Porsche's new philosophy with the GT3 according to AP
03-24-2017, 10:13 AM
#76
Race Director
Good info Zulu. Thanks.
03-24-2017, 11:49 AM
#77
Anytime Gentlemen, don't mention it.
Personally and honestly, it doesn't matter to me if whoever calls it top down or bottom up. It just irks me to see people worshipping at the Mezger alter and eventually it will be the same for this new engine, and eventually we will see someone say "my car is the last NA 'Mezger' (insert new bogus name for the 9A1 race engine) engine you will ever see in your entire life" then Porsche comes out with a new (insert new bogus engine name here) NA engine, and the planet will start revolving again.
Originally Posted by RealityGT
Same same but diffelent? haha (node to CAlexio)
Seriously though.. I notice a lot of disdain from some .1 and RS owners.. Can't we just all get along!
Seriously though.. I notice a lot of disdain from some .1 and RS owners.. Can't we just all get along!
03-24-2017, 01:01 PM
#78
Nordschleife Master
Alright, let's get one thing straight about the Hydraulic lifters, the reason they were used in the 991.1 GT3 is that they were concerned that the rocker would float from the cam lobe at high RPM. They included a hydraulic dampener remedy this float/slap at high RPM. Unfortunately, as we now know that this is a design flaw that caused the cam lobe to score because there was too much force on the lobe as there was not enough oil running, thus introducing a new oiling system for the G engines. Now with the new gen II engines, they got rid of these hydraulic dampeners due to issues I just mentioned. Moving forward, they managed to scrap them and find the benefit of A) no more floating/slap at high RPM and B) no need for adjustment later in the engine life cycle. Let's see what the documentation says when we get our impatient grubby hands on them.
You want 9000+ rpm? Solids are the way to go.
03-24-2017, 01:28 PM
#79
Technical Guru
Rennlist Member
Rennlist Member
Even the very last Mezger GT3R and the RSR had solid-lifters that needed to be checked every 300km. With the street cars the maintenance intervals and exhaust gas emissions at startup were more important. But if they've solved those two issues with a cheaper solution then why not? And it probably won't be all that difficult to use the new parts on the old engine, it usually isn't for something this minor...
03-24-2017, 01:35 PM
#80
Race Director
Porsche has sold a decent amount of .1s. There will be a good market for this fix.
03-24-2017, 02:33 PM
#81
Rennlist Member
Alright, let's get one thing straight about the Hydraulic lifters, the reason they were used in the 991.1 GT3 is that they were concerned that the rocker would float from the cam lobe at high RPM. They included a hydraulic dampener remedy this float/slap at high RPM. Unfortunately, as we now know that this is a design flaw that caused the cam lobe to score because there was too much force on the lobe as there was not enough oil running, thus introducing a new oiling system for the G engines. Now with the new gen II engines, they got rid of these hydraulic dampeners due to issues I just mentioned. Moving forward, they managed to scrap them and find the benefit of A) no more floating/slap at high RPM and B) no need for adjustment later in the engine life cycle. Let's see what the documentation says when we get our impatient grubby hands on them.
The only reason Porsche utilized Hydraulic lifters is because of cost/economics. Hydraulic lifters are prone to valve "pump up" or "bleed down", as you stated. Solid lifters are not. Solid lifters are superior in every aspect wrt performance. Period.
Porsche understood this limiting factor and incorporated "anti-pump-up-lifters", as almost every manufacture does. Which as you stated, accounts for the stiffer/heavier plunger. This extra cam lobe drag/mass in conjunction with relatively high oil pressures is why they have scoring issues. Excessive mass/drag is an inherent issue with hydraulic lifters. This is why virtually every high RPM motor utilizes solid lifters. They are superior.
IMO, Porsche neglected to obtain sufficient empirical data wrt oil pressures and valvetrain cam lobe stresses at 9k under lateral loads. That is why they have approached this issue from both angles. Eliminating both the inefficient lifter design, and decreasing oil pressure in the valvetrain.
03-24-2017, 02:48 PM
#82
Addict
Rennlist Member
Rennlist Member
Do you think it's likely that Porsche has really cracked the question of how to make solid lifters with no lifetime lash adjustments or does this seem overly optimistic?
03-24-2017, 02:59 PM
#83
Rennlist Member
This will be the 991 GT3 to own long term.
03-24-2017, 03:10 PM
#84
Race Director
03-24-2017, 03:17 PM
#85
Race Director
This obsession with AP has got to stop. The guy is a pitchman and FOS most of the time. Just like every piece of porsche marketing.
Every single engine they build has major issues. For such a renowned engineering firm, they **** up an awful lot. I bet you there are issues with these special coatings.
Every single engine they build has major issues. For such a renowned engineering firm, they **** up an awful lot. I bet you there are issues with these special coatings.
03-24-2017, 03:37 PM
#86
03-24-2017, 03:59 PM
#87
Instructor
This obsession with AP has got to stop. The guy is a pitchman and FOS most of the time. Just like every piece of porsche marketing.
Every single engine they build has major issues. For such a renowned engineering firm, they **** up an awful lot. I bet you there are issues with these special coatings.
Every single engine they build has major issues. For such a renowned engineering firm, they **** up an awful lot. I bet you there are issues with these special coatings.
03-24-2017, 04:05 PM
#88
Rennlist Member
"In view of this accelerative performance, the valvetrain hidden behind the magnesium alloy cylinder head covers also came under intense scrutiny. Light but strong titanium alloy was employed once again in the construction of the valves, while the valve springs are cylinder-shaped and of a low-inertia design to remove the chance of valve float at high revs. These were partnered with ultra-lightweight solid rocker arms featuring a special diamond-like wear-resistance coating and integrated oil jets."
03-24-2017, 04:08 PM
#89
Rennlist Member
03-24-2017, 04:12 PM
#90
Rennlist Member
I thought Lexus LFA also had solid lifters. This is from the UK website. They refer to it as solid rockers, but I think they refer to lifters. Correct me if I'm wrong.
"In view of this accelerative performance, the valvetrain hidden behind the magnesium alloy cylinder head covers also came under intense scrutiny. Light but strong titanium alloy was employed once again in the construction of the valves, while the valve springs are cylinder-shaped and of a low-inertia design to remove the chance of valve float at high revs. These were partnered with ultra-lightweight solid rocker arms featuring a special diamond-like wear-resistance coating and integrated oil jets."
"In view of this accelerative performance, the valvetrain hidden behind the magnesium alloy cylinder head covers also came under intense scrutiny. Light but strong titanium alloy was employed once again in the construction of the valves, while the valve springs are cylinder-shaped and of a low-inertia design to remove the chance of valve float at high revs. These were partnered with ultra-lightweight solid rocker arms featuring a special diamond-like wear-resistance coating and integrated oil jets."
