Success! I tightened it by 3 turns, and that did 3 things. It made it hit 175kpa much sooner, 2997rpm instead of 3200, it mostly got rid of the fluctuations (now it fluctuates max peak to dip across the whole run 7kpa, which is much better than 23!), and it actually increased the wastegate value to 195 ish kpa. I wasn't necessarily looking to do that for a while, but it ran good once I raised the safety to 200 kpa, still very rich, still no ping, and now it pulls right up to 5000+, instead of dipping off with the fluctuations.
For the summer, the boost pressure should remain stable, but as winter approaches, you may notice that the boost pressure will increase. Keep an eye out for that!
On my car, I noticed the boost pressure (that was before I enabled closed-loop electronic boost control) in December was 10-15 kPa higher than in the summer.
For the summer, the boost pressure should remain stable, but as winter approaches, you may notice that the boost pressure will increase. Keep an eye out for that!
On my car, I noticed the boost pressure (that was before I enabled closed-loop electronic boost control) in December was 10-15 kPa higher than in the summer.
Interesting, I wonder why, I know when it's colder the air is denser and you'll get more power out of the same amount of air, but that shouldn't change the springs pressure, this is one of those things where you first look at it and it makes sense (cold air makes more power, more boost=more power), then my brain kicks up a gear and it doesn't make sense (a spring rated for x psi should be x psi no matter the temperature). Clearly I'm missing 3rd gear here, where it does make sense and have a logical reason, I'll look it up and see if I can find the answer instead of you typing out the scientific reason for this insignificant query haha.
Edit, I wonder if that is from the cold air getting heated up "more" than the warm air from compression (harder to compress denser air), even if it is still cooler, the temperature increase compared to warmer air might raise the pressure a bit, or it's from the denser air making more power, making more exhaust, spinning the turbo faster? Still I would think thata regulated x psi is still x psi no matter the temperature, oh well, that's enough for tonight!
[This message has been edited by 1985 Fiero GT (edited 07-01-2025).]
Interesting, I wonder why, I know when it's colder the air is denser and you'll get more power out of the same amount of air, but that shouldn't change the springs pressure, this is one of those things where you first look at it and it makes sense (cold air makes more power, more boost=more power), then my brain kicks up a gear and it doesn't make sense (a spring rated for x psi should be x psi no matter the temperature). Clearly I'm missing 3rd gear here, where it does make sense and have a logical reason, I'll look it up and see if I can find the answer instead of you typing out the scientific reason for this insignificant query haha.
Edit, I wonder if that is from the cold air getting heated up "more" than the warm air from compression (harder to compress denser air), even if it is still cooler, the temperature increase compared to warmer air might raise the pressure a bit, or it's from the denser air making more power, making more exhaust, spinning the turbo faster? Still I would think thata regulated x psi is still x psi no matter the temperature, oh well, that's enough for tonight!
As they say... I'm not a biologist (haha), but I'd imagine that the temperature changes would in fact affect the metal in the springs... though at temperature they should operate the same. But the denser air would likely mean more pressure... as you say, it would be harder to compress the denser air.
Originally posted by 82-T/A [At Work]: As they say... I'm not a biologist (haha), but I'd imagine that the temperature changes would in fact affect the metal in the springs... though at temperature they should operate the same. But the denser air would likely mean more pressure... as you say, it would be harder to compress the denser air.
If that were the case and summer to fall temps would change the rating of the spring, then you'd get insane fluctuations at other times (cold start would be huge boost, then as the turbo heats up it would reduce a lot, the wastegate gets baked being so close to the turbo), anyhow, I don't fully know haha.
So I'm at 640 ish kms now, no real problems at all. I had some impressive oil leaks, from a damaged axle seal and a disintegrated o ring on the dipstick tube, I replaced that and those leaks are no more. I think I have a little bit coming from the front main seal (tiny amount at the moment, so little it's hard to pinpoint, might just be residual from the big leaks). I did an oil change at 500kms, oil was still nice and clean, no sludge, metal or anything. I also had the oil pressure sender go out, I have it running the o2 sensor, and the switch wasn't the most reliable, then just stopped working. New oil pressure sender works perfect on the switch front, but seems to read lower than the last one (have a video of the last one reading 50 psi @ 1700 rpm @ 63°f, This morning the cold start number was 37.5 psi @ 1700 rpm @ 71°f) and the new sender idles at 20psi @ 975 rpm fully warmed up, 1 tick off the red. This is with new 10w40 conventional. Does that sound normal to you guys? This engine's spec is 15 psi @ 1100 rpm, so it's still above spec, but seeing it go down a bit from the old sender, and go down even more from my 2.8s sender (it almost never left 80 psi, the sender was definitely not working at all), just caught my attention. Is the new sender reading low, or the last sender reading high, or a little of both? What does the White Bug idle at warm? I'm positive that the oil pressure change is just the sender's fault, and not bearings or anything, because the oil pressure drop happened all at once with the sensor change, and hasn't dropped any more since, and I've already driven farther since that sender change than the bearings even lasted on the first iteration of this engine
I also got a tiny bit of pinging today when it was hottest, and that made me think back to the last couple times I've had that, I thought I fixed it by re timing the distributor, or enrichening the mixture, and after I had done those things the ping was gone. Then I realized that I had gotten gas at a different station than normal immediately after the first time, and the other time I didn't test it again immediately (no fun driving with the windows up trying to hear pinging when it's so hot, so I waited until it was cooler). So I looked at the octane I was running, it was the highest at the station I usually go to, which was only 90, no ethanol, the time I filled up at a different station and didn't have any pinging, I got 91 octane, so I think I was not using fuel with enough octane, as I've had encountered slight pinging maybe 3 or 4 times, usually at the hottest part of the day. I found out Shell sells 93 octane, so I topped off my tank with that, didn't have any pinging on the way home (it was cooler than this afternoon, but still windows down temperature). I'll have to see on the way home from church tomorrow if the splash of 93 fixed that, and if not then I'll have to burn through the rest of the tank and fully try 93 octane and see if that will do it. It won't cost any extra to use 93 octane, turns out in Maine 90 octane is ethanol free and more expensive, so with regular 5-10% ethanol 93 octane I'm only paying $1.40 cad/liter. PMBrunelle, what octane do you use? What boost was that good to before you had to use the water injection? or did you not wait to encounter ping before implementing the water injection?
[This message has been edited by 1985 Fiero GT (edited 07-06-2025).]
20 psi should be enough at idle. Shouldn’t your oil pressure gauge read in kPa rather than psi if it is a Canadian Z49 Fiero? I think that mine idles around 35 psi, but I don’t remember exactly.
How did you find TDC when you marked your harmonic balancer? Did you use a piston stop? Is your ignition timing what you think it is?
I never encountered knock with my car. I started running water injection more as a preventive measure.
I’m running 91 octane pump gas, which is available anywhere. Nowadays in Québec the pump gas has 10% ethanol.
As you are aware, the AKI of fuel is the average of the RON and MON, which represent two different test conditions for octane. So, depending on the running parameters of the test engine, you get a different octane measurement.
Some experienced tuners (not me, I saw this on Reddit) have reported that in a turbo engine, E10 has more knock resistance than pure gasoline with the same AKI. RON and MON test conditions are perhaps not fully applicable to turbo engines.
[This message has been edited by pmbrunelle (edited 07-06-2025).]
20 psi should be enough at idle. Shouldn’t your oil pressure gauge read in kPa rather than psi if it is a Canadian Z49 Fiero? I think that mine idles around 35 psi, but I don’t remember exactly.
How did you find TDC when you marked your harmonic balancer? Did you use a piston stop? Is your ignition timing what you think it is?
I never encountered knock with my car. I started running water injection more as a preventive measure.
I’m running 91 octane pump gas, which is available anywhere. Nowadays in Québec the pump gas has 10% ethanol.
As you are aware, the AKI of fuel is the average of the RON and MON, which represent two different test conditions for octane. So, depending on the running parameters of the test engine, you get a different octane measurement.
Some experienced tuners (not me, I saw this on Reddit) have reported that in a turbo engine, E10 has more knock resistance than pure gasoline with the same AKI. RON and MON test conditions are perhaps not fully applicable to turbo engines.
Ok, yes it's in kpa, I was converting to psi because most people on the forum are Americans, I forgot that you would also be in kpa, for the combined tach/oil gauge, it is divided into 4 sections of 20 psi, each with 4 ticks being 5 psi, with the first white tick off the red being 20, 275 is 40, 550 is 80
The first time I simply copied from the old balancer, the second time I used a screwdriver down the #1 spark plug hole and first rotated the engine by hand clockwise until I felt it wasn't going up or down, then went past and came back to TDC counter clockwise and did the same thing. I made note of the location and did that once more in each direction, and all results were within about 2* of each other, so I timed it to that new number, which was several (9 if I remember) degrees retarded from what I had it at to start with. I also reduced the spark tables several degrees from what you had so this engine would have no excuse to have any issues (which is probably why it didn't have any issues with the balancer being 9* off), so if my balancer is currently wrong, it would be wrong in the retarded direction unless my old balancer was more than 9 degrees more advanced (considering it ran the 2.8 fine at 12* timing (total of 11* more than "stock"), I doubt it was any more than that, and if it ends up a little retarded, that's fine.
Makes sense, so with the heat and compression of a turbo, ethanol free 90 would have been significantly worse than even just e10 91, well once I run this tank through and I get a really hot day with 93 I'll test again and hopefully I don't get any noises. And this pinging, I haven't really described it, it isn't metallic or deep, or really fast, it is just a little rattle, infrequent enough that I can discern each one, but to fast to count when it happens, so it isn't happening on every cylinder or even every combustion on one cylinder, I don't feel it in the way the engine runs, and it's pretty quiet, so it's definitely extremely mild, but enough to want to figure it out. If 93 solves this, then I'll try a tank of 91 octane, see what the lowest I can go is before it happens again, so I know what I can use gas wise if I'm somewhere else.
Rodney had one last set of poly transmission mounts, so I ordered those, I'm going to order a poly engine mount from Fierospace.com, as Rodney's out of those, I also ordered Rodney's adjustable solid dog bone, because it was cheaper than his adjustable poly one, that should definitely tighten down the drivetrain movement, as there's definitely quite a bit at the moment, and I've heard bad things about the replacement rubber mounts that I have now.
More driving today, now at 3/4 tank 93 octane, 1/4 tank 90 octane, still had the ping, and this evening I actually hit boost cut again (was pretty cold and rainy out, so that confirmed that temperature effects boost, somehow haha).
I was looking at the spark timing I was using (from an older tune from the White Bug), and looking at the spark timing other people have used (some other msqs from the megasquirt forum, and the tables from the book "high performance Fieros"), and I see that under boost (specifically 200 kpa), the timing was between 10 and 18 degrees more advanced (in the book, they use a 3.4l, iron head, and the timing is 0 across all rpms @ 200 kpa, whereas I had up to 18*, others on the megasquirt forum (Ericjon262 was one I saw I think) were in the 8* range, in my initial setup I had lowered the timing 4 degrees from what it was (so up to 14* at 200 kpa, seemingly without effect), so now I've put in the table from the book (above 100 kpa, no point messing with the vacuum timing that I know works fine), tomorrow I'll see if that finally gets rid of my pinging, if so I'll wait for a good hot day to increase it incrementally until I get the ping back, then know what the limit is. Afr is at 10-11 across the rpms at 200 kpa, so I know I'm not going lean.
It is knock, and not the “spark blowout”? “Spark blowout” is a misnomer as it designates the failure to initiate a spark when the cylinder pressure is too high. Reducing the spark plug gap is one way to facilitate spark formation.
Removing and inspecting the spark plugs may give you some hints about how the engine is running.
Is your intercooler working with water/antifreeze circulating?
Excessive ignition timing retard is not necessarily "safe", because the exhaust gas does not fully expand (and hence cool) inside the cylinder. So the exhaust valves and exhaust manifolds are subjected to high exhaust gas temperature.
You may need to reduce the boost pressure if you have a knock problem that you cannot otherwise solve.
There are aftermarket wastegate actuators with replaceable springs sets which you could use to fine-tune your boost pressure. I have one from Tial. Turbosmart sells another one.
It is knock, and not the “spark blowout”? “Spark blowout” is a misnomer as it designates the failure to initiate a spark when the cylinder pressure is too high. Reducing the spark plug gap is one way to facilitate spark formation.
Removing and inspecting the spark plugs may give you some hints about how the engine is running.
Is your intercooler working with water/antifreeze circulating?
Excessive ignition timing retard is not necessarily "safe", because the exhaust gas does not fully expand (and hence cool) inside the cylinder. So the exhaust valves and exhaust manifolds are subjected to high exhaust gas temperature.
You may need to reduce the boost pressure if you have a knock problem that you cannot otherwise solve.
There are aftermarket wastegate actuators with replaceable springs sets which you could use to fine-tune your boost pressure. I have one from Tial. Turbosmart sells another one.
I don't think it is spark blow out because I've had the same symptoms intermittently everywhere from 175 kpa to 195kpa after the wastegate adjustment, but always around the same rpms. It was a hot day today so I did some driving at 0*, no symptoms at all, then I split the difference to what I had, so now it peaks at 7* at 200kpa, and I had no symptoms again. By that point I was overheating (can't hear the knock with the windows down or fan turned up and no AC) so I didn't test any further. I can check some plugs tomorrow, I had them gapped to 0.040", with an MSD coil, fresh wires and distributor, what should I look for on them/what should they be gapped at?
To the best of my knowledge the intercooler is fully functional, whenever I stop driving, it is cool/cold (compared to the rest of the engine bay) to the touch, and there is a noticeable temperature difference between the silicone air tubes going into it and the ones going out of it, I also see the iat sensor (installed in the water line) go up a few degrees when doing an acceleration, then return to ambient or very close.
My thoughts are that my setup is different enough from yours to significantly impact correct spark timing, for example using the distributor vs the 7x wheel, putting more play into the measurement, and of course the little bit of uncertainty around the balancer marks. Hopefully my knock does not return, I'll look at some spark plugs tomorrow.
Would minor spark "blow out" or any other things give me those symptoms, a very small rattle like sound, no loss in power or other change in the way the engine is running or feels. I almost feel it is something totally different, maybe something related to drivetrain movement, or something, just because of how small and quiet it is, and how random yet reoccurring it has been.
Checked my spark plugs, a little sooty, but the insulator and tip are a lighter gray. No buildup, erosion, slime, etc.
Plus 1-6
All of them looked very similar in person, my phone camera is pretty bad, number 1 and 3 are the closest to how they look in person the other ones showed up darker on camera than they are.
Spark gap was at 0.045", with one at 0.050". I lowered them all to 0.040" to be on the safe side, and then did a little more driving, with no ping/knock.
I ran 0.030” spark plug gaps for a long time, but in more recent tests in the 210-215 kPa range, the engine misfired, so I backed it down to 200 kPa. In my next steps, I think I will try 0.025” gaps and then see if I can increase the boost again.
A misfire will be accompanied by a power loss. Knock will not necessarily cause a power reduction.
I don’t see anything horrible on the spark plugs, but obviously the idle/cruise mixture seems like it’s still too rich. I guess it’s on your to-do list.
Are there any altitude changes with your driving? The greater the altitude, the greater will be the pressure ratio (and therefore temperature rise) of the compressor. Hotter air will be more knock-prone.
I ran 0.030” spark plug gaps for a long time, but in more recent tests in the 210-215 kPa range, the engine misfired, so I backed it down to 200 kPa. In my next steps, I think I will try 0.025” gaps and then see if I can increase the boost again.
A misfire will be accompanied by a power loss. Knock will not necessarily cause a power reduction.
I don’t see anything horrible on the spark plugs, but obviously the idle/cruise mixture seems like it’s still too rich. I guess it’s on your to-do list.
Are there any altitude changes with your driving? The greater the altitude, the greater will be the pressure ratio (and therefore temperature rise) of the compressor. Hotter air will be more knock-prone.
Ok, interesting, none of this has ever had an accompanying power loss, the only symptom is the sound.
Yes, I wanted to figure out this sound before making anything leaner, but I will work on that.
There are lots of small altitude changes as I live in the Appalachians (basically this whole area is just a bunch of large hills, so there are dozens of changes in a drive, none super big though that I know of), that could certainly be a factor to, my ECM has a barometer built in although I don't think I have any of those features tuned or turned on yet.
I did a little more driving in 1st Gear, and I think it is fairly similar to the 4 speed in terms of bucking, maybe less, definitely not more,
