Boost controllers - adjusting

[Prof]

Hi chaps - time to pick brains - have searched the forum, and apart from some figures from Shaun for twin turbo\'s on FD, I can\'t find too much on this - same over on rx7club.
 
OK - fitted a boost controller - Profec B Spec II to the old vert just under a week ago, and dialled in some really low numbers so that I did\'nt go mad with boost whilst finishing the running in - no probs there.
 
However, now I can let the car run longer legs so to speak, and push the revs out - the boost is stable until about 6000 RPM and then just starts creeping up until the Profec limits it
 
I tried the following settings to start with:
 
10% Duty
10% Gain
0 for Set Gain (Start boost)
Warning 9.5
Limit 20
 
With these settings I was hitting 12PSI on occasions when revving past 5700 RPM
 
I tried
 
15%
10%
6
9.5
L 20
 
and the boost peaked at 14.7 - way too high
 
Currently I am running
 
10%
13%
6
9.5
L 20
 
but at the higher revs I am still getting creep until the limiter kicks in.
 
So the question:
 
Has this got anything to do with the street porting and the much freer inlet ducting I am now employing ?
 
I want to get the LO boost setting so that I can have quick turbo performance on the stock ECU - and set slightly higher for the HI setting for when I have the other mods on.
 
Any ideas ?
 
Cheers,
 
Prof. :cheers

[nikp]

As far as i understand reading the instructions, the Gain needs to be raised if you are getting boost creep. But I can\'t get mine to give me stable settings for the life of me, so i may not be the best person to offer advise on it!!

[antnicuk]

the controller can only do so much to prevent boost creep, the rest is down to the wastegate,  if the controller is allowing full pressure to the actuator then it cant do any more,  IIRC you already have a ported w/g, another option is to make a slight restriction in your exhaust somewhere, maybe a middle box or a small bung or sleeve in the tail pipes if possible, that will keep the low end pick up and reduce the creep.  Otherwise try and reduce the gain which will bring the turbo in slower and later but may give the w/g a head start on by passing the gasses.  

I had boost creep issues on mine and it was the bend in the dump pipe not being smooth enough (external type though)

[antnicuk]

As far as i understand reading the instructions, the Gain needs to be raised if you are getting boost creep. But I can\'t get mine to give me stable settings for the life of me, so i may not be the best person to offer advise on it!!

i have found that the cheaper wastegates and the pipe work to it are more the cause of the problems than the boost controllers, just my experiences though

[Prof]

I guess I wasn\'t expecting the ported engine to be able to overwhelm the turbo so easily.  It\'s possible I could get it to stabilize at higher boost values, but without the fuelling mods I don\'t want it to settle up there !
 
It was stable at spring only boost (compressor output looped back to wastegate actuator) so I am reasoning that I must be able to get a set of stable values for 8-9 psi boost for my LO setting.

[Brett]

I\'d agree - I was running with a home made bung in the exhaust until I had the ECU to cope with the boost :yes

 I amde mine by cutting off the tube section of a standard bung, welding on a 2.5" x 12" steel tube, I then folded the end of the tube to get a solid end.  Once this was done I drilled about 300x5mm holes in the tube to get the surface area for the gases to flow through.  It kept the boost down to around 12psi, but it certainly makes the response seem a little strangled!

[antnicuk]

I guess I wasn\'t expecting the ported engine to be able to overwhelm the turbo so easily.  It\'s possible I could get it to stabilize at higher boost values, but without the fuelling mods I don\'t want it to settle up there !
 
It was stable at spring only boost (compressor output looped back to wastegate actuator) so I am reasoning that I must be able to get a set of stable values for 8-9 psi boost for my LO setting.

If you had stable boost without the boost controller at High RPM, try running bigger diameter vacume pipes to the actuator/boost controller, it may help if the actuator has to be fully open to flow enough gases through it.

Your turbo is only a little bigger than stock and would probably be a better upgrade on the stock engine.  My TII engine is only mildly street ported (at the moment) and at 0.9 bar (12.5 psi ish IIRC) i have 340 RWHP which is about double the stock car and thats with a small turbo with virtually no lag and low comp rotors which would give less power than stock ones. A little porting goes a long way.....

[FD3UK]

The first thing to do is switch off the Boost controller and see what boost you make. If you are still creeping above your target max at higher revs you will have to improve waste gate flow first. Once wastegate keeps boost below your target max, reintroduce boost controller and adjust settings to achieve your desired boost level.

[Prof]

The first thing to do is switch off the Boost controller and see what boost you make. If you are still creeping above your target max at higher revs you will have to improve waste gate flow first. Once wastegate keeps boost below your target max, reintroduce boost controller and adjust settings to achieve your desired boost level.

Stupidly, I never thought of that !:2Rolleyes
 
I will give that a try - makes sense to do this, and then if necessary, introduce a bung or somehow restrict exhaust flow before I get the other mods online.  I don\'t want to be blowing up the engine :2eek
 
I must say this has the \'feel\' of being a very fast car... :cool

[Prof]

Took Kev\'s advice and did a run with the unit OFF - pulled over and checked - logged 11.3 PSI peek, with the Rev\'s just under 7000 RPM.
 
Set the LO settings to
 
8% Duty
15% Gain
5 PSI start boost
9.9PSI warning
Limit 20%
 
Did another WOT run in 3rd - managed 6700 RPM - and checked the values when I got back to work - peaked at 11.3 again. On the run I noticed the mechanical Boost gauge held rock solid at 0.6 BAR (8.8 PSI) which is exactly the same as a stock Tubby II.  Did not notice the boost controller flashing red, so the spike is very quick when it happens.  The boost comes on quickly and is much more controllable at the top end. Pretty happy with those settings for the LO setting.
 
Cheers guys for your input.:Typing
 
Prof. :cheers