Piper 2.25 & PCE just fitted - wow! but boost creep

[paulsmithmk]

I am not surprised - whilst I have the downpipe and cat on my 2.25 as well as an everest I think haven driven rips car the exhaust alone give amazing results. I had my wastegate ported to 20mm - no problems since even in the cold. If you want me to put you in touch with the person that did mine (there are many things I dont want to do myself!!) let me know as you are close by...

[ccb056]

OK so I drove my car for the first time in a few weeks today, outside temp must of been around 1C, maybe 2C...so very cold. Once the car was warmed up (10 mins of normal driving) I opened it up ... awesome acceleration in 2nd, then 3rd....wham... boost stopped with a bang at around 5500rpm (I think...was too busy grinning and watching the road) , engine warning light came on for about 20 seconds then everything went back to normal.

So I presume this is the fabled boost creep.

Given that all I've done is replace by standard exhaust system was a piper 2.25, PCE and sport cat I was quite surprised.

I've read all the threads on boost creep and don't really want to go down the wastegate porting route as that will no doubt cost me a fortune (zero chance of doing it myself so would need to pay a garage to do it) but I was wondering if fitting a kilimanjaro or everest chip might actually help? i.e. because they raise the fuel cutoff limit. Is it likely to help?? Or am I clutching at straws!

I am running the stock chip with 2.5" Piper, PCE, and the 2nd silencer.
The boost creeps up to 0.9 bar and then the wastegate is able to control it.
I have the wastegate ported to 21mm.
The test was done on a 0degC day.
Here is the info: viewtopic.php?f=36&t=21952

[paulous]

I am not surprised - whilst I have the downpipe and cat on my 2.25 as well as an everest I think haven driven rips car the exhaust alone give amazing results. I had my wastegate ported to 20mm - no problems since even in the cold. If you want me to put you in touch with the person that did mine (there are many things I dont want to do myself!!) let me know as you are close by...

Thanks Paul, PM sent.

I drove my car 'enthusiastically' again this morning when it was maybe 1-2C outside and I got the same problem at least 5-6 times Each time it was around 5500-6000rpm and when the boost reached it's maximum showing around 0.75 - 0.80 on the guage (not accurate I know but since fitting this exhaust my guage now boosts just beyond the 0.75 mark compared to previously when it never wnet above 0.5). I even managed to hit it when joining the motorway accelerating in both 4th and 5th doing <ahem> 70mph of course ... boost cutting out on the motorway was interesting to say the least.

So I definitely need to do something.

Quick questions on wastgate porting...

1) Is there a simpletons guide or thread on here anywhere that explains why it's needed? Or can anyone summarise in a few sentences?

2) Will I see any other benefit once ported other than the boost creep going away?

Thanks all,

Paul

P.S. I double checked my ECU today too to make sure it hadn't already been chipped, and it appears to be standard and unchipped. So the awesome uplift I'm getting in boost appears to be entirely down to the 2.25 system with PCE so all credit to Piper. I also went for a drive later in the day when the outside temp was warmer (around 8-9C) and couldn't get it to boost creep. I also literally found myself laughing out loud a couple of times , the transformation in my car's performance is that good! Mucho fun, what a great car!

[ccb056]

Quick questions on wastgate porting...

1) Is there a simpletons guide or thread on here anywhere that explains why it's needed? Or can anyone summarise in a few sentences?

2) Will I see any other benefit once ported other than the boost creep going away?

http://wikilec.9600.org/index.php/Wastegate:_Porting

Essentially the exhaust flows through the exhaust manifold to the turbo where it is separated and goes through both the turbine and the wastegate in parallel, the flows are then combined in the downpipe and go through the precat and the rest of the exhaust system.

Not enough flow through the wastegate means too much flow through the turbine.
Too much flow through the turbine means the turbine spins too much, causing the compressor to spin too much, creating too much pressure in the intake manifold.

By replacing the stock exhaust with an upgraded aftermarket you have decreased the backpressure downstream of the turbo.
The rate at which the turbine spins is directly related to the differential pressure across the turbo (exhaust manifold pressure - exhaust pipe pressure).
Which means by upgrading to a less restrictive exhaust, you have increased the differential pressure across the turbo, resulting in a turbo that will spin faster.

By increasing the diameter of the wastegate, you allow more flow through the wastegate, resulting in less flow the the turbine, resulting in less boost.
The wastegate is controlled by a pneumatic actuator which can keep the wastegate either fully open, fully closed, or anywhere in between by pulsing a signal (% duty cycle) to the actuator.

[paulous]

Fantastic explanation, thankyou! Thats exactly what I needed. Makes sense now.

It does however raise another question in my turbo-novice mind... "allow more flow through the wastegate, resulting in less flow the the turbine, resulting in less boost." ... Does this mean I'm going to see the awesome increase in boost/power resulting from fitting the exahust reduce after porting?? Or will it not be noticable?

[ccb056]

If you have the stock chip then a successful port is defined as seeing a max boost of 0.65 bar.

If you like the added power that comes with the extra boost the best advice is to port the wastegate so that you can control to the 0.65 bar with the stock chip, and then replace the stock chip with a 'Mountain' chip from ESM to bring the boost to a controllable 0.9 bar.

Currently the boost is in an uncontrollable state, which is dangerous.

[TrevorB]

This subject always interests me as I had the Piper 2.25 system fitted last year and at the time saw an improvement in performance.
But like Paul I am a complete novice even more so I have tried to see what boost I get and have seen it at approx 0.65 and once
even saw it peak at 0.9. I have not checked the ECU to see if I have a chip and checking through records do not have any indication
that one has been fitted. With Donington and Ypres trips coming up I am hoping that one of you can look at my car, even have a
drive and get some expert advise on what I have or not in respect of this subject. Do I need to port wastegate, get a piper downpipe,
is it chipped etc. I am keen to understand and learn more and there are plenty of you that will help, I'm sure.
See you at Donington.


Trevor

[chipp]

How have owners of the Piper 2.25 found there system for fit and motorway use.
Over on the Peco/Cybox thread they have mentioned droning which can be alleviated and more worryingly bottoming out.

chipp

[ccb056]

Running with the Piper 2.5, bottoming out is only a problem when going up/down driveways without angling the path. Driving on roads is no problem.