MBC only setup, more data, and questions:
05-06-2004, 03:38 PM
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MBC only setup, more data, and questions:
Edit: perf. mods include K04s, X-chip v8, 5 bar FPR, JoeP MBC, LaBree DPs, Neuspeed G2, stock air filter, 710Ns, AMS TBB, samco f-hose.
Some of this was very puzzling to me, so I'm posting to try to get a grip on what's going on here. Today I hooked my MBC up *without* the N75 in the line, and did some logging. Here is the data:
First is a log of the boost, this is a 2nd and 3rd gear pull. I had to stop far short of redline, but you get the picture. Temp was 82 deg, humidity 29%, roughly SL alt:
<img src="http://filebox.vt.edu/users/chcampbe/Logs%205-6-04/MBConlyBoost050604.jpg">
Next is a log of the MAF readings (on separate 3rd gear pull):
<img src="http://filebox.vt.edu/users/chcampbe/Logs%205-6-04/MBConlyMAF050604.jpg">
A log of the timing (same run as MAF above):
<img src="http://filebox.vt.edu/users/chcampbe/Logs%205-6-04/MBConlyTiming050604.jpg">
And finally a scatter plot of the 3rd gear pull to give time perspective:
<img src="http://filebox.vt.edu/users/chcampbe/Logs%205-6-04/MBConly3rdPull050604.jpg">
OK, now first question is, why the hell does the boost look so low, and you'd think this looks like a perfectly good setup, just set at 14 psi on the MBC. I did not change the screw setting from the last setup I had, which ran the MBC in parallel to the N75, and I had the following boost plot:
<img src="http://filebox.vt.edu/users/chcampbe/MBCN75ParPlot.jpg">
Also, these runs felt like the car was pulling HARD, it sure didn't seem like 14psi. Where does the ECU get its boost "actual" reading from? Is this a calculated value? Could something be wrong with my ECU?
How does the timing look? It seems decent to me. I don't have it displayed, but the throttle never dipped below 100% once it was floored, so I definitely didn't have throttle cut.
MAF seems really low to me, it's even down from the 270 g/s max that it was before I took the N75 out, here is the old graph:
<img src="http://filebox.vt.edu/users/chcampbe/MAFlog42504.JPG">
The freakish thing is that I actually replaced my dirty old air filter with a brand new one, and got the poor numbers. When I took the MAF out to check it for dirt, it looked clean (although admittedly I don't know exactly what to look for).
Bottom line: according to the data, everything seems to be running a tick slower than before I pulled the N75 out, but the car feels like it just flies! Could I have affected the ECU sensors in some way by pulling the N75 (incidentally, I left it hooked up, just disconnected the two lines)?
Edit: btw, no fault codes showing except the two first bank O2 sensors (resistance too high), but then I assume this is because I have no precats (LaBree DPs).
Some of this was very puzzling to me, so I'm posting to try to get a grip on what's going on here. Today I hooked my MBC up *without* the N75 in the line, and did some logging. Here is the data:
First is a log of the boost, this is a 2nd and 3rd gear pull. I had to stop far short of redline, but you get the picture. Temp was 82 deg, humidity 29%, roughly SL alt:
<img src="http://filebox.vt.edu/users/chcampbe/Logs%205-6-04/MBConlyBoost050604.jpg">
Next is a log of the MAF readings (on separate 3rd gear pull):
<img src="http://filebox.vt.edu/users/chcampbe/Logs%205-6-04/MBConlyMAF050604.jpg">
A log of the timing (same run as MAF above):
<img src="http://filebox.vt.edu/users/chcampbe/Logs%205-6-04/MBConlyTiming050604.jpg">
And finally a scatter plot of the 3rd gear pull to give time perspective:
<img src="http://filebox.vt.edu/users/chcampbe/Logs%205-6-04/MBConly3rdPull050604.jpg">
OK, now first question is, why the hell does the boost look so low, and you'd think this looks like a perfectly good setup, just set at 14 psi on the MBC. I did not change the screw setting from the last setup I had, which ran the MBC in parallel to the N75, and I had the following boost plot:
<img src="http://filebox.vt.edu/users/chcampbe/MBCN75ParPlot.jpg">
Also, these runs felt like the car was pulling HARD, it sure didn't seem like 14psi. Where does the ECU get its boost "actual" reading from? Is this a calculated value? Could something be wrong with my ECU?
How does the timing look? It seems decent to me. I don't have it displayed, but the throttle never dipped below 100% once it was floored, so I definitely didn't have throttle cut.
MAF seems really low to me, it's even down from the 270 g/s max that it was before I took the N75 out, here is the old graph:
<img src="http://filebox.vt.edu/users/chcampbe/MAFlog42504.JPG">
The freakish thing is that I actually replaced my dirty old air filter with a brand new one, and got the poor numbers. When I took the MAF out to check it for dirt, it looked clean (although admittedly I don't know exactly what to look for).
Bottom line: according to the data, everything seems to be running a tick slower than before I pulled the N75 out, but the car feels like it just flies! Could I have affected the ECU sensors in some way by pulling the N75 (incidentally, I left it hooked up, just disconnected the two lines)?
Edit: btw, no fault codes showing except the two first bank O2 sensors (resistance too high), but then I assume this is because I have no precats (LaBree DPs).
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05-06-2004, 03:54 PM
#8
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From a retard who knows absolutely nothing....
Boost shouldn't taper at all if you have k04s and a MBC in place of the N75 valve. You "set it and forget it". It should keep a steady boost level from initial WOT to redline.
