T5 standard boost pressure

[Turbodave]

Easiest way is to make a home brew pressure tester, bung with a schraider valve and pressurise with a bike pump,i used to have a kit for my Audi S2, saved alot of time!!

Funnily enough, I mentioned this on another forum and got laughed at. My "other" car is a turbo too and has 3" stainless steel boost pipes and seems to suffer boost leaks regulary, so my plan was to drill a small hole in one of the pipes and fit a car tyre valve then seal it. Thus I figured I could pressurise the system and look for leaks.

Granted it can't check the entire system as it's never gooing to be 100% air tight but by making a temporarly seal at the air flow meter and throttle body you could in theory test smaller sections of the intake system, I figured it'd be good for testing the intercooler and it's pipework but then again wouldn't be any good on the vacuum system. But if anybody has any suggestions, it'd be appreciated.

Really don't want this thing to turn into another project... however I do want it to be right and the fact it's boost like an asthmatic on a fag break isn't good, no point trying to find more power if it isn't even making standard power.

[Turbodave]

Further information needed gents...

Successfully removed the turbo heat shield (fun...) and had a look at the actuator adjustment in a view to curing why the car is boosting so low on the gauge. I've removed the actuator arm from the wastegate arm, with the wastegate full closed I need to pull the actuator rod out about 2mm in order for it to locate on it's pin. Now to me, that should be enough preload... however given it's age, would it be worth winding the arm in a turn or two, in essence increasing the preload??

I've also checked the vacuums and boost pipes as best I can and can't see anything obvious bar the inlet boost hose that runs from the intercooler over the head and into the turbo seems very loose, but assume this is due to it being rubber mounted where it meets the turbo. Dunno who decided canting the engine over backwards and then hiding teh turbo under the master cylinder was a good idea, Sven needs his arse kicked. There has already been blood lost and a ratchet launched across the workshop!

Car's now in bit's and it's started to rain... sense of humour bypass en route shortly.

Regards

[Turbodave]

Actually ignore that, I'm talking ££££££££... to increase boost I'd need to lengthen the actuator arm slightly as shortening it will reduce how much the wastegate opens. I'll adjust it so it slips over the rod without any need to haul the actuator out and take it from there. See if I can regain some of the boost that seems to have escaped. I don't really want to go faster, I just want it to run at factory levels.... car just seems slow compared to my Cavalier (he says, ducking to avoid the incoming fire for that one)

AA is 0800 838 1122 right?

[timbo_1975]

Shorten the rod to increase pre-load. There is a figure at which to set it - 3psi OTOH - the rest is achieved by the ECU modulating the BCS.

Find and seal your boost leak first though.

Tim.

[Turbodave]

We've been fiddling about with this all afternoon to little avail.

As an experiment I increased the length of the actuator rod so in effect there was no pre-load on the actuator and gave it a try. When stationary and revved, there was a increased "dump" or "flutter" if you like and on a run under boost in the higher gears the turbo whislte was increased and the dump/blow off valve seemed more pronounced.

I then adjusted the rod again to give more preload and tried again, less noticeable turbo whistle (which I understand) but what got me was the boost gauge read the same in both instances despite the actuator being adjusted both longer and shorter than the original position. So, went and did some googling and as far as I'm lead to believe... these things will self regulate the boost? So even winding in the rod, the car/ecu/whatever will compensate for this and maintain a pre-determined PSi?

I'm used to barn door engineering where winding in the actuator would increase the boost levels untill the ECU saw a boost pressure outwith it's factory limit and then shut itself down. To get round this, remap the ECU and wind the actuator up. But again, I'm not looking to increase over factory... just want back what's escaped and given the gauges reluctance to move, I assume it's lost something.

Shoudl have bought a BMX

[BruceT]

If you wind the acuator in, it should allow slightly more boost for a few seconds, untill the ECU see it and knock it back to factory.

Linky:
http://au.geocities.com/ozbrick850/e...eithspage.html

So now you have a “tweaked” turbocharger – what are the advantages and disadvantages?

The “base line” boost of the turbocharger has been increased to 6 psi – meaning that the impeller blades are allowed to “idle” faster than before on part throttle opening. This means that boost is available sooner when the throttle is opened wide - hence it has the effect of reducing turbo “lag”. However, as the baseline boost is now higher and the turbocharger can build boost much more quickly than before, it can also spike more easily before the ECU has time to make corrections.

So the delay introduced by leaving the ECU in line means that it is now much easier for a boost “spike” to exceed safe parameters and the ECU may react by cutting off the fuel to the engine. Secondly, the ECU is still measuring the output of the Mass Air Flow sensor. It will react to the higher volume of air entering the engine by reducing the boost pressure via the wastegate solenoid valve. The onset of “knock” will cause the ECU to retard the ignition and also to back off the boost level. Luckily it does take a finite time to do so - therefore there is an increase in boost but only for a short time, until the ECU returns it to what it considers to be “normal”. [This isn’t as bad as it sounds – carefully study this extract from one review on the T5R.

“The R's engine management system has been programmed to allow the turbocharger to kick boost from 9.6 psi to 10.9 psi in 7-second bursts during maximum acceleration. This ups the horsepower rating to 240”.

[irf]

personally i think it could be one of three things or all three

1. boost leak(most likely and common as muck)

2. turbo on it's way out

3. knackered cat

[Turbodave]

Righty ho... well, went back and had yet another attempt. I shortened the actuator back to how it was before I decided to go poking, then added another couple of turns so in effect increasing the pre-load. I figure with the wastegate fully shut, I need to pull the actuator about 4mm forward to locate the pin (if that makes sense) Went for a run and to be fair, it's alot better. I would say it does reach slightly higher up the gauge and does seem to pull a tad harder before settling down. So all in all, I'm happy with that.

Regarding what could be wrong... I doubt it's the turbo as it doesn't smoke at idle or under boost, there are no oil leaks nor is it burning oil through the exhaust and I checked for play in the wastegate bearings with it disconnected and they had no play. The catalyst, again I dooubt it as the car was only MOT'd on Friday and passed emissions with flying colours (I was surprised to say the least) and to make sure, I checked the cat and it appears reasonably new (as does the whole exhaust)

So... yes, boost leaks. I still maintain it does sound very noisey under boost. What I can't decide is if they just are fair intrusive turbo's or if it's boost leaking. Id does sound like a leak, it's not really a whistle... more a whooshing noise followed by a destinct flutter when you come of the power. Again, I'm not familiar with the blow off setup on these nor how intrusive they are, but under held boost it does sound a bit airy.

So, with the actuator sorted... any ideas on where to go looking for boost leaks or how to fault find? I have visually checked as much as possible and even witht he car ont he ramp and suspended and doing 4th gear foot to floor sessions, it's not obvious where the whoooshy noise is coming from. Suggestions?

Here endeth War and Peace for the time being!

[PNuT]

if its fluttering your recuirc valve is not working..... check the pipework too it....

[Turbodave]

Ironically, today it's all but stopped being intrusive. We have a road here btween two high walls, up a hill which is great for doing window down echo spec diagnostics with a keen ear... and today it was fine, still can here it boosting away but now it just has a wee sook noise when you change gear, much like a something opening... like a bottle of coke. Still drives fine, pulls fine and reads fine on the gauge. Truth be told, I'm reluctant to start poking around too much now!

I'll have a wee check of the pipework but can the recirculating valve split and leak boost? Assume it's just in essence a rubber sealed vacuum controlled valve so if it wasn't sealing during boost it'd leak and make a noise. Blanking it off would seem like the better option but really don't want to put an atmospheric valve in it's place but if it solves the potential issues then so be it... process of elimination as usual!