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Twin turbo 2.7 Cayman


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22 hours ago, trialsstar3 said:

My 2.7 is getting the TT treatment in the next few months. So I thought I'd start the post to document the install. 

Popped it on the dyno yesterday to get a baseline.

20220925_090003.jpg.26f8cb7ef721b7856c603f697a9ab3d7.jpg20220925_085923.jpg.fd04f3777d5fbe5451d42a3410d6b68c.jpg

 

If anyone has any upgrade suggestions they'd like to recommend I'd appreciate it. 

I'm planning on a clutch upgrade but haven't started looking yet. 

Also toying woth the idea of an aluminium flywheel.


Sounds interesting. What are the benefits of an Aluminium flywheel, and what clutch upgrade and why please?

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Hi,

Aluminium flywheel to reduce rotating mass. This will make the engine rev more freely. I'm thinking about going with the Sachs Performance clutch. This will hold more torque before slipping. 

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Is it a particular kit your going with like tpc or are you just fabbing it up yourself?

 

What turbos are you going for and any reason your wanting twins instead of a single with such limited space?

 

Ecu plans?

 

Sounds really interesting and something I'd love to have a go at in the future if i ever sell the 981.

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Had planned to fab it up using the Audi RS4 turbos and injectors then the Syvecs ECU. Got taking with another Cayman owner that put me intouch with Martin at MRN race technologies. A day or so later a plan was hatched and a 2.7 twin turbo Cayman is underway. 😁 

I'll be installing the hardware with MRN then the car will be going to their tuning partner to develop the mapping on the standard ECU. 

 

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1 hour ago, trialsstar3 said:

Had planned to fab it up using the Audi RS4 turbos and injectors then the Syvecs ECU. Got taking with another Cayman owner that put me intouch with Martin at MRN race technologies. A day or so later a plan was hatched and a 2.7 twin turbo Cayman is underway. 😁 

I'll be installing the hardware with MRN then the car will be going to their tuning partner to develop the mapping on the standard ECU. 

 

 

Guessing they'll run in parallel, one per bank? Probably simplest. And what of intercoolers, one or two of those?

 

Very interested to see how this pans out and how you manage the packaging and heat! Good luck with the project and keep us updated 😉

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I believe i saw that system or very similar on their website a few months ago when i was looking into this.  

 

Looks a neat tidy set up, 👌 

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My main questions with this conversion would be around engine longevity, thermals, and reliability. 

 

My reasoning below:

 

Longevity

The stock engine compression ratio is 11:1 and that's quite high for a turbocharged engine.

Are there any precautions (beyond retarded ignition timing and lower AFRs) to bulletproof the engine from the increased stress supplied by the turbochargers?

 

Thermals

How long until heat soak sets in and bombs IAT?  Would the car perform poorly in normal or mild traffic conditions?  The NA engine gets pretty toasty in there as little natural airflow reaches the engine bay (thus the exhaust fan).

 

Reliability

This is a brand new kit and, as such, there will inevitably be teething issues and revisions to components to solve those.  My primary area of concern would be that MRN are new on the scene and (as far as I can tell) is a one man band.  Will they stand the test of time to support this kit into the coming years?  It is extremely expensive to have another company finish someone else's bespoke work.

 

Absolutely not trying to put you off, but it's a lot of money to drop and end up unknowingly detonating your engine into oblivion.  Rebuilds are not cheap, especially those of the overstressed kind.  If MRN have already addressed these challenges, I would love to hear more.  I know they are/he is active on here.

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Hi Aaron, 

I believe the 2.7 is 11.3:1 😁

Lets look at the 991 turbo S

So stock compression ratio is 9.8:1 and stock boost is 1.2 bar (17.4 psi gauge and 32.1 psi actual) lets make the maths very simple but just to compare turbo setups 

32.1 x 9.8 = 314

Now lets do the same for the 2.7 Cayman engine with a boost pressure of 5.5 psig (20.2 psia)

20.2 x 11.3 = 228 

This is a VERY crude calculation of cylinder pressure at TDC but the fact the numbers are miles apart I have no worries about over compression of the 98 RON fuel air mix. 

I'll have to let you know how it performs thermally. But driving in traffic... You won't be under boost.

I'll be fitting knock sensors to each bank and monitoring this whilst driving or on the dyno. 

Reliability I'm not concerned in my opinion the 2.7 is bulletproof. MRN have been successfull on weaker 3.4 engine so far. I've also got a spare low milage 2.7 engine 😊 In terms of working on the in the future it'll be done by myself so not worried about having my pants pulled by other Porsche specialist.

I think the price is spot on £7k as opposed to TPCs kit costing near £15k!!!

 

 

 

 

Edited by trialsstar3
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17 hours ago, Aaron said:

 

Now you're speaking my language!  But I agree that is a very crude method for determining longevity.  It's little things like PCV possibly causing excessive oil loss, and a myriad other possibilities that also need catering that I would also be having in the back of my mind.

 

On the thermals: whilst you may not be generating intake charge, the turbines will still spin (albeit lower than enough to generate any meaningful compressor speed) generating heat; plus the parasitic loss of the turbochargers themselves, in addition to the extra load on the oil and coolant pumps.  I assume the turbochargers are engine oil and water cooled?  The engine has a lot extra to do and, meanwhile, sucking it through a significantly longer intake tract than before.

 

Under boost is a different scenario, as you'll likely be travelling faster and receiving a reasonable amount of airflow.  I don't see any challenges there.

 

I would recommend tuning WOT on the dyno, but a road tune for closed loop as that provides significantly better drivability.  Sure, you can tune each cell/torque target to MBT at each load and RPM cell/interpolation but that misses air resistance, and real airflow hitting the car.  You can usually advance a few more degrees of timing driving closed loop on the road.

 

Nonetheless, I watch your thread with eager eyes and look forward to seeing more!

All will become clear... 

Gotta love an engineering challenge... So I hope there's a few that need ironing out 🤣

In terms of tuning It won't be done using VE tables that are usual on aftermarket ECU'S.

This set-up will retain the MAF to calculate air flow and density. I'm leaving that upto Martin's Tuning partner who are leaders in their field. 

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17 minutes ago, trialsstar3 said:

All will become clear... 

Gotta love an engineering challenge... So I hope there's a few that need ironing out 🤣

In terms of tuning It won't be done using VE tables that are usual on aftermarket ECU'S.

This set-up will retain the MAF to calculate air flow and density. I'm leaving that upto Martin's Tuning partner who are leaders in their field. 

 

Then how will it be tuned?

 

As far as I understand tuning, the MAF sensor is only used as an input?  It can become the definition for load (basic pulse width map, or VE-based map), or a calculated load input (for torque based tuning).  You can use MAF, MAP, or TPS for VE tuning; you only need to specify which is defined as load on your ignition/fuel tables.  Torque based would probably be a lot better on a turbocharged engine, but I'm not sure which form of mapping the stock ECUs use, especially being NA from factory, but it's likely the same/similar ECU on the turbocharged cars.  They're an early/mid 2000s Bosch and VE was pretty common back then for OEM applications.  Most modern ECUs are now torque-based.

 

You have pulse width mapping: at x load and y RPM, open the injectors for z ms.  No one does this anymore as it's rather primitive with modern compute capabilities at hand.

 

VE mapping: at x load and y RPM, based on the defined VE value, z amount of fuel is required (injector response time is a, plus c desired pulse width = open injectors for d ms).  Specifying engine capacity, cylinders, etc to define the VE formula.

 

Torque mapping: at x load and y RPM, attempt to generate z torque dynamically controlling components within their specified parameters (max ignition timing, max injector duty cycle, max intake charge pressure, gear selector, etc).

 

If there is another form of tuning I'm not aware of, I would love to be enlightened!

 

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Humm I'll have to ask when it hits their dyno. As far I was aware on stock ECUs running MAF they avoided VE tables. 🤷‍♂️

I can't say I've ever played with mapping on OEM systems. 

Torque mapping would be ideal with a Turbo setup but would require accurate an boost controller which I don't believe is being done on this kit.... Yet. 

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Just interested in your baseline run, is 231 flywheel not pretty low for a standard ( i assume) 2.7.

 

I had thought they were 265bhp standard.

 

I know they are no spring chicken but that's quite a loss. 

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48 minutes ago, Neil_jdmr said:

Just interested in your baseline run, is 231 flywheel not pretty low for a standard ( i assume) 2.7.

 

I had thought they were 265bhp standard.

 

I know they are no spring chicken but that's quite a loss. 

Hi Neil. Standard they're 245 out the factory. So I'm down 14bhp thats using a transmission loss of 20% the best number to be looking at is at the wheels after all that's all the road is going to see. The car has an aftermarket exhaust and cotton air filter at the moment. I didn't do any runs before the items were fitted 👎. I imagine the injector spray performance is less than optimal.

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9 hours ago, trialsstar3 said:

Hi Neil. Standard they're 245 out the factory. So I'm down 14bhp thats using a transmission loss of 20% the best number to be looking at is at the wheels after all that's all the road is going to see. The car has an aftermarket exhaust and cotton air filter at the moment. I didn't do any runs before the items were fitted 👎. I imagine the injector spray performance is less than optimal.

 

I get that about the whp but at 192 it's still pretty low considering 20% is generous trans loss percentage .  The only reason i highlighted it was just incase there was an issue before you start running boost through it. 

 

Anyway please do keep the pics coming and brace for the mucho questions. 

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