Bonnet Scoop - Air Vents for Cooling

[grump]

I am in the industry that can manufacture these auto exec type intakes, I would be keen to make one for myself, after looking at my NA this afternoon it would be very acheivable, but there may be a bit of trimming involved. I can make them with a finish layer of carbon if required. also I would be prepared to look at the same for an NB if it needs to be different to the NA. The more hands in the air the cheaper it would work out. let me know how much interest there is and I will do my homework on price e.t.c.

[Rotary]

What it all means is that no matter what heat you pick up from components under the bonnet, you will counteract this to a smaller degree at idle and to a larger degree whilst moving forward - more speed = lower induction temperatures => lower induction temps = denser air which equals higher efficiency.
Then add : more speed = higher air pressure, which equates to less induction restriction, again providing higher efficiency ...... your motor is not trying to suck air through a straw.

Don't get me wrong on this, I'm not trying to get blood out of a stone, if you want sheer horsepower and lots of it then of course you have to do the big mods with the big spend - what I'm trying to achieve is efficiency which I hope will equate to lower fuel consumption and increased responsiveness ..... I'll get back to you when I get it all finished, but don't hold your breath, it's gonna take some time

Where do you estimate your greater Gains in Fuel efficiency will come from the increase in gas velocity etc. or from the lower gas Temps
and in what driving conditions do you think an improvement may come(ie. cruising at various speeds, acceleration(mild,heavy,Max) or all of the above)

I ask because I can see many factors within the affected engine systems, that will work against an improvement in fuel economy.
For max power its all good, but Engineering for fuel economy is quite different than designing for max power(although obviously some Mods will benefit both)

[randymx5]

The more hands in the air the cheaper it would work out. let me know how much interest there is and I will do my homework on price e.t.c.

Im keen, price dependant

[PUR157]

The more hands in the air the cheaper it would work out. let me know how much interest there is and I will do my homework on price e.t.c.

Definitely interested!

[MX5CHIC]

In answer to your question Rotary ..... Efficiency ..... well - if you were to test the pressure drop across the intake system, as in testing at the inlet and testing at the manifold after the Flow meter, air filter etc then you will see a considerable difference, but heres the trick - the air filter and air flow meter are not major causes of air flow restriction, in fact it is the bends in the air duct and air box that cause most restriction (turbulence); the trick is to smooth the air flow path and thus reduce restriction.
An improvement in airflow via reduction of restrictions will produce a small increase in power, the actual improvement in performance will not be measured by a Dyno, when I swapped my standard air intake from standard to a K&N system I really only noticed one thing, the car revs quicker - this makes perfect sense because a larger volume of air gets into the manifold due to the lower restriction of that airflow = this makes an engine more efficient.
Cold air, or at least lower temperature air will make the fuel burn more efficiently, hot air costs power through more retarded ignition timing and lower density so it makes perfect sense to avoid under bonnet air supply at any cost, this again is what I refer to as efficiency whether you consider it in terms of gaining power or reducing fuel consumption.
Further to your question, I think the improvements would be seen throughout the speed range but in particular to acceleration and I'd make an educated guess that colder air will aid fuel efficienecy but i'll ascertain that when I get a system set up and tested over a few tanks of gas.

[Rotary]

This is my favourite topic of discussion for most of my life(Engines- Power and funnily enough for someone who loves Rotaries, Efficiency), so enjoying the tech discussions, its got me thinking deeper and deeper, which is always good for learning and reinforcing understanding, and some great little ideas everyone is putting forward like the wetsuit and
Oven Mitts, Nothing beats Cheap working solutions and the best way to do it is by transferring technologies from other industries, so bring on the ideas.

On to the Technobable, I’ll try my best to explain a few key systems within an engine and how I understand them to apply to both power and efficiency. Also try and keep it as simple as I can for all readers

Firstly dividing the discussion into 2 key areas,
1. Increasing Induction Pressure and Velocity,
2. Effect of Lower Intake Temperatures

Quick Simple Definition of key terms:
VE (Volumetric Efficiency): The volume of Air you can get inside the Cylinder which is compared to the Cylinder Displacement to work out its efficiency (its effect on fuel efficiency is by its direct relationship to Pumping Losses)
Pumping Losses- it is the energy necessary to suck air into the cylinder, One of many losses within an engine which reduce power and efficiency, it is at its greatest loss when vacuum is greatest(Closed Throttle) and lowest loss under Full Throttle

1. Increasing Induction Pressure and Velocity
In a normal Petrol Engine, You will not get a gain in VE(Volumetric Efficiency) from Pressure and Velocity, Except when in the WOT(Wide Open Throttle) Position, The Gain in WOT will be a small gain in VE with a small lowering of Pumping Losses.
At WOT an engine is not tuned to efficiency, its tuned for Power and protection from a lean condition, which means a rich A/F Ratio (11-13:1 and much wasted fuel.) offsetting any possible hope for fuel efficiency.(unless your trying to gain efficiency on a racetrack ie mostly WOT)
The Increase in VE will give a relative increase in Engine Power.

The main reason for the above is quite simply the TB(Throttle Body)it is by far the greatest restriction, Lets say you want to accelerate and this corresponds to a certain Throttle opening. then if you force air past it, your car will go faster than you want it to so you will back of anyway, i.e. you will regulate throttle to your desired speed and acceleration.
So the Net effect will be the exact same VE within the cylinder in all but WOT situations.


2. Effect of Lower Intake Temperatures
Now this is a more complex discussion with for and against. So I’ll keep to the most significant factors most relating to efficiency

The first and most important is the efficiency of combustion within the cylinder, this is determined by the rate of FFP(Flame Front Propagation)
For this discussion I’ll keep it a simple as possible and won’t go into all the elements of FFP and how its rate varies, as there are many factors involved,
And try to give a brief insight into what’s important and how temperature affects it

So in simple terms, FFP must hit the piston at a precise crank angle after TDC(top dead Centre) which is ideal for maximum transfer, and continue to transfer energy to the piston quickly, before the piston gains to much velocity otherwise efficiency will drop.
But most importantly, it works best when the combustion and hence FFP speed, occur quickly so more of the energy is utilised.
Higher Temperatures lead to a higher rate of combustion and so aids in efficiency, unless it is so high that the FFP hits the piston too early which leads to pinging (in practice this doesn’t occur in our engines even with the higher temps and pressure from mildly boosted turbo applications)(so not a factor and ignition will not be retarded easily)

The second important factor is again related to pumping losses and how a denser charge will increase this in all situations except the WOT case. This is similar to the throttle Body case in part 1, with one very important distinction, this time the VE will be lower for the required power(except full) as the denser charge will yield more power for any given Volume, and therefore require less VE. As VE is related to Pumping losses, then they will be larger for all but the Wide open Throttle
(Note: The A/F mixtures will always remain relatively constant as the ECU will compensate for the colder denser air, with the appropriate extra fuel)

The one area you could theoretically offset some of the losses of FFP is by advancing the ignition timing, but this idea is let down by the ECU of our engine and the fact it won’t compensate for this, so without going into to much detail on the ECU control as it could be a few more pages (I had plans to manufacture them). I’ll say that you must manually adjust it as I have done 18deg BTDC, and the newest engines, are a bit smarter, but so too are the designs of their CAI’s

I have also read some time ago now, in some SAE(Society of Automotive Engineers) Papers, that motor vehicles will waste less fuel, when the temperature increase. Something that surprised me and I couldn’t make sense of at the time, but understand it better now

So I hope this explains some of the important factors, and like to hear more opinions on this or related. And if I haven’t explained something clearly please let me know (English was always one of my weaker subjects)

[randymx5]

Nothing beats Cheap working solutions and the best way to do it is by transferring technologies from other industries, so bring on the ideas.

Cheap would be me making some dry ice just before i leave work each night and placing it around my airbox or intake some how. Colder still, maybe i could use some liquid nitrogen (however thats prob a little too cold)..

[MX5CHIC]

Getting so deep and meaningful Rotary .....

Everything you say does make sense, all my experience with engine tuning and modification was with 2 and 4 Stroke motorcycles and to some degree with pre ECU cars like my old Alfa Romeo.
Theory VS Actual - I have read about Negative Pressure Supercharging recently, part of the idea is to utilise Hot Air Induction, the system makes some amazing claims on engine performance and fuel economy - here is the link - http://www.impulsengine.com/how/induction.shtml
If you search the internet as we all do, most engine performance ideas work on lowering the intake temps and lowering the intake restriction so we would assume there must be some science behind these concepts.

You mention intake velocity and the Throttle Body having the largest restriction - now as per my previous post, if you measured pressure drop from the throttle body to the intake tube (air entry point to the airbox) you will see a noticeable pressure differential - therefore if you imagine .. the throttle body is "asking" for more air than it can receive ; because that pressure drop occurs before the throttle body, the intake manifold / throttle would take in air at a greater velocity if it were not for the restriction of airflow before it.
In a perfect world you would have the throttle body open to the atmosphere with nothing in front, this would then cause it to be the only, and greatest restriction.
Removing all airflow restriction before the throttle / carburetter would define a maximum available inlet pressure at that point, hence my "theory" that shortening the intake path (aftermarket intakes) and smoothing the available airflow to avoid turbulence will assist engine breathing by permitting air to get to the throttle body faster than it could with restrictions as proven by measurable pressure drop, of course the point of my post was to reduce some of this pressure drop by introducing a forced air intake.
My own experience as stated earlier is that the car "revs" quicker - I certainly cannot state that I therefore gain better fuel economy or increased horspepower and you are correct on that point as with the lower intake temperatures - seat of the pants testing needs to be done on that yet.
BTW - did you enjoy debating at school ? It's very interesting so don't stop yet ..

What I'd love to know from users on this forum is their individual experience's from Air Intake Modifications.

[Benny]

I've got some wet-suit material in the factory if anyone wants to buy some.
It's not cheap material however.
A square foot of it costs me around $3.50, so if you would like some, let me know how big a piece you'd like.
It'll be chaeper from me than buying a few stubby holders to cut up!

[Rotary]

my experience with engine tuning and modification was with 2 and 4 Stroke motorcycles and to some degree with pre ECU cars like my old Alfa Romeo.

You can help me tune my RGV then

I don’t know too many people that like cars the way I do (except on this forum), and Have found them all to be a very knowledgeable bunch, making enjoyable reading even if I don’t always contribute.
And I often wish I knew more experienced people I could discuss my ideas with, such as your knowledge of cooling systems, I have been working on ideas in regards to designing the most efficient liquid to Air intercoolers for my supercharger I plan to install, I say liquid because I have been toying with the idea of liquids other than water, in particular Liquid metals (Favourable heat transfer ratio to weight which could imprtantly also allow for better flow within the manifold if less material used) , and also multiple systems maybe even including heat pipes as often used in the IT industry. This is a related but slightly different topic but I can imagine you have seen some extraordinary systems, and be able to transfer a suitable technology.

Back to the Topic, when you say rev quicker the only way this will occur without changing Rotational masses, gearing or vehicle weight is by the engine producing more power due to the greater VE or denser mixture, which in turn creates a larger BMEP(Brake Mean Effective Pressure) and ultimately more power. As I have said in my previous discussion this will all happen at Wide Open Throttle, and it is possible that the engine will be more efficient at WOT(but only WOT) than it previously was, but probably not by much if any because that denser charge means ECU will give more fuel than previous,
I was going to mention Carburettors, but thought it unnecessary for our application, but in a Carby setup a very different set of circumstances will occur with the carby’s inability to meter extra fuel for the cooler mixture.

I totally Agree with what you say about just seat of the pants feeling it, (hardly scientific ) So i never trust my own judgement and use the Gtech Dyno

Benny I may take you up on that offer, what sort of sheets do they come as, so I can know how much I will need for my 3inch diameter Piping
Cheers Matt.

[Hellmun]

What I'd love to know from users on this forum is their individual experience's from Air Intake Modifications.

Well my car was standard when I got it, then I put a K&N pod filter on a PVC elbow. This made the throttle response twitchy but it did feel like the car gained top-end but lost mid-range. Then I got a longer intake pipe and place the intake on the exhaust side in a heatshield. This seemed to have the same top-end but I got my torque back in the midrange too. Then I enclosed the box and rigged up a pipe to the foglight. This was the final and best design, car feels torquey at mid range, great at top-end and I've noticed I can reach a redline JUST in 4th gear on the back-straight of wakefield. I also need to back off the throttle to turn into turn 1 at Eastern creek. I've got pictures of all 3 setups.

I've made it based on the CAI I made for my daily driver. I have an all aluminum enclosed box with a cold air ramp to under the bumper in a camira. In that car I measured a drop on the same day (30 minutes later) from 56C to 23C from a temperature probe sealed in an unused vacuum line. The cold-air ramp (literally a rectangular piece of guttering bent sitting just below the bumper) started working at low as 35kmph. The heatsoak was terrible in the standard system, it pulled half the air from around the radiator. I have pictures of all the setups (on the camira and mx5) that I could post.

I've found the colder the air I've gotten to the intake, the sharper the throttle response. The longer intake doesn't seem to have any negatives though other than price.

[grump]

well I installed a mania cold air intake yesterday arvo, the whole job took 2 hours, it included removing and reinstalling the strut brace and making a new bracket to mount the washer bottle. very easy install. I have gained power right throughout the rev range. especially 5000 revs and over. seems to have more torque down low as well. and love the induction sound when I go over 3000 revs. probably the cheapest and easiest hp gain to be had, now all i've got to do is put a decent exhaust system on.

[93_Clubman]

I am in the industry that can manufacture these auto exec type intakes - the more hands in the air the cheaper it would work out. let me know how much interest there is and I will do my homework on price e.t.c.

Pls count me in

[MX5CHIC]

Ok, in my effort to test any and all modifications on the intake system I thought I'd let everyone know that Jaycar Electronics sell Temp and Pressure test equipment - the only trouble is that it requires some electronics skill.

High Range Adjustable Temperature Switch with LCD @ $69.95 - CAT. NO. KC5376 (measures up to 1200 Deg C) and has an LCD Readout which can be mounted on the dash.
http://jaycar.com.au/productView.asp?ID ... &SUBCATID=

Pressure Differential Sensor @ $39.95 - CAT. NO. ZD1904 Will measure the pressure drop across your air filter and supply piping.
http://jaycar.com.au/productView.asp?ID ... &SUBCATID=

[Fatty]

Pressure Differential Sensor @ $39.95 - CAT. NO. ZD1904 Will measure the pressure drop across your air filter and supply piping.
http://jaycar.com.au/productView.asp?ID ... &SUBCATID=[/quote]

i LOVE the jaycar stuff (got a few of their kits on my car)... but yeah they are all "kits" ... i guess i prefer to be spoonfed.. if you install this can you give us a step by step tutorial on the install? ?