991 Direct Injection
#16
Both of you guys have a nice number of miles on your cars. That's very encouraging! Any problems with a rough idle on cold starts (especially in low ambient temperatures)?
The problem with Audi's carbon buildup is that it happens so gradually that you really don't notice the power loss. I have a series of dyno plots I made with a friend's car over the first few years of ownership. We dyno'd it a few times as he racked up the miles. He didn't feel any difference in driving it, but the numbers don't lie. After a carbon cleaning we re-dyno'd to see a bump of 40whp. It felt like a different car.
The problem with Audi's carbon buildup is that it happens so gradually that you really don't notice the power loss. I have a series of dyno plots I made with a friend's car over the first few years of ownership. We dyno'd it a few times as he racked up the miles. He didn't feel any difference in driving it, but the numbers don't lie. After a carbon cleaning we re-dyno'd to see a bump of 40whp. It felt like a different car.
I'm sure you're right regarding an insidious loss of power. I've never dyno'd the car to know for sure but all outward signs are showing a healthy car. I'm very interested in this topic, as well. Can't wait to see the inside of one of these engines.
#17
Thanks for bringing this topic up - I had been wondering if this was going to be an issue (not that it prevented me from placing an order. )
#18
It is definitely a US gas issue. You'll see considerable deposits with 87 (don't use it) octane versus 91/93 octane. Lexus also has the same issue.
You can spike once in a while:
https://www.6speedonline.com/forums/...on-2-93-a.html
Also could 991 owners confirm if 91 octane is recommended, unlike on 997s?
You can spike once in a while:
https://www.6speedonline.com/forums/...on-2-93-a.html
Also could 991 owners confirm if 91 octane is recommended, unlike on 997s?
#20
It is definitely a US gas issue. You'll see considerable deposits with 87 (don't use it) octane versus 91/93 octane. Lexus also has the same issue.
You can spike once in a while:
https://www.6speedonline.com/forums/...on-2-93-a.html
Also could 991 owners confirm if 91 octane is recommended, unlike on 997s?
You can spike once in a while:
https://www.6speedonline.com/forums/...on-2-93-a.html
Also could 991 owners confirm if 91 octane is recommended, unlike on 997s?
#22
No rough idle at cold starts but for the first few feet of driving, the car tends to stutter. This only occurs if the car has been cold soaked below, say, 50 degrees overnight and I'm just using light throttle. There was a high pressure fuel pump replacement campaign that Porsche performed voluntarily on certain VIN's that I thought would help this but it didn't. Otherwise, the car starts up and goes on its way perfectly.
I'm sure you're right regarding an insidious loss of power. I've never dyno'd the car to know for sure but all outward signs are showing a healthy car. I'm very interested in this topic, as well. Can't wait to see the inside of one of these engines.
I'm sure you're right regarding an insidious loss of power. I've never dyno'd the car to know for sure but all outward signs are showing a healthy car. I'm very interested in this topic, as well. Can't wait to see the inside of one of these engines.
#23
I understand your concerns and would like to offer my services. Let me borrow your new 991 for a day a month and I will make sure to blow out any carbon buildup. Because I am a nice guy, I will do it for free. This is just the king of guy that I am.
#24
I guess what I would like to know is how you get carbon buildup on an intake valve? It should be closed when combustion takes place. With DFI it only opens to let air in. ???
Someone please explain if you know. If it is on the bottom of the valve just run the **** out of your car like I do!
Someone please explain if you know. If it is on the bottom of the valve just run the **** out of your car like I do!
#25
I guess what I would like to know is how you get carbon buildup on an intake valve? It should be closed when combustion takes place. With DFI it only opens to let air in. ???
Someone please explain if you know. If it is on the bottom of the valve just run the **** out of your car like I do!
Someone please explain if you know. If it is on the bottom of the valve just run the **** out of your car like I do!
I was primarily a lurker on Audiworld and still get most of my news from Quattroworld Off-Topic forum. I'm not an active poster, but an avid reader of the forums.
Thanks for bringing this topic up - I had been wondering if this was going to be an issue (not that it prevented me from placing an order. )
Thanks for bringing this topic up - I had been wondering if this was going to be an issue (not that it prevented me from placing an order. )
I'm glad to bring up the subject for discussion. It's nice to see a civilized discussion of it on here.
#28
There is NO documented info on P engines....because the 9A1 engine is DFI then it is THEORETICALLY at risk.
How do you know you have no crud on your valves? Have you unroofed and taken a peek? Pics?
I will be replacing my valves with an X51 kit (in shop now), I will extensively photograph my valves...this on a 2010 C2S with 26K miles.
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sdg1871
991 Turbo
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09-12-2015 06:54 AM