Ignition Amp for 16v

Matt H · Post by **Matt H** » Wed Jul 28, 2010 9:23 pm

Hi all,

I'd like to get started on my 16v again soon, as I've had other projects on the boil, but my first port of call is to test a known good Bosch ignition amp.

If anyone has a spare ignition amp for a 16v I can either buy or borrow for a few days i'd be really appreciative. But it must be a Bosch original... As i've heard too many horror stories about the cheap pattern parts not working on these engines!

I just need to know for sure if it can be ruled out as a problem without spending silly money on something that isn't actually at fault. I will buy a brand new one if it turns out to be the problem.

Cheers,
Matt

Post by **docchevron** » Wed Jul 28, 2010 9:41 pm

6 or 7 pin?

Matt H · Post by **Matt H** » Wed Jul 28, 2010 10:32 pm

I think six, but will have to double check... I seem to remember that when I was last looking the only replacement I could find had 7, and the parts guy told me it had been adapted to work on the 6-pin setup, which was what I wanted.

But still... I'll check. It has been a while

Post by **docchevron** » Wed Jul 28, 2010 10:58 pm

hmmm, Mine's a 7 pin....

prm · Post by **prm** » Wed Jul 28, 2010 11:06 pm

Old unit was 6 pin, part no 0.227.100.123

Now replaced with a 7 pin unit, still with the same number. No problems when installed

Pin 7 is not connected for 16v with 119 ML 4.1 ECU. Not sure if this number and pin connections applies to the very last models.

Regards

.................................

Edited.

Sorry, forgot to add……….

Would recommend removing the ali heat sink/plate on the bulkhead, cleaning and applying a coat of clear lacquer. Then a covering of thermal grease/gel on the rear of the module to improve heat transfer.

Found several early units failed before their time due overheating. Also poor hot starting or breaking down around 3000-3800rpm.

electrokid · Post by **electrokid** » Thu Jul 29, 2010 12:11 am

If anyone has a duff or suspect one they'd like to send me - I'll have a look and trace out the circuit and have a look for any weak points in the design and ways to get around them.

Post by **docchevron** » Thu Jul 29, 2010 1:06 am

heat seems to be the only major weak point...

Odd that though PRM, when my original 7 pin cooked the bloke form Bosch gave me a 6 pin and said "it'll be fine they're all like that now mate"..
Only when I plugged it in the car mis-fired like buggery and wouldn't rev past 3K...

electrokid · Post by **electrokid** » Thu Jul 29, 2010 12:11 pm

heat seems to be the only major weak point...

If it runs hot enough to cook itself then the design is marginal. The use of better / more modern components may be part of the answer. I can't find the cct in the workshop manuals - no change there then. Where is it located on the BX ?

The job the amp has to do is very very simple and IMHO there's no excuse for unreliability here - so every possibility of being able to improve it. I have the cct for what is very likely to be a Bosch since my other car is made in Germany - from its workshop manual - it's simply a line of emitter followers - very basic - very bulletproof - and for that reason I've never had one fail in 200k of motoring in this marque - in fact I don't even know where it is under the bonnet !

prm · Post by **prm** » Thu Jul 29, 2010 12:16 pm

Doc, you could be right, as my last purchase, 7 pin unit goes back to 2006.

The 3k rev limit on your 6 pin, could ?? possibly indicate the body been spiked by a 12v positive external source or faulty screening on the input signals cables.

Kind Regards

prm · Post by **prm** » Thu Jul 29, 2010 1:24 pm

Electrokid ,maybe you should drive a 16v and really push it to realise how hot they become!!!! especially with no cooling fan run-on.

Failure or misfire faults are not within the general design of the module but down to heat retention, due to the position on the bulkhead and installation.
I also agree, the unit should electronically outlast the car.

Over a period of time corrosion builds up between the module and the ali sink plate, reducing heat transfer. Found several early 16v’s had no thermal grease/gel applied.
Also the wiring and connections inside multi-pin plug are inclined to corrode and become brittle, increasing the temperature on the unit.

Regards

electrokid · Post by **electrokid** » Thu Jul 29, 2010 7:27 pm

Electrokid ,maybe you should drive a 16v and really push it to realise how hot they become!!!!

Oooo - yes please

anyone going to lend me one

increasing the temperature on the unit.

Yes I get the problem.

The use of better / more modern components may be part of the answer.

Ok I know it's not the done thing to quote from my own post

it's a bit of a minefield because device manufacturers don't tell you the whole truth in their datasheets ! Let me give you one of the more glaring examples - the power transistor BU208D - designed for TV line drives, several manufacturers just tell you what you need to know for that application only so they tell you that the max average power is 12.5 watts and they'll also tell you to 'derate to 150°C'. They probably don't tell you the max continuous power because they've made it out of chewing gum and the figure is rubbish.

There are a couple of manufacturers of the BU208D who give more info in the datasheet - because they make a good transistor - ST Electronics for example quote continous max power at 150 watts - which suggests that it has significantly bigger balls than the ones at 12.5 watts - it also quotes Tmax at 200°C and gives the curves for derating. The one that says 'derate to 150°C' doesn't actually say that it will still work close to this temp whereas 'Tmax' says that it does continue to work up to 200°C even though it's not as capable depending on the derating curves -and designers should be using devices within the derating curves anyway.

It's for those sort of reasons that you won't find any other type of BU208D in my stock than those made by ST Electronics - and if I happen to fit one under the bonnet of the BX it's not going to die just because it's Summer

Post by **docchevron** » Thu Jul 29, 2010 7:51 pm

prm wrote:Doc, you could be right, as my last purchase, 7 pin unit goes back to 2006.

The 3k rev limit on your 6 pin, could ?? possibly indicate the body been spiked by a 12v positive external source or faulty screening on the input signals cables.

Kind Regards

Possible I guess... I sourced another 7 pin and it was fine, I did try the 6 pin in KMO and that ran like a bag of shit too, so I guess it could have been a duff unit maybe?

Electrokid wrote:and if I happen to fit one under the bonnet of the BX it's not going to die just because it's Summer

The unit lives on the bulkhead behind the battery...
I have no idea what lurks beneath the lid since I'm no electrician though... mine doesn't emit it's precious smoke, so I guess it's all good right now..
But, a decent permenant cure would be nice, I still get a bit twitchy on the hottest of days sat in traffic, almost waiting for it to melt!

electrokid · Post by **electrokid** » Thu Jul 29, 2010 10:22 pm

The unit lives on the bulkhead behind the battery...

Hmmm - sounds sensible enough - difficult to find somewhere cool under there. If it's always heat that kills it then it's probably more likely to fail - as you say - sat in traffic - rather than cruising along. Still not a great deal of airflow there I would think (and only heat rising from the exhaust when stationary !) perhaps a 12v computer fan to keep it cool - there's a round hole in the inner wing - don't know whether it's accessible with the battery there - perhaps a fan drawing air from the hole / nearside wing cavity and piped towards the ignition amp ?

But, a decent permenant cure would be nice,

Yeah - I'd like to take a butchers at one - all my BXs have been diesel !

Post by **docchevron** » Thu Jul 29, 2010 11:01 pm

hmmm, I think I have an old dead one laying around somewhere..
If I find said I'll gladly post it your way if you want to open it up.
Dont hold your breath for it though, it could be in the garage, where I haven't ventured for about 5 years, and it's full to the gunwhails with crap!

electrokid · Post by **electrokid** » Fri Jul 30, 2010 12:14 am

hmmm, I think I have an old dead one laying around somewhere..
If I find said I'll gladly post it your way if you want to open it up.

Thank you - yes I'll certainly be interested to do that - I'll PM you with my address when you find it - cheers.

Dont hold your breath for it though, it could be in the garage, where I haven't ventured for about 5 years, and it's full to the gunwhails with crap!

Mine's the same - a couple of months ago I decided 'it's no good - I'm going in...' and so I had a sort out and created a small amount of space - even threw some stuff out

Since then I've acquired - a set of BX seats - 5 wheels + snow tyres - a diesel pump - an HP pump - plastic manifold etc etc - and it all just fits the space I cleared a couple of months ago

Hey ho - go back to the beginning do not collect £200 etc