tici

iTrader: (1)

My scans while shifting clearly show that when the TB closes the engine speed rises for about 1/2 second, then drops (see the attached pic).
Only then the tranny allows me to shift.
The engine speed decreases pretty slow too, slower than when the blower is disconnected. Result: it takes up to 2 second to shift
Without blower it shifts as it should.

This is a manual (T56) 1998 trans am with a 5 PSI Vortech SC. I still have the original Bosch bypass valve.

Is it possible that this bypass valve is too small?
Is it possible that the TB is shot? (I don't think so, because the idle is fine and the MAP shows 29 - 30 kPa).

Is this a common problem with manual trannies?

Thanks!

Stefano

Inspector12

iTrader: (29)

It take the bypass valve just a second to depresure the charge pipes and it is forcing more air through the hole in the TB blade. Nothing to worry about IMO. Good luck.
Jeff

Got Me SOM

iTrader: (2)

you sure it aint clutch/tranny related??

tici

iTrader: (1)

Sure. But this causes veeeery long shifts.
According to the scans I can shift in 1/2 second when not supercharged (belt disconneted) but 2 seconds with the blower ON.
...a lot of time!

I was thinking that tranny and clutch were shot until I removed the belt: now it shifts smooth and fast

Look at the picture: see the delays? the rpm rises while the TB is closed.
The TPS doesn't show higher values, so I think the blade is really closed.

Only think: at idle the TPS shows values between 0% and 0.4%.
Is it really a little open? Or is it normal?

stevieturbo

How does the rpm hanging on, affect how long it takes you to lift your foot, change gear, and step on it again ???

That mechanical/human action should take the same amount of time, regardless of what rpm the engine is doing ???

Is your complaint about fast driving, normal driving ?

Its weird though. I use a different ecu, with no ISCV at all. My logs look as if the rpm does hang on a few tenths after I shut the throttle to shift.

I believe its just a logging issue, as my car shifts fine, pretty much every time, regardless of how I drive it.

tici

iTrader: (1)

without blower less that a second, with blower up to 2 seconds. (confirmed by scanning)

I can confirme this. Shifting time is the same no matter how I drive.
Without blower always less than a second, with the blower always much looooonger.


Both. pushing on the clutch pedal and let off the gas happens almost at the same time. without the blower the engine speed start to drop as soon the TB is closed. with the blower it rises during 1/2 second, then drops.
I have to wait. the tranny doesn't allow me to shift and if I force it it grinds.


that's what I'm talking about.

I made a scan with and without the blower. there is a clear difference.

here two examples (both with blower)
1-2-3-4-5-6-5-4-3-2-3 quite driving
http://videos.streetfire.net/video/7...5d00c920dd.htm

1-2-3-4-3-4-5 not so quite driving
http://videos.streetfire.net/video/2...5d00cc150f.htm

speedfreak440

iTrader: (9)

Have you checked the transmission and/or motor mounts. Could be the extra torque is enough to bind things up just a bit.

tici

iTrader: (1)

The shifts you can see on my attachment were all when not under boost (between 1600 and 2600 rpm).

The mounts look fine to me.

Maybe the extra rotating mass of the blower impeller? OK I can check this disconnecting the pipe betwee blower and TB...

TNTramair

iTrader: (15)

your also adding an additional 100+rwtq with the supercharger and 100+rwhp...it may be just the clutch not keeping up...which would explain why its ok when the blower is disconnected. just a thought. i.e. "nitrous"

stevieturbo

I dont understand??

Does your foot/hand move slower or something ?? The physical action of you changing gear, shouldnt take any longer, regardless of setup.

It doesnt matter if I have a blower, or Im travelling 1mph, or 100mph. My shifts take 0.4 seconds ( when trying )

stevieturbo

Watching the videos, Im even more confused.

All the shifts look very lazy and slow to me on both videos ?? Are you even trying to shift quickly ??

Also, the stick action looks very notchy. I know my T56 just slips into gear nicely. Is there any oil in the box ? if so, what are you using ?

hardbodeez

iTrader: (10)

I know this may sound silly, but are you pushing the clutch completely down? With my spec 3+ clutch I had the same problem with sticky, notchy shifting with the nitrous on. I moved the seat a tad closer and fully pressed the clutch to disengage.
Or you can adjust the travel on your clutch m/c depending which one you have.
Just a thought, but made all the difference with me. Now it shifts much easier.

LSs1Power

iTrader: (5)

I dont see a problem in that vid.

tici

iTrader: (1)

The shifts in the scan were in a non-boost RPM range.
No slipping, or the RPM scan would show a curve and not a straight line.

tici

iTrader: (1)

My foot moves tha same way: supercherged or not (at least I hope so ).
When I say "I can't shift" I mean the syncro's ring aren't allowing me to select the gear. I feel a resistance in the shifter. As soon the gears are "ready for the shift" the shifter is "sucked" in the right position.

tici

iTrader: (1)

I was shifting as fast as I could
If I force it it grinds.

It is notchy. The oil is mineral Dexron III (BP Autran DX).
The tranny is a 97 Borg Warner (still original internals) with 50'000 miles on it.

tici

iTrader: (1)

The master cylinder is modified (homemade - adjustable), it pumps more liquid than normal. The slave cylinder is a new design, the clutch is a 2002 stock. The hydraulics have been pressure bleeded. Drill mod done.
New pilot and TO bearings.

I'm 200 cm tall and I don't need to get closer to push the clutch all the way down ( I actually had to modify the seat to fit in the car!)

stevieturbo

IMO, you have a tranny/clutch/arm problem.

When racing ( and when I log ), from I lift foot off throttle, press clutch in, change gear, let clutch out, and stamp on throttle again, takes 0.4seconds.

Im using Fuchs ATF in my T56, and it shifts great.

tici

iTrader: (1)

That's possible. This is a used tranny I installed on my previous automatic car.
No idea if the old owner was really able to shift
The next question is if I have a M6 program... yes. I have.

What kind of bypass valve are you using?

Fuchs ATF: I don't know this brand. Is it synthetic?

HAs your tranny been rebuilt? I was thinking to do it myself...

stevieturbo

Mine is used as I bought it a couple of years ago, from a 2001 Camaro SS

Fuchs ATF4000

http://www.fuchs-europe.de/1712.0.html