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I would also check your CPS or perhaps just swap to a new one. Look for wire damage and check resistance against the Bentley specs. When checking electrical things, it’s a good idea to check them at the DME with a voltmeter across the appropriate pins. This validates sensor operation and the wiring all the way to the DME.
What’s the mechanical history on the engine? Fresh rebuild, high mileage, or something else?
Pretty much unknown. Bought it 1.5 years ago with “maybe 175k” on it.
I installed an IJ crank scraper, pan baffle, and did all the mounts while i was in there. After starting it back up, it sounded horrible. It would appear that the rubber mounts dampened a lot of the sound.
Anyway - turns out that the part of the head casting that goes over the rocker arm shaft cracked off and the rocker arm shaft was bent. I probably ran 6 events with it like this!
Fast forward - new head, new cam, new IE HD rockers, etc.
Bottom end is still somewhat of an unknown.
I think the AFM is definitely the first place I’ll look. The plastic cover was removed prior to my ownership and never RTV’ed back on (it’s on there just loose) so who knows whats been done to it. I’ll look for another one.
Given that your AFM has been tampered with, I think you are on the right track with swapping. I’m not a believer in adjusting the AFM spring…
With a high mileage bottom end and fresh head, you could expect balanced horsepower and torque in the the high 140s or possibly low 150s.
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I think I had one pull at 151/151 but who cares!!
Eric and I ended up with very similar results, but I actually made less power at a dismal 139HP as you can see below. Both of our cars had the A/F richen up to 12:1 at about 4,800, although I didn’t seem to have the big dip that Eric did. After 4,800 both of ours picked up power as soon as the the A/F richened.
The strange thing is that almost everybody who was making good power, say for example, Aaron with 157hp, was actually closer to a 14:1 A/F ratio throughout the rev range if I remember correctly.
After taking a look at my torque and HP curves, Sumpter had suggested that the AFM was to blame. I swapped out my original AFM for one of those re-manufactured units not too long after getting my car, as we were having a lot of idle issues and the AFM seemed to have been tampered with. The problem is that I also had a massive vacuum leak caused by that valve cover breather being routed into an open catchcan. I believe there were some other things that were sorted out and the thing finally runs well at idle, but no one fix on its own actually remedied the idle issue.
A few people have said those remanned AFM’s can have issues, so I’ll swap back to the original AFM and see if that changes anything. The engine did have a refreshed head put on it right before I took possession of the car, and there are quite a few signs that it may have been a rushed assembly, so another vacuum leak (perhaps intake manifold gasket) wouldn’t be out of the question. I’ll check the other usual suspects that Scott and Brian pointed out as well.
I did spin the engine backwards for just a moment in December after a lost argument with turn one, but I would think a bent valve would be making some substantial racket. I’ll definitely perform compression and leakdown tests just to be sure.
Spinning an engine backwards won’t bend a valve.
Running the hose from the rocker cover to a bottle won’t cause a vac leak as long as you block off the hose’s port at the throttle body.
There’s remanufactured AFMs and there’s refurbished AFMs. The guy that does the refurb is out West. He says he has a fixture that calibrates his AFMs before he sends them out. I don’t gainsay the guy. All I can say is that I talked to him and he seemed to have his act together. Contact info is here in the forum somewhere. Search for AFM and my username.
Since the mixture got pretty good at high rpm but the hp didn’t, it might be a mistake to focus solely on engine management. Might be both an engine management problem and a weak engine.
It’s awesome that you guys got F/A data this time around, wtg. Did you get the data files too? If so, you can download WinPEP and create your own graphs. This is a big help on zeroing on issues. You can, for example, create a graph from 4-6400k rpm and F/A 12-14. This really zooms in on what’s going on.
Aaron and Ryan were instrumental in gathering the data and the numbers will prove to be important in understanding the dyno test. There were two pages printed for each customer, one for you, one for them. Perhaps they can bring the data with the or forward to you.
Thanks to everyone that came out. Inspections are out of the way and we’re ready to hit the track.
RP
Thanks again to the Whitingers for helping to organize the day. It would be great if you can scan all the dyno sheets to a single PDF then upload to a public space so anyone interested could download/review.
I haven’t had a chance to put in a new AFM, however I did show my dyno results to Eric Schieb over at Electron Speed (they support Bimmerworld’s racing team and many others from an electronics/engine management standpoint) and he was most suspicious of the O2 sensor. Mostly because the A/F ratio is consistently wrong, but it is consistent.
I tested the sensor using the methodology described here http://www.verrill.com/car/idle/e30_o2test.shtml which gave a reasonably consistent ~.77v. If I’m reading that page correctly, it should fluctuate quite a lot?
Has anyone else ever tested their O2 sensor? What values did you see? Were they consistent or fluctuating?
If the O2 sensor is the issue, it’s an easy fix, but I’d rather not buy an $80 part without justification.
Alex - Since you had similar results to me, I wonder if your O2 sensor would show the same values?
Quick edit - After re-reading that link, if my sensor is reading a high voltage, it’s indicating that the engine is running rich, which would then cause the computer compensate and run it lean. In actuality, the engine is good and it’s being leaned out due to a false rich reading. Did I read that right?
It is my understanding that the O2 sensor input is completely ignored by the DME when at WOT. I would love for someone to prove me wrong on that though.
The O2 sensor doesn’t play in open loop (WOT). The way the O2 sensor could goof the mixture is by causing problems to LTFT (long term fuel trim). If the O2 sensor was reading rich, your DME would dial back the injectors. This would make you always lean.
Your DME goes to open loop when the TPS senses WOT, or when the AFM door fully opens (4000-4500rpm I think). At open loop it no longer listens to the O2 sensor, yet the LTFT fuel map adjustment still plays. Therefore the LTFT adjustment the DME learned at partial throttle is applied at full throttle.
Note what this learned LTFT means for swapping parts. If you power off the DME or replace an engine management part, you have to give the DME an opportunity to reset LTFT. This means some time at partial throttle, since learning doesn’t occur at open loop. How much time I’ve never been able to figure out, but I’d guess less than a minute or two.
I don’t think there’s a good test for how well the O2 sensor is working. Sure, you can test to see if it’s basically functional, but a CEL would probably tell you that. Testing to see if it’s working “well” would be a whole 'nother can of worms. As a narrowband device it’s oscillating between on and off based on AFR. A person would probably need an oscilloscope and a calibrated AFR source to ID how well the sensor was working.
I have a F/A meter on my dash that is connected to my Traqmate. I installed it in '09(?) when I spent much of a season fighting engine management issues that I couldn’t seem to beat. The F/A meter told me I was running really lean. That would have fixed me up pretty quickly but, sigh, at the time I didn’t believe what it was telling me.
The other really handy gauge on the dash is fuel pressure. Eventually everyone experiences mysterious engine management issues. Having gauges like that on your dash gives you a baseline for normal behavior, and give you important clues when trouble strikes.
I haven’t had time to mess with the car at all, but I don’t believe the O2 sensor is our issue, Eric. I replaced mine over the summer after the old one blew out of the manifold from stripped threads; so mine is practically brand new. As Scott said, it shouldn’t be using the O2 in open loop anyways.
What I find strange is that my engine made good power (155 or so) back in 2013 with the previous owner. I really wouldn’t think that the less than 10 track days I’ve done with it would have worn it to the point that it would be making as dismal power as it is. I’ll preform leakdown and compression tests, but I still think there’s an issue else where. That spike in the AFR obviously indicates that there’s something going on with the feedback to the DME. My first suspect is going to be the TPS.
By the way Scott, it is indeed one of those refurbed units from who I believe is Bavarian Restoration. His process seems to be very thorough so I see no reason why the AFM would be bad. Some others at Balanced had mentioned that they’ve had problems with those AFM’s in the past though.
+1 for the TPS. The DME may not know its at WOT. FWIW, mine was running way lean because the fuel injectors were the wrong model. Seems basic but worth checking.