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I bought a used 2006 Cooper S that was not running so I wasn’t able to check much out before I bought it. I was able to get it running (ended up being a blown fuse) but now I’m chasing down a P1498 code (downstream supercharger air leak). I can reset the code and it will drive fine for a little while but the code will come back on in about 15min. Even that it is driving “fine” the max boost I’m reading is around 11.8 to 12 psi.
According to the seller, it has had a supercharger service done and a 15% pulley installed. I haven’t measured the pulley yet, so for now I'm assuming this is true. I have confirmed that it has a 4-2-1 header installed and a catless straight pipe. There is also an aftermarket catback exhaust system installed but I’m unsure of the brand. I was told it’s a cheap $300 unbranded eBay exhaust.
I’ve heard that psi can be lower when more air is flowing. Does anyone have a similar setup that can compare boost numbers for me?
I’m curious if maybe the boost levels are somewhat ok and maybe the ECU needs reset so it can relearn after these mods have been done?
FYI… I’ve already removed and inspected the vacuum line that runs from the horn and fuel pressure regulator. I’ve also zip tied the bypass valve closed and took it for a drive. There was no increase in boost, however after returning home the P1498 code was not present.
I'd expect you to have a couple more PSI than that. How are the intercooler couplers under the hood? If they are worn, or aren't mated/clamped down properly it's a common problem for losing pressure (and would account for your code). Another frequent problem is the belt might be too long, and is slipping. A smaller size belt is required when the pulley is swapped, and colder burning spark plugs are recommended as well. The good news is most folks that would swap the pulley out should know this and many options are kits that include the belt and plugs.
The added breathing from the exhaust shouldn't effect boost pressure. Is the intercooler stock? If you have an aftermarket larger intercooler, that definitely does.
Last edited by OutlandishnessDue; 09-17-2024 at 06:52 PM.
I'd expect you to have a couple more PSI than that. How are the intercooler couplers under the hood? If they are worn, or aren't mated/clamped down properly it's a common problem for losing pressure (and would account for your code). Another frequent problem is the belt might be too long, and is slipping. A smaller size belt is required when the pulley is swapped, and colder burning spark plugs are recommended as well. The good news is most folks that would swap the pulley out should know this and many options are kits that include the belt and plugs.
The added breathing from the exhaust shouldn't affect boost pressure. Is the intercooler stock? If you have an aftermarket larger intercooler, that definitely does.
Thanks for your reply. After posting this I came across several threads talking about how bad the aftermarket intercoolers are. I had no idea and didn’t even think to mention the fact that the previous owner installed one of those cheap eBay intercoolers. I’ve already ordered a new Bypass valve from Detroit Tuned and also a set of factory inter cooler boots as he gave me the stock intercooler.
I’ll see if I can pull the plugs and get numbers off of them and the belt to see if those have been replace as needed.
I’ll report back once the Bypass valve and stock inter
cooler is installed.
I have a couple of points of reference. I just removed a supercharger that I was running a 17% pulley on which I would see about 13 psi of boost. That was with a ported inlet pipe to the supercharger, ported intercooler horns, ported intake manifold, a GRS Motorsports intercooler and BMW V12 throttle body (about 3mm larger inlet than stock).
I installed a ported Stiegemeier supercharger with, I believe to be a JCW (11%) pulley. I now see 10 psi of boost on my Autometer mechanical boost gauge. My car has never had any boost leak issues that I know of, meaning the only check engine light I have ever had was for a faulty gas cap.
With a 15%, intake, header, exhaust, Bosch 380’s, and tune I hit 16-17 lbs of boost. If the outside air temps are below 50 degrees, that’s when I typically see the extra lbs of boost. I'm betting those bigger intercoolers are where they are losing power, I had a racing dynamics one, and was losing boost on the hot side.
With a 15%, intake, header, exhaust, Bosch 380’s, and tune I hit 16-17 lbs of boost. If the outside air temps are below 50 degrees, that’s when I typically see the extra lbs of boost. I'm betting those bigger intercoolers are where they are losing power, I had a racing dynamics one, and was losing boost on the hot side.
100%. I had a nice IC setup that came with my car and replaced with an oversized Alta IC with my tune. Peaked 16-17 psi max with a 19% pulley. This weekend I decided to put the smaller IC back on and she'll pull 18 psi all day, and that's when it was 95 degrees outside. Keeping an eye on intake temps and it maxed at 130. That's not much warmer than with the Alta.
If you're getting a used IC to replace it, pour some gasoline through it a couple times then rinse it out before your install. Without a catch can they collect oily residue over time and that makes them less effective. I did that and was amazed how oily the gas was coming out the other side.
09-15-2024, 04:01 PM
