Here at ARD Tuning one of the most enjoyable aspects of our
work is when we are asked to participate in interesting new projects. We were
quite fortunate to be commissioned by Ron Edwards of CKA motorsports to
co-develop a stage 3 package for his newly acquired 2.5l automatic LPT (Low
pressure turbo) 2007 XC70. Our goal was very clear from the get-go; produce a
significant increase in horsepower and torque across the power band without
sacrificing engine longevity and daily driving comfort.
To start on the project, we headed over to Portland Speed
Industries’ Dynojet chassis dynamometer to get some baseline numbers and to
verify that all the stage 0 items had been completed. Starting with a solid
foundation is key; it is absolutely imperative to go through the vehicle and
make sure all wear items are in OEM new condition or better before trying to
make additional power. This is so important to the performance of these cars
that the Volvo community has coined a term for it: Stage 0. Thanks to diligent
maintenance by CKA motorsports the XC arrived prepped and ready for some
Dyno charts provide very useful information as is; however,
they become even more useful when you compare them to the calibrations within
the ECU. The first thing most folks will notice with the 2.5l LPT is that in
stock form both the boost (shown in the lower graph) and power/torque (shown in
the upper graph) start early and then fade drastically to redline. Additionally
you’ll note the air fuel ratio (AFR), shown in the lower graph red trace, stays
at the stoichiometric point (14.7:1) throughout the entire RPM range which is
quite different than what you see with the Volvo HPT engines and tuned engines
as a whole. We will touch on this a
little further down.
Drop down and check out the stock boost map below then
compare it to the dyno chart above. As you can see, in factory form the boost
is programmed to build early on in the RPM range and then fade off as the RPM’s
rise, particularly after 4500 rpm. Due to the limited operating envelope of the
14T you can’t safely push this turbo far into the upper RPM’s at higher boost
pressures, so a larger turbo was in order!
It’s important to note that the stock 14T turbo that is
equipped on this 2007 XC is of the TD04L family,
not the more common TD04HL family that Volvo has used for
many years in various models. The TD04L 14T is substantially smaller on
both the compressor and turbine wheels than even the TD04HL 13T/G that was found
on earlier LPT engines. While there is a little room to gain power with just
ECU tuning and the stock 14T, this small turbo is pretty tapped out by 3500 rpm
and will only provide a moderate gain compared to what we’re used to seeing
with ECU tunes on most Volvo turbo models.
The LPT version of the 2.5L engine is robust enough, but
isn’t the strongest power plant in the Volvo line up. We had to take this into
consideration for this build, along with Ron’s particular wants and needs with
regard to what this kit would provide.
With the LPT motor in mind, we selected to use an ARD 19T
with 11 blade GTX billet compressor and 11 blade turbine was selected. We used
a 7cm^2 angle flange turbine housing mated to a Eurosport downpipe and exhaust
to help evacuate the added exhaust gas flow. Additionally, we installed a
Jet-Hot ceramic coated R manifold and ported the exhaust runners to encourage
smooth exhaust flow into the 11 blade turbine wheel. The stock 19T 12 blade turbine wheel was
sufficient for stock levels of power, but Ron was looking for a bit more midrange
and upper RPM power. We choose our 11 blade turbine wheel for its quicker
spooling and higher flow capability over the stock 19T 12 blade turbine.
The ratio of air to fuel for the most efficient burn with
the least emissions is right around 14.7 parts of air to 1 part of fuel for
gasoline. This is commonly notated as 14.7:1 AFR (Air fuel ratio), also known
as the stoichiometric ratio. While this ratio is ideal for the cleanest and
most efficient burn, it’s not always the safest. At higher boost and power
levels cylinder temperatures can increase past a safe point and fuel enrichment
is needed to help cool the combustion chamber and pistons and prevent
detonation. Detonation is very harmful to an engine and can cause engine damage
quite rapidly if left unchecked.
There are numerous enrichment strategies in the ME7 engine
management system our XC uses however; we’ll discuss the more prominent 3 here.
based on drivers input. Better put, enrichment based on throttle application.
This map is unused in most Volvo ME7.X versions except early ME7.0 and ME7.01
used from ~1999-2002. In our XC this map is inactive. Our Blue tune activates
and modifies this map to gain the enrichment AFR’s we are looking for.
based on exhaust gas temperature (EGT). Also known as ‘protection lambda’ this
strategy relies on the ECU’s calculation of combustion chamber temperature
modeled after EGT. Since the ECU measures how much fuel and air is entering the
cylinders it can calculate, quite accurately, a projected EGT and consequently
take action when it rises high enough to potentially damage the engine. This
map is active in most Volvo ME7.X versions but not in our XC’s ME7.5 ECU. Again we recurve this map to gain the
enrichment we’ll need at higher cylinder temps due to the increased temperature
and performance the engine will be experiencing.
Enrichment based on ignition degradation. Better
described as enrichment based on knock (detonation) detection. This map is a
bit of a last resort in fueling to protect the engine from damage by reducing
combustion chamber temps far enough to prevent knock. Again in our XC this map
is not active. We’ll activate this map as well but with proper timing control
and load enrichment the ECU should not have to utilize the calibrations in this
map very often.
With that said you can start to understand why the stock
dyno chart shows a 14.7:1 AFR target throughout the run. Normally proper AFR
values at higher boost and higher RPM are targeted from as low as 11.3 AFR to
as high as 12.7 AFR with 13.2 AFR having the fastest flame front I.E. best
power for a given AFR value. So the
question becomes: “Why did OE engineers spec such a lean fuel target? Wouldn’t this potentially harm the motor?”
The answer to that is
twofold. First, we need to consider the target market of the initial buyer the
factory tuned this ECU for. We need consider their driving characteristics
along with the tepid boost targets in the ECU.
You’ll find it simply doesn’t push the engine into a high enough heat
range (in most cases) to activate added enrichment. The second thing we need to
consider is the factory ignition profile in our XC. The factory ignition
profile is quite conservative, which translates to a wide margin of protection
from potential detonation or knock, so additional fueling enrichment is not as
necessary. The image below shows our
2.5l LPT engine timing map in green with a 2.5l HTP V70R timing map overlaid in
red. Interestingly there is only 2-3 degrees of timing advance difference between
the higher compression LPT engine and the lower compression HPT engine. This is
in part due to the timing advance strategy that ME7 implements where the
primary ignition maps shown below are only a starting point. From here ME7 will
quickly adapt beyond these base values to a more advanced timing setting so
long as the knock sensors are not detecting any detonation and the optimal
timing map is not exceeded.
Our first run on the newly built XC with all of our upgrade
parts and a custom ARD Blue tune resulted in a bit of boost overshoot on
initial build up (blue lines). Fine tuning to the boost control duty cycle map
and our target filling map will smooth that out and ultimately gain a few more
horsepower and ft-lbs torque. It’s interesting to note the added fuel
enrichment, as compared to the stock lack of enrichment, actually helped to net
added power. Our final gains were 78 AWHP and 122 Ft-lbs torque. Quite an
improvement in both overall power and the usable power under the curve! We’re
not 100% complete with this build so we’ll keep updates coming as we move
Robert Lucky Arnold
Post Script: There's a few questions I'm sure will be asked with regard to upgrading the LPT engine that were factory equipped with the TD04L 14T so I'll do my best to address those!
Q. Can the 14T exhaust housing be used with a larger TD04HL turbo like the 16T for instance?
A. No, unfortunately the turbine wheel inducer/exducer differences make them non interchangeable.
Q. Is the TD04HL (13T/16T) 100% plug and play?
A. Nearly, the only issue is the compressor outlet. You'll need a slightly longer coupler to connect the compressor outlet to the over the engine pipe.
Q. Is there a billet compressor wheel and matching cover that can be used to upgrade the 14T?
A. No, at this time there is not.
Q. If I install a larger turbo to my LPT engine do I need tuning?
A. It's highly recommended to retune the ECU since, even at stock boost levels, a larger turbo will put out more airflow and generate more horsepower than the stock turbo. Added fueling is the main concern.
Q. Do you have any other pictures of the build?
A. Sure do, see below!