Cyber's 2001 S4 Build

[Cybersombosis]

I finished the install of the MAP sensor. It went smoothly. Here are some pics.

IMG_3266.jpg

IMG_3267.jpg

I can unhook the MAF connector and swap back and forth at will. We’ll dial in the fueling and max out the OEM MAF first before we switch to speed density.
IMG_3269.jpg

IMG_3270.jpg

IMG_3273.jpg

[CELison]

Do you have to tune around having the map after the TB? Can there be situations at partial throttle where you have higher pressure before the TB and lower pressure after it since the blade itself will be a restriction? If that even matters.

[Cybersombosis]

The tuner says for speed density, the secondary MAP sensor needs to be in the intake manifold. Basically he says that the pre throttle body MAP sensor is acting like a boost sensor or thrust sensor as Bosch calls it so can’t actually measure manifold pressure because it’s pre throttle body, but the post throttle body sensor is truly functioning as a MAP sensor, manifold absolute pressure since it’s installed in the manifold.

As far as the pressure differential before and after the throttle body, he says it’s built into the ecu by default. You need to know the ratio yes and there is situation where thats a factor but it’s nothing to do with speed density.

[CELison]

Gotcha. I didn’t read all the posts. I thought you just moved the map to after the TB.

[Cybersombosis]

Ya the secondary MAP uses the MAF wiring connector. I made an adapter from a spare MAF I had. I didn’t want to snip any wires. I can use the OEM MAF to get the fueling spot on, max that out, then swap over to speed density. One of the reasons for going this route is the limitations on a B5 RS4/B6 S4 MAF up to 500g/s. No limitations with speed density.

[Cybersombosis]

Ok so a small update, I thought I had gotten away with no issues after install of the engine but alas, I wasn't so lucky. Had this annoying oil leak from the first day of install. It would drip down off the turbo and onto the silicone charge piping. Had me baffled for the month I’ve had it up and running. I was like oh crap, hopefully it’s not the oil line feed that's totally hidden. Went in with a bore scope and it was dry, thank goodness. Looked at a banjo fitting and it was covered in oil and thought, voila! Found it. Had a hard time getting to it but got a wrench on it and tightened. I was happy that I found it. Next day the oil is still dripping. WTF? Took the scope out again and had a closer look. I had a DUH moment. The banjo I had tightened was the charge air banjo and of course doesn't have oil. The oil was coming from above the metal coolant pipe between the two heads and it had a drip coming from that area. Turns out the new cam seal I put in when rebuilding the head was faulty. Dripped from there and down the coolant pipe on to the turbo boost reference line for the N75. Luckily I didn’t break the boost reference banjo as it would have been a big hassle to replace it. No more leaks!!!

Another issue I've been having is overboosting. The tuner set me up with a wastegate file and when I went for a pull, it was boosting to well over 25PSI, enough to max out my boost gauge which is just a 2.5 bar sensor. I thought I was only hitting 22PSI but I was losing traction in third on a damp road and after some thought, I just maxed out my boost guage and 2.5bar MAP sendsor. The car felt GREAT and a little scary but great none the less. The tuner immediately told me something is wrong so I had to investigate the next day, albeit a little disheartened. Hooked up my compressor set to 20psi to the wastegate lines and sure enough, HISSSSSSSSSS. Damn, it's down by the turbo. Sure enough after removing the airbox and charge pipes, I found the culprit, a split hose at the wastegate. I don't wish that on my worst enemy.

IMG_3301.jpg

Lots of swearing and busted knuckles later, I finally was able to put a replacement on from my spare engine.

Went out for a test run and now it's behaving properly. I've now maxed out the MAF so that is no longer being used. Speed density her we go. I went out to do a 5 runs for the tuner last night at 10, 20, 30, 40 and 50% WG duty cycle so he can build a linear boost table for speed density. Hopefully that's it for issues and we can get this thing dialed in.

[travis_w]

How was the tuning experience from speed density? I assume the same.

Sent from my SM-S928U using Audizine Forum mobile app

[Cybersombosis]

Ya basically so far I’m having to do multiple runs with specific duty cycles until he builds the grid and figures out the compressor maps then he can dial the tune in. Not much different on my part vs. MAF tuning at this point.

[travis_w]

You still using the stock intake right?

Sent from my SM-S928U using Audizine Forum mobile app

[Cybersombosis]

Ya so far. I haven’t done the mod yet to the airbox. We’ll see how it goes and if it’s a huge bottleneck but if it isn’t, I’ll keep the stock look for the OEM win.