joeyz87

I know that at first one turbo starts at 1500-2000rpm and then the second turbo starts to spin and kicks in at 4 or 5k rpm. What happens if i redline 1st gear and then shift to 2nd? If i begain 2nd gear at 5000rpm does the 2nd turbo provide boost? I'm asking casue it seems to hesitate when i do this.

BobfisH

thats normal. At constant throttle the car will not be producing much boost on either turbo - the second turbo doesnt come online until the first is producing more than 8psi of boost, and then you will get a boost dip and then a spike (Dip is when the exhaust gas is diverted to pre-spool the secondary, spike is when the secondary actually comes online)

So basically, even if you sit at 6k rpm and then floor it, you will still get the hesitatino because the primary comes on, instantly hits 8psi, then boost drops to spin up the secondary too.

joeyz87

So what rpm is best to launch at? It shoul dstill be pretty fast with 8psi right.

dgeesaman

iTrader: (7)

Scenario: redline 1st, shift to 2nd (engages at, say, 5k). Both turbos were pushing, both turbos continue to push. At 5-6k rpm there is plenty of airflow to keep both working well without much lag.

What can happen is you shift at 5k (rather early for a hard run), and you engage 2nd at 4k. The system will in some cases stay in parallel mode, and continue driving both turbos. The problem is the load of both turbos can get a bit laggy at this lower rpm.

For maximum punch on a roll, shift at redline and continue with each gear. Highest rpm all the way through. From a standing start this will just cause wheelspin, so in 1st gear you'll have to experiment with the best drop rpm and if 2nd spins, figure out what the best rpm to hit 2nd is.

Dave

joeyz87

It will redline 1st in like 2 seconds then I shift to second within 2 seconds you sure that is enough time for both turbos to be producing power.

dgeesaman

iTrader: (7)

Yep

You won't get 0-60 in 5.0s without it.

FDNewbie

iTrader: (10)

Heyyy Dave. Haven't seen you a minute!

To be a bit more specific...

Not quite. The CRV opens from about 3500 - 4500 rpms, (pre)venting any prespool from reaching the secondary turbo. Then at 4500 rpms, the CRV closes, spooling the secondary, which should be fully spooled by 5000 rpm.

The reason I'm pointing this out is, if I stay at 9spi at 4200 rpm for a YEAR, the secondary would still never spool or produce any boost. It's rpm based; you have to pass 4500 rpm.

To clarify the "in some cases" parameters, once you go above 4500 rpm and both turbos are active, until you drop below 3000 rpm, you are and will continue to run non-sequentially. So if you always shift at redline, the only time you'll be sequential is from a dig in first, which is when you really need the sequentials - real low in the powerband, to get you up and going real fast. Once you're higher up in the powerband, running the primary alone is a waste, so it's non-sequential the whole way, unless you drop back down below 3000 rpm.

I haven't figured out the best spot for myself, but there seems to be a general concensus that right around 3500 rpm from a dig is the best compromise for minimizing wheelspin and maximizing acceleration.

~Ramy