Hi all,

*Apologies for my general lack of technical understanding - the last time I touched my car was 3 years ago and I've forgotten a lot!*

I've recently signed up following a 3 year break from cars and the stresses that surround them! I am however now itching to get my Four back on the road, but before I do, there were a couple of issues that need addressing; wheel bearing replacement, possible DP repair or replacement etc however the most important one is that the DV doesn't seem to dump plus I suffer from large over-boost. Firstly, I'm unsure whether the two are related, but it would seem logical.

I initially thought that perhaps the Actuator was jammed which wasn't allowing the internal wastegate to open and I was over-boosting (if that's even how it works?!), but tonight I took off one of the boost pipes and put a few PSI through - the actuator moved and I could hear the wastegate open (I think.... )

Moving forwards I'm not sure where to look? I guess I'll take off all the vacuum pipes for inspection / to make sure none are pinched and maybe look at the DV, but aside from that, I'm stumped?

I've got an EBC - could this be to blame? I appreciate it might be linked to the boost, but I would assume the DV would still function?

Incidentally the DP has got a hairline crack in it - I'll replace / repair this as a matter of course however it feels unlikely that it's connected to the above?

I would gratefully welcome any advise / experience/ ideas.

Thank you in advance.

Squirrell

The DV is unlikely to be related to the overboost as the DV should be firmly shut on boost, opening only when the throttle is lifted to release pressure.

Lack of DV operation is likely to be the DV itself stuck shut, or could be split / missing hose from dump valve to inlet manifold.

If the wastegate appears to open with pressure applied to the actuator, then try plumbing the small outlet from the turbo direct to the actuator. It should then boost to about 0.5 bar. If it still overboosts then make sure the other port of the actuator is blocked (it normally goes to the ECU controlled bleed valve, but this is normally disabled when running an EBC,

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Hi Nibbles,

Thank you for your response.

Thinking logically it's fairly obvious that the over-boost and DV operation 'should' be separate issues - subject I guess to vacuum pipes all being sound?

I'll check all hoses and DV operation in isolation.

Regarding the overboost - it looks like I'd make more progress is the car was on the road so that I can tinker and test. With that in mind I will MOT it first then look into this in more detail.

One final wildcard that I thought of (after scouring some forums) is that I should check my gain on the EBC. I assume I'm right in thinking the gain controls how quickly the turbo spools, therefore if too aggressive, could spike to fuel cut and give the impression of over-boost?

Thank you for your help so far - much appreciated.

Squirrell.

Sounds like you are on the right track. If I had the problem of overboosting or 'spiking' then I'd suspect the gain setting on the EBC first and turn it down. If that didn't do the trick then I'd probably take the EBC out of the loop and reconnect the actuator and TVSV to confirm that all is well with the standard setup and take things from there.

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Don
GT4DC Chairman
1994 Toyota Celica GT-Four ST205WRC JDM 269bhp @ 0.9bar
1994 Toyota Celica GT-Four Special GT 590bhp @ 1.8bar
1989 Van Diemen RF88/89 Formula Ford 1600
2008 Nissan Patrol GU 3.0L ZD30DDTi 154bhp

EBC gain was set to 10! Quick bit of google and apparently this is far too high and 5 is a more suitable level. I've currently taken it back to 0 and will review on the road post MOT.

Hopefully that was an easy fix!

Now onto the DV.....

.... The DV was also an easy fix too, I think. I've got an hks ssqv and when I received it there was a inline vacuum filter. I'd installed this and used it for years......

Over the period it had filtered out some stuff and as a result got clogged. I took the filter out and the DV dumps once more (albeit not sequential, but I believe i need boost for it to do that?)

Slightly concerning that the filter got clogged however.

seems to be different to all the cars, blitz recommend 5, I use 5 and ratios of 30, 40, 57 and 62 and this achieves 1.07-1.12 and 1.18 bar bar respectively on the higher ratios with the gain at 5.

I recently changed the gain to 15 to see what difference we have, although pulls slightly better down low the overall acceleration after about 4k feels about the same.

Some suffer spikes though and some don't seem to, at present I am yet to spike with the 15 gain setting.