Hi
I have been following the discussions about MAP or TPS sensing of load and to summarise my understanding it seems that MAP is preferred (more accurate), except where lumpy cams are used as the signal will fluctuate as it is only sensing one port.
I assume from this that is for carbed cars and injected cars with individual throttle bodies. If I use a single (big) throttle and plenum chamber and then multiple injectors further downstream, I think that I can use a MAP sensor mounted into the plenum chamber and a lumpy cam - is this right or have I missed something along the way?
On the subject of knock sensors I understand what they do, but what are they and where do I need to fit it/them on the engine?
Sorry for the dumb questions but we all have to learn.
Chris
MAP Positioning / Knock Sensors - Newbie
Moderators: JeffC, rdoherty, stieg, brentp
Correct on the map
Correct on the map sensing
Knock sensing is a piezo that creates a signal when pre detonation
is taking place, the sensor is mounted on the side of the engine block
not the cilinderhead!
Ivan
Knock sensing is a piezo that creates a signal when pre detonation
is taking place, the sensor is mounted on the side of the engine block
not the cilinderhead!
Ivan
There's no dumb questions,
There's no dumb questions, only dumb answers...and this could be one..
<i>I think that I can use a MAP sensor mounted into the plenum chamber and a lumpy cam - is this right or have I missed something along the way?</i> Yes, that's generally right. Depends on how lumpy the cam is I suppose. What engine/car are you considering?
Knock....
From
http://en.wikipedia.org/wiki/Engine_knock
A knock sensor consists of a small piezoelectric microphone, on the engine block, connected to the engine's ECU. Spectral analysis is used to detect the trademark frequency produced by detonation at various RPM. When detonation is detected the ignition timing is retarded, reducing the knocking and protecting the engine.
Wholly irrelevant to MJLJ in its current form as the MJLJ has no knock sensing capability (ie spectral analysis) or the ability to take in a simple signal that says that knock is occurring.
<i>I think that I can use a MAP sensor mounted into the plenum chamber and a lumpy cam - is this right or have I missed something along the way?</i> Yes, that's generally right. Depends on how lumpy the cam is I suppose. What engine/car are you considering?
Knock....
From
http://en.wikipedia.org/wiki/Engine_knock
A knock sensor consists of a small piezoelectric microphone, on the engine block, connected to the engine's ECU. Spectral analysis is used to detect the trademark frequency produced by detonation at various RPM. When detonation is detected the ignition timing is retarded, reducing the knocking and protecting the engine.
Wholly irrelevant to MJLJ in its current form as the MJLJ has no knock sensing capability (ie spectral analysis) or the ability to take in a simple signal that says that knock is occurring.
MAP Positioning
Thanks guys, glad to know I'm on the right track and that the knock sensor isn't required.
Further question - If I use twin carbs with a manifold that has a balance tube (like an MGB etc.); could I get a smoother MAP reading even if using a lumpy cam (Piper 285)?
Chris
Further question - If I use twin carbs with a manifold that has a balance tube (like an MGB etc.); could I get a smoother MAP reading even if using a lumpy cam (Piper 285)?
Chris
Twin carbs usually use a
Twin carbs usually use a Throttle Position Sensor, so maybe there's a lesson to be learnt from that. That doesn't mean that MAP won't work, but TPS might be better.
Costs are probably about the same (the MJLJ MAP sensor vs. a 'proper' TPS), although I've seen a homemade TPS made from a 50p potentiometer and a 35mm film can that works well
With twin carbs, I'd go for TPS. Here's a nice TPS install
http://www.cate1.co.uk/megajolt/installation.php
In simple terms, they're both just a way to measure the 'requested' power (or torque?) demand, both initiated largely by the throttle - TPS measures the throttle demand exactly, MAP does it by measuring the resulting vacuum in the manifold.
Costs are probably about the same (the MJLJ MAP sensor vs. a 'proper' TPS), although I've seen a homemade TPS made from a 50p potentiometer and a 35mm film can that works well
With twin carbs, I'd go for TPS. Here's a nice TPS install
http://www.cate1.co.uk/megajolt/installation.php
In simple terms, they're both just a way to measure the 'requested' power (or torque?) demand, both initiated largely by the throttle - TPS measures the throttle demand exactly, MAP does it by measuring the resulting vacuum in the manifold.