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I had the dealer install Tial M660 turbos on my 2017 Carrera with PDK. I also have Soul cats, APR diverter valves, Soul headers, Speed Circuit inlet pipes,which are like Tial but a metal, and a Softronic tune. I had all these mods for a long time before the turbo change last week. I cannot get more than 10 psi of boost at WOT. The car drives flawlessly except for low boost. Somewhere I have a boost leak.
I took the bumper off and it seems that all the hoses are tight and connected. I can hear a whistle when I am acceleration and a resonance around 3000 rpm. The car is very ,very fast, and much faster than it was with just the tune and stock turbos so I can only imagine what it will be when I get full boost. There really is no turbo lag and very good throttle response. Very linear power and feels naturally aspirated. Is there any place where a vacuum connection could be that is not obvious? Any idea where to look for a leak? For those who have Tial intake pipes, do you hear a whoosh or resonance on acceleration? I did have a slight whoosh sound with the pipes before the turbo install but it was very brief. and I think others have heard this like the video from Tommy's Garage. This sounds different.
Did Scott recommend another tune? or did he say that the tune would work with the M660 turbos? I believe you need a new tune with the M660/M800 turbos.
I know that the Softronic tune is aiming for a target power level, and can thus deal with various exhaust modifications and adjust itself, but believe it does not extend to new turbos.
I can tell you from personal experience that when I had almost the exact same amount of boost leak (maxing out at about 10-11 PSI) this was the culprit. Replaced it brought the boost back. These lines are hard and can break easy. It’s one of the vacuum lines that plugs into the y-pipe.
I can tell you from personal experience that when I had almost the exact same amount of boost leak (maxing out at about 10-11 PSI) this was the culprit. Replaced it brought the boost back. These lines are hard and can break easy. It’s one of the vacuum lines that plugs into the y-pipe.
Was that boost leak making any noise?
I have had boost leaks on other cars and they are often quite noisy/loud but not easy to find.
Did Scott recommend another tune? or did he say that the tune would work with the M660 turbos? I believe you need a new tune with the M660/M800 turbos.
I know that the Softronic tune is aiming for a target power level, and can thus deal with various exhaust modifications and adjust itself, but believe it does not extend to new turbos.
When I asked, Scott told me the same base tune is fine with the stock Carrera/S/GTS turbos, but you need a different tune when stepping up to the hybrids.
[QUOTE=Tier1Terrier;20147111]I can tell you from personal experience that when I had almost the exact same amount of boost leak (maxing out at about 10-11 PSI) this was the culprit. Replaced it brought the boost back. These lines are hard and can break easy. It’s one of the vacuum lines that plugs into the y-pipe.
I have had boost leaks on other cars and they are often quite noisy/loud but not easy to find.
Not that I could easily notice. I discovered this after installing cat bypass pipes so there was plenty of other glorious noise that made it hard to hear anything else lol.
[QUOTE=F355bob;20147168]
Originally Posted by Tier1Terrier
I can tell you from personal experience that when I had almost the exact same amount of boost leak (maxing out at about 10-11 PSI) this was the culprit. Replaced it brought the boost back. These lines are hard and can break easy. It’s one of the vacuum lines that plugs into the y-pipe.
I think that is the one that goes to the BOV
Not directly. That line connects to the cluster that sits in the middle between the y-pipe and the engine air filter cover.
[QUOTE=Tier1Terrier;20147491]Not that I could easily notice. I discovered this after installing cat bypass pipes so there was plenty of other glorious noise that made it hard to hear anything else lol.
Originally Posted by F355bob
Not directly. That line connects to the cluster that sits in the middle between the y-pipe and the engine air filter cover.
did you replace the plastic line or the whole fitting that goes to the intake? I took the bumper off the other day and every connection looked good. Will take bumper off again and see if I missed something. Thanks
Not that I could easily notice. I discovered this after installing cat bypass pipes so there was plenty of other glorious noise that made it hard to hear anything else lol.
did you replace the plastic line or the whole fitting that goes to the intake? I took the bumper off the other day and every connection looked good. Will take bumper off again and see if I missed something. Thanks
First I Mcgyver'd it by connecting the two broken ends inside of a rubber sleeve and cinched it down with some zip ties. Honestly, it was probably a perfect repair but I still ordered the replacement part for about $40 from my local Porsche dealership parts department. I then replaced the fixed one with the new one.
It was quite a learning experience for me though. In the process of seeking a solution to repair, I discovered that finding OEM parts (not Porsche brand) that are exact in specification was very hard. I went to two auto parts stores, an Ace Hardware and a Home Depot. Nobody sells vacuum lines/hoses that are the same. It's like Porsche created their own hose material. But I did manage to buy a few lengths of different tube/hose material to play around with and experiment in the event of another breakage. I also bought a couple of other tools, one of which (Single Ear Hose Clamp & Pincer kit) I used to resecure the hose coupling that connects the diverter valve to the cluster of other vacuum lines. I managed to find some 'close enough' alternatives to Porsche brand. It's shocking (not really) how much these parts cost if you buy them from Porsche. For instance, Porsche sells the hard vacuum line from the diverter valve for almost $100 per side. That whole cluster of vacuum lines & hoses that's nestled together between the Y pipe and the air filter will run you several hundred dollars. Maybe 1000. Ridiculous. You can find stuff that's almost the same for a few bucks but it takes a bit of trial and error.
Last edited by Tier1Terrier; Jul 20, 2025 at 05:53 PM.
First I Mcgyver'd it by connecting the two broken ends inside of a rubber sleeve and cinched it down with some zip ties. Honestly, it was probably a perfect repair but I still ordered the replacement part for about $40 from my local Porsche dealership parts department. I then replaced the fixed one with the new one.
It was quite a learning experience for me though. In the process of seeking a solution to repair, I discovered that finding OEM parts (not Porsche brand) that are exact in specification was very hard. I went to two auto parts stores, an Ace Hardware and a Home Depot. Nobody sells vacuum lines/hoses that are the same. It's like Porsche created their own hose material. But I did manage to buy a few lengths of different tube/hose material to play around with and experiment in the event of another breakage. I also bought a couple of other tools, one of which (Single Ear Hose Clamp & Pincer kit) I used to resecure the hose coupling that connects the diverter valve to the cluster of other vacuum lines. I managed to find some 'close enough' alternatives to Porsche brand. It's shocking (not really) how much these parts cost if you buy them from Porsche. For instance, Porsche sells the hard vacuum line from the diverter valve for almost $100 per side. That whole cluster of vacuum lines & hoses that's nestled together between the Y pipe and the air filter will run you several hundred dollars. Maybe 1000. Ridiculous. You can find stuff that's almost the same for a few bucks but it takes a bit of
If the diverter valves aren't getting boost pressure behind them on acceleration due to a cracked or leaking line, they will push open under boost and air will begin recirculating from the post-turbo to the pre-turbo side. The diverter valve springs are pretty weak and rely on boost pressure behind them to 'balance' the pressure above and below the diaphragm so the little strength of the spring can keep the valve closed. I'm guessing the rushing air you're hearing is the air recirculating into the turbo inlet under throttle. With the leaking the line, the boost below the diaphragm (charge pipe) will be higher than whatever it's seeing above it from the line going to the nipple, and it will start to open under mild boost.This is bringing me back to my VW days (who am I kidding, I still have my MK4) when this would happen . Under normal conditions only the sudden increase in vacuum when the throttle snaps closed, or you clutch in and let it idle, defeats the spring and opens the valves to bleed off the boost and recirculate it into the turbo inlet, but in your case, it's likely opening under throttle.
This also lines up with it not pulling like it should. If the diverter valves are bleeding boost under throttle, it’s never going to hit target. The ECU’s smart enough to compensate and make the car seem like it’s running fine with no misfires, no limp mode; but it’s down on power the whole time.
If the diverter valves aren't getting boost pressure behind them on acceleration due to a cracked or leaking line, they will push open under boost and air will begin recirculating from the post-turbo to the pre-turbo side. The diverter valve springs are pretty weak and rely on boost pressure behind them to 'balance' the pressure above and below the diaphragm so the little strength of the spring can keep the valve closed. I'm guessing the rushing air you're hearing is the air recirculating into the turbo inlet under throttle. With the leaking the line, the boost below the diaphragm (charge pipe) will be higher than whatever it's seeing above it from the line going to the nipple, and it will start to open under mild boost.This is bringing me back to my VW days (who am I kidding, I still have my MK4) when this would happen . Under normal conditions only the sudden increase in vacuum when the throttle snaps closed, or you clutch in and let it idle, defeats the spring and opens the valves to bleed off the boost and recirculate it into the turbo inlet, but in your case, it's likely opening under throttle.
This also lines up with it not pulling like it should. If the diverter valves are bleeding boost under throttle, it’s never going to hit target. The ECU’s smart enough to compensate and make the car seem like it’s running fine with no misfires, no limp mode; but it’s down on power the whole time.
Found the leak and it was the intake hose that gives vacuum to the diverter valves. It was not completely seperated but cracked so I missed it the first time. Can now get 18psi and no weird noises. Thanks to all who gave advice and support.
Glad you have that fixed, I see that you’re over the moon with this. How is response / playfulness with these turbos relative to the base ones? One thing I’m afraid of looking is the “NA-like” feel of the base turbos.
M660 install but boost leak
. Under normal conditions only the sudden increase in vacuum when the throttle snaps closed, or you clutch in and let it idle, defeats the spring and opens the valves to bleed off the boost and recirculate it into the turbo inlet, but in your case, it's likely opening under throttle.
