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Inconsistent Boost - Now with Video


Samurai 20V

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Hi guys..

 

My car seems to be behaving strangely.

 

In 4th and 5th gear mainly, at about 3000rpm, if I floor the accelerator the car boost to around 0.6, then picks up to 0.8, then drops again.. This goes as long as I have the car on WOT.

 

Previously, when I first got the car, it used to do it once then run smoothly, but now it seems to be consistently fluctuating. Since then the only mechanical changes have been a new intake, new FMIC & removal of the tailpipe silencer.

 

Any ideas? Should I be concerned?

 

Thanks in advance.

Edited by Samurai 20V (see edit history)
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So floor at 3000rpm and you get 0.6, when it goes to 0.8 I assume that's second turbo kicking in, then it tails off? How quickly does it tail off and what does it tail off to? Check there aren't any splits in boost hoses or vacuum hoses attached to any actuators I guess.

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ive known people to have boost problems after fitting new IC. even though you def checked the clamps maybe its worth just re-checking and going over the clamps again? such a small thing could have different effects, if your still stumped and considering you've just fitted it and suddenly youve a problem think its worth a pop :) GL!

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So floor at 3000rpm and you get 0.6, when it goes to 0.8 I assume that's second turbo kicking in, then it tails off? How quickly does it tail off and what does it tail off to? Check there aren't any splits in boost hoses or vacuum hoses attached to any actuators I guess.

 

Well I drove it again yesterday, it was fluctuating between 0.6 and 0.8 bet 3000rpm & 4000rpm and did eventually tail off at 0.7bar after 4000rpm, fairly quickly. Different to when I drove it earlier in the day, it was fluctuating all the time after 4000rpm..

 

Will check up all the boost & vac hoses and FMIC clamps..

Edited by Samurai 20V (see edit history)
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ive known people to have boost problems after fitting new IC. even though you def checked the clamps maybe its worth just re-checking and going over the clamps again? such a small thing could have different effects, if your still stumped and considering you've just fitted it and suddenly youve a problem think its worth a pop :) GL!

 

I think thats a good idea, i need to adjust the bumper anyway so its worth a check.

 

Will drive it again today to reconfirm the behaviour..

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Ok, update on my situation.. I figured out that my defi gauge can record the issues with the boost, rather dumb on my part.. So I have a video of what the boost is doing in my car.. Please can someone tell me if this is normal or not.

 

This was done at WOT on 4th gear at around 3500rpm till about 5000rpm, then long pause for some traffic and WOT on 5th gear from 4000 to 5000rpm...

 

Car is stock boost, both cats are in, exhaust, FMIC and intake.

 

The cars behavior is a bit different from my original post..

 

image

Edited by Samurai 20V (see edit history)
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As far as boost levels go and the transition from 1st to 2nd turbo it looks fine. The needle is oscilating quite a bit on 2nd turbo like mine used to do. I fixed what I thought was a potential boost leak and then sprayed WD40 on the actuators and moved them back and forth and it fixed it. So it was one of the two causing the problem.

 

I also have that boost guage with recording feature. Took me a little while before I realised too. Cool huh :) In fact I have a video of a recording of my boost i'll see if I can dig it out for you to compare.

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As far as boost levels go and the transition from 1st to 2nd turbo it looks fine. The needle is oscilating quite a bit on 2nd turbo like mine used to do. I fixed what I thought was a potential boost leak and then sprayed WD40 on the actuators and moved them back and forth and it fixed it. So it was one of the two causing the problem.

 

I also have that boost guage with recording feature. Took me a little while before I realised too. Cool huh :) In fact I have a video of a recording of my boost i'll see if I can dig it out for you to compare.

 

Ok, good to know that the turbos are operating fine...

 

One of the actuator rods does look a bit dirty and oily, will give it a good cleanup and see from there..

 

Yeah, the defi gauges are top quality stuff, I want to get the Oil temp and possibly fuel pressure..IF you could find the video that would be cool.

 

Thanks mate.

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Found one of the vids. I think I was just after 3250rpm in 3rd so didn't really get much chance to build up full boost on the first turbo but you can see it dips a bit. My EGCV VSV actuator rod (the one behind and underneath the 1st turbo) was very stiff and difficult to move (and difficult to get to!), all the other seemed to move relatively freely, so my thinking is that it might've been stuck and couldn't fully open so choking up the exhaust and making it difficult for turbo 2 to create boost. Seems logical to me as the issue was only on 2nd turbo.

 

I think my needle was moving around a bit more than yours, and you do get a little bit more movement depending on where you've tapped the guage feed from so maybe it's fine.

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Found one of the vids. I think I was just after 3250rpm in 3rd so didn't really get much chance to build up full boost on the first turbo but you can see it dips a bit. My EGCV VSV actuator rod (the one behind and underneath the 1st turbo) was very stiff and difficult to move (and difficult to get to!), all the other seemed to move relatively freely, so my thinking is that it might've been stuck and couldn't fully open so choking up the exhaust and making it difficult for turbo 2 to create boost. Seems logical to me as the issue was only on 2nd turbo.

 

I think my needle was moving around a bit more than yours, and you do get a little bit more movement depending on where you've tapped the guage feed from so maybe it's fine.

 

Thanks..

 

I will take a look at those actuator rods, clean them up and see from there.

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