Understanding Boost Controllers

[R33_Beast]

Very basic question here so please straight answers.

Ignoring gear based electronic boost controllers, should max boost be equal across all gears (excluding first due to limited exhaust gases to make boost)?

For example, if I was to install say a Turbotech manual boost controller in my S15 should I expect to see 15psi at 3500rpm in 2nd, 3rd, 4th gear etc or would each gear boost differently?

I believe my boost controller is playing up so just curious on how it 'should' be working in theory.

[linkems]

test boost in 3rd or 4th where there is some proper load. Ignore boost in 1st and 2nd gear where there is hardly any load.

[R33_Beast]

I'm most interested in boost achieved in 2nd gear as that's the gear I tend to rev on the street.

If my car is tuned for 15psi @ 3500rpm in 4th gear then should it still make 15psi in 2nd gear?

[89CAL]

It will still make 15psi just not at the same revs

[GH05T]

boost creep issues tend to become evident in taller gears too when you get the revs right up their for longer than a spike.

[Dose Pipe Sutututu]

I would say depends on engine load, not too much gears .. imagine you're going up a super steep hill in 2nd.. like shopping centre slope, but somehow 1km long LOL

[scotty nm35]

Lol, my $25 ball and spring won't hold stable boost, there must be something wrong with it...

[R33_Beast]

Thanks for the replies guys. So it sounds like I will still hit 15psi in 2nd gear but it may be at say 3800rpm whereas it hits at 3500rpm in 4th gear.

If I replace my seemingly faulty HDI EBC with a Turbotech manual controller I'd like to see a very responsive 15psi in 2nd gear. I just don't want to have it set up in 2nd gear only to have it boosting higher in 3rd and 4th gear. My car is running a NisTune tuned for 15psi in 4th.

[Dose Pipe Sutututu]

You will still find a proper EBC with gain controls will bring boost on a touch sooner than a turbotech ball bearing valve. I believe those HDi controllers only allow you to adjust a targetted boost i.e. duty cycle of the valve and not the gain

[R33_Beast]

You will still find a proper EBC with gain controls will bring boost on a touch sooner than a turbotech ball bearing valve. I believe those HDi controllers only allow you to adjust a targetted boost i.e. duty cycle of the valve and not the gain

You're correct John. The HDI EBC merely had two turnable control knobs (one for low and one for high boost). You could increase or decrease boost by turning the knob. There were no other options like gain etc.

My new TurboTech v2 boost controller with the electronic missile switch arrived today and will be installed shortly. Fingers crossed it provides the excellent boost response and rock solid high boost that everybody raves about. PITS will be turning the boost back up to 15psi and checking the tune so I'll report back and compare my dyno sheet with the HDI compared with the TurboTech.

I am wondering whether I should block the standard recirc valve up (with a grub screw) to hold boost better above 5500rpm. During my original dyno run 18 months back you could see the boost would hold at 15psi until roughly 5500 and then taper off to 13.5psi from there.

[GTSBoy]

My car is running a NisTune tuned for 15psi in 4th.

You see, that's where you are thinking about it wrong. Your ECU is not "tuned for 15 psi". It is tuned for the airflow that it flows when you are at the highest load conditions. That would be 15 psi at max power revs in 3rd or 4th. But your ECU and the tune don't really measure or care about the actual boost. Just the power.

As to the boost falling off after 5500 rpm......that's nothing unusual. No boost controller can overcome what happens when you try to shove a crapton of gas through a small exhaust housing. Boost tends to fall off under those circumstances.