MSX3 on a 998 Turbo. Cam Sensor, Fuel Injector and Throttle Body Advice.
Turbo Mini Forums

Hello.

I am in the process of building a 998 +100 with EFI and a turbo and have a few questions.

I am in the process of ordering the required parts for the MSX3 fuel injection. Diy Auto Tune seems to be the cheapest place. I am however struggling on how to convert the dizzy to a cam sensor. I have read the current feeds and sadly a lot of the pictures have gone so if anyone has any pictures of their own please help me out.

Equally injector size is an issue, i understand why you need a a large cc injector, due to fueling both draws on one quirt of fuel. I was thinking of a pair of 630cc at the inlet port. A second pair of 630cc injectors, fitted next to the first, and then staged later into the map. Again if you have knowledge please advise.

Finally i am looking at different throttle body options. I was looking at the MK2 MX5 throttle body as it has a built in idle motor across the butterfly. I know i will require a new TPS as i believe the original are just on/off switches, but hopefully the stepper motor will be compatible. does anyone know the diameter of the throttle butterfly on this body? Or does any one have any suggestions which have been previously sucessful? Advice needed please.

cheers

#Tried It 2

I'm running a stock MPI manifold, throttle body and injectors on a 998cc with around 7psi boost. I am also using an MS3x.

Four 630cc/min injectors will be good for up to 150hp. Staged on boost.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Awesome, one more thing off the list.

Paul previously you sent me a picture of your converted distributor, and i have a question. I understand that the rotating aluminium top has a square of a specific size which the sensor picks up on. Is the the iron part at the core part of the original distributor?
and how did you attach the aluminium cover securely?
do you have any websites that offer a guide to converting a dizzy?

cheers

#Tried It 2

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

The latest for reference:

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Sorry, by covered i was referring to the steel tube on your latest design.

So you hall effect sensor reads the steel and then the perfectly sized cut out gives the the signal that is required. As opposed to reading noting and then the steel tab giving a signal, in your older design?
do you have one or two cut outs.

So essentially you strip the dizzy down, retain the spindle and the body. Remove the top of the body from where the clamp retains the standard dizzy. place the spindle back in the dizzy and then weld the piece of steel tube to the spindle, I presume at the top. Then you attach a small oblong of aluminium, with a thread tapped for the sensor. and then use a grub screw to attach the block to the body.

I have spent a long time looking at the previous feeds trying to work out you design haha.

I hope you are not offended but i am essentially going to borrow your design, if you don't mind, for my own sensor as i love your compact design. I am going to attempt to us the DIY auto tune hall sensor for my own cam sensor. Do you have any experience with this sensor?

cheers

#Tried It 2

some pictures of my cam sensor attempt on my thread. no where near as sophisticated as the other ones on here, but it was cheap and got me on the road :)

http://www.turbominis.co.uk/forums/index.php?p=vt&tid=562154

Hey beejay (haha),

i have read your feed thoroughly before i posted. I am looking to make the smallest possible cam sensor that i can to give me as much room as possible. have you made any changes to your cam sensor since your posts?

thank you

#Tried It 2

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Here's mine. Not as compact as Paul's latest but very shallow, plenty of room for front mounted rad was my criteria. Uses a slotted opto sensor rather than hall.









Dizzy body machined down, circular (flat) aluminium disc glued in and additional screws from behind to secure. sensor on that.

If you use any form of dizzy body as a starting point, make sure it goes back in approx the same place rotationally as it would have been as a real dizzy. Although it appears the modified one could go at any rotation, if you look closely at one in bits you will see an oil drain/feed hole in the section that goes into the block that has to be in roughly the right alignment or the bearing bushes won't last long. You can see in my third photo I got it wrong at first hence the plugged hole for the wires.

Schrödinger's cat - so which one am I ???

If you are rebuilding the engine you may wish to consider picking up a signal on the cam sprocket:


This is how I've done 2 of my EFi engines. I've used the dizzy sensor on a budget build for my lad's car.

You need to use an alloy duplex and swap one of the stainless screws for a steel one. It works but oil sealing and temperature may be an issue.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

So for every complete cycle of four strokes of the engine there are 2 rotation of the cam sensor, this will then give 2 on/off signals per single engine rotation. If you were to make the cut out smaller than 180 would this effect the usability of the signal?

Surely you have to make sure that the cut out lines up with a stroke in the engine. If it was on the overlap between 2 strokes wouldn't this create issues with referring to the signal.

Thank you, that is why i try to make my explanation and hunt for detail a part of my post so it is easy for other to understand.

Is the cherry sensor the one that DIY Auto Tune sell?

I need as much room as possible for the intercooler as i would like to keep it all tucked under the bonnet.

Have you had any issues with the optical sensor? Is there any particular advantage to one over the other?

Thankyou for the tip about orientation, i will have a look at the dizzy i intend to use as the basis to make sure i have it all lined up.

#Tried It 2

Schrödinger's cat - so which one am I ???

It's one rotation of the cam for 4 strokes.

Have a look at the MS3 manual on cam sensor setup section 6.9.9.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

For a more detailed explanation, consider it like this,

No.1 cylinder at TDC starting the firing stroke, which is 1/2 revolution of crank by which time No.3 cylinder has reached TDC ready to fire then 1/2 revolution later, No.4 cylinder comes up to TDC to fire (while No.1 comes up on its exhaust stroke) and so on so a cycle is four half revolutions of the crank, or two complete revolutions.

And because a cyle is two crank revolutions the cam has to run at half the speed to open inlet and exhaust valves in the correct sequence for each cylinder over those two engine revolutions.

So the ECU just needs to know one point on the cam (usually a specified time before the No.1 TDC firing event, 120 degrees BTDC for a Megasquirt) to know which cylinder is about to fire (rather than be on any other of the three parts of the cycle).

And it's only for an ECU running any fully sequential mode (fuel or spark) that the cam position is needed at all. Cruder batch injection systems and/or wasted spark systems only need to know the crank position.

BTW, my choice of optical sensor was purely personal, I have used them a lot in the past for other things. For my wheel speed sensors I've used miniature Hall switches. No adavantage or disadvantage that comes to mind for use in a dizzy but the original aftermarket electronic ignition systems (ie, "Lumenition") used optical, all modern systems seem to use Hall.

EDIT - typo and para added.

Edited by Rod S on 20th Oct, 2016.

Schrödinger's cat - so which one am I ???

I saw the pictures before of the cam sprocket sensor. I really liked the idea, but i have a simplex set up with a stretched IWIS cam chain which i don't want to change and have to the issue of the chain stretching again and no one seems to do a reasonable priced alloy simplex setup. I know Kent did a few years ago but they don't seem to any more, and i think it is MED or swift tune who do one now but its very dear for what it is. If anyone has a Simplex they are willing to sell it would be brilliant if i could have it off you.

Thank you for the explanation so the cam sensors slot doesn't have to be a 180 slot, but does have to be on the inlet stroke of number 1.

Thank you for all of the help so far. Do you have any advice on throttle body selection, i liked the look of the MX5 throttle body due to the built in stepper motor. Do you have any advice on this?

cheers
#Tried It 2

Edited by Rod S on 24th Oct, 2016.

Schrödinger's cat - so which one am I ???