What Rpm Do You Get Positive Manifold Pressure?

[jase_c]

Hi guys, i have just picked up a R34 Gtt (auto) and it seems to take a while to get to boost. Could a few of you let me know what RPM your standard turbo 34's start to make positive manifold pressure so i can see if mine is the same or not, at the moment it doesn't become positive till around 3000rpm and i am wondering whether theres a leak or if thats normal.

[GTSBoy]

Should be not much more than 2k.

[sonicz]

Don't forget with an auto the transmission is not always directly engaged with the engine, so what rpm postive pressure comes depends largely on how much throttle you are applying. Don't expect much boost with the stock auto boost controller anyway.

Edited April 28, 2013 by sonicz

[jase_c]

Nar the car has an apexi avcr to control boost and by the look its set at 1.1 bar, need to get the car to a tuner pronto to give it a good tune methinks.

[GTSBoy]

1.1 bar on standard turbo? Asking for trouble. If not standard turbo, then why did you bother asking what rpm is boost threshold without telling us what turbo you have?

[jase_c]

Its 1.1 kg/cm well thats what it says on the apexi but its not getting that high .As i stated in the original post i just got the car, it looks like the standard turbo as all the stock piping is coming off the outlet of it.

[sonicz]

Ok even though my car is pinging, I set my car to stockish boost and took some dodgy videos to show you how the automatic transmission and throttle is the biggest factor in what RPM an the car develops positive pressure.

In D, on snow start setting, full boost can come as early as 2000rpm. In L setting, gear one, and "power" setting the engine may reach around 5000rpm before the gauge show you full boost. It Depends on how much throttle you give it as well. 3/4 is different to full.

Unfortunately I am capped so it will takes ages to upload

What are you reading the boot pressure off? Just to let you the stock boost gauge measures in mmhg (millimetres of mercury) and not psi.

Edited April 28, 2013 by sonicz

[sonicz]

In L

D, power setting

Edited April 28, 2013 by sonicz

[jase_c]

reading boost off the apexi avcr and the stock gauge. just thought around 2800-3000rpm was a little late to get positive pressure. Thanks for the video sonicz

Edited April 28, 2013 by jase_c

[GTSBoy]

There's no point talking about boost threshold unless you're talking about 100% throttle and a high enough gear to get sufficient load into the engine to get the exhaust flow up.

1st gear and even 2nd gear are a waste of time. 3rd or 4th in a manual or whatever you can achieve in an auto without it kicking down too many gears.

[paulr33]

adjust the tune to bring boost on earlier (more timing)

1.1kgmc2 is too much boost for standard turbo

auto runs different diff gears to manual so gearing would play a part (engine load / turbo charger boost pressure ramp)

auto also runs different stock boost actuator (irrelevant when using boost controller)

imho tune your ecu setup and you should be around the equiv of a manual ish

from memory in my manual 33 tuned i had 0.85kgcm2 by 2700rpm

[jase_c]

Thanks for that info mate, the car has a greddy emanage ultimate setup and i have it booked in for a tune in 2 weeks so will know more about whats going on then. I am starting to think the stock turbo may have been hi flowed or something for that boost.