RB20 high RPM breakdown please help!

[kawasakirider]

RB20 high RPM breakdown please help!

Hi everyone, so I've got some issues with a project car I picked up and I'm hoping someone can help diagnose it with me, I'm well and truly out of ideas. 

So, I bought a super clean 180sx with an RB20 conversion. It was a non runner and I decided to do it up (why?! lol).

Basically the car hadn't run for years. I compression tested it and that was fine, then realised there was no fuel at the filter, so I figured I'd buy it as it was likely a dead fuel pump. 

Long story short, the pump was messed up. I dropped the tank, drained it and did the following: 

Added a new Walbro 255

Got the injectors cleaned and flow tested (they were stuffed but came back to life and flowed almost identically).

Sprayed some cleaner in the fuel rail and FPR.

This got the car running. 

It wouldn't boost well so I thought the wastegate may have been stuck open (it had a high flowed T04 on it with a Nitto 40mm External gate).

I took that off and found the gate was fine, but the turbo's rear housing had a crack in it and was no good, so I bought a T04E for it and had the dump pipe flange matched to the new turbo. 

The new turbo has a smaller CHRA than the old one. 

So I put it all back together last night and it's laggy but it wants to die high in the rev range from about 6,000 RPM. 

If I hold my foot into it, it will hesitate for a bit at that mark and then clean up and boost to 9,000.

Now please, I realise RB's have a rev limiter. I'm not sure if the tachometer is accurate, it's likely out. 

So after that I went and bought a set of spitfire coils and I'm getting the exact same issue.

Revs to mid-high RPM and as boost starts to really come in, it dies. The gauge only sees 3psi max. I've put a different gauge on to confirm this. 

So in summary: 

* New fuel pump
* Injectors cleaned and flow tested 
* New fuel filter (admittedly I started the car with the old filter after I ran fuel through it into a bucket looking to clean the lines, bit of a brain fart but I doubt that hurt it)
* New T04E turbo running gate pressure on the nitto external gate 
* New splitfire coil packs 
* New spark plugs BCPR6ES at .8mm

So where I'm at now I'm just completely scratching my head. 

If it was the AFM I'd assume it would rev poorly throughout the rev range. I have a mate who says he had the same symptoms I'm having from an AFM, so I may change it. 

There's a ticking sound  from the engine bay that I've isolated to be injectors/fuel pressure regulator. Could the fuel pressure regulator be shit? The injector guy told me it was working. It's just the stock one. 

The only other thing I can think of is the Walbro fuel pump is not getting enough power. I've checked it at idle and according to my multimeter it's getting 11.9-12-ish volts. Haven't done a voltage drop test yet. 

My thoughts are: 

Hard wire fuel pump to battery and just use a switch so it's got constant power. 

Add an adjustable FPR. 

Maybe switch igniter, AFM, etc.

If anyone has any ideas, I'm all ears and would really appreciate it. I've read a bunch of tech articles trying to chase this and I am 100% over it. 

I know it's something simple but it's eluding me.

The only other thing I can think of is the turbo is too big for the fuel system but I doubt this is the case as I'm only seeing low boost and after the hesitation it goes for the last tiny bit of the rev range. 

Any help is greatly appreciated!

[R_34]

Did you checked boost leaks ?

Is the ECU still standard ? STD injectors and AFM ?

Is the timing belt correctly installed ?

Is the timing set to 15° ?

As for the rpm reading it may work but still read 50% higher than it should, you'll need to turn the pot at the back of the tachometer almost fully counter clockwise.

Redline of the RB20 is 7600rpm with a factory ECU.

[kawasakirider]

Yep, no boost leaks. 

ECU is standard AFAIK

AFM is a pink/red label - gave it a spray with contact cleaner last night and the issue became worse but don't think it was fully dry.  

timing belf is correctly installed 

could this be a CAS, AFM or igniter issue? 

Cheers 

 

[GTSBoy]

Big turbo.  Standard ECU & AFM,  And we're wondering where the problem is?

[Kinkstaah]

Yep, as soon as I heard T40E running 3 psi (??) on standard ECU I was about to post something similar to the above.

It could be a CAS, AFM, or Ignitor issue, but if you have a standard ECU, anything other than a standard turbo is going to cause you massive grief in one way or another.

I'd be putting a standard turbo or something standard sized (rb25?) and get as many things as possible close to stock as you can, and then go after troubleshooting things. With that setup there's just almost no way you could get it running well in any scenario, even if every component was setup right.

[iruvyouskyrine]

What these guys said above. The only hope you have of getting it running somewhat well in its current state is to take it to a reputable tuner (even the they will make you get a NIStune or PowerFC at an absolute minimum).

If you want to fix it yourself then as they said get everything as close as possible to standard, most importantly the turbo.

Basic things to check that you didn't mention
- check mechanical timing
- check electrical timing
- check condition of wiring loom (main loom and coilpack loom)
- try known working CAS and Igniter

[NickRB20]

13 hours ago, kawasakirider said:

AFM is a pink/red label

 

Shouldn't it be a green label for an RB20?

[kawasakirider]

Well, I direct wired the fuel pump with a relay this evening and the car is fine now  

Doesn't break down under load, runs great. 

The walbro 255 wasn't getting enough power through the factory loom! 

Thanks for the help everyone. 

[kawasakirider]

It's also running gate pressure at the moment at about 7psi (I wound the spring on the external NITTO gate back when I fitted the new turbo). I'll fit a boost tee at some point.