Supercharger ECU tuning
Discussion
Hi all,
During 1st lockdown for something to do I fitted an Eaton M45 supercharger to a 2.0 Twinspark Alfa for a bit of fun. The car is pretty worthless so I was never worried about destroying the engine, it was more of a learning experience for me as I've never done anything involving forced induction.
I'm not sure of how much boost it makes because the gauge is analogue 0-30psi & it barely lifts off 0. I'm using a blow off valve that recirculates the air back into the intake when throttle is shut. It does run surprisingly well & all my concerns about it running lean appear to be false but I'm just after some confirmation of my knowledge after some logging I've done. At wide open throttle to 6250rpm the MAF signal is 4.47v. I suspect at 7200rpm the MAF may be at the limit but I'm going to assume it's ok for the time being before confusing me more with scaling a new one etc.
The Lambda sensor was constantly switching from low to hi signal throughout normal driving conditions but on the same WOT run it was 0.925v throughout the pull (running rich?) but I'm wondering why? Shouldn't the ECU to trimming the fuel off?
I'm wondering where to go from here. I'm thinking of installing a wideband Lambda with Air/fuel gauge next. The ECU is a write only & looks a nightmare to do anything to, I'm wondering if it's best to wire in a piggy back ECU with a built in MAP sensor.
I hope this makes some kind of sense. I understand I've not addressed spark advance etc. But want to fully understand the fuel side first.
During 1st lockdown for something to do I fitted an Eaton M45 supercharger to a 2.0 Twinspark Alfa for a bit of fun. The car is pretty worthless so I was never worried about destroying the engine, it was more of a learning experience for me as I've never done anything involving forced induction.
I'm not sure of how much boost it makes because the gauge is analogue 0-30psi & it barely lifts off 0. I'm using a blow off valve that recirculates the air back into the intake when throttle is shut. It does run surprisingly well & all my concerns about it running lean appear to be false but I'm just after some confirmation of my knowledge after some logging I've done. At wide open throttle to 6250rpm the MAF signal is 4.47v. I suspect at 7200rpm the MAF may be at the limit but I'm going to assume it's ok for the time being before confusing me more with scaling a new one etc.
The Lambda sensor was constantly switching from low to hi signal throughout normal driving conditions but on the same WOT run it was 0.925v throughout the pull (running rich?) but I'm wondering why? Shouldn't the ECU to trimming the fuel off?
I'm wondering where to go from here. I'm thinking of installing a wideband Lambda with Air/fuel gauge next. The ECU is a write only & looks a nightmare to do anything to, I'm wondering if it's best to wire in a piggy back ECU with a built in MAP sensor.
I hope this makes some kind of sense. I understand I've not addressed spark advance etc. But want to fully understand the fuel side first.
One would think before even getting to this stage you'd have done some research into how things work which would have answered the questions in order to prevent damage to the engine.
Get some books on the subject. Paper resources whilst may be less common these days, are worthwhile having to learn from.
1. You have probably plumbed the gauge in wrong...it needs to be plumbed into the intake manifold between the blower and intake valves.
If it is there already....then maybe you are making no boost....or it isn't attached to the gauge lol. An d ideally you'd have a gauge that reads vac/boost.
2. If your MAF signal is already topping 4.47v...IMO, it's maxed out, probably not so safe. Some sensors may go right to 5v...many do not and mid 4's is them flat out.
3. To an amateur, a narrowband reading is pretty useless and could be considered dangerous to infer anything from it..
Low loads closed loop, if things are working as normal, then yes the voltage should oscillate either side of stioch.
At higher loads when open loop, of course it will not
"Rich" on a narrowband simple means richer than stioch....it is not an acceptable form of determining mixture for high load tuning. Although with that high voltage....in theory it should at least be relatively safe.
And no, there is no reason the ecu should be "trimming fuel off".
4. Yes, a wideband is pretty much essential to determine fuel mixtures. They're so cheap these days, little reason not to have one.
And beyond that, some means of controlling both fuel and ignition timing so you don't blow the engine up. And a competent person doing the tuning....again, so you don't end up with a blown engine.
As to how you achieve any tuning changes....is another matter. Piggybacks are a little less common these days. Plenty of options for a full standalone ecu, but that also carries a price tag and perhaps more complication than you might need.
Or there are a myriad of DIY/bodge type methods of fooling things to achieve some sort of control over tuning over the years.
But without a full understanding of how your system works....those will be out of reach.
And without knowing what mixtures are like currently, or how things are with ignition timing etc....you're treading dangerous ground. Unless boost is actually zero...then it should be safe lol.
Of course then that needs resolved.
Get some books on the subject. Paper resources whilst may be less common these days, are worthwhile having to learn from.
1. You have probably plumbed the gauge in wrong...it needs to be plumbed into the intake manifold between the blower and intake valves.
If it is there already....then maybe you are making no boost....or it isn't attached to the gauge lol. An d ideally you'd have a gauge that reads vac/boost.
2. If your MAF signal is already topping 4.47v...IMO, it's maxed out, probably not so safe. Some sensors may go right to 5v...many do not and mid 4's is them flat out.
3. To an amateur, a narrowband reading is pretty useless and could be considered dangerous to infer anything from it..
Low loads closed loop, if things are working as normal, then yes the voltage should oscillate either side of stioch.
At higher loads when open loop, of course it will not
"Rich" on a narrowband simple means richer than stioch....it is not an acceptable form of determining mixture for high load tuning. Although with that high voltage....in theory it should at least be relatively safe.
And no, there is no reason the ecu should be "trimming fuel off".
4. Yes, a wideband is pretty much essential to determine fuel mixtures. They're so cheap these days, little reason not to have one.
And beyond that, some means of controlling both fuel and ignition timing so you don't blow the engine up. And a competent person doing the tuning....again, so you don't end up with a blown engine.
As to how you achieve any tuning changes....is another matter. Piggybacks are a little less common these days. Plenty of options for a full standalone ecu, but that also carries a price tag and perhaps more complication than you might need.
Or there are a myriad of DIY/bodge type methods of fooling things to achieve some sort of control over tuning over the years.
But without a full understanding of how your system works....those will be out of reach.
And without knowing what mixtures are like currently, or how things are with ignition timing etc....you're treading dangerous ground. Unless boost is actually zero...then it should be safe lol.
Of course then that needs resolved.
Thanks for the reply. Please don't think I haven't done any research because I said I wasn't bothered about destroying the engine. I knew from the beginning the ECU would be a problem to address later down the line but I've took everything one step at a time.
The gauge is a vac/boost one plumbed into the inlet manifold. I knew the setup wouldn't make more than 5psi which is apparently what the engine can handle without any modifications. There's definitely boost because you can hear it blow off. Maybe I'll switch to a digital one.
I appreciate the knowledge on the MAF voltage & narrow band lambda. I will install an AFR gauge then take it from there.
The gauge is a vac/boost one plumbed into the inlet manifold. I knew the setup wouldn't make more than 5psi which is apparently what the engine can handle without any modifications. There's definitely boost because you can hear it blow off. Maybe I'll switch to a digital one.
I appreciate the knowledge on the MAF voltage & narrow band lambda. I will install an AFR gauge then take it from there.
acealfa said:
Thanks for the reply. Please don't think I haven't done any research because I said I wasn't bothered about destroying the engine. I knew from the beginning the ECU would be a problem to address later down the line but I've took everything one step at a time.
The gauge is a vac/boost one plumbed into the inlet manifold. I knew the setup wouldn't make more than 5psi which is apparently what the engine can handle without any modifications. There's definitely boost because you can hear it blow off. Maybe I'll switch to a digital one.
I appreciate the knowledge on the MAF voltage & narrow band lambda. I will install an AFR gauge then take it from there.
So is the gauge reading vacuum ok ?The gauge is a vac/boost one plumbed into the inlet manifold. I knew the setup wouldn't make more than 5psi which is apparently what the engine can handle without any modifications. There's definitely boost because you can hear it blow off. Maybe I'll switch to a digital one.
I appreciate the knowledge on the MAF voltage & narrow band lambda. I will install an AFR gauge then take it from there.
If it is and you dont have some sort of check valve in front of it....then maybe you are making no boost.
I haven't read the book, but Julian Edgar always writes well, explains well, and covers a lot of basic stuff to learn from.
https://www.amazon.co.uk/Modifying-Electronics-Mod...
I have this one, although it was more basic than I expected, but for a learner it would be good. Although from a modifying point of view...the first one may suit better
https://www.amazon.co.uk/Electrical-Electronic-Sys...
A lot of his stuff was featured here many years ago if you can search the various tech articles. Although the website has not really been active for quit a number of years so the site isn't as functional as it once was.
https://www.autospeed.com.au/index.html
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