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Jaguar On A Budget, How To Do It On The Cheap! 
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Jaguar is a pretty well built setup that should be capable of surviving some serious abuse. That robustness comes with some cost, however. It IS possible to build a lower cost Jaguar, but it then becomes a much less robust platform.

This is my rough guide on how to be tight with your Jaguar build at the expense of future reliability.

  • Leave out all rail clamp diodes for analogue inputs
  • Leave out all LEDs, blocking diodes, and current limit resistors for them
  • Use only one regulator and bridge the two power supply sections
  • Leave out and bridge over the isolator chip
  • Leave out the 5V clamp setup as without the rail clamp diodes, it's not needed
  • Leave out the 5V rail thermal fuses, and bridge their locations
  • Use an external map sensor for free from junk car, and don't install SMD sensors
  • Leave off the MOV and bridge the reverse bias diode locations
  • Don't install the MAT or MAF ADC sections at all
  • Only install the drivers you need, for example, leave out 4 of the DPAK FETs, 2 of the SOT223 FETs, and one of the FET driver ICs, and all associated resistors, for a 4 cyl seq + wasted setup

If you follow these steps, what you'll basically end up with is like a MS main board, but with proper ignition drivers, low noise, and USB instead of RS232. IE, a fragile setup where one mistake with the wires can cost you a CPU or worse. It certainly will NOT pass any of the tests proposed for Jaguar design quality validation at this point. You can choose to only skip some of the above, however everything you skip comes with a down side, and some things only work as sets.

But it WILL be cheap, which is necessary for some people.

Fred.

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Sun Aug 04, 2013 3:04 pm
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Fred,

On a quick overview I saw there were two pressure sensors on the board. One for MAP & one for BARO. Is there a specific reason for using both? I am in the middle/nearing completion of designing a system (Scary similar to FreeEMS - So I don't contaminate this thread, I'll post some details as soon as I figure out where on the forum it's appropriate & get a little free time.) & my current code just samples the MAP sensor on bootup & stores it off as BARO. This obviously makes the the assumption that car isn't running, or the starter isn't even engaged at board bootup (both of which are of course detectable) I was going to log each bootup reading so I have a known ballpark (fallback BARO) in case I detect an out of bounds at boot, or if the watchdog resets and the ECU re-inits while engine is in fact running.

I had thought one could probably even get a BARO ( a little noisy perhaps) anytime someone goes WOT. That would give me a reason to floor it while climbing Pikes Peak. :) "But officer, my lambda was going to shit!. I had to punch it. "

I do like the concept of having two sensors. You could at least compare the two at bootup to prove that the more critical MAP sensor isn't drifting/broken or othewise behaving oddly.

A #define would allow someone to build without the second sensor for *some* cost saving. Apologies if this has already been thought of/implemented, ect.

Anyhow, great work so far by all!

Lenny


Wed Aug 21, 2013 6:13 pm
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It's just logged for now, and will always be optional. All other methods are flawed, though, and I don't intend to support anything except the real deal. Additionally, the real deal requires a hose running to the best place for a reading, NOT cabin pressure. This may well be the exhaust exit point, or near to it, in many cases. See also: http://faq.freeems.org/#fail

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DIYEFI.org - where Open Source means Open Source, and Free means Freedom
FreeEMS.org - the open source engine management system
FreeEMS dev diary and its comments thread and my turbo truck!
n00bs, do NOT PM or email tech questions! Use the forum!
The ever growing list of FreeEMS success stories!


Wed Aug 21, 2013 6:40 pm
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Gotcha.

Thanks for the link to the FAQ... I don't know why I didn't see the faq earlier. I'll check it out.

Lenny


Wed Aug 21, 2013 9:29 pm
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There are a few pages that I just don't link anywhere, because they're of dubious quality ;-) try subdomain team as well.

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DIYEFI.org - where Open Source means Open Source, and Free means Freedom
FreeEMS.org - the open source engine management system
FreeEMS dev diary and its comments thread and my turbo truck!
n00bs, do NOT PM or email tech questions! Use the forum!
The ever growing list of FreeEMS success stories!


Wed Aug 21, 2013 10:52 pm
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