Supercharger and M6
Thread Starter
TECH Fanatic
iTrader: (1)
Joined: Oct 2003
Posts: 1,066
Likes: 1
From: Zurich - Switzerland
Supercharger and M6 Last year I swapped my tranny from A4 to M6 
Before the swap I already had a Vortech supercharger and shifting at high rpm was obviously not an issue.
Now, with the M6 I notice something strange: when I shift the engine speed doesn't drop as fast as it used to be without the supercharger.
I dont powershift, it's a normal shift at maybe 4000 rpm.
It's like the blower is pushing some air into the intake manifold and doesn't allow the engine to reduce the rpm.
It's not too bad but I feel it and I don't like that.
Is my Bosch bypass valve too small? too slow?
Do I have to increase the size of the rubber hose between intake and bypass valve? (signal hose for the bypass membrane).
Do I have to buy an adjustable bypass valve?
Or is it just normal?
Thanks for every hint!
Stefano
Before the swap I already had a Vortech supercharger and shifting at high rpm was obviously not an issue.
Now, with the M6 I notice something strange: when I shift the engine speed doesn't drop as fast as it used to be without the supercharger.
I dont powershift, it's a normal shift at maybe 4000 rpm.
It's like the blower is pushing some air into the intake manifold and doesn't allow the engine to reduce the rpm.
It's not too bad but I feel it and I don't like that.
Is my Bosch bypass valve too small? too slow?
Do I have to increase the size of the rubber hose between intake and bypass valve? (signal hose for the bypass membrane).
Do I have to buy an adjustable bypass valve?
Or is it just normal?
Thanks for every hint!
Stefano
Thread Starter
TECH Fanatic
iTrader: (1)
Joined: Oct 2003
Posts: 1,066
Likes: 1
From: Zurich - Switzerland
I drove the car a couple of weeks without the blower and it was different. I noticed this "problem" as soon as I installed it back.
I can scan for rpm, TPS and MAP and see what happens during a shift...
In the original Vortech configuration the bypass valve is connected to the hose that goes from the intake to the brake boost, this using a rubber hose: about 2 ft long and 0.15" inner diameter (5/32"). I can imagine that this hose is too long and too tight causing a little delay between the closure of the TB and the opening of the bypass valve.
Do you also have a manual?
I can scan for rpm, TPS and MAP and see what happens during a shift...
In the original Vortech configuration the bypass valve is connected to the hose that goes from the intake to the brake boost, this using a rubber hose: about 2 ft long and 0.15" inner diameter (5/32"). I can imagine that this hose is too long and too tight causing a little delay between the closure of the TB and the opening of the bypass valve.
Do you also have a manual?
I experienced the same problem with my stock motor, and starting to see it again with the new setup. I tried ironing out the problem before and found that it was not SC related, but PCM related.
Im not sure about you LSx guys, but for us LT1 guys the PCM base programming is different between an Auto car and a M6 car. Something with the load tables as Ive been told.
When I did my A4 to M6 swap is when I noticed it. What I was told needed to be done, was to get another PCM from a car with the same options, but originally a M6. Or go have the dealership reflash the PCM with a base program from a M6 car. For the latter option, all you need is an equally optioned M6 cars vin number.
We tried copying and pasting load tables from several cars to no avail when trying to eliminate the problem on the stock motor. For this one, a buddy with Tunercats is going to get me a copy of the base file needed and load it on my PCM for me.
Im not sure about you LSx guys, but for us LT1 guys the PCM base programming is different between an Auto car and a M6 car. Something with the load tables as Ive been told.
When I did my A4 to M6 swap is when I noticed it. What I was told needed to be done, was to get another PCM from a car with the same options, but originally a M6. Or go have the dealership reflash the PCM with a base program from a M6 car. For the latter option, all you need is an equally optioned M6 cars vin number.
We tried copying and pasting load tables from several cars to no avail when trying to eliminate the problem on the stock motor. For this one, a buddy with Tunercats is going to get me a copy of the base file needed and load it on my PCM for me.
Trending Topics
Thread Starter
TECH Fanatic
iTrader: (1)
Joined: Oct 2003
Posts: 1,066
Likes: 1
From: Zurich - Switzerland
Fire67: The car has a M6 program now... but it's true: you can't just copy the tables you see (like with LS1Edit), you need the complete program.
ABeasst: sure! I just wanted to say "shifting when under boost".
The higher the RPM the more I notice this behaviour.
Around 5500 rpm it takes maybe 0.5 - 1 second to reduce the engine speed.
You can notice the same when you let go the gas pedal at high rpm: it just stays there for a little moment (again: 0.5 - 1 second)
Kinda of dangerous in certain situations
ABeasst: sure!
I just wanted to say "shifting when under boost".The higher the RPM the more I notice this behaviour.
Around 5500 rpm it takes maybe 0.5 - 1 second to reduce the engine speed.
You can notice the same when you let go the gas pedal at high rpm: it just stays there for a little moment (again: 0.5 - 1 second)
Kinda of dangerous in certain situations
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Pouria Savadkouei
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Verdad Gallardo
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Hennessey's New Supercharged Silverado ZR2 Has 700 HP
Verdad Gallardo
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Verdad Gallardo
Awesome K5 Blazer Restomod Comes With C7 Corvette Power
Verdad Gallardo
10 Camaros You Should Never Buy
10 LS Engine Myths That Refuse to Die
Verdad Gallardo
Thread Starter
TECH Fanatic
iTrader: (1)
Joined: Oct 2003
Posts: 1,066
Likes: 1
From: Zurich - Switzerland
Originally Posted by DeltaT
Try adding an extra throttle return spring, to close the air door faster and more firmly.
Jim
Jim
however: butterfly valves (like in the chemical industry) close themselve when they are close to the OFF position. It's a fluid-dynamic thing.
So I was thinking it wasn't a blade related issue
