Wastegate

[BertBeck]

Hi, I keep seeing issues on here related to the wastegate and have had a look at Wiki etc.
I dont actually have any issues but Ive had my Elan for 7 years now and have never done any maitenence on the turbo.
How often should the wastegate be ported or whatever it is you have to do. Im assuming it might be due after 7 years?.
What are the symptoms of a stuck wastegate, is it something I should be having a look at after at least 7 years of non maintenence?

Cheers, Charlie

[Rambo]

If it ain't broke, don't fix it. Providing you are getting the correct boost, can hear the wastegate flutter and use the car regularly you don't need to do anything.

And you certainly don't need to port the wastegate unless you are considering a larger diameter exhaust. Once ported, that's it. No need for any further reporting.

[BertBeck]

Cheers, yeh it seems fine so Ill leave it

Regards Charlie

[Rambo]

If you do actually need to something go your wastegate and/or actuator, look here ........

http://wikilec.com/view/Wastegate:_Releasing

[BertBeck]

Yeh I did have a look at that earlier, thanks

Charlie

[Tuga2112]

If it ain't broke, don't fix it. Providing you are getting the correct boost, can hear the wastegate flutter and use the car regularly you don't need to do anything.

And you certainly don't need to port the wastegate unless you are considering a larger diameter exhaust. Once ported, that's it. No need for any further reporting.

its worth noting that even if you have a bigger bore exaust, you may not need the wastegate ported either.
my exaust is bigger than factory but not by a lot, and i dont have boost creep issues. some people report boost creep with the same bore as mine, but it doesnt happen with all cars.

[Rambo]

Very true, neither of mine are ported (PNM and Piper full systems)

[MPx]

I didn't realise the boost creep was just for the larger exhausts. I ported mine when I put the Piper 2.25 on, but that coincided with fitting one of Alan's switcher mountain chips, and I thought it was the combination of big exhaust and remapping that could result in boost creep unless ported? Whatever, I've never had boost creep either!

[dapinky]

I'm in the same camp as Mike here - never had it, BUT, when I fitted the 2 1/4" Piper and Everest chip I did it at the same time to avoid it happening (if mine had been one of the cars susceptible to it!)

It is one of those things where the actual boost creep is a good thing in measured doses, as it increases the power from the engine. It is caused when 'too much' gas comes from the combustion chamber, into the exhaust manifold, and thus drive the turbo blades.

If it goes 'too fast' then it makes 'too much' boost.

At that point, the ECU (and other magic sensors in combination!) tells the wastegate to open, and the 'excess' exhaust gas goes straight through to to downpipe without going through the turbo, and thus the speed of rotation drops again to the proper level, and when it does so, the wastegate closes again, and the turbo gets the 'right' flow to get the 'right' boost.

If the engine produces more airflow than the original design will handle (free-flowing exhaust, MBC, Bleed-valve or whatever) then the wastegate cannot flow enough excess gas, and the pressure just builds up until you lift your foot off the pedal, or the ECU decides that it has got to a critical situation, and simple 'switches off' the power...... this gives a very sudden retardation of the car, and it is reported that you would hit your head on the windsceen if not restrained. Once the situation has resolved itself, the ECU will go back to 'normal' mode - or at least, the low power circuit doesn't stay in operation.

It is this increase in boost pressure between the 'designed' 0.65(ish) bar and when the cut-off happens which is the "boost-creep" area.

To avoid the switch-off, the choices are to either trick the ECU into not worrying about it (MBS, bleed-valve) and allow the excess boost to just build up, giving lots more power, until the engine just melts!

Okay, that is an over-simplification, but the fact remains that all the Turbo actually does is force extra air into the cylinders, and at some point, there will be so much air that the fuel injectors do not (because of the ECU settings) or can not (because of their physical size) flow enough fuel into the cylinders, and the mixture becomes too weak. A lean mixture will burn hotter than a rich one, and the temperature will increase in very short time, in a small area. At some point, something (usually the piston) will start to melt, and because of the extreme forces on it, will deform, and then the whole thing goes bang!

Now, I haven't mentioned the Everest chip yet, and that is because it can be both a source of the issue, AND a rectification.

As I said, it is all controlled by the ECU - but the Everest chip allows the boost to go up to 0.9, by accurately controlling the injectors to still flow sufficient fuel. The standard injectors will flow sufficient fuel to go to 0.91bar - but only if they are still in "as new" condition, even a small blockage will cut that flow (unknown to the ECU!!) and can cause issues....... clearly, bigger injectors could allow higher boost by allowing more fuel (but over 1.0 bar will require a change of MAP sensor from a 2-bar to a 3-bar version).... but that is getting into the realms of the specialised owners/drivers/engineers, and is beyond the needs of most of us.

Because of these factors, the Everest can stop (or prevent) overboost by increasing fuel flow in a car with good injectors.....but can cause it by allowing the boost to increase to 0.9bar before the "safety" features activate (okay, it won't actually 'cause' it, because it was happening anyway, but it may mean you encounter it more often as you are now deliberately letting your boost go higher than original, as opposed to it happening accidentally.)

Boost creep = good, Overboost = bad.

So, this is where the "porting" comes in - the standard wastegate is approx 16mm in diameter (hole/bore size) and if it cannot flow enough waste gas through it, we can simply increase the diameter so more gas gets through, and the pressure doesn't get high enough inside the manifold to cause Overboost. The flap which covers the hole is a set size, and it is widely accepted that the "biggest" we can make the wastegate hole is 20/21mm before running the risk of the flap not sealing, and the wastegate being (slightly) open permanently, thus reducing any boost that is wanted.

[HJ2]

Filling up the Wiki again Dave?