map sensor cheating?

[fdsjakl890]

hey hey

im new here and came to seek advice from the wise elders

i recently put silvertop itbs on my map bigport and i was wondering if theres a way to cheat the map sensor to output a better signal because the vacuum is not nearly as strong as with the stock manifold. runs perfect on full throttle but anything below is just really rich so i cant really cruise at all not the end of the world really, wouldnt mind otherwise but it sips A LOT of fuel, reeks of gasoline and i think the plugs are already going bad..

one idea i had was putting a vacuum pump to kind of emulate a normal manifold and a valve that opens/closes with the engines vacuum that controls the pressure but it seems pretty complicated

second option is making some electronics to convert the current signal range back to 0-5v but i dont know if thats any easier. im not good with electronics stuff but i guess i need some kind of amplifier?

or

can i plug in an o2 sensor in the stock ecu since mine doesnt have one? i was looking at the jdm ecu pinout schematic stuff and it looked like there was a spot for an o2 sensor. if i get an o2 sensor and plug it there would that give the ecu more information to work with or does that pin even go anywhere in a map ecu?
i do have a wideband lambda installed for a mixture gauge since i wanted to see how it runs with the itbs incase its lean but i guess i couldnt use that for the ecu?

"why not aftermarket ecu?"
im going to at somepoint but i feel like thats going to take a while to set up and tune. its my daily and i need it right now. all the wiring is pretty bad so im going to redo all of it when im swapping the ecu but right now i cant really take it apart. also im poor goblin

so if theres any bandaid fixes you people know of or if i have missed something really obvious let me know

[decryphe]

If you want to keep running the stock ECU, a piggyback that converts the sensor signal according to some custom map would be the way to go. If you're into electronics, you could try doing this with some form of Arduino or other small microcontroller. Personally, I'd go for anything that can run Rust, as I don't like C on embedded, such as https://www.waveshare.com/rp2040-zero.htm and either breadboard or design a little PCB to do the voltage conversions and some voltage spike protection on all pins.

If that's not an option, you'll have to jump to an aftermarket ECU now.

I could imagine there's also some form of analog circuitry that you could use to adjust the sensor output signal, maybe some form of pull-up resistor could help, depending on the polarity of the signal. I'd have to oscilloscope that sensor to know.

But to me, it's quite interesting that it could be quite simple to slap ITBs on mine without swapping the ECU... I'm surprised it runs at all. What does the setup look like?

[banpei]

The issue is that the vacuum on the MAP system is very different from the vacuum on ITBs. For the MAP system, there is a single sensor, as it's a single throttle body. By T-ing the four vacuum lines on the manifold, you will get a very different vacuum than on the single throttle body. This is apparent in both low-end and top-end. Usually, this isn't a huge issue to remap with an aftermarket ECU, but on a stock ECU this is a problem. Some people (like Robokill) use a stock ECU with a different map (e.g. using a custom EPROM), but this is not something you can obtain freely.

About the 02 sensor: some European ECUs did get a cat, so they also have an O2 sensor. However, if your ECU doesn't have a cat, it will not do anything with the O2 signal.

Edit: You could try to go for a Speeduino (which is not a piggyback), but keep in mind that you would have to create your own tune that matches your ITB setup. Even if there is a 4AGE map available for the Speeduino, it probably would be different from your setup, as it could differ in manifold or ITBs used. Most of the cost for aftermarket ECUs isn't in the ECU itself, but in creating the right map.

[fdsjakl890]

(08-18-2025 05:49 PM)decryphe Wrote:  If you want to keep running the stock ECU, a piggyback that converts the sensor signal according to some custom map would be the way to go. If you're into electronics, you could try doing this with some form of Arduino or other small microcontroller. Personally, I'd go for anything that can run Rust, as I don't like C on embedded, such as https://www.waveshare.com/rp2040-zero.htm and either breadboard or design a little PCB to do the voltage conversions and some voltage spike protection on all pins.

If that's not an option, you'll have to jump to an aftermarket ECU now.

I could imagine there's also some form of analog circuitry that you could use to adjust the sensor output signal, maybe some form of pull-up resistor could help, depending on the polarity of the signal. I'd have to oscilloscope that sensor to know.

But to me, it's quite interesting that it could be quite simple to slap ITBs on mine without swapping the ECU... I'm surprised it runs at all. What does the setup look like?

i was thinking of a microcontroller but i would have to learn how to code and do electronics stuff. im kind of spooked of all the electronic stuff because i really dont want to fry my ecu or anything if i mess up.

i did some research how i could do it all analog. lets say my signal is 3-5v. i would need a 3v reference to substract my current idle signal voltage and then amplify the signal voltage x2(?) so the output would be 0-5v with the same vacuum range. and voltage regulator so it doesnt go above 5v. and it could be made adjustable with potentiometers for simple tuning. atleast thats how i think it would work... im not an electrician but if its just soldering components i think this is something i could manage.. just dont know how

my itbs are just slapped on with an adapter i got on ebay. i just had to shorten the water outlet a bit since it was hitting the tps and had to leave the tvis plate on because the adapter was wayy too short. i did take the tvis valves off.

but it really does run great at full throttle

---

(08-18-2025 05:53 PM)banpei Wrote:  The issue is that the vacuum on the MAP system is very different from the vacuum on ITBs. For the MAP system, there is a single sensor, as it's a single throttle body. By T-ing the four vacuum lines on the manifold, you will get a very different vacuum than on the single throttle body. This is apparent in both low-end and top-end. Usually, this isn't a huge issue to remap with an aftermarket ECU, but on a stock ECU this is a problem. Some people (like Robokill) use a stock ECU with a different map (e.g. using a custom EPROM), but this is not something you can obtain freely.

About the 02 sensor: some European ECUs did get a cat, so they also have an O2 sensor. However, if your ECU doesn't have a cat, it will not do anything with the O2 signal.

Edit: You could try to go for a Speeduino (which is not a piggyback), but keep in mind that you would have to create your own tune that matches your ITB setup. Even if there is a 4AGE map available for the Speeduino, it probably would be different from your setup, as it could differ in manifold or ITBs used. Most of the cost for aftermarket ECUs isn't in the ECU itself, but in creating the right map.

yeah the vacuum is wayy different. i have the vacuum connections t-d together right now but maybe i should try what kind of effect adding a vacuum block or some kind of vacuum canister would have. or maybe bigger vacuum inlets?? would be way easier if there was a 0-5v map sensor with adjustable tension to adjust for the lower vacuum but i dont think those exist

i thought the o2 sensor goes in the manifold so cat doesnt effect it? but i guess that doesnt matter if the map ecu doesnt have the internals for the o2 sensor.

im sure theres a lazy and cheap way to fix it
or ill just have to swap the ecu and bike around until its done

[Ivan141]

I doubt there is a cheap and easy way to fix it.
That being said, I have a hobby project that is basically a PCB with 4 individual MAP sensors on it, that would then be connected to each runner individually.
The thing with ITB's is that only 1 cylinder at a time is creating a decent vacuum signal, if you T them into a small vacuum manifold you are basically dampening the signal out and it will still not resemble a proper plenum. The idea with the 4 sensors is to pass along the strongest signal at any time, which should result in a much more robust signal.

Anyhow, I've put my first prototype together and as is the tradition it has been a massive pain in the ass. Put on any single sensor and it works fine, put 2 or 3 and it works fine. Put on 4 and 1 sensor starts tripping balls. Have put it away for the summer as finding the cause of these issues can be frustrating.
If I can iron out the issue, you could in theory make it output any kind of signal you want as long as its between 0 and 5 volts as I have a microcontroller on the board.

[decryphe]

(08-20-2025 05:48 PM)Ivan141 Wrote:  I doubt there is a cheap and easy way to fix it.
That being said, I have a hobby project that is basically a PCB with 4 individual MAP sensors on it, that would then be connected to each runner individually.
The thing with ITB's is that only 1 cylinder at a time is creating a decent vacuum signal, if you T them into a small vacuum manifold you are basically dampening the signal out and it will still not resemble a proper plenum. The idea with the 4 sensors is to pass along the strongest signal at any time, which should result in a much more robust signal.

Anyhow, I've put my first prototype together and as is the tradition it has been a massive pain in the ass. Put on any single sensor and it works fine, put 2 or 3 and it works fine. Put on 4 and 1 sensor starts tripping balls. Have put it away for the summer as finding the cause of these issues can be frustrating.
If I can iron out the issue, you could in theory make it output any kind of signal you want as long as its between 0 and 5 volts as I have a microcontroller on the board.

That's also an interesting option. My first actual engine building experience will now either be the KE10 engine or an ITB+EFI conversion of a '71 Beetle 1302. There's some pretty cool EFI swaps for that engine, and getting the reliability and fuel economy of an EFI setup in the Beetle would be amazing. Building something that can deal with 4 or 6 cyl ITB setups would be great, as my dream build is to put ITBs on a 2JZ-GE.

Do you have any of the project info on Github or something? I'd like to have a look, actually.

[Ivan141]

Nothing online at the moment, but I copied the original idea from a dude on the grassroots motorsports forum (look for frankenferrari, the board he uses is called multimap).
The only thing I changed is add a microcontroller so I have more signal modifying options (it can also work with just diodes and an opamp), and I used way more compact and cheaper MAP sensors that still have a decent range (surface mounted).
It should end up more compact and affordable.

[decryphe]

(08-22-2025 04:01 PM)Ivan141 Wrote:  Nothing online at the moment, but I copied the original idea from a dude on the grassroots motorsports forum (look for frankenferrari, the board he uses is called multimap).
The only thing I changed is add a microcontroller so I have more signal modifying options (it can also work with just diodes and an opamp), and I used way more compact and cheaper MAP sensors that still have a decent range (surface mounted).
It should end up more compact and affordable.

This must be the older project: https://github.com/jharvey/MultiMAP

What kind of MCU are you using? Is it worth using something like the https://learn.adafruit.com/adafruit-rp20...r/overview to get CAN output as well? (Also, bonus points for being able to target it using Rust...)

[Ivan141]

Some specs:
MAP sensors: KP226E0109 (or similar, the part numbers change every year but they usually have something compatible with the same footprint).
MCU: AVR128DB28 (basically a decent Arduino compatible microcontroller).
PCB has a provision for generic MCP2515 CAN controller boards from AliExpress.