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Post by Giovanni on Mar 4, 2005 6:44:56 GMT 11
Hi Team,I am running a High Frequency amateur radio station,Yaesu FT100D and a 500 watt amplifier in the 1998 Wizard 3.1ltr T/D.The radio gear is mounted in the cargo bay and the antenna is on the spare wheel mount at the rear door.I have a aux. 90ah battery in the cargo bay connected in paralell via 35mm cable with the 90ah under the bonnett.Coaxial cable runs are short and all the gear is bonded to electrical ground.When transmitting on high power into the antenna,100 watts or more, the engine splutters and coughs.Yet when I dump the same amount of power into a resistive load,non radiating, there is no engine splutter.This leads me to believe the radiated RF from the antenna is getting into the ECU via the wiring harness of the vehicle.May have to try ferrite beads on the sensors and ECU wiring harness.Any ideas and where to find the ECU for the trans and engine??
ciao
Gio
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Post by Roscoe on Mar 4, 2005 9:29:05 GMT 11
Gday gio, You say you have a 98 wizard with a 3.1 motor, Mine is a 98 but I have the 3ltr 4JX1 twin over head cam, common rail motor in it which is fully electronic. I thought the wizards changed over to this engine in late 97.
Mine is a Standard Jap home market spec vehicle imported into this country so that may be the difference.
maybe you can sheild the ecu with something to stop stray emissions getting into it, also is it worth running all your radio gear off a seperate deep cycle battery connected by a split charging unit to the standard vehicle battery,
Cheers mate
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Post by geeves on Mar 4, 2005 15:25:06 GMT 11
I belive the 4jg2 was superseded with the 4jx1 mid 98 so there are Wizards from 98 with the old motor.
Im not a radio tech but what about trying to go the other way and complety issolate the radio from the car . Its quite possible that rf is entering the efi through the earth and short of actualy earthiing the car to an earth stake theres very little you can do.
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Post by Giovanni on Mar 23, 2005 8:02:45 GMT 11
Thanks Team for your replies.
I have found one ECU infront of the "T"bar shifter below the centre dash panel nick knack pocket.Is this the only ECU for the engine/transmission management?I have put some ferrite clamps on all the looms leading to this ECU which has stopped some of the spluttering but not all.Thinking that the errorous signal maybe received via the loom and transmitted to the ECU via the dash sensors I even ran the truck without the gauge cluster,this restricted the transmission gear changes,I noticed no differance in the amount of spluttering.
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Post by morpheus on Mar 23, 2005 20:18:00 GMT 11
have you tried ferrites on the cables from the aux battery to the battery under the bonnet or a bypass filter?
Also, im not sure on teh wiring but what drives the injector solenoids, is it direct from the ECU or are there FETs somwhere under the bonnet?
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Post by James W on Mar 24, 2005 8:23:41 GMT 11
This sounds nasty, I spend a fair amount of my working time dealing with these sort of issues making products compliant to many differant international and military specifications.
This could well chew up a lot of your time in a complex system that you don't have full visibility off. i.e. no circuit diagram of the ECU.
This however comes under two problems, emissions and suspetability. Your antenna emitts RF and obviously the ECU or something else is suspectable.
This can furthermore be broken up in two types of emissions and susecpability; conducted and emitted. Conducted is in cables and emitted is RF.
Emissions should be delt with at the source, as close to the source as possible. Any cable leghth between the noise soucre and the suppressor will be an antenna.
Susecpability in the first instance should be delt with by good design. This is outside your influence.
So you need to deal with the noise at the source. Unfortunately your antenna is supposed to emitt RF, so you can't do anything there either. However there may be conducted emissions. Ensure the earth including the coax cable sheath is good between the antenna and the RF amp. Ensure there are no engine sensors between these two points. The fuel sensor may conduct it all forward into the ECU. Filter the 500W amp power supply, add ferrites, add caps, particulary low impedance ceramics as this is relitivly high frequency. Large electrolytics and long leads often seen in large car sterio systems are a waste of time. Electrolytics are high impedence at RF frequencys and long leads compound the problem. By long I mean anything longer than an inch. A spectrum analysier I am sure will show a mess of conducted noise at the aux battery terminals. Filter as close to the 500W amp power input as possible. Keep leads short, very short to any filter cap. Filter the connection back to the main battery. This with 500W of power will form the bulk of any conducted emissions and without a doubt and will form the easiest path to try first. All the other issues become guessing in a complex system that will never be able to fully supressed. Just think of all that wiring in the vehicle.
You may need to get some techinical help, like a spectrum analyiser to be more analytical about it.
I could go on and on about this with supporting math and physics but will leave it at that for now. Give me a yell if you want any more help.
A thought that just occured to me. Isolate or power the 500W amp externally. If the problems go away it may well be conducted noise, if the problem remains it is suspectable to RF.
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