JCtx

It has a detuned version of the Carrera S motor (385 vs 400 -420 on GTS-), therefore not a GT one.

I also don't see any way to have valve lift on the GT3 valvetrain. Are we missing something?

Jamie@dundonmotorsports

991 GT3 doesn't have high and low lift lobes on the cams. Just the one high lift. It does have variocam (variable cam timing) for both cams

GT4 has high and low lift lobes on the cams and variable valve timing.

The 991 GT3 does have a sophisticated torque monitoring system and from what I've heard from motorsports engineers, the car uses coil current draw to estimate cylinder pressure as a way to monitor torque/cylinder. This in conjunction with misfire detection is how the car likely detects the high rpm misfire...

m42racer

There you have it. Explanation on both points. Thank you.

WernerE

Thanks to Macca for a brief synopsis on this thread above. As the owner of a 2015 GT3, I'm an interested party. What I find fascinating is Porsche doing the calculus on its liability for replacing future engines against the assumption on how many track their cars. I assume most do track their GT3, and therefore Porsche appears far more confident in these engines than the length of this thread suggests.

If the E, F and G motors are really in the same boat, including those dropped in the latest RS models, I'm willing to bet the # of motors that will need retrofitting and/or replacement under warranty is a reasonably modest number. If it were not so, why would Porsche extend the production run of the RS'? Or is it that the number of tracked GT3s is significantly smaller than I assume and Porsche is willing to write it off as the cost of doing business/engine development?

bronson7

^^^I think Porsche has a good idea of how many owners track their car.

Ceepe

This is one amazing thread!

Macca

Werner. My view on this is that Porsche have at various junctures believed they have found the remedy to the issue. Hence the continuation of the engine in its relative guises in the RS and GT3. The fact they have in the last 6 weeks introduced an updated component (Camshafts with DLC coated lobes) indicates they have been unsuccessful to date and have now moved their focus from finger follower coatings and oil pressure/additional lubrication to the cam lobe mating surface. They must have some confidence this will be an improvement or else they would not have incorporated this into the very recent 911R and RS engines. Is this the final part of the equation to make the engine "fit for use"? It's hard to say and the body of evidence would suggest it's just one change in a long series of updates so far.

The thing that has me very curious is why these issues could not have been fully identified and resolved on the test bench over the last three years? I guess we will never know....

bronson7

I find this so hard to believe. Porsche obviously did not do their homework first time out. What does this say for the future of Porsche. This does not send a good message.

Macca

Yes it's an unfortunate situation and it will take some time before we know if this chapter in history is closed. In fact I venture to suggest it may take well into 991.2 GT3 production unless of course that car has a significantly re designed valve train. As others far better trained to comment have said, the issue related to the move to a valve train that was designed to endure high revolution activity (I.e. The much vaunted 9000 rpm). Interesting last night I was looking for a document and venture and upon my file on the GT3 launch and media. The focus and headline was all about this newly deployed finger follower design and how it enabled the engine to reach such dizzy heights of 9000 and beyond.

History has taught us a few facts. One of them is that PAG chose to reduce the headline max rpm of the RS late in development. The is still a copy of the RS launch video with 9000 rpm RS tachometer floating around YouTube. They in fact reduced the max rpm to around 8675 in most gears except first gear (8800). The 911R was launched with a 8600 max rpm and it was "assumed" the MT had something to do with this. The next GT3 is still unknown but I would suggest 8600-8700 will prevail.

So Porsche reduced the rev limiter while they went about improving their design on our engines.

I guess we need to wait and see what's next. Without a 9000 rev limit I can't really see any benefit of the roller rocker design and they may as well revert to the bucket tapper design. That said they are deep down the rabbit hole now and have developed emissions electronics for this engine etc....

bronson7

Thank you Macca for all your input....respect your opinion greatly.

hf1

They would have incorporated them regardless of their confidence, which they have been doing over the last three years. What would be the alternative -- delaying production or model launches?

ipse dixit

Porsche has found a solution; or, rather, they settled upon a solution.

Porsche AG will simply replace engines until the OEM warranty expires, and then write it off as a cost of doing business.

In the grand scheme of things the cost of replacing engines during the OEM warranty period is minute compared to a full-blown recall where just the cost of negative publicity would take years, and unquantifiable dollars, to recover from

m42racer

Profits are driven by sales and HP is now a factor required in sales to keep ahead of the competition. Add in EU and US fed restrictions and rules you have the ingredients for a really hard nut to crack. The only way you can meet the tight fuel regs and emission regs is to build the engines smaller and more efficient. To gain sales you have to match HP performance so up go the revs. To gain the higher Revs and some chance of longevity, the masses have to be less and lightweight.

The issue is a mechanical fault but probably has turned into a marketing and warranty nightmare.

I think whatever Porsche has or does do to fix the problem, is going to be as stated in other post., Its what is less costly to the company as there is no money to be made in re development and warranty work.

Macca

Yes I think you are right. I was being polite LOL!

Macca

My pleasure Bronson. Its just one opinion in a sea of many on a subject we would all probably preferred did not exist...