Bosch Dist. And Vacuum Unit

[Guest Ictoan]

Hi,

This is my first post on this forum so hope someone can advise me.

 

My 205 1.6 Challenge car has always felt down on power compared to

what I thought it should feel like. Tried various things but today decided

to check the vacuum advance unit. Pulled pipe from out of AFM and sucked

gently but felt no resistance at all from the dizzy end. Blowed gently and again no resistance so

I assume the vacuum unit diaphragm is burst. I also refitted the pipe and

disconnected from the dizzy end to blow back through the AFM and it was clear,

so no blockages there.

 

Am I right in thinking that I can replace the vacuum unit and if so do I just

undo the two screws that are holding the unit onto the dizzy, and pull it off

or do I need to dismantle the dizzy completely?

 

Any advice much appreciated,

 

Tim

[hengti 2]

You can replace the advance unit without any other dismantling of distributor

 

I might stand corrected on this, but I'd have thought that you should take the unit off to test it as well - as it's connected to the advance springs/weights whilst it's on the distributor - so you won't be able to tell if the diaphram is bust or not - ??

 

I guess someone'll on here'll be able to confirm/correct

 

 

 

Don't think it'll affect engine power though - only part throttle fuel economy

Edited January 25, 2006 by hengti

[jonD6B 0]

The vacuum unit is (I think) an integral part of the dissy and probably easiest to change the whole thing. Apparently, there shouldn't be any suction on the advance pipe at idle only when it's at 2000 rpm upwards. I thought mine had gone but it turned out to be a poorly tensioned timing belt giving the same symptoms on the diagnostics.

 

(Atleast that's what I was told).

[Guest Ictoan]

Hengti

 

When I blew back through I could hear the air escaping, that's why I think it may be burst. I would expect to feel resistance when both blowing and sucking?

 

JonD6B

 

Having looked at the diagram for the Bosch it looks like it should come off easily enough but wanted to make sure before breaking anything.

 

Has anyone actually had experience of changing the vac. unit?

 

Thanks for the replies so far,

 

Tim

Edited January 25, 2006 by Ictoan

[hengti 2]

Mate,

If you can hear air escaping whilst blowing, I'd also have thought that that would suggest that the diaphragm is split (apols; might have missed that point in your original thread)

I'm assuming that the vac adv unit is basically the same on a 1.6 as it is on a 1.9 dizzy (think so) - in which case they're a doddle to change

All that's holding it on is the two screws and an arm within the vac adv body which goes into the dizzy body and hooks onto the advance weights - just a simple matter of unhooking it

But - fixing it isn't going to affect power - only part throttle fuel economy. If you're sure there's a power issue, the problem must be somewhere else

[Guest Ictoan]

Hen,

Thanks for that.

 

When I first got the car I took it to a rolling road which indicated that it was down about 14 bhp. There is very little 'umph' about it. The cam timing is OK, I've taken off the FSE fuel regulator, fitted another AFM, and Grp N exhaust instead of the Ashley(?) comp item. Before changing the fuel regulator and AFM it needed to be revved to 6k+ to feel anything, now there is a little bit of 'umph' at about 3.5k, but not a lot. Having searched this site I started to consider the dizzy timing and the vac. unit.

 

I was thinking that if the vac. advance was not working the total advance would not be what it should be, therefore I would not be getting the maximum advance I should be getting. (But I could well be wrong as I don't fully understand how it all works)

I was going to try turning the distributor to advance the timing to find some of the missing power, but there doesn't seem a lot of point if the vac. advance isn't working yet.

 

I cannot be 100% sure which dizzy it is, the number on it says 0237 009 063, but unsure if this is a 1.6 or 1.9 dizzy.

 

Thanks for the feedback so far.

 

Tim

[hengti 2]

I'm no expert either, but as I understand it, the vac adv isn't operational at anything other than part throttle cruise (ie. it won't be affecting your full throttle power problems)

 

You could try advancing the dizzy until it *just* starts pinking, then retard slightly to see if that helps.

The state of repair of the vac adv won't affect this operation as I understand it.

 

14bhp down on a 1.6 sounds alot to me though (presume your RR session was just for a reading and not a tune?).

 

If I were you, I'd bite the bullet and take it back to the RR so they can investigate and fix/tune it up. I'm daft with money though, so you could just wait around until one of the engine boffins on here comes round.

 

Henry

[pug_ham 245 3 Cars]

Am I right in thinking that I can replace the vacuum unit and if so do I just

undo the two screws that are holding the unit onto the dizzy, and pull it off

Yes, thats exactly what you need to do.

 

The vacuum advance unit is a seperate unit bolted to the distributor & hooks the balance weight mechanism inside the distributor. The hardest part with the distribuor fitted is getting it hooked back on the balance weight mech.

 

You've done the test already & it sounds like it is dead, a replacement is about £15 from Autofive iirc, Peugeot can get them but usually ask for your distributor number (which you have) & it'll take a few days to get in & cost about double.

 

As hengti already said though the vacuum advance only works at low rpm & wouldn't make any difference to top end power.

 

Is the car tuned to run on UL(95ron) or SUL(97+ron) fuel? The 1.6 doesn't suffer as bad as the 1.9 by running on ul but anything can make it feel down on power.

 

How does the RR operator know it was down 14bhp & how was he taking the reading of the power developed?

 

Are the ignition components all in good condition? What mileage has the car done?

 

Graham.

[Guest Ictoan]

The problem with a 2nd hand rally car is that you cannot be 100% sure about anything!

 

The engine is standard except for a K&N as far as I know. The ignition timing I think is set to about 10 deg, at least the two marks on the dizzy line up and I assume that is correct. The valve timing is correct, checked the holes all line up. I haven't checked the compression ratio, but it is on the list after fiddling with the ignition timing

 

At the RR it measured 101 bhp max at 6200 rpm with a very flat line from about 1500 up. The head has B6D (from memory) marked on it which I believe is a 115 bhp one hence the assumption that it is 14 bhp down. As mentioned before, it just doesn't feel very peppy, if you know what I mean.

 

Firstly I'll fit a new vac. unit and then adjust the timing as suggested by Henry and see where we are. If it's not any better I'll then get the CR checked.

 

Might not get back on to the forum again tonight but hopefully will tomorrow or over the weekend.

 

Hen & Pug, thanks for helping me understand a bit better how the vac unit works.

 

Tim

[pug_ham 245 3 Cars]

At the RR it measured 101 bhp max at 6200 rpm with a very flat line from about 1500 up. The head has B6D (from memory) marked on it which I believe is a 115 bhp one hence the assumption that it is 14 bhp down.

How was it measured & where (wheels or flywheel)?

 

101bhp at the wheels is slightly high imo, especially if it feels low powered. A good 1.9 can struggle to make that power at the wheels so I'm guessing his figures were of flywheel power.

 

I drove Dead205's car last weekend when he wanted a second opinion of if he was right in thinking it was a good one, (he was) but have you driven another one close to the same spec as yours?

 

The engine would be a B6D, not just the head. What year is your car?

 

Graham.

[Guest Ictoan]

Graham,

 

First registered nov 1986. Unfortunately I haven't driven another car to compare but a friend who is a mechanic and is used to rally cars thought it was a bit gutless also, and that it sounded flat.

 

I think the bhp would be at the flywheel. Unfortunately I didn't actually see the RR test (it was over a year ago) and neglected to ask if the figure was at the wheels or flywheel but compared to my road car (2.0l Golf estate) which supposedly has about 100 bhp, there is not a lot of difference.

 

Hopefully I will get the chance to play atround with the timing over the weekend.

 

Thanks, Tim

[pug309twin40s 1]

take of the rocker cover and check the condition of the camshaft lobes.

 

these can wear out on 1.6 engines and then the vavles wont open properly and your lose power and will feel abit flat.

 

have you done a compression test?

[Guest Ictoan]

Hi pug309,

 

A compression test is next on the list, after the timing, but I will have a look at the cam lobes as you suggest.

 

Cheers, Tim

[jonah 1]

Unlikely to be a compression problem I think, that would give other more obvious symptoms (smoke / oil usage / not idling on 4 pots etc.). I've never seen the cams wear on these engines personally but I'd have thought that if it was that you'd notice the noise more than anything!

 

When you changed the exhaust did you notice whether the downpipe had a split tube design (like two D shape sections back to back)? A lot of pattern exhausts don't have this, and this would lose you a bit of power without any other symptoms. Don't know if it could explain 14bhp though.

 

Sounds like the RR you took it to wasn't up to much if he couldn't tell you what was causing the power loss. If all else fails take it to Mikeanics at Congleton, he does the engine sealing for all the Challenge cars so he will have probably seen your car before, and he really knows his stuff.

[Guest Ictoan]

Hi Jonah,

 

Thanks for the reply.

I know exactly what you are getting at regarding the downpipe. The system was a competition one from the manifold. Changed it to the Grp N system plus a brand new standard downpipe with the split tube (shaped like two D's back to back) as the one on the car didn't have it. To be honest, I don't think it made any noticeable difference but I thought it was worth a try as the exhaust bore was a bit too big anyway.

 

I'm also a bit doubtful about it being either compression or worn cam lobes (only uses a little oil when it's been thrashed all day and there is no horrible noises-not from the engine anyway!, but it won't cost anything to check if the timing doesn't sort the problem.

 

With fairness to the RR, it was only booked in on an initial 2hr session and he did give a couple of things to try, but they haven't made much improvement. I was reluctant to write a blank cheque for him to sort it so for now I'm trying to get to the bottom of it myself, more satisfying when you find the answer yourself. In process of ordering a vacuum unit and when I've fitted it I will report back.

 

FYI the car was originally Naveed Iqbal's, aka Navtheace on the Br. Rally forum, well put together and has all the bits but has needed a bit of tweaking to get it handling better. Got that sorted reasonably now (bit low at the rear) and now hoping to get a bit more poke out of it.

 

Cheers, Tim

[Guest Ictoan]

Fitted new vacuum unit and it has made the engine feel a bit more lively at about 3.5-4.0k revs when set at the original timing marks. Top end power probably the same, hard to tell. Advanced the ignition timing and moved the 'lively' band up to around 6.0k revs so brought it back down a bit. When I get more time I will try some more to find an ideal setting and then have a look at the other suggestions.

 

Many thanks for the advice so far,

 

Tim