LZ4 3500 V6 Swap

[The Dark Side of Will]

The crank position sensors are Hall effect in principle, but have built-in electronics that make them digital in operation.

Thus the exact value of the pullup resistor should not matter much at all. A larger resistor will make a slightly slower return to rail voltage once the sensor stops driving the signal low, but you'd need an oscilloscope to tell the difference. We're talking microseconds, maybe even nanoseconds, not milliseconds.

[pmbrunelle]

Pullup resistor value is more defined by noise immunity requirements than rise time.

[zok15]

Pullup resistor value is more defined by noise immunity requirements than rise time.

Can you elaborate on this?

[neophile_17]

This is how I see the resistor functioning.

The sensor is only capable of pulling the input to ground. The pullup resistor pulls the input high. You could think of it like a cam (sensor) and valve spring (pullup resistor). The cam can open the valve but without the valve spring the valve won't close and you'll have a mess.

Megasquirt operates with many types of sensors, so it is impossible to choose the perfect pullup value and incorporate it into the controller.
Capacitance and inductance from the sensor, wiring, and ECM induce ringing (noise) that gets worse the faster you switch the signal. Lowering the value of the pullup resistor will pull the input to 5V faster. This would allow a higher RPM if it was limited, but will use more power and cause more noise. Measuring parasitic capacitances and inductances from wiring and any that might be in the sensor is difficult or expensive so your average hobbyist is stuck with guess and check, or experience. If I find the crank signal is breaking up at high RPM I should be able to change the resistor with only minor annoyance.

[pmbrunelle]

Pullup resistor value is more defined by noise immunity requirements than rise time.

Can you elaborate on this?

Consider the limit as the pullup resistance tends to infinity. In this condition (with output driver switch open), the potential of the line is ill-defined, and any noise can easily change the potential of the line, in the worst case, causing the receiver to interpret a logic 0 where a logic 1 was intended.

The lower the resistance value, the "tighter of a leash" you have on the line potential, and the less it can be affected by external noise sources.

The lower limit to pullup resistance value comes with power consumption, heat dissipation of the resistor, and current handling capacity of the output switch. Furthermore, if the pullup resistor value becomes comparable to the on-resistance of the output switch, you have created a voltage divider, with a risk that the logic 0 level is not low enough to reliably be interpreted as a 0.

1 kΩ is a good starting point for automotive stuff.
470 Ω is possible if you have a good output switch, enough of a power budget, and you're feeling frisky.
10 kΩ can work in a car, but within a single circuit board where you are controlling the immediate environment. Probably ill-advised for something that runs in the vehicle wire harness.

Capacitance and inductance from the sensor, wiring, and ECM induce ringing (noise) that gets worse the faster you switch the signal.

Ringing can indeed happen, but I don't think you should be concerned about ringing due to the rise rate of a 1 kΩ pullup resistor. If you're going to be worried, you should focus more on the output switch which may have an on-resistance on the order of 25 Ω...

That said, in the automotive context, you're probably trying to build your module robust to damage from electrostatic discharge (due to mishandling), so the receiver probably has some resistance in series with the input line (and maybe a parallel capacitor). This input structure should give you the damping you need.

When it is practical, push-pull (the transmitter has a switch to connect the line to low voltage, and another switch to connect to high voltage) is preferred. The line is kept on a tight leash, without the power draw of a pullup resistor. Cam and crank sensors on my Fiero are push-pull!

Measuring parasitic capacitances and inductances from wiring and any that might be in the sensor is difficult or expensive so your average hobbyist is stuck with guess and check, or experience.

It's kind of hard to model everything, so if one has problems, it is probably best to probe your input pin with an oscilloscope and then add patches as necessary. A trap for beginners is that ringing can also happen in your oscilloscope leads, where none exists in the DUT.

[neophile_17]

Thanks pmbrunelle,

Those are good points about what is likely inside the GM sensor. Ringing probably isn't a likely here. I think a push-pull arrangement would be great. However, the mechanical housing of this sensor is complicated enough I'll deal with the pullup resistor rather than reinvent the wheel. You're making me feel better about choosing 1K for the pullup.

[zok15]

Thanks Patrick that was a good explanation. How would you find the lower limit practically? Trigger the sensor and measure resistance between signal and sensor ground? What magnitude difference in resistance would you want between the on resistance of the output and the pullup? How would you go about determining the current carrying capacity of the output switch?

I am only asking for theory, I have no intention of messing with it unless 1K works poorly, which is unlikely.

[pmbrunelle]

How would you find the lower limit practically? Trigger the sensor and measure resistance between signal and sensor ground? What magnitude difference in resistance would you want between the on resistance of the output and the pullup? How would you go about determining the current carrying capacity of the output switch?

Well if you're designing the system, you can look in your notes for information on the switch... or if it's a purchased part, you can ask the supplier for specs. If your buddy is working on the switch, you can walk over to his desk and have a chit chat over some coffee.

Oh wait, you're talking about the dark world of auto modification with limited information

If the (solid-state) switch is closed, and it's dropping more than 0.2 V, you're probably pushing too much current through it. That's a general feeling I have.

MOSFET switches behave like a normal resistor in the on-state, with voltage proportional to resistance. Can be measured with an Ohmmeter when "on".
BJT switches have a more constant voltage drop, not so much a function of current. Not measurable in the same way.

If you have access to the original vehicle in which the module was found, connect the ECU input pin (containing the pullup resistor) to ground via an ammeter. The current measured by the ammeter is equal to the current the switch normally handles. Copying the original application is probably a safe bet.

[neophile_17]

I've been trying to make progress on the exhaust but time has been tough to come by. I will be using the stock Impala front (firewall side) as well as the rear (trunk side) manifold. The original plan was to use a Saturn Aura manifold for the rear but the Y-pipe plumbing was going to turn into too much of a project.

From Zok15s thread-

You might disagree but I think the firewall side manifold is designed pretty good.

I'd keep that, and the crossover, and build a new trunk side manifold mating into the crossover somehow.

The trunk side manifold narrows down to a 1.8 inch hole for all 6 cylinders. It's very restrictive. So if it were me to save time and materials, I'd figure out the trunk manifold and redesign that and keep the rest.

I did port the Impala rear manifold to ~2.1" from the 1.8" stock size. With 2.5" exhaust there will be a step up just as the original system was in the Impala only 2.1"->2.375"(ID 2.5") instead of 1.8-2.125"(ID 2.25"). I'm telling myself that a short restriction isn't as bad as a long restriction. Dimpling headers made little to no difference on Engine Masters so hopefully that applies here. The other problem I had was getting a flange since the GM bolt spacing is really wide. I ended up tapping the manifold for a standard flange to eliminate that headache.

LZ4_neo17_1_Manifold.jpg (343.41 KiB) Viewed 2703 times

From Zok15s thread-

The stock LZ manifolds weld up ok, I tig'ed a set for the Gran Damn... was it worth it? probably not overall, because Gran Damn, but was it a cool project that kinda worked out ok? yeah.

I'm a little worried that I might have made the manifold wall too thin. How many miles do you have on that welded manifold? I'd like to have a backup plan if mine cracks.

I cut some access holes in the heat shield for the front manifold so that I don't have to remove it to tighten the bolts but it is by no means easy. For the rear manifold I think it will be easy enough to remove the shield. I now have both manifolds fully bolted on. Next up is to slice and weld the crossover to fit the clutch arm. I did this for the 3400 in the racecar so I'm confident I can make it work with minimal heartache.

[ericjon262]

I haven't really kept track, but I think somewhere around 800-1200 miles so far, the car is pretty much my DD at the moment, but since the weather's getting a little nicer, and I've got the new tank going in the Fiero, I'll probably start driving that more.

[Shaun41178(2)]

I t.

https://www.ebay.com/itm/155378021375?c ... 1&mkcid=28

So maybe keep the stock firewall side, use something like this for trunk side, merge them under the trunk.

Crossover then can maybe be wiggled enough to clear the clutch arm, as it won't be tied to the trunk exhaust manifold in a rigid location.

Scroll down page 1 I mocked it up so you can see how it would look

http://www.realfierotech.com/viewtopic.php?t=18377#top

[Shaun41178(2)]

Then do something similar to the 3800 guys.

C__Data_Users_DefApps_AppData_INTERNETEXPLORER_Temp_Saved Images_PICT0031.jpg (87.58 KiB) Viewed 2687 times

I also remember making a video. I don't think the trunk would have to be cut to fit the piping. I was talking about using a turbo here which would require trunk cutting.

So this is a route to take which I think other than fabricating headers would flow the best.

https://youtu.be/p0f3I-Q3Z9o

[zok15]

When I was debating using the stock stuff, I had decided that I would replace the trunk side manifold with a G6 manifold:

https://www.ebay.com/itm/374269720437?h ... R46m3trTYQ

And then run what was the crossover similarly to what Shaun posted with the 3800 above, but a little more similarly to stock with the addition of a Y pipe.

And yea Shaun I put the motor in my car with factory manifolds and there was no issues with the trunk, it actually was pretty perfect.



You can see that the flange is under the little shelf of the trunk which puts it with plenty of clearance around it. Also the G6 manifold is ever better for freedom of routing since the output flange is angled more.

[neophile_17]

Then do something similar to the 3800 guys.

This is reasonably close to my original plan. I have both the ebay linked manifold and the turn down manifold. I was going to use the turn down manifold and turn it into a Y. Getting the tube length similar would have been a hassle that I'm not willing to take on. Since the lengths will be unequal anyway I looked at the crossover style manifold. The crossover style manifold is really clean and we noticed no loss in power compared to log style headers on a ~210hp 3400/LX9 hybrid. At some power level the crossover manifold won't be acceptable. I guess we'll find out if ~250hp is it.

When I was debating using the stock stuff, I had decided that I would replace the trunk side manifold with a G6 manifold:

Sounds like we had pretty much the same plan. And then went in opposite directions from there...

[zok15]

The crossover style trunk manifold is very restrictive, it necks down quite a lot. If you stick with that I would definitely cut the manifold open and weld in some extra material to open that up a bit. You can weld in a new flange to run a 3" exhaust as well. Maybe some schedule 40 ss tubing and elbow to accomplish this.

Here is what Schwa Motorsports (Chris) did plus what I am suggesting including the elbow or just 3" straight tubing:



I do like how clean it is, but I want to run my wiring harness under the intake, and with the shift cables and intake tubing, it seemed cleaner to run my crossover under the motor. When I decided to do headers originally I was planning to still utilize a crossover over the trans, this would be the firewall side header:





The other issue I was running into was the collector is pretty large and it was getting close to the shift cables and things, and the tubing was going to be all stacked on top of each other just prior to the collector creating a real cluster, so I pivoted to where I am today. Routing the exhaust the other way really cleans up the tubing routing and flattens it out a lot.

[ericjon262]

another option that could be helpful, would be to look at G6 front manifolds, the point down instead of back, and might help with clearance to the trunk wall. I'll see if I can find a good picture of the manifold I'm thinking of.

Edit:

This one, and they're available new for $72

https://www.partsgeek.com/catalog/2006/ ... ifold.html

[Shaun41178(2)]

Yea I think that will point right towards the axle though. It might clear pending how tight a bend you need or can get away with.

Just something to keep an eye out for. 72 new is dirt cheap though. Wow.

[ericjon262]

Yea I think that will point right towards the axle though. It might clear pending how tight a bend you need or can get away with.

Just something to keep an eye out for. 72 new is dirt cheap though. Wow.

I have that manifold on the rear bank of the Gran Damn, it does point towards the axle, but it's easy enough to route the pipe around it. Also, not that it really matters, but it's easier to make both head pipes close to equal length because it's a bit further from the start of the front bank pipe.

[zok15]

Spring is here, any progress?

[neophile_17]

Spring is here, any progress?

My plan was to work on the car leading up to spring so that I could finally drive it. But we're moving, so the car moved to the back burner once again as house prep took precedence. Maybe in the fall...