New S4 Tuning

[18ME]

I realise the RX8 doesn't have a turbo (as I've got one in 10 days time), I was refering to my Audi is a pain with its turbo.

[Dippy]

It just goes to show how crap a measure bhp per litre really is.

I'll say this one last time. Performance is all about torque curve and not peak power.

I do believe that AmD got over 400bhp out of the car. So what? Let's see its torque curve before we decide how good it is...

[JamesB]

I totally agree about bhp being an inadequate measure of performance (although bhp per tonne is surely way better than bhp per litre). But I can't help feeling that increasing max bhp from 344 to over 400 (if true [img]images/graemlins/tongue.gif[/img]) would have a fairly substantial effect on torque. Either it is going to increase peak torque, meaning good gear selection will improve performance, or it will flatten out the "after peak" torque curve a bit, improving performance across the rev range.

Come what may, until someone comes across an authentic curve [img]images/graemlins/sekret.gif[/img], we're not going to know. [img]images/graemlins/s4addict.gif[/img]

[Joshie]

The BHP per litre figures were just my way of explaining why I felt that 400 BHP from the 4.2 was aparently ambitious (although as I said I reserve judgement for the time being). I never suggested that BHP per litre was a measure of performance and I agree with Dippy that torque (but not just a peak figure in isolation) relative to the weight of the car is a more accurate measure of performance. Have a look at EVO or a similar publication. pick some cars at random then analyse the quoted torque relative to the weight and performance - makes interesting reading.

[JamesB]

I only mentioned bhp per litre myself as it has been used as a comparator in the thread. And I think it can be a useful way of comparing the performance of the engine in isolation and possibly putting a reality check on some of the more ambitious claims. [img]images/graemlins/3flypigs.gif[/img]

I think we all agree, really. When you look at the torque curve and know the weight, you have a better idea than any bhp measurements.

Although I'd still like to know your thoughts on what the quoted increase in peak bhp might do to the torque curve of a NA engine. Or is it more important to know the areas where the remapping has an effect?

[Dippy]

There are 2 ways that torque has been increased: Free-flow exhaust and remap.

The exhaust reduces losses due to back-pressure. However this is mostly significant only at the top end, after the torque peak. Therefore often a free-flow exhaust will increase peak power without increasing peak torque. Sometimes it can actually lower peak torque!

What the remap does is dependant on what parameters can be changed. AFAIK the fuelling and ignition timing are the key ones to change. However the fundamental difference between a NA and turbo car is that you can't actually increase the air mass in the cylinders and therefore there is a limit to how adding more fuel can increase torque.

What I expect is that the OEM map is already fairly optimised for the peak torque. However in the rest of the range it may be compromised for greater fuel efficiency and less pollution. Therefore it would still not surprise me if there is only a marginal increase in peak torque from a remap. Again most of the gain would be at the top end, and hence why peak power can be increased.

The torque curve of an NA is much more triangular than that of a turbo car, and usually peaks higher in the rev range. Basic tuning won't change this, it will just alter the angles of the triangle.

As always, this is just MO.

[S4_SAT]

It ain't that hard.Audi got 360bhp from the 4.2 for the s8 in a relatively moderate state of tune.And the first 4.2s had 280bhp when it was in the v8.Thats nearly a 100bhp increase without significantly altering the way it drives apart fron the fact that the s8 has more power higher in the rev range.Ferarri are managing to get over 400bhp from a 3.6 litre v8 so 400-420bhp isn't that unimaginable.

[Golich]

Still no confirmation from AMD then?

[BlackS4V8AVANT]

Hi All,

First post so here goes.



I have a Black Avant with silver silk Nappa and every concievable extra including full roadpilot with raydar and jammers front and rear. I paid 1% off list whick I all in with the full Miltek system and the supposed 415+ BHP came to £55K ish.

It actually made 391bhp on two independent tests.

I am not happy as you would imagine.

I have some news though, I have been talking to MTM in Germany and they are working on a Supercharger kit to add antother 100 - 120 BHP. Needless to say I have pre-ordered it as 500 BHP sounds like the perfect amount for the car.

The car as is

I love it, a great cruiser for those long journeys but it certainly can be hustled on the a/b roads also. The grip is good and the handling is also excellent.

I ran it at Santa Pod a while ago against a mates 03 M3 and it pulled away easily. (Great News there then) I ran a best time of 13.56 but it was a very hot and it feels quicker when its cold outside.

I will report back when the new Supercharger arrives and post Dyno charts and any figures I have.

Cheers

Andrew

PS. It does sound Fabulous!! like a TVR saloon. [img]images/graemlins/audiS4black.gif[/img]

[wazza]

Welcome to RS246 Andrew [img]images/graemlins/thumbs.gif[/img]
Nice to see these new owners here.

came to £55K ish.

OMFG [img]images/graemlins/blush.gif[/img]

Supercharger sounds interesting.....
Even so 391bhp is not a bad car. What does it feel like over standard? Have you driven the old S4?

[Dippy]

Hi Andrew.

Yes the supercharger sounds interesting. How much have MTM quoted for the kit?

Also what about torque? I don't know a lot about superchargers except that they 'cost' some torque by the fact that they are direct driven by the engine. Have you got any more technical info?

[BlackS4V8AVANT]

Hi BiTurbo and Dippy


Indeed I have driven the old version, I had an X Plate saloon. The new one is definately quicker than both my old one and the standard new S4 one.
It does pull very well although I have noticed that the ambient temp is really an issue. It feels a good 25bhp more in this cold weather!!!

The main difference between mine and a standard one is noticable when you are sprinting away from standstill, on mine the DSP slaps your wrists in the first three gears! Needless to say it stays off most onf the time, about this, I have been told you can have it off at default on start up, does anyone know how?

FYI MTM are quoting roughly 3-4K for the supercharger converson and yes Dippy you are correct about the torque, It only costs about 2% however, at least thats what I have found on Yank V-8's in the past.

Cheers


Andrew[img]images/graemlins/audiS4black.gif[/img]

P.S Just got Confirmation from my Audi dealer, my order for the Le Mans has been accepted by Audi UK so I should be one of the first.... [img]images/graemlins/biggrin3.gif[/img]

[Golich]

Welcome to the site [img]images/graemlins/thumb.gif[/img]

It actually made 391bhp on two independent tests.

I am not happy as you would imagine.

What did AMD have to say about that?

Ooo the supercharger option sounds very interesting [img]images/graemlins/jump_clap.gif[/img]

[BlackS4V8AVANT]

Hi Guys - Quick update.


AMD have had the car back and had another go!!!

Result is 406BHP verified on an independant RR and 392ib torque.

A bit better me thinks, it may actually hit 415 once its done 10k?


Still no news on Supercharger, I live in hope.

Have a good Christmas one and all [img]images/graemlins/laugh.gif[/img]
Andrew [img]images/graemlins/audiS4black.gif[/img]

[Joshie]

I ran it at Santa Pod a while ago against a mates 03 M3 and it pulled away easily. (Great News there then) I ran a best time of 13.56 but it was a very hot and it feels quicker when its cold outside.

Interesting what you say about Santa Pod. The times posted normally by M3's there is 13.3S standing quarter so I think your mate had a bad start otherwise he'd have beaten you [img]images/graemlins/tongue.gif[/img]

Can you let me know which independent rollong road you used too.

Thanks