st3ph3n Posted March 29, 2009 Posted March 29, 2009 Chaps, how would I step down 12v from a battery to between 4.5v and 5v? Trying to fool an ECU here!
ANDYJDMSTI Posted March 29, 2009 Posted March 29, 2009 (edited) Chaps, how would I step down 12v from a battery to between 4.5v and 5v? Trying to fool an ECU here! Try this - Converters depending what you are trying to do you can chop the end off the adapter and b@stardise to suit! Edited March 29, 2009 by ANDYJDMSTI
evil evo Posted March 29, 2009 Posted March 29, 2009 try the boys at maplins you can use a thingy resistor cant remember what you call them ,they are useually surrounded in a ceramic case as they do get hot , techys in maplins should be able to give you right value
ed-209 Posted March 29, 2009 Posted March 29, 2009 Andy way of doing it is the right way, maplins should sell these also. it needs to be a regulated one as the car voltage goes up and down 9v on cranking the engine to 14v when running and charging the battery. .
scouk Posted March 29, 2009 Posted March 29, 2009 Curious to know what your doing there! Potentially the best way is as mentioned above, get a cigarette lighter adapter and hide it somewhere out of sight.. Trying to work out something similar at the mo for an Onbard Computer For some daft reason I get 4v on the dipped headlight circuit when just my sidelights are on.. Don't ask me why cause I've no idea.. Wouldn't mind knowing though..
JohnSt Posted March 29, 2009 Posted March 29, 2009 Stephen if you simply require a fixed voltage, I'd just spend less than a Quid and stick an 7805 in there Maplin product code UJ54J. ---john---
st3ph3n Posted March 29, 2009 Author Posted March 29, 2009 Thanks for the replies chaps. It's not for my car though, for a mates bike engined one and he asked me for my electronics knowledge. Unfortunately I've forgotten everything I learned 12 years ago when I did my module b in electronic construction in high school. Will look at the options with him in the morning. The wiring loom has a couple of wee issues and we think supplying this signal would solve one of them.
paul_lawrence Posted March 29, 2009 Posted March 29, 2009 (edited) hi guys, this is all my fault Cheers Stephen, I thought he was better than me at this stuff, clearly not, but he has you lot to call I have a kitcar with a bike engine it which I am trying to compete with in the Hillclimb Championship. The previous builder/owner decided to chop the loom right back to the absolute minimum and has gone a bit too far. The car uses a 3rd party dash/speedo arrangement so the clever chappy decided not to include/wire up the speed sensor. On the ZZR1400 the ECU checks for a valid output from the speed sensor in two ranges - 0.05v to 0.09v (when I believe the sensor is not picking anything up) and between 4.5 and 4.9 v when it does. It sends 4 pulses for each full rotation of the engine. Right now I have an open circuit which the ECU determines to be an error and helpfully restricts itself to being in 6th gear to try and stop mad people trying to break the 200mph barrier by just cutting the wire. When I hit 9800rpm in any gear the ECU thinks it is doing 186mph and the rev limiter kicks in. Crazy stuff. My plan at this point is to try and send a constant voltage from one of the two ranges above and try to get the ECU out of 6th gear by giving it a valid reading although this would make it think that I am doing a constant 0mph Hopefully you have stuck with me this long and can help. The fixed voltage solution looks great but I need it to be just lower than 5v. Any quick and easy suggestions as this is a bit of a punt, but worth a shot. The other solution (if I can source one) is to buy a new speed sensor and just wire it up under the dash. Cheers Paul. Edited March 29, 2009 by paul_lawrence
the squiggle Posted March 29, 2009 Posted March 29, 2009 Possible to find out what a classic gearbox speedo output voltage range is. 97 - 00 cars had a electronic feed to the speedo head and there is a good possibilty that this gives a 0 - 5v linear output, earlier 92 - 96 cars were mechanical drives from box to speedo head Someone on 22b would be able to confirm what voltage the Subaru speedo outputs at if no one on here can assist Good luck in the coming year
terzo neil Posted March 29, 2009 Posted March 29, 2009 i think its for a bike engined kit car grant, as impreza's dont red line at 9800rpm at 186mph
the squiggle Posted March 29, 2009 Posted March 29, 2009 What Paul is trying to do is fool an ECU If a component from any car can output the voltage he needs then he can use it regardless if what EFi ECU controlled engine he is trying to bluff. As i knew Subaru 's like to use 0 - 5v for numerous sensors in the system i reckoned using one of them would work by giving 0v at standstill and 5v at full rotational whack, TPS would even be helpful 97 - 00 cars use a pulse system from gearbox to ECU and this cuts everything at 180km/h. We fool the ECU by fitting a gearing device with 1.6 turns to 1 and this shuts the car down at 180 mph instead of 180km/h As i said someone on 22b.com would be able to confirm what voltage range a gearbox drive from a later outputs at
JohnSt Posted March 29, 2009 Posted March 29, 2009 Hi Paul, easy thing to do. If you need to show it a little less than 5V just use an appropriate Zener Diode. Stephen here's an idiots guide http://www.mayothi.com/diodes.html Personally I suspect the code will be a little more clever than to be fooled by a fixed voltage, but it's worth a try !! ---john---
st3ph3n Posted March 30, 2009 Author Posted March 30, 2009 John - Paul wants to know if there's an idiot's guide for slow children as he's struggling with that one!
JohnSt Posted March 30, 2009 Posted March 30, 2009 John - Paul wants to know if there's an idiot's guide for slow children as he's struggling with that one! I managed to stave that off till I was 39 so it is do-able The technique is a well guarded secret
st3ph3n Posted March 30, 2009 Author Posted March 30, 2009 Right. Turns out we have an ex-maplin man in the office so we're going to try the 7805 you suggested John. Pop down to Maplins in Hamilton tonight for the bits then give it a whirl. Thanks for the help everyone.
st3ph3n Posted March 31, 2009 Author Posted March 31, 2009 We ended up building this last night. The 5v Voltage regulator with a wee extra resistor just to knock it down to within the tolerance zone of 4.5 to 4.9v. That all worked great and when were wired it into the loom and turned the ignition on we were getting 4.88v reading through it which was spot on. Unfortuantely it didn't solve the problem so I think Paul is going to source a speed sensor and be done with it. He's spoken to someone today who says that it needs to be a pulsed signal rather than a constant on. Damn those clever jap ecu makers!
JohnSt Posted March 31, 2009 Posted March 31, 2009 (edited) Did think that would be the case Stephen. It want's to compare RPM to Speed to figure out what gear it's in by the sounds of it. ---john--- Edited March 31, 2009 by JohnSt
st3ph3n Posted March 31, 2009 Author Posted March 31, 2009 Could be John. All to try and stop these bikers killing themselves! Does mean that if we get it all working properly then Paul might need a speedo healer to unlock maximum revs in 6th. Not that any of the circuits in Scotland should require that at this moment in time. Especially with East Fortune off the calendar.
paul_lawrence Posted March 31, 2009 Posted March 31, 2009 (edited) hi guys, yes, no luck but thanks for the help. It was a bit of a punt! The ZZR and newer bike engines tend to have mechanical gear selectors, but it apears that the ECU does do more checks than I hoped. Managed to source a speed sensor and will try to get it wired in before Kames. Just need to get it mounted and pointing at the propshaft bolts Wont be the same without you taking short cuts across the grass John Good luck in your new exploits... edit - just spotted Stephen's question - my Gi-Pro will allow me to trick the ECU into 4th gear - so no top speed issues other than the thing shaking itself to pieces... cheers Paul. Edited March 31, 2009 by paul_lawrence
JohnSt Posted March 31, 2009 Posted March 31, 2009 Wont be the same without you taking short cuts across the grass John Good luck in your new exploits... Now what makes you think I won't be around cutting the grass this year ? ---john---
paul_lawrence Posted April 1, 2009 Posted April 1, 2009 you might grace us with you prescence for the odd test, but I heard that Mr Bremner had scared you off.. you there on the 11th and 12th then? P
st3ph3n Posted May 5, 2009 Author Posted May 5, 2009 http://ninjabogey.wordpress.com/2009/05/05...on-as-promised/ Thought I should post this up as the issue was finally solved at the weekend.
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