Turbo system components

sawood12 · Jan 21, 2005

Can any turbo-heads out there can help me or point me to a good workshop manual that can. I'm still trying to get familiar with all the various components of the turbo system and what they do. So far i've sussed out:-

Recurculating valve (or dump valve)
Wastegate
Turbo (of course)
Intercooler

However i'm still a bit confused about the operation of the banjo bolt. Does this connect to the top of the wastegate and provide the signal to the wastegate diaphram?

Also i've seen reference to something called the 'cylclic valve' in relation to the wastegate. What is this (assuming it's different to the recurculating valve) and what's it's purpose?

I've just picked up a new dual port wastegate and am looking to see if I can fit it myself and am trying to decode the instructions.

Cheers.

sawood12 · Jan 21, 2005

Thanks. I got a Lindsay Racing DPW and an Evolution recyling valve during a recent visit to the states. I am intending to upgrade fuel press reg and chips once funds allow. Hopefully I should be OK in running the DPW in the meantime.

I find that the instructions that came with the DPW are not very well written and my unfamiliarity with all the components and their locations isn't helping. I'm not a stranger to a toolbox and working on cars but am reluctant to take on a job that I havn't fully recearched in advance.

From what I can gather so far the pipe from the banjo bolt attaches to the top of the original SPW and is refitted to the top of the DPW. The 2nd input to the DPW comes from the variable boost controller. So on the face of it fitment of the DPW looks pretty straight forward.

However the description of how to bypass the cycling valve has me stumped. Help with further instructions would be much appreciated.

Cheers.

John Sims · Jan 21, 2005

Can any turbo-heads out there can help me or point me to a good workshop manual that can. I'm still trying to get familiar with all the various components of the turbo system and what they do.

Hi Sawood12,

Regretably there aren't realy any good manuals - the Haynes book is a joke. There are a number of good on line resources including Clarkes Garage and Dave Sims site which may be of assistance.

Try the links from Here

To try to answer part of your question:-

The banjo bolt does connect to the waste gate but, on the 944 Turbo, goes via the cycling valve. The cylcling valve is controlled by the engine management system and will interupt the signal to the waste gate if boost exceeds its pre-set limit. This is the overboost protection that Andrew speaks of.

eastendr · Jan 21, 2005

Workshop and parts manuals HERE

Diver944 · Jan 21, 2005

With proper instructions it's relatively easy, and most of us here have replaced our own wastegates with few problems. It's a very good idea to completely soak the existing bolts in WD40 or PLus Gas for a number of days before the change as they can be quite stubborn. The lindsay website has a pretty good pictorial guide and I do suggest you make sure you have a few 'wobble' bar extensions to easily get to the upper bolts.

Andrew, if Scott was looking to wait a short while before getting your 1.2 chips, could he not just set the boost to factory level (0.8bar) and then turn it up when he's ready for the rest. I'm guessing he'd still get much less lag, but would not tip over the 0.8 bar overboost?

Scott you really need an accurate aftermarket boost gauge when starting to tinker as the dash gauge just isn't accurate enough IMHO

John Sims · Jan 22, 2005

if Scott was looking to wait a short while before getting your 1.2 chips, could he not just set the boost to factory level (0.8bar) and then turn it up when he's ready for the rest. I'm guessing he'd still get much less lag, but would not tip over the 0.8 bar overboost?

I'd go along with that. Many of us ran Boost Enhancers and Reliaboosts, to help our tired waste gates, still on standard chips. A correctly set DPW should be the same as a single port wastegate - but better.

Guest · Jan 23, 2005

The main thing is to make sure you don't end up running weak at high revs.
I used to be up against the same problem (running 3 Bar FPR) due to standard chips and injectors & DPW. I have now done quite a few more mods including fitment of a wideband 02 as well as larger injectors test pipe MAF etc etc. So have more than enough monitoring.
As a result I have my old Lindsey Racing AFR & Injector duty monitor surplus to requirements. If you are interested you can have it for £40.00. Its still like new only a couple of months use. For more info check out Lindsey Racing

Cheers
Tom

sawood12 · Feb 2, 2005

Well i've finally got the Dual Port Wastegate fitted. And WOW. It is fan-blooming-tastic. It really does feel like a new car. I'm currently running it on it's lowest setting till I get used to it, which works out at about 1.6 bar absolute, but even at this pressure the car just feels so much more spritley and egar. I still get a step change in accellaration as the boost get above about 1.2 bar but the difference is that there is power whenever you hit the accelarator and it builds to max boost very quickly - almost instantaneously. It's especialy noticable on the motorway. At 70mph in 5th you can hit the throttle and you intantly get max boost and good strong accelaration and before you know it you would be in automatic ban territory (of course i've never tried this).

I'm still running std fuel pressure regulator and ECU chips and so far have not detected any problems.

Part of the big difference i'm noticing is probably because my original wastegate's housing was cracked almost all the way around it's circumference (from flange to flange) along the line of a valley of one of the cooling fins. You could see daylight though this huge crack - i'm surprised I managed to get & hold any boost at all. Looks like I wont be getting my $300 exchange charge back then!

I think i'll be leaving it on 1.6 max boost pressure for a while until I train my right foot that it no longer has to floor the throttle and then try to second guess when the boost is going to come in. I'm sure with my cracked wastegate housing my turbo lag must have been much greater than it should've been.

Typical though - as soon as I sort one thing out i've developed a leak in my high pressure side which is giving me irratic revs at idle. I can hear the sucking but can't locate the leak. I've gone round all the jubilee clips with a screwdriver but it's still sucking. It's probaly a minute split in one of the hoses.

Thanks all for the advice it was, as always, spot on, although the WD40 bath didn't help the bolts at all which is why I eventually got my local Porsche Specialist to fit the unit - and even he couldn't get it off without shearing all but one of the bolts. Whatever happened to Copperslip?

tommo951 - thanks for the offer but think i'll decline. It's going to take me some time to work my way back upto standard 1.8 bar boost pressure let alone tweaking it for more!

Cheers all.

John Sims · Feb 3, 2005

Looks like I wont be getting my $300 exchange charge back then!

I've got a nonbroken one sitting in a box in my shed and will split the $300 with you if you are interested.

sawood12 · Feb 3, 2005

That's a very generous offer John, but by the time you factor in the poor US$ to £ exhange rate and cost of shipping item to the US (about £40) I reckon we're looking at clawing back a measily £63 each. Even though that would go a small way towards recouping my losses I'm sure you could shift your wastegate on ebay for more than that.

I'm still waiting to hear from Lindsay Motorsport if they will accept mine back with the crack but I suspect they wont since I can't see it being possible or economic to repair the housing. Don't feel too sorry for me though because even with the core charge i've still saved money compared with the cost of the item in the UK excluding the core charge. Lucky I had a business trip to the States which allowed me to skirt the shipping costs.

Cheers.

Fen · Feb 3, 2005

I'm glad it's made a difference to you, but as I've said before there are lots of these wastegates cracking nowadays which does make me question the wisdom of using them as cores at all, especially when there are alternative wategates built entirely of new parts available for similar to even the exchange price.

Guest · Feb 3, 2005

Scott,
Just checking how you are measuring your 1.8 bar boost as that is quite a lot of boost to be running with stock FPR and injectors. Remember 1 Bar on the stock gauge is atmospheric pressure so 1.8 bar on the stcok gauge is in fact 0.8 Bar or about 12lb boost.
If you haven't already get yourself a standalone boost gauge, you will find they are only about £30-35 on ebay and you will have a better idea of what boost you actualy have. Never trust the stock gauge, I am sure everybody on here will back me up on this one!!

Cheers
Tom

sawood12 · Feb 3, 2005

Tommo,
What I meant to say is 1.8 bar absolute pressure not boost pressure - i.e. 0.8 bar boost pressure. I believe this is stock boost pressure.

At the moment i'm using my standard guage as reference only. I'm not currently intending to run higher than stock boost and i'm sure when my guage is saying 1.8bar I could be getting more or less. With my stock wastegate I was getting 1.8 on the guage now i'm getting 1.6 and it is noticably less boost so i'm confident i'm currently running within limits. Once I get used to the new wastegate and cashflow allows and I start 'playing' I will invest in a better boost guage.

Interesting about the cracked housings. I spoke to Lindsay racing and they sounded quite surprised when I told them as if it's not a common thing. Oh well, i'll keep an eye on it and see how it goes.
Cheers.

Diver944 · Feb 4, 2005

I think the stock gauge is pretty accurate when it comes to measuring the boost presure but its 'reaction time' is a bit slow. What I mean is if you are making 0.8 bar boost it will read 0.8 but as you start to lose boost at the upper rev range it is slower to react. An aftermarket mechanical gauge quickly shows that you are in fact reading 0.6 where the dash is still at 0.8

The other thing is it maxes out at 1.0 bar and the markings between 0.8 and 1.0 bar are very close together so you could easily overboost and your gauge would still be pegged at 1.0, this is obviously more of a problem if you are raising the boost pressure. Scott is right to be conservative, but you do have the added safety of overboost cutout with your standard chips. They won't let you raise boost over 0.8 bar for more than a few seconds