Dean's Activa/XM/V6 and now Talbot blog

Unread post by **myglaren** » 09 Apr 2011, 07:46

That doesn't look simple to me at all!

Are you sure it isn't out of the space shuttle?

robert_e_smart · Unread post by **robert_e_smart** » 09 Apr 2011, 08:08

Ohhh, good, I like to see autoboxes being taken to bits, the more knowledge about them out there, the better.

Whats your car doing Dean?

Deanxm · Unread post by **Deanxm** » 09 Apr 2011, 09:16

I know it doesnt look simple but really its just hydraulic shuttle valves v's spring pressure with dampers, its just a citroen hydraulic system in minature in a box, to see it with your own eyes would make sense.

Robert it was sometimes shifting roughly into R, when putting it in gear it would always just settle smoothly if you know what i mean, now it goes in with a jerk.
Also sometimes i get a slight 3-4shift delay but i think ive sorted that.

Here is one for you thouhg Robert, last night afer i was messing around with the box i came in and trawled the net for specs to see if i could get spring specs, i couldnt find any but i found another exellent manual for the 4HP18 which explains the operation of the box and hydraulic circuit diagrams, because im sad i sat up to the small hours of the morning reading it and trying to finaly get to grips with the operation of the box and do you know what conclusion i came to?
The valve block cannot control shift points, but you proved it can obviously so i had another look, did the car the block came from have a turbo? was it a low blow TCT too? that may make all the fifference as it runs half the boost of the dervs and this would ruin your shift points somewhat, need to look into it more.

D

robert_e_smart · Unread post by **robert_e_smart** » 09 Apr 2011, 10:55

Interesting Dean,

The first valve block swop was from a TCT. WIth the "wrong" shift points. Then I put a valve block on from a 2.1 TD, and it is better than the original TD valve block that was on the car. But the changes happen at slighly different times.

So what is it that controls the change points??

Deanxm · Unread post by **Deanxm** » 09 Apr 2011, 12:53

The change points are governed by the regulator, the regulator has 3 stages on our boxes and as far as ive read stage one activates a reverse lockout, so as soon as the car is moving stage one is stroked by centrifugal force and bocks fluid flow to the reverse lock up clutch, then the other stages are basicaly pressure regulators or a hydraulic speed sensor and act in the same way the load compensator (kickdown cable) does, basicaly modulating fluid pressure that the shiftvalves see to allow them to stroke (initiate a gear change) by overpowering the aposing spring or not.
There is also a boost operated pressure modulator, this operates under the same principle as the kickdown does but instead of pulling a valve mechanicaly with a cable it uses boost directly from the induction system to increase or decrease pressure and thus shift points.
So although the shift valves are in the main part of the valve block the decision to shift comes from the kickdown valve (mounted on the underside of the valveblock), boost modulator (bolted to top of valve block) and centifugal regulator (on final drive).

The actual valve block itself isnt a valve block, its just a casting of oilways that takes fluid to all the shift valves and pressure regulators to the main housing of the gearbox and thus the clutch packs, they would have used pipes but with so many oil ways this way the most compact, reliable and cost effective way of doing it, and its a work of art.

Also found what ive been searching for with regards line pressure, it would seem the gearbox runs at between 110 and 190psi depending on load and engine speed, reverse actualy puts the highest demand pressure wise on the gearbox, so not a great amount of pressure in there at all really, no wonder none of the oil ways use gaskets.

D

Deanxm · Unread post by **Deanxm** » 10 Apr 2011, 19:35

had a little sit down in the sun this evening with a drink and rubbed this down, just warmed it up and painted, now its going in the oven and then i wll get some clear on it quickly.
Can you guess what it is yet

CIMG3261 by Deanxm, on Flickr
Should set things off nicely with the rocker cover the same colour and maybe the inlet manifold too.

D

Unread post by **CitroJim** » 10 Apr 2011, 19:54

Dean, that's incredibly interesting on the 4HP18 valve block and a very good explanation on how it and the regulator works

You sure know your autoboxes...

That paint job looks very good and I'd guess it's the sump cover from the autobox...

Are you going to colour-code your spheres too?

Deanxm · Unread post by **Deanxm** » 10 Apr 2011, 20:46

Im learning slowly Jim, with these cars getting on a bit now the more we know about the auto's the better, in fact i would say we xm owners are well behind Saab fans in HP18 knowledge.

Yes it is the top cover, and i saw the colour coded spheres on that tweaked activa, it looked exellent but as far as im concerned spheres are green like the fluid they run on, i was thinking about making up a perspex LHM tank, now that would be cool and rather easy, just want to get the other more important stuff sorted first.

D

Deanxm · Unread post by **Deanxm** » 17 Apr 2011, 20:09

Bit of an Activa update.
i finaly have some good boost, turned out putting a restriction in the boost line to the boost controller has allowed everything to work as it should, i cant ever imagine the car produced any more than wastegate boost, it was running 3 boost controllers in series, the restriction on the pipework was huge and could never have bled boost away from the wastegate fast enough with all that to pass through let alone the fact the pipework isnt big enough to cope with piped up properly.

The long and short of it is, it goes like a stabbed rat

, boost can be set from within the car to between 5 and 12psi, at 12psi it produces great accelleration, i think now its runing right the remap is really shining, and eating my fuel..................must stop driving it, must stop driving it, must stop driving it

Have not really touched the xm yet, im waiting for a new A/C condenser and some other bits and bobs.
Truth is work has started on the dining room now and cars are going to take a back seat for a while

D

Unread post by **CitroJim** » 18 Apr 2011, 19:19

Dean I'm delighted you're really enjoying the Activa

A good, well set-up one is such good fun. Have you discovered at how slowly everything else seems to be going when you're piloting an Activa?

They may not be the all-out fastest cars but they surely do cover a lot of ground at a high average speed die to their ability to go round corners and to ride across dodgy surfaces pretty well. have you noticed the suspension works better at speed than when going slowly?

Deanxm · Unread post by **Deanxm** » 18 Apr 2011, 20:32

Yes jim it rides rather well at speed, not a patch on the xm for comfort but then the strut spheres have a smaller damper hole for starters and its running slightly lower profile tyres but it has the waft but not as often and it doesnt handle ruts as well as the xm.

I had to pick up a battery for an MX5 im working on this morning and while i was at the scrap yard i picked up a bosch recirc from a 95 Saab.
I wanted to get one as i could very clearly hear compressor stall when lifting of the throttle and i just dont likethe sound of it, it sounds stressfull.

With the (£2

) Recirc now fitted there is a very muted sssshhhhhhthtt, a far less mechanicaly stressed sound so im happy.

Performance wise i went out with my dad in his 3L V8 Stag for a thrash at the weekend and i managed a 0-60 of pretty much 7sec dead not bad considering its only a low blow 8v lump, the remap is making its thirst for fuel a little heavy though, i get more than i could from my old 2.3t saab which would best 21mpg being very good and 12mpg best if being very very bad, it would drop to 1mpg when you put pedal to metal on the trip though!
The activa seems to be doing 25mpg if im good but 18mpg whilst having fun which is ok for over here really.

Anyway, yes im enjoying it more than i thought i would its a pretty good car, no out and out racer, but the suspension is impressive.

D

Citroenmad · Unread post by **Citroenmad** » 18 Apr 2011, 21:26

Very similar to my findings with the Activa.

The ride is good but not on the same level as the Xm is. Though on some individual bumps I find the Activa rides slightly better than the C5s and XM as it doesnt seem to get pulled down into the bump as much as those. Seems to be to do with the ARBs?

There is a very odd bit of road not too far from here, its a road down the coast which is extremely undulating due to how the drainage system works. Its one after the other of dips and rises in quick succession. The best car I have been down it in is a CX, its wheels seemed to absorb the bumps at high speed. The Xm is good but not as good as the CX was. The C5 is ok, but at higher speeds the softer 52 plate starts to take on the rhythm of the road and gets upset and runs out of suspension travel. Depending on the speed its quite an uncomfortable stretch of road. A lot of people potter down it as silly low speeds due to their cars having no suspension.

However, the Activa seems excellent on it, not sure the reason for this but its virtually imperceivable, almost as good as the CX.

So in some cases I find it more comfortable, however in most the extremely comfortable XM can offer much better ride quality.

The Activa is a great compromise of everything.

I agree with your last comment Dean, pretty much what I think too. Im liking it a lot more than I thought I would and for such a comfortable car the drive it offers is exceptional. My kind of car, comfortable, quick and handles excellently.

0-60 of 7 seconds is very good for the Activa Dean. I didn't know you had it remapped, I guess a ECU remap. What kind of bhp would that have given? Gareth tells me mine is running around 12PSi of boost, it seems quite brisk!

andmcit · Unread post by **andmcit** » 18 Apr 2011, 21:42

One thing's for sure; I'm feeling the love here for Activae...

And folk wonder why I'm up to 8 of'em. Again!!
Mind, you took your time Chris!

Deanxm · Unread post by **Deanxm** » 18 Apr 2011, 21:56

technicaly the Activa can remove its arb by allowing fluid to flow freely in and out of the arc ram and so should give a softer ride in a straight line, although this does not happen in practice, ive yet to find a road the Activa is better than the XM on but i think you are right, given the right conditions/surface the Activa could shine and outperform the xm although most of our rroads are rutted with a broken surface and hydraulics dont like that, the gravel potholed road to work though is another matter the xm will do 70 or 20mph down there, ive done it recently, and its like its on fresh tarmac, it amazed me actualy as i hardle ever drive it on that sort of surface but the ride was just something else. the activa did not like it so much but then with that damn arc bush rattling away it makes the experience a little less plesant, noise seems to creat discomfort where the re is none if you know what i mean.

Anyway, power wise, i would think the map would be good for 20 maybe 25bhp extra boost with my bigger intercooler maybe 15-20bhp tops, the intercooler works really well actualy but then it should, its beedin huge

The previous owner said it was running 200bhp and after getting the boost up to 9psi (my guage is over reading a bit i found out today) i think its actualy about right maybe hovering around the 1850bhp mark from experience but then the weight of the thing may have me underestimating but its very hard to tell.
But it does do 0-60 pretymuch 7sec dead which is a bit of a threat to even the 24v prv xm, certainly a V6 xantia as i had a little race with a silver one over here and the Activa pulled away from it well, the V6 does have the Auto box though which will slow it off the line.

Do you know what though......................my 8v auto xm is still the better car in my opinion, yes its slow, yes its got a dino box but you know what? its got something no xantia has got and im not just talking about space to put your sunglasses, wallet and phone without them sliding around in the door pocket...............the xant just doesnt have the presence, i have been stopped in the petrol station by people in the Activa but its invisible compared to the xm, people go crazy for that and it feels so good to drive.
Am i weird? i dont know but i know that when its perfect and i sell the Activa i wont shed a tear for it..........................secretly i think i would if i had to part with the xm

D

andmcit · Unread post by **andmcit** » 18 Apr 2011, 22:24

So the Activa'll be on eBay and the For Sale section here sometime soon?

Sometimes presence isn't what you want when you're being slightly naughty
with the speed limit and why an Activa or V6 Xant can be totally invisible.

Be honest, who are you trying to impress anyway? Whilst sometimes it's
nice when someone says they'd love to "own a car like that" I can tire of
trying to educate and/or correct the ignorance of the queries I get when
driving my Cx GTi T2.