BPU boost issue.

[Jack1998]

Afternoon all,

 

Just wondering if anyone has any thoughts on a problem we are having. 

After taking a friend out in my BPU supra, hes decided to do the same. We've set to upgrading plugs, full decat system, blitz boost controller, bigger front mount and associated piping, HKS FCD, the car already had a walbro intank pump. 

The moment we turn the boost over the stock 0.7-8 bar it quite violently bucks/spits. It feels like someone's jabbing at the brakes, really aggressive jarring, we haven't dared power through it just let off immediately. I initially thought coils, replaced all 6 to no avail then went with the 8 grade plug rather than 7's thinking they might not be cold enough but same story. 

The only other thing I can think is he's got the turbos running in parallel through re routing vaccum hoses rather than pinning them open. We haven't switched them back due to a dead Vsv and it's been running fine like this for years at stock power.

Appreciate any thoughts,

 

Thanks, 

Jack.

[Swampy442]

Sound like ignition cut/overboost, what boost did you get to? Plug gap out maybe?

 

[Mike2JZ]

Monitor AFR and check you arent leaning out

[Jack1998]

2 hours ago, Swampy442 said:

Sound like ignition cut/overboost, what boost did you get to? Plug gap out maybe?

 

Certainly feels like one, we changed the oil after a few pulls and it cutting as I was worried it might have still gone down the bores and contaminated the oil which sure enough it had, the oil was like water! 

Plugs are the BPU recommended iridium's so I assumed the gaps were left alone, it very mildly misfires at 0.9 bar, anything over than it snaps your neck it jarrs that hard 

[Jack1998]

1 hour ago, Mike2JZ said:

Monitor AFR and check you arent leaning out

We have thought about purchasing a cheapy afr to stick in and see what's happening, if we are leaning out is that correctable?  

[Mike2JZ]

The only instances I've seen of a 2JZ BPU leaning out hard enough to cause a cut in power was all related the fuel pump. So it was a fairly easy fix alll things considered. 

Worth checking that HKS FCD is set to around 9 on the dial. Any more than that can cause it lean it out more than required. 

[tomgeer]

I had similar sporadic boost issues when I took my car out of storage after servicing it. I would be looking at the coil packs, coil pack clips and connectors and the wiring, after that check the FCD settings and wiring to it. Check the spark plugs, if they are wet and sooted up they will need cleaning up too.

My issue turned out to be the coil pack connectors and I replaced all the coil packs with a set from Whifbitz which are good value for money.

[shaz2010]

Yes I had this coli pack connection were broken inside. Fixed the issue. 

[Jack1998]

15 hours ago, Mike2JZ said:

The only instances I've seen of a 2JZ BPU leaning out hard enough to cause a cut in power was all related the fuel pump. So it was a fairly easy fix alll things considered. 

Worth checking that HKS FCD is set to around 9 on the dial. Any more than that can cause it lean it out more than required. 

Well the fuel pump is of an unknown age so wouldn't do any harm putting a new one in. It is a bit gurgly and poppy on the overrun in normal driving too if that makes any odds. 

FCD is set at 12, possibly an amature mistake

[Jack1998]

6 hours ago, tomgeer said:

I had similar sporadic boost issues when I took my car out of storage after servicing it. I would be looking at the coil packs, coil pack clips and connectors and the wiring, after that check the FCD settings and wiring to it. Check the spark plugs, if they are wet and sooted up they will need cleaning up too.

My issue turned out to be the coil pack connectors and I replaced all the coil packs with a set from Whifbitz which are good value for money.

We have just put 6 new OEM coilpacks in, was yours the wiring going from the car loom to the connectors that had failed? If so how do I go about testing the wiring? 

[Scooter]

The connectors often get very brittle and crack/disintegrate when changing the bits you have. 

HKS FCD's get bad press so perhaps its fuel cut still? 

Didi you fit a restrictor ring in the exhaust? Isn't it the case that the boost controllers can only increase boost from a fixed level and not cap/reduce it? So when you say "turn the boost over" do you have a fixed boost with the controller off?

Does it run up the rev range on a low throttle ok ie when you keep the boost in check/at stock'ish levels? 

[Jack1998]

37 minutes ago, Scooter said:

The connectors often get very brittle and crack/disintegrate when changing the bits you have. 

HKS FCD's get bad press so perhaps its fuel cut still? 

Didi you fit a restrictor ring in the exhaust? Isn't it the case that the boost controllers can only increase boost from a fixed level and not cap/reduce it? So when you say "turn the boost over" do you have a fixed boost with the controller off?

Does it run up the rev range on a low throttle ok ie when you keep the boost in check/at stock'ish levels? 

Been messing today, turned the FCD to 8 and it boosts fantastic! 

He tore out the boost controller thinking it was the solenoid! So we rigged up a screw type one just to test. With the screw all the way out we got to about 0.9 bar, pulled really well and clean no smoke or juddering at all. I don't know if we hit the maximum boost for the screw controller as we couldn't get anymore. 

There is a restrictor ring in though now it's decat that whifbitz say is a 1.0bar restrictor, runs at 0.8 bar with no controller on at all. 

Shall be putting the boost controller back in and seeing if we can turn it up to 1.2bar.

[tomgeer]

On 4/30/2023 at 2:48 PM, Jack1998 said:

We have just put 6 new OEM coilpacks in, was yours the wiring going from the car loom to the connectors that had failed? If so how do I go about testing the wiring? 

Mine was coil pack connectors and brittle clips for the wiring to the coil packs.

 

[tomgeer]

4 hours ago, Jack1998 said:

Been messing today, turned the FCD to 8 and it boosts fantastic! 

He tore out the boost controller thinking it was the solenoid! So we rigged up a screw type one just to test. With the screw all the way out we got to about 0.9 bar, pulled really well and clean no smoke or juddering at all. I don't know if we hit the maximum boost for the screw controller as we couldn't get anymore. 

There is a restrictor ring in though now it's decat that whifbitz say is a 1.0bar restrictor, runs at 0.8 bar with no controller on at all. 

Shall be putting the boost controller back in and seeing if we can turn it up to 1.2bar.

The restrictor rings aren’t an exact science, they will vary a bit from car to car, as scooter says the electronic boost controller can’t turn down boost, only up it from the restrictor rings boost level, so you are on the right track upping the boost from the controller.

make sure the car has no misfires through the rev range, mine was missing still after I sorted the coil pack issue because the plugs were fouled up. Quick clean up and it was back to full boost and no problems.