In Part 1 of this series we looked at factory Holden and HSV tunes for the
LS1 V8. Now let’s look at Do-It-Yourself and aftermarket tuning approaches.
We spoke with one of Australia's
most experienced LS1 tuners – Sam of Sam’s Performance - to get the good oil.
Sam is knocking on the door of a 9 second pass with a naturally aspirated,
non-nitrous LS1 so it’s fair to say he knows how to make ‘em haul butt!
LS1 Tuning Mods...
Headers
A very cost-effective upgrade for the owners of early Holden LS1s is the
fitment of HSV headers. Any of the HSV headers are an upgrade over the standard
manifolds but the pair to go for are the short-length headers fitted to the latest
285kW HSV. Note that all Holden/HSV headers are interchangeable.
There’s also a wide selection of aftermarket extractors to choose from. Note,
however, if you take this approach we suggest obtaining feedback from other
customers before handing over any money. Be aware that poorly designed and built
headers can cause all sorts of tuning issues.
Exhaust
HSV cat converters (which are larger than their Holden counterparts) and
mufflers are cost-effective upgrades for anyone with a Holden LS1. But be aware
that it is possible to make good power using the standard Holden cats – Sam has
seen over 300kW at the wheels with them on his DynoLog chassis dyno.
If you’re shooting for maximum power, you should be looking at a custom
exhaust fabrication. Every performance exhaust shop you visit will have ‘their
own’ system which is claimed to work but – again – it’s best to talk with other
customers before handing over any money. You don’t want a system that causes
headache-inducing resonances.
A money-back guarantee is particularly attractive.
Air Intake
There are several air pick-up configurations and airbox designs used across
Holden and HSV models.
Sam says his preferred airbox is from the Monaro. The Monaro unit has a
single entry that can be easily enlarged, while other models use dual entries
that are more difficult to configure.
To ensure only cool air enters the airbox, it's common practice to bore a hole
through the inner guard and run a large diameter duct to the area behind the
front bumper. Where suitable, a forward-facing scop can be used to provide a
ram-air effect.
Another common air intake mod is the fitment of a smooth, high-flow ‘MAF
pipe’ – the pipe between the airflow meter and throttle. The basic Holden MAF
pipe has a convoluted section that causes turbulence and reduced airflow. This
pipe can be replaced by a smoother walled and larger diameter GTS pipe to
provide noticeably improved throttle response and power. There are also
high-flow MAF pipes available in the aftermarket - this photo shows an
aftermarket MAF pipe together with the standard part.
And what about playing tricks with the LS1 airflow meter? Ahhh, yes...
Sam says he’s seen many people ‘gut’ the honeycomb from the factory AFM. On
early model LS1s this can achieve a measurable power gain - but it’s not a very
elegant approach.
“You’ve got to know that almost everything in the factory PCM program is
related to grams per second of air passing through the airflow meter,” says
Sam.
“By modifying the airflow meter, you’re feeding the program a false signal –
in this case, a signal that causes a leaner mixture. It just happens that, yes,
you might pick up power on some cars – especially the early models that run very
rich,” says Sam.
However, by sending a falsely low load input to the PCM it will assume light
engine load and therefore give the engine plenty of ignition advance. Sam says
this is why gutted AFMs commonly cause detonation problems.
Essentially, it’s not a very nice way of going about things – not when there
are better options on your doorstep.
Intake Manifold
The intake manifold fitted to the VT Series 2 Commodore is best described as
‘compromised’ – you only need to consider it was replaced by Holden after only a
few months of service...
Sam says the VX-onward LS6 intake manifold is a direct bolt-on for a VT S2
engine and provides stronger torque all the way through the rev range. And,
although Holden’s official claim was a 5kW improvement, Sam has seen some LS1s
pick up 10kW at the flywheel (as measured on his engine dyno).
Interestingly, Sam says there’s no point upgrading to a larger throttle body
if you’re retaining the standard intake manifold. The stock LS1 manifold and
throttle is good for up to around 400kW at flywheel at the flywheel naturally
aspirated – beyond that you’ll need something like Sam’s awesome 8-throttle
set-up (see Part 3).
Engine Management
Sam says early Holden LS1s have a very basic tune – conservative ignition
timing throughout the range and very rich mixtures at high load.
“A VT2 LS1 at wide open throttle maxes out at 10.0:1 on my air-fuel meter –
and the meter’s limit is 10.0:1, so God knows how rich it’s really running,” he
says.
In contrast, VY-VYII models run at around 11.8 – 11.9:1 at full load and with
more timing across the range. These tuning changes go hand-in-hand with the
later engine’s superior intake manifold and slightly more aggressive cam
profile. Transmission shifts (which are PCM controlled) are also improved in
later-model automatic LS1s.
Given these running improvements, an easy upgrade for older models is to plug
in the PCM from a wrecked late-model Holden - but, depending on price, it might
be better to reprogram the existing PCM. Sam says the program is the same size
throughout the VTII – VZ series so there’s no problem loading a later-model tune
to your existing PCM. Sam says he’s updated plenty of VT2 LS1s with a VY
program.
Thanks to LS1 Edit software, Sam has access to around 4500 tables inside the factory PCM. Sam is also now using an editing program called HP Tuners
– HP Tuners offers a similar range of tuning flexibility but Sam says it’s more
user-friendly. Note that neither system allows real-time tuning.
So how much power can you expect with a custom retune?
Well, depending on mods, Sam says it’s not uncommon to gain around 35 - 40kW
at the wheels on a VT2 LS1 – the standard program leaves a lot of scope for
improvement. On a later model LS1, such as a VY, the gain is closer to 18 - 22kW
at the wheels.
A common step while tuning is to disable the so-called Abuse Mode of the
program. Sam tells us there’s a 350Nm calculated torque output (which is derived
from the airflow meter), at which point the PCM starts pulling out ignition
timing to protect the driveline. By merely deactivating this function Sam has
seen some cars pick up 7kW at the wheels.
Note that Sam says pretty well every LS1 tune he performs is intended for use
with high-octane unleaded. This is particularly important to be aware of given
Sam says the standard LS1 can detonate on
normal unleaded.
Tuned for high-octane unleaded, Sam runs a limit of 18 degrees ignition
timing at full noise.
“Any more than 18 degrees and it’ll ping on a hot day,” he says.
Interestingly, Sam doesn’t put a lot of faith into the standard knock sensing
system.
“The program seems to pick up light load detonation – where there’s 38 – 40
degrees of timing as standard - but not at heavy load. I mean, you can hear the
engine detonating but it’s not picking it up – it’s obviously because the
program has up to 15 degrees of knock retard and it’s not being used at all”, he
says.
If you want to go one step beyond a custom tune, Sam suggests going MAF-less
– ie ripping out the standard airflow meter and relying on a MAP sensor.
Sam says this conversion might not necessarily give much more top-end power
compared to a performance tune with an airflow meter (depending on the power
level) but the engine feels more responsive.
Sam points out that there’s no disadvantage to swapping to a MAF-less tune.
The HSV GTS relies completely on its MAP sensor and there’s no noticeable
driveability sacrifice so long as it’s been thoroughly tuned.
Note that the conversion to a MAF-less tune is not much more expensive than a
retune with an airflow meter. This is because there’s no new hardware required –
the existing MAP sensor (which is used in tandem with the airflow meter) is used
as the sole load input. All the required mapping points exist in the huge
factory program – all that’s required is a few parameter changes and the tuning
can commence.
Sam typically charges AUD$1500 for a MAF-less tune, which only AUD$400 more
than a custom tune with the airflow meter.
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Interceptors?
What does Sam think of using interceptors on the LS1 management system?
Well, he believes that interceptors have had their time – but now that there
are programs to retune the factory management they’re severely outclassed. “With
the factory program there’s just so much flexibility,” says Sam.
“For example, I can change the rev limit and I’ll soon have 200 tables to
control idle – and that’s great for running a big cam. I probably won’t use all
of those tables but it really is great to have everything from A to Z,” he says.
Note that Sam has run a HSV ute down the quarter mile in the low 10s with the
standard (but retuned) management system still in service!
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Power Tally
If you’ve got a Holden LS1 and you perform each of the mods listed above (air
intake, headers, exhaust and MAF-less tune) how much of a power gain can you
expect?
Well, the precise number depends on the base vehicle, type of transmission
and the specific components used but it’s typical for a VY SS to climb from
around 180 to 225kW at the wheels – a gain of 25 percent. Expect slightly less
in VT2s retaining the original intake manifold and conservative cam profile.
Stick around for Part 3 – the final. It’s time we looked at making some big power!
Contact:
Sam’s Performance
+61 2 9772 3105
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