How To Drivetrain :: Operation Vacuum Gain System (VGS)
#301
12-13-2005, 09:32 AM
6th Gear
Join Date: Apr 2004
Location: San Francisco Ca.
Posts: 1,179
Likes: 0
Received 0 Likes
on
0 Posts
#302
12-13-2005, 09:40 AM
6th Gear
Join Date: Apr 2004
Location: San Francisco Ca.
Posts: 1,179
Likes: 0
Received 0 Likes
on
0 Posts
#303
12-13-2005, 10:04 AM
Originally Posted by andy@ross-tech.com
{snip}...Personally, I can't stand the yo-yo feeling every time I switch back to stock.
Any minor adjustment I have had to make in driving style pales in comparison with the aggravation of the yo-yo. It is a joy to have my MCS display such smooth and even torque from about 2,800 rpm on up.
Do we know for a fact the there was a change in vacuum source for 2005? Anyone care to check their stock 2005/2006?
Theo
#304
12-13-2005, 12:21 PM
Originally Posted by Koopah
Ahmen, Brother!
Any minor adjustment I have had to make in driving style pales in comparison with the aggravation of the yo-yo. It is a joy to have my MCS display such smooth and even torque from about 2,800 rpm on up.
Do we know for a fact the there was a change in vacuum source for 2005? Anyone care to check their stock 2005/2006?
Theo
Any minor adjustment I have had to make in driving style pales in comparison with the aggravation of the yo-yo. It is a joy to have my MCS display such smooth and even torque from about 2,800 rpm on up.
Do we know for a fact the there was a change in vacuum source for 2005? Anyone care to check their stock 2005/2006?
Theo
Anybody?
#305
12-13-2005, 12:46 PM
3rd Gear
I just wanted to clarify that my 'issues' with the VGS were not a hard-and-fast reason not to do it, they were just issues that my driving style didn't jive with.
The main adjustment I wasn't able to make was to operate the clutch a whole lot faster. If you are quick with your shifts, then the lurching was much less pronounced when shifting... it was still an issue when coasting to a red-light or something.
I should also add that my 05 MCS hasn't really been plagued by much yo-yo'ing. I have noticed it only ever-so-slightly, but it never really bothered me. I also have an ALTA CAI and 15% pulley, so folks without these mods might interpret the VGS performance differently.
RM2K5
The main adjustment I wasn't able to make was to operate the clutch a whole lot faster. If you are quick with your shifts, then the lurching was much less pronounced when shifting... it was still an issue when coasting to a red-light or something.
I should also add that my 05 MCS hasn't really been plagued by much yo-yo'ing. I have noticed it only ever-so-slightly, but it never really bothered me. I also have an ALTA CAI and 15% pulley, so folks without these mods might interpret the VGS performance differently.
RM2K5
#306
12-20-2005, 06:27 AM
Originally Posted by RallyMINI2005
I had posted earlier that I had installed the VGS on my '05 MCS, and I wanted to update folks that I have also removed my VGS.
MY reasons were pretty simple: with the VGS the bypass valve stayed closed longer, and when shifting under high-load (accelerating hard, etc) the bypass valve would stay closed just a nano-second too long causing some wicked engine-braking effects. This had the effect of causing a big JERK in between shifts, which felt like it was going to break something.
I drove around for about 2 weeks with the VGS just to be sure, and indeed I noticed this behavior pretty often. Once the weather turned cold this effect got even worse, and it finally got bad enough I was worried about the tranny, so I ditched the VGS, and I have to say, I am very happy I did.
Also, my mileage was worse with VGS, I think because the supercharger was working more often... or because my right foot was. Not sure.
On a final note, there was always something about VGS that I couldn't really verify easily, but it always felt like the last little bit of "omph" was missing when on the highway... like if I REALLY wanted to pass a 18-wheeler or something. With VGS there just wasn't anything there, and now without there is a last little bit of accleration waiting waaay down at the bottom of the peddle, which is awesome.
Anyway, it was an easy mod, and I'm glad I did it...
RM2k5
MY reasons were pretty simple: with the VGS the bypass valve stayed closed longer, and when shifting under high-load (accelerating hard, etc) the bypass valve would stay closed just a nano-second too long causing some wicked engine-braking effects. This had the effect of causing a big JERK in between shifts, which felt like it was going to break something.
I drove around for about 2 weeks with the VGS just to be sure, and indeed I noticed this behavior pretty often. Once the weather turned cold this effect got even worse, and it finally got bad enough I was worried about the tranny, so I ditched the VGS, and I have to say, I am very happy I did.
Also, my mileage was worse with VGS, I think because the supercharger was working more often... or because my right foot was. Not sure.
On a final note, there was always something about VGS that I couldn't really verify easily, but it always felt like the last little bit of "omph" was missing when on the highway... like if I REALLY wanted to pass a 18-wheeler or something. With VGS there just wasn't anything there, and now without there is a last little bit of accleration waiting waaay down at the bottom of the peddle, which is awesome.
Anyway, it was an easy mod, and I'm glad I did it...
RM2k5
2 weeks? damn....I felt it the sec i took off after doing it and came right back and took it all off.
Andy and I both agree that this mod is very effective but at the same time, the motor mounts in these car are horrible and exhibit alot of movement during faster operations on the throttle.
I already have changed my upper mount and im tryin an experiment with the old one which i will get back to you guys about.
#307
12-21-2005, 08:32 PM
2nd Gear
Join Date: Apr 2004
Location: North Hampton, NH
Posts: 77
Likes: 0
Received 0 Likes
on
0 Posts
I find the comments regarding the VGS interesting as I put in on my JCW MCS a few thousands miles ago in the middle of summer. Things I noticed was that at cold start in warm weather it made the car very jerky (almost exagerated yo-yo) for the first few minutes of motoring. It then smoothed out and seemed to dramatically reduce the yo/yo flat spot. I could still feel the flat spot but it was/is more subtle and was easy to add a little throttle and get through it.
In cold weather it feels even better. Strangely enough smoother at cold weather cold start and much more linear in general with even less of a flat spot. The pick off points on my early 05 are the same as shown in the various instructions so I'm confident the early 05s are the same as early cars. As an aside, the engine in general really seems to have come alive around 7000 miles or so.. seems easier to rev and more responsive.
In cold weather it feels even better. Strangely enough smoother at cold weather cold start and much more linear in general with even less of a flat spot. The pick off points on my early 05 are the same as shown in the various instructions so I'm confident the early 05s are the same as early cars. As an aside, the engine in general really seems to have come alive around 7000 miles or so.. seems easier to rev and more responsive.
#308
12-31-2005, 07:40 PM
5th Gear
Join Date: Apr 2005
Location: Canberra, Australia
Posts: 1,099
Likes: 0
Received 0 Likes
on
0 Posts
I was speaking to an Aussie who had the VGS on his 03 car - which was mainly a track pig. He said it caused the car to backfire - to the point that it fried his cat and he had to replace it!!!
Anyone here have any thoughts about that? My mechanical knowlege is embryotic at best - I don't understand how it would cause the car to backfire....
Anyone here have any thoughts about that? My mechanical knowlege is embryotic at best - I don't understand how it would cause the car to backfire....
#309
12-31-2005, 07:47 PM
I'm no rocket scientist, but the VGS only reduces the amount of vacuum seen by the bypass valve. It doesn't affect air, it doesn't affect fuel.
Your friend may have had the VGS, but I can't think of a scenario where the VGS would CAUSE that issue. It may be COINCIDENT with the issue, but if the car is a 'track pig' odds are there are many different modifications to the car that would be more likely suspects. Especially if he's not running the stock ECU software.
Your friend may have had the VGS, but I can't think of a scenario where the VGS would CAUSE that issue. It may be COINCIDENT with the issue, but if the car is a 'track pig' odds are there are many different modifications to the car that would be more likely suspects. Especially if he's not running the stock ECU software.
#310
12-31-2005, 10:48 PM
There seems to be a misconception here
Originally Posted by Eric_Rowland
I'm no rocket scientist, but the VGS only reduces the amount of vacuum seen by the bypass valve. It doesn't affect air, it doesn't affect fuel.
Your friend may have had the VGS, but I can't think of a scenario where the VGS would CAUSE that issue. It may be COINCIDENT with the issue, but if the car is a 'track pig' odds are there are many different modifications to the car that would be more likely suspects. Especially if he's not running the stock ECU software.
Your friend may have had the VGS, but I can't think of a scenario where the VGS would CAUSE that issue. It may be COINCIDENT with the issue, but if the car is a 'track pig' odds are there are many different modifications to the car that would be more likely suspects. Especially if he's not running the stock ECU software.
#311
12-31-2005, 10:52 PM
Exactly backwords.
Originally Posted by norm03s
The VGS mod. taps into the intake manifold at #1 cylinder intake runner. The intake manifold sees a higher vacuum than the intake duct between the throttle body and supercharger intake duct.. This causes the bypass valve to close earlier as there is a higher vacuum acting on the bypass valve diaphragm allowing the supercharger to build boost earlier. Issues of back firing would indicate a vacuum leak. A possibly if that was the only thing touched when doing this mod.
Otherwise, it would close in light load, and open under boost.
Matt
ps forgive spelling, I've had about 5 glasses of champagne! Happy new year!
#312
12-31-2005, 10:59 PM
5th Gear
Join Date: Apr 2005
Location: Canberra, Australia
Posts: 1,099
Likes: 0
Received 0 Likes
on
0 Posts
#313
12-31-2005, 11:13 PM
No clue.
But it's not easy to understand. The TB position is determined by a feedback loop in the computer via the pre-SC pressure sensor. The bypass valve opening and closing sure can mess with the reading there. The fuel is set (I think) based on the post SC T-MAP sensor. Vacuum leaks... well who knows how all this works out. It will make the TB close more for a given RPM and load, but it the T-MAP based control is perfect, the problem would be between the air the computer thought it should be getting, and what actually can get into cylenders....
Basically, I have no clue. But because the VGS can see boost, I put wireties on all the connections, so it couldn't leak under boost. Also reduces the chance of vacuum leaks.
Matt
ps, did I say Happy New YEar?
Basically, I have no clue. But because the VGS can see boost, I put wireties on all the connections, so it couldn't leak under boost. Also reduces the chance of vacuum leaks.
Matt
ps, did I say Happy New YEar?
#314
12-31-2005, 11:17 PM
Originally Posted by Tit
OK...so....if there were a vacuum leak, how would that cause the car to back-fire?
Has anyone experienced any other issues, other than the initial roughness coming off the throttle (ie. engine braking)...?
Has anyone experienced any other issues, other than the initial roughness coming off the throttle (ie. engine braking)...?
I've had the VGS on my 03 for probably alittle over 30K miles now and I have no issues that have been mentioned above. I havent checked my lines in awhile (for hardening) but the last I checked them (about 10K ago) they were fine. All in all I've been very happy with this mod.
Oh, and Happy New Year to the Down Under Crew
Nik
#315
01-01-2006, 12:10 AM
Your right! that was bass akwards of me duh
Originally Posted by Dr Obnxs
The valve open under high vacuum, closed under reduced vacuum. With the action of the SC, the valve will close earlier ( in terms of post TB vacuum and RPM).
Otherwise, it would close in light load, and open under boost.
Matt
ps forgive spelling, I've had about 5 glasses of champagne! Happy new year!
Otherwise, it would close in light load, and open under boost.
Matt
ps forgive spelling, I've had about 5 glasses of champagne! Happy new year!
A vacuum leak will cause a lean condition. When letting off the gas this additional air will cause unburned gas in the exhaust to ignite i.e. backfiring.
I have run this mod almost a year now I like the quick throttle response, no problems. Thanks to Andy
#316
01-01-2006, 08:34 AM
#318
01-09-2006, 07:02 AM
#319
01-09-2006, 07:04 AM
5th Gear
Join Date: Dec 2004
Location: San Luis Obispo, CA
Posts: 1,091
Likes: 0
Received 0 Likes
on
0 Posts
#320
01-09-2006, 07:46 AM
#321
01-09-2006, 08:26 AM
5th Gear
Join Date: Dec 2004
Location: San Luis Obispo, CA
Posts: 1,091
Likes: 0
Received 0 Likes
on
0 Posts
#322
01-09-2006, 08:55 AM
Originally Posted by andy@ross-tech.com
If you don't have any yo-yo, then I wouldn't bother. I certainly didn't do it for any other reason.
Mine was acting up last week......rev'd the engine and it dipped below idle a few times and felt some power loss......Feels ok this week.
Im thinking its my by-pass.
#323
01-09-2006, 09:02 AM
#324
01-09-2006, 11:39 AM
6th Gear
Originally Posted by 1FSTMINI
Mine was acting up last week......rev'd the engine and it dipped below idle a few times and felt some power loss......Feels ok this week.
Im thinking its my by-pass.
Im thinking its my by-pass.
#325
01-09-2006, 12:08 PM
It would happen if i blip the throttle at a stop....Idle would drop below normal feeling like she wants to stall and my boost gauge needle is jumping at full boost in the top of 3rd.
Does there by-pass feel like the VGS.....i dont want that real response feel that the VGS gives you with these crappy motor mounts.
Does there by-pass feel like the VGS.....i dont want that real response feel that the VGS gives you with these crappy motor mounts.