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Helpful ReplyHot!GT4 or Tuned 718S

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ralphmusic
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2021/05/06 09:14:50 (permalink)

GT4 or Tuned 718S

With current interest in building 4.5L 981 GT4s, perhaps we should consider the much cheaper route to HP and tons of torque, the 2.5L turbo 4 engined 718 Cayman.
 
https://www.facebook.com/watch/?v=882650535269493
 
..718 s with stage 2 and individual tune is almost ready for delivery. Ehresmann GmbH decided to use a less aggressive tune because cars are prepared for track use. 

Result 
450 ps (444 hp)
550 nm (406 ft lb)

 
 

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carreraboy
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Re: GT4 or Tuned 718S 2021/05/06 09:44:53 (permalink)
PDK?

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Motorhead
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Re: GT4 or Tuned 718S 2021/05/06 11:10:07 (permalink)
That’s the great thing about turbo engines Ralph … relatively straightforward (and cheap) to tune in terms of horsepower/£. It looks as though Stage 2 is just BMC filters, a new downpipe and a custom remap?
 
From what I’ve heard the main limitation is cooling/heat dissipation? Probably more of a challenge with the mid engine layout, although the likes of McLaren, Ferrari, etc. don’t have problem, though they’ve been designed from scratch for a turbo layout.
 
Jeff

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ralphmusic
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Re: GT4 or Tuned 718S 2021/05/06 11:10:26 (permalink)
I assume those who want more power use their cars on track so PDK is more suited to track and has higher torque rating.

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ralphmusic
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Re: GT4 or Tuned 718S 2021/05/06 11:20:51 (permalink)
Motorhead
That’s the great thing about turbo engines Ralph … relatively straightforward (and cheap) to tune in terms of horsepower/£. It looks as though Stage 2 is just BMC filters, a new downpipe and a custom remap?
 
From what I’ve heard the main limitation is cooling/heat dissipation? Probably more of a challenge with the mid engine layout, although the likes of McLaren, Ferrari, etc. don’t have problem, though they’ve been designed from scratch for a turbo layout.
 
Jeff



 
Jeff,
 
The Suncoast car is having heat issues but Florida ambient temperatures much higher than Europe. Jens doesn't take his above 450PS to make them robust for intensive track use.
 
That's not to say there aren't solutions to high engine compartment temperatures, but given my issue with other peoples' rubber blocking one of the engine compartment fans, I'd add an air scoop higher up. Perhaps using one or both of the little rear compartments to feed to the engine compartment and nearby C pillar window frame for intake. It would be less disruption to the interior than the plenum induction pipes (below) that use the same C pillar frame because it would feed the front of the engine.
 


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AndrewCS
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Re: GT4 or Tuned 718S 2021/05/06 11:28:36 (permalink)
718 S ... cue Brian 
 
981 ... I believe that PARR are currently installing a 4.0l, not sure if it`s in the blue S on their site ? 
 
Porsche 981 Cayman S - GT4 Replica (parr-uk.co.uk)
post edited by AndrewCS - 2021/05/06 11:37:15

Aberdeenshire (R2) : Cayman GT4 981


Motorhead
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Re: GT4 or Tuned 718S 2021/05/06 11:37:54 (permalink)
Ralph,
 
With that RS-style engine intake arrangement, surely the side intake scoops along with suitable modified ducting could be used for engine compartment cooling?
 
Of course the set-up is very different on the F-4 turbo engine with its complex engine intake and intercooler arrangement, the latter using the LH scoop. Ducting from the C-pillar window frames could perhaps be used for engine compartment cooling though?
 
Jeff

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ralphmusic
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Re: GT4 or Tuned 718S 2021/05/06 12:57:54 (permalink)
Jeff,
 
Sorry, the Suncoast car is a 718 F4 turbo so the thought above was for engine compartment cooling, I'd leave the side intakes OEM but with Manthey or similar mesh protection. I'd not want the trunking from the illustrated car, nor would it be needed because air from C pillar intake could be ducted directly to the front of the engine compartment. 
 
NB I haven't CAD designed this!! but looks a likely solution.
 
The Bonk-run VLN/NLS race car below at a Silverstone trackday a couple of years ago is a F4 Turbo GTS and runs normal intake save for the Manthey mesh. This ran in VLN 24 hrs for 24 hrs but is stock power.
 

 
 
post edited by ralphmusic - 2021/05/06 13:00:15

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Kai
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Re: GT4 or Tuned 718S 2021/05/06 17:17:10 (permalink)
Interesting post and very much in my wheelhouse. 
I have a Cayman F4 base model - 2.0 litre turbo which I have been “improving” for some time. it Now has 400bhp and 378lb/ft and - along with some more standard upgrades - I have recently fitted the front (3rd) radiator from the GTS models to get the water/oil temps down and a water/methanol injection kit to keep the intake temps down. Previously both water and air temps had been high on track and I could feel the car reigning in power due to engine bay temps. Even a short session on the rolling road would see power dropping. 
I can confidently state that the combination of the extra rad and the water/meth kits have down wonders - last track day absolutely no problems with temps or power drop. Perhaps something to add to the discussion as I dare say the S models are very similar to mine - just a 2.5 litre and variable turbo. I’ll be interested in others’ views. 
Kai 
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Re: GT4 or Tuned 718S 2021/05/19 15:44:45 (permalink)
Kai
Interesting post and very much in my wheelhouse. 
I have a Cayman F4 base model - 2.0 litre turbo which I have been “improving” for some time. it Now has 400bhp and 378lb/ft and - along with some more standard upgrades - I have recently fitted the front (3rd) radiator from the GTS models to get the water/oil temps down and a water/methanol injection kit to keep the intake temps down. Previously both water and air temps had been high on track and I could feel the car reigning in power due to engine bay temps. Even a short session on the rolling road would see power dropping. 
I can confidently state that the combination of the extra rad and the water/meth kits have down wonders - last track day absolutely no problems with temps or power drop. Perhaps something to add to the discussion as I dare say the S models are very similar to mine - just a 2.5 litre and variable turbo. I’ll be interested in others’ views. 
Kai 



I believe the 2.5 GTS actually has a larger turbo also…… I.e. Larger than the S.
Motorhead
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Re: GT4 or Tuned 718S 2021/05/19 16:59:50 (permalink) ☄ Helpfulby TDT 2021/05/19 17:43:06
TDT 

I believe the 2.5 GTS actually has a larger turbo also…… I.e. Larger than the S.




According to R&T -
 
The Cayman GTS’s most notable trait, compared with its six-cylinder predecessor, is its immediate, abundant, and unrelenting thrust. The new car’s 2.5-liter produces 15 hp more than the four-cylinder in the current Cayman S, thanks to a revised intake duct and a larger turbocharger compressor wheel, the latter helping to raise boost pressure from 16.7 psi to 18.1.
 
Jeff

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ChrisW
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Re: GT4 or Tuned 718S 2021/05/23 23:03:38 (permalink)
Turbo tuning is almost too easy ... heat dissipation being the greatest challenge.
 
The counter argument is turbo lag and therefore power delivery linearity ...

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TDT
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Re: GT4 or Tuned 718S 2021/05/25 01:01:29 (permalink)
As Chris says, heat management is the limiting factor on tuning the 4 pot 718s… and if your upping the power and boost for track work… then you’ll quickly find that the ECU starts to really aggressively derate as those temps rise.
Biggest issue here in placement of the IC.
That said, mitigation’s exist with efficient aftermarket ICs +larger down pipes, and if you take it to some where experience with these cars in particular like Ken @ Nine Excellence, you’ll hopefully get a nice stable package.
I’ve been out in the 9e development 718S at Zandvoort a couple summers back, as it was then… bit of a revelation.
ralphmusic
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Re: GT4 or Tuned 718S 2021/05/25 07:06:25 (permalink)
Post by Jens Ehresmann:
 
"... the air intake through the side windows actually has to do with the radiator ventilation in the front bumper. The first 718 Clubsport still had normal side windows, like all the other 981/718s. During racing however, the hot brake and cooler exhaust air was drawn in from the front via the side panels, which resulted in high intake air temperatures, therefore ignition withdrawal = less power. Later came the option with the side windows and the airbox and other mapping which made it much better."
 

 
For my part (on his GT3 powered Clubsport), I have completely removed the old air ducts in the engine compartment and use the air collected from the side panels to supply or flush the engine compartment with fresh air. Suction now only takes place through the side windows. From there with 4" air ducts directly into the self-made air filter box in the rear trunk and from there with 102 mm to the suction pipe."
 
Jen's home brew kit...
  
 
 
 
Jen's kit is a solution for reducing engine compartment temperatures and throttle intake temperatures, I assume the Porsche Clubsport kit is similar in scope...
post edited by ralphmusic - 2021/05/25 07:48:47

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Motorhead
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Re: GT4 or Tuned 718S 2021/05/25 09:12:43 (permalink)
Ralph,
 
Some interesting insight there from Jens.
 
It’s impossible to tell from the Clubsport pic if the large boxes are used exclusively for engine intake filtering or if some air is bled-off for engine compartment cooling.
 
Although these mods are for the nasp engine, Jen’s mod probably could be adapted for the F-4 turbo engine to provide cooler engine intake air as well as for engine compartment cooling. The intercooler is an air-to-coolant device, but I think that the LH intake is used for the intercooler radiator and so the arrangement would benefit from a cooler air supply.
 
Jeff

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ralphmusic
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Re: GT4 or Tuned 718S 2021/05/25 11:38:12 (permalink)
The Porsche solution may well also make the side intakes engine compartment cooling only, rather than road intake and engine compartment cooling.
 
I rather like Kai's solution in post #9 above which does not seem to have got much attention. His car featured in December PP at https://live.editiondigital.com/e/20bshmmmr/december#!page108. and he discusses on-track heat in his c400hp 718 2.0L.

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997.2 Carrera GTS
Motorhead
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Re: GT4 or Tuned 718S 2021/05/25 13:09:08 (permalink)
Yes, it would make sense to use the side intakes exclusively for engine compartment cooling on the Clubsport Ralph.
 
Water/methanol injection is an old-school trick for getting more power from turbocharged engines, and I think that it’s been offered by mainstream manufacturers on occasions. Didn’t Porsche offer some sort of system on the GT2, although it may have been to spray water into the intercooler?
 
Interesting to note that Kai’s 2.0L engine runs a higher boost pressure than that of the 2.5L, which has a bigger turbo and variable inlet guide vanes. Maybe they run different compression ratios?
 
Jeff

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Brian_Innes
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Re: GT4 or Tuned 718S 2021/07/02 20:05:37 (permalink)
I've been following this thread with much interest being a former 718 2.5t owner, latterly with the superb 718 2.5t GTS.
 
Heat dissipation on the Cayman platform is a major issue with the turbo engines, especially when tuned to their true potential. As Jeff rightly pointed out in an earlier post, McLaren, Ferrari, etc, have no such problems being designed for turbo engines from the outset.
 
Tuning turbo engines is the easy bit, it's dealing with the engine compartment heat build-up and extraction that's the more challenging problem. In my experience when tracking my 718 2.5t GTS I never had any power back-off issues, even on the few warmer track days I encountered.  
 
Taking the opportunity to dispel the widely perceived view regarding turbo lag, I can unreservedly confirm that using manual shift PDK in a well practiced manner on track, absolutely zero turbo lag is evident. My 718 2.5t GTS posted a 58.76 second lap time at Knockhill in August 2019. The power delivery and flow from the turbo was smooth, instantaneous, and linear. In my humble opinion, thanks to variable vane technology working in concert with variable cam timing, turbo lag has been completely eliminated given an experienced approach to driving techniques.          
 
As R&T so aptly put it when testing the 718 Cayman 2.5t GTS......
 
According to R&T -
 
The Cayman GTS’s most notable trait, compared with its six-cylinder predecessor, is its immediate, abundant, and unrelenting thrust.
 

Brian

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