New shiny things

[Indi9xx]

A good example of the above was a customers car just before it was dyno tested at 342BHP at WRC.

We had just finished another batch of modifications ready for dyno testing.. from memory, the car previously had 319 BHP and had no problems with the breather system and it didnt smoke or do anything to worry about.. Then we made our modifications and took the car for the test drive.

Once warmed up, we started our full throttle, full boost, high speed runs in 3rd, 4th and 5th gear... During this test, we noticed a cloud of smoke on each gear change..

My thoughts were.. "Oh $%it... The engine is toast"... So we thought we had better hold back and get some fuel... while fueling the car my humble boost assistant opened the bonnet to investigate, to find oil all over the engine, lots of smoke and soon after a petrol station attendant shouting that the car was on fire!... More swearing followed.

Once back to base, I gathered my thoughts and ran a compression and leakdown test, which the car passed.... I was confused, until I worked out that the dump valve of gear changes at full boost was defeating the breathers..

I notified the customer, he authorised installation of a catch tank, we cleaned the engine, we installed the tank, we tested the car again, no smoke, no oil leaks and the car made 342BHP without issues.

 

[Hilux]

On a 944 turbo engine, the standard breather arangement tends to begin to fall flat on its face as you pass 330 BHP.

Excellent news I`ll leave mine alone for now []

Fascinating article regarding internal crankcase air pressures. You learn something every day.

 

[Diver944]

Thats a pretty comprehensive explanation Jon, even I understood it []

However..........its shiny, I still want one []

 

[Fen]

Thanks Jon, good explanation. If I may be so bold I do remain sceptical on one point (only); that the narrow bore breather pipe and relatively small vacuum exherted on the J-pipe end of it can make any significant difference to the pressure in a volume the size of the crankcase given that it is replenished to some degree on every power stroke (so up to 100 times per second). I'm prepared to be proved wrong, but you know me and I want to see numbers before I will be... Does anyone have any information on the vacuum pumps mentioned above to create negative crankcase pressure? I might fancy one of them. Another point of interest is that I think your explanation unintentionally encompassed one of the best descriptions of the potential problems with recirculating dump valves and hence the advantages of atmospheric ones - or course they are not suitable for cars with AFM or MAF, which then leads us into seeing differences between MAF and MAP, all from a discussion about crankcase breathing!

 

[944Turbo]

The problem with MAF/AFM and atmospheric dump valve is a rich spot when you change gear (flames!) so it wouldn't bother me too much, however my good lady wife likened them to a bus stopping and since then I struggle with the appeal.[] I am also concerned (but havent looked at them that closely), that they allow unfiltered air in at idle I know they open under vacuum so what stops the air going back the other way?
Tony

 

[Fen]

They are kept closed by a spring as I understand it, but it might be clever use of a diaphragm. Rick had to change his psring, so he can explain why (I keep meaning to ask him). My problem was getting mine to open when I wanted it to, not keeping it closed when I didn't. I totally agree on the sound; I hate it.

 

[sawood12]

Can I just clarify one or two point here because i'm reading this thread both with great interest and great fear and trepidation due to talk of turbo damage. does the whole issue of damaging turbos only apply to highly modified cars (i.e. 330bhp+)?

Are there any benefits for those of us who are not planning modifying to that extent (or at all) i.e. reduced oil in the induction system thereby reducing the effective octane of the fuel (we all know how important knock is on turbo cars), oil vapour displacing air/fuel mixture, generally a cleaner induction system with no oil collecting on all the surfaces including the turbo impellors?

Cheers.

 

[Fen]

I will allow Jon to provide the definitive answer, but my suggestion would be that it doesn't help in any situation to have oil vapour pulled through the intake system; you get it conensing and pooling in the intercooler reducing its effectiveness as well as potentially being turned to carbon deposits in high-heat locations such as the turbo hotside and the pistons/head even if the Lindsey blurb about compromising the air/fuel mixture is as tenuous as I expect it to be. Consider the increased quantity of oil vapour that makes it to the crankcase as engines wear and as boost is turned up and you will very likely have more oil hitting the intake than was originally the case for a new, standard car, so in short you have more of a bad thing as your engine wears and/or the boost is turned up. I can't really see a downside with the solution Tony has fitted compared with standard; it can only reduce the oil hitting the intake by passing it through a knock-out bottle and the check-valve sounds like a good idea, albeit that it has to be a restriction to the effectiveness of the vacuum to some degree. My atmospheric solution may be more problematic as it can cause oily smells in the cabin (if the engine is worn I guess as I don't get any with my rebuilt engine) and I think to work to its best it really needs the restrictor Porsche placed in the factory breather removed, which involves some dissasembly of the engine to get at the oil filler neck piece where the restriction sits.

 

[944Turbo]

Also that metal pipe on the 2 I have seen has been yucky inside. I have heard others talk about it too, which was what prompted me to look. It runs under the inlet manifold, the larger of the 3 and exits in a short length of rubber into the J boot just in front of the turbo. Anything coming out of there will hit the turbo, and maximum suck will coincide with maximum revs.
Tony

 

[eastendr]

Interesting and informative post, Jon. To expand on Fen's question ...

The BOV should normally be closed under vacuum (idle) conditions to prevent air being drawn in through the BOV rather than the entire inlet tract and air filter. When the turbo comes off boost, the vacuum created in the inlet manifold should cause the BOV to open to vent the excess pressure in the inlet tract that would otherwise have nowhere to go at the (closed) throttle plate end so would back up through the intercooler and eventually the turbo compressor, causing a high shock load.

Setting up the BOV to work correctly involves setting the spring pressure (or pre-load) so that at idle (20" Vacuum on WUF) the BOV remains closed, but on deceleration (24-26" Vacuum on WUF) the valve opens fully.

I ran dump to atmosphere with both the original AFM, then with the link AFM and now with a MAP installed. Theory is a wonderful thing, but in practice I experienced no problems by not recirculating with the AFM. The critical point here is that the BOV must remain closed at idle, or you will run very lean as unmetered air is drawn in via the BOV that the AFM does not see. With a MAP, this is irrelevant.

With most BOV installations, you have no manual adjustment of the pre-load and each car idles with a different vacuum level, which leads to a BOV which does not close under idle conditions so is not operating in the correct range. The good thing about the Tial 50mm BOV is that different springs are available to get the valve working in the desired vacuum range, while having an enormous capacity to dump the turbo charge as needed, particularly with a high flowing turbo / high boost.

Other BOV's available may have some manual adjustment, or the ability to take the BOV apart and preload the spring with spacers (much the same as shimming a wastegate) to get the required operational range.

If you change to a piston type BOV, be aware that you will need to clean and check it regularly to make sure it's sealing properly. In the past I've been through two Bailey piston dump valves which have leaked vacuum to an unacceptable degree (so are now in the famous BIN).

 

[eastendr]

I really MUST update my avatar ...

 

[Indi9xx]

Hi Fen,

Between the air filter (even a FandangoMotorsport one) and the turbo, when on the power or even cruising, there will be a pressure drop bellow atmospheric pressure.

I will try to take some numbers next week sometime, it will just involve hooking up a vacuum guage tee'd into the J-Pipe. Even a 1 Psi of depression will create a worthwhile gain within the crankcase.

I will try to take some numbers at idle, cruise and on boost at several rpm stages.

Its something I want to do anyway, because I want to accumulate some data of pressures at various locations around the intake system anyway... In particular I was planning on taking pre and post intercooler readings with both standard and our modified intercoolers anyway... Not just as a selling point for our modified intercoolers, but also to prove a theory I have had for a while.

I will post some data once I have it.

The catch cans are just at the tail end of development and testing at the moment and not something that we are advertising... Yet.. As we are working on final packaging and data, along with install instructions. As I believe that every product really does need to be a propper plug and play kit, as other companies advertise their products as being, yet are not.

I will post some data once I have it.

The kit will also be available as a "open loop" (atmospheric venting) version, as well as a "Closed loop" (intake venting) version.

What I will say though... I really do welcome ANY discussion, critisism, on anything we develop. The 944 community is too small to not welcome input from members of the community.

 

[Indi9xx]

Hi Rick,

Atmospheric venting blow off valves (AKA dump valves) make a fantastic sound

And with a system not measuring airflow for fuel metering, they are a great solution to dump unwanted boost when throttling off. However, for a MAF or AFM (or even CIS) system, they do of course cause overfueling.

I only stock one kind of MAF now, which is our own version for the 944 turbo (also 964 turbo and 993 turbo) which are set up just for the cars they are sold for.

I have seen nothing but trouble or inefficiency from Bailey and Forge dump valves. So I can understand why your old ones are in the bin.. the best place for them.. I would have a use for them, which would be putting them on a donkey saw to cross section cut them, and publishing photos (but not names) to explain why they are so bad and why our ones are better.

With our catch can breather kit, when used in closed loop, the check valve is there to instantly respond and close off the crankcase breather during those brief moments when the BOV is dumping... As soon as it sees more than 1 PSI difference in the wrong direction between the J-Boot and the crankcase, it closes off.. It can hold off 160+ PSI of boost trying to open it and can flow more air from the crankcase than even a blown up engine could ask for.

Talking of BOV's though, I have a mad scientist experiment that I want to try with those as well..

 

[Indi9xx]

One thing I will say...

Some catch tank setups try to sell themselves on reducing oil vapour and that oil vapour will reduce octane and cause detonation.

What I would like to say about this is that think about the octane rating of your fuel you are using... compare that with the volume of fuel that your using over say 1000 miles, how much of that 1000 miles you are on boost and running close to detonation, and how much oil you will be missing after that 1000 miles. Which should put it into perspective.

I am sure someone will be able to search the internet and find some mad scientist who has mixed engine oil with a specific RON fuel... it may be worth looking into some 2 stroke forums or mazda RX7 forums, where someone may know at which ratios of engine oil to 98RON fuel will result in XYZ effective RON.. It will reduce the ron figure for sure..

but if you work out the ratio of Oil missing from your sump after 1000 miles (most of which will be getting past the rings and burnt, not exited through the breathers), and the amount of fuel you will have burnt during that 1000 miles, you will be able to work out how much the oil will have lowered your fuel octane by (even being pedantic by saying it all had gone through the breathers)... I expect the answer would be that it will have made very little difference.

My main reason for developing the catch can, was to stop intercoolers filling with oil (they are in effect the 944T standard catch can) ... to stop all that oil having to hit a turbine spinning at 120,000 to 190,000 RPM, which causes a massive amount of shock and errosion to the compressor wheel (not to mention the damage putting the turbine out of balance).. to stop oil droplets being burnt, and to stop the pressurisation of the crankcase during throttle off conditions (bov open) which can put oil seals and gaskets under excessive strain... Not to mention the benefits of negative crankcase pressure as mentioned in my post.

If an engine is in OK condition, the standard breather system is just about adequate for the 944 turbo.. Increase boost pressure and you also increase dumping pressure seen by the j-boot as the dump valve opens... Increase intercooler flow, or turbo efficiency and again you increase the volume of intake charge and pressure seen by the j-boot on dumping.

 

[Indi9xx]

In defence of recirculating BPV's (bypass valves - closed loop - recirculating) rather than BOV's (blow off valves - open loop -atmospheric venting) is that you have a considerable amount of energy in the pressure being dumped.

With a BPV, that energy is being dumped between the air filter (restriction) and the turbo (wanting to free wheel), which in theory will help keep the turbo un-loaded, which again in accepted theory will mean that the turbo RPM once your back on the throttle will be higher.

Theory though, isnt fact... and until someone runs some back to back tests and figures out a definitive test, involving some form of turbine rpm measurement and and a infalible way of ensuring the turbo is boosted to the same level, the throttle snaps shut at the same rate, and that the boost pressure and everything else is exactly the same for back to back tests, this proof is going to be hard to get... I but I personally prefer the idea (even if its just theory) of the dumped boost energy is being diverted to somewhere it may be doing some good.

Having said that... Rick is from the world of cosworth RS500 tuning, where much more money has been spent, and much more development made, into testing BOV's versus BPV's, than will ever be spent on 944 turbo tuning experimentation.. So he may have a good argument for the BPV's (other than the damn cool sound they make)

 

[John Sims]

I don't know, I spend a couple of nights off the forum and it all gets interesting.

I am intrigued by comments that the dump valve should be closed during tick over. I became cheesed off with my Bailey dump valve staying open at idle being concerned that it was allowing the engine to suck in un filtered air.

As the Bailey dump valve is not adjustable I dismantled it and shimmed the spring to try to increase the preload. It still stayed open []. I then tried sprinkling some tissue paper fragments around the dump valve vents to find out if it were sucking in or blowing out - it was blowing out. From this I can only assume that, even at tick over, the turbo is producing more pressure in the inlet pipe than the engine needs and the dump valve is releasing this excess pressure.

The Bailey has now been replace for a Forge dual piston dump valve (which also stays open at tick over). I have an annoying on boost hiss that I was trying to get rid of. I still have a hiss but I don't have a gawooosshh on dump I now have a 90's rally car chirrup sound.[8|]

 

[Fen]

Isn't that chirrup sound compressor stall, suggesting the DV isn't working? Mine does both and that is because I can't get the BOV to open quickly enough. Maybe I need a softer spring? Interesting stuff by the way Jon. Feel free to post that sort of thing as much as you find you have time for as far as I am concerned. It's always nice to have someone who knows what he is talking about among us keen amateurs.

 

[Indi9xx]

The cool "Pit-ch-Shhhhhh" noise is the excess pressure venting to atomosphere which is normal opperation of a venting dump valve... a sound like a dove cooing is normal for a recirculating dump valve if you have an unrestricted air filter which will let the sound out.

I have also heard venting dump valves making the dove sound on gear changes.

As long as the pressure in the throttle body pipe is higher than a set amount more than the intake pressure the dump valve should open. All throttle bodys will be slightly restricted, so its quite normal to have a higher pre throttle body pressure than intake pressure, even when boosting with the throttle fully open.. this can vary from car to car and from mod to mod.. the difference in pressure that the dump valve will open, should reflect the maximum tollerable pressure differential that you should expect, plus a small margin.

Too much of a margin and the dump valve will not open enough or soon enough and the compressor will stall or begin to stall... too little of a margin and you run the risk of the dump valve being partly open when your at full boost with the throttle wide open, which will reduce your performance.

 

[Indi9xx]

I don't know, I spend a couple of nights off the forum and it all gets interesting.

Absolutely!

I really like this forum.. a few years ago it seemed to be pants with lots of people debating different waxes and which type of wine to have with antelope!

Now its good and technical.. I love it.

I quite like Rennlist.. But I would probably cause too much trouble there, because I often dissagree with some of the forum sponcers technical views and the views of some of the "Rennlist golden boys"... Also there is the American angle, which often means "What is the absolute biggest turbo housing that will fit my standard 86 944 turbo" rather than "Whats the absolute best turbo to fit to my 944 turbo and which mods should work well with it"

Then there is the problem with rennlist, which seems to mean "Pay us some cash, and we will let you spam the living daylights of of forum posts, while also stopping anyone who has something better even so much as mentioning it" which often seems to be a bit of a double standard.... Then there is the "pay us a subscription or we shall look down our noses at you" attitude.. its stopped being a community in some ways and is now a forum for chequebook tuning.

Rant over..

 

[eastendr]

ORIGINAL: Indi9xx

Having said that... Rick is from the world of cosworth RS500 tuning, where much more money has been spent, and much more development made, into testing BOV's versus BPV's, than will ever be spent on 944 turbo tuning experimentation.. So he may have a good argument for the BPV's (other than the damn cool sound they make)

Or even BOV's (not BPV's ) [] [] []

John, you're absoloutely right about the RS500's. Demands were different because the boost pressures involved were considerably higher than typically seen on a 944 Turbo (Standard RS500 was about 12PSI, mine was running 36PSI / Standard 944T runs about 11PSI, WUF currently runs 20PSI) so the shock effect on the compressor was magnitudes higher in the RS500's.

Also most research was for race applications where the frequent 24" vacuum - 36 PSI boost transition could also cause other problems when more than one race was lost when boost pipes suddenly literally blew off ...

Even standard RS500's used recirculation and the arguments at the time between BPV's and BOV's ( for road car applications) were that BOV energy was wasted, whereas BPV would vent the boosted air back in to the airbox, leading to a slightly faster repressurisation when the throttle plate opened again and the turbo began to spool up.

However, the air that was BPV'd back in to the airbox (air filter box) was already hot from turbo pressurisation ...

Hundreds of different theories in both camps (for lower boost, road specs cars) all hard to prove with data. The usual applied - people who had driven both types invariably fell in to one camp or another based on their 'sphincter dyno' as opposed to hard facts which quite regularly prove the opposite, as you say.

Another important fact was that the Cosworth engine management, although not having any knock control, was a lot better than the 944 system (in my opinion) as it was a MAP based system from the outset (no restrictive barn doors here or problems metering air before the inlet manifold) and the sensors were a lot better allowing sequential fuelling.

Another important point was that the air temp (charge air temperature sensor) was a lot better being placed in the intake manifold (as WUF now has) where it actively reads the air temp entering the cylinders and is an active signal that is used to trim the afr according to (boosted) air temperature. Compare that with the air temp sensor on the 944Turbo which is mounted within the airflow meter and read by the DME only at startup to apply an overall trim to fuel based on ambient air temp (so knows to add more fuel when it thinks you're in a cold country).

While this may be OK on a N/A car, it's not on a turbo car where the inlet air charge temperature varies over a wide range depending on outside air temp at cruise / idle or boosted air temp under boost (also effected by boost pressure / turbo efficiency / intercooler efficience etc) where the difference in temperature is vast (5 - 100C) so the fuelling need changes considerably. The air temp sensor in the 944Turbo cannot be used to protect the engine based on air temp (by retarding ignition) because it doesnt know the air temp !

Rick.