Manual Boost Controller

[CupraGTi]

Hey guys,

I've been searching the webs and have been getting some pretty conflicting reports on using a Manual Boost Controller to up the boost. I'm not looking to go retarded, just give myself an extra 4Psi. I'm punching 10Psi at the moment, and I think 14Psi would be pretty safe. I've read about doing a Diode mod? but I don't think our cars even have the MAP sensor hooked up... I've also read that under WOT if you have a MBC hooked up it runs fine, but if you part throttle, it send the car into soft limp mode...

Some people say they just leave the n75 hooked into the intake, but cap off both nipples, and hook in the MBC instead. Others run the MBC in parallel to the n75, which I couldn't see doing anything at all, except maybe help with boost spikes...

I'm bloody confused... I just want to wind it up 4 psi... why is it such an issue?

Kris

[Umai Naa!!]

Without the ability to monitor AFRs and detonation, you'll never actually know what 'safe' is.

Do some of the basic mods, and then get the ECU re-mapped. Trying to fool the ECU with bleed valves, etc, won't net you a reliable result.

[sambb]

Running an MBC in parallel with the N75 is done to reduce your peak boost. I needed to do this to reduce overboost after a few breathing mods. To up your boost you would place the MBC in series with the N75 ie the line running from inlet pipe to the N75 and start to add restriction until you see the boost increase you want but there's a risk. Don't run the MBC as a standalone with the N75 un-plumbed. The car will flick to peak boost setting on about 1/10th throttle application if there is any load. Its either vacuum or full boost and no ability to modulate boost with your foot/ECU in between. Its like driving a light switch.
Alternatively you could just explore the different types of N75's. The ECS tuning N75 which is a rebadged N75H will get you a bit more boost. Or you could piggy back a 2 pound spring onto you wastegate actuator for a bit more snap.
But as mentioned above, you are just playing a guessing game with this kind of stuff if you're not logging or doing it tie in with other mods. Just do air in air out mods first and go from there or if you don't want to go down this $ hardware mod route, just buy a stage/phase 1 flash tune and be done. At least then you know nothing is going to grenade on you.

[CupraGTi]

It's breathing really well... both ends....

But I guess what I'm asking is... where do I plumb the MBC? and will it give me a weird part throttle response??

[CupraGTi]

I've done this... I'll see how it goes...

I've usually only used MBC's on cars with standalone which is really easy... you just tap into the reference line from wastegate actuator to intake boost reference...

I'll go for drive and see..

[CupraGTi]

Ok... So I did it as above, and I did get above 10Psi... Just way too much above 10Psi and fuel cut/timing retardation kicked in... I had screwed the turbosmart boost tee all the way to minus, but still it just boosted off its head..

first run, it went up to 17-18Psi and cut, then everytime I tried to play with the tee and wind it up or down to try find a sweet spot or whatever, boost was cut at 15Psi...

Am I missing something?

[h100vw]

Ok... So I did it as above, and I did get above 10Psi... Just way too much above 10Psi and fuel cut/timing retardation kicked in... I had screwed the turbosmart boost tee all the way to minus, but still it just boosted off its head..

first run, it went up to 17-18Psi and cut, then everytime I tried to play with the tee and wind it up or down to try find a sweet spot or whatever, boost was cut at 15Psi...

Am I missing something?

Only that ECU is clever enough to stop you scrapping the motor... Too much airflow, N75 duty cycle at 0, airflow still rising. It calls game over.

You can't fool them. A tune wins every time.

Gavin

[Umai Naa!!]

Am I missing something?

You're missing the bit where the ECU controls the boost.

[h100vw]

No way to get 4 psi extra from it with a bleed valve. Even with it being 15 years old. It's still more sophisticated than stuff from the 80s ��

[CupraGTi]

In no way am I trying to piss on your parade Gav... not at all... but with a bit of playing around, I have adjusted the boost up to 15psi. True it spikes up to 15psi and comes down to 12psi in 2nd and 3rd, but 4th and 5th both peak at 15psi and stay there pretty much all the way through the rev range..

And it wasn't difficult at all....

[CupraGTi]

Is this like, a huge secret that I shouldn't be spreading or something?

[CupraGTi]

And I don't see how it could be leaning out?? The n75 valve controls nothing but boost pressure... the Air Flow Meter is the sensor that controls air/fuel ratio... so the increased air being sucked in would be complimented with extra fuel...

I understand that timing isn't being played with, so I understand that I'm not getting the most outta the extra few PSI I've gained... but the butt dyno doesn't lie, theres extra power there.

I'm running 98 with octane booster. I am not getting any detonation.. and even if I was, does the 1.8t not have a knock sensor?

I need a front mount......

But the Manual Boost Controller CAN work on our motor.

[h100vw]

I can get 30 psi out of my polo if I want to. Not hard to do. But without the right software. It'll run lean and the chances of engine damage are high. So you haven't stumbled on anything new. Just don't be fooled by looking at only one aspect of getting more power from your engine.

[h100vw]

In my experience, engines feel strongest, just before they quit.
If you're intent on running it like it is. You should definitely be checking the afr.

[CupraGTi]

I hear what you're saying, but what makes a VW so much more fragile than a Subaru? with supporting mods you can raise boost on pretty much any standard computer trubo car. There is a limit to the Air/Fuel map true, but that's what the air flow meter is for... its to take control of the fuel... its not like I'm trying to pump 20psi through my motor... and I WOULDNT... but a couple extra psi should be taken care of by the engine management.

Putting a 3 inch exhaust, and new intake on the 1.8t naturally gave me another 2psi and took it from roughly 8psi to 10psi. The AFM would have taken that into account and given more fuel... All I am doing is fooling the n75, while letting the computer take care of the fuelling.

I will not post how I did this, as it seems to be a contentious issue.

Gav, when I get bigger Turbo, and need fuel upgrade I will definitely be talking to you about Custom Code.