7730 engine management

[The Dark Side of Will]

[series8217 added this]: This post was split off from a discussion on 7730 engine management that started from this thread:
http://realfierotech.com/phpBB/viewtopic.php?t=6940
[back to Will's original post]:


The primary advantage of the 7730 is the ability to run $8F code from a Turbo Grand Prix. This program has thoroughly tunable boost control algorithms built into it. The rate of boost onset is even tunable (GM slowed boost onset to help extend transmission life).

[Aaron]

The primary advantage of the 7730 is the ability to run $8F code from a Turbo Grand Prix. This program has thoroughly tunable boost control algorithms built into it. The rate of boost onset is even tunable (GM slowed boost onset to help extend transmission life).

I wouldn't say this is a primary advantage. Although it may be useful, not in most of our applications. I, like most here I suspect, want boost to come on as quickly as possible, and get to max as quickly as possible. Furthermore, it's already been proven that the stock Fiero ECU is capable of tuning for boost, as Shaun is using it. So to me, the DIS ICM and ESC are the two biggest advantages.

[The Dark Side of Will]

The OP has a turbo. Boost control/boost awareness is the most important characteristic an ECM can have, bar none.

Knock sensor capability is a close second. However, without boost capabilities, sensing knock is of questionable utility.

[Aaron]

The OP has a turbo. Boost control/boost awareness is the most important characteristic an ECM can have, bar none.

Knock sensor capability is a close second. However, without boost capabilities, sensing knock is of questionable utility.

I completely agree that the ECU needs to be able to fuel and adjust timing for boost, but past that, it doesn't really need to know or do anything, and doesn't need to control boost. That's what the wastegate is for, and if you use a good wastegate, it's reliable and durable.

I'm not sure what you consider "boost capabilities." It doesn't take much to get a stock PCM to run a boosted engine. It does not change that much, it just uses different fueling tables, that most of the time are already in the PCM. And in my case, it doesn't change the timing curves at all. All my piggyback does it change the MAF values. The PCM does the rest like nothing's changed.

I'm not saying you can go push 10psi through a stock ECU. It's obviously critical that you tune for the boost. But this isn't difficult, most routes you go. Darth has done quite a few, 2/3 bar map sensor, and adjusting the voltage/air relation. If this is all you call "boost capabilities," then we're on the same page, and I'm just not exaggerating its complexity.

[lucky]

Aaron, Will, the PRIMARY advantage of the 7730 is that it updates every 1/10th of a second, while the stock fiero ecm updates every 1.6 seconds; hence the big improvement in driveablility.

[Aaron]

HA! I WAS FUCKING RIGHT. YEAS!!!!!!!!!

Albeit for a reason I had no clue existed. Thanks for throwing that out there.

[lucky]

I got that little nugget from one of Sinister's threads, don't recall if it was here or on Pee Eff Eff..


Lookin good dgz :thumbleft:

[The Dark Side of Will]

Aaron, Will, the PRIMARY advantage of the 7730 is that it updates every 1/10th of a second, while the stock fiero ecm updates every 1.6 seconds; hence the big improvement in driveablility.

That's only the data stream.

Yes, the engine runs better, but that's because the ECM is newer than the Fiero computer. The algorithms are more extensive and more capable because of the faster processor and larger memory space.

I'm not saying you can go push 10psi through a stock ECU. It's obviously critical that you tune for the boost. But this isn't difficult, most routes you go. Darth has done quite a few, 2/3 bar map sensor, and adjusting the voltage/air relation. If this is all you call "boost capabilities," then we're on the same page, and I'm just not exaggerating its complexity.

The tune is vitally important The ECM must have awareness of manifold pressures above atmospheric.

I don't believe in piggybacks. They are a bandaid for not having proper engine management.

[Aaron]

The tune is vitally important The ECM must have awareness of manifold pressures above atmospheric.

I don't believe in piggybacks. They are a bandaid for not having proper engine management.

My PCM tunes just fine, and it has no idea of pressure. All it knows is flow.

Damn good bandaid if you ask me. Can you give me one reason why my piggyback is bad, or worse than "proper engine management?"

[lucky]

I was gonna continue this, but I've decided I won't muck up dgzfiero's build thread any more. Sorry, dgzfiero.

[Shaun41178(2)]

split the topic if you have to as I don't want to ruin this thread

Nice work dgz. Is it running yet?

I would have put the MAT sensor after the intercooler not before the turbo. The computer needs to know what the airflow temp is going into the engine itself. After being compressed and intercooled, I am not sure what the temps might be and how much they would differentiate from ambient.

I ended up putting my MAT sensor in the intake manifold itself next to the power brake booster vacuum line on the end near the thermostat housing.

I like turbo setups, can't wait to hear how yours runs. :thumbleft:

[Aaron]

split the topic if you have to as I don't want to ruin this thread

I wish someone would, as I'm very curious to know how my stock GM PCM isn't proper engine management.

I would have put the MAT sensor after the intercooler not before the turbo. The computer needs to know what the airflow temp is going into the engine itself. After being compressed and intercooled, I am not sure what the temps might be and how much they would differentiate from ambient.

I like turbo setups, can't wait to hear how yours runs. :thumbleft:

I put my IAT before the turbo as well. My theory on it, is my engine can handle the more aggressive timing (No knock counts yet, gone up to 11psi and 7200rpm). I believe a good intercooler will be able to get the air back down to ambient (IIRC). I haven't checked my intercooler's efficiency yet, but I really want to.

I took like seeing custom turbo setups.

[The Dark Side of Will]

Can you give me one reason why my piggyback is bad, or worse than "proper engine management?"

Because it's using a NON-feedback system to manipulate the control inputs of a feedback system.

I put my IAT before the turbo as well. My theory on it, is my engine can handle the more aggressive timing (No knock counts yet, gone up to 11psi and 7200rpm). I believe a good intercooler will be able to get the air back down to ambient (IIRC). I haven't checked my intercooler's efficiency yet, but I really want to.

Lots of beliefs here, but they are irrelevant because they have no basis in fact.

The FACT is that pre-turbo and post-intercooler air temps DO NOT have a linear relationship. Therefore, your ECM is missing a CRITICAL variable in controlling your engine. You're feeding it rubbish and the reason you haven't blown it up yet is that you're not running it hard... The car's in CO, right? 14 psi of boost on 12 psi of ambient pressure is 11 psi of boost on sea level pressure.

Tell me again why your setup is good? It's got all sorts of fuxored control inputs, so you don't really have much idea what it's doing. You can't even read a datalog because you have to back out the manipulations that your piggyback puts in... but do you really know what those are beyond "make this bar taller"?

Not blowing up yet isn't a good answer because I'm using hose clamps on my fuel lines and my car hasn't blown up yet... :scratch: :thumbleft:

[Mach10]

Like walking through the jungle with a big shot of novocaine into each ankle.

You wouldn't know you have problems until you fell over and noticed the almond-smell coming from your black and green toes.

Feedback is ALWAYS better, because it makes no assumptions.

To be fair, though, as far as band-aids go, the SAFC isn't too horrible.

[Aaron]

Because it's using a NON-feedback system to manipulate the control inputs of a feedback system.

It still has feedback. Mys tock O2 sensor still works fine, and I can constantly see what the piggyback is doing. I can datalog with it, and see exactly what values it's changing, and by how much.

Lots of beliefs here, but they are irrelevant because they have no basis in fact.

The FACT is that pre-turbo and post-intercooler air temps DO NOT have a linear relationship. Therefore, your ECM is missing a CRITICAL variable in controlling your engine. You're feeding it rubbish and the reason you haven't blown it up yet is that you're not running it hard... The car's in CO, right? 14 psi of boost on 12 psi of ambient pressure is 11 psi of boost on sea level pressure.

Tell me again why your setup is good? It's got all sorts of fuxored control inputs, so you don't really have much idea what it's doing. You can't even read a datalog because you have to back out the manipulations that your piggyback puts in... but do you really know what those are beyond "make this bar taller"?

Not blowing up yet isn't a good answer because I'm using hose clamps on my fuel lines and my car hasn't blown up yet... :scratch: :thumbleft:

It isn't missing it, it's mearly getting a lower number. And that may not even be true. A good intercooler setup will get the air back down to ambient temperature. I don't think anyone could argue that mine isn't good, being it's one of the best you can buy. So if my IC is functioning properly, the IAT values it's getting should be pretty close.

I'm not running it hard. Ummm, ok. Not sure how you could argue 11psi and 7200rpm on a stock engine, 100 miles after the first time it's ever been started, is easy. But just wait. I'll go to the dyno, then you can decide what's hard. Because you don't know shit about how hard my setup is being run. All you know is basic numbers, that rely on many other things. So Matt laid down 415rwhp at 13-14psi IIRC. I have a bigger, better turbo, I have heads that flow 50cfm more than his, I have a better intake, a better throttle body, a better intercooler, a better exhaust, headers that put shame to his manifolds, a better crossover, and a better wastegate setup. This all leads to me making more power, with less boost. So despite me running less boost, I could very easily be making more power right now. You have no idea whatsoever.

For all these fucked up inputs, shit seems to be working out. No knock at WOT on any of my runs, and my A:F's are safe and flat at 11-11.5. I intend to raise those obviously.

It's easier than hell to read my datalogs. You look at the run, it recorded every cell it used in that run. You compare to the WBO2. Based upon 500rpm increments, when your A:Fs are off, you change the corresponding cell, which changes the adjustment to the airflow tables, which changes fueling. It's working flawlessly. And being that I've got the A:Fs tol hold a flat line, moving them up will be easy. I'm just waiting until I can test my intercooler's efficiency.

All my piggyback does is change airflow values. Isn't that what boosting an engine does? So I add boost, motor gets more airflow. I change airflow values.

[Jinxmutt]

Just wanted to add that I really wanted to put my IAT in the runner of my intake manifold but I was worried that it would heat soak. I figured that if the computer knew the temperature of the air as it was entering the cylinder, it would be able to more accurately calculate the amount of fuel/timing it should have.

I figured the sensor would be reading higher due to the conduction through metal and decided that putting it in the charge pipe just before the TB would be a better idea. I don't think the air temp is really going to change much from 6" before the TB to the intake anyways...

[Series8217]

Putting the IAT pre-turbo is stupid for all the reasons mentioned above.
The ECM is programmed to make corrections based on air temperature entering the cylinder. Not the turbo.

GM even put the IAT on the intake manifold on the 87/88 Duke cars. Good place for it, but I think the Duke manifold doesn't get so hot. You could build a phenolic bushing to isolate it if you're worried about that.

[The Dark Side of Will]

There are a couple of different styles of IAT sensors. Some apps like TPI engines left the factory with a metal capped sensor similar to a CTS. Others like the Fiero got open plastic elements that react faster. I've heard of people boosting TPI's swapping out their stock IAT sensors for the faster reacting ones.

Anyway, the turbo adds a distinctly NON-linear relationship between actual air temp and IAT sensor reading, when the IAT sensor is located upstream of the compressor. In this situation, the ECM is getting garbage for the IAT input and will produce inconsistent results.

MAFT's have a wire that "clamps" the IAT output to approximately 80 degrees. This is marginally better. Even though the output is garbage, it's consistent garbage. The tuner can then retune EVERY time the weather changes, or with every run he makes to compensate to changing temperature.

This is of course UTTERLY ABSURD because it fails to take advantage of one of the primary advantages of EFI: it can compensate for environmental variables with PERFECT CONSISTENCY, as long as it gets good sensor inputs.

The CORRECT way to tune EFI is to back the temperature compensations out of the datalogs BEFORE calculating adjustments to the MAF or VE tables.

If your engine was tuned to the gnat's ass at 70 degrees, and not running right when the temp goes up to 90, you SHOULD NOT adjust your base map... you should adjust your temperature compensation.

However, LOTS of people see their cars running a little off and make a change to the piggy-back or base map instead of the temperature compensation. This is wrong and counter-productive because the car never gets to a solid, reliable tune, but always dances around depending on the weather. This is not using EFI to its fullest capabilities. However, this is the description of tuning that everyone who uses a piggyback or an inaccurately instrumented ECM has come to accept as reality.

This is why using a piggyback is not a good long term solution. It snares you into making the "easy adjustment" instead of making the adjustment you SHOULD make. Because of this, the car never gets tuned correctly.

If temperature is properly compensated, the ONLY environmental variable that can throw a tune off is humidity.

[Aaron]

There are a couple of different styles of IAT sensors. Some apps like TPI engines left the factory with a metal capped sensor similar to a CTS. Others like the Fiero got open plastic elements that react faster. I've heard of people boosting TPI's swapping out their stock IAT sensors for the faster reacting ones.

The Fiero sensor is metal though, and screws in (At least mine did). I'm using a plastic sensor from the MCZ34, it just pushes in. So the Fiero sensor could be moved to my pressure side, post turbo and IC, but I want to make sure it is just as accurate as my current one before I do.

Anyway, the turbo adds a distinctly NON-linear relationship between actual air temp and IAT sensor reading, when the IAT sensor is located upstream of the compressor. In this situation, the ECM is getting garbage for the IAT input and will produce inconsistent results.

I do plan on moving it, but for now, it's not causing any problems, and the car is running consistently fantastic.

This is of course UTTERLY ABSURD because it fails to take advantage of one of the primary advantages of EFI: it can compensate for environmental variables with PERFECT CONSISTENCY, as long as it gets good sensor inputs.

True enough, but so far so good. The IAT doesn't change that much in the tables run. In fact, you can completely disconnect it, put a resistor in it, anything, and you won't really notice a difference. I have dyno sheets proving this. And it also only affects timing, not A:F. I also have dyno sheets proving this.

The CORRECT way to tune EFI is to back the temperature compensations out of the datalogs BEFORE calculating adjustments to the MAF or VE tables.

The IAT doesn't change the MAF or VE tables at all, just timing. Otherwise my A:Fs would be different everyday. They aren't. And they'd have changed when I ran my Z34 on the dyno with the stock IAT, without an IAT, and with a GTP IAT. They didn't.

If your engine was tuned to the gnat's ass at 70 degrees, and not running right when the temp goes up to 90, you SHOULD NOT adjust your base map... you should adjust your temperature compensation.

However, LOTS of people see their cars running a little off and make a change to the piggy-back or base map instead of the temperature compensation. This is wrong and counter-productive because the car never gets to a solid, reliable tune, but always dances around depending on the weather. This is not using EFI to its fullest capabilities. However, this is the description of tuning that everyone who uses a piggyback or an inaccurately instrumented ECM has come to accept as reality.

This is why using a piggyback is not a good long term solution. It snares you into making the "easy adjustment" instead of making the adjustment you SHOULD make. Because of this, the car never gets tuned correctly.

If temperature is properly compensated, the ONLY environmental variable that can throw a tune off is humidity.

As soon as my IAT is moved into the correct position, then my PCM is correctly tuned, and a change in ambient temperature won't affect my tune at all. However changes in ambient aren't affecting it as-is. I ran it this morning, 45* out, ran perfect. Drove it again this afternoon, 75, ran perfect. A:Fs didn't move at all. Ignition timing probably did, to some minute degree, as it was supposed to.

[Series8217]

True enough, but so far so good. The IAT doesn't change that much in the tables run. In fact, you can completely disconnect it, put a resistor in it, anything, and you won't really notice a difference. I have dyno sheets proving this. And it also only affects timing, not A:F. I also have dyno sheets proving this.

The CORRECT way to tune EFI is to back the temperature compensations out of the datalogs BEFORE calculating adjustments to the MAF or VE tables.

The IAT doesn't change the MAF or VE tables at all, just timing. Otherwise my A:Fs would be different everyday. They aren't. And they'd have changed when I ran my Z34 on the dyno with the stock IAT, without an IAT, and with a GTP IAT. They didn't.

What you're saying may be true for MAF cars, but is absolutely not true for speed-density, which REQUIRES an accurate IAT for air flow calculations.