does a CAI really make sense in our cars? i mean, let's say you install a big FMIC, would a CAI really do any good since you would have that big FMIC anyway? with wet weather common here i would think a short intake connected to a FMIC would be better then risking it with a CAI which seems redundant.
CAI's in our cars...
- Thread starter SpicyRay
- Start date
Ok....this has been gone over in the big injen threads but I can understand you not wanting to sift thru all that crap. So here is your answer:
1) Colder air is always better
2) A CAI will increase turbo efficiency (especially helpful for higher boost with these small turbos)
3) The bigger thing in a turbo is to keep air flowing in the system...hence the larger, less restrictive filter
4) Stock, CAI vs SRI you probably won't notice too much difference, so long as they both go straight to the turbo as the injen...otherwise there are loses in the bends in the stock piping
5) A FMIC probably isn't necessary for this car considering the total efficiency of the system...an IC cooler of some sort would be better, or a slight relocation of the IC to prevent heatsoak (also a small problem w/ SRI vs CAI
In other words...if you plan on going high boost a CAI might be necessary down the road. If you plan on going stock-10psi look at MemphisRacer's SRi prototype and other products to free up the air flow. Then worry about the IC...believe me, the IC isn't the weakest link in the chain...just ask JoeP about his experience regarding this.
Hope that helped....
1) Colder air is always better
2) A CAI will increase turbo efficiency (especially helpful for higher boost with these small turbos)
3) The bigger thing in a turbo is to keep air flowing in the system...hence the larger, less restrictive filter
4) Stock, CAI vs SRI you probably won't notice too much difference, so long as they both go straight to the turbo as the injen...otherwise there are loses in the bends in the stock piping
5) A FMIC probably isn't necessary for this car considering the total efficiency of the system...an IC cooler of some sort would be better, or a slight relocation of the IC to prevent heatsoak (also a small problem w/ SRI vs CAI
In other words...if you plan on going high boost a CAI might be necessary down the road. If you plan on going stock-10psi look at MemphisRacer's SRi prototype and other products to free up the air flow. Then worry about the IC...believe me, the IC isn't the weakest link in the chain...just ask JoeP about his experience regarding this.
Hope that helped....
SpicyRay said:
Ok first of servoeyes' answer is very good, but if you want more detail here it is.
If you really want to know the true benefit of CAI it's b/c of thermodynamic. The turbo is a compressor and if you think about it, air is a fluid. Now as the compressor wheel compresses the air it becomes hotter and the pressure rise. Now as you know the compressor's power comes from the turbine, so how much the compressor can compress depends on how much engery is in the exhaust.
Common sense would say that if there's less work require to compress the gas, then for the same amount of work, the compressor can compress the air to a higher pressure ratio then with a hotter gas. This is basically what a CAI accomplish. It allows the intake of colder air than a stock or in certain instance Ram air intake. This means that the inlet temperature is cooler so less work is require by the compressor to compress a given pressure ratio. In our car's case 1.3 (19.7/14.7 assuming boosting at 5psig). This means less work is required from the turbine. This free up energy then can allow the compressor to compress the inlet air to a higher pressure ratio.
This is all what CAI does(ideal case only). Most CAI means a longer piping than the shorter ram air intake. Longer piping means piping loses due to friction and boundary layer. This means that there's pressure drop in the tube as the air flows through the winding tubes. Pressure drop is bad, b/c it means the work you put in to compress it has just gone to waste, but hey this is life and there's inefficiency and loss everything, go look at the 2nd law of thermo. If you want to know more about this go read some books. I don't want type anymore.
And sorry to the other ppl, this is the long about way of explaining how CAI works.
I'm sure Mr. White has some good explanations in his Book, Fluid Mechanics...Munson, Young, & Okiishi have a decent fluids book, and for thermo see Sonntag, Borgnakke, & Van Wylan
I also wrote one of these novels in the INJEN thread a while back, but have since been reminded my schools motto (by none other than Joe) : Theory and Practice...They are different things altogether. Thanks YuYuRena for the more advanced version...I really didn't feel like typing all that out!
I also wrote one of these novels in the INJEN thread a while back, but have since been reminded my schools motto (by none other than Joe) : Theory and Practice...They are different things altogether. Thanks YuYuRena for the more advanced version...I really didn't feel like typing all that out!
Just a quick note that no one considered the pressure loss due to the stock intake in the pressure ratio calculations. Since the stock intake is convoluted, it has a higher pressure loss than the Injen, so the stock turbo has to work harder (higher pressure ratio) to achieve the same boost pressure. By working harder, it raises the compressed air temperature and is therefore more vulnerable to detonation. Even with the intercooler.
Sorry, just got a copy of Maximum Boost by Corky Bell. Fun book, but dated.
Sorry, just got a copy of Maximum Boost by Corky Bell. Fun book, but dated.
See...I said something about the bends! Kinda...I should type out a big thing at somepoint that just goes over the WHOLE process and post the text as a downloadable file. But of course the best resourse for practical use is Mr. Bell's book (which I have not read, but trust is as excellent as EVERYONE has said!) It feels good to talk about this with out being flamed out!
