Boost control advice/help needed

[user515]

I had my GReddy Profec B Spec II boost controller fitted last weekend, and I am having some 'fun' getting it running how I want.

When it was first fitted, I couldn't get it to hold boost steady at all. When I put my foot down in 3rd gear at 2500rpm for instance, it would spool to 1 bar by around 3k, and max boost (1.1bar low setting, 1.4bar high setting) by circa 3.5k, but then boost was fluctuating by around 0.1bar until 5k+ when it would become more steady. Whilst this was happening, I could feel the car 'lurching' until over 5k when it would start to pull smoothly. I was also having to turn the 'set' level very high to achieve decent boost levels. Having done some searching on evolutionm.net & had a read through the manual, I realised that it could be down to the spare port on the solenoid having the cap left in when it should be removed. Sure enough, it was, and having removed it, the car now pulled much better, with the 'set' level being much lower to achieve the required boost levels.

However, it still isn't perfect by any means. The boost remains fairly steady (from watching the gauge & the controller display), but from when the turbo spools up at 3k right through to 5k, the car feels somehow flat, and I can feel it it sort of hesitating. I have tried reducing the gain, and the adjusting the set-gain (start boost), but I can't quite eradicate the problem. After 5k it pulls smoothly, and very hard, overall the car is much quicker than before, but it's bugging me. I'm not getting any spike, the boost stays constant & pretty steady on the gauge from 3.5k onwards, although in high setting it backs off from 1.4 to 1.3 bar at around 6k.

So, I'm thinking it could be:

1) Surge. Could the standard downpipe & elbow be causing this?
2) The standard dump valve leaking? (doubtful, certainly in low setting)
3) Detting? - Hope not!! :shock:
4) I can't set up a boost controller for shit.

The problem only seems to occur at lowish revs with large throttle opening.
Help please...

The spec of my car is:
Ralliart sports ecu
HKS panel filter
3" decat, fujitsubo cat-back exhaust
Walbro 255lph fuel pump
GReddy Profec B Spec II boost controller
Denso iridium plugs.

I'm taking it to WRC's rollers a week on saturday, but would like it running nicely by then...

[dral]

So the gauges are reading steady boost at the expected pressure, but the car feels hesitant up to 5000 rpm?

Does it seems to pull less strongly than before the controller was fitted?

I'd guess if the boost is showing the right pressure that the controller is working fine so you need to look else where. Where are the boost controller and gauge reading the pressure from?

The only thing that i can think of at the moment is that i have read of a problem with the walbro overfuelling, that would reduce the power at the lower end, but i thought that was more a problem with early evos to be honest. A pressure reg should help if that is that case though.

You could try disconnecting the recirc pipe on the dump valve, that would tell if you had a leak, but even a 1.4 bar i think you're right in thinking it'd be unlikely.

Not much help i'm afraid, i'll see if i can find out any more though.

check for vac leaks, exhaust leaks and make sure there are no kinks in the vac lines. thats usually the problem. hth. :muhaha:

[user515]

Thanks Nik. It's hard to say if the car is actually flatter below 5k than before, I suspect not. The car seems to push well when it comes on boost at around 3k, then it feels sort of flat or hesitant from then up to 5k. I tried dropping the set-gain lower this morning, but it made little difference. I got a mate to drive the car while I adjusted the controller and it seemed ok, I could feel no surging from the passenger seat. But once I was driving, I could feel it. Don't get me wrong, the car is definitely quicker than before, I had it up to 140 the other night in quite a short distance, it just doesn't 'feel' like I think it should. :-?
I've attached a pic of where the boost gauge is 'T'd in, the controller is reading from the line that runs to the boost gauge ('T'd in inside the car.) Is this right?

[dral]

Does it do the same at various boost levels? As Novtec says a restriction in the pipework somewhere could result in less air getting to the block at the same boost pressure. And from that i'd say your controller is doing it's job properly. I'd guess the small control lines must be fine as you're reading the right pressure, but there maybe a leak or blockage between your intake and the manifold? Have you had a good listen to the engine for leaks yet?

The boost is being measured directly from the manifold, and the gauge and controller are taking it from the same place which does look fine to me.

I'm pretty much guessing here, based on my very basic understanding of turbo engine theory.

I've just been for a quick run in my car, which is pretty much as you're bar the ECU, and it does pull evenly from 3K. Sorry i can't be any more help.

[user515]

Well, I went to WRC Tech this morning, it's all sorted now. The boost was holding just fine, but power was way down, somewehere around 290bhp, and it was running lean, I mean dangerously so. :shock:

Fortunately, Chris spotted that the pipe to the fuel pressure regulator had been knocked off...

It now pulls much, much better, the mixture is fine (rich), and it produced decent figures at 1.45bar. They reckon with a downpipe they could Ecutek my car to around 370bhp/360Ib ft. Game on... 8)

[madmat]

Good figures mate, well pleased for you 8)
Iain didnt knock that pipe off did he??

[user515]

Originally Posted by MADMAT

Good figures mate, well pleased for you 8)
Iain didnt knock that pipe off did he??

I think he may have, it was hesitating when we were initially setting up the controller... but I don't know for sure, obviously. :shrug:

It flies now though, I hit 150mph in no time on *ahem* a private stretch of road on the way home. :muhaha: I've used a whole tank of fuel today! :shock:

Oh, I think I'll have that HKS front pipe of yours mate, want to PM me how much you want for it? (including fitting) Cheers.

[madmat]

Do you still want the rod bolts changing?

[user515]

Originally Posted by MADMAT

Do you still want the rod bolts changing?

I'm not going to bother to be honest Mat. I've been searching the MLR, and there's no conclusive proof either way. I'm not so sure they need doing, I reckon it's high revs that are the killer, not so much the level of boost. I can't find any examples of the bolts letting go, and some people reckon that changing them via the sump can do more harm than good. I know you've done yours, and it's been fine, but I'm *fairly* happy that mine'll be ok. I know this is against your advice though, so on my head be it... :shock: