Im thinking about reinstalling my decel valve
 

So... I read over and over about how the decel valve on my car is worthless.. and since my hose to it had a vacumn leak I removed and plugged.. NOW Im starting to think there is a DAMN good reason for it.. and the reason for it is the 915 transmission...

I have noticed I need to keep my RPM's up between shifts or Im killing dogteeth.. I think the decel valve does this right?

decel valve is an emissions thing.

try shifting faster (better timing) to match the falling rev's.

Apparently you've never shifted a 915? There is nothing fast about that transmission.

It may be an emissions thing.. but does it do what I think it does? Keeps RPM's up on decel? If so mine is going back! I HAVE to keep my accelerator slightly depressed or blip inbetween 2nd and third... Im not saying its right.. Im saying I dont have $3k to fix it right now... and its easy to do.. but since I move between cars.. I forget.. and when I do.. OUCH... dogteeth get torn all to hell.

And Im talking upshifts here...

:rolleyes:

If your timing is right, they are very fast. ...even with worn syncros.

However, getting the syncro's & dog-teeth replaced will make the box easy for anyone to shift fast.

The decel valve is there to stop an over-rich F/Air ratio, when you quickly let off, closing the intake air. --an emissions thing.

edit: if you want to shift slowly, you don't have to let ALL the way off the gas pedal. ...when up shifting. ...making less work for the syncro's

the decel valve won't fix the transmission. i disable them all the time and the cars still shift fine. just practice shifting slower maybe.

Ok.. I guess I suck then.. so seeing as how I suck... does it keep rpm's up? Sounds like not...

LOL.. slower, faster... which is it?

I know how to shift.. been road racing for years.. I know what MY transmission needs.. it needs to be shifted slow and it needs RPM's put back on the main shaft.. bottom line.. it is what it is.. I just need to remember to do it.. I've been driving my little econo box honda a lot with fuel prices.. so I forget..

OK.. nevermind.. I thought I was on to something here...

I just sucked up some bandwidth....

thanks for the answers...

I am gonna try Kendall though.. who knows.. have the pelican religion in it now.. :)

The decel valve slows the drop in rev's. ...which can also be done by letting off the gas pedal more slowly.

The more you let the rev's drop, the harder the syncros have to work ...and when not up to par, that takes a long time.

otoh,
If you have awesome shift timing, the syncros can really suck (feeble) but you can still be quick.

You're not crazy. It does cause the RPM to fall slightly slower when you let off the throttle between gears which makes it easier to up-shift in town at moderate engine speeds. As others have said it is purely an emissions device and you can match flywheel and input shaft speeds on your own but the decel valve when operating properly does make it a little easier.

Decelleration valve makes your car behave like a 72 Buick... there's barely any connection between the gas pedal and the motor. Lots of people like this.

Only CIS cars have that valve, everyone else matches rpm's with toe and heel or double clutching or matching shift rpm's, or gets there transmission fixed. Sometimes my car will not go into 2nd gear. I have to almost start over! So now, i try to shift out of first around 4300 rpm. That seems to work best.