- Fitting an aftermarket cam to your LS engine is one of the easiest and most cost effective ways
of seeing huge improvements in power and torque, not to mention getting that lumpy
cam idle.
However, more often than not I hear horror stories about cam upgrades where the engine really didn't
deliver the power and torque that the cam was capable of.
Or alternatively cars that stall every time that you come to a stop.
In this video, we're going to talk about 5 easy mistakes that you can avoid if you're
contemplating a cam upgrade in your LS.
The number one problem is simply choosing the wrong camshaft for your engine.
While it can be tempting to scroll straight to the bottom of the list of cams offered by your
manufacturer of choice, choosing the biggest lumpiest cam that they make for your engine,
this more often than not is going to result in disappointment.
The reason for this is twofold, first of all the cam specs will have a big impact on not only
the power and torque that the engine will provide but particularly and more importanty
for a street car, it'll also affect the drivability of the cam as well as your fuel economy.
This is something that we do need to keep in mind.
The other aspect with the larger cam offerings is that in order to provide the sort of power
and torque that the cam is capable of, this will almost certainly require some other
hardware modifications to your engine.
You're most likely going to need to fit aftermarket cylinder heads that can support
more airflow at high RPM to see the sort of potential the cam can actually deliver.
While choosing a cam like this might make a lot of sense for a dedicated racecar that's only
going to be operating at high RPM, particularly for a street car, you're almost always going to
get a better overall result if you sacrifice a little bit of top end power and get a broader
power and torque curve, this is going to make the car much more drivable and
user friendly on the street.
When you are choosing a cam, you also need to consider the supporting parts
that go along with that camshaft.
The cam manufacturer will be able to advise here but it's really important not to overlook
upgraded valve springs, maybe double row timing chains for the larger more
aggressive cam grinds and usually we're also going to need a vernier adjustable
cam gear or timing set so you can actually adjust and time the camshaft to the
manufacturer's recommendations.
Speaking of cam timing, this is the second mistake that you should be aiming to avoid.
Or more specifically getting the cam timing wrong.
A lot of people, when they are fitting an aftermarket camshaft to an LS engine will
simply install the timing gear a the zero mark and assume that everything's going to be
just fine.
Well unfortunately this is a very expensive gamble to be making.
At best, you're likely to find that the cam timing won't be set up to the manufacturer's
recommendations and this can end up costing us power and torque.
At worst we could end up with very costly damage as a result of valve to piston contact so it's
really critical to make sure that the cam is timed up correctly.
This is something that's going to add a little bit of time and potentially a little bit of cost
to your camshaft installation but when its done, you can be assured that you're going to get all
of the potential that the camshaft can offer and you're going to have confidence you're
not going to have an expensive engine failure as a result of your camshaft upgrade.
The third mistake you're going to want to avoid is not having the required supporting modifications
in place on your engine so that you're really going to see the potential that your camshaft
can offer.
This should go without saying and there's probably not a lot of people that are going
to fit an aftermarket camshaft as their very first modification on an otherwise stock engine
but it is important to consider airflow in and out of the engine in order to allow the cam to deliver
the additional power and torque at higher RPM.
What I mean here is we're going to normally need a freer flowing intake and we're also
going to probably want to fit a set of headers and a larger freer flowing exhaust system.
Here we're simply trying to optimise the airflow in and out of the engine so that
the cam can deliver the sort of power and torque that the manufacturer is claiming.
The next two problems you're going to want to avoid both revolve around idle
control and this is one of the most common mistakes I see people making when they're
fitting aftermarket cams to their LS engine.
One of the key issues here is trying to make the engine idle too low.
While a stock camshaft will quite happily idle around 550 RPM in an LS engine, if you're
going to fit a large cam with a lot more duration, a lot more lift and a lot more overlap, that's
simply not going to be the case.
So for a start we're going to need to choose a suitable idle speed so that the cam has
some chance of idling properly.
There's a lot of tables inside of the factory engine control module that will
need adjusting in order to get these results so let's jump into the car now,
we'll have a look through the HP Tuners software and see what's relevant and what
needs to be adjusted.
We're in our tuning software here and we're going to start by looking at our idle targets.
Now at the moment I've got the calibration for our cam tune overlaid with a compare
file which is the stock calibration.
Let's start by looking at our idle targets and we're on our idle tab here and to the
left we've got our RPM tab.
And the table that we're really interested in at this point is our base set point so let's
click on that.
We'll actually start by looking at the values from our base or factor calibration for the
stock cam.
We can see that we've got a table here that has our engine coolant temperature on the
horizontal axis.
This is important because it allows us to vary our idle target depending on the
coolant temperature.
We're going to want to set a higher idle target when the engine is cold compared to at
operating temperature.
We've also got the ability here to vary our idle speed depending whether the engine is running
in gear or whether it's in park and neutral.
Interestingly even in the stock calibration we can see no variation in our idle targets.
Now if we look at the idle target down perhaps 8-20°C we can see that we're
targeting 850 RPM.
But up at the normal operating temperature, up around 90°C, we can see that's dropped down
to 550 as I previously mentioned, so that's our stock calibration.
Let's have a look at what we've done with these idle targets to suit our larger cam.
Now in this case we've got a Kelford Cams HS108D cam fitted to the engine.
This gives us a duration of 236° on the intake and 242° on the exhaust so definitely not
the biggest cam that ever has been fitted to an LS but it's definitely a large cam,
particularly for a street driven car.
On top of that we've got 630 thou lift on the inlet and 610 thou lift on the exhaust
so definitely a reasonable sized cam.
We can see straight away that up in the normal operating temperature we've
lifted the target idle speed by 300 RPM, we're up to 850.
Down when the engine is cold, we're up at 1000.
This does need to be managed carefully.
Ideally what we want to do is choose the lowest RPM that we can get the engine to
comfortably idle at.
The reason for this is particularly with an automatic transmission, if we raise the
idle speed we're going to end up with the car wanting to push or drive forward
when the car is in gear.
And this can be a little bit disconcerting, it's going to require us to hold our foot
fairly firmly on the brakes so this does require a little bit of testing.
I know for our HS108D cam, 850 RPM hot does give a really good idle quality.
But the car will definitely push so it's something that does require a little bit
of experimentation with but if we are trying to make the engine ide too low,
the cam is just not going to work well down at low RPM and you're just going to end up
wasting a lot of time and causing a lot of frustration trying to get the engine
to idle at an RPM where it simply won't.
Just raising the idle speed targets unfortunately doesn't fix all of our idle control problems
and we're likely if we just make that one change, to still find that the engine will
stall when we first start it and it's going to stall when we come to a stop.
What we really need to do is reconfigure the base position for our idle speed control.
In the case of our LS2 or L98 engine as it actually is, this is a drive by wire throttle
engine so the idle speed control is adjusted by actually opening and closing the throttle
butterfly and there are a few aspects that we need to keep in mind here.
The first of these we're going to have a look at here is this table here which is our
base running airflow.
It's labelled as idle airflow.
We'll open this table and what this does is it gives us essentially a starting point
for our idle speed control circuit.
This table defines relative to our engine coolant temperature and also relative
to whether the automatic transmission is in gear or whether it's in park or neutral.
What the airflow required for a specific idle speed is.
So we can see that particularly as we move through this table and the engine goes from
cold running conditions to hot running conditions, we see that the idle airflow does
decrease.
Now what we're going to need to do is adjust the values in this table, going to almost certainly
need to make a significant increase to these values in order to get enough idle airflow
to satisfy our new higher target idle speed.
There's a little bit of work that goes into this, we can also use the VCM scanner software
and create a histogram where we can basically monitor what the actual airflow at idle is
as the engine warms up and we can use this to help us populate this particular table
but getting this right is one of the keys to getting good solid stable idle speed
control regardless of the engine's operating conditions and operating temperature.
Lastly, the 5th and final aspect that you're going to want to avoid if you're fitting an
aftermarket cam to your LS engine is drilling a hole through the butterfly.
This is something that I see so many tuners doing and fortunately it's really easy to avoid.
This is a problem we see with the drive by wire throttle engines and the reason that
this is done is that if we don't make the required modifications to our calibration,
we're going to find that particularly when the engine is cold, the throttle body just
simply won't open far enough to allow the engine to idle at the correct or target
idle sped.
This results in stalling, particularly when the engine is cold.
Even if we can get the engine to idle, we're going to find that the engine idle
speed will be way lower than we really need it to be.
So how does this work and why are tuners out there drilling holes through
butterflies in the first place?
Well with the drive by wire throttle there is a limit to the maximum throttle opening
that will be allowed during idle speed control.
Let's have a quick look into one of our tables here and at the moment we are
on our airflow tab under idle speed control and we have a set of parameters
here which are called effective area.
And what we're looking at specifically is this value here which is listed as percentage max.
Now this defines the maximum throttle opening that can be used during idle speed control
and if we mouse over it we'll actually find down the bottom we do get a bit of a description
saying maximum percent throttle area from idle.
And you can see I've got a value there of 5% right now.
In the stock calibration this was set to 1.9% so again this artificially limits the amount of
maximum throttle opening we can get.
Now we can't just go and set this to any number we want.
By going too large with this value we're going to end up getting lower resolution for the
idle speed control and that in and of itself can cause problems.
For this particular cam we've found a value of 5% works but this just allows a little bit more
throttle opening compared to the stock calibration, fixes that problem, allowing good
idle speed control when the engine is cold even with a large cam.
There are a range of other problems that drilling holes through the throttle butterfly
introduces because then the engine control module really doesn't have a good handle
on the airflow into the engine.
Basically it's got extra air bypassing the throttle butterfly that it doesn't know about and this
again causes a range of other knock on issues with drivability, there is no reason to drill
holes through your butterfly if you understand the correct changes to make in your calibration.
Which leads me to a solution if you are looking to tune your own LS engine with a cam, particularly
on the HP Tuners platform, we have a big cam worked example in our Practical Reflash Tuning
course that's going to be perfect for you, takes you through the complete process,
start to finish of the tuning process.
Let's have a quick look at that course and I'll show you what's included.
While in this video I have been focusing on GM reflashing using HP Tuners as
the software platform, our Practical Reflash Tuning course which includes our LS big
cam tuning worked example, is actually a generic course and it's applicable regardless what type
of engine you are tuning and regardless what type of software platform you're using
for making your tuning changes.
Let's dive into it here.
And we start by covering some of the basics of reflashing which you're
going to need to understand if you want to get the best possible results, we'll talk
about what reflashing is, how this varies from tuning an aftermarket standalone ECU.
We'll talk about live tuning vs reflashing because often when we are reflashing,
we won't be able to make tuning changes live or in real time while the engine is running.
We'll talk about the required hardware and software, some of the precautions
that you should be keeping in mind when you are reflashing, we'll also talk about
how reflashing will affect your factory warranty.
There's a few aspects here you need to understand before diving into tuning,
particularly if you've got a car that is still covered by a factory warranty.
We also cover open source vs commercial tuning packages and how those differ.
Moving down, we also talk about some of the operating principles of the factory engine
control module.
This differs particularly from how we tune in the aftermarket standalone world.
So we talk about MAF based ECUs vs speed density based ECUs and how load measurement
is done.
We then move into some of our basic tuning strategies here including data logging.
This is essential to get the best possible results when we are reflashing, again this
comes down to the fact that more often than not we can't make our tuning changes
live so we're really relying on data and our data logger while the engine is running.
We talk about fuel delivery here and how to adjust our ignition timing.
We then move into some of the more advanced tuning topics here such as
MAF rescaling, injector rescaling, so how to adjust your calibration if you're fitting
larger injectors.
Talk about speed density conversion, boost control and a few other aspects in there
as well.
Next we move into our 6 step tuning process and this is a generic process you can apply
irrespective of your tuning job.
This takes the guess work out of reflashing and I know particularly for novices it can
be a little bit confusing knowing what to do first and what order to progress in.
By following that 6 step process, each of the individual steps is quick and easy to complete
in no time you've got to the end, you've got a completely tuned engine delivering great
power, great torque and most importantly great reliability.
We've also got a set of modules within this course that cover the process of tuning
out on the road or the racetrack if you don't have access to a dyno.
And fortunately when it comes to reflashing, we're actually in a pretty good position to
get great results, even if we don't have access to a dyno.
Yes the dyno is the best place to perform your tuning but we know that we've got customers
that come from cities and sometimes even entire countries where there are no dynos.
In this case, obviously you've got no option so we'll teach you how to get the best
results out on the road or the racetrack.
Up to this point the course has been generic, it's applicable to any engine and any reflashing
package however, now we move into our library of worked examples which is where
we get a little bit more specific.
Here we tune a specific engine and we use a specific software package to give
you experience on a wide range of different platforms.
However for this video we're really interested in the HP Tuners platform and our big cam
tuning and that is this particular worked example right here.
Again you can watch each of those individual steps from start to finish.
Seeing exactly the process and the changes that are require to get the best possible results
out of a cam upgrade on the LS engine.
If you want to learn more about this course and enrol, click the link.