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Discussion Starter #1
Hello,

I am thinking of upgrading my 155 Q4's breathing system. BMC Carbon dynamic airbox and a Revotek dumpvalve is on the shopping list, but when looking under the hood, there are so many hoses going around that gets me confused. :confused:

Ones specific are the hose from valve cover to airbox (via cylindrical "thing" behind the battery) and another that runs from under the metal tube (before the throttle body) to a switch of some kind (between the metal tube and valve cover.)

Can someone explain the purpose for all these hoses or point me to a place where I can study myself. Pointers to places where to obtain service manual or some other good literature, are also appreciated very much.
 
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The airbox is not complicated to replace by a cone. The difficulty I found is to make some kind of 3" metal support to keep the cone in place. But not a problem at all.

A little bit more complicated is the dump valve issue. You have to disable the induction hoses, under which you will found the original Bosch. Remember to tighten everything well when finishing the job so as to avoid air leaks.

Juan
 

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The "cylindrical thing" behind the battery is the oil vapor separator. You have input from the camshaft cover (and from the crankcase?) and ouputs (liquid) to the sump (?) and to the airbox (air/oilvapor).

The hose to the metal tube is part of the boost drive valve system. Theese engines (and Lancias, Fiats and Saabs and ..) recirculate the pressurised waste air at throttle lift offs, i.e. it is not a dump valve that blows the pressurised air out of the system.

I hope I made it clear ...

/A
 
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A_Möller:
The "cylindrical thing" behind the battery is the oil vapor separator. You have input from the camshaft cover (and from the crankcase?) and ouputs (liquid) to the sump (?) and to the airbox (air/oilvapor).
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OK, That is pretty much clear. Pretty much what I had in mind, but I didn't think it would (could) pass the liquid oil directly to the sump. It makes sense now. I have seen the light. :D

I will probably have to make an adapter for the airbox to fit the vapor output. I guess one can't block it for good.?

The hose to the metal tube is part of the boost drive valve system. Theese engines (and Lancias, Fiats and Saabs and ..) recirculate the pressurised waste air at throttle lift offs, i.e. it is not a dump valve that blows the pressurised air out of the system.

I hope I made it clear ...

/A
So there is a sort of "dump valve" in the car already ?!? I saw this kind of general fitment for sale also and it was even more expensive than the normal (race) dump valve. (with the sound) wink

So what are the advantages for fitting a regular dump valve to this kind of system? (Apart from the sound)

Can one rip off the existing system ? And to what extent? How many meters of hose can I take off .. ( -kg :D )
 

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Okey, we're talking sound. Take a look at the pictures under my post "Airbox modification" and imagine the box with a foam filter (Jamex), i.e. almost a standard configuration. With standard chip you hear the boost dump CLEARLY, even without the airbox modifiaction. With increased boost it sounds like a rallycross car, it's almost too loud.

AT very high boost pressures you need a dump valve, but usually a boost drive system is preferrable as it helps the compressor spinning by the higher pressure (less compressor work needed) in the inlet ducting. My theory. But I don't know what capacity the standard boost drive valve has. Perhaps you gain performance and reliabilty by upgrding even at moderate boosts even though I don't think so.

If you want to clean up ein the engine bay I would first of all consider another intercooler arrangment, like a Pace chargecooler where the steel pipe runs today. Rearrange the 1.5 cm waterhoses and replace the battery by a smaller highperformance battery and the chargecooler will fit. Then turn the compressor 180 degrees and you will duct the compressed air upwards from the turbo and rearwards along above the gearbox to the throttle. That would be 100% supernice and effective. I consider that arrangement but do unforynately have to upgrade the brakes first.

/A
 
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Discussion Starter #7
I looked at the pictures and it looks very good indeed. Much better than using a standard cone without any airbox. Have anyone seen the BMC's CDA - stuff. It seems like a perfect kit. Carbonfibre airbox to put (somewhere) in the engine bay and a aluminium tube to get fresh cold air into it. BMC Homepage

Do you mean that there is noticable sound from the _original_ boost drive system? And do I understand correctly that this race kinda stuff is better at much higher boosts? What if I put in both. The dump valve being adjustable so it kicks in higher than 1 bar and the original doing it's business as before.

I myself cannot go and try my car since it is not yet registered in Finland. :( I am just waiting for tax reduction.

As for the engine bay rearrangement. I intend to reroute the battery to trunk. Several reasons for this.
1. I can put on a bigger battery ( Cold winters and lots of audio equip),
2. Audio equip will be in the trunk anyway
3. More space in the engine compartment
4. Better weight distribution? Does anyone have specific weight distribution of Q4 (wheel by wheel)

That chargecooler thing looks very neat indeed. Does anyone know how much pressure can the original intercooler handle (physically)?

Rotating the charger might ba cool trick, too. :cool: I have to look at it the next time I have time to take a closer look. Thanx.
 

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Hi sami,

The BMC CDA kit looks nice, but from what I could see the largest kit was dimensioned for 2.5 litre displacement, i.e. < 200 hp. So it wouldn't have enough capacity for any tuning plans.

Most notable difference in sound did I get when I replaced the paper filter with a foam filter. I don't think it would be worth the job to build a hybrid boost drive and dump valve system. Especially not if you consider it as to crowded as it already is.

The standard intercooler holds at least for as much us the Magneti Marelli P8 system allows, i.e. 1.5 bar.

/A
 
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Discussion Starter #9
1. When/if you replace the airbox with cone filter make a large t-piece to accept the air oil seperator hose and fit the cone filter where the airbox used to live.

2.The intercooler has plastic end caps and will only really take 1.5bar

3. The dump valve is not a dump valve but a recirc valve, excess pressure gets recycled into the induction route.

4. Not fitting a dump valve would cause the turbo to stall on lift off and my even shatter the turbine blades.

5. If you fit a cone filter the re-circ valve will be alot louder and will draw attension to the car.

6. The Q4 has an overboost (pierburg) valve (top right of the radiator as you look at the front of the car) to control overboost situations in conjunction with the ecu. Fitting a bleed valve may well give you more boost, but you have now disabled all the safety feature built into the ECU. Do you really want to do that??
 
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