Unusual boost leaks ?

Discussion and technical advice the SW20 MR2. 3S-GTE, 3S-GE, 3S-FE etc
Anything and everything to do with maintenance, modifications and electrical is in here for the Mk2.

Moderators: IMOC Moderators, IMOC Committee Members

MartinF
Posts: 494
Joined: Thu Sep 01, 2011 8:27 pm
Location: Essex
Contact:

Re: Unusual boost leaks ?

Post by MartinF »

So just to add to this I have performed a compression test and a leakdown test.

1 - 180psi - 20%
2 - 179psi - 30%
3 - 180psi - 30%
4 - 179psi - 30%

So at least I know that my engine is in good health even if the mystery thickens about the boost leak.
Blue Lexus RCF
Black MKIV UK Manual Supra
Green MK2 MR2 Tin Top
MartinF
Posts: 494
Joined: Thu Sep 01, 2011 8:27 pm
Location: Essex
Contact:

Re: Unusual boost leaks ?

Post by MartinF »

So to bring this one to closure, and to help any other poor souls who end up battling with a similar issue......

My car ended up quite consistently building boost to around 14psi and then dropping to around 4psi between 5k -5.5k RPM. So after spending many an hour online researching, pressure testing, reverting back to stock boost control etc, I finally gave in and took it to TDI for them to load up on their dyno.

It turned out to be a broken VTV on the recriculating valve... ](*,)

As soon as this was bypassed the car held boost fine all the way upto redline.

I am very happy that the issue is now resolved, but for the life of me can't understand how this failure only showed up at 5k+ RPM ... but is definitely sorted.

So as part of the diagnosis i ended up with the obligatory power graph, see below. 208BHP at the hubs is not bad for an old Rev1 engine running a CT20B on stock ECU with Walbro at around 14psi.

Image
Blue Lexus RCF
Black MKIV UK Manual Supra
Green MK2 MR2 Tin Top
rev2rich
Posts: 519
Joined: Thu Dec 17, 2009 4:43 pm

Re: Unusual boost leaks ?

Post by rev2rich »

Nice to see :thumleft: .... Simple things make so much hard work ](*,)

Unrelated was my car still their lol :thumleft:
MartinF
Posts: 494
Joined: Thu Sep 01, 2011 8:27 pm
Location: Essex
Contact:

Re: Unusual boost leaks ?

Post by MartinF »

Is yours the grey one ? Didn't look that closely at the other cars but saw a grey MR2 there.
Blue Lexus RCF
Black MKIV UK Manual Supra
Green MK2 MR2 Tin Top
rev2rich
Posts: 519
Joined: Thu Dec 17, 2009 4:43 pm

Re: Unusual boost leaks ?

Post by rev2rich »

Ya that's mine :roll:
mrfil13
Posts: 1102
Joined: Fri Jun 23, 2006 7:18 pm
Location: Cambridge (ish)

Re: Unusual boost leaks ?

Post by mrfil13 »

Glad its finally sorted.

Out of interest how did they bypass the recirc valve?
MartinF
Posts: 494
Joined: Thu Sep 01, 2011 8:27 pm
Location: Essex
Contact:

Re: Unusual boost leaks ?

Post by MartinF »

It wasn't the recirc valve they bypassed but the VTV which helps control it.

Pic showing it bypassed.
Image

And how it should be;
Image
Blue Lexus RCF
Black MKIV UK Manual Supra
Green MK2 MR2 Tin Top
SonicSW20
Posts: 3681
Joined: Mon Nov 29, 2010 7:54 pm

Re: Unusual boost leaks ?

Post by SonicSW20 »

Oh! I just assumed that was in place.

Yes, as you discovered, the VTV is vital to the operation of the BPV!
MartinF
Posts: 494
Joined: Thu Sep 01, 2011 8:27 pm
Location: Essex
Contact:

Re: Unusual boost leaks ?

Post by MartinF »

Oh yes it was there, but just faulty.

It was bypasssed (as per the first pic) and now holds boost to the redline. Last night I fitted a spare that i had (as would prefer for things to work as Toyota intended) and it did the same thing so seems like I have two faulty VTV's.

Have just ordered a new one.
Blue Lexus RCF
Black MKIV UK Manual Supra
Green MK2 MR2 Tin Top
SonicSW20
Posts: 3681
Joined: Mon Nov 29, 2010 7:54 pm

Re: Unusual boost leaks ?

Post by SonicSW20 »

Was it fitted the right way round? Its directional.
User avatar
Ryan S
IMOC Moderator
Posts: 10902
Joined: Sat Dec 10, 2005 1:32 pm
Location: Bonnie Dundee
Contact:

Re: Unusual boost leaks ?

Post by Ryan S »

SonicSW20 wrote:Was it fitted the right way round? Its directional.


As above. Switch it around and see how you get on.
MartinF
Posts: 494
Joined: Thu Sep 01, 2011 8:27 pm
Location: Essex
Contact:

Re: Unusual boost leaks ?

Post by MartinF »

It looks correct to me, black side (port B) towards the gearbox end of the engine.
Blue Lexus RCF
Black MKIV UK Manual Supra
Green MK2 MR2 Tin Top
steven63
Posts: 63
Joined: Fri Nov 28, 2014 9:24 pm
Location: preston

had 250whp on a rev2 with those mods

Post by steven63 »

MartinF wrote:So to bring this one to closure, and to help any other poor souls who end up battling with a similar issue......

My car ended up quite consistently building boost to around 14psi and then dropping to around 4psi between 5k -5.5k RPM. So after spending many an hour online researching, pressure testing, reverting back to stock boost control etc, I finally gave in and took it to TDI for them to load up on their dyno.

It turned out to be a broken VTV on the recriculating valve... ](*,)

As soon as this was bypassed the car held boost fine all the way upto redline.

I am very happy that the issue is now resolved, but for the life of me can't understand how this failure only showed up at 5k+ RPM ... but is definitely sorted.

So as part of the diagnosis i ended up with the obligatory power graph, see below. 208BHP at the hubs is not bad for an old Rev1 engine running a CT20B on stock ECU with Walbro at around 14psi.

Image Replaced With URL For Quote http://mkivsupraownersclub.com/images/M ... une-19.jpg
hojoos
Posts: 19
Joined: Sat Jan 18, 2020 2:40 pm

Re: Unusual boost leaks ?

Post by hojoos »

Sounds like your wastegate might be getting stuck open, perhaps?
Post Reply

Return to “MR2 MK2 1990 - 1999 NA & Turbo”