G60 boosts too much

[Staffan 10]

My Corrado G60 from 1989 has a boost problem. It runs just fine up to 3500 rpm and 0,5 bar but then boosts 1,5 bar and the engine looses significant power. It is chip tuned and is supposed to deliver about 1,0 bar.

Is there anybody in the forum who can help me. Why is it "overloading"?

[Simeon 0]

What chip have you got in it? Do you have the ISV removed? What have you done about the boost return?

[Staffan 10]

It is a SLS P3RS and a 68 mm pulley. The ISV and boost return are stock. There was a ISV check valve but I removed it yesterday and put a hose instead but there was no difference.

 

The car ran great all summer (I bought it in April) and I have not changed anything (except for the check valve yesterday)

 

I took it out for a spin today, just to try to be more accurate in my description of the problem. I noticed that at half throttle and up to 0,5 bar the car runs just great. When I hit the throttle the engine looses power and the boost gauge shows up to 1,5 bar.

 

My son says that he can hear a hiss-sound when the gauge shows over 0,5 bar. Would the gauge show that much boost if it is a leak???

[Staffan 10]

It is a SLS P3RS chip and the ISV and boost return are both stock. The pulley is 68 mm.

The car ran great all summer (I bought it in April)

[Simeon 0]

Ok, cool, so what other symptoms have you got? If I'm honest I don't really understand how you're seeing 'overboost' and losing all power .. what is happening if you apply even throttle in, say, 3rd gear up to and through the 3.5k rpm point you say is causing trouble.

 

Does it make a difference how hot or cold the engine is? (not suggesting you go ahead and abuse your engine when cold by the way)

[Staffan 10]

I took the car for a drive today just to try to be more specific in my description of the problem. If i apply even throttle in 3rd the engine looses significant power as soon as the boost goes above 0,6-0,9 bar it doesn´t matter what the rpm is . It seems like the problem gets worse when the engine gets hotter. The spark plugs are very black.

I am also questioning the fact that the gauge shows "overboots". Might be something wrong with it??!!!

[Staffan 10]

It is not easy to describe the problem in a foreign language, I sure hope you understand my English.

 

It seem like the the engine looses power as soon as the g-lader starts loading. The loss gets more significant over 0,5 bar, no matter what the rpm is. Over 1 bar( it is not supposed to load over 1,0 bar) it´s really bad, no power at all. If I drive and third gear and hit the throttle hard, the boost gauge goes up real quick. As soon as I ease of the throttle it runs smoother

 

The idling is perfect and it starts real easy. It runs really smooth when it´s not charging.

It seems like the powerloss increases when it is hot.

 

The spark plugs get really black and they smell of fuel.

Edited October 31, 2017 by Staffan

[VEEDUBBED 0]

Start with the easy things first.

Change the coolant temp.Sensor that sends the signal to the ecu for temp. or Swap over the blue and Black Sensor plugs to see if the engine runs better, the black and blue sensors on the front coolant hoes flange both have the same resistence.

Check the Ohm reading on the CO pot located on the boost tube, should be around 450/500 Ohm, they are sometimes miles out.

Check the full throttle switch works.

How are you monitoring actual boost?

Edited November 1, 2017 by VEEDUBBED

[Staffan 10]

Thanks for reply. Will check the sensors and and CO pot asap. Have checked throttle switch, it was OK. I´m monitoring the boost from a pretty cheap on dash gauge. I have some suspicion that the gauge is not 100%. It was mounted in the car when I bought it

[VEEDUBBED 0]

Obviously, try using a decent, accurate boost gauge, prefrebly taking a direct reading off the inlet manifold or MFA signal pipe.

[Staffan 10]

Start with the easy things first.

Change the coolant temp.Sensor that sends the signal to the ecu for temp. or Swap over the blue and Black Sensor plugs to see if the engine runs better, the black and blue sensors on the front coolant hoes flange both have the same resistence.

Check the Ohm reading on the CO pot located on the boost tube, should be around 450/500 Ohm, they are sometimes miles out.

Check the full throttle switch works.

How are you monitoring actual boost?

 

Checked CO pot today it was 790 OHM. Swapped black and blue coolant sensor plugs and no difference. Still looking for a good boost gauge. I have started to put in new vacuum lines.

[Graphite 0]

Your boost guage reads the pressure that is accumulating in the manifold in the period between the inlet valves being open and closed on each cylinder.

 

Given the Supercharger drive ratio is the same both above and below 3500 rpm, your description suggests that above 3500 rpm there is a lot more pressure being generated (over three times more).

 

Logic states that if this were happening, your engine above 3500 rpm is unable to breathe quick enough to consume the incoming boost.

 

As engine RPM increases the valves open and close faster in proportion to engine speed, meaning that it consumes the incoming air at a propotionaly faster rate, however you have to bear in mind that as RPM increases the time that the inlet valves are open for reduces, meaning that the air needs to be forced in quicker, But your supercharger should also be spinning proportionally faster and generating higher boost pressure to account for this.

 

So you will eventually get to a point in the RPM range where A) The supercharger is producing peak boost (the most your unit can actually deliver, this will vary depending on the health of your charger) and B) Your engine can't consume the pressurised air quick enough to stop the boost pressure in the manifold from rising. So there will be a point where the boost will seem to increase faster, usually at higher RPM or full throttle application, especially if your supercharger produces peak boost at an RPM that is higher than the engines ability to consume the air fast enough and starts to plateau.

 

Your boost gauge is reading the pressure from the manifold, between the throttle body and the cylinderhead? If not you need to correct that. I see you're located in sweden, there are many petrol mad volvo owners who have heavily modified their cars in your country (toyoya supra engine conversions etc), see if you can track one of those guys down to find out where you can purchase a good boost gauge in your country. I am tempted to say that your boost gauge is reading incorrectly.

 

So, you seem to loose power and your plugs are fouling also.

 

The plugs fouling and being black is a telltale that the engine is running rich, especially if you have a strong smell of fuel. This is either an issue of over fuelling, or you are loosing spark past 3500 rpm leading to incomplete combustion.

 

There are only a number of things that control fuel on a G60.

 

The chip and ECU

The blue ECU engine coolant temperature sender

The CO Potentiometer

The injectors themselves

The fuel pump

The wiring between these components.

 

There are only a number of things that control spark:

 

The chip and ECU

The hall sender on the distributer

The ignition coil

The ignition HT leads

The spark Plugs

The wiring between these components

 

The only other thing that can affect this is the engine timing by the cambelt. But I would expect you to have running issues prior to 3500 rpm that were obvious if you had an issue there.

 

My advice is to start with the basics. Check your cambelt timing (especially if the belt has not been changed in the cars recent history) purely just to eliminate this issue as then you know youre working from a safe basis.

I would be tempted to put a stock chip back in the ECU to see if that changed the behaviour of the car.

 

If that doesn't change it you will have to go through the Fuel and spark systems to try and track the problem down.

 

You state you have started to put new vac lines in, however if your engine is idling normally (around 850-900 rpm) then I am doubtful you have a vacuum leak.

 

Hope this helps and keep us updated.

[Staffan 10]

Your boost guage reads the pressure that is accumulating in the manifold in the period between the inlet valves being open and closed on each cylinder.

 

Given the Supercharger drive ratio is the same both above and below 3500 rpm, your description suggests that above 3500 rpm there is a lot more pressure being generated (over three times more).

 

Logic states that if this were happening, your engine above 3500 rpm is unable to breathe quick enough to consume the incoming boost.

 

As engine RPM increases the valves open and close faster in proportion to engine speed, meaning that it consumes the incoming air at a propotionaly faster rate, however you have to bear in mind that as RPM increases the time that the inlet valves are open for reduces, meaning that the air needs to be forced in quicker, But your supercharger should also be spinning proportionally faster and generating higher boost pressure to account for this.

 

So you will eventually get to a point in the RPM range where A) The supercharger is producing peak boost (the most your unit can actually deliver, this will vary depending on the health of your charger) and B) Your engine can't consume the pressurised air quick enough to stop the boost pressure in the manifold from rising. So there will be a point where the boost will seem to increase faster, usually at higher RPM or full throttle application, especially if your supercharger produces peak boost at an RPM that is higher than the engines ability to consume the air fast enough and starts to plateau.

 

Your boost gauge is reading the pressure from the manifold, between the throttle body and the cylinderhead? If not you need to correct that. I see you're located in sweden, there are many petrol mad volvo owners who have heavily modified their cars in your country (toyoya supra engine conversions etc), see if you can track one of those guys down to find out where you can purchase a good boost gauge in your country. I am tempted to say that your boost gauge is reading incorrectly.

 

So, you seem to loose power and your plugs are fouling also.

 

The plugs fouling and being black is a telltale that the engine is running rich, especially if you have a strong smell of fuel. This is either an issue of over fuelling, or you are loosing spark past 3500 rpm leading to incomplete combustion.

 

There are only a number of things that control fuel on a G60.

 

The chip and ECU

The blue ECU engine coolant temperature sender

The CO Potentiometer

The injectors themselves

The fuel pump

The wiring between these components.

 

There are only a number of things that control spark:

 

The chip and ECU

The hall sender on the distributer

The ignition coil

The ignition HT leads

The spark Plugs

The wiring between these components

 

The only other thing that can affect this is the engine timing by the cambelt. But I would expect you to have running issues prior to 3500 rpm that were obvious if you had an issue there.

 

My advice is to start with the basics. Check your cambelt timing (especially if the belt has not been changed in the cars recent history) purely just to eliminate this issue as then you know youre working from a safe basis.

I would be tempted to put a stock chip back in the ECU to see if that changed the behaviour of the car.

 

If that doesn't change it you will have to go through the Fuel and spark systems to try and track the problem down.

 

You state you have started to put new vac lines in, however if your engine is idling normally (around 850-900 rpm) then I am doubtful you have a vacuum leak.

 

Hope this helps and keep us updated.

 

Thank you so much for your very interesting reply. My gauge is connected between the throttle body and the cylinder head on the FPR line.I will hunt down some Volvo freaks to see if they know what kind of gauge I should get.

 

You are absolutely spot on that the idle would be suffering if there was a vacuum leak.

 

I have done some measuring:

Co pot 790 Ohms

Blue coolant sensor 3530 Ohms

ISV 4,1 Ohms

O2 sensor 0,190-0,570 Volts, 0,570 with cold engine and falling to 0, 190 as the engine gets warmer.

 

I have replaced the fuel pressure regulator, no difference at all.

 

Next thing is checking the timing belt.

I´m so grateful for all the help I can get and I´ll be more than happy to update.

[Graphite 0]

You’re more than welcome, we’ve all been there at some point.

 

I have found measurements for the CO pot in particular to be a bit of a here and there thing. I’ve seen cars running perfectly well (using a multiple gas analyser to check CO, HC and Co2) running CO pot values outside of the listed range.

[Staffan 10]

You’re more than welcome, we’ve all been there at some point.

 

I have found measurements for the CO pot in particular to be a bit of a here and there thing. I’ve seen cars running perfectly well (using a multiple gas analyser to check CO, HC and Co2) running CO pot values outside of the listed range.

 

I had these values checked at the annual inspection three weeks ago: CO at idle: 0,09%, above 2000rpm: 0,20%, HC: 21 PPM,

Co2: 1,03

 

The car passed the inspection with these values so I guess they are good.

[Graphite 0]

Those are reasonable figures. But I guess this is before you started to experience what you have described?

[Staffan 10]

Those are reasonable figures. But I guess this is before you started to experience what you have described?

 

Yep those figures were before my problems started and now I have got some serious problems. My G-lader broke down totally today. I´m talking major breakdown.

So now I´m on G-lader hunt and hopefully my earlier problems get solved with a fresh lader. Any idea where to find one at a descent price. I´ve looked at eBay but the prices are unbelievable.

Thank you guys for your time trying to help me out

[VEEDUBBED 0]

Bung a turbo on there instead, for the price sellers charge for that crap charger one could nearly buy an entire car..

[Staffan 10]

Bung a turbo on there instead, for the price sellers charge for that crap charger one could nearly buy an entire car..

 

I know, g- lader prices are ridiculous. I would like to have a turbo instead but isn´t it difficult to make it work with all that stonage electronic and sh*t on the Corrado?

[VEEDUBBED 0]

I've done At least 3, 1st one was using an old kkk24 turbo off an old Audi Quattro.

Digifant was fine, just use a chip written for a turbo application, add a wide band air/fuel meter, 8v turbo manifold off eBay, Volvo orange 300cc injectors or Saab red top versions, rising rate fuel press. regulator, better intercooler than the Shiyte g60 one..

Plumb in the turbocharger with water and oil, add an oil return to the sump or use an old golf gtd sump as it already has one.

There's more but that's the basic layout.

[Staffan 10]

Thanks for the interesting info.I will absolutely look into this.

[Dox 22]

Yep those figures were before my problems started and now I have got some serious problems. My G-lader broke down totally today. I´m talking major breakdown.

So now I´m on G-lader hunt and hopefully my earlier problems get solved with a fresh lader. Any idea where to find one at a descent price. I´ve looked at eBay but the prices are unbelievable.

Thank you guys for your time trying to help me out

 

Could it be you have a blocked exhaust / collapsed cat that's put the charger under so much pressure its gone bang?

[VEEDUBBED 0]

If the cat or silencers were indeed buggered, I reckon the engine wouldn't rev that high to cause an overboost, you'd probably get the exhaust manifold glowing red hot too.

Get a decent boost gauge and don't tap into the fpr's feed hose, it needs its own independent line, preferably the original g60 boost signal pipe that is connected to the blue boost sensor located on the back of the instrument panel, as the factory originally provided.

You could also use the inbuilt MFA's boost function too.

[Graphite 0]

Could it be you have a blocked exhaust / collapsed cat that's put the charger under so much pressure its gone bang?

 

That is worth checking out.

[Staffan 10]

That is worth checking out.

 

I shall absolutely check that. Right now I don´t even want to see the car.

Edited November 10, 2017 by Staffan