested for a similar reason, as it should be a big step forward as well as being cheaper/easier (but only when the irreplaceable OEM kit failed, of course).

Id love to see Jons car finished...


Simon

Just to clear something up, the KLR from a 944 turbo does not perform knock sensing per cylinder and retard only that cylinder, that is a seperate electronic box of tricks we have.

The KLR is very cleaver though, it senses knock and has its own detonation avoidance strategies, so very impressive for its day.. we just add our electronics as "belt and braces"

Wes, have we talked before? perhaps on the 924.org forums or something? Maybe we sent you some parts? The name sounds familiar to me.

You stay with your plan though Wes, it would be boring if everyone tried the same things and no progress would be made.

My project would be a rod for my own back, none of it is super easy, but my vision is to try to build a combination of the missing link in the evolution of the 924 turbo into the 944 turbo from 1982 to 1986 and making the best use of some modern technology where it would be criminal not to.

Tial wastegates are good items, we modify and improve them for our 944 Turbo and 930 applications as well as using them on a couple of 924 turbo's.

Last year one of our 924 Carrera GT Customers asked us to improve his brakes and suspension. After a lot of talking and advising him not to do anything which could not be reversed, we modified 944 220 hubs to accept a 924 speedo drive, along with the 220 brembo calipers and 968 anti roll bars, combined with GTS Shock absorbers. We plan on doing the same with our 924 turbo project, except we may upgrade it again further to MO30 or 964 turbo front brakes as the power levels go up, possibly using a modified version of KWv3 instead of the GTS Shock absorbers.

Luckily we have a storage unit and a container full of 944 Turbo parts, so picking the parts is not a problem which is fortunate for us. We have also removed the front panel from each 944 turbo we have broken for spares in the last couple of years with 924 turbo's in mind, not to mention a couple of 924 turbo badge panels and one "new old stock" one I have been hording for a long time.

Nice to see some enthusiasm for the 924 turbo's still out there, we only modify one or two a year these days and probably have as many Carrera GT's as customers in the workshop as we do 924 Turbos, which is an indication perhaps of how rare the 924 turbo's are becoming.

Wes wrote: Steve, your compression will mainly be set by the pistons. If you are going custom-forged then you'll be able to specify the dish in the piston crown. The other thing that will raise CR slightly is how much your head has been skimmed.

Regarding the different K26 turbos, I would go with the S1 turbine housing (#6) to reduce back-pressure and it'll also help keep EGT's under control. The S2 compressor (2664) would be the best choice from the stock turbos as it's efficiency is better than the 2470. The 2470 compressor wheel hits peak efficiency between 3500rpm-4500rpm. It was sized okay for a standard car but increasing the boost tends to turn it into a heat pump and overspin it.
If you can find a 951 250hp turbo (the K26/8) you can bolt your S1 turbine housing to it and then you basically have a compressor wheel very close to what the 924GTS has.

Anyone have a 951 K26/8 turbo going for a very reasonable price? I am a poor 924 turbo owner who's been raped and pillaged heavily recently!! Consider it a donation for a very worthy cause

Thank you in advance

If you want to follow the plan set out by Wes, I guess you will mainly want a used k26/8 and will not need the turbine housing as you will be using your S1 #6 Turbine Housing.

If so, you might be in luck, when we build a typical hybrid turbo for a 944 Turbo, we prefer to use all garrett and KKK parts, in particular KKK exhaust housings as they fit the crossover and discharge pipe, even though there are available aftermarket alternatives from Turbonetics etc, as the quality of the materials is higher in the KKK item.. Unfortunately a genuine KKK exhaust turbine housing is very expensive, a couple of years ago they were £300 a pop due to the value of Nickel (as well as unofficial KKK tax) and a seasoned #8 without cracks is even better than a new one, even if we need a larger one, we have them modified.

As a result, I should have (as long as I have not binned any recently) some K26/8's, missing their exhaust turbine housings, which are just hanging around as spare cores with little value, so I would be open to offers.

As I said before.. I am almost ashamed to say I have a 40 foot container and a 800 square foot storage unit filled with 944 turbo parts alone which I should clear out... But so much of it, including turbo's missing exhaust housings eventually become very handy! lol

Hi Jon

Thanks for the offer. I have no idea what money these command as I haven't searched one out until now. If you want to PM me your expectation including postage I would be most appreciative. Thanks again

944 Man wrote:Id suggested a TD05 and a new manifold as upgrades which were potentially cheaper than original kit, although didnt know that youd already got a trick turbo... The ECU was suggested for a similar reason, as it should be a big step forward as well as being cheaper/easier (but only when the irreplaceable OEM kit failed, of course).

Id love to see Jons car finished...


Simon

To be honest I've not actually checked to see what a custom exhaust manifold would cost to have someone else make it. It is a route I'd like to explore at some point.
The Mitsubishi turbos are also something I'll have to look into, so thanks for the tips. I've also had Holset recommended - I think it was the HX30?
I do think the custom fabrication would be well worth the effort - it would potentially open up a whole new avenue of turbo choice. It's a real downer with the 931 K26 having the funny 3 bolt fixing (and also no room).

I would also love to see Jon's car finished - it would be really cool to see a build thread or something similar.

jmgarage wrote:Just to clear something up, the KLR from a 944 turbo does not perform knock sensing per cylinder and retard only that cylinder, that is a seperate electronic box of tricks we have.

Yeah, I misread your post. That does sound like a handy box of tricks and clever.

jmgarage wrote:Wes, have we talked before? perhaps on the 924.org forums or something? Maybe we sent you some parts? The name sounds familiar to me.

Yeah I'm pretty sure we talked a very long time ago on 924.org. I remember always finding your posts interesting and knowledgeable then someone spoilt it for you on there if I remember correctly?
I did spend some time away from that forum for a while myself as I got fed up with it for various reasons.

jmgarage wrote:Last year one of our 924 Carrera GT Customers asked us to improve his brakes and suspension. After a lot of talking and advising him not to do anything which could not be reversed, we modified 944 220 hubs to accept a 924 speedo drive, along with the 220 brembo calipers and 968 anti roll bars, combined with GTS Shock absorbers. We plan on doing the same with our 924 turbo project, except we may upgrade it again further to MO30 or 964 turbo front brakes as the power levels go up, possibly using a modified version of KWv3 instead of the GTS Shock absorbers.

Actually I've heard nothing but good things about the KWv3 set-ups although I suspect it's a little out of my price range, at least for now.
I've thought about losing the torsion bars and going full coilover with reinforced mounts but whether I ever get round to it I don't know. I'll probably end up going for beefier torsion bars and springs and maybe lower it slightly.

jmgarage wrote:Luckily we have a storage unit and a container full of 944 Turbo parts, so picking the parts is not a problem which is fortunate for us. We have also removed the front panel from each 944 turbo we have broken for spares in the last couple of years with 924 turbo's in mind, not to mention a couple of 924 turbo badge panels and one "new old stock" one I have been hording for a long time.

Again, if I'd known you have K26/8 turbos with missing exhaust housings I would have definitely gone for one of those. I spent a while hunting for a second-hand one but the K27 came up first.

One question I have is, what causes the back of the engine to run as hot as it does? Is it the coolant circuit that's mainly to blame or is it partially down to the design of the log exhaust manifold causing exhaust gas temps to be higher at the back?
I know Porsche had problems at Le Mans with burning out exhaust valves, to the point that they eventually had titanium valves in the 924GTR's or so I've read.
I'll be fitting a K-type EGT thermocouple and sensor but it's near the turbo.
There's a guy called Joakim (don't know his surname) who runs a Garrett GT30 on his 931. I don't know his exact spec now but in 2003 he dyno'd it and recorded 956°C at 4000rpm at full 1.55bar boost. Car went on to make 274.7kW (368hp) at 7000rpm with max torque 444Nm at 5500rpm. The car has moved on since then with ITB's and apparently leaves 911 GT3's for dead.
I've tried to go as much for thermal management as possible with mine but will be stuck with the OEM log manifold for now

So what are the implications or limitations of running boost of say 1.0 bar on my proposed set up? Are there any issues of running beyond 1.0 bar and what would be a safe limit be? What are my current watch outs before needing to take on the next upgrade path?

Carrera RSR wrote:So what are the implications or limitations of running boost of say 1.0 bar on my proposed set up? Are there any issues of running beyond 1.0 bar and what would be a safe limit be? What are my current watch outs before needing to take on the next upgrade path?

Well you have charge cooling taken care of which is a big factor. Sounds like you're already planning the ducting for it so the 951 cooler should do it's job well.

I wouldn't call the CIS unreliable, it just has to be in good operational condition. You can alter the system pressure easily enough and then there's the adjustable WUR mod which should come in useful. Don't know how much boost the standard WUR diaphragm is up to.
Actually making mods to the fuel distributor though - that's where you need someone who knows what they're doing. I personally don't think you'll need to though - it's good to fuel at least 250hp as proven by 931 and also BMW enthusiasts who've used the same 931 fuel distributor.
The CIS injectors are good for around 320hp so no probs there - it will be worth checking their spray pattern and timed fuel delivery though, just to make sure they're working properly.
You have the AFR gauge so you'll be able to make sure your fuelling is adequate on boost.

You'll be limited with the distributor-based timing. You can't get super-accurate timing with the distributor. Quite a bit of power can be gained through accurate timing - this is something I've noticed the americans over on 924.org over-looking or even dismissing it when I've mentioned it.
There are other options like Megajolt that you could look at in the future if you want to retain the CIS. At least then you can tune and build a proper timing curve to match your set-up and boost.

Bottom line is I think you'll be fine with 1 bar. Beyond that, I'm not sure. I have a feeling the fuel system is probably up to a bit more but if it was me I'd feel better having more control over the timing.