306 gti6 MAP sensor

[boldy205 75]

Hi All.

I'm having issues with the MAP sensor on my 205 with GTI6 with Lynx supercharger kit. 

After some googling, I found that I should have 1v at idle and 5v at WOT between pins 1 and 2.

I'm getting a reading of 5v in all situations, idle and WOT. I've changed the sensor and had the same readings. Any ideas?

 

Thanks

 

Matt

[Thijs_Rallye 87 4 Cars]

Sounds like your +5V ref is shorted to the signal wire somewhere in the loom.

[wicked 103 3 Cars]

Are you sure you are measuring pin 1 & 2 and not pin 2 & 3? 

[boldy205 75]

I've re tested today and had the following results; 

All on cold engine at idle:

 

Wire 1 green: 0.5v

Wire 2 white: 0.0v

Wire 3 orange: 2.5v

 

Values do jump around slightly, within a volt or so on all but wire No 2

 

There does seem to be quite a variety of results here. So I'm guessing some kind of wiring issues.

 

I'll look at tracing the 3 wires back to, I guess, the ECU?

[boldy205 75]

The above was +ive probe of multi meter on the wire, -ive probe to a good body earth.

 

Thanks!

[petert 586]

Maybe completely irrelevant and I've never really thought of it until now, but how does the standard MAP sensor cope with the boost range?

Edited August 27, 2022 by petert

[boldy205 75]

It's fitted before the SC, within a 2nd housing after the throttle butterfly. I assume the ECU then is programmed according.

It's crude, but has been working perfectly until now 

[petert 586]

The engine I just built for Parry uses a 2 Bar sensor, as it starts off in vacuum (<2500) then goes though to high boost, exceeding a range of 1 Bar.

[SRDT 175]

15 hours ago, boldy205 said:

I've re tested today and had the following results; 

All on cold engine at idle:

 

Wire 1 green: 0.5v

Wire 2 white: 0.0v

Wire 3 orange: 2.5v

On a 3 wire map sensor you have Ground, +5v and map signal so it seems that the orange wire is your signal here.

As for having 1v at idle it depends of the sensor range, all will be maxed at 5v so a 100 kpa, 150 kpa or 200 kpa can't have the same values.

[boldy205 75]

3 hours ago, SRDT said:

On a 3 wire map sensor you have Ground, +5v and map signal so it seems that the orange wire is your signal here.

As for having 1v at idle it depends of the sensor range, all will be maxed at 5v so a 100 kpa, 150 kpa or 200 kpa can't have the same values.

Agreed, the values seem all over the place.

I'm hoping for a dodgy connection somewhere on one of the wires.

Thanks for the clarification of the function on the 3 wires, will help when digging the loom out.

[boldy205 75]

3 hours ago, petert said:

The engine I just built for Parry uses a 2 Bar sensor, as it starts off in vacuum (<2500) then goes though to high boost, exceeding a range of 1 Bar.

That's the 'proper way' to do it, agreed. Just frustrating at my set up has worked, and very well, for quite a while now. Slightly crude, but still good!

[welshpug 1,657]

I believe  a work around was found after the kit was developed, but the main issue is that  the MM 1ap10 ecu is not designed  to see boost, so regardless  of fitting say a 3 bar sensor it doesnt know what to do beyond a certain point  that the original  sensor range is.

Edited August 28, 2022 by welshpug

[SRDT 175]

The IAW ap10 is used on the 405 T16 so aside for using another map sensor it should be more of a software problem. Now rewriting the code isn't like tweaking a few maps so it must be hard to find someone that can do that.

[boldy205 75]

18 hours ago, welshpug said:

I believe  a work around was found after the kit was developed, but the main issue is that  the MM 1ap10 ecu is not designed  to see boost, so regardless  of fitting say a 3 bar sensor it doesnt know what to do beyond a certain point  that the original  sensor range is.

This is why the standard sensor is used before the charger, so it never sees positive pressure. Then, I guess the ECU is programed to almost 'guess' where the fueling and spark needs to be? 

I believe some people have adjusted this set up and put the MAP sensor (and throttle body) after the charger, just before the inlet manifold. This would need stand alone ECU etc to work I assume.

Hopefully I'll get a few hours on it tomorrow night to dig these MAP sensor wires out and see if I can fin an issue. I might just bridge some fresh wires from ECU to sensor if I can't find much wrong.

[wicked 103 3 Cars]

The ECU has an external MAP sensor, so the statement that it is not designed to see boost is a bit weird. The ECU is designed to see an external MAP signal between 0-5V. So it depends on the MAP sensor you attach and if it can handle boost or not. 

If a MAP sensor is fitted with more range (like 250kPa MAP sensor iso the OEM 100kPa sensor), the signal will still be between 0-5V, but it has a different meaning.
 

100kPa (WOT) will be close to 5V with the original sensor but, maybe only 2V with 250kPA sensor, so without changing the software in the ECU, it will run very lean with that. 

[boldy205 75]

26 minutes ago, wicked said:

The ECU has an external MAP sensor, so the statement that it is not designed to see boost is a bit weird. The ECU is designed to see an external MAP signal between 0-5V. So it depends on the MAP sensor you attach and if it can handle boost or not. 

If a MAP sensor is fitted with more range (like 250kPa MAP sensor iso the OEM 100kPa sensor), the signal will still be between 0-5V, but it has a different meaning.
 

100kPa (WOT) will be close to 5V with the original sensor but, maybe only 2V with 250kPA sensor, so without changing the software in the ECU, it will run very lean with that. 

Hi Wicked. I see what you mean regards the ECU seeing boost, and using a different sensor, however this is an issue that has developed over time. The set up has worked well up until now. 

I've stripped back the ECU loom and chased back the MAP sensor wires. Will spend a bit more time tonight trying to find a loose/damaged wire hopefully.

I may well fit fresh wires from ECU to sensor to rule that out.

[wicked 103 3 Cars]

I was not trying to explain your issue; that likely is the wiring. It was more a general remark to clarify. Although I must say I think it is a weird solution to put the sensor before the charger, since MAP sensor is there to estimate the airflow going into the engine and that needs to be measured after the charger. How do you get the extra fuel injected that you need on boost?

[petert 586]

Parry's MAP sensor is in the normal position, near the throttle body, post supercharger. Even when it was running the oem sensor it was in that position. I had no experience of the previous setup. He purchased the bits from someone in Ireland. My job was to make it work with an aftermarket ecu.

[boldy205 75]

2 hours ago, wicked said:

I was not trying to explain your issue; that likely is the wiring. It was more a general remark to clarify. Although I must say I think it is a weird solution to put the sensor before the charger, since MAP sensor is there to estimate the airflow going into the engine and that needs to be measured after the charger. How do you get the extra fuel injected that you need on boost?

Fingers crossed it's something in the wiring to that I can sort easily. 

Regards the additional fuel needed on boost, I've no idea how that is calculated. The only way I can guess it's done is by RPM and throttle position, as these are the only other measurable parameters available to be the ECU if MAP is then redundant.

Saying that, maybe the MAP sensor just sees a greater drop in pressure (higher vac) as the boost is drawn into the engine. So possibly the ECU is programed for that?

[boldy205 75]

1 hour ago, petert said:

Parry's MAP sensor is in the normal position, near the throttle body, post supercharger. Even when it was running the oem sensor it was in that position. I had no experience of the previous setup. He purchased the bits from someone in Ireland. My job was to make it work with an aftermarket ecu.

Peter, is that a Lynx setup too?

[SRDT 175]

 

7 hours ago, boldy205 said:

Regards the additional fuel needed on boost, I've no idea how that is calculated. The only way I can guess it's done is by RPM and throttle position, as these are the only other measurable parameters available to be the ECU if MAP is then redundant.

Saying that, maybe the MAP sensor just sees a greater drop in pressure (higher vac) as the boost is drawn into the engine. So possibly the ECU is programed for that?

You need MAP + TPS (and obviously RPM) to calculate engine load.

You can get away with only RPM and TPS if you're not supercharged but in that case it's better to also have a lambda sensor.

[boldy205 75]

Well, I've started it up after messing with the ECU wiring and it didn't misfire at idle, which is a step forward. 

I'm thinking I'll bypass the ECU to MAP sensor wiring for the ground and +5v by giving it it's own supplies. This will then rule out and issues with those 2 wires.

Can anyone see an issue with doing this? 

[petert 586]

The MAP sensor was originally mounted on that adapter block between the throttle body and the manifold. The new GM 2 Bar sensor is now remote mounted but still taken off the manifold.

[wicked 103 3 Cars]

9 hours ago, boldy205 said:

Well, I've started it up after messing with the ECU wiring and it didn't misfire at idle, which is a step forward. 

I'm thinking I'll bypass the ECU to MAP sensor wiring for the ground and +5v by giving it it's own supplies. This will then rule out and issues with those 2 wires.

Can anyone see an issue with doing this? 

Yeah, don't! Just fix the wiring. The signal from the MAP means something relative to the ECU ground and +5V and external supply will have some offsets to those. You'll open the door for even more gremlins... 

 

And figure out if/what they did with the ECU to make it work...

It can be TPS-only on boost, but then they should have modified something. 

[petert 586]

Is TPS only a valid representation of load for a supercharged engine?