From my understanding the boost controller uses a solenoid to regulate the pressure being sent to the wastegate. This allows the boost controller to control the opening of the wastegate and thus control boost. I thought the solenoid must be switching very quickly between boost pressure and atmostpheric or vacuum to give an average pressure to send to the wastegate. The duty cycle of the solenoid, the proportion of time open vs closed, would determine the avg pressure. Its the same principal as an injector. The reason I wondered if it had a vacuum line is that unlike an injector the pressure in the boost line to the wg has no venting route. Thus I thought that the solenoid would switch quickly between pressurisng and venting the boost line to atmosphere or vacuum.
Hard Pipe To Intercooler Hoses
- Thread starter barks944
- Start date
ORIGINAL: Diver944
.......At our weedy boost levels on 3L cars we could hold our pipes on with blu tack []......
Perhaps you should have used that at Donington then [
] []Boost pipes do blow off. Just because someone hasn't had it happen to them (yet) doesn't mean it doesn't. The original clips, the thin ones that loop over and are held with a nut and a bolt, were great when they, and the hoses, were new. When new they no doubt worked very well as their thin section would cause a nice ridge on the inside of the rubber hose. The hoses harden with age and the clamps stretch (some of mine the shoulders eventually met). Left undisturbed they no doubt continue to hold. Unfortunately, as the boost pipes have to come off to change the belts, this isn't an absolute option.
Silcone hoses are braced internally so don't ridge the same way as rubber, they do have nice grippy surfaces though. This being the case they work best with nice broad clamps getting as much surface contact as possible.
I am not familiar with Marks toothed clamps but wouldn't be keen on using them on my car for fear of them damaging the hoses. Just my personal thoughts.
MarkK
Active member
Tried new original clips when the car was put together,for most situations they worked but not always when the car was being driven really hard,the new ugly clips solved the proplem by just replacing a couple of original clips,they are just a fraction wider,they clamp harder,no damage to the original fitment intercooler rubber hoses over a period of years,they really work it was just a sharing of ideas to anyone running high boost pressures like Pete that had had a blowoff,one thing against them is they don't look over pretty but they do the job.
vitesse
Active member
My BMW 530D Touring has on odd occasions blown off the boost hose to the intercooler at the the turbo end where the "z" rubber hose joins the metal pipe.All turbos release a little oil into these pipes & if they are not cleaned really well ,both inside & outside prior to refitting,they do blow of again under high boost conditions,even if the hose clamps are tight.My engine has been remapped so in Steptronic it can over rev & also over boost particularly if I totally disengage the DSC button(Hold in for over 15 secs until the warning light goes out again).
Since I started looking at these problems,myself, I cleaned the pipes well,slightly abraded the metal pipe ends to get a better key & used a new clamp,I haven't had any further blow offs.
Since I started looking at these problems,myself, I cleaned the pipes well,slightly abraded the metal pipe ends to get a better key & used a new clamp,I haven't had any further blow offs.
sawood12
New member
ORIGINAL: barks944
ORIGINAL: sawood12
Tom - regarding EBC's one of the finest ones you can buy and is well used and known in the 944 Turbo community worldwide is the Apexi AVC-R [
Hey Scott, thanks for the suggestion. Ive had a look at the AVC-R and its a pretty slick bit of kit isnt it. I like the idea of RPM, speed and gearing based boost control. I remember you saying that the promax chips couldn't handle changing boost levels. This would imply that I can only set the AVC-R to the current boost level (1.2 bar wasnt it) and cant play about with all the other clever stuff. Is that right? Know of any chips that can handle changing boost levels?
Tom, yes, the Bosch Motronic doesn't map for boost level so the maps assume a certain max boost pressure, therefore with the AVC-R you'd need a True MAF piggy back control system like Vitesse (the only true MAF piggy back system I know of) or a MAP system with Standalone or MAP piggy back. So you'd have to use the AVC-R in simple EBC mode rather than utilising all its bells and whistles. Once you have true MAF or MAP you can vary the boost level to your hearts content and be ensured of getting the right fuelling.
The current boost level on your car is 1 bar/15psi.
The new Vitesse V-Flex uses MAF for fuelling and MAP for ignition timing, which is a system used by most modern production turbocharged cars. The stock Motronic wont vary ignition timing according to boost pressure, again it will be mapped assuming a fixed max boost pressure. The KLR uses a pressure line to sense for overboost conditions so it can to retard the ignition timing, but the DME has no idea what the boost pressure is at any point in time.
As to what the Apexi will do for your car. Well if you study the rolling road printouts for your car you'll see that the boost pressure builds to the max boost pressure at about 3krpm. However the max boost pressue isn't held for any length of time - it starts to tail off linearly to about 0.7 bar at 6500 rpm. That linear tailing off is due to the MBC bleeding boost. Basically the MBC is a spring loaded valve so cannot actively regulate the boost pressure as the RPM's rise - i.e. it is not a closed loop control system. The Apexi is so will attempt to hold the max boost pressure for as long as the turbo can flow enough air to maintain the boost pressure as the revs rise. There is much speculation as to what the flow capability is of the K26/6, some say they are getting 15psi to the red line, some say it can't hold pressure to the red line. One thing is for sure - even if the Apexi can hold max boost for 1500 - 2000 rpm before the turbo runs out of puff then you will definately feel a huge difference through the seat of your pants and I reckon you'll be knocking on the door of 300bhp - if not exceeding it depending upon how long the max boost pressure can be held.
The only reason I was reluctant to fit is was because I was worried about the stock injectors delivering the fuel with all that extra air at higher RPM. There are people running stock injectors with 1 bar boost and Apexi's - I think Andy at Promax was/is running his 250 turbo upto 1.2 bar on a Promax L2 kit with an Apexi on stock injectors with no probs, so maybe I was being super cautions. In anycase my plan was to install larger injectors with the CEP fuel rail kit (still available for sale by the way but going up on Rennlist during the next week) and a Vitesse MAF kit so I elected to wait.
In any case with the Apexi you can set a boost profile according to RPM so you could programme the same boost profile the car has now (i.e. tailing off to 0.7 bar at red line) then start to gradually move the gradient out so you get an increasing flat spot where max boost is being held. The Apexi can tell you what your injector duty is so as long as you keep an eye on that then you can gauge how well the stock injectors are holding up.
Presumably the car is mapped to account for this tail off in boost pressure then? So if I increase the boost by the intallation of the apexi then wont the car run lean? How does the car handle the injection where say im at 4000rpm off boost and on boost? I was wondering if it was the fuel pressure regulator, as if you are feeding it boost rather than vacuum then the fuel pressure in the rail would increase with boost and this deliver more fuel.
sawood12
New member
Not sure Tom - On the basis that at WOT (or even about 3/4 of WOT) the fuel system is working flat out all the time (i.e. not mapped) so you will likely be running rich and potentially leanin out a bit at the higher RPMs. Again you'll have to look at the rolling road print outs as one has a Lambda line - you'll see that the line is pretty jagged so I don't think it is that clever. You could be right about the FPR - I'm not 100% sure, I always thought that the FPR simply maintains the fuel pressure at 3 bar above manifold pressure - as the boost pressure rises the FPR will regulate fuel pressure to maintain a 3 bar differential. If not then the fuel pressure differential will drop and you'll lean out.
The FPR is a diaphragm valve with a spring and pressure line connected to it. Its very similar to a wastegate, varying the pressure to the diaphragm in the FPR will change the pressure that the FPR regulates to. If its a boost line then increasing the pressure will force the valve to stay shut more thus increasing the pressure in the fuel rail. This is the only thing I can think of that will add more fuel to the engine when its on boost. Otherwise it would just inject as if its off boost all the time and thats clearly not the case.
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