Jobro

iTrader: (2)

Ok I now understand I can use ignition only, to debug car and then attempt fuel later.

I'm currently sourcing a S5 Turbo CAS. I understand it has 2 sets of teeth, a 24 tooth wheel and a 2 tooth wheel.

I understand that If I use the base v3.0 PCB it has one VR sensor conditioner. People mention all the time removing teeth from the CAS trigger so they do not have to build another VR sensor conditioner. Could someone explain to me, the logic involved in this. I don't understand how a sensor conditioner is interfaced into the CAS output.

Is it dodgey or sub-ideal to remove teeth instead of installing additional VR filter/conditioners. How difficult is the additional VR sensor conditioner.

I want my ignition systems to have.

*A wasted spark setup used for the leading plugs. ALA DLIDFIS (which I use atm)
*1 Coil/plug for the trailing ignition
* Correctly set leading/trailing split
*MAP/rpm based ignition

I currently have 3 Bosch BIM024 ignitors, and 3 coils which work fine being driven from the factory Electronic Distributor.

I did make provisions in my brackets for additional coils (4 coils and 4 ignitors to be exact), so this is no problem at all.

How is the system setup when I want this functionality, and how does it work. I read somewhere if you want coil / plug you need to use a 36-1 wheel and some EDIS system.

Can someone explain the theory to me so I can understand what I NEED and what is optional. I understand the V921 circuits or whatever aren't needed because I have ignitors already provided.

My engine is a 12A extend port (you guys would call this a street port). It has ported exhaust aswell, brandnew housings (still less than 400miles on them) windowed rear stat gear and bearing.

muythaibxr

you do not need EDIS or a 36-1 wheel...

For your CAS questions:

It doesn't matter if you cut teeth out of the CAS or build another VR sensor conditioner as far as the car running is concerned... most of the people who cut teeth do so because they don't want to build the extra conditioner.

The CAS has 2 wires per VR sensor, one + and one -, so all you do is wire the + wire on the 24 tooth wheel to the tach pin on the MS, and turn the two potentiometers on the inside of the board all the way counterclockwise. The - wire should be wired straight to ground.

For the 2 tooth wheel, you have to build another conditioner, and wire the + wire to the correct place on the lm1815 circuit, and the - wire to ground.

All you *need* is:
1) CAS (If you cut two teeth out, you only need the built-in VR sensor conditioner on the v3 board)
2) an ignitor and wasted-spark coil (preferably an S4 or S5 leading ignitor with coil). This is for leading
3) either a 2nd gen (s4 or s5) trailing ignitor with coils, or 2 coils and 2 ignitors. You can do split either way. With the 2nd gen ignitor, you need to select "FC trailing" in split options, with 2 separate ignitors, you can select FD trailing.
4) for either ignition option, you need to add 4.7k pullup resistors as detailed in the FAQ.

You will not be able to run 4 coils and 4 ignitors with the current code unless you run the leading ones as if they were wasted spark.

Jobro

iTrader: (2)

THANKS!!!

Ok if i cut 2 teeth out of the 24 tooth wheel, i cut the ones that line up with the 2 tooth wheel? Do I then just use the outputs from the 24 tooth wheel because it has the information of the 2 tooth wheel on it in the form of missing teeth? Is that the correct understanding.

I WILL be running the leading ignition in a wasted spark setup. I think that is the best bet.

I understand the 4.7k trick for the -ve coil wire.

papiogxl

iTrader: (6)

You can cut any two opposing teeth on the wheel. Having these cut negates the need for a second wheel because the computer knows when to reset its timing by seeing the longer gap in teeth than usual, instead of seeing a tooth on the other circuit.

renns

In theory any two teeth can be cut, but you may end up with a CAS that can't be properly adjusted due to the limited range of motion of the CAS housing against that adjustment screw. Terrh said he had that problem, where proper adjustment was just beyond full rotation in one direction. Re-stabbing the CAS one tooth off to compensate resulted in being just beyond full rotation in the other direction. Rotate the engine to 60 degrees BTDC, with the CAS rotated to the middle of its adjustment range, and then choose the tooth that's aligned with the VR sensor, and it's mate opposite. That should give you proper adjustment in both directions for fine-tuning.

muythaibxr

Wait, you don't want to cut the tooth that's lined up, you want to cut the tooth before it. The reason being that the tooth that's lined up at 60 deg btdc is going to be the trigger tooth.

What I've always done for this is position the engine at the -5 mark (there's no easy way to tell where 60 btdc is) and look at the tooth that is lined up with the sensor. This tooth is going to be tooth #3, and is going to be at 0 deg when all is said and done. now count back two teeth... the tooth you're on is tooth 1, and is at 60 deg btdc roughly. Count back 1 more tooth... this is the one to cut, at 90 deg btdc. Now find the tooth opposite it, and cut that one too, and you're done.

renns

True enough. Be sure to move the CAS to midposition, first though. If the CAS is swung over full one way or the other, a set of teeth may be cut that results in never being able to set the timing properly, even with re-stabbing.

As for the 60 deg mark on the pulley, doesn't everyone have their's remarked in 10 deg increments to verify advance? It's really easy to, thanks to an idea Paul Yaw posted to his site years ago. The pulley diameter is about 115 mm, resulting in a circumference almost exactly 360mm. In other words, each degree is 1mm when measured as an arc length around the rim. A piece of cloth tape, mark paper, or whatever can be used to transfer timing marks to the rim. File a shallow groove with a file at each mark, and add a drop of paint to make it visible to the timing light.

muythaibxr

I don't think everyone has done that to the pulley. I sure haven't.... have not found it necessary.

Jeff20B

iTrader: (13)

Actually, that's an idea I came up with. Paul was all into inches and masking tape, which can stretch and ruin your careful measurements. I suggested using a clotch metric tape measure.

For mine, I added a mark every 120° on the pulley with extra dabs of paint on the middle high part of the pulley to show which rotor was firing. I cut the teeth from the reluctor that seemed correct at the time.

Just a couple days ago while test running the 20B, I hooked up a timing light and the pulley marks are dead even at -5° when the CAS housing is aligned so the clean spot from the original positioning is directly under the nut. I guess I go it right.

Jobro

iTrader: (2)

I am having problems understanding the uses of the "Throttle Position Sensor"

1.) What functionality do we loose if we just use the the map sensor on the megasquirt ecu? And NO TPS, I think I have one on my intake manifold however, I will be using a stock nikki carby during my instalation of the ignition control

2.) Do I require water temperature and intake air temperature sensors for *just* the ignition part of the control.

I read somewhere the megasquirt can advance timing for cold conditions and retard them for hotter ones. Is this correct. I understand that has more plan in a boosted motor, but I was mainly talking about ease of starting a motor.

muythaibxr

for ignition only coolant and air temperature are probably not necessary...

For ignition only the TPS will do nothing, and even when controlling fuel, the TPS isn't totally necessary

Jobro

iTrader: (2)

What is to gain by using both the tps and the map sensor?

muythaibxr

with TPS, some people feel that accel is more responsive... meaning that accel enrichments tuned using the TPS will make the engine more responsive if tuned right.

In practice it's hard to tell the difference.

Jobro

iTrader: (2)

Can you use map for all the fuel maps etc and then use tps based enrichments?

Would this be the best of both?

muythaibxr

you can do that if you want... I personally like MAPdot for enrichments as tps sometimes makes it hard to catch the off-idle lean spot that a lot of people get.

Really you should just pick what works best for you.

You can use TPSdot for enrichments and MAP for all the maps if you want though.

Jobro

iTrader: (2)

you mean multiplication by dot?

Eagle7

DOT is a term that was probably coined by some aerospace engineers. I think it means "delta over time" or "differential over time", i.e. the rate of change. Examples - DISTANCEdot is speed, and SPEEDdot is acceleration. Thus MAPdot is the rate of change of the MAP signal, TPSdot is the rate of change of the TPS signal.

Jobro

iTrader: (2)

gotcha, its sad that makes complete sense, probably a good thing you are talking to a 3rd Year "Bachelor of Engineering in Microelectronic Engineering - Communication Systems Major". But after doing some computer systems I'm thinking maybe I should have done that.

PS I ordered my pcb today. gonna start on the assembly the day it arrives

Jobro

iTrader: (2)

Should I be using VB921 ignition coil drivers instead of external ignition modules?

The Bosch BIM024's I was planning on using run perfectly fine using the stock distributor system. I'm not actually sure if anyone has used them with a CAS/ecu setp though.

Does anyone know if there would be any downsides to using the tiny VB921 circuits over the large external modules.

Because I think the simplification space and external wiring wise is almost enough to buy a set of 4 and a spare set of 4 and use internal ignitors.

What does everyone else think?

Btw I only have 3 Bosch modules which cost around $60AUS new each, so it would also be economically viable for me to order my sensors and ignitors and pay postage etc from the states.

muythaibxr

I'd use the same setup you're using now... but just use the CAS to feed the MS a signal, and use the ms to feed the ignitors a signal.

I wouldn't use the vb921's unless you don't have external ignitors.