VSR Explained?

[Madjackal 0]

Always keen to educate myself and intigued to learn how the VSR does what it does I was pleased to find this untill I read it and realised it makes very little sense to me, anyone fancy tackling this one? Lamens terms anywhere between 'makes the car go faster' and the following; (some points for clarification are highlighted)

 

 

Limited by the transverse mounting of the engine, there isn't much room for generous inlet manifolding. In order to achieve a good compromise between maximum power output, and adequate torque in day to day use, the inlet manifold runs across the top of the head. This has circumvented the shortage of space and allowed the use of an oscillating-flow tuned inlet manifold. Each cylinder has its own inlet tract that is tuned to such a length as to ensure positive inlet pressure. As engine output is proportional to the airflow, this scheme means that the VR6 doesn't have to be ashamed in the face of competitors. The 2.8 litre produces 174 PS [DIN hp] and a maximum torque of 240 Nm at 4200 RPM, and the 2.9 litre

engine in the Corrado achieves 245 Nm at the same engine speed. But this achievement wasn't enough to satisfy the Wolfsburg developers. To achieve even more torque, lower down in the rev range, the 6 cylinders were to breathe even more freely. The idea of the variable inlet manifold [ german "variables Saugrohr" ] was born and developed in parallel with the now standard version, with assistance from the Pierburg GmbH in Neuss, a company which has a high reputation with things relating to mixture control. The VSR [ abbreviated from the

german ] system did not go into, falling victim to the red pens of accountants shortly before the VR6 started production. That this piece of motor technology was not condemned to the depths of the Wolfsburg catacombs, is thanks to the interests of Volkswagen Motorsport, based in Hannover. This VW company took the VSR and now offers it as an after-

market conversion kit for 2888 Marks. The kit may be fitted to all VR6s with 2.8 and 2.9 litre engines.

 

Even though the VSR achieves similar aims to those of the switching inlet manifold of the 2.8 litre V6s from Audi, the operating principle is different. In the Audi engine, a long, narrow inlet tract achieves high torque at low revs; 245 Nm at 3000 RPM. The maximum power is

achieved using a short, wide inlet tract, producing 174 PS at 5500 RPM.

For the engine to be fed through the appropriate channels, depending on engine speed, inlet manifolds are switched using six individual, vacuum operated flaps at 4000 RPM. In both stages, the technology is based

purely on tuned oscillating-flow inlet manifolds, with the necessary switching.

 

The VSR in contrast, two diverse technologies are applied. It is designed so that at low engine speeds, resonance is used to improve cylinder charging efficiency -- at higher RPM, oscillation- tuned,

individual, broad tracts are used. Switching from one to the other is achived by a single flap, also vaccuum operated at 4000 RPM. The tuned inlet tract operates by the low pressure caused between the throttle valve and the inlet valve, by the suction of the descending piston,

Through inertia of the air in the tract, the airflow tends to keep moving towards the inlet, even after it's closed, causing a slight over-pressure when the inlet valve next opens. This ensures high charge efficiency even during early stages of the induction stroke. Of course, further during the same stroke, inlet pressure falls followed by a high pressure but not before the inlet valve closes.

 

In order to achieve optimal control of the oscillation and reflection of the column of air in the inlet tract, it needs to be closely coordinated with valve timing, but this is not possible due to variation in engine

speedWhy not?. Even at mid-range-rpm, the valve opening and the are out of synch. The second pressure wave arrives much too early before the inlet valve closes and a backflow reduces fill efficiency. Now to achieve high torque under these conditions, resonance-fill is utilised. This is done by closing the connection flap between a small resonance chamber which is immediately before short inlet tracts above the inlet valves. This transforms the 6 cylinder ending into effectively two 3 cylinder engines

with uniform firing times, and which do not have overlapping inlet strokes. Resonance pulses of up to 0.4 bar [approx 6 psi] above atmospheric are achieved, leading to remarkable fill efficiency and torque increases.

 

Even though fitting the VSR requires not great skills, it should be undertaken by a professional with the right tools. For example, fitting the new EPROM and the new control harness requires dexterity and special tools. The new chip doesn't alter the previously-programmed behaviour of the engine management, it only adds an additional control output for the electrically- controlled, vacuum operated flap. The kit includes

instructions as to complete installion, including connections to the vaccum circuit and electrical connections.

 

Further engine modifications are not required, so one is permitted to anticipate the VSR transformation. A marked improvement in torque at mid-range is advertised with 255 Nm available at 3600 RPM on the 2.8 litre engine. This corresponds to an 11% increase at that engine speed.

In the 2.9 litre incarnation, 260 Nm is available, providing more performance in the most-used rev range. There is no promise of more power in the higher RPM range.

 

To illustrate the performance improvement in a VSR Golf, one doesn't need any test equipment! Almost right from the start, at below 3000 RPM, a new urge is sensed. Up to 4000 RPM the engine provides markedly better acceleration, yet above, the previously expected manners appear because the torque curve corresponds to that of the standard engine. Even more!

After the impetuous acceleration, the switchover feels almost reserved.

The steeply increasing torque curve up to 3600 RPM also shows a rapid fall back to the norm between 3600 and 4000 RPM. The torque improvement is an excellent fit to the Golf VR6.

 

In fourth gear, the torque boost corresponds to 90 to 120 kmh, in fifth to 110 to 150 kmh. This turns the Golf into a sprinter, that none of the near-200 PS professionally tuned chariots comes near. Testign showed

that acceleration from 90 to 120 kmh in fourth gear only took 5.4 seconds. The standard VR6 Golf took 6.1 seconds and a near-200 PS Oettinger VR6 Golf taking 6.4 seconds, and a Wendland special taking 6.2 seconds. No wonder because their maximum torque happens at much higher

RPM.

 

Unremarkably, the VSR trick didn't improve peak acceleration or top speed, both of these being exclusively in the higher rev range.

 

The VR6 opens up a new field for Volkswagen Motorsport tuning. This is appropriate when one expects high torque for comfortable and sporty driving. It's even more attractive because testing showed reduced fuel

consumption by half a litre [ per 100 km ]. On the other hand, the VSR offers professional tuners an innovative platform for development - as some of them have already indicated.

[big_chris1981 0]

it sounds like theyre saying that it will improve low down response and mid range torque,,,and make the cars acceleration a litle faster, but onyl below 4000rpm?

[Madjackal 0]

Yeah, i mean i understand that more air means more fuel and therefore bigger bang.

 

I just struggle to understand how different types of air flow actually affect performance when it comes to numbers and better acceleration across the range, I for instance just bought a BMC CDA and it seems to have given me more power but it still all comes in a big lump at around 3.5 - 4k. I have heard that attaching the cold air feed helps to bring the power in lower down the rev range, whether true or false I dont know but is it the colder air or the longer inlet tract?? So many variables!!

[PhatVR6 0]

it uses the pulses from the induction of the other cylsinders to draw air into the surrounding cylinders, in a scavenging effect, thus drawing in more air than would be possible with a normal manifold.

 

amazingly clevr, and makes a massive difference on a VR, but for the same money they go for you can buy a complete 24v motor, which comes with a VGI too......

[gg7aph 0]

Wakey-Wakey....time to open this old thread back up!

Since sorting out my ISV and MAF problems and having nothing else to distract me with I'm noticing that just like some of the other posts here I get a massive 'dump' of power around 3750 - 4000 rpms. As the description details the VR6 produces it max torque output at this level. However, I it feels really 'flat' under 3750rpm and wonder if there isn't something I can do to improve low down performance?

Installing a VSR sounds a little severe, mostly to my wallet through initial costs but then also additional fuel consumption, right? Anything else I can try?

[dukest 0]

your wallet is there to be punished..! the fact that you're posting in this thread means that you know you want one really! :D

[Taggart 0]

You won't use more fuel, in fact a lot of people find use less as you tend not to need to rag the hell out of the engine so much.

[dinkus 10]

On a VR you've got 3 tuning options:

 

Shrick/VSR VGI

Shrick 268 or similar cams (not sure if it's worth doing until you've done the inlet)

Forced induction

 

F/I is by far the best 'bang for your buck' as it were, but a VGI and set of cams is slightly less mental option (but probably no cheaper than a supercharger).

 

Failing that, go buy yourself a 2.8 24v for a few hundred quid and chuck that in instead.

[tonedef 8]

your wallet is there to be punished..! the fact that you're posting in this thread means that you know you want one really! :D

It doesn't take too much punishment, I picked up a Schrick VGI from German ebay for under £750 inc postage, fitted it myself and did an ECU reset jobbie. There was a bit of pinking on the first full throttle run and nothing after that, seems a reasonable price to pay to me. There's been a few for sale on here recently, get one bought and make yourself happy!

 

You won't use more fuel, in fact a lot of people find use less as you tend not to need to rag the hell out of the engine so much.

Hmm, maybe after the honeymoon period, for now I use as much if not more :lol:

 

I'll be sticking a set of cams in next and then maybe it really should be remap time.

[Goldie 2]

Im at the Schrick + Cams + Enlarged TB + BMC stage and the car is so much more drivable (and vocal)..

 

Im certainly not ruling out chargers or maybe engine conversions in the future and at the end of the day im not likely to have lost much money on the goodies that are under the bonnet at the moment..

 

My petrol consumption is similar to before TBH...

[Taggart 0]

Going back to standard mani, I definitely use more petrol on the std mani.

 

Different driving styles I guess...

[dr_mat 0]

It's a bit much to claim that a VSR/VGI is "probably no cheaper than F/I" .. the cheapest supercharger setup will set you back a fair amount more than the VSR/VGI setup (which on some cars is a straight fit-and-forget). Add £250 for a remap and you're laughing. Of course, if you're up for doing your own fitting on a supercharger then yes, you'll get a lot more oomph for a little more cash, but you'll still have sluggish response below 3500 rpm .. If you have to pay someone to fit it, it'll cost ya a whole lot more.

 

As for fuel economy, the reason it can actually be improved is simple: if the car pulls hard from lower revs you're less likely to go to higher revs .. and it's revs that cost you fuel, not engine torque output. (6000 rpm times six cylinders is 50% more fuel than 4000 rpm times six cylinders isn't it!)

 

The science bit.

 

As for the science bit .. well when they're talking about resonance, consider that the air moving through the inlet manifold has *inertia*. Once it starts moving, it wants to carry on moving, and if it stops moving, it wants to stay stopped. Imagine waves of pressure bouncing around inside the inlet. Moving air hits a closed inlet valve, it will bounce back slightly. The VSR is tuned to bounce these waves around for just the right amount of time so that the next wave arrives back at the inlet valve *just* as the valve opens, so the increased pressure causes the air to move into the cylinder more efficiently at that moment.

 

The standard manifold does not, so it allows these waves to dissipate, so when the valve opens it just has normal atmospheric pressure behind it, which doesn't assist with filling the cylinder very much at all - you're relying on the -ve pressure caused by the piston dropping away to encourage it - but again, the air has inertia, it's stopped and it takes time before it starts to flow again.

 

The standard inlet works well at high revs because the higher air flow at high revs means that there is always enough inertia in the air to keep the pressure up at the inlet valve - resonance is not required.

[boost monkey 0]

*gets excited about an engineering thread*

 

Oh, Dr Mat beat me to it :(

 

Uh yeah...what he said ^^^

 

*sulks and wanders off*

[dr_mat 0]

Sorry .. :)

[boost monkey 0]

lol, no prob. I had seen it all morning and never got around to posting!

[gg7aph 0]

STOP IT! ALL OF YOU!

I spoke to my wallet and she told me that I can't afford to to go about spending 750 quid on german ebay parts...no matter how much I want to. I'll have to wait until christmas and be a very good boy. Now, although I'm very pleased I've learned something new today, and started off this heated debate, my original question remains:

What can I do (Other than fitting a VSR or F/I) to improve my low-down rev torque?...CHEAPLY!

[Toad 0]

What can I do (Other than fitting a VSR or F/I) to improve my low-down rev torque?...CHEAPLY!

 

I don't think you can to be honest...

[dinkus 10]

What can I do (Other than fitting a VSR or F/I) to improve my low-down rev torque?...CHEAPLY!

 

I don't think you can to be honest...

 

Aye. But I guess if you want cheap, you could strip the interior out apart from the driver's seat - that'd save a fair amount of weight and make things a bit more spritely :lol:

[Goldie 2]

STOP IT! ALL OF YOU!

What can I do (Other than fitting a VSR or F/I) to improve my low-down rev torque?...CHEAPLY!

 

Other than what dinkus has suggested and stripping your car out there isnt really anything you can do..

 

Mods such as induction kits arent gonna do anything on their own apart from make your car sound pretty....

[boost monkey 0]

I spoke to my wallet

 

Oooh boy, that's where you went wrong.... :lol:

 

What can I do to improve my low-down rev torque?...CHEAPLY!

 

 

Cos I'm a nice guy, I'll swap you my 1.8 8v for your VR6, then when we swap back your Corrado will feel like a rocket ship. Woo!

[tonedef 8]

What can I do (Other than fitting a VSR or F/I) to improve my low-down rev torque?...CHEAPLY!

You could try a set of plugs and always make sure you fill up with super unleaded, apart from that cheaply and VR6 tuning rarely occur in the same sentence I'm afraid :(

[boost monkey 0]

Take the rear bench out and empty your boot...? :?

[Kevin Bacon 5]

Shorten the final drive ratio?

 

The obvious is always overlooked when considering ways to improve acceleration :lol:

 

The 3.68 final drive is in the top 5 "Best things I did to my Corrado" annual.....

 

But you always get your tight fisted types worrying about a 1mpg reduction in economy 70mph.... It's a VR6 and you want to mod....feck economy! Buy a bloomin Prius if economy is a concern!

 

So if you're needing a clutch, drop the box and fit a quaife and 3.68..... do more with the power you've got!

[corozin 0]

If you want 300bhp cheaply, buy an Impreza...

[Uzi85_VR6 0]

Shorten the final drive ratio?

 

The obvious is always overlooked when considering ways to improve acceleration :lol:

 

The 3.68 final drive is in the top 5 "Best things I did to my Corrado" annual.....

 

But you always get your tight fisted types worrying about a 1mpg reduction in economy 70mph.... It's a VR6 and you want to mod....feck economy! Buy a bloomin Prius if economy is a concern!

 

So if you're needing a clutch, drop the box and fit a quaife and 3.68..... do more with the power you've got!

i thought a quafie was from harry potter, that ball from quidditch?