Where to from here?.......
So, we can see what's going with our engine and transmission, we helped out engine breath easier, we helped it evacuate
the spent gasses better, so now we're ready to start adding power, right?
Transmissions and clutches:
Before we start throwing a bunch of HP and torque to the ground,
we need to GET it to the ground, so keep this in mind. Your stock automatic 47 or 48 series transmission can only handle about
40 HP over stock before the OEM torque converter starts to slip. This generates heat and shortens your transmissions life.
Not only that, but if you have added performance modules, programmers, big injectors, etc., you aren't putting the power to
the ground due to this slippage. All your extra HP and torque is doing is generating heat as your TC and clutch packs slip
under the increased power.
The stock TC has limits of approx 360 HP and 700 lb/ft of torque. Beyond
this, it simple cannot cope with the power. Most aftermarket TC's are rated for over twice, and up to nearly triple, this
power level. For torque converters and valve bodies, Doghouse Diesel Performance recommends SunCoast Converters and Goerend
Now you manual guys aren't much better off. Start exceeding 60 - 90 extra HP and
your OEM clutch is gonna give way also. The good thing you have going for you is that, for the most part, the manual transmissions
in our trucks are pretty bullet proof, other than the clutch.
The stock clutch behind your Cummins
has limits of approx 400 HP and 800 lb/ft ot torque. Some of the aftermarket clutches available are rated for up to 2000 lbs
of torque. Picking the right one for you is critical, as some of them can be very grabby and require excessive pedal
pressure to disengage the clutch. Picking the right clutch will make your driving experience much more enjoyable. South Bend
and Valair and two good manufacturers to look at when considering a clutch upgrade.
So what do
we need to do?
Automatic transmission owners, you have a little work cut out for you. You need
a MINIMUM of three things here. A good triple disk torque converter, a good valve body and if you intend to tow heavy or occasionally
drag race, a billet input shaft. These three items will help keep a good majority of your transmission woes at bay.
Manual transmission owners, you have it a little easier. You can get away with a new clutch (possibly a flywheel
for some applications), a billet input shaft and possibly upgraded hydraulics. With those three items, you're getting ready
to handle some power.
NOW we can start adding some power. This
comes in all sorts of forms; mechanical, electrical and even chemical. What your intend to use your truck for is gonna be
the main decision maker here. Give us a call and we'll help you make a good decision for where you see yourself
taking your truck in the future.
Your stock turbocharger, when applied to a stock Cummins engine is very good. But, like other stock
components, it has its limitations. It is really only efficient up to approx 32 psi of boost. This works fine under MOST stock conditions
as, depending on model year of your Cummins, it’s wastegated at approx 18 - 26 psi of max boost. Beyond 32 psi, all
it’s really doing is heating up the air due to it being outside the efficiency map of the compressor. Upgrading your turbo is one of
THE best ways to control EGT’s and GREATLY improve the performance of your engine.
Now, with the understanding that you
want to try and keep your engine operating at a maximum SUSTAINED exhaust temperature of 1250* or less and the fact that you
can effectively cool your exhaust temps by approx 10* for every pound of boost, you can see where an aftermarket turbocharger
comes into play. Some of the aftermarket turbochargers that are of the same size as your OEM turbo are efficient at ranges
up to 60 psi and have much higher lbs/min ratings than your stock turbo.
Bigger is not always better when it comes to upgrading your turbo. A very large turbo will certainly help keep EGT’s
down, but the lag and lack of response at low RPM’s can make it perform poorly in day to day driving. Picking the right
size turbo for the power range that you are looking for is very important to getting good power, response AND good drivability.
Go too big and you’ll have a hard time getting it spooled. Go too small and you won’t be able to effectively control
Below are some recommended turbo sizes for desired power capabilities. For a daily driven truck that doesn’t tow
often, look at the lower numbers in the range. For trucks that tow often, look in the middle of the range. If you use your
truck as weekend warrior / occasional drag racer or sled puller, look at the high side of the ranges.
Up to 300 HP, the stock turbo is fine,
but upgrading to a 57mm will help greatly.
400 HP, look at 57 – 62mm’s
500 HP, look at 60 – 64mm’s
600 HP, look at 64
– 66mm’s (This is where we start to recommend compounds on daily driven or towing applications)
700 HP, look at 66
– 71mm’s (compounds are recommended)
800 HP, look at 74 - 80mm’s (compounds are recommended)
Over these HP ranges, you're looking at applications that are highly customized.
Aside from your turbo, your intercooler is the next item that helps keep the
EGT's in check. Like everything else we've discussed so far, it has it's limits. The intercoolers on some of the 3rd Gen trucks
(03 - 05 models) are most in need of an intercooler upgrade. The end tanks on these intercooler are plastic and prone to failure
as boost pressures increase.
Larger intercoolers, with higher
fin counts, wider and deeper cores, larger end tanks, larger inlets and outlets and heavy duty aluminum construction can help
lower your intake charge as it comes out of your turbo by as much as 300*. This can translate into a 150* drop in EGT's.
Intercoolers are a very easy swap and can be done in less than an hour.
In order to provide enough fuel to get these turbos spinning, we’ll look
at fuel system and injector upgrades next.
With upgraded power comes higher fuel demands. If you start exceeding 100 - 120 HP over stock, you are
probably exceeding the capabilities of your OEM lift pump. This is a critical piece for you VP44 guys, less so for CP3 owners.
Both of these pumps are cooled and lubricated by the fuel, so you can see why a lack of pressure or volume can be extremely
detrimental to it's longevity. A good fuel pump (AirDog or Raptor) will go a long way in keeping those
big injectors and hot tunes fed and your EXPENSIVE injection pump happy.
Dodge addressed one of
the problems with the lift pump when they moved it from the engine mounted pump to the in-tank pump that is currently
used. The in-tank pump is much less likely to fail then the engine mounted pump was, but it still falls short when you start
demanding greater than stock fuel flow.
For stock and lightly modified applications, an AirDog
or Raptor 100 are a good choice to help increase fuel flow, remove air from the fuel and provide increased filtration. These
pumps are available with 2 micron fuel filters, which greatly exceeds the required 7 micron rating that the factory filter
For higher HP applications or if you think you'll do more upgrades in the future, we suggest
going with an AirDog 165 or Raptor 150. Both of these pumps are capable of supporting all but the highest fuel demands, offer
increased filtration, air removal and have life time warranties on the pumps. Filters are widely available and have a much
longer service life than the OEM filters. These 150+ GPH pumps both provide approx 17 psi of pressure for your VP44 and CP3
powered trucks, which is perfect to keep them supplied and lubricated.
Injectors and Injection
Now that we've upgraded our fuel system, we can address the injection of that fuel. This is where our
injection pump comes into play.
The VP44 (98.5 - 02) and CP3 (03+) pumps take the low pressure
(17 psi) fuel from your lift pump (hopefully a FASS or AirDog by now) and turn it into the high pressure (up to 23,000
psi) fuel that is needed for efficient combustion in your engine. These pumps differ slightly in operation.
The older VP44 controls everything to do with the injection. It does the injection timing, duration and creates the
pressure. All of this is done based on the demands from the ECM.
The CP3 has an easier job. All
it is responsible for is creating pressure. The injection timing and duration of the injection pulse is controlled electronically
by the computer by way of signals sent to the individual injectors.
There are several options
for upgrading your injection pump. These range from a bag of parts to highly modified single pumps to dual pumps for high
Lets talk about injectors...
Your injectors are the
final critical piece in your injection system. They need to matched correctly for not only the application that you have intended,
but also to the turbo you intend to use. Small injectors and large turbos equal poor power and lots of turbo lag. Large injectors
and small turbos equal lots of smoke and extremely high EGT's. Getting the correct mix is critical.
range in size from 25HP to 200HP from most of the major manufacturers. Custom sizes are available and can be created by most
So how do we know we are getting the most power but not overloading our turbo? Look at
your exhaust when you are at wide open throttle. If there is no smoke at all, you can go with bigger injectors. If you are
pouring out black smoke, you don't have enough turbo. If you can get to where you have just a barely visible haze at WOT,
you are getting all the power that your setup can produce. Remember, lots of black smoke it just HP going out the tail pipe.
For the average daily driven truck that runs a stock turbo, you can get away with running up to 25HP to 50HP larger
injectors, as long as you don't tow heavy (i.e. 10K lbs or more). For a little more power with a slightly larger turbo, you
can look at 75 - 90 HP injectors. For bracket racers or occasion sled pullers that are using 62 - 64mm turbos, 100 - 120 HP
injectors work well. For higher HP trucks with large singles or compound turbos that don't tow often (and when they do it's
less than 10K lbs), 150+ HP injectors are the ticket.
Other mechanical upgrades to consider:
After this, we suggest you look at some mechanical upgrades. Two things to look at here; valve springs
and head studs. There are some options on these and we can help you decide if you need them or not. A good rule of thumb is
that if you are making more than 48 psi of boost, you need head studs and heavier valve springs.
stock head bolts can be replaced with much stronger studs. These studs will allow you to get your engine up into the 60+ psi
range without worrying about head gasket failure. If you are upgrading to a bigger turbo, these should also be purchased at
the same time.
Along with the head bolts, your stock valve springs need to be replaced as your
boost levels increase. The stock springs only have approximately 60 lbs of seat pressure, so as you approach this in boost
pressure you can slow down how quickly the valves react. Once you get to around 52 psi, you can actually blow the valves open
and this can cause valve / piston contact resulting in MAJOR damage. Upgrading to a stiffer set of valve springs will not
only allow you to run more boost, but also allow you to exceed the factory RPM limit of 3200 and push your engine up to 4000
RPM's without worry of engine damage.
From here, we can have some fun. So if you want to take
your truck a little further, give us a call so we can discuss some plans and get you on the right path so you're only buying
Remember, BUY THE PART YOU WANT THE FIRST TIME! Otherwise, you'll just spend more
to get it later.