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Gtir Motorsport club » Tech room » Help and Advice » Boost tailing off

Boost tailing off

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1 Boost tailing off on 22nd April 2015, 7:57 pm

GTIR James


As some of you may have seen at bobs rolling road day my car has a problem with boost tailing off.

The car is fitted with a 2871r with ported wastgate.
Forge actuator with the strongest spring available
Actuator rod was set to nearly a whole hole over waste gate arm.
On the dyno it holds 1.65 bar upto 4,800 rpm then drops off to 1.4bar

I've tried adjusting the boost controller but it still tails of to 1.4ish bar

What are people's thoughts? I've heard of people having problems with these boost controllers not holding boost high up but perhaps the problem lies else where.

2 Re: Boost tailing off on 22nd April 2015, 8:07 pm

pulsarmoley

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How old is your forge actuator? Could it possibly be the spring has gone weak?


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3 Re: Boost tailing off on 22nd April 2015, 8:11 pm

GTIR James


Spring was new when the engine went back in Pete. Probs done a max of 3k miles

4 Re: Boost tailing off on 22nd April 2015, 8:17 pm

GTI-R US

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Management
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I would say its the boost control solenoid james (assuming no leaks are evident)

fit a dawes device and I bet you it holds boost just fine Wink


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5 Re: Boost tailing off on 22nd April 2015, 8:22 pm

pulsarmoley

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Have you got the red spring then? Might be worth testing the actuator with a hand pump?


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6 Re: Boost tailing off on 22nd April 2015, 8:49 pm

GTIR James


Yep it's the red spring Pete. I remember seeing a tread you put up ages ago about forge springs.
Where can I get a dawes device to try Bob?
Are they spring & ball?

7 Re: Boost tailing off on 22nd April 2015, 8:55 pm

pulsarmoley

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Yeah I tried searching for it with no luck so checked an old email from a guy at forge motoraport.


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8 Re: Boost tailing off on 22nd April 2015, 10:47 pm

GTI-R US

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I bought some in recently after being advised they are actually more stable than many electronic controllers even at high boost levels, cheap electronic controllers can cause all kinds of boost probs.
And yes they are spring and ball type
These are completely different to bleed valves which are known to be very unstable especially at higher boost levels


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9 Re: Boost tailing off on 22nd April 2015, 10:57 pm

MartyMG

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Check out EBay US. I bought my Hallman pro Dawes device from the states & its worked perfectly.

10 Re: Boost tailing off on 23rd April 2015, 6:14 am

grim_d

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@GTI-R US wrote:I bought some in recently after being advised they are actually more stable than many electronic controllers even at high boost levels, cheap electronic controllers can cause all kinds of boost probs.
And yes they are spring and ball type
These are completely different to bleed valves which are known to be very unstable especially at higher boost levels

Dawes device seem good but lack nice features of high end EBC such as start boost, gain and rpm offset. My E-01 actually has a boost/rpm data logging feature which can be very useful to tune boost curve.

With those features I could tune out my compressor surge without having to lower boost too far.

Dawes device better than cheap EBC no doubt there, simplicity can be king if only need basic control and no solenoid to die. Would only trust Greddy profec for EBC.

11 Re: Boost tailing off on 23rd April 2015, 12:07 pm

johnny gtir

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Apexi AVCR very good piece of kit

12 Re: Boost tailing off on 23rd April 2015, 12:09 pm

johnny gtir

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Try manual control and putting to much pre load on is not a good thing. After that I guess it's penny valve as we talked about James but try the manual first

13 Re: Boost tailing off on 24th April 2015, 5:38 pm

GTIR James


Thanks guys. I've got a dawes device on order so will update once that's fitted. Hopefully that will cure the boost issues

14 Re: Boost tailing off on 24th April 2015, 8:51 pm

gtir_pimp

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I had a forge actuator that wasn't very old and the spring was fooked causing the boost to drop off, maybe it was a fake

15 Re: Boost tailing off on 29th April 2015, 1:05 pm

Welling_AL

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Had a dawes device for years - really cant complain - holds boost well and takes the complexity of setting up EBC away - for a short term fix / explore of your issues James - it should do the job nicely mate.

16 Re: Boost tailing off on 29th April 2015, 1:43 pm

Mr B

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gtir technician
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Dawes style (ball & spring) are about the best principle for basic mechanical control.
If want specific boost mapping though you got to go ebc.
Most issues with them is they fitted wrong, set wrong (awful settings on some) or half fooked as old.
Do like the Greddy ones myself, used them a lot & only issues I had was due to other faults that needed rectifying or fact I set it wrong :-S

17 Re: Boost tailing off on 29th April 2015, 5:43 pm

shroom

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Haha even you get things wrong Mr B? Impossible!!!

18 Re: Boost tailing off on 29th April 2015, 5:54 pm

ducie54

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Not every boost controller can handle high amount of manifold back pressure. IMO porting the waste gate has made it harder for the actuator to hold the flap closed due to the larger surface area exposed to pressure.

I never got around to measuring back pressure on a stock manifold but once you increase above 1bar I would say the ratio of back pressure to boost pressure goes past the 1.5:1

Would be nice if Bob could test this on a customers car

19 Re: Boost tailing off on 29th April 2015, 6:03 pm

Spark plug spike

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Here is my graph from Bobs rollers with a Dawes device manual boost controller running at 1.1 bar of boost.

There are no spikes and it holds the boost steady.

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