Turbo boost gauge

[c928jon]

Hi

Another question again...I keep reading to see if I can help answer as well, buy you guys seem pretty quick!

I've stripped all the dash out of my track car and replaced with a race-technology dash2 and datalogger. I found the specification for oil,temp, fuel and speed sensors but cant find anything for the boost gauge input.

I rigged up a temporary std gauge and all is fine, 0.75bar in std fettle but would like to configure the dash2 with the boost input.

Does anyone know what voltage is outputted from the klr/ecu for .5, 1 and 1.75 bar atm boost pressure? I havent got enough hands to drive at full boost, hold the temp gauge and get a multimeter accross the terminals!

 

[barks944]

The MAP sensor on the KLR is internal and is not accessable without getting inside the KLR. I believe the internal MAP sensor is 1 bar. Not sure what the internal output of the sensor is, suspect its measured by a wheatstone bridge as there laser trimmed resistors on its breakout board. Might generate a linear 0-5V output at the end of the day which you might be able to use.

 

[GPF]

It sends a voltage out from one of the pins on the KLR though doesn't it. Edit - it's pin 5 and it outputs a 0-5v. See here http://forums.rennlist.com/rennforums/944-turbo-and-turbo-s-forum/313463-klr-output-to-boost-gauge.html

 

[barks944]

I see the boost gauge is electrical! I always assumed it was mechanical for some reason. Edit: I always thought the MAP sensor in the KLR could only measure up to 2 Bara? The last post on that rennlist suggests the output of the sensor at >2 Bara was only about 2.5V doesnt it? If the overall output range is 0-5V does that suggest the sensor can measure up to 4Bara or 3 Barg? Unless the output is simlply capped at 2.5V and doesn't go any higher.

 

[robwright]

No electrical. Pin 5 of the KLR output is fed to pin 3 of the DME connector T1. I can only assume pin 4 is ground as is connected to pin 2 of knock diagnosis plug T21. Then pin 1 & 2 of plug A on the binnacle. You could in theory rig a device to this input to the binnacle to record these signals.

 

[barks944]

Pin 4 is ground I think. What is the binnacle? Edit: Ah you mean the test connector got you, pin 1 on that is 12V and pin 2 is DME relay switched GND (C50) I think. I don't think the MAP signal goes to the Test Connector. But I guess this chap has the cable that normally goes to the dash gauge anyway as he's ripped his dash appart.

 

[robwright]

Binnacle. Otherwise known as the instrument panle or cluster.

 

[barks944]

Lol, we'll at least we agree then was starring at the circuit diagrams scratching my head for a while there.

 

[robwright]

I did have to run ladedruck through the translator on google just to make sure I was looking at the right thing though [] I knew druck was pressure but was unsure what lade was. For those who haven't fallen asleep yet it translates to charge pressure.

 

[sawood12]

As Tom say's, the KLR MAP sensor can only read upto 2 bar absolute or 1 bar boost.

 

[robwright]

In that case how would a car deal with more than 15 psi of boost then? The MAP sensor is a piece of hardware on the KLR board IIRC and not integral to the chip, which would be changed for such a modified car. As the KLR not only provides output to the gauge it also provides boost pressure information to the DME for fueling calculations. Or am I egtting this wrong? Then surely it could not provide info to the DME for any more than 15 psi? I am not asking because I know. I am just kicking thoughts around my head [&:] Or does the DME make calculations based purely on air flow? Surely not????

 

[GPF]

The DME doesn't make it's calculations purely from airflow, but it doesn't use boost either. AFAIK, the map sensor in the KLR is not used in any of the DME's fueling/timing calcs. Part throttle values do use load on one axis of the map, but it comes from the TPS/AFM values. Also, the DME overboost protection completely ignores the map sensor - it uses AFM voltage.

 

[robwright]

Ah I see - well kind of lol. I wouldn't mind digging a bit further into this just for my own perverse satisfaction []

 

[c928jon]

wow I have the input to the dash(aftermarket) connected to the pin 5 of the klr, or pin 3 and 4 of the eight pin dme connector as per wiring diags. What I have to do now is teach the dash what voltages to expect for given manifold pressures. i.e -.5 bar atm = .5v, 1bat atm =1.5v and 2bar atm =4.0v. With three figures the dash setup software will produce an algorythm that is uploaded to the dash. Ok so it'll be best fit, but more accurate than my eyeballs bouncing up and down on full boost with silly track suspension!

 

[sawood12]

The KLR map sensor output is only used for overboost protection and has nothing to do whatsoever with the ecu, furling Or ignition. Upon detection on overboost the KLR will retard ignition before dumping exhaust manifold pressure via the cycling valve and wastegate. Aftermarket chips allowing more than 1 bar boost disable this safety feature to allow higher boost pressures however you are still protected against knock.

 

[barks944]

ORIGINAL: GPF The DME doesn't make it's calculations purely from airflow, but it doesn't use boost either. AFAIK, the map sensor in the KLR is not used in any of the DME's fueling/timing calcs. Part throttle values do use load on one axis of the map, but it comes from the TPS/AFM values. Also, the DME overboost protection completely ignores the map sensor - it uses AFM voltage.

The dme doesn't know map for sure. The turbo system was hacked onto motronic ml3.1 the more I understand it the less I like it. Doesn't know about knock or throttle position between closed and wide open throttle either. Will be fixing this with my new system ..

 

[robwright]

ORIGINAL: c928jon wow I have the input to the dash(aftermarket) connected to the pin 5 of the klr, or pin 3 and 4 of the eight pin dme connector as per wiring diags. What I have to do now is teach the dash what voltages to expect for given manifold pressures. i.e -.5 bar atm = .5v, 1bat atm =1.5v and 2bar atm =4.0v. With three figures the dash setup software will produce an algorythm that is uploaded to the dash. Ok so it'll be best fit, but more accurate than my eyeballs bouncing up and down on full boost with silly track suspension!

OK this much I do know as concerns overboost and hence the reason my cycling valve was junked long since. So my suspicions about off the shelf aftermarket chips being pure guess work are correct then? OK well not total guesswork they must be based on models but how can I put are pretty generic maps. So a custom map based on your own dyno figures is the best way to go then. Question is how much does one of those cost? And who does it? Surely they would have to know 944s specificly and know what they were looking at. And if you are not planning on modding your car to the possible max in one hit then a trip to said dyno would be necessary after every mod. Also are the aftermarkets usually EPROMS and can therefore be reprogrammed hence negating the need to buy more chips each time. Sorry to hijack your thread fella []

 

[sawood12]

Upon detection of knock or overboost the KLR will send a signal to the DME to start retarding ignition upto a max of 6 degrees, if that still doesn't arrest the problem then the cycling valve is commanded by the KLR to dump exhaust manifold pressure. So the DME doesn't know boost pressure - it simply receives a signal from the KLR which tells it to start pulling back ignition. My understanding from various threads on this subject is at partial throttle the DME only uses AFM and doesn't map against boost pressure - ignition timing is achieved via assumed boost pressures derived from other sensors such as AFM, TPS. At 3/4 to WOT the DME just commands fuel flow against RPM and at WOT it just commands as much fuel as the system can deliver (if you've ever been behind a turbo on song you get a very rich smell of unburned fuel and nice flames out of the back once you lift off throttle). No point in knock protection or closed loop AFR at those conditions because if you things go wrong things happen so quickly the system can't react quickly enough to save the engine, so the idea is to never let the thing get into those conditions in the first place by throwing as much fuel in the system as possible.

 

[GPF]

ORIGINAL: sawood12 The KLR map sensor output is only used for overboost protection and has nothing to do whatsoever with the ecu, furling Or ignition. Upon detection on overboost the KLR will retard ignition before dumping exhaust manifold pressure via the cycling valve and wastegate. Aftermarket chips allowing more than 1 bar boost disable this safety feature to allow higher boost pressures however you are still protected against knock.

Sort of but not quite. The KLR map sensor is used to regulate boost via the CV which controls the wastegate. It does not have anything to do with overboost protection though - that is handled purely by the DME monitoring airflow via the AFM voltages. The KLR controls knock protection by retarding ignition by 3 degrees at first and then 6 degrees as you describe. It also triggers the "limp mode". It is the DME overboost protection via the airflow voltage that aftermarket chips raise or disable. If you have bypassed the CV, you can disconnect the vac line to the KLR (and plug it) and the only thing that will change is that the dash boost guage won't work...... Edit - actually, that's not 100% correct either![8|] The "limp mode" won't by triggered - but then if there's no CV it can't be anyway.....

 

[barks944]

Seems like theres a lot of differenent understanding of these systems. I can tell you the following things I am very sure are true. I know this as I have been reverse engineering the circuits to do my project. The ignition signal from the DME is sent to the KLR which sends back a signal which directly fires the coil circuitry in the power board of the DME with no input to the microprocessor on the DME. The DME does not know if knock has occured. The DME does not know boost pressure. It derives load from the AFM signal and assumes full load when it sees a full load signal which is generated by the KLR. My Assumptions: I believe, although without certainty that the KLR manages overboost protection. This is why you must chip the KLR even if a manual boost controller is used. Otherwise it will retard ignition or w/e. I think knock protection is simply triggering limp mode, the KLR does not manage knock or adapt ignition to prevent it, it just protects the engine if it detects a certain frequency of knock. Edit: As part of my work on this engine management system I am compiling somthing of a disection of the 944/951's management system. Would appreciate a people reading what I write and giving some feedback in order to create a good shared understanding of the system. Any takers?