Craig Bower said:
Hi,
Don't take this as a flame, but allow me to correct some of your
mis-information...
I love this statement:
Torque based turbo management, sounds darn fancy doesn't it?
Sounds like it's engineered to give you more power, right?
WRONG - torque based turbo management means the engine
management computer is ACTUALLY pulling some of the boost
back on the engine at certain RPMS and Throttle conditions to
ensure transaxle longevity. I.E. no massive torque-shock-loads
go into the transaxle thereby hopefully eliminating transaxle warranty
claims.
Actually, according to SAE Technical Paper Series 2003-01-0410 titled
"Turbocharging the Chrysler 2.4L Engine" (which is written by 2 DCX
employees, compiled from info that 10 engineers who designed new components
for the 2.4L Turbo : "Unlike mechanical boost control strategies of the
past, the 2003 2.4L Turbo has torque-based boost control. The driver's
throttle input in interpreted as a desired torque. For a given throttle
input, the driver will receive the same torque output from the engine,
regardless of ambient conditions (temperature, barometric pressure, etc.)
NGC (Next Generation Controller - the name for the new PCM design) can also
reduce the torque as required under certain conditions to ensure powertrain
durability."
So there is merit in the interest in transaxle longevity. However,
compensating for higher ambient temperatures by providing higher boost to
obtain the same torque as lower temps for the same throttle position does
not qualify as ensuring powertrain durability (See Sport Compact Car
magazine, October 2003 issue, for this tidbit of info regarding torque based
boost management.
The stock PCM was bad about pulling boost when a mechanical boost controller
was installed. It had the equivalent of an electronic boost controller
inside the PCM, and it was willing to derate performance to regain control
of managing the boost. The 2003 PCM in the turbo had fairly new software on
a new engine platform, and had a few oversights. The Stage I PCM corrected
a lot of them.
Now we are talking - St-I is nice - and it reduces the "torque based
turbo management" effects to near zero, the bean counters figure
the "few" enthusiasts who put this kind of kit on their car, most likely
won't overshadow the savings in stock transaxle longevity.
Yes, there is even a feature for Boost hold during WOT shifts in the Stage I
advertisements. In addition, it increased WOT part throttle boost, improved
Wastegate control routines for better turbo response, enhanced first gear
boost schedule and reprogrammed for a soft rev limiter. However, they
retained the torque based boost control that was inherit in the PCM design;
still provides the same torque for any pedal position regardless of ambient
conditions.
Yup, sounds good except the no additional torque portion. Torque is what
you're going to need to move a big-brick (PT cruiser) through the airstream
el rapido during acceleration! It sure is nice to say 260hp though! I'd
be curious to see on back to back dyno runs and quarter mile times/mph for the
stage I vs the stage II setup. Without any additional torque, I'd be
surprised to see much change except for MPH in the top end of the
quarter.
I haven't seen any curves on it yet, but I can imagine that they have
concentrated on the area "under the torque curves" to get the torque as high
as possible, and as early as possible to try to maintain a fairly flat
torque (and HP) line. If they are optimizing for high speed, they will have
to do something about the speed limiter that has been a part of PCM
calibration..
As it is now, the Stage I reaches above 250 ft/lbs torque around 2300 and
maintains 260 ft/lbs from 3600 to 4400 RPM. Remember that comment about
"natural powerband? HP peaks at 235HP at 5200 RPM. Remember the comment
about where the "natural powerband" tops out? Also, when easing into
traffic, getting straightened out and pointed in the direction you want to
travel, the wheels don't break loose until the 3500 RPM mark. I don't think
it is coincidence that the torque reaches it's apex there. Even though the
GT is turbo charged, it is still a 2.4L based engine. The 3500 to 5500 RPM
Power Band seems to carry over to the turbo, and both the performance curves
and actually operation go far in verifying it.
And my "stock" Dodge Omni GLH-Turbo (with intercooler!) will gladly hand
any stock PT GT it's ass on a silver platter!
Mind you my GLH isn't
really stock! Have you seen some of the numbers people are getting out
of the SRT-4's?? Them things are in the 12's and 11's already! - Insane,
but
I like!
The GLH was the ultimate sleeper. The SRT-4s are really creating some
excitement. The 2.5L turbo Forrester XT is starting to get under the skin
of the SRT-4 group. There is a trend toward performance re-emerging in the
industry, and it is encouraging. I guess they had to do something to regain
the interest of the buyer.
Compared to what? Honda? Toyota? McCain's apple pie?
Consumer Reports - (FWIW), and PT Cruiser owners. While there have been
some problems with power steering, DCX has been good about issuing recalls
before damage is done. Overall, PT owners have been satisfied with their
cars, and the industry reports lower than average reliability issues, in
terms of frequency of repairs.
Hmmn, yeah you said it there - small turbo ... it'll spool quickly, but once it
runs out of steam, seriously it runs out of steam. It eventually simply
chokes off the exhaust system as it is a huge source of backpressure.
And I'm not sure what you mean by the "natural" powerband of the 2.4L
you can't have your cake and eat it too. Simply put the 2.4L in your PT
does not have a "natural" powerband, i.e. naturally aspirated. It is
Supercharged, or more accurately Turbine-Supercharged or Turbocharged.
Thus, the engine doesn't magically stop using the turbo at 3500 rpms
and shift into naturally aspirated mode. Every single cubic foot of air
going into that engine or coming out of it goes through the turbo, no if
ands ors or buts. And with a small turbo, if you want to see more power,
eventually you'll have to trade off and go with a "big" turbo - I.E. a
Garrett AiResearch T03 or T04 to reduce exhaust backpressure and move the
turbo boost/dynamics maps closer to where you want them to be for the level
of performance you are trying to attain.
See above about the natural powerband . Even if the concept is pervceived
as snake oil, the can be little doubt when looking at the curves and seeing
where the tires will break loose under WOT, clutch fully out and pointed in
a straight line. The NA Cruisers were no different. You could tell from
the sound of the intake where the engine was "breathing better". If it
didn't carry over as a trait of the basic 2.4L engine, DCX sure spent
considerable effort in the PCM calibrations to mimic the response between
3500 and 5500 RPM.
There is a drop in both torque and HP after the 5200-5500 mark. I think the
plans for Stage III call for both a larger turbo and an enhanced fuel
delivery system. As it is, the GT has a non-return fuel system which
delivers 58 PSI. It is possible that the turbo scroll area could have been
matched to fuel delivery capabilities to lessen the chance of leaning out.
I like the smaller turbo. It has very little (if any) turbo lag, and the
exhaust system has been optimized to keep the low end torque high. There
are plans for stage II to offer an optional 3" cat back system. I can only
guess that due to the progressive increase of sizes from the O2 sensor
housing (2 1/4") to the cat (2 1/2") and finally to the 3" catback system
that they are looking to let the natural cooling of the exhaust gas in a
larger pipe to create the same density, while handling a larger volume of
extraction. This would let the car have a larger exhaust while preserving
low end torque. Since the turbo and exhaust manifold are a single piece,
there isn't a chance for headers...
Surprising engine reaction? - Try a Turbo Omni man - fight for your life to
stay on the road when full boost hits - now that's surprising, only if you
don't know it's coming!
Yeah, but 900% of "Ricers" don't have fast cars, they worry only about
appearance, so you now know the value/fun/excitment rating of driving
a "sleeper" vehicle. Your PT can do way more than is expected of it
from these ricer clowns, fun isn't it?!
Hmmn, my Omni GLH-Turbo is a grocery getter, what kind of treatment
did you have in mind? - Maybe a Zaino treatment and some plastic polish
on the tail lights for the imports to see?
God knows no PT cruiser will
compete with a 2200 lb Omni running 14psi of boost through an intercooler
netting 205hp and 275 ft-lbs of torque the old fashioned way, with a 2.2L
The "treatment" is the attention that the market is giving to the PT, Subaru
Forrester and Subaru Baja ( I don't know what is next). They look like
unlikely candidates to be performance oriented, but that is the way the
market is leaning.
There is no doubt about the merits of the GLH. It has been referred to more
than once as the design concept that could have been used as an intro for a
boxy vehicle like the PT to receive the turbo treatment. The PT weighs
between 3300 to 3800, depending on the load, seats in or out, gas tank full,
etc. To get the kind of performance that it has is hard to imagine.
Getting below 14 secs in a PT is like getting below 12 in a lighter weight
vehicle. I like mine, and continue to be impressed by the Stage I addition.
I guess I am a candidate for Stage II when it is released. The PT owners
with the turbo and stage upgrades will be a good test to see about the
durability of the design. My guess is that if DCX is planning on releasing
staged upgrades to build HP and Torque near the 285 mark that the engine was
designed to deliver 10% to 20% more. It will be interesting to see how the
trans-axles hold up to the challenge.
