reno808

how come??

333pg333

PM sent Thom.

A.Wayne

The older Bosch system is specific for that setup the 60-2 done on the newer cars are for more resolution not less. Many say they can work with anything , stick a digital timing light on them and watch them run ...

Chris White

If you are just looking at base costs – the Haltech Sport 1000 ECU is just over $1300 and the Electromotive Tec-S is $1249 for just the ECU.

The stock system is not a trigger wheel, is a starter ring gear! A proper trigger wheel, regardless of tooth count, has square teeth to give the best trigger signal. Some of the systems I have looked at that use the stock ring gear do not calculate engine rpm in real time, they calculate it once a revolution. On a fast accelerating engine this will cause timing errors. Real high performance ECUs calculate the crank position every tooth and as a result can give ¼ degree accuracy in the ignition timing. As A Wayne mentioned – put a timing light on it and see how steady the system is at idle. If it moves at all at idle you can only imagine how sketchy it will get at speed in dynamic conditions.

See above…plus I have no wish to reuse old sensors in mission critical areas. The only old sensors that I ever reuse and coolant temp sensors – and if it’s a race engine I replace those too. I also want the ability to set the trigger up the way I want to – set the lead time of the home signal (missing tooth on a 60-2 system or a cam position sensor). The position of the home signal is dependent on the max ignition advance you want to use. Some systems are locked into a specific lead timing, some are not. Another reason for preferring not to use the stock trigger is accessibility. There is a definite benefit to having quick and easy access to any vital sensor on a track car. You never know when you may have to change something!

I am sure people can get het stock trigger system to work, and maybe even work well – I just don’t think its optimal and I am not into compromises when it comes to management systems – if you want to install and set one up then do it the best way possible.

333pg333

Pretty much what I've found. Seems as if Electromotive, Wolf, Motec, and also LINK have discovered this.
Many are in fact offering a front wheel kit for this reason. This is why I am interested in Thom's experiences?

Thom

My experience with adjusting the base timing on my set up with a timing light is that it did not move one bit, and that was with watching the OT mark for a good 10 minutes to check how stable the system was (serious headache following...!). This tells me the CAS used on my set up is precise enough for this application.

As for tooth squareness :

a/ I'm not convinced that the starter ring gear is any less square than the tooth on a S/S2/968 flywheel - did a clutch job a 944S last weekend and the tooth on the flywheel didn't seem particulary "more square" than those on the ring gear.

b/ How could "tooth squareness" matter when used only for a reference sensor dedicated to measure engine speed only? Can the version of the factory Bosch ECU used with the 60-2 set-up (16V engines) compensate for the varying distance between the position sensor and the tooth during the arch of circle of the period of the tooth? I doubt it since the same position sensor is used on both 132 and 60-2 set ups.

c/ If the ECU cannot compensate for the varying distance between the sensor and the tooth, which will be varying greater the wider the tooth, the maths just say that for 132 counts for a revolution the sensor is triggered more than twice than with a 60-2 set up, hence better resolution at measuring engine speed.

Raceboy

On good systems, reference sensor is only used for determining TDC position and engine speed is calculated by teeth. Cam sensor indicates which TDC (1st or 4th cylinder) it is.

Chris White

Looks like a little basic info is in order - a magnetic (regular or Hall Effect) sensor does not count ‘teeth’, it measures the ‘change of state’ of the trigger wheel. An electrical charge is created when the leading edge of the tooth passes by the sensor and another charge is created when the trailing edge passes the sensor. The amplitude of the signal is based on proximity. If the trigger tooth has any ‘ramp’ to it (less than completely square) it will create a signal with some analog function and the ECU will have to ‘guess’ at what voltage level represents the actual triggering event. Starter gears tend to have less that square teeth – they need to in order to mesh with the starter without causing undue wear.

All that being said – the 944 starter ring gear does have a profile that is ‘squarer’ than most.

As for the compensation for varying distance – its not an issue since the signal voltage generated by the small change is distance is minimal – it is also important to note that the signal delta will be opposite to the rising leading edge. Most good stand alones allow you to choose between a rising or falling trigger. If you chose the rising signal then the slight falling due to the increase in gap distance during the tooth passage is truly irrelevant. I will give you credit for a good try on that point!

In truth the stock ring gear should do an acceptable job in creating a signal for an ECU. My main objection to it is the idea that you can set up your new ECU using the old stock sensors. If you replace the stock sensor with new ones and make up your own wiring harness from the new sensors to your new ECU that will greatly reduce my objection to the implementation of a stock type set up. I still find the position of the sensors and the gap adjustability a maintenance annoyance! I still have a concern about the use of the trigger signal. Some of the systems that I have looked into that have the ability to use the stock trigger system do not calculate the engine speed at the passing of every tooth. Some just use a software based system that calculates the engine speed once a revolution. So you have more trigger events but a lot less final resolution due to the software algorithm.



Not a problem……even with the auto tensioner in place!

Thom

Thanks for the clarification.

It goes without saying that installing a modern ECU/wiring harness without all new sensors (OEM or not) makes little sense.

Yes, the factory location of the crank sensor is not the most convenient, but to be honest it should not need to be adjusted every other day and it still probably requires less work than installing a replacement sensor elsewhere.

333pg333

Hehe, I was hoping you'd post that. I couldn't find it. Thanks.

Thom

This is what Ray Hall from Vi-PEC has to say about the triggering :

I suppose this means that the ring gear on our cars performs well enough when used with an ECU that can count each of the 132 teeth of the ring gear, such as the Vi-PEC.

I don't have any experience with the Link ECU but if it's as similar to the Vi-PEC as the user interface suggests, I suppose the Link will perform just as well.

From that point I'm not sure how a 60-2 set up could offer as much resolution, unless perhaps if using some compensating algorithm.

theedge

Vipec is similar to the Link you mean Link makes the Vipec.

Chris White

You identified the interesting part in your last statement. I can speak for the Electromotive system – which by the way developed, patented and licensed the 60-2 tooth trigger wheel system). The electromotive ECUs use a complex modeling system to use the trigger impulse, the current rotational speed and the rate of change to identify the current crank angle accurately. If you just look at the teeth and you are close, but not perfect due to the dynamic nature of an engine. In reality most of the current crop of EMS do a pretty good job, in the past there were some that had pretty significant errors in timing.

My main objection still stands – old sensors and wiring are not a good starting point for a good management system and the original set up is not easy to work on if track side tweaks or repairs are needed.

Thom

Hey Brian, does it really matter which of the chicken or the egg came first...

Chris White

Depends if you want an Omlet or a Chicken Sandwich!