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This is at about 4000 miles (yep, about to roll 100K after 10 years )
FL/FT/RL/RT
Also just can't seem to *quite* get back to the power I was at. I've checked for leaks multiple times, checked coils, replaced the plugs, tweaked on AFR... Here's a comparison from where I was sitting at 12psi (Red Line) on the last reman motor compared to where things are sitting now at 13psi (Blue Line) on the rebuild. I am thinking I must have got some tolerances wrong or something... Top end seems to land in the same spot but there is a considerable gap along the way. What is interesting is the load is actually showing higher on the lower power graph... I know I am running leaner in spots now, I was trying to make use of the WI, but tweaking higher or lower doesn't really seem to make much difference... Oh well, I am still happy with how it turned out, still a blast to drive and really moves, it isn't *quite* the same...
What's the deal with the boost profile on the blue line? Is the slight dip from no BC on the signal line to the WG now? It could be that this is causing the WG to crack open slightly under boost, causing less turbo efficiency. If there's no BC, throw one in there and see how that goes.
The "boost" profile is actually calc load, as I don't have a way to log boost.
Red line was no BC, just 12lbs of spring, blue was with BC. Even still I would have expected with the BC to be better. Load seems to indicate boost coming on sooner...
Tonight I swapped back to just 12lbs of spring with no BC to get an apples-apples comparison. I'll try to log tomorrow...
I agree and I actually did a test yesterday Red line is no WI, blue line is WI starting at 2psi and full at 15psi with a 7gph nozzle. There is a bit of a gap, about 10rwhp, but otherwise negligible. I let off early because I saw AFR climbing and wasn't sure how high it wold go without WI.
I switched back to just 12lbs of spring, no BC, and I am fattening up AFR to match what I was targeting in previous logs so I can get a true comparison of previous to current. Once I get a good baseline without WI I will add it back in and see how that looks...
I think I have a theory... Looking at past logs I previously mentioned my load is currently spiking much sooner than in previous logs. I also noticed my MAF reading is now much higher than previous. My old MAF had a pin break a month or so ago so I am running a different MAF now. With the load having a significantly higher value that retards timing and when I overlay timing logs I have a solid 2 degress pulled in current logs at the lower RPMs where power is really struggling to get back to where it was. At first I thought it might be my MAF calibration but the voltage is significantly higher also, I think this MAF is quite a bit different in response than the last. I am going to play with the calibration to see if I can get things to match up and see what the resulting power graph looks like...
Heh, so the current MAF hits 4.94V while the previous only reached 4.78V at the same boost. Only thing that changed besides the MAF was the rebuilt motor, but theoretically it should flow the same. Looks like I have a bum MAF... The old MAF wouldn't see the current MAFs voltage until 17+ psi...
Given Brettus' progress I figured I'd better get busy
Seems my theory on the MAF induced inflated load affecting timing and subsequently power seems to hold some water, though not so much down low yet where I anticipated more of an impact... I haven't gotten the new MAF yet but I have been playing with scaling the current one. I really need to replace it though, since I am hitting 4.94V at 12psi and 4.99V at 13psi and above, which is really out of whack. Still needs some work, but seems promising...
Red line is on new MAF adjustment, blue line is the same tune with the previous MAF scale and green is a past 12psi log on the old MAF.
I would be looking more at the maf setup or maybe even a vac. leak between maf and turbo rather than blaming the sensor .
I did consider a leak and did three leak tests. The things that are leading me to questioning the MAF:
1) No leaks found (not out of the question but so far none found so I need to start looking at other things).
2) The only things that have changed are motor rebuild and MAF sensor. MAF setup is same as before.
3) Replacement MAF is old, in fact 10 years old, as it came with the car.
4) The previous MAF only read up to 4.7'ish volts at 12psi and only reached 4.99V at 17psi. The current MAF is hitting 4.94V at 12psi and pegging 4.99V at 13psi. There is no way in my mind the sensor should be reading 4.99V at 13psi...
5) and finally... initially testing has exhibited results that match the theory...
I have seen some pretty crazy differences in maf output just from a slight misalignment of the tube/filter leading to it . Which is why I always tell people to fit a honeycomb these days .. do you have one ?
It is bigger than I prefer but I've been using it for over two years now. It has always worked well. Didn't see this high of MAF voltage prior to the rebuild with the old MAF. I also had to scale this MAF down in the cruise areas when I swapped from the previous. I just never got a chance to test boost before the dang pin corroded and fell off I'll experiment, could def be something else. But if I don't try I won't know. I didn't get this far by not tryin'
Some further data that is leading me to look at the MAF:
Previous MAF sensor idle voltage:
Current MAF sensor idle voltage:
Not saying this is it, just need to rule it out... Could be a total waste of time I don't see how it could be a leak prior to the MAF sensor, since all that is there is the air filter...
Do you have a screen in there or honeycomb? I could never get mine scaled right and happy with just the honey comb so I added an AEM screen at the front and that fixed the issue and I was able to get it perfect.
Heh, I have actually played with it both ways and it doesn't seem to make a difference in my case. But have been running with the screen on both with the previous MAF and prior to rebuild and now with current MAF post-rebuild. I had the previous MAF pretty well dialed in. It is just really odd to me that this MAF is hitting 4.94V 12psi, pegging 4.99 at 13psi, while the previous didn't hit that high until 17psi in the same configuration. Still waiting on Amazon to deliver the replacement...
Honeycomb only:
Honeycomb with screen, it is a little blurry but you can see it back there and it's flat...:
Ok, so I've been getting irritated waiting for the new MAF and decided to try putting in my old MAF housing that doesn't have the honeycomb and just run a screen. Well I noticed the honeycomb tube wall thickness is a bit thicker than the old housing so I measured them. The old housing is 85mm and the honeycomb is 83mm. With the old housing this current MAF, which was reading up to 4.94V @ 12psi is now only reading 4.86V @ 13psi. This effectively lowered the load reading, which advanced the timing and seems to have had a positive effect. So, it must mean that the previous MAF I was using is actually off, but it worked out with the smaller diameter housing... I am still wanting to test when I get the replacement MAF but here's results so far:
Red line: current MAF in 85mm housing @ 13psi
Blue line: previous MAF in 83mm housing @ 12psi
Green line: current MAF in 83mm housing @ 13psi
The red and blue load lines are much more analogous (though still not quite) than the green line...
No, I know it is confusing but I installed the honeycomb 83mm MAF two years ago after I had the wastegate relocated. I also bought and installed a new MAF sensor from Amazon at the same time. I scaled the MAF in that housing and had plenty of headroom, voltage-wise and ran like that until just a couple months ago in August when one of the MAF pins corroded and broke off the sensor. So I put my old MAF back in, the one that came with the car. I had to tweak it a bit but it worked. But I could not get my power graphs to match up with past logs. Then I noticed I was hitting really high voltage at only 12psi, which I had not experienced before. That sent me down this rabbit hole. I figured it was the MAF but seems it was more the housing. It was just blind luck that the Amazon MAF I bought before was off to match up with the housing that was too small. I still have another MAF coming from Amazon, I bought another from the same seller so hopefully it will respond the same. But then again they may just be junk and respond wildly different...
I'd likely agree at this point. Years ago pre-turbo days I got a sensor from eBay that read very high voltage relative to the original sensor, even in the MS CAI housing, which is actually 86mm. I just never noticed, or took the time to measure and verify the diameter on this honeycomb MAF housing. The housing I have installed right now is 85mm. It is amazing how much difference a few mm makes....
Honeycomb 83mm:
Honeycomb wall thickness, 3mm!
MS CAI diameter 86mm (measuring on bottom of ruler):
I find it interesting that the power drop-off conincides with the MAF response crossover. Not sure what, of if this means anything...
Also, am I wrong in thinking that load and manifold pressure are related? I am pretty comfortable with tweaking my MAF scale at idle and cruise ranges but for the high boost stuff I was thinking that I could loosely correlate 200% load with 1 bar manifold pressure... no?
10-11-2016, 10:41 PM
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I'll experiment, could def be something else. But if I don't try I won't know. I didn't get this far by not tryin' 
