4hp20 lock up question

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Post by CitroJim »

Stempy wrote:At what point does it tell the engine ecu to back off the ignition timing?
On downchanges I believe. I can confirm later after a consultation of my HP20 bible...
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Post by Chris570 »

xantia_v6 wrote:
Chris570 wrote: Mine has changed in the past few hundred miles from being powered with cream to being a lot more solid in the way it changes gears if that makes sense, the TC will still slip in doddery git mode but not much. the gear changes are more noticeable now than they were. i'm watching this one with a close eye
From my experience of that car, it will gradually get smoother again. The auto-adaptive logic is struggling to find a set of parameters that it is happy with.

The "firm" (if not "clunky") phase is rather like the behaviour for the first few miles after a Lexia reset of the transmission parameters.
Just a thought here with it being a mk1 box on mk2 ecu are there subtle differences with the internals that could cause it to throw a tantrum and then re-learn everything?

also, driving in snow mode, is that bad for the box to do it frequently?
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Post by xantia_v6 »

Chris570 wrote: Just a thought here with it being a mk1 box on mk2 ecu are there subtle differences with the internals that could cause it to throw a tantrum and then re-learn everything?

As far as I know, the same 4HP20 software is used on Xantia Mk1 and Mk2 and XM (there were a couple of updates, apparently including one to eliminate the 3000 RPM upchange when cold), but there should be no problem with backward compatibility.
Chris570 wrote: also, driving in snow mode, is that bad for the box to do it frequently?
On this transmission, I don't think that there would be any bad consequences (other than performance and fuel consumption), the oil in the torque converter will be working a bit harder, but none of the mechanical components should be stressed.
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Post by CitroJim »

Chris570 wrote:Just a thought here with it being a mk1 box on mk2 ecu are there subtle differences with the internals that could cause it to throw a tantrum and then re-learn everything?


Well, My MK1 is effectively talking to a MK2 Valve Block from a MK2 2.2HDi and seems more or less happy.

As far as I'm aware, there is no fundamental difference between the MK1 and MK2 'box apart from the dipstick deletion and that did not occur with MK1 to MK2 transition. My R plate MK2 has a dipstick.

Basically, if you reinitialise using a Lexia, it just gets on with the job of re-learning without necessarily caring about the precise specification of the egarbox internals.

Chris570 wrote: also, driving in snow mode, is that bad for the box to do it frequently?
No, snow mode is just another map...
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Post by citrov6 »

Thats not good then. i don't get wheel spin unless tires are cold, really only takes off around 2500rpm. The adaptive feels like it adjusts to throttle position so in traffic it i can move 1100-1500rpm and it still feels fully locked up, but if i floor it seems like a calculated increase up to 2500rpm at a slightly slower rate than the torque converter would naturally spin up. Gear changes feel fairly firm. All seat of the pants stuff not measured it but sounds like I should watch it from what has been said
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Post by CitroJim »

Yes, sadly Citro, it seems your 'box may be a little on the tired side. You have the two V6s so have you compared the two..

Yours definitely behaves nothing like all the ones I've experienced (five I think, at last count)

Point is, if you feel the 'box is a bit on the slippy side then NOW is a good time to rebuid it before any damage occurs.

My suspicion is it is low on oil pressure due to a pugging filter and a new filter, seals and TLC may be all it'll need to make it good again..

Leave it until it throws it's toys and it can be a different matter...
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Post by Stempy »

Sound like someone's touting for work :wink:
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Post by CitroJim »

Stempy wrote:Sound like someone's touting for work :wink:
In this weather :evil: My workshop is like Siberia at the moment...

:lol: :lol: :lol:
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Post by citrov6 »

Both of them do this, I will observe it more over the next few days. Maybe I am just thinking about it too much. I only really started to notice this after i drove my sisters 1.4 c3 which is obviously geared a bit lower and is a bit more responsive at lower speeds

Thanks for the heads up
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Post by Stempy »

When I had my old 2.0 VSX auto Xantia I found that the initial pick up on that seemed sharper than the V6 but only for about 10 yards......
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