Installation of recirculating dump vavle

[hovgaard]

Due to overwhelming popular demand (from x6gas), I'm putting up a post about installing a recirculating dump valve in my S4. This post will concentrate solely on the 'how' of the issue. As to the 'why', much has already been written in the 'back to BOVs' thread in the V8 room, and if this subject is of interest to you, I suggest you read that thread first. If you have further questions as to why, by all means post them here, but this particular post is about how. Please note that all measures are from memory only and should be double checked. Installation process is fairly simple.

WHAT YOU NEED:

A 50mm silicone rubber T:

A 60mm alloy T:

A plastic T:

Some thin vacuum hose:

Some 25mm silicone rubber hose:

A short 60mm silicone rubber hose:

And some hose clamps. This should all be available from places like Demon Tweeks. Both DT and Forge also have so-called 'dump valve fitting kits' available, perhaps you can get a bargain by buying the stuff in a bundle.

You will also need an Esprit automobile, and a dump valve. I have used the Bosch black plastic dump valve, because it is easily the cheapest available, and good enough to get the job done. Available from your nearest Saab/GM dealer. However, there are many other valves available, such as the Forge DV006, which our esteemed member Phil B has reported performs better that the Bosch variant. It also looks a lot nicer and there seems to be less risk that it could fail so as to loose parts into the compressor, but it costs several times more.

The Bosch:

One of Forge's models:

HOW IT ALL GOES TOGETHER:

I have tried to take some photos of my installation, but it is a bit cramped in the area, and they didn't turn out too well, sorry. I didn't bother to take my car apart just to show this a bit better, but I think you will get the idea anyway. Cleanliness during the installation process is of the utmost importance. Use hose clamps wherever applicable.

Remove the big black air hose that comes from the air filter, and attach the alloy T to the compressor intake using the 60mm silicone rubber hose (mine is green, but it barely shows in the photos). The smaller connection on the T pipe should point upwards, and a bit forward. Attach the big black hose from the air filter to the alloy T pipe. In my case the hose didn't need to be shortened, so reverting back to stock would be easy. Make sure the pipe is straight on the compressor intake.

The original hose from the compressor discharge to the chargecooler is removed and replaced with the silicone rubber T (mine is blue), the little connection of which should point to the right. As I recall, one has to loosen the chargecooler to do this. And, as I recall, one has to shorten the T hose to get it down to the same length as the original hose. The original hose is placed permanently on a garage shelf.

Attach base of dump valve into rubber T hose, and connect the valve discharge to the alloy T pipe with the 25mm silicone rubber hose (mine is green). I procured a piece of 25mm hose with a slight bend in it, but I think it should be easy enough to do with a straight hose.

Now fine tune your installation by rotating everything slightly till you are satisfied it all fits as snugly as it can. The rubber T hose should not be bent where the valve attaches, and there should be a bit of space between the bulkhead and the valve so they don't rub. Then tighten all the hose clamps. This could also be the stage in the process when you realise that you have to take the alloy T pipe out again and shorten it a bit to align with the valve. Carefully remove all filings from it before reinstallation.

Under your chargecooler you should find a nipple with a rubber elbow with a semi-rigid plastic tube. Remove the elbow from the engine, and instead attach a piece of vacuum hose (dead centre of last photo). At the other end of the vacuum hose, you attach the little plastic T. On the second branch of the T you attach the rubber elbow, and the third branch you connect to the dump valve using another piece of vacuum hose.

All done.

TEST DRIVE:

Get the engine up to temperature and roll down the right-hand side window. Then accelerate hard through the gears. During gearshifts, you should notice that the harsh surge noise is gone and has been replaced by a smooth and subdued sound, and that boost is more readily at hand just after the shift, improving the cars performance.

Cheers!

[x6gas]

Thanks Jens.

That makes it all really clear and I am definitely going to do this mod (shame I have only just re-fitted my chargecooler, but hey!

Cheers, Ian

[CarlC]

Jens,

Thats great. I've been wanting to do this for ages and was wondering how it would work.

Really appreciate the effort with all that.

Many thanks, Carl

[Jonathan]

Hmmmm I just bought the one from the LEW link that sits in between the chargecooler and the plenum....then I see this DIY mod and think I should have done this instead hehe

Infact I actually had 2 of those dump valves (I believe they're off the Cosworth cars too I got mine for next to nothing when I had them fitted to my Renaults). Only recently just chucked them out....DOH !

I like the way the loop is kept as small as possible which is the way I will be looping my re-circ back I think even though my BOV is higher up towards the plenum I don't want to be drilling the airbox, with this it can all be taken off with no damage.

Great write up though - only thing is that I am sure the compressor housing is fit for an 80mm pipe not 60mm ? I may be completely wrong but the flexi hose going from the airbox to the compressor is 80mm daimeter....might be an idea to check before buying just incase.

Just need to get one of those nice T pieces now.

Good Job ! B)

[CarlC]

... only thing is that I am sure the compressor housing is fit for an 80mm pipe not 60mm ?  I may be completely wrong but the flexi hose going from the airbox to the compressor is 80mm daimeter....might be an idea to check before buying just incase...

<{POST_SNAPBACK}>

The airbox to compressor air pipe reduces down from the large airbox side to the much smaller compressor intake. I had to replace mine recently and a new pipe is about

[Paul C]

I'm not tech enough to know, but the valves i've seen fitted

have been between the Chargecooler and the plenum, so i

got a couple of questions...

The Mass Air Temperature (MAT) sensor is fitted to the chargecooler

body, and is used by the ECU to measure air density and set fuel delivery.

I think?

The widely used 'T' used between the CC and Plenum is after the MAT sensor.

But this alternative position puts the Valve in the system before the MAT sensor,

Does/can the valve operating further down the system affect the MAT sensor?

Just a thought, probably nothing.

[hovgaard]

No, the sensor will still meassure the temp of the air going into the engine. Regardless of the engine being stock, have the post chargecooler BOV, or this.

[Kato]

This would be a great guide to go on LEW. Do you have a problem with it being 'stolen' and put on the site?

[Dermot]

Just some observations on the setup.

Any restriction on the air intake size is not ideal, especially if it creates turbulent flow.

My understanding is that BOV's should be as close to the throttle bodies for optimum performance.

The "dumped air" is before the chargecooler. This is very hot, at high boost levels it will be well over 100 deg C, and if it is recirculated back into the inlet air you have setup a positive feedback loop, you many get very high MAT as a result. Please watch this carefully.

On the positive side it is a neat install and will probably be a quieter location than the conventional spot between the plenum and chargecooler.

Dermot

[hovgaard]

Kato: You may hijack this if you like.

Dermot: Not to worry (well not too much). On most mass produced turbochargers for gasoline engines, there is such a valve built into the compressor housing, which means that they all end up pumping hot air round and round in the compressor while off the throttle like I do, so it's not a problem for the compressor itself. The engine doesn't see the hot air, anything that gets to the engine would pass the chargecooler first. The only problem would be that the Bosch valve may not be rated for the temperature, but so far mine looks tip top. Those who worry about that, use the Forge valve or similar. The hot air in the compressor housing is key to why this should perform a little bit better than a BOV, as hot air is less dense and thus offer less resistance for the compressor wheel. And it eliminates the risk of getting unfiltered air into the engine.

It is true that compressor intake restrictions are an evil thing, but this doesn't really offer much restriction at all as far as I can see.

[Bibs]

Paul, in answer to your question I think this may help. I hear from someone who knows about such things that...

Looking back in Lotus Esprit Turbo history a blow off valve was fitted in the plenum of all Esprit Turbos that were fitted with the separate wastegate (mounted in the exhaust wastegate adaptor). This was to protect the engine from excess boost and any subsequent damage. At that time they did not use very high boost and the pistons were of the cast type and would not tolerate long term overboosting. The blow off valve gave audible warning of continuous excessive boost (as did the boost gauge.)

When the integral wastegate turbo was introduced (at X180 & Renault Transmission start) the blow off valve was again evaluated. It was considered unnecessary as the new integral turbo wastegate system was much more durable than the previous unit (nearly 10 years had passed and turbo technology had improved considerably.)

With the following introduction of the Electronic Engine Management system and the ability to monitor boost pressure and control engine operation manual boost control was not considered necessary. The engine operation could be controlled in the event of excessive boost being detected. During the development phase of the integral wastegate which included dyno development and durability the operation of the turbo was monitored and overseen by the supplier Garrett. The final version of the turbo (there had to be changes to the rotating parts) completed the required durability on both the Dyno and on the road. The turbos showed no ill effects during

investigation after the required testing.

Items like the Dump Valves at that time were considered unreliable for a road car which had to comply with Durability & Emission requirements worldwide. There may be slight performance benefits to be gained during extreme performance requirements (Race Cars etc.) Another downside was the oil mist in the engine bay that is usual with these devices. What must be remembered is that the Esprit is a road car and the primary functions are safety, reliability and legal compliance. Without these they would not have had a viable product.

Getting to your original question of what position is better for a Dump valve could only be confirmed by back to back testing. Fitting the valve on the compressor outlet will promote high inlet air temperatures whereas fitting it after the chargecooler maintains the lowest air temp (chargecooled air) to be retained in the system. Whether these conditions could be detected while driving a vehicle with a production engine is difficult to say.

The compressor outlet installation gives a very tidy solution and if it works and gives the required benefits it should not give problems assuming the valve working parameters are adhered to. Many people have the dump valve fitted after the chargecooler and experienced reliable operation.

The benefits of Dump Valves is more evident on race spec. engines where more severe off / on throttle operations are common. For production specification road car we felt that this feature was not considered necessary so was not incorporated (remember this is going back nearly 18 years to the last serious Lotus 910 design / development changes.)

If it were to be done again today they may come up with a different opinion. Many things have changed over the last 10 years with the introduction of Turbocharged / Intercooled cars like the Subaru and Mitsubishi which use much more advanced components and technology in the engine operating systems.

[x6gas]

I managed to pick up a brand new Forge Motorsport recirculating dump valve from eBay - just waiting for the hoses to turn up so that I can fit it!

If anyone is interested there is another Forge unit on eBay at the moment http://cgi.ebay.co.uk/FORGE-MOTORSPORT-REC...1QQcmdZViewItem

Cheers, Ian

[mchlrodrigues]

When the integral wastegate turbo was introduced (at X180 & Renault Transmission start) the blow off valve was again evaluated. It was considered unnecessary as the new integral turbo wastegate system was much more durable than the previous unit (nearly 10 years had passed and turbo technology had improved considerably.)

Another downside was the oil mist in the engine bay that is usual with these devices. What must be remembered is that the Esprit is a road car and the primary functions are safety, reliability and legal compliance. Without these they would not have had a viable product.

<{POST_SNAPBACK}>

The foregoing sounds like a Lotus corporate explanation to which I'd like to add some comments.

There is no problem with separate poppet valve wastegates, reliability or otherwise. They're superior to the integral swing type in terms of flow, boost control, leakage and reliability. Porsche has always used them.

On the early Esprits, Lotus used a surplus Garrett item. It went out of production. Problems with them were due to the materials used in their construction, not necessarily the design.

When production integral wastgates became available, they were cheaper, more compact, and permitted simplified manifold castings, allowing Lotus to eliminate 2 parts. One cannot discard cost and availability considerations.

The oil mist issue is a matter of emissions legality. Inexpensive production recirculating valves were not available 15 years ago (when the MFI cars hit US shores)

The best place to locate a recirculating valve for various reasons, is on the underside of the plenum cover. Here the air vented is post charge cooler, pressure build up is relieved at the obstruction (throttle bodies) prior to the formation of a shock wave, and one has a clear shot to the inlet trunking to vent the pressure into the turbo inlet.

The disadvantage is that either welding or machining of the plenum cover will be required to install a spigot for the recirculating valve, and an adapter will have to be made to connect a discharge hose into the compressor inlet. The discharge from the valve should merge with the inlet air at an angle, as opposed to 90 degrees so as to have a mininum impact on the inlet airflow. This installation is compact, clean and logical, as other OEMs do it. It's just not the easiest nor the cheapest way to go about it.

Speaking of cheap reminds me of a Lotus story. I once asked a Lotus engineer why they did something in a certain way, when an obviously better alternative existed. "We're cheap and cheerful around here", was the reply with a chuckle.

Remember that phrase "cheap and cheerful". It may not be the official public position, but closer to the truth I've never heard.

[hovgaard]

The best place to locate a recirculating valve for various reasons, is on the underside of the plenum cover.  Here the air vented is post  charge cooler, pressure build up is relieved at the obstruction (throttle bodies) prior to the formation of a shock wave, and one has a clear shot to the inlet trunking to vent the pressure into the turbo inlet.

<{POST_SNAPBACK}>

On cars fitted with the two extra injectors at the inlet to the plenum, this would lead to condensed gasoline being dumped along with the excess air, so this solution may not be to everyone's taste. As far as I know, you don't have those injectors Michael, so this may well be a satisfactory solution for you, but for some it would be dangerous.

Speaking of cheap reminds me of a Lotus story.  I once asked a Lotus engineer why they did something in a certain way, when an obviously better alternative existed.  "We're cheap and cheerful around here", was the reply with a chuckle.

Remember that phrase "cheap and cheerful".  It may not be the official public  position, but closer to the truth I've never heard.

<{POST_SNAPBACK}>

Spot on. I asked at Garrett why the valve was omitted, considering that my 1988 Volvo is factory equipped with a Garrett turbo with a built in recirculation valve, which is known to be highly reliable, and considering that practically all other gasoline turbo cars have similar schemes. They declined to answer clearly but hinted at cost.

[Paul C]

On cars fitted with the two extra injectors at the inlet to the plenum, this would lead to condensed gasoline being dumped along with the excess air, so this solution may not be to everyone's taste. As far as I know, you don't have those injectors Michael, so this may well be a satisfactory solution for you, but for some it would be dangerous.

Good point.

[Htown]

Well, the secondaries stop firing the moment tps signal is less than 94%(not sure) or something, and that charge air is moving so fast, it's consumed by the throttle bodies before any valve can react. I've used a vent to atmosphere valve for years with lots of fuel and 1.25 bar boost, never had a hint of fuel from the valve.

fwiw-

Craig

[hovgaard]

Well, the secondaries stop firing the moment tps signal is less than 94%(not sure) or something,  and that charge air is moving so fast, it's consumed by the throttle bodies before any valve can react.  I've used a vent to atmosphere valve for years with lots of fuel and 1.25 bar boost, never had a hint of fuel from the valve.

fwiw-

Craig

<{POST_SNAPBACK}>

Just for the sake of clarity - where did you put your valve?

[mchlrodrigues]

For all practical purposes we're splitting hairs here. Turbos with integral diverter valves have been available for some time, and while in theory they recirculate "hot" air it's only for a second when the motor is not under boost. Jen's installation would work perfectly and quietly as well.

I tend to get overly caught up on the aesthetics of an installation, and because my car comes apart almost as frequently as a race car, I put a lot of effort into changes that facilitate disassembly and maintenance. The fewer hoses I have to take off and fewer parts in my way the better. That's not necessarily important for a lot of folks.

I hadn't thought about the secondary injectors at first but I agree with Craig. The secondaries will shut off before there's enough vacuum to open a diverter/BOV valve.

Please note that I was referring to the location for a diverter valve in my last post not a BOV. So if any fuel were vented it would return to the compressor inlet, keeping things safe and clean.

[Htown]

Just for the sake of clarity - where did you put your valve?

<{POST_SNAPBACK}>

Originally between the chargecooler exit flange and secondary injector plenum, now it is further downstream on the intake plenum.

Craig

[hovgaard]

Interesting. Maybe I'm wrong, but I'd have a hard time trusting it never to dump any fuel.

[patpong]

Great thread..... BOV is my next mod.

However, I have another with the normal whoooose BOV, instead of release air to atmosphere, I will direct the air going through hose to blow on to the turbo.... good, bad idea??? comment please.

[mchlrodrigues]

Great thread..... BOV is my next mod. 

However, I have another with the normal whoooose BOV, instead of release air to atmosphere, I will direct the air going through hose to blow on to the turbo.... good, bad idea??? comment please.

<{POST_SNAPBACK}>

Pat,

There's no problem with that, and it will be quieter. If you look up through the threads there's a picture of how Jens did it. I think Jens used a Bosch diverter valve which has a rubber diaphragm in them. They're OK up to 0.85 bar, but don't last very long above 1 bar (the diaphragm tears). Depending upon the boost you're running I'd suggest a Bailey's or Forged Motorsport piston type. They're more durable.

Michael

[CarlC]

Pat,

There's no problem with that, and it will be quieter.  If you look up through the threads there's a picture of how Jens did it......

Michael

<{POST_SNAPBACK}>

I've seen a picture on one of the fan sites in the US of what appear to be a very similar BOV to the type advertised on LEW which looks great - but with the vent pipe directed back into the air box to stop the noise. I take it this is safe and could be done with the LEW BOV to make it in effect re-circulating???

[ragingfool35]

I've seen a picture on one of the fan sites in the US of what appear to be a very similar BOV to the type advertised on LEW which looks great - but with the vent pipe directed back into the air box to stop the noise. I take it this is safe and could be done with the LEW BOV to make it in effect re-circulating???

<{POST_SNAPBACK}>

http://web.tampabay.rr.com/redrocket/Red%20Rocket/BOV.htm

[CarlC]

http://web.tampabay.rr.com/redrocket/Red%20Rocket/BOV.htm

<{POST_SNAPBACK}>

Thats the one!

Hi Chris,

I've sent you a PM about some mods on your car hope you dont mind as its a bit of topic.

I see now thats it different to the LEW unit I was talking about.