Does anyone on here have a Supercharger kit on a 986?

[911monty]

IMHO superchargers on a 986 stock motor is a losing proposition. One distinct problem is the high compression and lack of dome volume in the stock form. These engines want a cool dense air charge. A supercharger running high pressure looses efficiency by creating heat of compression aka adiabatic heat. This is a killer as the supercharger is simply heating the intake charge by beating from compression. Efficiency falls dramatically. To properly utilize a supercharger you want low compression around 8.5 to 1, flat top or dished pistons and large domes are desired. Reason being Theoretical volume. eg if you have a 2.5 liter engine (swept volume of the piston) and add 100 cc of dome volume (for illustration purposes) then you have now increased the theoretical displacement to a 3.1liter engine (2.5 L or 2500cc + 6 X 100cc.) This is because the supercharger fills the swept volume plus the dome volume. You can now use less boost pressure and increase adiabatic efficiency. You now enjoy the benefits of a theoretically larger engine, and a s the saying goes there is no replacement for displacement.

[Qingdao]

Originally Posted by 911monty

IMHO superchargers on a 986 stock motor is a losing proposition. One distinct problem is the high compression and lack of dome volume in the stock form. These engines want a cool dense air charge. A supercharger running high pressure looses efficiency by creating heat of compression aka adiabatic heat. This is a killer as the supercharger is simply heating the intake charge by beating from compression. Efficiency falls dramatically. To properly utilize a supercharger you want low compression around 8.5 to 1, flat top or dished pistons and large domes are desired. Reason being Theoretical volume. eg if you have a 2.5 liter engine (swept volume of the piston) and add 100 cc of dome volume (for illustration purposes) then you have now increased the theoretical displacement to a 3.1liter engine (2.5 L or 2500cc + 6 X 100cc.) This is because the supercharger fills the swept volume plus the dome volume. You can now use less boost pressure and increase adiabatic efficiency. You now enjoy the benefits of a theoretically larger engine, and a s the saying goes there is no replacement for displacement.

Long story short... Superchargers are just terrible.

I have 32 thousandths of ring gap in my car. Why? cause superchargers are just terrible. I also run 8.9:1 compression; and I still have a locked distributer with 1* of boost retard for each PSI over 2#s.

That being said there is NO replacement for the noises the roots blower makes right behind your head. Its simply orgasmic.



If you wanna go fast check out turbo. Turbo is good. The noises it makes are cool if its your first turbo car.


ike84: Na, I've been too chicken to run the nitrous yet. I spun a bearing and had to pull the engine... again. Oh well I got 2000 miles on this rebuild so give me a few more months of enjoyment and I'll squeeze the giggle gas button and break it some more.

[Johnny 5]

Originally Posted by Qingdao

California government says "we burn coal only; no gasoline cars here". LOL

Not as fast as you'd think. About 10psi.

Yea California is getting ridiculous! Depending on the city they do random road stops and if your car looks or sounds modified they run a sniffer to it and can tow your car right on the spot! Yes you heard me they have an actual mobile smog vehicle.

Originally Posted by beater986

Just register the car to a mail forwarding address in another state or county with no emissions.

There is a place up North that has no smog laws but I think California is getting smart with that stuff. Not sure if forwarding mail will do the trick. Used to work from my understanding but never really knew how that works or looked into it. Most of my vehicles pass smog...well used to before the DME crap so will see what happens.

Originally Posted by 911monty

IMHO superchargers on a 986 stock motor is a losing proposition. One distinct problem is the high compression and lack of dome volume in the stock form. These engines want a cool dense air charge. A supercharger running high pressure looses efficiency by creating heat of compression aka adiabatic heat. This is a killer as the supercharger is simply heating the intake charge by beating from compression. Efficiency falls dramatically. To properly utilize a supercharger you want low compression around 8.5 to 1, flat top or dished pistons and large domes are desired. Reason being Theoretical volume. eg if you have a 2.5 liter engine (swept volume of the piston) and add 100 cc of dome volume (for illustration purposes) then you have now increased the theoretical displacement to a 3.1liter engine (2.5 L or 2500cc + 6 X 100cc.) This is because the supercharger fills the swept volume plus the dome volume. You can now use less boost pressure and increase adiabatic efficiency. You now enjoy the benefits of a theoretically larger engine, and a s the saying goes there is no replacement for displacement.

I hear you on that! I mean these kits are boosting so low I really don't think it would be a problem. As for the intake air heat Im thinking of throwing on a air to water intercooler just got to take a better look at things while the replacement engine is in.

Originally Posted by Qingdao

Long story short... Superchargers are just terrible.

I have 32 thousandths of ring gap in my car. Why? cause superchargers are just terrible. I also run 8.9:1 compression; and I still have a locked distributer with 1* of boost retard for each PSI over 2#s.

That being said there is NO replacement for the noises the roots blower makes right behind your head. Its simply orgasmic.



If you wanna go fast check out turbo. Turbo is good. The noises it makes are cool if its your first turbo car.


ike84: Na, I've been too chicken to run the nitrous yet. I spun a bearing and had to pull the engine... again. Oh well I got 2000 miles on this rebuild so give me a few more months of enjoyment and I'll squeeze the giggle gas button and break it some more.

He's got a point the sound of that roots is awesome. I know this is going to be pushing massive amounts of power but I really think I can make this pretty reliable once I figure everything out

[Johnny 5]

On a side note does anyone have the 987 airbox installed? Did you end up using the 987 mass air flow as well? This kit didn't come with the intake piping and Im trying to figure out if I want to go with the 987 airbox and maf. Cold air intake is another possibility. Just trying to see what my options are.

Also how well do these dme's work? Would going with a 987 maf help with a little bit more fuel to the factory injectors? Im trying to keep the dme stock due to the new regulations and use a aic for the additional injector only.

[Johnny5]

Originally Posted by Johnny 5

He's got a point the sound of that roots is awesome. I know this is going to be pushing massive amounts of power but I really think I can make this pretty reliable once I figure everything out

Correction I mean to say not going to be producing massive amount of power.....

[gonzzo]

I just saw this, i have a TPC supercharger in my 98' 986, installed it myself.

Let me know if i can help.....