Very informative for those who aren't well versed in engines and the like.

However, it still doesn't tell me if twin turbo is better than single turbo. Is there any way you could amend your post to include that info?

 

IMO, ONe isn't better than they other. Same with N/A vs. F/I & Turbo vs Supercharger. Everything has its pluses and minuses. You need to build your car around your wants and needs. IE: Someone that is a major autocrosser is going to invest in suspention, brakes, & stay N/A vs the drag racer that wants a high output HP car to complete the 1/4 as fast as posible. Also, and this is the biggest kicker, is money. I'm sure if we all could afford a Ferrari we all would own one. Some people just can't, for whatever reason, afford to completely build their motor and do a major twin turbo build.

All-in-all, I don't think one way is better than the other. Guess that is why I just enjoy seeing a fellow Z owner enjoying thier Z however it is built*.

*To an extent.

 

I was being sarcastic , but a good response none the less.

 

There is at least one member among us who does own such a car.

 

And he can afford such car. BTW: PM Link please.

 

I'm surprised that someone did not point out the NA has no more than 14.0 psi plenum pressure [WOT atmospheric pressure] and F/I exceeds that by what ever amount the external mechanical device adds.

 

wouldn't that be 14.7 psi for 1 atmosphere............

also, what about those people who live in area below sea level (NOLA, for example)? would they have slightly higher pressure in a naturally aspirated manifold?

 

Good write up, sticky would be a good idea.

 

awesome write up

One thing I'm going to disagree with is the use of the phrase "turbo lag" when describing centrifugal SC's:

it can only have (turbo) lag if it is exhaust driven and indirectly driven by the engine itself.

-The exhaust energy indirectly spools turbos.
-The turbo and engine do not have a consistent relationship at all rpms.
-The boost at rpms relationship varies depending on the gear you're in

-The engine belt directly spins the supercharger.
-The supercharger and engine do have a consistent relationship at all rpms
-The boost at rpms relationship does not vary in different gears

lag isn't the time between zero and full boost, it's the time between negative/zero psi and positive psi
A turbo needs to first spool to create positive boost. A supercharger is already spinning and can immediately create positive boost - though the amount of positive boost may depend on the rpm





Another thing I'm going to disagree with is this:
faster compressor rpms is not necessarily an advantage.
The trade off for such high rpms is the drastically higher amounts of heat turbos make - they can actually get red hot from the heat.
This can raise under hood temps, and strain the cooling systems more.

Superchargers do not spin nearly as fast. They don't ever get all that hot. You can often place your hand flat on them after driving the car hard not not get immediately burned.
They also don't spin as fast because usually the impeller blades are are larger than the smaller, but faster spinning turbos







you should expand on this and list the reasons:

- lower torque due to low boost at low/mid rpms
- more parasitic loss
- belt maintenance
- difficult to reach insane high power levels since power is limited by both the belt system and the displacement/flow of the engine
- blower noises


the advocates disagree and feel it combines some of the best qualities of a turbocharger and supercharger:
- high power
- no lag, linear throttle response
- low heat
- easy install
- low cost
- no hood modifications
- flat torque curve
- bypass valve sound
- generally considered safer for engine

 

Afte having a JWT TT installed and driving in a few single turbo Z's I can tell you there is a difference. The Twin Turbo's power comes on like a tidal wave, no pushed in the seat feeling, it just continues to build power as you accelerate. The Single Turbo has the power come on like a nuclear explosion. You are pinned in your seat and the acceleration feels like it's going to throw you into the rear hatch. One set-up isnt' better that the other rather they are different approaches to F/I. Bigger ISN'T always better!! To get the most from either set-up you need to evaluate what your goals are.

 

your description isn't entirely accurate. I have driven both out of box single turbos and twin turbos. While some singles may come on very hard; "like a nuclear explosion" I find a properly matched single turbo should have a very smooth power delivery. I had a local running an APS single and the power delivery was about as perfect as one could want. I have a twin turbo setup on my car and the power can come on like a freight train and honestly unless you are really on your toes, can be overwhelming. The single was very predictable and pulled all the way to redline