Boost pressure.... what boost pressure

[catch_twotwo 0]

Ok, so I've just picked up my 1990 G60 (only £850) but when I was doing the boost test I could only clock 1095 (exactly 1095 mind you... and it hit that at about 3000 rpm). Now according to the buyers guide this would mean the charger is off (or shot)

 

However if that was the case I'd be expecting the car to run like a 2 legged dog... needless to say it doesn't and I had to make sure to remember to slow down as I hit 100 on the M25 on the way home, and it got there quick as well.

 

So am I doing the test wrong (read and reread the doco at least 4 times) or is there something else I'm missing here ?

 

I guess the nice folks at g-werks will tell me on Saturday anyway... but I'm a curious fellow :lol:

[Blue_Joe 0]

I would let Darren at G-werks have a look and work his magic!

[catch_twotwo 0]

Yes... I guess that's the best bet...

 

However with my knowledge of cars I'm likely to turn up (3 hour drive) and have him laugh his ass off as there is no charger installed :lol: possible an embarassment I couldn't live down.......

[Walesy 0]

LOL..that would raise a smile if you turned up in a 16v wanting a charger rebuild!.

 

 

Are you sure the figures are correct mate?..it's just that i seem to remember the boost test has to be taken at redline in 3rd and 4th gear?...not 3k revs?..

[catch_twotwo 0]

Yeah I got it as close to redline as i could on the road... but after about 2500 the boost pressure sat at 1095 and never moved an inch all the way.

 

Still, it needs an engine service so it's worth the trip anyway ;)

[Walesy 0]

yeah deffo, get it to G-werks anyway. :thumb right:

[catch_twotwo 0]

Yeah although for the lader rebuild, engine service and chip/pulley it's going to cost me more than the car did ?

 

I'm not sure, but it just feels so wrong :roll:

[Spykee 0]

does anyone have a link to the thread with what the boost readings should be?

 

im having a few issues and have been looking at the service screen for boost readings but im not sure what they are supposed to be and what rpm's the test is done at?

 

i take it is at 6k in 3rd and 4th from what it says here?

 

the other thing is mine seems to read in psi or pascals cos its a proper german one...... :?

[stevemac 0]

The guide below is just that - a guide. MFA does not accuractely measure boost levels.

 

 

 

How to test your boost levels - UK spec cars

 

1. Start Engine

 

2. Move the MFA selector to "2"

 

3. Press and hold the MFA end button (keep holding)

 

4. Stop engine

 

5. Start engine

 

6. Release the MFA end button.

 

7. Press the MFA End button one time.

 

 

You should now see 450-800 readings fluctuating with idle. Anything higher than 800 is not right (vacuum leak). Much less than 450 is probably too much timing advance.

 

Go run your car!!! 3rd and 4th gear to REDLINE. Carefully note the highest #'s you've got.

 

A pullied charger should not make less than 11.6psi, and even so, thats weak. A Stock charger should make ~~11psi in perfect shape!

 

EURO Hg(#'s of boost/vacuum) Comments

200 -23.7

400 -17.8

600 -11.9

800 -5.9

1000 0 (Atmosphere- ala no boost, charger is bypassed)

1200 2.9 psi (Your charger is dead or big boost leak)

1400 5.8 psi (Your charger is about dead or big boost leak)

1600 8.7 psi (Your charger needs new apex strips or big boost leak)

1800 11.6 psi (Great for stock pulley, Probably needs new apex strips if 68mm pulley)

2000 14.5 psi (Great for 68mm pulley on stock charger)

2200 17.4 psi (Great for 68mm pulley on heavily ported charger, hold on to your ass fast!!) :rambo:

 

2000 and up folks need to be careful with fueling, as the programming maps end at about 2000 on the ecu :) Dynotuning, and air/fuel/egt gauge, and custom chip recommended.

 

Info supplied courtesy of http://www.snstuning.com

[stevemac 0]

For early (upto mid 1992) C's the extra MFA functions are:

 

MFA switch, position 1:

1: Engine map code.

2: Country code.

3: Speedo drive ratio.

4: Upper RPM limiter.

5: Lower RPM limiter.

6: Deceleration fuel shutof pressure.

7: Segment test.

 

MFA switch, position2:

1: Test sum of programmed bytes

2: Intake manifold vacuum/pressure. (Boost level)

3: Engine RPM.

4: Momentary fuel consumption.

5: Signal from speed sensor.

6: Oil temp.

7: Ambient temp.

 

Info supplied courtesy of http://www.snstuning.com

[catch_twotwo 0]

Well, the latest on this is that after a full rebuild my boost pressure is still only showing 1024....

 

Is there a component that sends the boost pressure to the MFA ?

[Tempest 0]

Is the display permanent, i.e. does it display this value even when idling or when the engine is turned off (still need to take the MFA in its diagnostic mode, of course)?

 

If so, you may have a leak somewhere in the vacuum hoses or more likely the vacuum sensor is shot.

 

Tempest

[catch_twotwo 0]

It idles fine, and goes upto 1024 as you'd expect... but then hits 1024 and stays there going not one point higher no matter what. I'd expect it to shift a little depending on the speed even if the hoses where shot, or am I wrong on that ?

[stevemac 0]

1024 is atmospheric pressure - I suspect your vacuum pipe has become disconnected or has a large leak.

[catch_twotwo 0]

Odd, as Darren at G-werks put on a new pipe for me.

 

Guess I'll have to have a closer look when the car gets back from the bodyworkers, and I have a spare hand to help me get the damned bonet open....

[Supercharged 2]

Darren proably did the one to the ECU - there is a more solid pipe that goes to the clocks, it's probably come off behind the clocks...

[catch_twotwo 0]

No Darren replaced the main boost pipe as it had a huge foot long tear and was getting zero boost.

 

Sorry to sound silly (well I am, but still) is the tube you're talking about only for the MFA ? As what throws me off is that even though it's saying no boost, it still goes some.....

 

So do I need to take the clocks out to reseat that tube ? or get to it from the engine bay ? Man I really need to get a detailed manual....

[stevemac 0]

We're talking about the small pipe that goes to the MFA.

 

Likely to have come off the back of the clocks or fallen off the connector on the brake servo vac pipe in the engine bay. The MFA measures pressure in the inlet manifold via this small pipe.

[g60greeny 0]

now i'm really not happy :mad:

been sayin to everyone lately how fast my G feels how well she picks up speed,nice an smooth idle etc. so i decided to do the boost test well what a load of big fuckin bollocks bastid fuckin waste of time(sorry for the swearin but i'm proper pissed off)

anyway got a readin of 1095 the highest it would go even though i'd gone into warp speed!!!!!thought i was marty mcfly for a sec!! quite a scary moment redlining 3rd an 4th while watchin traffic an things anyway any ideas?checked the hose on the back of the clocks thats ok as far as i know?unplugged it an started the engine and i could feel the hose sucking?so i pressume its also connected at the other end?surely its not the charger!!!!if it is it could be the end of my G!!!till i can raise some funds to sort it out god knows when that will be?someone tell me its not all that bad please!!just an hose thats not connected,dodgy readings anything but the charger,only positive in it being the charger i can come up with is that it feels fast as fuck now so if it is the charger and daz has to sort it it out then surley i'm gonna have the biggest fuckin grin on my face i've ever had :lol:

 

 

sorry for gettin a bit down there just listening to my james blunt album

[veeDuB_Rado 0]

just listening to my james blunt album

 

I think I've found your problem...

[catch_twotwo 0]

Damned, that was my job for the weekend... guess maybe my problem is somewhere else.

 

No James Blunt for me either. so guess the problem lies elsewhere 16v.

[bix 0]

now i'm really not happy :mad:

been sayin to everyone lately how fast my G feels how well she picks up speed,nice an smooth idle etc. so i decided to do the boost test well what a load of big **** bollocks bastid **** waste of time(sorry for the swearin but i'm proper pissed off)

anyway got a readin of 1095 the highest it would go even though i'd gone into warp speed!!!!!thought i was marty mcfly for a sec!! quite a scary moment redlining 3rd an 4th while watchin traffic an things anyway any ideas?checked the hose on the back of the clocks thats ok as far as i know?unplugged it an started the engine and i could feel the hose sucking?so i pressume its also connected at the other end?surely its not the charger!!!!if it is it could be the end of my G!!!till i can raise some funds to sort it out god knows when that will be?someone tell me its not all that bad please!!just an hose thats not connected,dodgy readings anything but the charger,only positive in it being the charger i can come up with is that it feels fast as **** now so if it is the charger and daz has to sort it it out then surley i'm gonna have the biggest **** grin on my face i've ever had :lol:

 

 

sorry for gettin a bit down there just listening to my james blunt album

 

It would be slow as fcuk with that little boost, the reading is wrong. If you can feel the tube on the back of the clocks sucking then maybe it is the pressure sensor on the back of the clocks faulty, or the clocks themselves!

[catch_twotwo 0]

Yeah mines the same..... still goes like stink though.

 

Seems odd though as on mine all the other readings work fine. I'd have thought they'd all fail and not just the one for boost ?

 

Does anybody have these two tubes marked on a diagram so I can double check mine this weekend ?

[g60greeny 0]

catch_twotwo, what does yours read at idle?

[B DUB 0]

Can any 1 help i dont understand all this . ive done the mfa test and on idle mine between 650-700. now is this good or bad? or is there more to do in the test? :scratch: