Performance worse with new DVs.

[DJG]

Mentioned this before, but thought I would give it its own thread.

Had my S4 checked out at AMD last week. They found that one of the DVs had a torn diaphragm and in fact had become disconnected from the hose which had become brittle [img]images/graemlins/confused.gif[/img]

Not surprisingly they would not RR it like that so they swapped the DVs for new Bosch items and changed the vacuum hoses too.

Then they put the car on the RR and measured 271BHP and 329lbft.

Left AMD a happy bunny.

Very pleased to notice that the throttle response at low revs/throttle openings was much smoother.

However when I tried a few 6th gear 50-70s found that the car was now approx .5s slower (6.5/6.6s instead of the 6.0/6.2s I used to get (and others get)).

Hoped it was the fact it was a hot day, but its not that ( [img]images/graemlins/thumbs.gif[/img] Dippy).

Maybe the new Bosch DVs are just slower to react, but surely having a leaking and possibly disconnected DV wouldn't make the car perform better!

Very strange. Was expecting the throttle response to get better, not worse. Power output is OK too!

Any thoughts anyone....

[Dippy]

David,

Do your TBA just to be sure.

(use VAG-COM or reboot the ECU, but make sure you don't touch the pedals).

Can you either scan in your torque plot or let me know its values every 100 rpm between 1800rpm and peak. I should be able to tell if the engine's OK from that.

Dave

[DJG]

Thanks Dave,

Had a brief look at the "before" curve on the AMD site and it appeared OK.

Scanner here is not working, so:

RPM lbft
2300 280
2400 298
2500 318
2600 330
2700 328
2800 325
2900 325
3000 320
3100 318
3200 318
3300 326
3400 312
3500 310
4000 300
4500 285
5000 285
5500 255
6000 235
6300 215

My plot started at 2300. Sorry if the numbers look backwards, something to do with being left handed. [img]images/graemlins/wink.gif[/img]

David

[Dippy]

David,

Actually it's the earlier part of the rev range I needed, as any problems with turbo 'spool-up' would result in lag, such that torque is lower than it should be from 1800 revs. Nevertheless your curve does look good, suggesting that there really is nothing wrong with the engine.

What happens after a quick gear change? Do you feel a real lag before the torque comes back in? If so, then if the rest of the performance seems smooth, then I can't help but blame the DVs.

If you want to meet up then I could take a closer look...

[Blueone]

Hmm just read this post

I had new DVs fitted 2 weeks ago and so far I am disappointed - engine feels as if it is holding back somehow.

Does not feel as fast.

Thought that the ECU needed time to adjust.

Is this possible??

[DJG]

Dave,

Yes it's a pity AMD didn't measure any data before 2300RPM.

Did a bit of testing on my way to work this morning and don't appear to be suffering excessive lag when changing gear briskly.

Overall the car is driving well and smoother than before.

Just a bit slower to spool up [img]images/graemlins/frown.gif[/img]

Haven't tried the TBA yet.

Arrived home last night to find the dishwasher full of water, so that was my evening... Didn't manage to fix it either (think it needs a new pump) and guess what...it is one month out of warranty. [img]images/graemlins/confused.gif[/img]

Might like to take you up on your generous offer to have a look (S4 not dishwasher!)

[img]images/graemlins/beerchug.gif[/img]

David

[DJG]

Irritating isn't it.

If yours is like mine it is smoother, but a bit slower accelerating from steady speeds.

Wouldn't have thought that the ECU would need time to adapt. I have done a couple of hundred miles anyway.

Dippy did suggest carrying out a TBA (Throttle Body Adaption I believe, correction Alignment), but I think this just something that is relatively easy to do which could possibly help rather than the likely problem (did that make sense....)

David

[DJG]

Met up with Dippy last night ( [img]images/graemlins/beerchug.gif[/img] Dave).

We had a poke around my DVs and turbo pipes and a quick blat up the road.

So what did we conclude.

Well Dave's car is:

Faster than mine
Handles better
Stops better

[img]images/graemlins/thumbs.gif[/img] AMD

But we couldn't find anything wrong with mine and apart from the above ( [img]images/graemlins/thumb.gif[/img]) it appears to go alright for a standard car.

In isolation everything appears fine, just a bit slower against the stop watch on roll-on acceleration compared to how it was.

Odd [img]images/graemlins/confused.gif[/img]

[Golich]

Sorry to change the subject but since you tried Dippy's car What is your impression of the H&R coilovers compared to your stock suspension?

[Dippy]

Before David gives you his impression, I can tell you that a ride in his standard S4 reminded me how soft the suspension is! When I went round the roundabouts in my car (faster than David went), I got tyre squeal but the car stuck to the road. When David went round slower, I really felt the body roll, and knew that he couldn't turn as fast as my car without risking understeer.

In summary I really recommend the H&R coilovers, they are still probably the best modification I had done.

Cheers,
Dave

P.S. We were still both driving like grannies in comparison to Bushy, JR etc. [img]images/graemlins/jump.gif[/img]

[DJG]

Patrick,

We both drove our own cars so the driver certainly makes a difference (and I really do drive like a granny!), but the difference was very apparent to me.

The standard S4 suspension is very soft and bouncy by comparison (certainly with my 53K shocks) and Dippy's car felt much more stable under hard cornering than mine. I'm sure my car would have gone round the corners faster than I was driving, but the excessive roll is not exactly confidence inspiring and makes it harder to feel what the tyres are doing.

The ride on the H&Rs also seemed perfectly comfortable from the passenger seat and didn't appear to be so stiff as to cause the car to bounce around bumpy corners (Unlike my old lowered Golf GTI Mk 1)

So [img]images/graemlins/thumb.gif[/img] from me for the H&Rs and they are probably the most impressive single improvement over the standard car.

Dippy's car is a very impressive complete package and a credit to him.

[img]images/graemlins/beerchug.gif[/img]

David

[Bushy]

Oi! gutted I missed a local meet

[Dippy]

It was a last-minute arrangement.

However we ought to organise an occasional Reading meet as there are a few of us in this area (although Carl doesn't seem to post here).

[DJG]

Sounds a good idea to me.

David

[Joshie]

It was a last-minute arrangement.

However we ought to organise an occasional Reading meet as there are a few of us in this area (although Carl doesn't seem to post here).

I'd be up for that myself.

When I met Dave in MK we had a chat but I feel we missed an opportunity to do some comparisons, particularly of the the suspension as Dave's has the full H&R setup.

Maybe soon, hopefully. [img]images/graemlins/thumbs.gif[/img]