VSR vs VGI??

[LicklePaulie 0]

Took my VR6 to Cadwell Park on her maiden voyage last week. Got the handling sorted proper but found that my 205bhp takes way too long to arrive. I understand that a VSR manifold will lower the point at which peak torque arrives but don't really know much about what the VGI does.

 

Could somebody offer up an idiot's guide to the differences and pros and cons of each type of manifold compared to the OEM version? Similarly, does anyone have any other advice regarding the above issue? Many thanks in advance...

[Kevin Bacon 5]

If you want the grunt to come in earlier, lower the gearing! And besides, the car is a totally different experience on a track. You don't get the same sensation of speed and acceleration.....

 

Anyway, as discussed numerous times already....

 

Shrick = hits VR bonnet, tuned length inlet runners, OBD1 and 2 compatible, manifold has to come off to change plugs.

 

VSR = Doesn't hit VR bonnet, untuned runners, OBD1 only, manifold does not have to come off for plug change and only 500 were made.

 

Both give around 10bhp at the top and move the peak torque to about 3500, with a bit more added on for good measure, depending on engine.

 

K

[dr_mat 0]

Hmm, not sure if this has been done to death or not, but..

VSR is the WV Motorsport (/Pierburg) originally developed variable inlet manifold. yes, much more torque below 4000rpm than the standard manifold, and "normal" performance above 4000 rpm.

VGI is the Schrick aftermarket version of the same product. It has a few subtle differences, and is said to give slightly more torque and more flow at high revs than the VSR, but I've never seen a VSR vs VGI plot on the same engine so can't really say whether you'd notice the difference.

 

The biggests pro for the VSR is it's "VW"-ness it's a really nice fit for the car, it's identical in size to the original manifold and allows you access to the spark plug holes in the same way as the OE manifold.

 

The VGI, on the other hand, blocks off the front three plugs access points, and is physically larger than the original, resulting in less space under the bonnet, and the necessity to rework a part of the bonnet to get it into a Corrado. Not only this but it pulls the throttle body further away from the engine, which pulls the air intake box away from it's housing. (I discovered this this weekend, and wonder if that's got something to do with the sitting-in-traffic heatsoak..)

[dr_mat 0]

...all of which is more or less what Kev said... (more, mostly.. ;) )

[Kevin Bacon 5]

. Not only this but it pulls the throttle body further away from the engine, which pulls the air intake box away from it's housing. (I discovered this this weekend, and wonder if that's got something to do with the sitting-in-traffic heatsoak..)

 

Yeah it does pull the airbox away from it's inlet, very annoying! That is why I junked the cr@ppy rigid inlet hose and replaced it with the far superior (and infinitely more flexible) moulded rubber intake from pre-93 VRs. A damn good purchase for a tenner that was as it's able to adjust to the TB's new position without yanking the airbox away from it's inlet everytime you step on the gas.

[dr_mat 0]

Must do something similar...

[LicklePaulie 0]

Thanks for the quick responses. Feeling a bit :oops: :oops: :oops: cos I've just come across a thread that covers this precise subject.

 

Kevhaywire, I realise the differences between driving on road and track and my comments are based on that experience. I offer the following example of lack of torque - by the end of the start/finish straight my VR was reaching 97mph (obviously with more to come but not the room to reach it) whilst my mate's standard 92 Prelude (running 196bhp) was reaching 110mph at the same point - though I was carrying more speed through the next three bends and was killing him down Park Straight! I MUST get that peak torque point lower into the rev-range... :twisted:

 

Thanks for the info on the airbox. I am, however, running a GruppeM ram charger so shouldn't have too much trouble with fitment/refitment as I've already put in a length of flexible hosing anyways.

 

Final question though. I'm running a 94 (late version) VR; I assume that this means I'm running OBD1 and so precludes the use of VSR?

[dr_mat 0]

Nope, all Corrados are OBD1, the VSR is OBD1 only, the VGI is available in either.

As for your track experience, why not just change down...? 96 should be top of 3rd gear, drop it into 4th you're right back on the boil.

[LicklePaulie 0]

Thank you very much Dr Mat :) . Got to sort out some finances now :roll: . As for gear-changes, you're quite right that speed was high-third/mid-fourth - this was after a whole day of open pit-lane (trying all sorts of gear combinations). Had a really good day actually, got the H&Rs set up properly (eventually), gave the Brembos a real testing, and found that gears were very long-legged. Pretty much thought that VSR/VGI would be more suitable (as well as affordable!) mod than 6-speed box. I did find the lack of lsd to be less of a hindrance than I expected - but it did stay dry all day :wink: .

 

Anyway, thanks to you both for the advice - will have a long hard look at my next move.

[dr_mat 0]

Hmm - there's a wide enough torque curve to keep the engine on the boil, but admittedly due to the tall gearing slow corners are a problem, and there's not a lot of overlap on the gear selection (yes you have to change gear mid corner on the fast sweepers sometimes). I suspect it's 50/50 gearbox or VSR. The VSR will give you more flexibility to stick with a gear rather than change down, but then a 6-speed g/box conversion would give you the ability to select a more suitable gear for every corner. And the pricing is about the same, from what I've heard.

(A new VGI is going to set you back £1200+, whilst the gearbox mod is probably similar.)

[dr_mat 0]

IMHO most people looking at that kind of money for a track car are looking at spending slightly more and getting into turbo/super charging, I would have thought that's a better bet. Flexibility isn't so important on the track, it's outright power at high revs that's required...

[Kevin Bacon 5]

Yeah the VR's gearing is a tad tall for a short track. It is the 'touring' Corrado after all :lol:

 

Dropping the diff down to a 3.61 (if keeping it 5 speed) would be a good compromise for road and track use. Or a 3.94 diff with 6 speed even better......

 

I like the leggy gearing for road use but I would definitely feel it was a hinderance on a short, twisty track. As I'm not into track days, it's not an issue for me :lol:

 

Well, I would love to get into track days but not with the Corrado and I can't afford 2 cars :x

[LicklePaulie 0]

IMHO most people looking at that kind of money for a track car are looking at spending slightly more and getting into turbo/super charging, I would have thought that's a better bet.

Wanted to stay NA rather than go Forced Induction - I've also heard that s/c is great for road use and short bursts but can cause problems over longer periods of pressurised use.

Flexibility isn't so important on the track, it's outright power at high revs that's required...

I couldn't disagree with you more on that one. Power is no use at all if you can't get to it, and on the track I want as much flexibility as I can get.

[Guest]

I have tracked the same car with and without a VSR. The VSR makes its biggest gains between 2000-4000RPM, peaking around 3500RPM. In my experience, it only comes into play when leaving the pit lane - it's useless thereafter. I'd suggest that unless it's a very tight hairpin, if you drop below 3500RPM on track, you're in the wrong gear.

 

Work out & stick to your shift points, keeping the area under the curve at its maximum. My VR6 is primarily a track car and I am not buying another VSR for it. You'd be better off putting money towards gearing or 3500+RPM output gains.

[Kevin Bacon 5]

Exactly, which is why Stealth advise potential VSR customers not to bother if they spend half their time in the upper rev range. You may aswell spend the money on 268 cams, bigger throttle and a rechip instead. But the whole lot together is a good package though, if a little on the expensive side.

 

The VSR is primarily for making better use of the engine's torque, i.e. 1000rpm lower down, for a more relaxed drive on the road. That is to say making good progress without having to row the gearbox.

[LicklePaulie 0]

Hmmm. Plenty of food for thought there guys, thank you all v. much for your input. Looks like I'm gonna have to talk to Vince about a 6-speed box (might as well grab an lsd while I'm at it!).