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Hey guys, I’m wrapping up a DIY SC project on the 86.5. I was going to post the whole saga after I had dyno numbers in one hand and a drink in the other.
It won’t be for for faint of heart or the pure of soul.
But here’s tonight’s set back: driving it and the gains feel good, it’s cooling well and worth all the work, then pop, it shuts down and off on the side of the road.
I change my pants and see that the MAF is hanging out of the TB. I’m pleased that is all it was. I put it back in place and drove home.
Currently I just have new o-rings on the MAF, put clearly I need to fabricate a clamp or something else.
I remember researching before my build and reading that somebody had this issue and made a clamp to prevent the MAF from blowing off going from high revs to idle. Has anybody got pics or hints?
Many thanks, Dave H.
I had that problem on my S4. I tried many different clamps but had to get a silicone connector made that would hold 15 PSI boost ( http://928.jorj7.com/MAF-boot/ ). Even though it took care of most of the problem, the surge when closing the throttle suddenly also caused the problem. So I also added a quicker reacting Blow off Valve ( http://928.jorj7.com/intake/BOV.html ). Now I don't have that issue.
__________________
George
90 S4 Grand Prix White (Murf #5 - 219.0 mph top speed)
94 GTS 5-Speed Midnight Blue
06 Cayenne S Havanna/Sand Beige (PASM) http://928.jorj7.com
^^ I thought that maf boot looked familiar, the PO stuck one on my S4. Works great!
You could try installing shorter rubber buffers (or solid ones) on the air box mounts and see if that limits the movement to prevent the maf from moving back.
An easier thing to do though would be to do something similar to what George did and swap out 92811024302 (the rubber connecting hose for the maf) for a stiff silicone version.
It might be able to clamp down harder than the rubber factory part.
You may want to consider milling lips into the MAF. Use the stock boot and clamp. That's what I had done for my MAF. Credit to Kuhn Performance for the photo (http://www.kuhnperformance.com/model...-maf-machining)
Hey, thanks you guys. Those are great ideas and I appreciate the feedback.
Sorry, I should have explained the set up better in order to troubleshoot.
It’s a pretty random older model centrifugal SC mounted in front with a barrel intercooler. Just 3 inch pipe after the intercooler, which runs into a reducing boot on top of the MAF.
The manifold, TB, and MAF are in stock position. The pipe to MAF boot holds well, but the TB to MAF is the cause of concern.
This is where I will loose half my friends, but I ran out of room for the SC intake and vented the hood.
I found an old 924 Turbo scoop.
So is the boot coming off of the intake, or is the MAF coming out of the boot? If the latter, then milling the MAF will fix it. If the former, then that won't make any difference.
When I was running the rear turbo setup on my GT many moons ago, I had a similar problem. I was doing a high speed run when all of a sudden the power went away (hood lifted a bit). Thought I'd blown the engine. Found out that the MAF had popped out of the boot. I ended up putting a small bead of jb weld around the MAF and when the silicone boot slipped over it the clamp could hold it in place. The JB weld held well (still there actually) and didn't come out under boost ever again. (not as elegant as Kuhn's setup but I didn't have a milling machine LOL).
Hey guys, I’m wrapping up a DIY SC project on the 86.5. I was going to post the whole saga after I had dyno numbers in one hand and a drink in the other.
It won’t be for for faint of heart or the pure of soul.
But here’s tonight’s set back: driving it and the gains feel good, it’s cooling well and worth all the work, then pop, it shuts down and off on the side of the road.
I change my pants and see that the MAF is hanging out of the TB. I’m pleased that is all it was. I put it back in place and drove home.
Currently I just have new o-rings on the MAF, put clearly I need to fabricate a clamp or something else.
I remember researching before my build and reading that somebody had this issue and made a clamp to prevent the MAF from blowing off going from high revs to idle. Has anybody got pics or hints?
Many thanks, Dave H.
John Kuhn of Kuhn Performance has a number of different level solutions to this problem. More boost and more violent boost changes, more invasive the required cures. What boost levels are you running?
I would predict when done, low boost 4-6. I haven’t had it past 3000 rpm yet.
I was taking it to a pro tuner last week and the sucker shredded the SC drive belt on the way down.
I’m sure you guys saw the photo so it’s an old school tune at this point with an adjustable FMU.
I rebuilt the SC this week and should have done that before I installed it the first time.
In regards to the boot on the MAF: okay am I reading this wrong? Is there factory boot on the S3 that holds the MAF in the throttle body? If so my car didn’t have one when purchased. I had a boot going from top of maf to lower factory air box, but on the other end really just a big o ring set into the wall of the TB and a smaller o ring on the MAF. Good idea though and I will explore.
No, you are correct Dave. The boot options talked about here is for S4-up cars. Since your MAF plugs directly into the metal J-tube via O-ring, your solution will have to be different. Does anyone know what the Murf guys used on their S3 config? It looks like Carl's setup has a rectangular plenum back there so he may be mounting it to the same interfaces on the block as the stock airbox. My guess is that you will have to come up with some brackets to grab the tabs toward the top of the MAF and somehow interface with that cast J-tube. That J-tube has a flange (larger diameter) for the o-ring so this shouldn't be too hard to come up with something.
I found the old link I was thinking about, I would like to credit some body specific within the Norcal928 group but I couldn't find a name, maybe George knows?
Pretty impressive build, a lot of intuitive fabrication.
I found the old link I was thinking about, I would like to credit some body specific within the Norcal928 group but I couldn't find a name, maybe George knows?
Pretty impressive build, a lot of intuitive fabrication.
Bill Ball was the webmaster of the site when that was put up. He should know the source.
__________________
George
90 S4 Grand Prix White (Murf #5 - 219.0 mph top speed)
94 GTS 5-Speed Midnight Blue
06 Cayenne S Havanna/Sand Beige (PASM) http://928.jorj7.com
06-09-2020, 11:00 PM
Supercharger blowing off MAF
