Most BOVs I read so far only vent when you let off the gas. Since SST shifts too fast for the BOV to keep up, most won`t release the boost pressure in between shifts at WOT - so only when you rev it up in a single gear pull and let go of the throttle do you get the actual venting happening. So the only way you CAN have it released it between shifts is you have to physically let go of the throttle.

So is there a BOV out there that is quick enough to vent in between SST WOT shifting?

 

Why in the world would you want to release pressure between shifts? The point is to keep that pressure through the shift...

 

To avoid boost spike in-between shifts.

 

Thought the MR's were supposed to hold pressure during the shift (kinda like no-lift-shift ??)

If not then shouldn't the stock BOV do the job?

(FYI: total noob here, just interested in the subject.)

 

Ditto. That's my exact understanding.

 

I still don't understand. There is no such thing as "in between shifts", since a clutch plate is always in contact with the final drive, unlike complete disconnection of drivetrain from motor in a manual when you press the clutch.

 

If you dont lift of the gas between shifts, the bov does not vent. The shift is fast enough that the boost spike is minimal. Keep in mind that at redline on a stock turbo, you only have about 18-19 psi as it is, on a good day. Peak boost on my set up is 26.5. So the turbo has to make up that 7.5 psi as soon as the car shifts. The spiking is minimal, and what there is of it is usually okay. Keep in mind that this is wot.

 

it cant be good to lift your foot from the gas then shift? can it?

 

I'm not sure but I don't do it when driving my MR. Occasionally I will relieve some pressure on the pedal between shifts though if I'm at low speeds.

At part throttle my car will hold pressure up until around 4th gear. Even if I keep the same amount of pressure on the pedal it will still vent. Going WOT it holds throughout all gears. I assume this is normal?

I'm running a Forge BOV.

 

You can actually no load shift the SST as long as you are not in s-sport mode. To keep from confusing the trans and getting jerky no load shifts, you move the shift lever first, then a fraction of a second later, lift the gas pedal. It will take some practice to get it right, but its doable. In s-sport mode though, it will jerk so hard if you dont get it just right, that your neck will hurt.

You can also increase the time between shifts artificially by skipping a gear. This forces the trans to actually shift gears rather than shafts, which takes longer. Not sure exactly why you would want to do this, but you can. Just bummp the shift paddle/lever twice while lifting off gas as explained above.

The only reason I can see for no load shifting would be if you have extrememly aggressive aftermarket clutches and steels, and are trying to get them to last more than 10k miles for street driving. Even then, it is questionable wether it would actually increase clutch life or not.

 

That is not a very good idea .. doing a no load shift on the SST increases the wear on the clutches .. just like manuals .. worse especially when you're in Normal mode ..because it assumes no loads and slips the clutches in as you suddenly increases the load .. doesn't happen on SSport mode because there is little to no slippage during gearshifts .. thats also why SSport shifts in manuals tends to be more jerky ..

As webman mentioned .. you want to keep the pressure during shifts so that you're perpetually in the powerband rather than dumping the pressure .. and then wait for turbo to fillup the pipings and IC and then power up again ..

Kozmic is exactly right to say during shifts there is little to no boost spikes .. even on big turbos .. think of SST as an automated form of NLTS .. your throttle plate never really close and boost will be within +/-1-2psi of what you set for the rpm that the gear engages at ..

 

Exactly what I figured. I didn't think there's was really a need to vent between shifts because of the quickness of the shift.

 

Well if you want a suggestion .. I just put on the synapse ..

it vents so fast its ridiculous .. inbetween gearshift you can hear the dumps ..

Problem is it holds too well during the initial spoolup .. so you'll be going into overboost pretty fast on downshifts in full auto mode ..

 

Did it trigger P1870?

 

Have you been able to tune around it so that you don't overboost when downshifting?