Electrical Interference problems

[antnicuk]

I have had issues with some of my digital gadgets in the ....pit of the kit car, if I high rev the car they get a bit scrambled and either turn off, reset, give strange readings or just switch on and off again.

I have a shift light with a digi rev counter in the middle of it, I have an ecu display for the microtec screen and a Koso mini digi dash and they are all doing it.  Is it something to do with rotary engines ignition systems?

I have fitted a voltage stabiliser and it made no difference and the problem has got worse since i had it dynoed, where it used to do it very occasionally, it now does it nearly every time. I am using a universal loom for the electrics and the microtec loom for the ecu.

Is there anything i can put in the wiring to stop it happening, also what is it?

[clive]

May be an idea to see if you can run the car with the altonator belt disconected to see if your gremlins disapear as it may be causing what you describe

[antnicuk]

thanks clive,  if it is the alternator, the next question is how do i cure it

[BenLewisMav]

If it is something to do with the ignition system of a rotary engine I\'ve never heard of it happening before to a car specifically fitted with the Microtech ecu..
Maybe there is something in the standard car looms that stops this?
Also could be worth checking over and cleaning/adding some ground points, if you are still stumped maybe Microtech themselves may know.

[arrouk]

it sounds like a lose earth to me ant, try checking all your ground points in  the engine bay and for the gauges.

hth
matt

[AtomicRex]

This used to be a problem with cars with distributors, seems strange to have it with an electronic system!
 
It used to be fixed with a surpressor...so I guess that is a good place to try?
 
But I am siding with the idea that you have a dodgy earth.

[antnicuk]

thanks guys,  i will check the earths but i am pretty sure they are ok,  i have a fat earth wire running from the battery in the boot to the chassis and then continuin down the car where its connected to all the dash earths and the into the engine bay where its again connected to the chassis and onto the engine with a split to the coils.  I will check they are all done up.

I was wondering if there was something in the standard loom that prevented this problem, i have emailed microtech,

[SiH]

Dodgy earth.
However, as above - has the alternator you are using got a built in supressor, and if so, check it\'s fully functioning.

Also worth noting that the \'circular earth/voltage stabilisers\' (Often from SnakeOil inducstries ltd) can often actually make this worse by introducing ground loops. Best bet is to properly upgrade the OEM earths and clean up the mounting points.

However, if you REALLY want to fit a circular earth kit, I\'ve got some magic beans that i could sell you for many cheaps that will also help

[Brett]

What is the shielding like on your HT leads?

[antnicuk]

What is the shielding like on your HT leads?

errr,  none,  they are an aftermarket set.

Where is the alternator supressor?,  i stripped the alternator down when i fitted the turbo and then had the car mapped, so its one other that may have changed since before the mapping,  could this be causing it?  if so what could i do about it,  its very difficult to run the car without the alternator belt as it also runs the water pump.

I will try removing the voltage stabiliser and see if it helps..

[bumpstart]

loose earth and ground loop issue
-- also the use of non resistive plugs and or leads in the tune up has added ignition RFI to the equation
( i find you can use the non R plugs,, but must have at least spiral wound leads with suppression )

and yes,, a problem ALL the time in many aftermarket ECU installs
-- and VERY common on the microtech,, as this unit particulary has poor pin connections
and low wiring standard and has no passive and hardware related filtering or gain adjust

if its not so bad,, it represents as gobbledegook greek on the handset or dash while driving
-- the coms cable is picking up the squeal

evidently the other devices are to,, most likely by sharing a poor earth

if worse,, it will reflect through the ECU Vr input ( CAS )
,, and it DOES cause timing shifts and even supposedly impossible board reset
( i have seen this sort of thing take out all the map data,, a couple of times on different cars )
you will not get much help from microtech,, as they have head in the sand about it
they assume,, and expect a perfect world out there in every bay

-- other manufactures go to great lengths to guard against RFI,, and particularly it contaminating the Vr pulses  
both passively in wiring and connection quality,, and with hardware filtering
-- and also software signal analysis

( not to say others are immune to the effects of RFI,,
 but instead that they know there vulnerabilities to it when used in a Vr environment with reluctor adaption to TTL signal )

[antnicuk]

Hi,

Yes, Microtech have ignored my emails !!

I can understand some of your thread, i\'m not very electronically minded,  sometimes it displays gobbledegook and others it switches off.  So far the map seems ok, fingers crossed.

What sort of things should i be doing or checking to help the problem?

I will check the earths but i\'m sure they are fine.  Will an earth kit help?,  also,  what is a ground loop?  

All the electronics are connected to an earth that goes directly to the battery so i dont see how i can make it any better.  Should i seperate it?

Is there any shielding i can but to wrap the wires or HT leads in to help as this is causing me problems on track, I have no rev counter, speedo or temp gauges, which is not good on a rotary!!

Thanks for your replies

[Brett]

Try a set of stock leads just to eliminate the HT\'s.  I know the HF can cause issues, has the car always had the issue?

[bumpstart]

ground loops occur when the earth is to small, or crap,,
and a big and pulsing device uses the long route to get back to the battery
this may be via other devices
( that why headlights and flashers  go funky when there earth is crap)
principally,, you make some devices in particular have the easiest route to home ground


fail to do this right and it will go via other devices,, picking up the pulse alternating current from some of them
( yes alternators are AC devices )
ensure that other devices ( such as your added stuffs )
are also not squealing or competing along single under done earth



in short,, if you notice the effects of RFI--


get new leads
clean up those IMPORTANT routes to battery,,
be sure those two earths on the micro loom go exactly as printed below
so the ECU will gather its earth at the block and give it back directly to the battery,, with no chance of poor join or shares in between
and make sure the noise suppression caps/ condensors are hooked up,, usually at ignition and alt,, but on FC rx7,, bolted on the firewall

and for you specifically--
you have TWO issues

n01
 throw that silly spider earth kit away
your ecu and some of that stuffs use it to compete for path to earth and surge the current at each other
they may also be feeding EMF at one another ,,
flyback on shut down on shared devices is something you may have to add some caps in for

n02
the greek in the handset tells you there is PLENTY of RFI from IGNITION buzzing about
enough to effect the low volt signal down that com port

-- and the VR from that CAS is oh so next in queue as the next weakest voltages
 so it isnt funny
( they work with pull up voltages and glitches and spikes in the system can effect to be false triggers for timing )

new supressed leads no1 fix for the ignition roar
also making sure that the ignition loom earth on the micro goes to the engine block
and the real ground back to the battery directly
( the biggest ECU tips you can get )

next,, if still bad enough to effect timing
you can wrap the current Vr wires in alum tape for a shield,,
- or simply run twin shield coax out to it
earthing the shield ONLY at the ECU
( a faraday cage )

----------------------------------------

[Prof]

Go with what\'s been said in all the above posts.
 
Digital devices are far more susceptible to \'over voltage\' conditions as well, so any spikes or back emf from relays and motors are going to cause problems if they aren\'t supressed properley.  A good capacitor across the back of the power to the gauges should help (0.1 uf should be plenty), and maybe take the power for the gauges from a \'clean\' source - say direct from the battery positive via a relay if you need to switch them on/off with ingition, as the battery will act like a supressor as well.
 
Most of the automotive voltage stabilisers that you see advertised on ebay are cack - you are better off with a universal power supply for a laptop designed to run from the 12v car feed that can be set to produce 12v output - it will give a very clean filtered signal for the gauges / electronics.