718 Cayman GT4 is here – at long last.!

[Motorhead]

Oli,

I’d agree with Dave that something’s amiss with your hill-hold function, particularly if as you say it’s not releasing smoothly. Thankfully my 987.2 has a proper handbrake and not an inaccessible push-button at knee height so I rarely make use of the facility and there’s no visual indicator that hill-hold is in operation. Have you checked that the parking brake is engaging and releasing fully by jacking each rear wheel clear of the ground? If one side is binding-up it will give you an idea where to look but if the parking brake is working correctly then it will indicate a problem with the hill-hold system which must include some sort of incline measuring sensor.

Just to add that in case you’re not aware of it, the parking brake is separate from the foot brake. The bell of the rear disc forms the drum of a leading and trailing shoe drum brake and it’s possible that some adjustment is necessary. On my 987.2 CS the adjustment is mechanical but it seems that on the 981 and most likely on your 718 the ‘air gap’ has to be set using a diagnostic tool, so I’m sure that the dealer will be doing this as a matter of course while they’re checking the hill-hold function when you take in the car later this month.

https://uk.autologic.com/news/checking-parking-brake-air-gap-on-porsche-981-models

Jeff

 

[PeterRH]

Lichfield say they have sorted the drone at low revs with their replacement back box. I am looking forward to checking their GT4 out which has it fitted and if its ok will probably have one fitted.

 

[Twinfan]

The Litchfield option is interesting. It uses the standard tailpiece tips (smaller diameter than the pipework) and a fairly large silencer. The design is much the same as the standard system. On that basis I don't think it will be much louder or different to OEM so it would be good to hear it the flesh - if you check it out let us know what you think of it []

I'm dubious of their claim of a 20bhp gain using their solution. My car has a much simpler design with less silencing and wider exits and it added 20bhp. How are they matching that when their exhaust is more restrictive....

 

[ralphmusic]

Litchfield have a state of the art in-house Maha dyno and do a lot of very high-end engineering and tuning - I'd trust their power measurements.

 

[Twinfan]

I'm just wondering if they're being a bit sneaky that's all. They say in their blog that they evaluated different designs and they all gave 20bhp. One of their designs is very similar to my system, so I'm just wondering if they're using a dyno run from that design for marketing purposes. Akrapovic have a more silenced design similar to Litchfield's production system and only claim a 6bhp increase, for example.

I'm not saying it's not possible, it's just that if they've got a decent volume increase with an extra 20bhp and zero drone for £3k they've performed alchemy []

 

[Motorhead]

Chaps,

Here’s a blog which describes various stages of the Lichfield exhaust development as well as giving a back-to-back dyno comparison which shows their claimed power and torque gains. They mention the problem of droning with modified exhausts and the first photo shows a couple of Helmholtz resonators which no doubt were incorporated to address this and other issues but which are absent in the final design. As Dave says it resembles the standard design but with a smaller - and much lighter - silencer box, although I’m sure that there will be some fancy internal pipe and baffling work.

https://www.litchfieldmotors.com/blog/porsche-718-gts-gt4-exhaust-development/

At £2,994 it’s priced competitively, although it’s stainless steel rather than titanium or inconel which is used for some other systems.

Jeff

 

[Twinfan]

But which design was used for the dyno comparison, Jeff? It's not clear in the blog, is there a reason for that?

 

[geoff lane]

Lichfield say they have sorted the drone at low revs with their replacement back box. I am looking forward to checking their GT4 out which has it fitted and if its ok will probably have one fitted.

When they had my car before Christmas for some PPF repairs, I had a look at the silencer and asked if I could hear it on the car and was told by Iain that they had sold the car so I should check to see if they have fitted out another car before you go to Tewkesbury.

 

[Motorhead]

But which design was used for the dyno comparison, Jeff? It's not clear in the blog, is there a reason for that?

Yes, that was my initial thought too Dave … but then I’m always cynical about manufacturer claims! []

Jeff

 

[TDT]

You can only reasonably make claims of power gain, if you have taken a reading on the same dyno with the car before and after the mods.

If a vendor has done that and they can show the plots, they can claim the gains.

If a vendor only has one reading: after the mods were done, how can the gain actually be claimed...what was the car making in the first place?

Peak numbers on a dyno can read anything. Dyno is only useful really as a measure for before and after.

As for the dynometer itself, as Ralph says, Maha Dyno is state of the art.

 

[geoff lane]

You can only reasonably make claims of power gain, if you have taken a reading on the same dyno with the car before and after the mods.

If a vendor has done that and they can show the plots, they can claim the gains.

If a vendor only has one reading: after the mods were done, how can the gain actually be claimed...what was the car making in the first place?

Peak numbers on a dyno can read anything. Dyno is only useful really as a measure for before and after.

As for the dynometer itself, as Ralph says, Maha Dyno is state of the art.

Litchfields are not a back street outfit you would surely expect them to have done the basics as mentioned above. I was impressed with the operation and they are on the money with GTR and BMW enhancements. Anyone who is interested and gets one fitted I would like to hear what they think as I might go with one but want to sample the sound before I buy.

 

[TDT]

You can only reasonably make claims of power gain, if you have taken a reading on the same dyno with the car before and after the mods.

If a vendor has done that and they can show the plots, they can claim the gains.

If a vendor only has one reading: after the mods were done, how can the gain actually be claimed...what was the car making in the first place?

Peak numbers on a dyno can read anything. Dyno is only useful really as a measure for before and after.

As for the dynometer itself, as Ralph says, Maha Dyno is state of the art.

Litchfields are not a back street outfit you would surely expect them to have done the basics as mentioned above.

I was impressed with the operation and they are on the money with GTR and BMW enhancements. Anyone who is interested and gets one fitted I would like to hear what they think as I might go with one but want to sample the sound before I buy.

Absolutely. I've known Litchfield a long time, and they are providing their workings.

My comments really were an advisory for when looking at all vendors/products , when it comes to making claims on gains.

If you supply comparative data to show the gain, great. If you have only a single run or 'after' data only... not sure you can reliably claim a gain - and certainly at that point, you can't say that others are making the numbers, when the others are providing data.

 

[Twinfan]

OK, so you're clearly pointing fingers at me Tyrone. I'm happy to clarify my comments and views:

1. My dyno run was done after the mods only as an exploratory exercise. It wasn't done to prove any gains as we didn't do a before run. However, I was told the dyno used measured a stock 718 GTS 2.5 at 360bhp the day before using the same configuration so it appears to be pretty accurate. Assuming my car was putting out something around standard power as stock it appears to have gained around 20bhp. They dyno run I've posted measured peak torque at 423.8 Nm and the car is electronically limited to 420 Nm so it's seems pretty much on the money to me.

2. I'm not saying Litchfield are a shower of scammers, far from from it. They have a very good reputation. I just think they should clarify which exhaust configuration was used to generate the dyno run on their website as it's not clear that it's definitely the exhaust they are currently offering for sale. They've posted pictures of other development versions which have much less silencing and which will be less restrictive and potentially produce more power.

[]

 

[TDT]

OK, so you're clearly pointing fingers at me Tyrone. I'm happy to clarify my comments and views:

1. My dyno run was done after the mods only as an exploratory exercise. It wasn't done to prove any gains as we didn't do a before run. However, I was told the dyno used measured a stock 718 GTS 2.5 at 360bhp the day before using the same configuration so it appears to be pretty accurate. Assuming my car was putting out something around standard power as stock it appears to have gained around 20bhp. They dyno run I've posted measured peak torque at 423.8 Nm and the car is electronically limited to 420 Nm so it's seems pretty much on the money to me.

2. I'm not saying Litchfield are a shower of scammers, far from from it. They have a very good reputation. I just think they should clarify which exhaust configuration was used to generate the dyno run on their website as it's not clear that it's definitely the exhaust they are currently offering for sale. They've posted pictures of other development versions which have much less silencing and which will be less restrictive and potentially produce more power.

[]

Lol - was i that obvious?

But really - as you said... the dyno run was exploratory, as an indictor, and thats cool. But the point still stands - if you didn't have a prior run - you don't know the actual gain after, and in your case it might not be possible to attribute all of the gain just to the silencer, as you have the flywheel too, so is that 'releasing some drag which translates to hp?'... - as it is unless you get numbers at each point (after each mod) you don't really know... I'm not saying there are not gains - I'm saying, can we really be sure of what they are, without a comparison - other than that and just based on the factory figures as a baseline - its an indicative estimate, not a substantiated claim -and there's nothing wrong if its presented as that - (indicative estimate - 20hp)... nobody can argue with that.

At the end, we just have to be careful when stating things and particularly when others are producing before/after and showing evidence... those cannot be poo-poo'd or have doubts cast on them.

All good

 

[Twinfan]

I'm quite happy to question Litchfield's claims as they don't stack up to me given the spec of the exhaust for sale vs others they tried. It's not clear which system was dyno'd as they're suitably vague on their site, so I can only assume that's been done on purpose. So they can have doubts cast on them as far as I'm concerned. YMMV of course []

 

[MannyLon]

Oh how I would love an exhaust shoot out. All manufacturers turn up at a neutral testing center and before and after claims can be settled

I'm willing to bet most will not make more than 5BHP and some may even be down on power. Let's not forget the Porsche spend millions on testing new cars and exhaust manufactures, many of whom are small outfits really cannot compete on the same level.

 

[Twinfan]

Oh how I would love an exhaust shoot out. All manufacturers turn up at a neutral testing center and before and after claims can be settled

I'm willing to bet most will not make more than 5BHP and some may even be down on power. Let's not forget the Porsche spend millions on testing new cars and exhaust manufactures, many of whom are small outfits really cannot compete on the same level.

Porsche have noise limits to stick to, aftermarket silencers don't, so gains are more easily gotten []

 

[MannyLon]

Double post. Not sure what happened there..

 

[MannyLon]

Fair enough, but most of the noise is on the OPF. Still, your exhaust supplier is better priced than others. A SS backbox should not cost more than 1k IMO.

 

[TDT]

I'm quite happy to question Litchfield's claims as they don't stack up to me given the spec of the exhaust for sale vs others they tried. It's not clear which system was dyno'd as they're suitable vague on their site, so I can only assume that's been done on purpose. So they can have doubts cast on them as far as I'm concerned. YMMV of course []

From the product description -

The rear silencer uses an internal chamber with x-pipe design to help improve scavenging and reduce droning. With the valves open the engine performance is improved by 20bhp with useable gains in torque from as little as 4,000rpm (14.5lbft @5,000rpm) with power increasing higher up the rev range where the engine spins freely as it accelerated more readily to the redline.

So with the valves open gases take a direct path and its essentially a straight pipe - just like any other of these systems are - including yours. They specifically say, the 'additional 20hp' is realised, when not going through the silencing - valves open, on a valved system.

Don't think that there is an argument against that without some evidence.