Well as the subject says, what is the max CFM on a stock Nikki? And what is the approximate CFM at say 3k or 4k RPM? I'm wondering about the possibility of a ghetto turbo setup and need to know if it's even feasible the way I'm thinking about it.

Thanks,
BrianHeston

 

In stock form it has a max of 300 CFM but can be modified to have 420 CFM.

 

I calculated at one point, for an "average" compressor efficiency (I think I used 65%), I'd have to have a turbo that could flow 450cfm at 2:1 pressure ratio (14-15psi boost) at 8000rpm. This is either a BIG T3 or a small T04.

If you have the formulae, just calculate for a 2.3l piston engine that has about 80% volumetric efficiency. (About right for stock ports)

You shouldn't have to worry about carb CFM unless you're trying to do a drawthrough setup. Blowthrough setups actually prefer a slightly-small carb, believe it or not, so the stock Nikki should be fine. (One place uses stock Nikkis on bridge ported engines, blowthru carb, run 11's or 10's, forget which...) Drawthrough you obviously need a MUCH bigger carb because the air isn't compressed before it gets to the carb.

 

Peejay thats realy interesting about the carb requirements for blowthrough. I was thinking of going 48IDA but if your figures are correct it will not be necessary. As discussed on another thread I am thinking of modifying the rotors and going about 10psi with a TO4. Did think of EFI but its a lot of bother on a 12a.

 

I thought the Haynes book said the stock nikki was 445cfm? I'll have to check it when I get home. There was a J-spec 12A turbo in Japan. Does anyone know how to get some tech info on that car? Maybe someone could figure out how to replicate the fuel system for us American boys (and girls) to run turbocharged 12A's

 

These are the two possible ways that I'm thinking of doing it. Tell me if I'm nuts. And if one of them makes sense, let me know that too!



BrianHeston

 

You're nuts.

The stock air cleaner will blow apart unless you're running VERY low boost pressures. Even then, keeping it sealed would be a problem.

Put it this way... how big is the stock air cleaner, 14" around or so? 14" around is 154 square inches. At 5psi boost that's 770 pounds of force trying to blow the lid off...

 

So let's say, just for the sake of argument, that I had an air box that could handle the pressure. Any other problems, like tearing the filter apart or anything like that?

BrianHeston

 

Filter goes on the inlet side of the turbo or supercharger.

They make such air boxes as you describe, although they're properly called carb hats or bonnets

 

you mean like a CAI pipe and a cone filter on the end?

And will you un an intercooler?

 

Well with my budget right now, I'm not planning on the intercooler, but it is a possibility in the not so distant future.

 

I've just now read this, and I have to chime in. I'm a mechanical engineer, and I have played with turbo / intercooler setups.

Power from a gasoline engine is nearly linearly proportional to the DENSITY of the incoming fuel/air mixture, not the PRESSURE

By compressing the air through a turbine, you are increasing its pressure. Thermodynamics dictates that as you compress a gas you increase its temperature. Increased temperature of a gas means a lower density. Its all to do with the ideal gas law. This is why a properly designed intercooler is so necessary to achieve increased density.

Intercoolers remove heat from the compressed air, and therefore increase the density of the air, ideally with a minimal pressure drop across the intercooler core and maximum heat transfer rate while still remaining compact. Its really challenging to design one. I did in school.

The deal is if you only compress the air, you aren't running a turbo, you are running a supercharger. The only way to make superchargers work is to run the carb really super rich to attempt to cool the fuel / air mix, so economy goes right out the window.

All you guys out there tuning for the max boost they can achieve, I suggest that you consider improving your intercooler first. I've known guys who have this slick water tank setup, where a small amount of water from the tank is sprayed on the outside of the intercooler, and therfore increasing the heat transfer rate due to impingement of the atomized water droplets.

Bottom line is this: look for increased air density, not pressure. Compressing air increases temperature, which lowers density. Removing heat and increasing pressure increases density.