Bonnet Scoop - Air Vents for Cooling

[randymx5]

good work MX5CHIC

[matt9111]

Lol, yeah pretty low hey, my mates 180sx, stock SR20 with a full exhaust, Garret T28, bigger intercooler (not sure which...just big!), on 13psi did 177rwkw, so I assume the dynos about right, his power figures seem about right for his setup.

As for MX5CHIC's results....with your K&N setup, is it a box type filter or a pod?
Because my car is definitely running richer with the K&N pod on, it even showed up on the dyno, ill post my results in the dyno section if I can figure out how too lol


Cheers Matty

[MX5CHIC]

My Current system is a CAI with pod filter - this is the system that is running my engine very lean, no pinging though.

[grump]

MX5CHIC, where are you picking your air up from ,inside the engine bay or outside.?

[Boags]

interesting - now my next move is to get cooler air to the filter which will (should?) run the engine slightly richer thus increasing power output

Please explain.

Does the stock ECU increase fueling for cooler (denser) air? Or do you have an aftermarket ECU? Without an increase in fuel it will be leaner.

[MX5CHIC]

My non stock K&N CAI System is drawing air from under the bonnet presently and I have a standard ECU - it seems strange to me that for the 3 1/2 years that I have had this car, every time that I have changed or inspected the spark plugs they have been a dark carbon colour (on the rich side).
It is only since I fitted the K&N Pod Filter and intake that the car has consistently run lean, an almost white colour on all spark plugs - both systems draw air under the bonnet, same 98 octane fuel, no major services or other engine modifications.

[Rotary]

interesting - now my next move is to get cooler air to the filter which will (should?) run the engine slightly richer thus increasing power output

Please explain.

Does the stock ECU increase fueling for cooler (denser) air? Or do you have an aftermarket ECU? Without an increase in fuel it will be leaner.

The Inlet Air Temp Sensor will allow for accurate temp compensation. and therefore the mixture won't be any leaner or richer from change in temps

My non stock K&N CAI System is drawing air from under the bonnet presently and I have a standard ECU - it seems strange to me that for the 3 1/2 years that I have had this car, every time that I have changed or inspected the spark plugs they have been a dark carbon colour (on the rich side).
It is only since I fitted the K&N Pod Filter and intake that the car has consistently run lean, an almost white colour on all spark plugs - both systems draw air under the bonnet, same 98 octane fuel, no major services or other engine modifications.

There may be a few factors contributing to this, Some may or may not be relevant to your situation.

The first two will make large differences to mixtures seen by the plugs, and would be hard for most people to rule out completely,
Driving style and more importantly driving conditions, i.e. drives with longer trips(Leaner) as opposed to shorter trips(Richer), more highway driving(leaner), whereas city or congested driving(richer). So something like moving house or changing jobs could easily affect this, or just going on long drives more often than previous.

Ruling this out, there could be an aging of onboard sensors, in particular the O2 Sensor, which can vary its readings slightly with age,
This is important because this sensor is most responsible for the feedback to the ECU in keeping mixtures in check most of the time, and can adjust for many system changes, but it can’t compensate for driving conditions or style (due to closed loop and open loop operation)

Other factors could be placement of Inlet Air Temp Sensor with respect to pod (but this can be easily ruled out if done properly)
The other possibility if you could rule out all of the above, is the effect of change in flow conditions before and then through the MAF(Mass Air Flow) Sensor.
To measure airflow as accurately as possible a MAF sensor has a wire Mesh or Plastic grill placed in front to make the airflow throughout the device more consistent and measurable, so this should compensate for most variations of airflow paterns before entering, but its not a perfect system, and may or may not be a factor.
(ps: Not debating just trying to be helpful )

[MX5CHIC]

I have this nagging feeling that if I was to put the original airbox intake system back on, my plugs will be carbon black in colour again ........ I might just try it to prove or disprove my theories on air intake systems
I have a theory that it may actually be a result of the differences in air velocity and total air volume that is gained by most aftermarket air intake systems.
Has anyone else checked their spark plugs before and after fitting a CAI System?

[Rotary]

I have a theory that it may actually be a result of the differences in air velocity and total air volume that is gained by most aftermarket air intake systems.
Has anyone else checked their spark plugs before and after fitting a CAI System?

Mx5chic, what you do need to understand, is how the correct fuel ratios are worked out.

They are worked out as Mass to Mass ratio’s (i.e. Mass of Air to Mass of Fuel)
Not volume or anything else, just Mass

In the older Fuel systems a pressure sensor(MAP) was used to calculate the Mass of air entering the system (as Mass ,Pressure and Volume are related by the gas laws.)

But in modern systems that now use MAF(Mass Air Flow) Sensors, the volume, pressure and velocity can vary but are not important for measurement purposes and system accuracy.
The MAF quite simply measures the exact Mass of air entering the system and that’s all we need to know for our Fuel Ratios.

So an increase in Air flow from the filter system or other will have no effect on ratios, because the system is designed to read a wide ranging change in incoming Air Mass(due to the huge variation seen by throttling)

Just to simplify, volume- pressure- velocity etc can be used to work out the Mass of Air, but is not necessary as the MAF gives us our required Mass reading(accurately)

[MX5CHIC]

Actually Rotary, I agree on the principles of Airflow, Pressure etc. But what would you consider to be the cause for the major difference in plug colour, or more specifically the Rich running VS Lean running
Remember, no changes have occurred to fuel type, driving habits or engine tuning / modification.

[bruce]

I don't think looking at the plugs is as accurate as in the old days of carbies.

[MX5CHIC]

Yes but your plugs provide a clear indication of what is happening in your combustion chamber, my engine has always run on the rich side, so therefore something significant has occurred for the engine to now be running very lean.

[93_Clubman]

Has anyone else checked their spark plugs before and after fitting a CAI System?

Found that after fitting the Simota pod & MX5 Mania carbon fibre funnel drawing air from the cowl area below the windscreen that spark plugs indicated slighly leaner running than the typically rich that NA6/8 are noted for.

[MX5CHIC]

There you go ...... "cause and effect".

[Rotary]

Its as Bruce said.

What does a spark plug really tell us,
Does it tell us the what the Air/Fuel ratio is exactly?
Does it tell how the A/F ratio varies with RPM?(it varies greatly with injection)
Does it tell us what idle mixtures are?
Mixtures at cruising velocity?
Acceleration Enrichment?
Mixtures at various throttle openings?
Theres more but the above represent variations anywhere from 11 to 15+ in A/F ratios(huge)

It’s the bluntest way to test something, and if not used correctly it won’t tell you anything useful.
All the above mentioned vary greatly from day to day, and you cannot control them. Do you travel down the same road and stop at the same traffic lights for the same time every day, with the same amount of cars going exactly the same speeds and accelerations?
So the mixtures a spark plug will show, will vary greatly day to day week to week anyway.

The way plug tuning can be bluntly but slightly useful, is when all the above variables(there’s plenty more) are removed from the testing, and how a good tuner would use them for carburettor jetting.
Full throttle testing, usually in a track environment, so a tuner with great experience may be able to see the changes made to the jetting. Not in regular driving as even a carburettor engine would see the great variations I mentioned above.
If you do use it you will mislead yourself in coming to accurate conclusions if that’s what you want to achieve,
if you want to have fun and learn then what your doing is great.