Air intake scoop

[dodgedavidson]

Hi all,

 

Had my 1.6K tweaked by DVA including Jenvey's and Autotechnix airbox, it looks and sounds great.

 

I was doing a bit of datalogging from the Emerald at the weekend and noticed the air inlet temp quickly gets up over 32C after a bit of a blat. It was a nice day but only about 15C. I know things get pretty hot under the bonnet anyway but the air filter intake for airbox is only a couple of inches behind the rad.

 

As air density falls with temperature that's about 6% drop in engine power 

 

My thoughts are to fit an airscoop in the nosecone directly in front of the filter to get cooler air and make a baffle to divert hot air from the rad away from the filter intake.

 

Alternative idea was to fit a hose to the airbox and position the filter low down with a scoop to draw air from below the rad.

 

Was wondering what other people have done?

 

Cheers,

Roger

 

[TomB]

Have a look at Miles Davidson pages for an idea.  

http://www.alcester-racing-sevens.com/cool_air.htm

[Superwhite R283]

Its on my list of things to do as well

[oilyhands]

Experience with the mounting position of the IAT sensor shows that conducted heat from the TB backplate can distort the reading a little, mounting the IAT near the front of the box may give a more accurate picture.

Oily

[dodgedavidson]

Thanks all, useful pointer to the alcester sevens site.

@Oily I'll have a look over the weekend and drop you a line.

[Jonathan Kay]

There's also a description of Uncle Fester's fully ducted system somewhere in the archives.

Jonathan

[dodgedavidson]

@Oily

I had a look this morning and can feel the heat from the airbox backplane. I guess the intake is well away from the backplate with 90mm trumpets and the air is not hanging around long enough to get heated up much above ambient.

Looking at the loom length, size of IAT and space under the bonnet, it might need be moved to the end of airbox ahead of the pedal box, would that work or is there a better position?

Thanks,

Roger

 

 

 

[bingham]

I've had this problem before. The sensor readings are wrong as the back plate is acting as a heat sink. I bought a male and female plug fitting used to connect the sensor and made an extension wire so i could mount the sensor wherever I liked. In the end, as I've a bonnet air scoop, I mounted it in the indicator pod underneath the headlamp so it measures ambient air temperature in still dry air. The lambda sensor reading are more consistent now.

[TomB]

That's a really interesting idea. Did it make any difference to performance? I can't remember exactly from my Emerald map, but if the sensor gets warm from heat soak, the engine will think it's running in hotter air and reduce fuelling. Is that right?

So if you place the sensor somewhere in the engine bay away from the engine block, will it make any appreciable difference? On a K series with TBs could you simply cable tie the sensor to the chassis member under the TB? That would give a better reading of the air temperature entering the manifold.

edit - found this thread of relevance 

https://www.lotus7.club/forum/techtalk/remote-location-ecu-air-temperature-sensor

[sbryer]

Hi Roger,

 

Had a similar conversion done on my 1.6 by Oily.  Also had the air intake temperature discussion so i played around and fabricated this.  Not sure how effective it is but it has got to reduce the temps.  Made from Ali purchased from Wickes, uses 3 existing fixing points and has a foam draught exclude strip between the radiator and its bottom plate.  Hope it is of some help,  Steve

[bingham]

If like me you've a 2 litre engine rev'ing at say 4000 rpm that's sucking in a lot of air - 8 cubic metres a minute. The under bonnet air hasn't got time to warm up. The air intake temp is going to be about external ambient temperature. If the air intake temperature sensor is reading anything much above ambient then it's just measuring the temperature of the bit of metal it's attached to. This was my reasoning for moving it out of the engine bay. When it was on the air filter plate it was reading 65 degrees C in winter ! Even assuming that the air temp was 10 degrees C at the time then the engine is going to assume 13% less oxygen going into it and under fuel accordingly. If using open loop this is a potential recipe for knock and broken ring lands. Anyway that was my thinking.

[Jonathan Kay]

If like me you've a 2 litre engine rev'ing at say 4000 rpm that's sucking in a lot of air - 8 cubic metres a minute.

You have a 2 L two-stroke?

:-)

But it doesn't affect the logic of the argument much.

Jonathan

[bingham]

D'oh 4 cubic metres! 

I've got a 50cc 2 stroke though. And an 8k redline in the Caterham

[dodgedavidson]

Thanks all.

I had a some time yesterday playing around with something that looks a bit like Myles and Steve's ones.

Bought some aluminum sheet from Wickes (15% off this weekend) for less than £15.

I did some sums on airflow, the airbox intake is 6.5cm diameter which is about 33 cm2. The space over the rad is about 25cm wide by 1.5-2.5cm high which is about 50cm2 so there should be sufficient air flow. I thought worst case I'm stopping the hot air from the rad getting into the intake. I could always put one of those small air scoops, that Merlin Motorsport have, on the side of the nose cone by the indicator.

I made card templates and impressed myself with my metal bashing skills, photos of the air duct are here https://1drv.ms/f/s!AlHFjo1mUgofjahc5LCqaPNk3Hi50g

I haven't decided what to do at the back around the airbox intake, didn't want to seal it up tight, engine movement, air pressure build up and all that sort of thing. To seal the slight gap between the nosecone and the air duct I could pop rivet a length of brush type draught excluder, we'll see. 

So hopefully cold intake problem solved. I shall move the ECU Air Temp sensor to the far end of the airbox to stop the heat soak and I've got a bit of ali left over to cover the existing hole in the backplate.

Cheers,

Roger

[Jonathan Kay]

Roger: how are you going to measure the effect on temperature?

Jonathan

[Superwhite R283]

I would be interested.

Tempted with keeping the IAT sensor in the trumpet/sausage filter area but trying to isolate it somehow from the heat conducted from the back plate.

Here is my current location: https://www.dropbox.com/s/2xdvu5xirej7p1s/Photo%2007-11-2015%2C%2021%2052%2019.jpg?dl=0

[dodgedavidson]

Hi Jonathan,

Good point, the two issues with the old setup which both impact engine performance

1) High temperature of the inlet air being sucked in from behind the rad.

2) High temperature reported by the IAT due to heat soak from being mounted on the Autoteknix airbox backplate.

Making the mods for (1) won't be easily measured by the IAT without moving it as it's output seems to be dominated by heat from the backplate. The effect of cooler air entering the airbox won't be evident until the engine is up to temp with hot air coming through the rad by which time the backplate will be heating up too.

So to get an reading before and after adding the new duct (it's easily removable) I'd wondered about tie wrapping the IAT to the air filter, only thing is the loom's not quite long enough. I might be able to get it close enough for a test. Will have a look this evening.

To get a reliable reading of ambient air temperature for the ECU I've had a couple thoughts on repositioning the IAT. I'm not sure how susceptible they are to dirt and dust but...

a) In Autoteknix airbox away from the backplate. There's a flat section at the far (rear) end but that means drilling the airbox to mount the IAT and if one of the nuts works loose it'll be straight down one of the trumpets :-(

b) On my new air duct. Only thing is the loom isn't quite long enough as I said and it'll be sitting in unfiltered air.

c) In the heater fan box. That gets ambient air through the bonnet louvres, it's sealed from the engine bay hot air and it'll be easy to fit as it's a plastic case. 

Ideas welcome and I'll report back on temperature findings.

Cheers,

Roger

 

 

 

[dodgedavidson]

@Superwhite R283

My IAT is in the same place.

[Jonathan Kay]

How about a separate temperature sensor for the purposes of study? That might be easier than using the same one as the ECU.

Jonathan

[dodgedavidson]

Well I've been in the garage this evening to fit my air duct. Couldn't get the IAT sensor out of the backplate with reasonable force so I erred on the side of caution and ordered a second hand one for a tenner which can be my roving IAT while I take some measurements, with and without the duct, then decide where to fit it more permanently.

Going back to the beginning of the story I found my Emerald logs with IAT readings which set me on this path.

Saturday 28th Jan - Ambient 9C (when I switched the ignition on) - after warming up @ 15:56 the IAT was showing 14C and after a bit of happy motoring 28C @16:29. 

Sunday 9th April - Ambient 19C - after warm up 25C @ 17:13 and after a bit of thrash 33C @17:30

That backplate gets pretty warm :-)

Roger

[Jonathan Kay]

Bounce

Jonathan