Pnm engineering dump valve

[blimeyme]

Hi, looking for a decent dump valve for an S2 and there seems quite a few out there. Anyone got any views on what I should consider... Is the PNM one any good part pnm 4928k or is bailey the way to go....have also looked at tep kit which looks good but a tad pricey...unless of course it is really worth it???? Only had her since end Sept so all advice welcomed.
Cheers.

[lotusflasherman]

I wouldn't touch the PNM DV with a bargepole as I don't like 'whoosh' but prefer RDV's that exhaust silently into the air filter drum, then when I'm enjoying myself I can still hear the tyres talking to me...
but some people like 'whoosh' so the choice is yours. Recirculating Dump Valves in the UK are generally Baileys or Forge. (The PNM one looks like a Forge to me..)

Suggest you read this thread - forum.lotuselancentral.com/viewtopic.php?f=31&t=24654&sid=27e4438f7866007c1b84b6e2dafc890f#p310483

I have experience of 2 Baileys DV30's on my SE's but they seem hard to get hold of these days. If I was starting anew I'd probably be looking at Forge as a current supplier though they don't list Lotus on their applications info ...
http://www.forgemotorsport.co.uk/Valves--category--33.html

Forge offer a choice of springs which control blow off pressure but what spring to use is discussed on the thread above by those who have experience of them...

[Rambo]

Me too. I also don't like the whoosh sound of a dump valve. Reminds me of chavvy Subaru drivers. Oh, and Dico

But, as Phil correctly points out, it is a matter of personal choice. The links are also good background reading and should help you make up your mind on the best way forward

[Fredjohn]

My car had a Forge already fitted when I bought it. Hated the whoosh sound so fitted carb. foam around it to silence it. Very effective!
If I was starting from scratch I'd fit a recirculating type, probably from Forge. I did refurb mine with new seals and springs, but had to speak to them to find out which model I had. They were extremely helpful so would suggest you give them a call.

[blimeyme]

Thank you all for the replies....I will have a good look into Forge based on this.
Not a fan myself of the whooshing sound either so recirculating sounds a good option for me.
Hopefully get to meet some more fellow LEC members soon...booked onto Donington in April and Serpentine run in July so if your around I will see you there.
Cheers and Thanks again for the views/Info provided, helps massively and saves expensive mistakes. Cheers.

[Rambo]

You will always get good advice on the LEC forum. There are some extremely knowledgeable guys (and girls ) on here. Without LEC we'd probably all be worse off

A pity the main Lotus festival at Donington in March/April is no longer with us as it was a great opportunity for us all to get together, have a few beers and curry and do some serious tyre kicking in the car park. For me, and I guess the vast majority of us, it was the highlight of the year

[simonbuk]

So do they not come as standard with a dump valve ?

[maz_r]

Correct - they do not. If you have one, someone fitted it later in it's life.

[Scott]

Does Elan really needs a dump/blow off valve? I mean could we avoid it or is a must for our car's safety and longlasting?
Also which one should we get and why? DV OR RDV?

[Rice crispy]

One isn't needed but some believe it helps. I ran a DV30 for about 4 years but felt that the spring had worn so was releasing early so took it off. I can't say I've noticed any difference other than when I ran it dumping to the atmosphere for a week for a laugh going round scaring old people and children

[Steve A]

Does Elan really needs a dump/blow off valve? I mean could we avoid it or is a must for our car's safety and longlasting?
Also which one should we get and why? DV OR RDV?

Personally I wouldn't waste your time Scott, if your over 30 it just becomes embarrassing

[Scott]

So there's really not big bother about that right? I mean there are no papers or researches that say we should buy this item. I really try to understand what's going on with that and also interfering in the engine as you have to cut and add things, decreases the price and value of the car.

[rip]

There are differing opinions.

Some will say that when you close the throttle, the compressor still spins, so it is building up pressure towards a closed plate & this sends a pressure wave back to the compressor which causes increased stress & stalls it. It is therefore better to vent this extra pressure, either to the atmosphere or re-circulate it back into the air intake system. The decreased speed on the compressor reduces wear, which increases its life.
If this is a quick upshift, when you put your foot down, the compressor is still spinning so does not have to accelerate as long to get back up to speed.

The other point of view is that this excess pressure is good. It does no harm to the compressor at all & when you re-open the throttle, you have a burst of charge & the compressor will soon be up to speed.

I am not saying that either one is right or wrong.

The other issue is the 'whoosh' You do not have to plumb it back into the air intake to suppress this. A pipe with air filter will do, if the valve's design allows it.

[Scott]

So In the end, for our turbos and elans, do we prefer/use the DV? Also PNM is the only lotus engineers worldwide that provide a DV for our elans. Has anyone fitted one? If not, do you suggest a specific item?

[rip]

Opinion is split between whether they provide a benefit or not so its better for you to make your own choice.

As mentioned above, Forge do at least 1 valve.
Bailey do 2, DV30 & DV24. Once is re-circulating, the other is atmospheric. I believe the atmospheric one vents in all directions so cannot be converted to recirculating.
Greddy also do a valve but this has a flange fit. A flange has to be fitted to the pipe or welded to a metal replacement pipe. This comes with a 'trumpet' attachment if you like the whoosh sound or a recirculating attachment if you don't.

[bbjon]

Hi Scott,

The PNM dump valve your looking at is quite expensive - it's doesn't look to be anything more than a silicone t piece some vacumm hose and a generic atmospheric dump valve. You could buy the parts individually quite a lot cheaper.

With turbo cars there's always massive debate around dump valves my viewpoint would be that with a small turbo low boost application such as a standard elan they are not really necessary - then again they won't do any harm. The major difference you will notice is that with an atmos valve like the PNM one your car will be going pfffffffrrrttt every time you lift off or change gear rather than just making a chirrup when your pressing on!

If you want to bolt some kind of bin lid sized holset turbo on the front and run at 1.7 bar then you will need to fit one but at that point a dump valve will be the least of your worries!

[Scott]

Ok guys thanks for the tips. I will have to check more.