Re: Nissan Z, step aside

On Fri, 26 Oct 2007 06:53:56 -0700, Scott in SoCal
<scottenaztlan@[EMAIL PROTECTED]
> wrote:


>>With a 3.8L there will be more than enough takeoff torque and the
>>(modern design, and especially twin) turbo will kick in plenty soon. A
>>good turbo driver will have it spinning off the line and the challenge
>>will be keeping the wheels down rather than generating power. 
>
>There's no question a turbo will generate power at higher revs. The
>question is, given all the drawbacks, what's the advantage of a
>smaller turbocharged engine vs. a larger, normally-aspirated engine?
>Sure, you save a little weight, but is that worth all the hassles?

Most turbo's today blow heavy by about 2K RPM, so it's really not
"higher revs" anymore. Once you are off the line, it's cranking. I
have to admit, it took me over a year to figure out how to have it
blowing as you take off. When you first drive most turbo's you worry
about things like pulling out across traffic safely.  It's also worth
noting that most turbo cars today actually have the boost tuned down
in 1st and 2nd gear by the factory to reduce wheel spin and make the
cars more like NA cars. That can be "corrected" through hardware or
software.

I confess to not checking out this particular car in detail but most
twin setups are not usually what you'd expect - that is, they are not
two matching turbos, one on each manifold. One turbo can produce way
more boost than you can use on the street. But, the bigger the turbo,
the more spin up required. So most twin turbos usually have a small
turbo and a large turbo. The small one spins up very fast (but runs
out of boost), the big one spins up slower but generates lots of
boost. While a single turbo car these days does compromise a little,
most stock turbos and injectors can easily produce 100->125hp/liter
with limited/reasonable spin up time.  

Back to your question "is it worth the hassle?". Traditionally, the
turbo will get better mileage than the non-turbo for the same amount
of power as it is more efficient. 

Also, they aren't really very complicated. Every car is already fuel
injected and run by a computer metering fuel and/or air these days.
Engine controls throw feedback to the computer and it adjusts. Same
old thing. The turbo system just adds a little plumbing and a couple
more controls. It's actually very simple and easy to get your hands
around. 

I think the real draw is the incredible torque in mid to upper range.
With most NA engines I've driven, they can pull pretty hard but the
pull is fairly straight then it drops off. With the turbo, as boost
builds, the pull just starts increasing as the boost builds, like an
invisible hand pu****ng you along.  It's fun (and that's the reason
people like turbo and SC engines... the fun factor.)  

Editor's note: (not that I don't find an twin cam motor that will pull
8K RPM any less fun!) 

>>Nothing glows anymore and nothing melts or requires specific cool
>>down. 
>
>My understanding is that the cool-down is still necessary, but the
>cars just come with "turbo timers" to take care of the cool-down
>automatically, making the process less error-prone.

I don't think any designs have used that since the mid-90's, but I'm
no industry expert. Synthetic oil has made a big difference as dino
oil will coke up turbo bearings at shutoff. Previously, turbos guys
would let the engine idle for a little bit when pulling in to let the
turbo cool. I haven't heard of that being an issue in any recent model
turbos. 

>>I think you need to drive a newer turbo for a few days and
>>appreciate what it adds. 
>
>Got one to loan me? :)

Naw, but you local dealer would probably be happy to strap you in!