Start of Wastegate Trouble...?

[VanhireBoys]

Gents
I was out n the car yesterday and went to overtake.. I put the shoe down and no boost.. Guage was only showing approx 1.2bar. I put the shoe down again and no boost. I put the clutch in and stopped the engine. Restarted on the key and put the shoe down again.. Boost this time no problem.. Car was ok today as well !

I am thinking that the wastegate isnt closing properly perhaps...? I replaced the wastegate in 2005 with a second hand unit as the original had been messed about with. Some person of questioable parentage put shims in it causing the car to overboost []

Does anyone refurbish them or is there a rebuild kit available..? Any advice ..? I am trying to keep the car standard so I really dont want to go modified.... Or am I just panicing for no reason []

 

[944Turbo]

Would you be running a boost enhancer? Classic at this time of year is an overboost trigger as the colder denser air generates more boost triggering the overboost protection in standard chips. Ignition off and on will reset it and boost is restored, undo the boost enhancer a turn and that should get you through the winter.

shims should help the wastegate close and are there to compensate for a week spring,
Tony

 

[poprock]

Can I ask a quick tangenital question?

What exactly are the symptoms of overboost? I have a (very) occasional issue and suspect that's what is happening "¦

When I'm pushing the car a little harder than usual, revving and boosting higher than everyday driving, I sometimes have a sudden almighty loss of power"”exactly as though the turbo just cut out completely. Happening at speed, it feels a lot like slamming on the anchors. The car recovers quickly as long as I stay off boost and is back to normal running in less than a minute. (I don't need to ignition off and on, it just recovers with time.)

Do I call that overboost? It's the turbo/wastegate allowing more power through than the electronics are set up to permit?

 

[Lowtimer]

Poprock,

That is exactly what the overboost protection is like.
Assuming you have not been tinkering with it, the chances are you have a little air leak somewhere in the boost control system.

 

[poprock]

Thanks! Entirely possible, in that case. Or it could be the Lyndsey boost enhancer being incorrectly set "¦ or the adjustable wastegate being on too hard a spring "¦

Because it's only happened to me a couple of times in a few years I have never looked into the issue properly. Adding it to the list now!

I suppose what I'll need to decide eventually is whether to tone everything down so as to prevent overboost, or to re-chip and allow the power through.

 

[Lowtimer]

Ah, well, that (in the nicest possible way) was what I meant by tinkering with it! Yes, if you are running standard chips, best to think about turning down the wick a bit as it will be running lean when the boost is higher than standard. I would always have a thorough leak test once a year though, as that could well be a contributory factor.

 

[poprock]

Aye, the car was well tinkered with by the previous owner and five years later I'm still on the long learning process to really understand how the bits all interact.

 

[barks944]

Overboost protection is one thing, but there is also knock protection in the 944 as well. When the DME detects knock it puts a permanent 4 degree retard on the ignition which only resets when the DME is turned on and off. Poprock I would say for you the overboost protection is kicking in, although I don't know exactly what it is programmed to do. I just know it looks at the AFM signal and compares it to a maximum flow rate at a given RPM.

 

[VanhireBoys]

ORIGINAL: 944Turbo

Would you be running a boost enhancer? Classic at this time of year is an overboost trigger as the colder denser air generates more boost triggering the overboost protection in standard chips. Ignition off and on will reset it and boost is restored, undo the boost enhancer a turn and that should get you through the winter.

shims should help the wastegate close and are there to compensate for a week spring,
Tony

I forgot to say my car is totally standard.... with standard factory chipset and control setup - Nothing added - Nothing taken away !.. Deffo wasnt the overboost as the car was up to temp and I hadnt pushed it hard up to the overtaking point... I had a problem with a broken leg on the wastegate actuator valve in the past and this caused the overboost cut out .. This was different feel if you like ... !

I wish I could get on the boat and take the car over to demonsrate the problem Tony but knowing my luck she would be totally fine ...[]

I am going to just drive her on until it gets worse - then I will be able to say for sure []

 

[robwright]

ORIGINAL: poprock

Aye, the car was well tinkered with by the previous owner and five years later I'm still on the long learning process to really understand how the bits all interact.

If you have aftermarket chips and non-standard wastegate chances are you have no overboost protection. That is a risk you run on a modified car. That is exactly why I have an aftermarket stepper motor boost gauge to keep a check on the boost and an AFR meter to keep an eye on the mixture [] Over boost on the standard wastegate is controlled by the cycling valve, which uses manifold presure to open the wastegate removing exhaust gas pressure from the turbine of the turbo. I know certainly with the Tial this function does not exist not sure about the Lynsey's though. Does the Lynsey wastegate have three boost lines attached to it??? If so one of these could still be actuating the standard overboost function of the factory WG.

 

[944Turbo]

ORIGINAL: VanhireBoys

ORIGINAL: 944Turbo

Would you be running a boost enhancer? Classic at this time of year is an overboost trigger as the colder denser air generates more boost triggering the overboost protection in standard chips. Ignition off and on will reset it and boost is restored, undo the boost enhancer a turn and that should get you through the winter.

shims should help the wastegate close and are there to compensate for a week spring,
Tony

I forgot to say my car is totally standard.... with standard factory chipset and control setup - Nothing added - Nothing taken away !.. Deffo wasnt the overboost as the car was up to temp and I hadnt pushed it hard up to the overtaking point... I had a problem with a broken leg on the wastegate actuator valve in the past and this caused the overboost cut out .. This was different feel if you like ... !

I wish I could get on the boat and take the car over to demonsrate the problem Tony but knowing my luck she would be totally fine ...[]

I am going to just drive her on until it gets worse - then I will be able to say for sure []

Could well be a stuck open wastegate or cycling valve then (cycling valve is under the inlet manifold at rear). If the wastegate is stuck open the outlet pipe will heat up as fast as the crossover pipe iginition reset shouldn't fix it though. Boost/exhaust leaks unlikely to fix themselves with an ignition reset. Unless it was a misfire that was stopping it from boosting.
Might also be worth a check on the dump valve they are not the most robust and if it wasnt seating properly the boost could get dumped into the intake - ignition reset shouldn't affect it though!
Havent heard of a cycling valve sticking before.
Good luck!

 

[poprock]

ORIGINAL: robwright

If you have aftermarket chips and non-standard wastegate chances are you have no overboost protection.  That is a risk you run on a modified car.  That is exactly why I have an aftermarket stepper motor boost gauge to keep a check on the boost and an AFR meter to keep an eye on the mixture []  Over boost on the standard wastegate is controlled by the cycling valve, which uses manifold presure to open the wastegate removing exhaust gas pressure from the turbine of the turbo.  I know certainly with the Tial this function does not exist not sure about the Lynsey's though.  Does the Lynsey wastegate have three boost lines attached to it???  If so one of these could still be actuating the standard overboost function of the factory WG.

What I'm assuming is that my wastegate (from Turbosmart, an Aussie company) allows for higher pressure before opening than the original Porsche part, thus allowing more boost before venting"”but because I'm using the standard Porsche chip, that chip measures the boost pressure, detects too much, and shuts things down for safety. Does that sound logical?

 

[robwright]

ORIGINAL: poprock

ORIGINAL: robwright

If you have aftermarket chips and non-standard wastegate chances are you have no overboost protection. That is a risk you run on a modified car. That is exactly why I have an aftermarket stepper motor boost gauge to keep a check on the boost and an AFR meter to keep an eye on the mixture [] Over boost on the standard wastegate is controlled by the cycling valve, which uses manifold presure to open the wastegate removing exhaust gas pressure from the turbine of the turbo. I know certainly with the Tial this function does not exist not sure about the Lynsey's though. Does the Lynsey wastegate have three boost lines attached to it??? If so one of these could still be actuating the standard overboost function of the factory WG.

What I'm assuming is that my wastegate (from Turbosmart, an Aussie company) allows for higher pressure before opening than the original Porsche part, thus allowing more boost before venting"”but because I'm using the standard Porsche chip, that chip measures the boost pressure, detects too much, and shuts things down for safety. Does that sound logical?

Yes it does sound kind of logical but without knowing the specs of your car it is hard to tell. How much boost are you running? If you are running over stock boost then certainly you shouldn't be using standard chips as you run the risk of running dangerously lean. The stock chips won't supply enough fuel to support extra boost. Extra boost without the fuel to support it really does end up with engine meltdown!!!!

 

[VanhireBoys]

Lads
Sorry for dragging this old post up again but I have appeared to cure this issue as well. I had the earlier problem of the running bad under load and that was cured by the DME. I had 2 incidences of no boost since... When I had the bad running issue I orderded a KLR as well as DME... DME landed first and then the KLR landed on Monday...!

I changed out the KLR and Ive had clean boost everytime.. If anybody had suggested the ECU's when I first had problems Id have been very sceptical ... Well you live and learn ...![]

 

[Diver944]

Great news Donal [] I bet your car feels like a totally new animal now

 

[VanhireBoys]

ORIGINAL: Diver944

Great news Donal [] I bet your car feels like a totally new animal now

Thanks Paul.. Yeah she is back to rude health... The vulgar display of supremacy days are back once again []

 

[scam75]

Hi Donal

Have you gave your DME and KLR a bath at some point? A leak into the passenger footwell can cause this?

Stuart

 

[944Turbo]

Was wondering the same thing, being US spec is the battery in the front? hope there isn't a bit of corrosion letting water attack the ecu's (or any other holes in the scuttle area)

 

[VanhireBoys]

Definately valid points there lads and I will check them out.... ! At the time of the last bad running issue I had both KLR and DME open... Both PCB's in both ECU's were in fantastic shape.. No dry joints or damage of any sort to the PCB tracks.. I am thinking component failure with the DME but Im not sure with the KLR as it was intermittent. I am going to examine both in detail here at ahem.. Work.... []

Must take a few snaps of them... Just for the craic... !