Supercharged Issues Please Help!
Timing isn't a good reference point on performance. Running full OEM timing only says your car is OK. If it's really running well, you should be running a lot less than factory full timing. Combustion chamber efficiency is directly related to full advance timing, and a good combustion chamber runs about 7 degrees full advance. More advance means your efficiency is crap, and you're applying a bandaid for a poor combustion chamber design.
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Joined: Apr 2017
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From: Indiana
Timing isn't a good reference point on performance. Running full OEM timing only says your car is OK. If it's really running well, you should be running a lot less than factory full timing. Combustion chamber efficiency is directly related to full advance timing, and a good combustion chamber runs about 7 degrees full advance. More advance means your efficiency is crap, and you're applying a bandaid for a poor combustion chamber design.
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Driver School Candidate
Joined: Jan 2021
Posts: 19
Likes: 6
From: OREGON
Quick update: I did a boost leak test and there was quite a big leak at the blow off valve area, which is now fixed. However, the car is still having the same issues. If anything, it’s running way more lean now than before and I can barely go into boost. Anymore than 10% throttle and the car will start jerking repeatedly and it seems to do it anytime boost vacuum reaches 0 and is about to go into boost. I plan on getting my fuel filter looked at later this week and will report back the results.
Moderator
Joined: Apr 2017
Posts: 3,069
Likes: 978
From: Indiana
Quick update: I did a boost leak test and there was quite a big leak at the blow off valve area, which is now fixed. However, the car is still having the same issues. If anything, it’s running way more lean now than before and I can barely go into boost. Anymore than 10% throttle and the car will start jerking repeatedly and it seems to do it anytime boost vacuum reaches 0 and is about to go into boost. I plan on getting my fuel filter looked at later this week and will report back the results.
Thread Starter
Driver School Candidate
Joined: Jan 2021
Posts: 19
Likes: 6
From: OREGON
Thread Starter
Driver School Candidate
Joined: Jan 2021
Posts: 19
Likes: 6
From: OREGON
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Instructor
Joined: Mar 2018
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From: California
I’m not SC but I can say with certain that what the @dcguy says is 110% true! I had a bad MAF sensor a while back and my car ran like absolute trash. I could not figure out what was wrong for a while either because it would not throw a check engine light. Near redline it bogged and would shake. When I drove the car normal though it would have no issues. At WOT between 5k rpm until redline is where I had issues. Either it wouldn’t be able to redline or it would shake, bog and lose power, etc. eventually I tracked it down to the MAF sensor. Mine was clean and looked fine. I ordered a Denso one off rockauto and after installing it all my problems were gone immediately after installing it.
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Joined: Apr 2017
Posts: 3,069
Likes: 978
From: Indiana
I’m not SC but I can say with certain that what the @dcguy says is 110% true! I had a bad MAF sensor a while back and my car ran like absolute trash. I could not figure out what was wrong for a while either because it would not throw a check engine light. Near redline it bogged and would shake. When I drove the car normal though it would have no issues. At WOT between 5k rpm until redline is where I had issues. Either it wouldn’t be able to redline or it would shake, bog and lose power, etc. eventually I tracked it down to the MAF sensor. Mine was clean and looked fine. I ordered a Denso one off rockauto and after installing it all my problems were gone immediately after installing it.
Instructor
Joined: Mar 2018
Posts: 990
Likes: 352
From: California
Things I checked: fuel pump, fuel pump filter, spark plugs, ignition packs, wiring, RR tune, fuel, I also did a compression test. Eventually I just unbolted the MAF to look at it and it visually looked fine. I honestly can’t remember what made me order a new MAF but at that point I’m sure my mindset was what do I have to lose.
Intermediate
Joined: Oct 2015
Posts: 399
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From: Ok
Quick update: I did a boost leak test and there was quite a big leak at the blow off valve area, which is now fixed. However, the car is still having the same issues. If anything, it’s running way more lean now than before and I can barely go into boost. Anymore than 10% throttle and the car will start jerking repeatedly and it seems to do it anytime boost vacuum reaches 0 and is about to go into boost. I plan on getting my fuel filter looked at later this week and will report back the results.
Advanced
Joined: Feb 2014
Posts: 637
Likes: 97
From: CO
i have an sc isf and diagnosed multiple issues and installed myself. The maf is extremely sensitive. Check all of your piping and connections even the smallest leak will cause mayhem. Make sure your BOV is set correctly and is functioning properly, test the boost air line to the bov and make sure it is clear. A bad maf sensor will cause a ton of bogging issues as well. If you fixed a leak, reset your ecu the fueling will be all over the place when its used to a running with a leak. If rafi sent you a map to correct the issue might want to go back to a base map without any revisions. Did the shop need to extend the wires for the maf when it was installed? I would check their work, if its crimped or soldered poorly that will make a voltage drop in the readout of the maf sensor. Im going to bet on an air/boost leak somewhere and it makes sense that it has gotten worse over time. If you have an air oil separator even a tiny leak from that will cause multiple issues and difficult to diagnose as its a vacuum.
Thread Starter
Driver School Candidate
Joined: Jan 2021
Posts: 19
Likes: 6
From: OREGON
I’m not SC but I can say with certain that what the @dcguy says is 110% true! I had a bad MAF sensor a while back and my car ran like absolute trash. I could not figure out what was wrong for a while either because it would not throw a check engine light. Near redline it bogged and would shake. When I drove the car normal though it would have no issues. At WOT between 5k rpm until redline is where I had issues. Either it wouldn’t be able to redline or it would shake, bog and lose power, etc. eventually I tracked it down to the MAF sensor. Mine was clean and looked fine. I ordered a Denso one off rockauto and after installing it all my problems were gone immediately after installing it.
Last edited by ThatOneIS; Feb 2, 2021 at 02:13 PM.