928 over Panamera
03-28-2018, 06:26 PM
#1
Three Wheelin'
Thread Starter
928 over Panamera
So, I was thinking of selling my venerable/still fun 928S and investing in a used Panamera, likely with 3-6l w/r to my budget. I’m diligent enough to get considerable miles/durability from cars in my stable. And surely, Panamera is a blast in its youth. But......
https://rennlist.com/forums/panamera...ses-flaws.html
its the “Gas Direct Injection” (GDI) part that gets me. GM, Lexus and others including Porsche rushed headlong into GDI, without giving consideration to the obvious, eventual oil coking of intake valves, which no longer experience fuel washing. Frightful pictures of GDI related crud caked Intake valves are available throughout the internet for many GDI engines.
https://www.rennology.com/your-car/p...rbon-cleaning/
no, I’m not affiliated and I don’t live there. I’m just hugely disappointed and now disinterested in a (used) car I once aspired to own. Bear in mind some manufacturers (Toyota) are straightening out their GDI designs to include extra injectors to wash intake valves. Sheesh. And in the past I’ve sent heads off for valve refresh which returned with only exhaust valves replaced, because the intakes were functional as new. My 928S looks suddenly better in It’s garage space.
https://rennlist.com/forums/panamera...ses-flaws.html
its the “Gas Direct Injection” (GDI) part that gets me. GM, Lexus and others including Porsche rushed headlong into GDI, without giving consideration to the obvious, eventual oil coking of intake valves, which no longer experience fuel washing. Frightful pictures of GDI related crud caked Intake valves are available throughout the internet for many GDI engines.
https://www.rennology.com/your-car/p...rbon-cleaning/
no, I’m not affiliated and I don’t live there. I’m just hugely disappointed and now disinterested in a (used) car I once aspired to own. Bear in mind some manufacturers (Toyota) are straightening out their GDI designs to include extra injectors to wash intake valves. Sheesh. And in the past I’ve sent heads off for valve refresh which returned with only exhaust valves replaced, because the intakes were functional as new. My 928S looks suddenly better in It’s garage space.
03-28-2018, 11:12 PM
#3
Three Wheelin'
Thread Starter
The point is in the background. 32 years old, 140k miles and still strong are values I’ve come to appreciate in my 928 and therefore in Porsche. Oil coked intake valves in newer Porsche’s breaks the pattern of superior engineering. And of course, as stated the outcome is a greater appreciation of what I already drive. Never a bad thing.
03-29-2018, 12:13 AM
#4
Rennlist Member
The oil coking occurs in all engines utilizing DFI, not just Porsche. It is very fuel and power efficient method of delivery to the combustion chamber, but comes with some birthing pains. Newer engines are now utilizing DFI along with port injection to alleviate this problem. I spent an hour reading about it on Wikipedia and it's some good bedtime reading material if you're so inclined.
03-29-2018, 11:39 AM
#5
Three Wheelin'
Thread Starter
The oil coking occurs in all engines utilizing DFI, not just Porsche. It is very fuel and power efficient method of delivery to the combustion chamber, but comes with some birthing pains. Newer engines are now utilizing DFI along with port injection to alleviate this problem. I spent an hour reading about it on Wikipedia and it's some good bedtime reading material if you're so inclined.
03-29-2018, 12:16 PM
#6
Banned
First of all it is correctly referred to as DFI - Direct Fuel Injection. Second of all, it is not a performance modification per se; it is a fuel efficiency think. The reason why Porsche went with DFI, as well as a slew of other MFGs is FUEL EFFICIENCY. There was no other way to maintain the aggressive fuel goals set by world governments than DFI. Ditto for turbocharging - it is no longer a performance modification.
DFI on a large scale makes lots of power and is good for a motor. Not sure why you are obsessed with coking, as it is not really a factor in the ownership of the vehicle.
DFI on a large scale makes lots of power and is good for a motor. Not sure why you are obsessed with coking, as it is not really a factor in the ownership of the vehicle.
03-29-2018, 01:07 PM
#7
First of all it is correctly referred to as DFI - Direct Fuel Injection. Second of all, it is not a performance modification per se; it is a fuel efficiency think. The reason why Porsche went with DFI, as well as a slew of other MFGs is FUEL EFFICIENCY. There was no other way to maintain the aggressive fuel goals set by world governments than DFI. Ditto for turbocharging - it is no longer a performance modification.
DFI on a large scale makes lots of power and is good for a motor. Not sure why you are obsessed with coking, as it is not really a factor in the ownership of the vehicle.
DFI on a large scale makes lots of power and is good for a motor. Not sure why you are obsessed with coking, as it is not really a factor in the ownership of the vehicle.
because, soon enough they will replace it with another blingmobile. Then there are those who want a keeper, like most serious collectors. I recently read about a car that has part of the suspension going through a window in the oil pan,
That goes in the same territory of stupid...like BMWs with no dipstick.
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03-29-2018, 01:24 PM
#8
Banned
Why is the lack of a dipstick stupid? I have several cars with no dipstick, one of them is a BMW. It has never failed to alert me when it is low on oil, and if I want to check how much oil is in it, I push a button on the dash and it tells me.
Most new car problems are caused mainly from owners who are totally not adaptable to any sort of change. I think a good amount of new cars these days come with no dipsticks, and to be honest, it probably results in BETTER oil filling than in the past, because half the people never check the dipstick anyways, but a warning light on the dash spurs them into action.
I love the 928 but it is a very primitive car by today's standards and has not been cutting edge for 30+ years.
Most new car problems are caused mainly from owners who are totally not adaptable to any sort of change. I think a good amount of new cars these days come with no dipsticks, and to be honest, it probably results in BETTER oil filling than in the past, because half the people never check the dipstick anyways, but a warning light on the dash spurs them into action.
I love the 928 but it is a very primitive car by today's standards and has not been cutting edge for 30+ years.
03-29-2018, 01:36 PM
#9
Three Wheelin'
First of all it is correctly referred to as DFI - Direct Fuel Injection. Second of all, it is not a performance modification per se; it is a fuel efficiency think. The reason why Porsche went with DFI, as well as a slew of other MFGs is FUEL EFFICIENCY. There was no other way to maintain the aggressive fuel goals set by world governments than DFI. Ditto for turbocharging - it is no longer a performance modification.
DFI on a large scale makes lots of power and is good for a motor. Not sure why you are obsessed with coking, as it is not really a factor in the ownership of the vehicle.
DFI on a large scale makes lots of power and is good for a motor. Not sure why you are obsessed with coking, as it is not really a factor in the ownership of the vehicle.
Having put over 200,000 miles on various DFI vehicles the past 5 years, I've not had any issues. Not on the GM vehicles, or the Porsche we have w/ DFI.
The 928 IS a different animal, but I am careful not to make any comparison, as there is no...
03-29-2018, 01:49 PM
#10
Three Wheelin'
Thread Starter
Not a factor? Take a look at plenty of samplings of oil coked intake valves of GDI equipped vehicles. Contemplate valve guide wear, air flow dynamics (around oddly shaped carbon lumps). Carbon lumps breaking off, making their way to the cats. These aren’t my made up concerns. These are real experiences by some owners of GDI equipped vehicles. Same reasons manufacturers are *adding* Multipoint Injection (aka Port Injection) *in addition to* GDI. Yes, two injectors per cylinder. Mainly to solve intake valve oil coking. Prevention is the best remedy. Prevention in this case; wait to buy until the manufacturer directly addresses the issue with an updated design. So, the original concern showed up in the Panamera forum where it should probably have stayed. My point was my 928 gets a new lease after this revelation, no used Panamera until much much later.
Last edited by mj1pate; 03-29-2018 at 02:21 PM.
03-29-2018, 03:25 PM
#11
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I owned an early car with DFI - an '09 Cayman. Sold it last year at 92,000 miles. I don't recall hearing that it might be a big problem. Neither did the buyer.
That's one data point. There's lots of data behind this quote: Michael Karesh, the developer of TrueDelta.com said carbon buildup is “not an issue for all direct-injected engines” based on the data he collects. "The only engines it’s reported quite a bit is [with] the VW/Audi 2.0T and then the Audi V6s."
Hmm. My new Macan has an Audi 2.0 Turbo.
http://www.autoguide.com/auto-news/2...-engines-.html
That's one data point. There's lots of data behind this quote: Michael Karesh, the developer of TrueDelta.com said carbon buildup is “not an issue for all direct-injected engines” based on the data he collects. "The only engines it’s reported quite a bit is [with] the VW/Audi 2.0T and then the Audi V6s."
Hmm. My new Macan has an Audi 2.0 Turbo.
http://www.autoguide.com/auto-news/2...-engines-.html
03-29-2018, 04:56 PM
#12
Banned
03-29-2018, 05:03 PM
#13
Administrator - "Tyson"
Lifetime Rennlist
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Lifetime Rennlist
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How big is the issue? Kinda moot discussing this in a 928 forum.....however, the independent mechanics I know are enjoying the revenue from removing intakes and cleaning them up.
When I talked to one of these mechanics (also a 928 guru) specifically about a DFI Audi, he doesn't consider this issue a big deal either and it wouldn't detract him from buying one.
03-29-2018, 11:20 PM
#14
Three Wheelin'
Thread Starter
I think what he's saying is don't buy a first generation DFI engines. The 2nd gen and beyond with a port injector solve the issue.
How big is the issue? Kinda moot discussing this in a 928 forum.....however, the independent mechanics I know are enjoying the revenue from removing intakes and cleaning them up.
When I talked to one of these mechanics (also a 928 guru) specifically about a DFI Audi, he doesn't consider this issue a big deal either and it wouldn't detract him from buying one.
How big is the issue? Kinda moot discussing this in a 928 forum.....however, the independent mechanics I know are enjoying the revenue from removing intakes and cleaning them up.
When I talked to one of these mechanics (also a 928 guru) specifically about a DFI Audi, he doesn't consider this issue a big deal either and it wouldn't detract him from buying one.
03-30-2018, 01:03 AM
#15
Rennlist Member
The reason GDI or DDI cars cake up with crap on the intake valves is from soot from the EGR system and oil from the crank case ventilation system mixing and forming a sludge that sticks to everything.
The only real way to combat these long term is to eliminate the EGR system and or improve the crank ventilation system's oil separating ability with something like a provent.
You can also add methanol/water injection, that has shown great promise on diesel BMWs with gunk issues like the last gen 335D that need their intakes and valves walnut shell blasted every 75K miles.
Most 928s don't have and egr system ( 78-79 CIS only IIRC ) so our ports remain clean even though our crank case ventilation is poor at best causing quite a bit of oil to be ingested.
The only real way to combat these long term is to eliminate the EGR system and or improve the crank ventilation system's oil separating ability with something like a provent.
You can also add methanol/water injection, that has shown great promise on diesel BMWs with gunk issues like the last gen 335D that need their intakes and valves walnut shell blasted every 75K miles.
Most 928s don't have and egr system ( 78-79 CIS only IIRC ) so our ports remain clean even though our crank case ventilation is poor at best causing quite a bit of oil to be ingested.