Home brew intake mods

[Johnny Mullet]

Most Metro owners do 2 intake mods for economy and a tad more power for wide open throttle situations.

Throttle bridge mod............ HERE..



Warm air intake............

[Jyden]

Christ - colder air - as you say are more dense - which means that at a given RPM you are able to administer more fulel, thus developing more hp, because the colder and more dense air contains more oxygen...

As a rule of thumb:
- For every 3,3 degrees centigrade temperature drop the air density rises 1%
- If you for instance can lower the intake temp with 40 deg C you have a 12% greater air mass. This is equvivalent of a 1,78 psi "over pressure" which in theory shold mean that you have 12% more hp availeble, but in daylilife this is more likely to be around 8%.

In our modern engines you have theese censors:
- Airmass meeter
- temp censor
- oxygen censor

The ecu recives information on air temp, oxygen level, and administer feul accordingly, thus meaning, that at a given opening of the throttle/ RPM, you can administer more fule and generate more hp.

Cold air intake is a way of finding more torque/hp.

On a standard street car you often see the exaust manifold located to the front just behind the radiator, thus throwing lot of very hot air in to the engine room. Often the airbox is located on the hottest spot in the engine romm - on top of the engine.

In such a case you will often se air intake temps in the rage from 70 - 100 deg C.

If ambient temp is for instance 25 deg. C, you can lower the intake temp by isolating the intakesystem and heatshilding it with reflctive materials.

Often this is further improved by ruting a duct from to front of the car to just before the intake "mouth" / bell opening.

This will mean that you can generate more hp at a given RPM.

Now it's up to you (and your right foot) if you want to USE them

(Changing the lenght of the intake itselves will change the RPM where max torque occur. Either up or down depending on the specific car)

What I have stated here are fact of physics - colder air => more oxygen => burn more fuel => develop more hp at a given RPM.

Now - as I said it's up to the driver how to use the extra hp. And if you only use the forst ½ centimenter travel on the accelerator, this might indeed be very difficult to administer i a good way.

But dont deny the facts.

[Jyden]

@ Christ:

Peugeot 106 Rally 1,6 8v - DOT Engineering ApS - alt om filter, luftfilter, filtrering, kn luftfilter, knfilter, sportsluftfilter, tuning, autotilbehør, scooter tuning, auto tilbehør, auto udstyr, motorcykel udstyr, motorcykel tuning, knallert tuning

This shows a Peogeot 106 with an after marked airintake. when this first was mouted, the gains wa LOWER than standard (Of which I have no graph) but when ensuring that the intake only got cold air, we got the result as seen in the graph.

At 3000 - 4000 rpm there a gain of approx 2 hp.

This mean that the car could either:
- go faster at a given RPM, OR maintain the same speed at a lower rpm, thus saving fuel.

Peugeot 106 1.4 75 HK - DOT Engineering ApS - alt om filter, luftfilter, filtrering, kn luftfilter, knfilter, sportsluftfilter, tuning, autotilbehør, scooter tuning, auto tilbehør, auto udstyr, motorcykel udstyr, motorcykel tuning, knallert tuning, m

This 2. graph from a Peugeot 106, 1.4 liter 75 hp engine shows the difference of ONLY the isolated air intake.

- Now please remove your answer

Top lines (more flat graph) are tourque - bottom hp.

As you see, theres a significant gain....

10 Newton meter at 3000 rpm's the engines peak tourque point is a very big inprovement, which on this engine would mean better drivbality, and more mpg if the driver chooses so.

[Jyden]

I would be interesting to find out exactly why the HAI works for some people.

I've seached and read about this, but so far no one has come up with a pricise explanation thats adds up with the physics.... and the ECU which in theory would compencise for the hotter air.

I accept they might work on some - but no all engines - but why?

What we are talking about here is low rpm optimisation / FE optimisation - so:

- Are you tricking the ECU to run the engine more lean?

- Less effecient engine means driving with throttle moere open - does this have an impact on things?

- I expect that every engine will have a sweet spot - hvow do we findt it?

[Daox]

I'd recommend reading this:

Autospeed - BFSC

It'll introduce you to brake specific fuel consumption. More throttle while cruising is a good thing. Its why I have been able to get 70 mpg out of my paseo.

[Jyden]

Originally Posted by Daox

I'd recommend reading this:

Autospeed - BFSC

It'll introduce you to brake specific fuel consumption. More throttle while cruising is a good thing. Its why I have been able to get 70 mpg out of my paseo.

Excelent article - thanks for that....

So to sum up what I understod from that read was:
- best mpg at peak tourqe - hence the graphs (nothing new there)
- Dosen't work on diesels as they don't have any throttle (Nothing new here)
- Pump losses / restiction in the intake path of the engine caused by the throttle valve is the main culprit here....

So - what the WAI / HAI does, in providing hotter air to the engine is actually lowering it's effency at lower rpm, so that one has to apply more throttle to achive the same speed / rpm, thus lowering the resistance in the intake system because throttle valve is now in a more open position.....

OK - if we accept that pumplosses / restriction at the throttle valve is the culprit this actually makes sence.

So what we are looking for - is trying to optimise towards is a fully open throttle valve (= lowest restriction) at low rpm's.

We are also looking for lowering the rpm number where peak tourque occurs.

In connection to the last, it should be possible to optimise the intake for best tourque at lowest possible rpms.

One way to do this is to change the lenght of the intake tube. This is the distance from the airbox the the mouth of the tube.

This is engine specific, and depends on the pulse in the intake system. Some engines might like at shorter intake tube, while others might benefit from a longer one.

Even small changes can make a difference. Also the intake tube mouth should be bell shaped to improve airflow and lessen restriction.

Usually Toyota are good at this, while for instance the Peugeot 106, 206, 306 were terrible, and could be optimised a great deal.

Lots of room for new experiments here

[Christ]

Jyden -

A few points to consider for you:

1 - You can't maintain the same speed at a lower RPM without gearing changes, making the extra power you've just generated a burden to the general operator, because who's really going to calculate and regear to make up for 2 extra HP?

2 - The engine still experiences greater pumping losses by drawing colder air due to the air's specific density.

3 - The ECM will compensate on either side of the scale, but as you note, more cold air means more fuel, while more hot air means less fuel. If your engine is capable of making more power at your cruise RPM than is necessary to maintain cruise, you're wasting efficiency as high pumping losses. To recoup those losses, you open the throttle, but under normal circumstances, that would cause you to accelerate, which is undesirable. The acceleration comes from more air/fuel being added to the cylinders. This means that in order to mitigate pumping losses without making any more power, you have to throttle the air in different ways, such as thinning it. This requires pre-heating it.

4 - At every instance in your graphs, you're showing gains of 1-2 HP in ranges that are desirable to normal driving situations. Of course, knowing how dyno setups actually work, and without evidence that multiple runs were made and averaged, I'm going to dismiss the results entirely as being within the realm of noise, but assuming for a minute that I don't, you're still making more power at the same RPM, which, in the case of adding cold air/more fuel, is neither more efficient per unit of fuel, nor is it desirable for optimum operation involving fuel per distance calculation.

To clarify - when you add cold air and more fuel, you're not doing anything the engine wasn't already doing, you're just giving it more of what it needs to make power. If you were to maximize the power output from the same amount of fuel it's already using, then you're making it more efficient at doing it's job, converting liquid fuel to heat energy, and that could translate into somewhat better FE, despite the lower throttle angles that would be necessary to maintain the same speed.

[Jyden]

@ Chris - naturally the graphs are an avarege of several runs - we did things thoroghly!

If you gain 2 hp you can travel at a given speed pressing LESS on the accelerator => save fuel.

On some cars, theres a good gain to find on FE by derestricting the intake system - on other none. It's enegine and model specific.

I for the moment don't belive theres an much extra pumploss on cold air, but theres extra arodynamic drag to overcome in cold condistions. I think, that throttle valve resistance is far greater, which appears to be why HAI work, as throttel has to be open further to produce same amount of energy to move the car at a given speed.

What we are all trying to do here is to get the max Kilowatts out of every unit of fuel. Depending on the specific engine this can be improved in several ways.

- All engines will benefit from a derestricted intake system until a certain limit.
- Some will benefit from a cold air intake
- Some will benefit from a hot air intake.

So you can't really conclude this or that. Further more what is right at one rpm, might not be so at an other rpm. So it's complicated stuff, and it would take many hours on the dyne to dertermind the best for each car, and each speed.

Everything is a compromise - what you gain in one end you usually lose in the other end. So better FE at low rpm, will mean less power and FE at higher rps, and vise versa.

I've been working with CAI and derestricting intake systemes for four years some time ago, and at the time we saw significant gains on both hp and FE.

But things has changed in the past 10 years, and car manufactors and the ECU programs has changed a lot, so now things might look different, because of changed demands on emmisions.

I'm not saying that HAI dosen't work - I'm saying that it will be different from engine to enegine what works best, as the engine, car driver etc. are different, and thus you are optimising for different situations each time.

[Christ]

Originally Posted by Jyden

@ Chris - naturally the graphs are an avarege of several runs - we did things thoroghly!

Ok, if they're an average of runs, I won't discount them.

If you gain 2 hp you can travel at a given speed pressing LESS on the accelerator => save fuel.

This is completely untrue. Using less throttle means nothing when the fuel/air input is the same. Throttle is not the determining factor in fuel use. Also, your 2HP gain was made @ WOT... lessen the throttle angle, and the HP gain will decrease in a non-linear curve. In other words, at 50% throttle, there will be less than a 1HP gain, all things equal. The average vehicle cruises at much less than 50% throttle as is. How much difference do you think it's going to make?

On some cars, theres a good gain to find on FE by derestricting the intake system - on other none. It's enegine and model specific.

The throttle plate is the largest intake restriction there is. For normal purposes, the OE filter/piping flows plenty of air for what is necessary at a given throttle angle/engine speed. At WOT, or close to it, things change slightly. You still haven't shown me a dyno graph determining a generous gain in HP or TQ for a normal throttle opening.

I for the moment don't belive theres an much extra pumploss on cold air, but theres extra arodynamic drag to overcome in cold condistions. I think, that throttle valve resistance is far greater, which appears to be why HAI work, as throttel has to be open further to produce same amount of energy to move the car at a given speed.

Once again, throttle in general means nothing. Air and fuel are the measurements of HP, throttle only controls (to a given extent) the amount of air, and more indirectly, the amount of fuel. Colder air or warmer air only changes the amount of air mass in the same volume, changing the mass of air that gets drawn on intake. The volume is the same, regardless of air density, and the throttle plate is a volume control, not a mass control.

What we are all trying to do here is to get the max Kilowatts out of every unit of fuel. Depending on the specific engine this can be improved in several ways.

But you're not doing this. By adding colder air, you're telling the engine to inject more fuel, not get more power from the existing fuel mix. In either case, the amount of power capable of being generated is already more than is necessary.

- All engines will benefit from a derestricted intake system until a certain limit.
- Some will benefit from a cold air intake
- Some will benefit from a hot air intake.

Some will benefit from a cold air intake for making more HP. None will make more power with a HAI, (barring certain examples involving engine dynamics, but not combustion) since there is less air, and thus less fuel.

So you can't really conclude this or that. Further more what is right at one rpm, might not be so at an other rpm. So it's complicated stuff, and it would take many hours on the dyne to dertermind the best for each car, and each speed.

Math is more powerful than speculation, and so far, you've only provided a dyno graph which hasn't much to do with what were actually discussing here. Show me some math that supports what you're saying.

Everything is a compromise - what you gain in one end you usually lose in the other end. So better FE at low rpm, will mean less power and FE at higher rps, and vise versa.

Noone's looking for better FE at high RPM's, buddy. Power and FE are also at opposite ends of the spectrum, for most purposes, so better HP at the top means (generally) more fuel used, which means less FE. They're almost never lumped together as being universally better or worse.

I've been working with CAI and derestricting intake systemes for four years some time ago, and at the time we saw significant gains on both hp and FE.
But things has changed in the past 10 years, and car manufactors and the ECU programs has changed a lot, so now things might look different, because of changed demands on emmisions.

Prove it. I can mildly believe that you got better FE by removing intake restrictions, and smoothing flow, but adding a CAI just doesn't do it for me, especially considering that it appears that you don't (or didn't) understand BSFC until a few posts ago.

I'm not saying that HAI dosen't work - I'm saying that it will be different from engine to enegine what works best, as the engine, car driver etc. are different, and thus you are optimising for different situations each time.

Scientific results control all those variables down to engine only to determine which of the variables that are in play will produce the best result. So far, there has been nothing but anecdotal evidence (that I've read) which supports a CAI giving higher fuel efficiency in any case that couldn't have been explained by another variable having been changed, such as driver input.

I maintain my challenge.

[Jyden]

@ Christ - I rest my case - I belive that we are "talking" past each other - hence further writing will gets us nowhere.....

I'm with my curret abalities within English unable to get my message through to you in a manner you can understand.

Thanks for the dialoque....