ive got a 90 spec s2 and ive chipped it with a collins performance chip and its got a pipercross filter and 3 in scorpin full system on it, i fitted a -31 actuator and wound the boost up to 15psi and all was well, now after going to pod for the central day and going up the strip i noticed the boost peaks at 16 and then creaps bk down to 12 and holds.

my car is still fitted with the amal valve so i'm thinking it may be this any1 come across this issue b4 and what do you all think is the best way to get it to peak and hold 15-16psi?

cheers

 

Id probably leave it if your on standard intercooler?

 

If you are running that much boost on a standard cooler your act's will be through the roof mate

 

the act's aint too bad mid to high 30's on my readout,

so nobody got any ideas why its creeping bk down to 12 from peaking at 15-16psi?

i was thinking maybe the amal valve is bleeding off too much or the actuator isnt strong enough etc.

 

Weak act spring ?

 

i thought turbo engines naturally peaked and then settled down a bit?

 

Yes they do thats normal a 3psi drop is fine on a setup without an EBC, if you want to hold 15psi then you need to peak at 18/19psi.

 

Depends on what the predetermined limit that chip has been programmed. The boost you mention is stage 2 boost but as said thats the peak or "Spike" the held boost is what you have.


The amal valve won't bleed to much of as if it were it would be the opposite and you would run higher boost.

Martin

 

other option would be to fuck amal valve off and then take boost/vacuum pipe from just before throttle housing so the pressure drop over the intercooler is negated and the blower will 'try' make the boost your wanting

 

amal valve jets. a larger hole will reduce the peak. a smaller hole will increase the peak.

 

Errr... No! lol
RST ECU's do not control the boost, aside from shutting it down if it registers high ACT's or Knock (later S2's).
Could do that and it may remove the spike... but, it will remove the fail safe described above.


But as I said above this is normal on a RST with an Amal or bleed valve!

 

see my 1st post! dont recommend he does anything right now but we all know what its like!!

 

Yeah if he is on a stock IC then 15psi as you say is to the limit! Although he does say his ACT's are mid 30's which is fine, but holding 12psi they probably are! lol

 

id say you need a decent intercooler and a bleed valve ..... and is the actuator in good condtion as ive bought them from places like speed shack and they have been to weak.

most rs turbos will drop 2/3 psi sometimes a little more on a hot day as they hate hot weather

 

i've solved the problem guys thanx for the input, i sacked the amal valve off and got a -34 actuator and piped it direct from the turbo housing and it bangs straight up to 16 and stays put minty minty.

cheers

 

It works as I've done it before. open the hole slightly on the jet on W.

Think about what happens when you force pressurised air through a restriction into a lower pressure environment and the time it takes to equalise. Then reduce the restriction and think about the length of time it takes to equalise.

 

Karlos, after reading your reply again I think you need to do some further research into RS Turbo ECU's and amal valves.

 

I see what your saying with regards the Amal valve, by openeing up W no more is being bled off but it will equalise faster meaning a smaller spike
Post edited!

The rest of the post is correct with regards the ECU control.

 

define your term 'control' please. The series 1 ecu controlled the boost by varying PWM on the negative supply to the amal dependant on RPM and MAP input. It was not closed loop however and was only a mapped boost curve. This technology was carried over onto the s2.

You should not have any jets in the return by the way. only in compressor and wastegate ports on the amal.

 

Hmm.. are you sure?
I have heard this but I'm 99% sure Stu @ MSD wrote a article/post about MFI ECU's and they do not control the boost like that, the Amal is always open as long as it has 12v and an earth and makes a very loud click when it opens/closes you'd here it clicking like mad if it was PWM controlled and I have never heard mine (driving or on the RR) when I had one fitted.
AFAIK they are not like our ICV's which have varying degree's of open/close controlled by PWM, Amal's are either on or off

Ref the ports... I have never reallly looked at one closely as I replaced mine with a AVC-R and never tampered with it prior to fitting that.

 

[QUOTE=Karlos G;4882061]Errr... No! lol
RST ECU's do not control the boost, aside from shutting it down if it registers high ACT's or Knock (later S2's).

So how is over boost protection strategy if ECU does not operate it?

Martin

 

They close the Amal valve, dropping the boost on a stock car to around 3psi.

There is no staged boost control like you were saying in your first post, and the chip does not set the boost level, 99% of MFI RST chips have no overboost protection at all and allow for unlimited boost levels (in fact thats all they do!), controlled by your actuator preload and what you bleed off (bleed valve, EBC, etc).

 

I never said they had staged boost control, I said the chip will have the boost limit programmed and so it can not run higher than that which if the chip does not know this information how does it know the boost pressure AND drop to 3 PSI on a standard car?

Martin

 

Of course the ECU knows what boost pressure (manifold pressure) your running, thats what the MAP sensor is for lol
Stock RST's have a boost cut around 9/10psi, which is removed when you chip the ECU, some chips also have a different timing map like the Ahmed Bayjoo chips for example.

There is a difference between controlling the boost and being aware of it...

 

No by stage 2 boost I mean the pressure he is running "Stage 2 tune" AKA a 195 chip, nothing to do with staged boost control, I think this is where you are got confused.

I am fully aware of the MAP sensor's purpose, what I said in the first post was "The chip has a predetermined boost limit" which it has, generally speaking remapped chips still have boost limits, although can't speak for ERST.

Martin

 

Karlos, I'm 100% sure as i have researched it and have some documentation about it. Stu will confirm that also. You may however lose any control when using some chips. Stu's chips still retain the control.

If the amal valve worked in the way you described, you would have infinite boost until exhaust back pressure over came the actuator spring, and about 4psi in LOS.

 

Fair play DazC perhaps with a standard ECU this is the case and with Stu's chips.
You would not have infinite boost as the Amal is only bleeding off as much as the jet size allows.
Certainly with the chips I have used, Collins, Superchips, Ahmed Bayjoo, and Power Engineering, none of them have retained any sort of boost control that i've experienced.
Interesting to know though!

 

Ah I see what you mean, but as you say your not up on your ERST's, there is no 195 chip thats for the Fiesta RST's which have totally different management and are EFI for a start, 99% of ERST chips have no boost limit and only a few retain the ACT/Knock retard/boost cut, mostly it's all removed.

 

My wording again LOL, I dub the ERST stage 2 chip as 195 chip as this is the power it's claimed to produce the same where the name derives from for the FRST for the same state of tune.

Martin

 

What you'd do then is set the boost using the actuator and the boost characteristics would remain, just with a higher pressure. If the valve was either open or closed then you would get total bleed off or none at all. Disconnect the valve and you will get no (very little, usually 4psi on a standard car) boost. Wire it up live all the time and the actuator will not see any air as it will all be diverted down the R line to the metering unit, hence infinite boost. It fails safe so air is ported to the actuator set to lift at 4psi and is then raised to 7.25 via the PWM signal bleeding off the actuator signal.

On my own car I set the actuator to lift at 1ps and the amal valve then increased it to peak 16 and hold 14. I then turned up the pre-load at a later date and the boost increased linearly (e.g. peak 18 held 16, peak 20 held 18).

On the other chips, they just switch the amal valve open to port air from the C port to the W port (switch off the amal valve). The jets will still affect the peak and hold characteristics but to have any form of boost you'd need to add a lot more pre-load to the actuator as no bleeding off is carried out by the valve anymore.

 

hey karlos,i do agree with what you say.im using power enginnering chip and that simply removes the limit.I have not found a limit as of yet,even at 22Psi.Guy said yeah this just takes the boost limit away.plus im not using amal valve.