hard to get boost, but once its there, oh boy?

[Gothmolly 10]

Hello all,

 

I've acquired a 1990 G60 running a ported G-Lader and a 'Stage 5' SNS "no lag" chip. I am not getting a lot of boost, unless I really stand on the go-pedal and run the engine upwards of 4k RPM. Is this normal? I rarely see boost measured on the boost gauge at all, in normal stop-and-go, or even highway traffic. It seems like to get the boost and charger to really kick in, I have to floor it. Is this normal behavior?

 

I'm used to a TDI motor where as soon as you kick it in the guts, it just flies.

 

Thanks

[owen g60 10]

i have been in a couple of G60's recently and they all seem to behave in a similar way.

 

In my one when driving around normally my boost gauge measures a either a slight amount of vacuum or a slight amount of boost.

 

when i stamp on the loud pedal i get somewhere in the region of 1.5 - 1.8 bar of boost.

 

I think you will find this is a similar story for most as at low throttle most of the boost is recirculated out of the throttle body back into the charger (or to atmosphere if you have deleted this function).

At large amounts of throttle the butterfly on the back of the throttle body is closed so boost is no longer recirculated hence the higher boost readings

[steveo29 0]

take a look in the throttle body , the boost return butterfly stays partialy open until almost full throttle

[Gothmolly 10]

This seems like lousy driveability - any way to tweak this a little? With an increase in boost the ECU will add appropriate fuel to keep the mix correct, right? Is this valve ECU controlled, or springloaded like an old turbo wastegate?

[steveo29 0]

its mechanicly controled with a linkage from the throttle , some people do ajust them for earlier boost but the tuners dont reccomend it

 

might be an another issue , they should drive ok when working , but you dont get the sudden boost surge like a turbo

[mimjed 0]

Sounds quite possible you have a boost leak. Do you still have the plastic silencer box next to the charger?

 

Have a look at the condition of the vac hose from the back of tb to the ecu too.

[Rustynuts 0]

Boost does not just come blasting through like a turbo. The charger is belt driven by the engine so boost builds up with engine speed. So you get a linear boost delivery that rises with the revs and does mot have the on off element a turbo does. For drivability think more naturally aspired than turbo. You would say the same of a VR by the way, you have to really boot them for them to fly

[Alex_G60_Fanatic 0]

Sounds quite possible you have a boost leak. Do you still have the plastic silencer box next to the charger?

 

Have a look at the condition of the vac hose from the back of tb to the ecu too.

I agree with this... you shouldn't have to spool up to 4000 rpm to get a good pull. You either have a boost leak or the charger isn't to healthy

 

Boost does not just come blasting through like a turbo. The charger is belt driven by the engine so boost builds up with engine speed. So you get a linear boost delivery that rises with the revs and does mot have the on off element a turbo does. For drivability think more naturally aspired than turbo. You would say the same of a VR by the way, you have to really boot them for them to fly

Not quite... Super chargers will show a lineage power increase but they are most effective at low revs compared to turbo's. His charger should be noticeably pulling from 2000 rpm all the way up to 5-6k... he shouldn't need to gun it to see a power increase... you don't suffer turbo lag and the super charger doesn't need to spool up because it's already turning!

Gothmolly things you need to check are

 

 

1. vacuum pipe from intake manifold. This needs to be exactly 100mm long (please correct if I'm wrong here guys) with a good seal
   
2. take the charger pipe off the exhaust side of the charger (the one that goes down to the inter-cooler) and check for oil... there will always be a small amount of dirt in the pipe but if there is allot of liquid oil then the charger needs servicing!
   
3. check for boost leaks along the air intake system. Spray some soapy water around the charger hoses and throttle body gasket.
   
4. Check your intake manifold for blowing or cracks
   

start there but also take a look at your spark plugs and HT leads... it could also be ignition related.

 

Chargers that are ported to stage 5 are always right on the edge of falling to bits... the casing and internal gubbins are all knife edged to the point where they are very fragile. this means that they need servicing more often and are effected more by dirty oil etc.

 

When was the car last serviced? and when was the charger last serviced?

 

---------- Post added at 10:01 AM ---------- Previous post was at 09:47 AM ----------

 

just as an aside... this happened to my g60... put your foot down and nothing until 4000rpm when I would notice a marked increase in pull... almost like turbo lag but more instantaneous.

 

That turned out to be the charger leaking oil into the air intake. The oil cakes up the plugs and en-riches the fuel mixture throwing off your ECU. Only at high revs with WOT did the air coming in mix well enough to give a good spark and get the car pulling again.

[owen g60 10]

only one correction from what i have read... the pipe from the intake to the ecu needs to be 1m long (100cm)

[Alex_G60_Fanatic 0]

only one correction from what i have read... the pipe from the intake to the ecu needs to be 1m long (100cm)

 

it didn't sound right when i wrote it down! :lol:

[KipVR 1]

I think the vac pipe needs to be 1000mm long?

 

---------- Post added at 10:56 AM ---------- Previous post was at 10:55 AM ----------

 

must refresh more often :-)

[owen g60 10]

we all have those 'special' moments now and again :D

[Gothmolly 10]

Good stuff, thanks guys. The charger got overhauled by BBM about 13k miles ago. The previous owner had the car sitting though, so I'll check on the hoses for cracks and leaks. The air cleaner was completely filthy, yet changing it had no effect. The silencer has been removed. Mimjed, you wrote "Have a look at the condition of the vac hose from the back of tb to the ecu too." - when you write "tb" you mean timing belt correct? I'm going to run a compression test to get a baseline (200k on motor) so its a perfect time to check the plugs.

 

My TDI has a VNT so its able to deliver pretty quick response, but I assumed the supercharger would give a proportional response, unless there's something up with the ISV. I'll have to find a sunny day and tear into it.

Edited September 23, 2011 by Gothmolly

[josh.c 10]

Gothmolly, tb stands for Throttle Body I believe. :) I think a lot of people here have their chargers serviced every *Alex_G60's post below*, and if that is correct then maybe it's a bit tired and needs a good service? I could be completely wrong mind you, so wait for some confirmation / correction first!

Edited September 23, 2011 by josh.c
Corrected

[Alex_G60_Fanatic 0]

Gothmolly, tb stands for Throttle Body I believe. :) I think a lot of people here have their chargers serviced every 15,000 miles, and if that is correct then maybe it's a bit tired and needs a good service? I could be completely wrong mind you, so wait for some confirmation / correction first!

 

every 40k miles for a standard charger

30-35k miles for a ported charger/smaller pulley (68mm)

25K for stage 5 ported and 65mm pulley

 

As a rough guide...

 

Give your ISV a good clean with some carb cleaner two... It could be a little gunked up.

[mimjed 0]

Indeed tb, throttle body. Think its 3.2mm diameter hose, ive got some in my garage if you need some, vw was something daft like £125 a metre!

 

Shouldnt get lag as such from a supercharger, thats where they had an advantage ovet turbos before computers took over everything.

 

Sit in second gear at 3k for 15 seconds and then floor it, if it doesnt come on boost straight away then there is a problem to be found.

[Gothmolly 10]

Thanks guys - another question, after I swapped the essentially clogged air filter with a new one, I get a constant high pitched whistle while I drive - am I finally hearing the charger? Also, since I'm not 100% sure on the "mods" that this has, I see a large opening in the airbox (under the filter) which sort of mates with an opening in the bit behind the grill - is there supposed to be some kind of duct there, or is it just a "hole" ?

[mimjed 0]

The whistle is indeed associated with the charger ;)

 

The hole means somebody has desnorkled your airbox. First thing i do when i get a g60. Allows more airflow and makes a bit of a roar. Some people obviously dont like it.

 

If you get rid of the co pot then most people put a cold air feed to where it used to sit too.

[Rustynuts 0]

Mimjed, you don't mean co pot, you mean carbon canister.

[Gothmolly 10]

The charcoal thing is long gone. Let's hope I still pass inspection - the car passed in the previous state where it was registered, but who can tell. I may need to use the old "Here's $50 buddy, this care passed inspection, RIGHT?" trick.

[owen g60 10]

you will be surprised.... unless its rusted badly they are good on emission tests etc... even with decats they seem to meet the required standards (in the uk atleast)

[mimjed 0]

Was always led to believe they were the same thing?? Never mind a.

 

Didnt realise you were a yank! Emissions tests are much more difficult over there. Pre 92 here you can get away with pretty much anything, mine was decatted, nearly straight through exhaust and no lambda so running rich. Not a word said :)

 

Co pot as imformed ;) doesnt really do anything after 100k anyway so not one to worry about overly.

 

Everyone loves a blind test! £80 in leics and it doesnt even go on the ramps

[Redfox 10]

Hi Gothmolly, That 50 dollar trick would bring you right in front of a judge where I come from... ;)

 

What does your mfa read? Or bar meter if installed?

 

Cheers,

Redfox.

[Gothmolly 10]

If $50 gets you in front of a judge, then you know the wrong mechanics. When the boost comes up, I get around 12-13 psi.... so I guess almost 1 bar? (1 bar = 14.7 psi right?)

[owen g60 10]

Thats not too bad... for a ported charger and i am asuming 68mm pulley then you are doing well.

 

Seems you may have a bit of a restriction in your system then if you thinkpower takes a while to kick in.

 

Do you have an after-market RSR outlet?? I have never felt what a G60 is like to drive without one so cant compare, but my power seems pretty instant