Overboosting to 15psi with PFC tuned to 7psi?
 

Hi people,

My FD is on stock seq twins with a JDM OEM downpipe, Magnaflow resonated midpipe, Blitz nur spec S catback, and a double K&N instead of the airbox, brand new Apexi Power FC bought 3 months ago.

I am on the PFC base map. I did the mods that arghx wrote on this famous absolutley usefull thread, to keep it safe (less advance timing in the IGT map, 105% fuel over 3000rpm on the PIM volt menu, and all boost settings to 0.55, stock duty %).

Problem is : 2nd gear, WOT ==> POOOOOOOOOW fuel cut ! Boost peak value is 0.85.

So on the advice of a fellow 7 owner, i unplugged the turbo control solenoid (i am not sure about the name, but it is the right one, when you are in front of the engine, of the two bolted to the UIM, in a butterfly shape).

With that mod, no more than 0.52 peak boost value at WOT. So i am happy for now, as i don't risk blowing my engine up. Plus, it means that the wastegate is not the culprit.

But what would be the problem then ? Why the boost isn't following the PFC boost setting ?

Thanks :)

If you free up the exhaust then you WILL see boost creep on the stock wastegate, no amount of boost control is going to correct an overwhelmed wastegate. Add some restriction to your exhaust and/or port the wastegate :)

Also, 7psi as a target boost is rather low. If I remember correctly the secondary turbo won't even actuate at boost that low..

Hi and thank you for the answer.

However, like i said, i disconnected the solenoid, so that i can achieve 7 psi. And it works ! I don't see boost creep at all. I guess the wastegate port is still large enough to cope with the improved flow.

That's why i am asking why the engine can't follow the PFC orders in terms of boost pressure.

you need to adjust the POWER FC not just the boost setting But the duty cycle . lower the duty cycle until you get your desired Boost start very low like 60% on both primary and secondary and gradually increase it . until it kind of holds .

You can also use a Manual Boost controler rather then the OEM solenoid system people say it works better .

also .. .95 is about 14 PSI ( in a stock PFC without boost correction ) , so .85 you are still a couple psi down from 15 .

+1 lower the duty cycle until you achieve the boost level you want. If you can't, you need to test your precontrol and wastegate solenoids for proper operation and leaks. This can be done without removing the UIM/rat's nest so it's a good idea to do it anyway if you haven't.

All right thank you, i will try that asap and let you know :)

I've posted on this before, you are now running outside the parameters of the stock boost control. You either have to mess with pill sizes and the stock solenoids or get a good boost controller. I recommend a good electronic boost controller.

Dale

Hello Dale and thank you.

What would you advice me to buy as a good, relatively cheap boost controller ? I don't mind buying used part.

I have a Hallman manual boost controller under my hood. It does the job perfectly.

lol Steve Kan installed it one fine day while tuning my car.

Welcome to Hallman Boost Controllers


Another good way to get rid of boost creep is to create some kind of bottleneck in your exhaust. Swap that midpipe for a Bonez cat and you likely wont NEED a boost controller, although it will still be a good, safe idea to have it there.






:)

Thanks Natey i will look into it.

However, i havent any boost creep. Like i said before, the turbo control system seems to be at fault here, not the wastegate seat size.

While i'm here, i red here and there that people can also drill the restrictor pills. Is this true for my scenario ?

Delete the turbo control and pre-control solenoids. Then take the two nipples at the 3 oclock position on the wastegate actuators and block them off or connect them together.

Install two Hallman PRO RX manual boost controllers and set to whatever boost you desire.

The factory solenoids are simply two slow to operate correctly with a full exhaust.

Hi all,

I am buying an Hallman boost controler in the end (didn't have too much time to look into it before). When it will be in the car, what values do i have to put in the PFC for boost settings and duty ?

Thanks

The settings wont affect anything if you are bypassing the factory solenoid and using a manual boost controller.

I agree 100% on the boost controller. Manual controllers work fine but can be a pain to set-up correctly and will be tough to dial them both in correctly.

The alternative is a electronic boost controller which can be adjusted from the drivers seat on the go between pulls to set-up (vs having to pull over...pop the hood, and adjust the controllers carefully remembering where your currently at being careful not to over adjust) Not saying it's overly difficult but I MUCH prefer the electronic controller I have now vs the manual controllers I ran for 7 years or so.

For a relatively inexpensive and simple model I like the Greddy Profec B (not the II model) They can be had for under $200 or right around that mark.

edit: one here for $170 which is a good deal if you decide to go this route
https://www.rx7club.com/3rd-generati...ez-dp-1054065/

This is not true the Boost setting will still regulate when you fuel cut due to over boosting so keeping a boost setting is still a good idea so you dont overboost in case of a failure

What will be useless now is the duty cycle since you are bypassing the solenoids

I only bought one Hallman BC as my boost pattern is 10-8-13. I went the mbc way over electronic because it is a PAIN for me to crawl under the dashboard upside down and doing electrics in general.
I got a lambda sensor and gauge i still need to wire but cańt find the motivation for it.

Thank you guys for all the input. It is very useful. I will let you know when the bc is in.

Considered that, but wasnt sure. Thanks for clarifying.

You need to remove/drill out the wastegate restrictor (it can either be in the hose itself, or its built into the nipple on the turbos if you have a later year car) - and add a manual boost controller in some form. (i have a simple needle valve)
Or you need to restrict your exhaust

Can someone let me know what should I expect with the following mod on stock non-seq twins.

Apex-i PowerFC with Commander
Apex-i AVC-4 Boost Controller
HKS Twin Power ignition
Greddy under drive pully kit
Peter Ferrell air intake with air dam
Peter Ferrell stock mount intercooler (Medium size)
Koyo Radiator
Bonez 3" down pipe
Apex-i N1 dual exhaust
Dual Earl's 25 Row Oil Cooler 42510 -10 AN
ACT Clutch
ACT Streetlight Flywheel
B&M Short Throw Shifter
Supra TT Fuel Pump
Secondary Fuel Rail with 1680 secondaries
850 Primary Injectors
Aquamist Water Injection Kit

Air-Con Removed
Rat nest removed