[alanm474]

Hello, I have a Z4 sDrive28i, and my goal is to have little turbo lag, i want to improve the spool from low rpm, I want 20 psi 1500 rpm, that is, I like to make the car hard and shake, I do not care comfort .
For this, for me? Map 1 BMS Stage1 JB4 and give the same psi at low rpm? or less psi JB4 has to be softer and pleasant?
Thank you.

[Project Elite]

I believe JB4 runs a much more aggressive tune, that's why it's a stage 2 tune. However, 20 PSI founds a bit high for 1500 rpm. I'm sure it can achieved through ECU tuning though.

[mike@x-ph.com]

Jb4 give you a lot more control over boost. It seems you are looking to run map 6 with JB4 where you can enter your own boost targets,
That being said you wont be able to reach 20 psi at 1500 rpm

[mike@x-ph.com]

Originally Posted by Project Elite

I believe JB4 runs a much more aggressive tune, that's why it's a stage 2 tune. However, 20 PSI founds a bit high for 1500 rpm. I'm sure it can achieved through ECU tuning though.

If the JB4 cant do it, a flash wont be able to do it either

[CalCarNut]

I'd think 20psi at 1500 would hammer on the drivetrain way too much....but thats just me.

[alanm474]

Maybe it was too exaggerated, but my idea is from 20 psi to 2500 rpm.
My question arises as several sides lei stage1 BMS is not as smooth as JB4, the JB4 blows less psi at low rpm really?

[SeanWRT]

It's very uncommon that you find turbo lag with N20. I believe that's all about how you define lag.

A OEM like tune has a flat torque curve at mid range and it goes a little bit down when it's time for a shift. You can hardly feel any lag cuz in reality you get max boost below 2k rpm for sure. How can you complain car doesnt feel very strong when it's under 2k?

An aftermarket tune tends to max out turbo capacity by not limiting boost, which is to allow a full load early on (happening at 3kw~3k5 with N20 depending on the supporting mods) when RPM is too low to digest so much air, which results a very high boost. With RPM getting high, the turbo is not producing any more air than it is at low RPM cuz it's already maxed out, so the boost gets lower and you see torque curve goes all the way down until reaching red line. In that way, you probably will feel "lag" cuz the maximum torque is felt at 3k+.

Asking BMS Stage 2 for a high boost target early on works exactly the opposite direction theoretically. But in reality, it is the throttle response you gain with the tune that will address the lag issue and you'll be impressed by torque felt at 3k5. At the end of day, if N20 is truly a laggy car hardware wise, there is no solution in tune.

[rednose]

Turbo lag is only noticeable early in the rev range not at high revs.

When your losing or dropping power in the top end that would normally indicate that your turbo is out of puff, a turbo running out off puff is NOT turbo lag, it just cant physically push more air efficiently.

These cars have very little lag, there is no need for 20psi at 1500rpm and not really sure that could be acheived on this turbo anyway, but if you could get 6 or 7 psi more than factory and retain similar timing then these cars would feel unreal.