Turbo Chatter I think

[Rob P]

OK so I've been tinkering with the car again, well that's what it's for isn't it
This time I decided to see what it would be like without all the Trash can filter and pipework and stick a K&N type filter under the bonnet. Work completed and car runs OK except that It now sounds like an Audi Quattro. Instead of the previous massive dump of air on gear change I get this nice little chatter which sounds good but having read a few articles on the subject I suspect isn't going to do the Turbo any good.

As everyone probably knows this is Paul Watkins old car and yes it is somewhat modified but hey we all love a challenge don't we. Pictures provided to help hopefully. First one shows the filter in place and engine bay with Dump valve etc. Looking at the pipe work drawing in the manuals I have printed off hasn't really helped too much as there are different elements to the Turbo system on this car (Different Boost Gauge, parts not plumbed in as no longer needed as per a previous post) and a solenoid which has two pieces of pipework connected to the Turbo, one to the waste gate capsule the other low down to the Turbo body itself.
The Samco hose from the filter to the Turbo has a smaller hose from it which goes to the back of the OIl seperator, there is also another pipe from the Samco hose which is blocked off and goes nowhere.

IMG_2296.JPG

The next picture shows the Dump Valve, there is a pipe which goes from the bottom of this to the intake Plenum and one from the top which goes out the bottom of the engine bay to nowhere (again) but is open to the elements

IMG_2295.JPG

Question is, having put the new Filter in place have I upset the balance of air going into the Turbo compared with what the overall system can handle. is it a case of adjusting the Dump Valve (Assuming this is possible) to balance the pressure differential between the air intake and the intercooling piping which may well have been affected by the change in air flow on the Turbo side or have I missed the point completely here.
Always willing to learn but reading the notes and the info downloaded thus far has left me a little confused. I haven't tried putting the old trash can arrangement back on yet but that might be an option if you gurus can't guide me in the error of my ways as I really want to make this set up work ok. Looks so much cooler than the trash can IMO.
as always guys I welcome all feedback, even the odd mickey take.

[simonbuk]

I'm not going to be of too much help here but I've recently bought one with KnN filter already fitted, no dump valve, just exhaust. I recently posted how I was surprised how violent the sound was, surprised Lotus would have had it like this. Can't believe just the filter has made it like this but maybe so ?

Some said no need for the filter as it has enough air anyway but it came with it so it's staying on.

[Rob P]

Thanks Simon, yeah I was surprised when I took the car out with just the filter changed and the whole sound changed. The car still pulls well and the turbo boosts OK just the sound and the loss of the single dump of air is a bit of a worry. Although the sound of the chatter is a little hypnotic when I manage to stop worrying about what it might be doing to the Turbo

[Elanlover]

The only concern I would have about the filter setup is that its drawing hot air from the engine bay. I installed a pipercross filter which like a K&N filter but sealed. The intake plumbing is connected to the existing piping that runs prior to the old airbox so I can suck cooler air from the wheel well. It does make a difference. Maybe 100 degrees worth of difference.

[simonbuk]

But then some people say once its gone through the intercooler the temperature difference is negligible ?

Honestly don't know what/if the difference is, only hard facts will ever tell us, don't know if anybody has ever measured the difference in temp before it goes into the inlet on different set ups ? Be interesting to know.

[lotusflasherman]

But then some people say once its gone through the intercooler the temperature difference is negligible ?

Honestly don't know what/if the difference is, only hard facts will ever tell us, don't know if anybody has ever measured the difference in temp before it goes into the inlet on different set ups ? Be interesting to know.

Don't know who says that but they are talking through their exhaust pipe. Basic physics tells us that cold air has a greater density and greater ability to carry petrol vapour, that's why carbs have cold airboxes and turbos pull air from cold areas and have intercoolers to remove heat that exhaust driven turbo's inevitably put into the inlet charge. K&N filter inside the engine bay sucking air pre-warmed by the engine & radiator seems the most crazy idea to me. I wonder why Lotus went to all that trouble to fit all that pipework to the filter, turbo, and intercooler if stuffing a K&N filter in the engine bay would have been adequate. If it had been an improvement we'd definitely have it as Original Equipment !

[steve matthews]

Pull off the wheel arch liner and look where that turbo hose starts. Tucked way up into the wheel well.
The only air it gets is intercooler leftovers.
At least that is what is on the FED. car.

Steve

[lotusflasherman]

Pull off the wheel arch liner and look where that turbo hose starts. Tucked way up into the wheel well.
The only air it gets is intercooler leftovers.
At least that is what is on the FED. car.

Steve

What? The intercooler is a sealed system from the turbo outlet pipe, through the intercooler, through the intercooler outlet pipe, which just happens to pass through the wheel arch, and onto the plenum chamber.
Don't know what you mean by 'intercooler leftovers'. I know where my air filter draws air from, it's nice and cool.

[steve matthews]

Yes after the filter housing it is a sealed unit. Take a look at where the supply hose to the trash can is located.

I'm still looking for a better solution especially for track days.

[lotusflasherman]

Yes after the filter housing it is a sealed unit. Take a look at where the supply hose to the trash can is located.

I'm still looking for a better solution especially for track days.

What do you think the problem is? Have you got high ambient temperature? I raced a 1000cc Mini on UK circuits with a Weber 40 DCOE and tracks were clean so never bothered with any filters. Have you thought about taking filter out?

On an overnight trip down the French motorway to Monaco I hit the rev limiter (7,200 rpm) in top gear on standard SE induction set up. Cool damp night, hood down, Eagles on the CD player doing 149 mph everything was lovely.
150.5 mph hit the rev limiter and thought I'd blown the engine or hit a plate glass wall... ignition cuts, fuel pump cuts, front tyres squeal, seat belt stops me hitting the screen and engine picks up again doing about 110mph...
Bit of a shock to the transmission and the driver and thought 'Never, ever, do that again!' Bet I couldn't have done that with a K&N filter breathing warm air from inside the engine compartment.

[Rob P]

Well that stirred up some interesting discussion, I've seen many a car on here with this set up and wonder if anyone who also has this could add to the comments, as for the pipework for the original set up I wondered what the sense was in having the outlet under the wheel arch facing the rear of the car, surely that would be restricting the chance of air passing into the filter system as the car is travelling anyway wouldn't it. I did try the trash can set up with the tubing removed from the bottom of the can so drawing air into the Trash can and filter itself before fitting the K%N type arrangement and all worked well and I assume this would have been drawing in warm air also.

Sound slike I need to do a bit of playing around until someone with a similar set up pops up to say what results they are getting

[theelanman]

Rob
I agree with the sentiment raised by several.....
cold air is what you want and the large filters don't tend to get this......taking the hotter air from on top of the engine as they do
no matter what set up you have you always notice when you get a cool air day as the car is much more eager than on a very hot air day..
Id be trying to get the air from under the car....
I changed my filter out for the K&N version but the one which fits in the existing trash can....
hope you get it sorted
cheers
G

[simonbuk]

But then some people say once its gone through the intercooler the temperature difference is negligible ?

Honestly don't know what/if the difference is, only hard facts will ever tell us, don't know if anybody has ever measured the difference in temp before it goes into the inlet on different set ups ? Be interesting to know.

Don't know who says that but they are talking through their exhaust pipe. Basic physics tells us that cold air has a greater density and greater ability to carry petrol vapour, that's why carbs have cold airboxes and turbos pull air from cold areas and have intercoolers to remove heat that exhaust driven turbo's inevitably put into the inlet charge. K&N filter inside the engine bay sucking air pre-warmed by the engine & radiator seems the most crazy idea to me. I wonder why Lotus went to all that trouble to fit all that pipework to the filter, turbo, and intercooler if stuffing a K&N filter in the engine bay would have been adequate. If it had been an improvement we'd definitely have it as Original Equipment !

No I don't mean that.

I mean that whether its taken from an air box or a cone filter, by the time its gone through the intercooler some say the difference is negligible.

As regards why Lotus didn't put one on there in the first place well you could say that about all cars really where Pipercross, KnN, ITC, etc, etc, makes aftermarket performance filters. If none of them worked and the standard airbox is always more efficient then why are these companies still in business after all these decades.

And whats the temperature inside the engine bay when the car is moving along ? Its obviously nice and hot when we lift the bonnet up bug who knows what its like when movinb alonb - anybody taken any stats - just curious ?

Just playing devils advocate here you understand !!

[lotusflasherman]

But then some people say once its gone through the intercooler the temperature difference is negligible ?

Honestly don't know what/if the difference is, only hard facts will ever tell us, don't know if anybody has ever measured the difference in temp before it goes into the inlet on different set ups ? Be interesting to know.

Don't know who says that but they are talking through their exhaust pipe. Basic physics tells us that cold air has a greater density and greater ability to carry petrol vapour, that's why carbs have cold airboxes and turbos pull air from cold areas and have intercoolers to remove heat that exhaust driven turbo's inevitably put into the inlet charge. K&N filter inside the engine bay sucking air pre-warmed by the engine & radiator seems the most crazy idea to me. I wonder why Lotus went to all that trouble to fit all that pipework to the filter, turbo, and intercooler if stuffing a K&N filter in the engine bay would have been adequate. If it had been an improvement we'd definitely have it as Original Equipment !

No I don't mean that.

I mean that whether its taken from an air box or a cone filter, by the time its gone through the intercooler some say the difference is negligible.

As regards why Lotus didn't put one on there in the first place well you could say that about all cars really where Pipercross, KnN, ITC, etc, etc, makes aftermarket performance filters. If none of them worked and the standard airbox is always more efficient then why are these companies still in business after all these decades.

And whats the temperature inside the engine bay when the car is moving along ? Its obviously nice and hot when we lift the bonnet up bug who knows what its like when movinb alonb - anybody taken any stats - just curious ?

Just playing devils advocate here you understand !!

Ah, I see ... the argument is 'the intercooler will get it back down to the outside ambient temperature even if warmer air is pulled from the engine compartment'... probably a good argument for the UK but depends how much cooling the intercooler can do in higher ambient temperatures, when every little helps..

As you said earlier, measurement of temperatures would be interesting. I've got some of these that at the moment are telling me my thermostat is not closing ... www.ebay.co.uk/itm/Mini-LCD-Digital-Thermometer-Temperature-Sensor-Probe-for-Fish-Aquarium-Reptiles-/252259601892 Might help you do some research...

I'm not saying Lotus got everything right - compromises for production cost, suitability for all markets etc, and the development of other components since it was designed makes it tempting to tinker.
I've always fitted a Bailey Recirculating Dump Valve to my Elans, and I use the original filter 'dustbin' to feed into. Lift for braking before a corner and, rather than dumping boosted air to atmosphere and making an annoying (to me) noise, the RDV feeds 'boosted air' into the outside of the filter box so straight back down the turbo intake, through the turbo, intercooler and back towards the plenum ... and if the throttle is still closed and the RDV open it goes round again, but open the throttle, RDV shuts and back on full boost almost immediately, and I can't hear a thing!

My filter 'dustbin' contains an ITG foam filter itgairfilters.com/technology/ that I can clean and re-oil whenever I think it needs it. (Not yet needed to do it but have the kit. )

[Elanlover]

Pretty sure our tiny little intercooler is not capable of removing up to 100 degrees of heat during the few seconds the air passes through the pipes. Nor would most be able to do that. And even if it could, wouldn't you want to start with 100 degree cooler air and take it down even further in the intercooler?

[simonbuk]

as for the pipework for the original set up I wondered what the sense was in having the outlet under the wheel arch facing the rear of the car

Isn't this done as its better to have air drawn in from a low pressure area ? Sure I read it somewhere before now.........although don't know/understand why this is supposed to be an advantage.

These things always crop up on every car forum I've ever been a member of - panel filter V cone filter, air box V open filter, etc, etc, so we are not alone in our thoughts !!

I've got no real reason to drop my KnN filter, it came with the car, I have no air box or associated pipework (sounds like theres a bit extra I don't know about) to replace it with so I'm going to just use the car and have fun.

If I do compare it to another one with an air box and find its a lot more civil then I might revert the car back to normal airbox with an upgraded filter inside.

[steve matthews]

Ok, experiment time. Time to get on the Dyno.
Trash can K&N filter OEM piping dump valve.
K&N Cone filter no trash can dump valve.

I can not detect any performance differences between the Trash Can OEM and the Cone set up.
The Cone allows turbo noise to escape. May be you just hear your self going faster

Good discussion this has been bothering me for years.

Steve

[HJ2]

My 2 cents: (where to begin! )

Air temperature:
If you have a temperature under the bonnet of 40 deg. Celsius, in motion (I am not saying that it is, but I will place a temperature logger as soon as my car is drivable again and let you know) and an outside temperature of 20 deg. Celsius, then this gives a delta of 20 deg. The inter-cooler needs to cool this, additional to the temperature rise due to the compressing of the air. But the dimensions and the cooling capacity of the inter-cooler stay the same. This means that the temperature before AND after the inter-cooler will be hotter (not exactly the same delta due to losses, I know) when you take air form under the bonnet than from under the wing. You will notice this in a decrease of performance, reasons as per description above.

Turbo chatter:
This is the noise that the turbine makes when the throttle valve is suddenly closed (during shifting for instance) The pressure builds up between compressor side and intake body and this acts like a brake on the turbine vanes (I won't even start about shock-waves travelling through the system) In theory this generates an additonal axial force on the turbine shaft. On the turbo's that I took apart, I did not see wear on the axial bearings, only on the radial. I don't believe that this poses a problem for our tiny turbo. With a dump valve the excessive air that builds up when the intake valve closes ecapes (psssjjt! in stead of the air stalling tsch tsch tsch tsch ) This leaves the turbo spinning longer (as it does not brake on the air cushion) which saves time for the turbo to spin up again after a gear change. So in theory quicker on boost again at each gear change. The chatter noise on a stock system is greatly reduced due to the trashcan + piping. It dampens the sound. When you install a K&N like open air filter directly on the turbo, there is a more direct path for the sound to escape, so suddenly you hear the chatter a lot sharper. But it is still the same.
Since you suddenly have turbo chatter now: I your blow-off valve doing it's thing, or did you interupt the steering plumbing whilst tinkering around under the bonnet perhaps?? Chatter does not go together with a working blow off valve imho.

Intake position:
Under the bonnet: too hot, but a nice audible turbo chatter and it looks nice! For performance: not good. Under the wing: Nice cool air, but a bit longer path to the engine. The diameter of the intake path looks under-dimensioned. However this is not an N/A engine, we are talking forced induction here, so the air will be sucked in through the filter anyway! Also the diameter of the intake trajectory is larger then the diameter of the turbo inlet, so no restrictions here. The longer trajectory gives a bit more resistance at the longer wall of the pipes, but since the pipes are bigger then the turbo intake to begin with, it will be unnoticed imho. Also the direction of the intake with regards to the flow direction in the wheell well does not matter. A ram-intake will not push more air throught the turbo then the air being sucked in. The harmonica pipe between the trash can and turbo is not so bad either. The diameter in the can is large, so the air is slow, heavy particles will fall out the airstream before the filter is reached. Then the diameter is reduces in the hose, so higher speed towards the turbo. The harmonica profile induces a nice thick boundary layer that helps the core flow to efficiently reach the turbine blades. Nothing wrong with the design here, but yes, looks could be better There is however one improvement: Where the hose meets the turbo, there is an internal step. This segment could be improved imho

Air filter:
Lot's and lot's of info on open air filters on the interweb and here on LEC! I used one for a while (a replacement K&N filter in the OEM trashcan) but as I read more about it over the years, I ditched it and went back to the OEM filter. It filters better and is a lot cheaper. I just exchange the filter more often to keep the flow performance optimal. The longer you use it, the more obstructed it becomes. But then again: this is all in the margin and is neglect able compared to the effect of the intake temperature on performance! However stating that a filter is not necessary as the roads or tracks are clean Have a look in the stock air filter housing and you will find grains of sand and even bigger 'rocks'. You don't want this in the engine! It will eat away your turbine side of the turbo and wear or damage your engine quickly. Then there are the parts that are so small you cannot see, but will be filtered out by the filter. These will wear the engine a lot quicker than you'd like. So any filter is better than no filter obviously

If you are looking to improve the intake trajectory (performance wise, not optics), then I would opt for a bigger inter-cooler first, and not start tinkering around at the routing and / or filtering.

The usual disclaimer is applicable My above stated 2 cents are not necessary the truth!
nufft yped for now!

[lotusflasherman]

My 2 cents: (where to begin! )

Air temperature:
If you have a temperature under the bonnet of 40 deg. Celsius, in motion (I am not saying that it is, but I will place a temperature logger as soon as my car is drivable again and let you know) and an outside temperature of 20 deg. Celsius, then this gives a delta of 20 deg. The inter-cooler needs to cool this, additional to the temperature rise due to the compressing of the air. But the dimensions and the cooling capacity of the inter-cooler stay the same. This means that the temperature before AND after the inter-cooler will be hotter (not exactly the same delta due to losses, I know) when you take air form under the bonnet than from under the wing. You will notice this in a decrease of performance, reasons as per description above.

Turbo chatter:
This is the noise that the turbine makes when the throttle valve is suddenly closed (during shifting for instance) The pressure builds up between compressor side and intake body and this acts like a brake on the turbine vanes (I won't even start about shock-waves travelling through the system) In theory this generates an additonal axial force on the turbine shaft. On the turbo's that I took apart, I did not see wear on the axial bearings, only on the radial. I don't believe that this poses a problem for our tiny turbo. With a dump valve the excessive air that builds up when the intake valve closes ecapes (psssjjt! in stead of the air stalling tsch tsch tsch tsch ) This leaves the turbo spinning longer (as it does not brake on the air cushion) which saves time for the turbo to spin up again after a gear change. So in theory quicker on boost again at each gear change. The chatter noise on a stock system is greatly reduced due to the trashcan + piping. It dampens the sound. When you install a K&N like open air filter directly on the turbo, there is a more direct path for the sound to escape, so suddenly you hear the chatter a lot sharper. But it is still the same.
Since you suddenly have turbo chatter now: I your blow-off valve doing it's thing, or did you interupt the steering plumbing whilst tinkering around under the bonnet perhaps?? Chatter does not go together with a working blow off valve imho.

Intake position:
Under the bonnet: too hot, but a nice audible turbo chatter and it looks nice! For performance: not good. Under the wing: Nice cool air, but a bit longer path to the engine. The diameter of the intake path looks under-dimensioned. However this is not an N/A engine, we are talking forced induction here, so the air will be sucked in through the filter anyway! Also the diameter of the intake trajectory is larger then the diameter of the turbo inlet, so no restrictions here. The longer trajectory gives a bit more resistance at the longer wall of the pipes, but since the pipes are bigger then the turbo intake to begin with, it will be unnoticed imho. Also the direction of the intake with regards to the flow direction in the wheell well does not matter. A ram-intake will not push more air throught the turbo then the air being sucked in. The harmonica pipe between the trash can and turbo is not so bad either. The diameter in the can is large, so the air is slow, heavy particles will fall out the airstream before the filter is reached. Then the diameter is reduces in the hose, so higher speed towards the turbo. The harmonica profile induces a nice thick boundary layer that helps the core flow to efficiently reach the turbine blades. Nothing wrong with the design here, but yes, looks could be better There is however one improvement: Where the hose meets the turbo, there is an internal step. This segment could be improved imho

Air filter:
Lot's and lot's of info on open air filters on the interweb and here on LEC! I used one for a while (a replacement K&N filter in the OEM trashcan) but as I read more about it over the years, I ditched it and went back to the OEM filter. It filters better and is a lot cheaper. I just exchange the filter more often to keep the flow performance optimal. The longer you use it, the more obstructed it becomes. But then again: this is all in the margin and is neglect able compared to the effect of the intake temperature on performance! However stating that a filter is not necessary as the roads or tracks are clean Have a look in the stock air filter housing and you will find grains of sand and even bigger 'rocks'. You don't want this in the engine! It will eat away your turbine side of the turbo and wear or damage your engine quickly. Then there are the parts that are so small you cannot see, but will be filtered out by the filter. These will wear the engine a lot quicker than you'd like. So any filter is better than no filter obviously

If you are looking to improve the intake trajectory (performance wise, not optics), then I would opt for a bigger inter-cooler first, and not start tinkering around at the routing and / or filtering.

The usual disclaimer is applicable My above stated 2 cents are not necessary the truth!
nufft yped for now!

with all that.

I always thought air intake in the wheelarch was designed to face backwards so it doesn't act as a roadsweeper and bits of grit have got to be clever to turn and go backwards to get up there - but they do get in there!. Perhaps it's worse in UK because that's the wheel running in the 'kitty litter' by the verge on country roads.

Mini was fine without filter as air intake was in front of screen in high pressure area so there was a bit of 'ram feed' going on too, had a perforated zinc sheet with loads of tiny holes fixed on body and Weber carb was inside ali' box open at top. With a 5 port head the carb sat over the exhaust pipes and feeding it with cold air made a significant difference.

mini air.jpg

Suggestion was to try Elan without filter just to see if there were issues with filter restricting flow but do agree a visit to a gravel trap might have serious consequences with air intake down in the wheel arch... so accepted..

[HJ2]

Ok then:

There, it's over already!

The OEM intake is behind the liner, so no clear flow direction anyway
With the mini: I thought that the location where your intake was, is actually a low pressure area! Openings or louvres here help to get the hot air sucked out under the bonnet when driving. I just checked this: When I draw the 'mini' shape in my rudimentary wind tunnel app, i can see a low pressure recirculating zone here. The high pressure zone is a bit higher on the windscreen Perhaps that is also why usually a ram air duct is so high above the bonnet: to stay clear of the boundary layer and low pressure zone ...

It is becoming a very interesting topic !