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Dump Valve

W

wizard

New member
Hi guys
I am considering changing my Dump Valve but wondering
1. just how noisy are the non recirculating type in this car plus,
2. are there any benefits other than reduced noise of the recirculating types?

A few more mods are working their way into this car as I was very disappointed at the Jamsport dyno day with power down 30BHP from standard. I still haven't found the reason for this.[8|]


 
Wiz - non recirculating are not good for our car. You will lose a bit of boost which is a bad thing if you are already down on power. Does your dump valve fail the 'suck test'? I am guessing it will if it is the original. A new one from Porsche is £40 and is now updated to have metal internals compared with our plastic original

If your car is totally stock then I would guess it's the classic wastegate spring gone really weak that is your problem. A TiAL 38mm dual port design will hold the boost where it is supposed to be and they cost approx £300 to import from USA with adaptor plates to fit our car. Keep an eye on Rennlist for an occasional Groupbuy. Mine was £250 inc vat, import and delivery (and I sold my old wastegate for £100)

Once you have a good wastegate then a simple chip kit from Andrew at Promax will get you over the 300bhp mark
 
Thanks Paul.
I am in the process of renewing the vacuum pipes and shall be ordering the dump valve from Andrew soon.
The next bit will be the wastegate - I admit I have been putting it off for a while and had suspicions it would be the root of my problem.
Is there alot of difference between the TiaL and Promax?

Jason
 
Hi Jason,

If you haven't got one already I'd strongly suggest you plumb in a proper boost gauge, even if only temporarily.

Mine cost £30, was a doddle to fit and allows you to tell exactly how much boost you're getting and if you are holding that boost at higher revs. If you're not this would back up Paul's suggestion of a weak wastegate spring.
 
Is there alot of difference between the TiaL and Promax?
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Yes..... the ProMax one doesn't fall off.

Andrew will no doubt correct me if I'm wrong but IIRC ProMAX supply the Lindsey Racing waste gate. This is a built up around a modified Porsche original. You pay a deposite in the purchase price which is refunded when you return your original waste gate. You can do this direct with Dave Lindsey in the States but Andrew has them on the shelf and you don't have all the hassel of sending your wastegate to America. I don't think there is much price difference althoug this is difficult to asses as you have £/$ conversions to take into account as well as the customs payments you will have to meet. In my experience the level of service and convenience of going to Andrew far outwieghts any small fiscal saving you might make by going direct.

The TiAL unit is a new build unit but isn't specific to Porsche so needs addaptor plates. Again, I stand to be corrected, but everyone over here who bought TiALs in the group buy had problems with the wastegate comming loose from its addaptor plates - hence my opening comment. The TiAL functions more efficiently that the Lindsey WG as the TiAL pulls the valve out of the air stream giving unrestricted flow where as the Lindsey pushes the valve below the air steam leaving the valve stem in the air flow. I don't know if this makes a difference in reality as I don't know if both units have the same bore dimensions.

Whilst I have a Tial, purchased in the group buy, I would recommend the ProMAX/Lindsey WG. I don't like conversion plates, I like things to fit, I don't like things that fall of and last, but not least, you would have to get the TiAL and adaptors from Speed Force Racing who haven't inspired me on the several occaisions I have dealt with them. The final plus, Mr Cannell uses the Lindsey WG and he knows what he is talking about.
 
Well, I think the Tial is a better design, let down by cheap gaskets and no spring washers on the adaptors. The lyndsey wastegate is neat re-engineering but I would be concerned about the valve seat. This cracks on the standard unit and you are getting a rebuilt unit that may have already covered many hours and heat cycles. They only rebuild crack free examples but how long before this is an issue? Or do they cut new seats?
Anyway a Dual port wastegate witha suitable controller is definately the way to go.
I dont think in terms of performance there is much difference between a recirc or atmospheric dump valves - but Mr Cannell did mention to me at high boost levels there can be some issues with recirculating - but IIRC this is over 20psi
Tony
 
The tial is indeed a nice pice of kit. As you say tony just the small details that let it down, this however can be easily sorted. I ended up using some exhaust paste rond both sides and on the studs, its sealed very well and i have had no trouble now for about 2000miles.

If you want my advice, keet the car standard engine wise, spend some money on the suspention and brakes and enjoy your car on the roads that its intended for.... [:D]
 
keet the car standard engine wise, spend some money on the suspention and brakes and enjoy your car on the roads that its intended for....
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A very fair comment Slim. It avoids all those problems in trying to obtain insurance. The other issue with tuning is that you never stop. Every modification either requires a further mod elsewhere or the improvements seem to deminish after a time and you go looking for more. The best way to remain happy with your engine is to leave it well alone - this tends to keep your dearly beloved happy as well.
 
Speedforeracing is not the only supplier of TiAL and adaptor plates. You can buy TiAL wastegates from many American suppliers but until recently Speedforce was the only place to make the adaptor plates. There is now a Canadian on Rennlist (userid Myswiss) who supplies the TiAL with his own adaptor plates.

Interestingly it was only us UK folk who had problems with our bolts coming loose. Mine has now done 6000 trouble free miles since I tightened them after Johns warning.

Which of us modifiers will be the first through the 350bhp barrier? Rick possibly, though I hear that Tony is installing an Electronic Boost Controller as we type [:eek:]
 
Pictures of Lindsey Racing DPW HERE

The LR DPW fits straight on without any modifications and has never given any problems. Need I say more ??

It looks like only the main casting is original (although extensively re-machined). The valve is new and the chamber is a completely new design made using CNC processes. The valve seat would have been recut and I believe that Dave Lindsey has the castings crack tested before being remachined.

For dump valves, use a recirculating type if you have the standard air flow meter. This is because the air volume is metered and dumping to atmostphere will give a very rich mixture when going back on throttle after the valve dumps (DME adds fuel to match the amount of air that has passed the AFM, but you have just kicked said air out of the dump valve to atmosphere!).

I prefer an atmospheric dump valve when using a map sensor for 2 reasons - fuelling is not affected as it is only the manifold absolute pressure that is used to calculate the fuel injector duration, and when dumping high boost there is less turbulance in the inlet tract just before the turbo (smoother air flow to compressor when going back on boost).

If you go for an atmospheric dump valve, I recommend a piston type as opposed to diaphragm as they seal better, react faster and have better airflow.

Cosworths use the same (generic Bosche) dump valve, as do others like Saab and Volvo (I believe) as the one originally fitted to the 944. The plastic diaphrams used to split over about 1 bar. My engine used to run up to 2.5 bar (36psi) so the plastic ones would have vaporised [:D][:D]

My cylinder head's done now HERE and HERE

The inlet manifold and cam tower are back from the powder coater's. The cam has gone to piper for a cleaning up, slight reprofiling to increase lift and toughening. I should be collecting these bits next weekend so stay tuned [:)][:)]

 
Ok I have seen the rich info on recirc with the barn door, but am I correct in thinking that

A) the barn door is fully open before full throttle?

B) the dump is into a tube with a compressor / IC / shut tight throttle flap on one end and a leaky closed barn door / air filter on the other

If the above 2 are correct how does the engine know how much air is in the system (when runnning above 80%ish throttle) and what tells the molecules not to sneak out past the barn door and through the air filter?

Does a load of fuel passing through the engine cool the pistons (provided its not excesive to wash the bores) and generate nice exhust flame effects?


Tony (who should be installing boost control instead of typing [;)])


I dont think I will break 350 without injectors but may be close especially now the weather is getting cooler.
 
I've got my new induction pipe fitted [:)] and now dump to atmosphere - 'cos you can with MAP.

Danno produces a MAP induction pipe which retains the recirculating dump valve but directs the dumped air towards the Turbo inlet, apparently to maintain Turbo velocity. This will also work with the conventional barn door set up as, with the dumped pressure unable to escape past the closed inlet it can only go through the turbo.

As the air passes through the turbo it is then in the inlet pipe (via the intercooler) with a closed throttle at the end and will back up again through the dump valve creating it's own little circuit and continuing to spool the turbo as it goes. Well that's how I understand it.

So, in summary, with a barn door there are several reasons why you should retain a recirculating dump valve.

Using MAP you dump into an open ended pipe so, despite the anallogy above, you could be better dumping outside of the inlet pipe and avoiding the increased turbulance - you also get a stonking gawooshhh sound when you come off boost. [;)]
 
Excellent feedback guys thanks very much. Looks as though the shopping list is as follows.

1. Pursoil vacuum tubing (ordered)
2. Recircuilating dump valve (about to order)
3. booste gauge (about to order)
4. DPW with manual boost control (will the old one come off!!) (letter to be written to santa)
5. GURU

The car has done 150K now - should I start thinking about the widefire head gasket at some stage or are there other priorities?

I think I will be satisfied for a while when this is done and turn attention to the cosmetic side of things.

Thanks again.

Jason.
 
I wouldn't bother with the Widefire gasket - they are virtually no better than standard from the pics I've seen - just a wider fire ring on one side (and I beleive it's the top which makes even less sense to me).

I'd wait until yours blows (which it will, but usually gradually) and then either get something made of metal or just stick with a new standard one.

On the wastegate I seriously wouldn't use the original housing - lots are cracking these days and just because it passes a crack test today doesn't mean it isn't stressed and about to crack in a few months time. It just seems crazy to me to reuse an old part (albeit extensively machined) when it costs no less than a brand new part. Still, you pays your money...
 
You couldn't possibly do that as that would be very Chav. [;)]

The only one I would recommend is the Forge dual piston - if you do a search you might find a thread on it some time back.

The advantage of the Dual Piston is you don't get an open vent at idle.

When dumping it goes "oggle goggle" instead of "gawoooshhh".

Not that I would know about such things.

Some may say that you shouldn't dump to atmosphere with a barn door air flow meter. IMHO it doesn't make any difference as, once the air has passed through the barn door it has been metered. If it then makes a second pass through the turbo after being dumped back into the inlet I would have thought this would introduce latency into the barn door metering.
 
ORIGINAL: John Sims

You couldn't possibly do that as that would be very Chav. [;)]

I might put a max power sticker in the back window as well
m9.gif
, i was looking at the bailey dump valve,what did you think of them,and is the forge one recurculating ??
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