Ok settle in, this could be a long story...........

When I bought the car last October, it seemed to be very quick (I had moved from a 306 gti6 to an my98 terzo), but was overboosting quite badly.

So, as described on here, I cleaned out the Boost solenoid, reset the ECU and hey presto fixed overboost problem. But, it did feel slower, I put this down to me getting use to the extra power and thought nothing of it.

Got speaking to MickWRX (Nice graphics!) at the NBO and he said that he has no probs running 1 bar with a dawes device, but said that I must get a boost gauge before I thought about doing anything.

This I knew to be sound advice and so at the NBO I bought a nice greddy boost gauge, which I fitted that evening.

Left the car as it was till today, so as to monitor what it was doing without a MBC fitted. Car has full decat and induction and forge dump valve, but seems to be standard everywhere else.

I had read on here that normal boost pressure was meant to be 0.9 bar, so was a bit surprised when all I have been seeing was 0.5 - 0.6. Now I have fitted a MBC and can only get it to rise to 0.7 (with the controller nearly screwed out!), so figure there must be something wrong.

I have read to check the wastegate/actuator and its clip,as the turbo will only boost to 0.5 bar if anything faulty with it, but I have no idea what to check ie where is the clip and how can you check a wastegate?

Is there anything else I should be checking?

I have reset it all back to normal for now as I dont wanna blow the engine.

Any help would be greatly appreciated.

Cheers

Jonny

 

Sounds like you have a boost leek somewhere ? Do you have the standard Dumpvalve on ? Check the Boost pressure pipeline that runs to it. Thats the first place i'd look.

 

take it down to the clinic they'll sort it

 

Cheers for that. Already done that. I dont have the original dump valve as this one came with the car, but it runs straight from the manifold and is one silicone hose about 2 foot long, with no splits or cracks.

Cheers

Jonny

 

Now that I would love to do but unfortunately, the family holiday is coming up and spending of money has been stopped until the end of July!

Thought it must be quite simple really as it was overboosting then under boosting, I think it has been doing this since I cleaned the boost solenoid. The weird thing is that even with the boost controller on, that bypasses the solenoid, I was still getting just over 0.5 bar.

 

Ok.. I'd check all the other pipes and hoses aswell. It is possible to pressure test your pipework with with a tyre pump with a pressure gauge on it. Just tap into the manifold where the vaccum pipe from the Dumpvalve goes. Connect the pump up and pressurise the system. If it pressurises above what you are seeing then you don't have any leaks. If it won't hold the pressure then you have !

 

0.5 will be it running in safe mode, but cel light should really come on if it where that ?

boost leek does sound more like the problem. It only takes a very little hole in a pipe to cause this.

Check the top and bottom pipes from the bost solenoid for good fit and small cracks or holes, espeically where the pipes bend. and as you correctly state check pipes to the turbo too

I think the car should hit 0.9 in 5th and possibly drop of a little to 0.8.

let me know how you get on mate.

like I said at the NBO if you fit a Dawes device or similar that will remove the solenoids input to the boost level and you will be able to mechanically set it to what you want, fuel cut permitting

good to meet you at the NBO

 

In 1 of the small pipes from the boost solenoid & actuator pipes somewhere in those small pipes there is a tiny valve it could be the prob it controls the boost .think bigger valve less boost smaller valve more boost hope this helps.

 

I would say if the leak was at the inlet to theboost solenoid then it would be overboosting as it would be bleeding off boost pressure before the solenoid.

 

Cheers Mick,

was good to chat with you too, I shall try and make it to a meet so I can meet the rest of you. Tried what you said at NBO, so I can assume that the pipes to the wastegate and the impellor side of turbo are ok as they were new with the dawes.............. Oh and no CEL light and I know its working cos I had to replace the speed sensor recently, but I think I shall do a diagnostic tomorrow too and see if any codes appear.

Quite like the idea of pressurising the manifold though, I have a compressor so I can use that to pressurise the system. Shall try that tomorrow and post the results.

Any ideas on the wastegate actuator clip? Read it here:- http://bbs.scoobynet.co.uk/showthrea...boost+problems 2nd to last post.

Yeah that is what I thought to as basically all the dawes does is bleed off some of the pressure to stop the actuator activating, I think?

 

Not sure about what pipework you have on these Scoobs. But if you find that it's not holding pressure? Then you will have to pressurise it in sections to fing exactly where the leak is.. !

 

The boost controller DAWES mounts in-line between the intake manifold (or turbo nipple) and the wastegate. The controller holds the signal from the wastegate until the desired boost level is reached, (you will have set this by twisting the nuts.and monitoring your boost guage)
If the wastegate is letting the gasses out before the boost has hit the limit there could possibly be a leak somewhere on the pipe work.

If the dawes is not fitted yet, as said, correctly, the output hose from the boost solenoid could be leaking, either way way it sound like your loosing pressure some where before the wastgate.

I find this a really dificult subject to get accross lol...

 

Make sure all pipes are connected to the waste gate control valve the right way.

Bottom of controller to turbo and top to intake duct.
Check for splits in pipes, make sure the restrictor is in place other wise the waste gate will open at about 0.6 bar.
To cheack waste gate you need a MITY VAC
Waste gate commence opening = 63.3 to 65.4 Kpa
Waste gate fully open = 104.6 to 106.7 Kpa
Max rod movement = 9 to 10 mm

If you live near York I‘ve got a unit at Ellvigton
Could have a look for you if your still stuck.

 

Another thing to check first, but not so obvious. When you put key in the ignition and turn it to the accessory position (just before starting engine) does the engine light light up ? Its not a common thing , but if there is a fault that the previous owner/dealer had ,then they could have removed the bulb so it dosnt look like theres a fault at all. if the bulb is missing or blown it'll cost 10p for a new one then you can retrieve a fault code.
Also try reversing the dump valve to see if it holds pressure, if it does then the valve is leaking.

 

Good morning all and thanks for your responses!

Been hectic here at work as we are running a radio station for a week!

I have checked the CEL light and it definately works and is not coming on, also on a diagnostic shows no error codes.

On the way to work this morning the car boosted to 1.2bar!!!!! And looked like it was going to keep going up, till I panicked and backed off.

I am going to reset the dawes and start again. My question is will it boost more when cold?

One question though is, this restrictor, is it in the feed pipe to the boost control solenoid or is it between the actuator and turbo nipple, and am I supposed to still have it whilst using the Dawes?

Cheers all for the advice, Mick, I will have to come to a meet now so you can check it out lol! (at least thats what I shall tell the missus)

Jonny

 

Aha, eureka and all that, found one of the pipes had been a bit too close to the lambda sensor and had melted a hole in it, that explains the massive boost this morning, and in a way has shown me that it will boost that high if I was that way inclined.

I have also put in, an in car boost controller as well so we shall have to see if that makes a difference.

Turning into a real mission now! At least I understand how turbo's work now and what all the bits do.

I shall post my findings.

Cheers

Jonny

 

Hi Jonny and good morning mate

One tube wants to go to the wastgate actuator nipple,actually on the wastegate actuator with no valves inbetween just straight through pipe, The other pipe from the dawes wants to go to the turbo out, there should be a nipple down there perfect for the job that used to be used by the solenoid ?
no valves inbetween any of these tubes hoses either in or out of the wastgate actuator or turbo air body (out pipe)


Wastgate actuator -----tube------ dawes-----tube-----Turbo air out -----------intercooler


The hoses from the now redundent boost solenoid just require looping, the hose out of the solenoid put onto the nipple in

The standard ECU will only fuel to about 1bar max possibly1.1 but then will hit fuel cut and feel like its trying to throw you through the winscreen, try to avoid this has its obviously running zero fuel for the seconds this happens.

hope you follow me mate

 

Yeah cheers Mick, thats exactly as I have it, apart from its a 2 port boost solenoid, so I have blocked the redundant hose with a bolt and jubilee clip as there is nowhere to loop it back to. Will be going out in it a dinner so I shall see how it performs.

Cheers fella!

Jonny

 

Sorry mate missed your eureka post, its looking good hitting them boost levels without fuel cut possibly uprated ecu and pump

glad its sorted mate

 

Yeah, I was wondering about fuel cut. Its a UK Terzo MY98 so is one of the weird in between models, when it comes to the engine and electrics. Unfortunately I don't know what had been done before I bought it and I have done not very much at all.

AFAIK it has a standard brain and no other mods, i've had the brain out before and it looks completely standard (Think its either 6s or 7s 3 plug one with no soldered on bits to the pcb inside) as for fuel cut defender, I have no idea what one looks like or where it goes.



In't this fun!

Jonny

 

Here's a thought though, maybe the boost gauge is lying...........

ha ha ha ha ha ha ha ha ha, think I may be getting delirious, and now this work stuff is getting in the way of tuning!

 

your letting work get infront of tuning

how dare you ( in peter kay voice )

 

Ha ha ha Max and Paddy, quality! <A Team> Doo D Do Doo, Do Doo Dooooo</A Team> Maybe its a job for Magnet and Steel!

Plus I have to be careful here. not because of work, just because the missus works here too and she may see me in the car park under the bonnet ha ha!

 

Jobs a Carrot!!!

0.9 bar boost hit ok can go all the way up to 1.2 with no fuel cut or any probs, but I have set it to 1 bar. This is with the in car boost controller, could have been a faulty (possibly blocked) dawes, but, hey, who cares, it works now.

It has dramatically improved the car and it feels more like it did when I first got it.

A big thank you to all on here who chipped in!

Jonny

 

Just by the by, AFAIK the fuel cut is determined by the map sensor and newer cars have a 3 bar map sensor fitted as standard, hence no fuel cut at 1.2 bar where as the early cars have, I think, a 1.2 bar map sensor.
Had mine changed to resolve my fuel cut issue