Overboost

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Re: Overboost

Postby lotusflasherman » Thu 07.01.2016, 20:19

lotusles wrote:I am in the process of fitting timing belt etc and would eventually like to fit a bigger bore exhaust to naturally increase bhp. Would I do any damage if I was to remove and ream out the waste gate now but not fit an exhaust until some time later?

Thanks


No. All you will be doing is removing the 'Achilles Heel' before it becomes a nuisance. As long as the flap valve still covers the enlarged wastegate port and you don't leave any swarf or abrasive material in the turbo it should be fine. Wastegate can't really be too big as the valve controls flow through it, but it can certainly be too small. There's a guide on Wikilec that HJ2 provided a link to on the first reply to the original post, so I won't repeat it here...
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Re: Overboost

Postby lotusles » Thu 07.01.2016, 21:01

lotusflasherman wrote:
lotusles wrote:I am in the process of fitting timing belt etc and would eventually like to fit a bigger bore exhaust to naturally increase bhp. Would I do any damage if I was to remove and ream out the waste gate now but not fit an exhaust until some time later?

Thanks


No. All you will be doing is removing the 'Achilles Heel' before it becomes a nuisance. As long as the flap valve still covers the enlarged wastegate port and you don't leave any swarf or abrasive material in the turbo it should be fine. Wastegate can't really be too big as the valve controls flow through it, but it can certainly be too small. There's a guide on Wikilec that HJ2 provided a link to on the first reply to the original post, so I won't repeat it here...


Thank you, it was the original ,link that got me thinking :D
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Re: Overboost

Postby Elanlover » Thu 07.01.2016, 21:12

lotusles wrote:I am in the process of fitting timing belt etc and would eventually like to fit a bigger bore exhaust to naturally increase bhp. Would I do any damage if I was to remove and ream out the waste gate now but not fit an exhaust until some time later?

Thanks


I've yet to hear of any negative impact from porting the wastegate even if the standard bore exhaust is used. I believe you'll be just fine.
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Re: Overboost

Postby rip » Fri 08.01.2016, 12:03

lotusflasherman wrote:
lotusles wrote:I am in the process of fitting timing belt etc and would eventually like to fit a bigger bore exhaust to naturally increase bhp. Would I do any damage if I was to remove and ream out the waste gate now but not fit an exhaust until some time later?

Thanks


No. All you will be doing is removing the 'Achilles Heel' before it becomes a nuisance. As long as the flap valve still covers the enlarged wastegate port and you don't leave any swarf or abrasive material in the turbo it should be fine. Wastegate can't really be too big as the valve controls flow through it, but it can certainly be too small. There's a guide on Wikilec that HJ2 provided a link to on the first reply to the original post, so I won't repeat it here...


:agree:

I am sure the wastegate would have been designed to open & close fully in normal operation. A larger wastegate should not need to open fully with a std exhaust but this should not be a problem.
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Re: Overboost

Postby Wallzaveerz » Wed 06.03.2019, 22:34

I've now experienced overboost. Had the car out for its first proper run last Sunday. Out at 8am in cold damp foggy weather. Any enthusiastic use of the throttle resulted in a lowered rev limit and the EML flashing. Going back home at noon when it had warmed and dried up considerably it was perfectly fine.
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Re: Overboost

Postby TrevorB » Sat 17.10.2020, 19:15

I'm thinking I need to get my wastegate ported?!
I took Merlot out today and once it got really warmed up and I was on my way home, on a few occasions, when accelerating through the gears, at approx 4000rpm in 2nd and 3rd gear the engine juddered and didn't want to go any harder. Presumably this is an indication of over boost? I had no indication from engine management of any problems. Otherwise everything was fine and she run perfectly. Did not have this problem early in the run when I was also pushing through the gears.
Confirmation of my thoughts or any other diagnosis much appreciated.
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Re: Overboost

Postby HJ2 » Sat 17.10.2020, 20:26

Hi Trevor,

Did you do the paperclip test?
Any overboost will be stored

If no CEL and no errors stored I doubt if it was overboost you experienced.
You also can recognise overboost at better then normal performance just before the fuel cutoff takes you out of the dream :mrgreen:

What were the last changes / service on the car before the overboost appeared?

I think sparkplugs with the wrong gap or sticky wastegate, so wiggle it!
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Re: Overboost

Postby alan e » Sat 17.10.2020, 21:33

Hi Trevor It's worth checking the timing it can move on our cars, i don't think Merlot got a chip fitted so when it cuts out what is the boost gauge reading.
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Re: Overboost

Postby GeoffSmith » Sat 17.10.2020, 21:37

If your nose isn't broken then it's probably not overboost.
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Re: Overboost

Postby esprit888 » Sun 18.10.2020, 00:17

GeoffSmith wrote:If your nose isn't broken then it's probably not overboost.

:agree:
:lol: :lol:
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Re: Overboost

Postby HJ2 » Sun 18.10.2020, 08:44

... or a broken nose gets you into dreaming... :bananasex:
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Re: Overboost

Postby TrevorB » Sun 18.10.2020, 14:10

HJ2 wrote:Hi Trevor,

Did you do the paperclip test?
Any overboost will be stored

Hi Henk, I will do a test next opportunity I get.

If no CEL and no errors stored I doubt if it was overboost you experienced.
You also can recognise overboost at better then normal performance just before the fuel cutoff takes you out of the dream :mrgreen:

What were the last changes / service on the car before the overboost appeared?

Plugs were changed at last service in May.

I think sparkplugs with the wrong gap or sticky wastegate, so wiggle it!


I will try the wastegate wiggle.

alan e wrote:Hi Trevor It's worth checking the timing it can move on our cars, i don't think Merlot got a chip fitted so when it cuts out what is the boost gauge reading.


Alan, didn't look at boost gauge as I was concentrating on whethere CEL was coming on. Not sure when the next opportunity will be to take her out again to check.

GeoffSmith wrote:If your nose isn't broken then it's probably not overboost.


Geoff, nose is still intact :D
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Re: Overboost

Postby HJ2 » Sun 18.10.2020, 14:36

And you checked the plug gap?
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Re: Overboost

Postby Rocklobster » Sun 18.10.2020, 15:20

It may be overboost that you're experiencing, but that doesn't mean the wastegate needs porting. If the wastegate was the right size last year, then unless you've put a big exhaust on, it's still the right size.

More likely that the wastegate linkage has seized or become stiff (hence the wastegate wiggle) or you may have a pressure leak and the wastegate actuator isn't actuating. There is a post on here somewhere about testing the wastegate actuator with a pump. If you find that the wiggle frees things up, wipe a generous amount of ceramic grease around the linkage. Not any other type of grease.
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