CAI and Forced Induction ... waste of time?

[Fatty]

Lots of interesting conversation going on in another thread right now about CAI on an NA engine. Rather than take that thread off topic, i thought i'd start another to discuss this issue.

From the other thread:

Why would you want a cold air intake with a intercooler????
The intercooler will remove the heat and feed air into the intake at near ambient temperatures.
All air under the hood is around 70degC as it's feed thru the radiator (I've done extensive measurements under the hood (it was cramped under there )) CAI will help on na engine but is pointless when you have an intercooler.
Ted

OK so I agree with Ted that underhood temp is very hot (especially when you add in the extra heat of a turbo) . However I'm struggling to beleive that an intercooler will "remove the heat and feed air into the intake at near ambient temperatures" . It may remove a large percentage of heat but it could never be 100% effective.

So , given the above line of thinking, when i installed my turbo i retained a CAI. i figure, at the very least i'm giving the intercooler a "helping hand" by feeding slightly cooler air into it, to start with. Makes the job easier for the intercooler this way.

I guess i won't really know until i do some comparitive tests of air temps, post intercooler, with my CAI setup , then the more conventional underhood pod filter setup most turbos seem to run.

So, has anyone done these tests already? (would save me the time) or can anyone add any thoughts to this? if the CAI is not doing anything useful, i might as well remove it and save a few feet of intake (better throttle response, and lighter weight! )

[d-mag]

It makes sense to me......then I'm no genius.
I'm in the process, well, the mechanic is, of putting a temp sensor on the intake after the intercooler.
I also plan to do some sort of CAI/shield/BEGI Box sort of arrangement under the hood too.
The ECU allows for data Logs so I'll log the intake temps during different types of conditions before and after the CAI and see if it makes a difference.

[Fatty]

well please let me know the results! talk about perfect timing

[MX5CHIC]

Oh no, I'm not getting inolved in this one ..... I will be building a complete forced air cold intake for my NB over coming weeks - I'll post up all my measurements for the before and after setups.

CAI Intakes have become so popular with all types of cars, whether they be Carburettor, Fuel Injection, Turbo .. whatever, and I'm sure everyone would love to know for certain if they are really worth the effort and expense.

This sure has become a HOT topic lately (forgive the humour)

[Fatty]

This sure has become a HOT topic lately (forgive the humour)

[Fatty]

d-mag's results may be a while coming, so still interested in other peoples thoughts / test results please

[93_Clubman]

can anyone add any thoughts to this? if the CAI is not doing anything useful, i might as well remove it and save a few feet of intake (better throttle response, and lighter weight!)

As for the heat ingress to the motor, well that is always going to be affected by what you put in at the entry point, air velocity has an enormous effect, if you begin with an entry temp of 70 Deg C and pick up 15 Deg C along the ducting then you have induction temp of 85 Deg C. It stands to reason then if your entry temp is 20 Deg C + 15 Deg C you have induction temp of 35 Deg C.

Can only echo the above - also understand that one of the Canberra forum members, or someone they know, spent a lot to get a CAI custom made to draw from the below windscreen cowl area on their SC'd MX5

[Sasso]

Haven't you got an IAT sensor? just take some logs with and without the CAI and see if it makes a difference. I'll see if it makes a difference one day when I get the chance to put the turbo back on. I don't see why it shouldn't help, anything is better than nothing.

[Fatty]

just take some logs

how do i do that? (currently on stock ecu with dfa piggyback)

[SuperMazdaKart]

every bit of cooler air helps. especially in summer when the fmic is picking up more heat from the road.

[Rotary]

can anyone add any thoughts to this? if the CAI is not doing anything useful, i might as well remove it and save a few feet of intake (better throttle response, and lighter weight!)

As for the heat ingress to the motor, well that is always going to be affected by what you put in at the entry point, air velocity has an enormous effect, if you begin with an entry temp of 70 Deg C and pick up 15 Deg C along the ducting then you have induction temp of 85 Deg C. It stands to reason then if your entry temp is 20 Deg C + 15 Deg C you have induction temp of 35 Deg C.

Can only echo the above - also understand that one of the Canberra forum members, or someone they know, spent a lot to get a CAI custom made to draw from the below windscreen cowl area on their SC'd MX5

It is too that effect, but a little different this time becuase if you had an ideal 100% efficient intercooler then the tempreture would always become whatever the outside Temperature is, I'll illustrate what i mean.
lets say outside temp(Deg C) is 20, and induction temp 30, after Turbo lets say the temp gets to 100, then a 100% efficient Intercooler will reduce temp back to 20.
Now if it were Hot induction temps of 60 then after Turbo temps would be maybe 150(not accurate), but if the intercooler remains at 100% efficiency then temps would drop to 20 again. so no difference.

Is there such thing as this ideal intercooler? Yes and No, I have read that some Powerboats with a constant flow of cold water, have intercoolers with efficiencies of up to 100%
But in practical car systems, a good Intercooler is only around 60-80% efficient,

So for all practical purposes the difference to power will be very significant, with a drop in temps entering the piston, this will mean you can add 1-2 psi more boost, for even more power
Which makes it possibly more important than on a N/A engine

[Matty]

Forgetting the intercooler efficiency for a moment, I would hazard a guess that the compressor works more efficiently with lower inlet temperatures. But my thermo memory is a little hazy...

Certainly the less heat the intercooler dumps, the less heat is going into your radiator.

[Fatty]

Certainly the less heat the intercooler dumps, the less heat is going into your radiator.

hadn't even thought of that. thats a neat little side benefit and worth keeping the CAI for that alone.

thanks for your thoughts everyone.

[Juffa]

Good Topic Fatty.

When I first installed my ECU I was NA. I attached the air temp sensor to the outside of the pod air filter. At that time the filter was sitting where the OEM airbox used to sit, so quite close to the exhaust manifold. I often saw temps of 50+c at the filter when on the road. Popping the headlights would drop the temp a few degrees.

After going FI, with a very large intercooler, and the air temp sensor mounted just before the intake manifold I was seeing intake temps between 20 and 30c on the road. The intercooler was blocking the radiator however and therefore causing coolant heat issues. I swapped to a smaller intercooler (thanks Fatty). No more overheating and the intake temps have only changed up by a couple of degrees. A small price to pay for getting the coolant temp under control. The pod filter now sits right behind the headlight.

I remember seeing a white NA on this forum with a FI setup installed by Mania. It had a CAI setup. It would interesting to see what statistics are available from that?

I would also imagine that whatever method of controlling your fuel and boost you are using would need to take the intake air temp into consideration in order to get the best efficincies from the system.

J

[Fatty]

i should have kept that intercooler juffa.... i think mine is a bit too big now

yes i remember the white car, was that fuzzlets old car?