Hi guys, on my '04 S (163cv) i put a boost gauge, on forum i saw that the S pressure is 0.8 bar, my gauge stop to 0.6/0.65, i check pressure in all the rpm range;
on my car i have the one ball mod; there something wrong on my car or is a bad gauge?
Thanks

Hi guys, on my '04 S (163cv) i put a boost gauge, on forum i saw that the S pressure is 0.8 bar, my gauge stop to 0.6/0.65, i check pressure in all the rpm range;
on my car i have the one ball mod; there something wrong on my car or is a bad gauge?
Thanks

.8 bar is right at normal for a stock S.

maybe there is something wrong on my gauge...

another guys of my club has another gauge and result is the same...:mad: :confused:

maybe there is something wrong on my gauge...

another guys of my club has another gauge and result is the same...:mad: :confused:

Ahh...I think I understand now.
You're reading .6 on your car.
Yes that's low. Where are you picking up the reading from? Where is the hose for the gauge connected to the motor?
A bad seal on a hose fitting could do this, leaking IC boots and a few other things can cause this.

i connect the gauges under the IC, i found the fuel pressure (i think) wich is connect to the car with an L conector, in this L i put a T that goes to the gauge;
all the tubes are fixed strong to the T

i connect the gauges under the IC, i found the fuel pressure (i think) wich is connect to the car with an L conector, in this L i put a T that goes to the gauge;
all the tubes are fixed strong to the T

That bit sounds right.
I'd next check the IC boots and one poster actually found the IC horns had a gap from them not being tightened properly.

After that I'm out of ideas.

i check it but there are not gap!:confused:

i check it but there are not gap!:confused:

The last thing I can think of is a slipping belt.

If that isn't it I'm tapped out.

could be the oneball mod. Lower backpressure would mean the gas flow is better, and might result in less pressure (but not necessarily less power)

...severely clogged airfilter.? This will stretch the air entering the SC at WOT to below ambient . Less pressure entering SC= less pressure exiting it. The stock ducting to get air to the filter lets crud in at an alarmingly fast rate, Even cars with a couple of thousand miles gets the filter filthy.
Best Regards Roland GTT:smile:

i check pressure with the stock in box filter and with a bmc cone:red:

i've heard that the stock boost pressure for a MCS is about 10.5 psi, which is 0.72 bar, no?

if it's 0.72, maybe with one ball .65 is true!:red:
thk!

Your SC bypass valve may need to be fine-tuned. If the butterfly doesn't close
all the way then you will lose boost pressure through the gap. Hmm, would this
be another occasion for the phrase, "Mind the gap"? :tongue:

Your SC bypass valve may need to be fine-tuned. If the butterfly doesn't close
all the way then you will lose boost pressure through the gap. Hmm, would this
be another occasion for the phrase, "Mind the gap"? :tongue:

this is something that could definately be the cause. I forgot to mention it :)

Your SC bypass valve may need to be fine-tuned.

please what do u mean whit SC bypass?
What for u i have to tuned?
thanks:cool:

...interesting thread guys... one I am asking myself now I have a boost gauge fitted!

My MCS builds boost to around 5psi very easily (and quickly) but to reach full boost, it takes WOT and a bundle of revs.

Is there a graph of the shape of the boost (against revs) that we should see?

DJ

...interesting thread guys... one I am asking myself now I have a boost gauge fitted!

My MCS builds boost to around 5psi very easily (and quickly) but to reach full boost, it takes WOT and a bundle of revs.

Is there a graph of the shape of the boost (against revs) that we should see?

DJi'm no scientist but there has to be an inherent wall in the design then as the cam timing becomes optimal boost becomes harder to build as flow becomes better . starting it seems at about 4000rpms so i wouldn't worry if it kept building i'd be scared. is there a blow off type deal on these cars? so we don't pop a head? or does the size of the super charger max out preventing this normally?

please what do u mean whit SC bypass?
What for u i have to tuned?
thanks:cool:"detroit tuning"

i'm no scientist but there has to be an inherent wall in the design then as the cam timing becomes optimal boost becomes harder to build as flow becomes better . starting it seems at about 4000rpms so i wouldn't worry if it kept building i'd be scared. is there a blow off type deal on these cars? so we don't pop a head? or does the size of the super charger max out preventing this normally?

yep, flow will be better when cam timing is optimal, but the thing is, the SC gets more power to force air in as the revs build, so even though the head is flowing better, the SC is flowing more, so it does still build a little bit of boost, but not much more than what you had at 5kRPM.

We do have a bypass valve. It sits between the post-IC horn and SC inlet plenum. But it doesn't vent boost pressure when the throttle is hard down, if that's what you're asking. Turbos can do this, but not directly. Instead of releasing a hard-earned dense intake charge, it slows down the turbos by venting some of the exhaust gases away from the exhaust turbine.....

yep, flow will be better when cam timing is optimal, but the thing is, the SC gets more power to force air in as the revs build, so even though the head is flowing better, the SC is flowing more, so it does still build a little bit of boost, but not much more than what you had at 5kRPM.

We do have a bypass valve. It sits between the post-IC horn and SC inlet plenum. But it doesn't vent boost pressure when the throttle is hard down, if that's what you're asking. Turbos can do this, but not directly. Instead of releasing a hard-earned dense intake charge, it slows down the turbos by venting some of the exhaust gases away from the exhaust turbine.....yeah the by-pass if i understand is just to fissillitate (i know i can't spell worth a sh$t ) fuel economy by not using boost until a pre determined rpm (say around 2800). but yeah the question was directed at the blow-offs used by turbo cars.to avoid too much boost .but it's possible the 45 doesn't make enough boost to be a danger. wonder what the testing on the 62 will bring?

yeah the by-pass if i understand is just to fissillitate (i know i can't spell worth a sh$t ) fuel economy by not using boost until a pre determined rpm (say around 2800). but yeah the question was directed at the blow-offs used by turbo cars.to avoid too much boost .but it's possible the 45 doesn't make enough boost to be a danger. wonder what the testing on the 62 will bring?

our bypass valve is throttle controlled (sort of). It will slam shut under WOT, no matter what revs you do....

The thing you speak about with turbos is called a wastegate. it diverts exhaust gas away from the turbines to slow down the turbines, in order to keep the boost at a sane (and preset) level.

Turbo, and supercharged, cars both also have bypass valves that release boost pressure, but only when you back off the throttle, so that the dense (and high energy) intake charge doesn't cycle back into the turbo/supercharger blades, which puts a lot of stress on the blades themselves. Basically the high pressure air within the intake manifold will cause problems,(cos the turbo/supercharger is trying to make a dense flow of air, but when you shut the "hole" that its trying to force air through, the only way it can escape (and it tries very`hard) is back through the blades). So that's why we have a bypass valve there, to make another "hole"

So could we fit a blow off valve? or is it a waste of time?

So could we fit a blow off valve? or is it a waste of time?

I want to know too...... anyone?

no-one's tried it AFAIK. Why don't you give it a go. I can't imagine much going wrong, i think the worst thing that could happen is you throw a CEL or SES light.

As Stooge has pointed out its as much about air flow as it is boost pressure,both are linked , the charger will put out a fixed amount of flow at any rpm it is directly proportional ie if you double the rpm of the engine and hence charger you will double the amount of air flow (the charger is working as a geared pump)this is in an ideal situation where the flow is going down a pipe of a fixed size into a fixed resistance. the engine is the resistance but it varies due partly to the cam opening/closing the valves at its timing points hence the flow is altered and hence the pressure is also altered. the same is true by altering the exhaust/manifold/head/valves/cam to flow more air you may see a drop in boost pressure although an increase in power because the resistance has dropped and the FLOW has increased more flow -more oxygen-more power.(and heat) The charger runs a maximum flow of about 330 CFM cubic feet of air per minute without overspeeding it (not a great idea) and the air into the charger is restricted by the throttle which is before the charger ,hence larger throttle bodies (the stock one can only flow about 260 bhp) there is also a restriction due to the inlet pipe just after the throttle being a crap design ,hence modified pipes, there is also a restriction in the pipes and air filter and box , hence free flowing filters/induction kits.
But ultimately it is the charger itself that has a limit (330 cfm ish ) and a pressure limit at which it will become very inefficient. That is why I am shortly launching a new charger which will produce over 500 CFM and run comfortably 22-24 psi and remain within its efficiency range, it should make 325 bhp, which I will limit to 275 due to engine constraints and cost
Wrappa your 0.65 bar pressure may be correct with the one ball fitted,but a quick check on the plugs to make sure they are seated properly and the intercooler rubber boots may be beneficial

i think the worst thing that could happen is you throw a CEL or SES light.

What do these lights mean? is it bad or is it an annoyance?

the lights mean that basically the car isn't running the way it should. It may or may not throw the car in to limp mode, which basically limits revs, power, the lot until you fix it

is that something i'd be able to fix myself with the right codes or is it a dealer thing?

well the only way you could fix it is putting the car back to stock. So you can do it yourself