sim's Volvo 245 comments

All home-built FreeEMS implementations without a forum of their own, usually TA-based.
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Fred
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Re: sim's Volvo 245 comments

Post by Fred »

I'm not sure what the arduino can pump out current wise (edit: "The maximum current per pin is 40 mA." compared to our 20mA for 8 pins = 2.5mA per pin), however my main concern was others reading it and thinking it was OK. I don't know if 1k will drive the opto well enough. You can go a bit lower than that depending on the V drop in the opto when turned on. 1k assumes 5v short to ground through it or vice versa. I said you could do it with 1k directly if the opto was efficient. Buffering it with a line driver is a superior idea, so leave it as is and add that to your diagram such that it's clear to others. Pretty please :-)

Re the fly back, could be OK, shouldn't do any harm, definitely not if through a line driver, roll with it and see how you go, I was just mentioning it for your reference. :-)

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Re: sim's Volvo 245 comments

Post by sim »

Okay, I'll stick with the line driver plan then. I like to stay
conservative.

I'm not sure I have room to squeeze another chip on my board, in
fact, I really don't, so it might be a bit before I get a second
layer set up. I need to make a trip to the electronics store.

I'll leave the edit to my post as-is for now, I don't want to
mislead. I'll document the line driver solution there later when
it is done.
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Re: sim's Volvo 245 comments

Post by Fred »

OK, suits me! Thanks :-) Re the arduino, i edited my post, it can push 40mA per pin, so 82 ohms is no problem for it :-) Hence your success.
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Re: sim's Volvo 245 comments

Post by gixxer-harry »

I must be thinking wrong but..........
If the tacho uses the coil for inputs then the tacho get two signals every crank rotation when the coil dont fire in wasted spark(cil 1 and 3 if the firing order is 1-3-4-2)
Now the tacho only gets 1 signal every crank rotation if u use the coil in wasted spark mode
Dont you have to use two of these boards (1 on cil 1 or 4 ,and 1 board on cil 2 or 3) to make it work?
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Re: sim's Volvo 245 comments

Post by Fred »

Firstly, it depends on the tacho, if it's designed for 2 pulses per cycle or 4 or whatever, then that is what you need to feed it. That's the beauty of the code that I added, it can fire inputTeeth/2 pulses per decoder cycle max, or anything less than that, down to a minimum of one per decoder cycle. IE, with a trigger like the one Sim has, you could run a V12 tacho no problem.

Secondly, on OEM setups with wasted spark coils there is usually a diode circuit to merge the pulses into one signal for the tacho.

Thirdly, Sim has four coils and used to have one. If he could access his signals, which he can't, he could have driven his tacho with a diode arrangement from the combination of four coils equally well. Four pulses per cycle is four pulses per cycle, no matter the source :-)

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Re: sim's Volvo 245 comments

Post by gixxer-harry »

So the "relay board" get its own signal from the CPU and that is 2 signals per revolotion?
Okay than my thinking was wrong (like most of the time),i thought he was going to use a signal from a pin that was connected to one of the coils
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Re: sim's Volvo 245 comments

Post by Fred »

Correct! :-)

He can't use a signal from the coils because his coils are logic level and self driven. Hence this.
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Re: sim's Volvo 245 comments

Post by Fred »

Oh, and the new rev-limit code is very fun! Thanks for that Fred, and thanks for the assistance putting this all together.
You're welcome! My pleasure :-)

Good luck with the tacho board not working issue solving process!
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Re: sim's Volvo 245 comments

Post by Fred »

Having read through both the upstream thread:

viewtopic.php?f=62&t=1263

And this thread:

viewtopic.php?f=62&t=1262

I am acutely aware that i have abused the original author's no-comments thread. Hence here I am adding another post to the 9 page comments thread.

Sim, your 2.5" exhaust, with tdo4/5-h(r)-1[456]g turbo, how rowdy or civilised is it, and how many mufflers does the current incarnation have? Just the one at the back? Or have more found their way in? Contemplating what to run in my 240 wagon. I want to keep it smooth and relatively quiet, but have an easy 300hp at the crank on tap. 2.5 seems like the logical choice for that, as I think 3" would be very excessive and less than 2.5" would feel restrictive and repressive. Thoughts? Any are most welcome! :-)
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Re: sim's Volvo 245 comments

Post by sim »

Fred wrote:Having read through both the upstream thread:

viewtopic.php?f=62&t=1263

And this thread:

viewtopic.php?f=62&t=1262

I am acutely aware that i have abused the original author's no-comments thread. Hence here I am adding another post to the 9 page comments thread.

Sim, your 2.5" exhaust, with tdo4/5-h(r)-1[456]g turbo, how rowdy or civilised is it, and how many mufflers does the current incarnation have? Just the one at the back? Or have more found their way in? Contemplating what to run in my 240 wagon. I want to keep it smooth and relatively quiet, but have an easy 300hp at the crank on tap. 2.5 seems like the logical choice for that, as I think 3" would be very excessive and less than 2.5" would feel restrictive and repressive. Thoughts? Any are most welcome! :-)
Well, the whole comments here thing died long ago.

The original 2.5" exhaust was built for the 242GLT originally.
Image

It lived on the Snot Rocket after the GLT was sold, and before
the Snot Rocket got a turbo.

When I added the turbo to the B21A that came in the car, I redid
the exhaust in 3" tubing.
Image

In addition to the pictured 14"x7" oval muffler, I've since added
a 4"x12" round resonator in the cat position, and a big muffler
in the rear muffler position. All are Magnaflow mufflers, and all
of them have a perforated 3" bore through.

I've added a flex section at the end of the downpipe section.

The whole package is fairly quiet. My process was essentially to
add mufflers until the car was acceptably quiet.

I know that 3" tubing is overkill for my power goals.

I should get an advantage in turbo spool up. My exhaust turbine
housing is tiny, so the big pipe on the outlet is closer to
atmospheric.

I've got to take a hit on VE for having the turbine in the exhaust
stream, might as well keep it small as I can, and have good
response. I'm not after shoot-for-the-moon power.

It's a TD04HL-15G, with a turbine housing from a TD04HL-13T.
The turbine outlet fits a 3" pipe perfectly.

The whole package is not rowdy at all, though it has been in
the past.
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