Good evening, all. It was recently suggested to me that I take a look at the Ryephix supercharger bypass valve as a way to smooth out the throttle response in my April-'05 build MCS. A bit of Googling turned up the near-epic Operation Vacuum Gain System (VGS) thread. That thread contains a lot of good information, but I'm still (as something of a newbie) left asking "but so what?"

I love my MINI, but I am frustrated by generally poor performance below 4k RPM and a nasty spot of surging and poor throttle response. I *think* this is the dreaded yo-yo, but I was also under the impression that that'd been solved by MINI before my car was built. Not that I'd be surprised if it wasn't, but anyway...

It would appear that this "vacuum gain system" (aka VGS) is one approach to solving this problem, correct? Is it also correct to assume that the Ryephix BPV attempts to solve the same problem? If so, are they compatible? Which is more effective?

Thanks in advance, and if this is an FAQ, maybe it should be in the howtos or made sticky? ;-)

 

bump

 

I think 15% may fix that poor performance under 4K that you have.

 

(As in a 15% smaller supercharger pulley.)

 

The reduction pulley wether it be 15,16,17,19 percent is still the biggest bang for the buck available for the mini.

 

Yeah, a -15% pulley is on the horizon, although I would prefer to rectify the yo-yo/gutlessness below 3k with a cheaper solution, so I can buy a harness, stickier tires, and more track time. :-)

 

seems this thread is touching on different issues, not all are related. If you just sense poor performance in general from 1K to e.g. 4K a reduced pulley will help for sure. If you sense a yo-yo or stumble around or between 3K-4K then a pulley (and other performance mods) might make it worse, or maybe long-term it gets worse regardless of the mods, dunno.
I felt the car was performing poorly in general from 1K to 4K and had a 16% pulley, Milltek and Unichip installed and even though performance improved greatly my 05 MCS now has the stumble, BIG TIME. It's very irritating, extremely annoying at half throttle. The car just hesitates all the time around those rpm. WOT no problem. With Unichip removed it still does it, so it's not 'that' mod. Today I bought the parts for the VGS and plan to install them tomorrow. Hope this improves things...

 

The RPII makes the bypass close earlier, and not open as much. Personally, I'd use it if I were on the track all the time, it's aggressive. The VGS SHOULD help the yo-yo, but I can tell you that if you have stumble bad, it will probably be there with the VGS as well.
Personally, I streatched the stock spring a bit, and did the VGS. Not as aggressive at tip in as RPII, but I'm happy. I found the RPII to make very light throttle driving a bit harder...

But that's just me.

Matt

 

What do you mean by "aggressive"? Do you get more abrupt throttle response?

 

I have both Andy's VGS and DetroitTuned bypass valve.

I started by doing the VGS mod, which helped a lot with throttle response and smoothness. It was a very nice upgrade and it cost less than 10$. You can also do it by yourself, it's very easy to do and Andy's how-to is very usefull!

About 2 months later, I went with the DetroitTuned bypass valve. It knew I had a bad stock bypass valve, that was leaking from everywhere! I chose DetroitTuned bpv because it was adjusted properly from them, and it had a stiffer return spring. This mod has "released" a lot of lost HP on my car... It felt like a completely different car, but remember that my stock bpv was un-adjested for a long time. The boost seems to come on much more sooner than ever before.

Many people think that those 2 mods can have a pretty bad effect on fuel consumption (anything from 7-8% to 15% loss) but my MCS still has some very good numbers... I still get 480-500km per tank and from 8L/100km (highway) to 12L/100km (city).

I'd say you should first try the VGS mod, since it's lot cheaper. If you still feel flatspots on RPM, or Yo-Yo effects, then get the DT bpv, or adjust your stock bpv.

We are not a whole lot of people with both the VGS and BPV mod, but the very few of us are pretty much satisfied, and try to spread the good news! lol

 

Good work Number 2, or should I say DarkMiniCooperS. As you know, I also have both. I started the other way around. I started with RP#2 and months later did VGS. The combination is great. Yet, so few people have done it.

If you do not want to do RP#2, you can still try to adjust your BPV to close properly. Unlike the TB, the BPV should be able to close completely. If you are close to a dealership, go the parts department and just look at their samples, to be sure they close properly. Place your eye into the opening of the BPV and look at a light. If any light passes by the butterfly, it does not close properly. Look at the next sample. The part costs $38 or around that. Best thing to do for the MINI, since it will allow you to get the most of your mods.

Bomboasy
Number 1

 

lol I guess I'll have to get a new username, Number 2.

 

So the compramise I made was to stretch the stock spring a bit when I put the bypass back together.

Matt

 

Mine's already abrupt at light throttle. :-)

I did the VGS mod last night. I only lost a little bit of skin, and contained the 3rd degree burns to just a couple of fingers. Not bad, in all...

I just drove it around the block last night, and I'm not sure I see much difference at this point, but the yo-yo wasn't *always* horribly noticeable. It's actually been running quite a bit better now that the temps are cooler... I'll do a write-up with a couple of helpful hints soon.

 

So, on this thread I'm number 3 (003). I added the by pass valve today to my 2 month old VGS--now it's smooth and "the ol' butt dyno" says it's a little "thicker" in the mid range (my old hifi days showing through.) I'd say overall a worthy mod over my original spec. car. There's certainly daylight to be seen through my old by pass valve, but not as bad as I had imagined.

cheers,