Bone stock 528e with Megasquirt

E28 technical advice asked and given! Troubleshooting, modifications and more.
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turbodan
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Joined: Jan 09, 2007 10:19 PM

Bone stock 528e with Megasquirt

Post by turbodan »

Image

This is the fuel map a few days into tuning this thing, I thought the features were interesting. Peak torque is around 3200 RPM, this main hump in the fuel map is visible. Around 1800 RPM though there is a secondary hump, perhaps a second resonance in the long runner manifold. It is tuned up to 85 kpa, the top three rows are just placeholders for now.

I was really on the fence about going further with building this thing. Eventually I got tired of fighting with Motronic. I was utterly unable to achieve a satisfactory idle with the stock injection, and there were some occasional drivability hiccups that were irritating as well. If I'm going to slap a turbo on this car, Megasquirt removes several obstacles. In the mean time, I can finally enjoy a buttery smooth idle and full fuel and ignition control.

The MAF knocks about 2 kpa off of manifold pressure at WOT. Not a significant restriction, although it is susceptible to wear and tampering which is likely to subtract power and increase fuel consumption.
beaseac
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Re: Bone stock 528e with Megasquirt

Post by beaseac »

Which megasquirt are you using? I bought a k-data but haven't used it yet.
turbodan
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Re: Bone stock 528e with Megasquirt

Post by turbodan »

This is a MSPNP setup from diyautotune.
beaseac
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Location: South Carolina

Re: Bone stock 528e with Megasquirt

Post by beaseac »

Awesome. Can you share your tune so I will have something to start with?

Thanks!
Adam
88 528e
Ju@n
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Re: Bone stock 528e with Megasquirt

Post by Ju@n »

Seems like a good map, buttery smooth, and shows where the engine is most efficient
turbodan
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Re: Bone stock 528e with Megasquirt

Post by turbodan »

beaseac wrote: Nov 23, 2022 10:24 PM Awesome. Can you share your tune so I will have something to start with?

Thanks!
Adam
88 528e
Pm your email and I'll send it over.
turbodan
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Re: Bone stock 528e with Megasquirt

Post by turbodan »

Ju@n wrote: Nov 23, 2022 11:30 PM Seems like a good map, buttery smooth, and shows where the engine is most efficient
It's pretty good for a narrowband street tune over half a tank of fuel. Already runs better than motronic.

I am surprised by the character of the VE curve compared to the m20b25. Those are much flatter.
Ju@n
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Re: Bone stock 528e with Megasquirt

Post by Ju@n »

My stockish M30B34's fuel curve kind of looks the same, the only difference is I imagine the 528e has the rev limit lower than mine. The "torque bump" starts at around 3600rpm and ends at 4800.
RobertRO
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Re: Bone stock 528e with Megasquirt

Post by RobertRO »

beaseac wrote: Nov 23, 2022 7:38 PM I bought a k-data but haven't used it yet.
I wish you good luck with your K-Data unit.
Some 7 years ago I have purchased a Kdfi v1.4 PNP M30 ECU. It soon proved to be a very bad decision.
Mea culpa, at the time I was not aware that Kdfi is an illegal rip-off of Megasquirt. The unit I've got never worked properly. It randomly kept on losing the VR signal from the crankshaft sensor. However, the same VR sensor worked fine with both Motronic and Megasquirt). Customer support from K-Data: zero.
So I simply scrapped it, assuming a lost of 500+ Euro and a lot of time. I paid for my ignorance. Then I moved on to Megasquirt, and a couple of years later - you may laugh - back to Motronic. I actually enjoyed the Megasquirt project, and I learned a lot during the process. But I ended up concluding that it's hard to reach the superb tuning of a stock ECU.
beaseac
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Joined: Apr 25, 2021 3:32 PM
Location: South Carolina

Re: Bone stock 528e with Megasquirt

Post by beaseac »

turbodan wrote: Nov 23, 2022 11:55 PM
Ju@n wrote: Nov 23, 2022 11:30 PM Seems like a good map, buttery smooth, and shows where the engine is most efficient
It's pretty good for a narrowband street tune over half a tank of fuel. Already runs better than motronic.

I am surprised by the character of the VE curve compared to the m20b25. Those are much flatter.
Are you running everything from the Montronic just with the megaquirt? I've been holding off on installing mine until I found some details on whether or not I need to change anything for it to work. The only thing I found was I need to run a vacuum hose to the kdfi.

Have you noticed any performance improvements?

Thanks!
beaseac
Posts: 9
Joined: Apr 25, 2021 3:32 PM
Location: South Carolina

Re: Bone stock 528e with Megasquirt

Post by beaseac »

RobertRO wrote: Nov 24, 2022 9:18 AM
beaseac wrote: Nov 23, 2022 7:38 PM I bought a k-data but haven't used it yet.
I wish you good luck with your K-Data unit.
Some 7 years ago I have purchased a Kdfi v1.4 PNP M30 ECU. It soon proved to be a very bad decision.
Mea culpa, at the time I was not aware that Kdfi is an illegal rip-off of Megasquirt. The unit I've got never worked properly. It randomly kept on losing the VR signal from the crankshaft sensor. However, the same VR sensor worked fine with both Motronic and Megasquirt). Customer support from K-Data: zero.
So I simply scrapped it, assuming a lost of 500+ Euro and a lot of time. I paid for my ignorance. Then I moved on to Megasquirt, and a couple of years later - you may laugh - back to Motronic. I actually enjoyed the Megasquirt project, and I learned a lot during the process. But I ended up concluding that it's hard to reach the superb tuning of a stock ECU.
That doesn't sound good. I bought my unit about a year ago in hopes of someday adding a turbo. I've been looking for a kit for the E28 but it appears most are designed for the E30, which I'm sure could work on an E28... maybe.

I was looking at my Kdfi unit and saw that the cpu board is a plug in board... I wonder if an 'official' board will plug in? I figure I'll give it a try to see how it goes... now I will know what to be prepared for and turbodan is going to share his tune so I'll have a good baseline... did the kdfi recover or did it take some fiddling to get the signal back?

Thanks!
turbodan
Posts: 8777
Joined: Jan 09, 2007 10:19 PM

Re: Bone stock 528e with Megasquirt

Post by turbodan »

beaseac wrote: Nov 25, 2022 11:28 AM Are you running everything from the Montronic just with the megaquirt? I've been holding off on installing mine until I found some details on whether or not I need to change anything for it to work. The only thing I found was I need to run a vacuum hose to the kdfi.

Have you noticed any performance improvements?

Thanks!
The Motronic DME has been removed and the stock TPS has been replaced by a variable type. Everything else is stock. For starters the TPS is optional but it is beneficial to configure the overrun fuel cut and acceleration enrichments among other things. If your ECU is set up properly it should work with the stock VR sensor and possibly the stock ICV as well. Mine does run the ICV but this requires the correct hardware provisions on the Megasquirt board.

Performance is entirely up to you. On a non turbo motor you have the potential to pick up a small increase in power if your fueling and ignition timing is on point. It is also possible to cause engine damage with excessive ignition advance or a lean AFR. If you are not familiar with tuning you will very easily be lost like a golf ball in tall grass. Aspects like cranking pulsewidth are no fun at all, the car simply won't start if you're not close. Wideband oxygen sensor won't help at all until the engine is running. I'm still working on cold start settings, below 50 degrees it is not as effortless as it should be. Motronic will light right off at 10 degrees, you will not find a standalone unit that just does that. You have to dial it in.

The idle quality is vastly better, I can say that for certain. I suspect Motronic tries to maintin the idle at a relatively high manifold pressure by pulling the timing way back. Most likely better in terms of emissions if it's working properly. Not ideal as far as smoothness or fuel consumption. I'm idling around 30 kpa with Megasquirt and it is as smooth and consistent as we expect a BMW inline six to be. I do use a small pocket in the ignition table to help stabilize the idle but the minimum advance is 14 degrees and it doesn't approach that until it gets nice and warm.
beaseac
Posts: 9
Joined: Apr 25, 2021 3:32 PM
Location: South Carolina

Re: Bone stock 528e with Megasquirt

Post by beaseac »

Thanks for the information! Do you happen to have the part number for the throttle position sensor? I see there is already one on the throttle body, but I guess it's just for idle and full throttle?

I have a little experience with fuel management on the megasquirt but haven't delve into ignition mapping or anything so I know I have a lot to learn there.
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