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This
Dart-based, Lunati-filled, Racer Pro-topped powerhouse boasts a Vortech
V4Z supercharger and a Mondo air/water aftercooler. All up, when testing
was stopped at 7000rpm (boost had become too high at 30lbs/in2) there was about
1100hp on tap. |
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Super Camaro, Air/liquid
intercooled beast.
Start small and work your way up doesn't seem to be a concept Michael
understands. You see, this is his first project car ever, and it's not a bad
start. Originally, he had in mind a stroker making around six or seven hundred
horsepower - until he saw a rotary with plates that read "EATAV8" and,
he says, thought, "No, that can't be allowed." It was even more
annoying because the owner had a big mouth and was a mate's mate so he couldn't
get away from him.
That's when he decided 1000hp was going to be the minimum figure for the
project, and a supercharger seemed like a good way of achieving it. Then he
figured, as long as he was going to be spending the sort of money this was all
going to cost, he should have a go at the Horsepower Heroes at the Summernats.
At first, Mike had taken the standard car to McDonald Bros Racing just to get a
decent tune because it was running so badly when he got it. He chose McDonald
Bros because they'd built an 11-second engine for a friend on a budget and it
performed very reliably.
He liked the racing work they did and the reputation they had so he decided to
get them to fit a roll-cage and tubs. He paid his deposit and, as Mike and the
boys at Ray's got talking, things got out of hand. That, along with the factors
just mentioned, was a contributing factor in deciding what the power figure
should be and how to achieve it.
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Left: Copper gaskets and o-rings seal the bores and did a good job despite the
fact that they went 10lbs/in2 over the intended figure.
Left:
The blow-off valve empties the inlet tract when the throttle is shut
abruptly at high revs and high boost levels. We have more about Vortech
Superchargers elsewhere in this issue. |
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HOT FAVOURITES
Of course, superchargers heat air so an intercooler was going to be needed. This
was particularly important because of the dyno competition at the Summernats.
Mike noted that the event is always held during extremely hot weather and
conditions around the dyno are usually crowded and even hotter, so an air/air
intercooler didn't seem like the best way to go.
An air/water intercooler, on the other hand, can absorb huge amounts of heat and
seemed like a good idea. He'd been talking to Tony Rullo at C.A.P.A about the
supercharger and Tony suggested a Vortech Mondo air/water intercooler would be
the thing to use, particularly because no one in Australia had fitted one
before.
The mondo looked good because Vortech said it's capable of supporting a 1700hp
setup. As company literature says, some drag race teams don't use a
recirculating fluid circuit incorporating a radiator with the mondo - they
simply run a small supply of iced water through the unit for the very short
duration of the race.
To get things really cool, Michael is currently wondering how you'd go about
using liquid nitrogen as the cooling medium. This, of course, is just an idea at
the moment. It would certainly keep temperatures low, but questions like what
sort of pump to use and other technicalities would have to be solved.
Eventually, Michael wants to fit nitrous oxide.
The project as it stands at the moment has been a collaborative effort. Lee
Kavanagh brought in the Dart 4 block and Lunati stroker kit. Duggans prepared it
and the associated components. Graeme Cerini at Total Performance chose the
Racer Pro heads and ported and prepared them. Crow Cams were advised of the
objectives for the project and supplied an appropriate cam and, of course,
C.A.P.A supplied the supercharger and cooler.
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A Lunati stroker kit gives the cubic displacement needed to take the
output of the V4Z supercharger. |
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SHORT DETAILS
Warren Duggan explained that the block arrived with most things,
like align-honing the mains, already done.
However, the bores had to be prepared and, as you'd expect, boring and honing
were carried out with a torque plate attached. There are no real surprises in
any of this and clearances were set to usual specs of around 0.0025"
through the mains and rods. Piston-to-bore clearances were set to kit
recommendations plus about another 0.001" to accommodate the expansion the
extra heat was likely to create.
Compression is about 8:1 and, because the pistons had to have such a large dish
to accommodate it, Warren was worried that at 0.200" the crowns were going
to be too thin for the operating conditions. As a precaution, the combustion
faces were ceramic coated by Competition Coatings to help keep the heat out and
prevent the crown going soft and collapsing. As it turned out, Warren's concerns
were justified - almost. More on that in a minute.
Copper gaskets are another aspect to handling the heat involved. Although some
people don't have that much luck with them, Warren says they work fine if used
correctly. Using the right sealant is essential, but just as important is the
amount applied. It's definitely a matter of more is worse. Just a light coating
of ThreeBond white silicon around the holes on either side of the gasket is all
that's needed.
An o-ringed block is the other requirement for getting them to work at their
best in this sort of application. However, it's essential to have the o-rings
sitting above the deck by the correct amount or this technique doesn't work
effectively either. Warren says about 0.010" protrusion works best.
Nothing much else out of the ordinary was done except that the combination of
block, heads, cam and rockers called for a bit of die-grinder modification to
the pushrod holes in the heads, but things like that are expected in a highly
customised setup like this.
The rods needed a bit of attention because the cut-outs in the big-ends weren't
quite deep enough for the bearings to seat properly. This would make it
impossible to obtain an accurate measurement across the bearing and could cause
failure due to inadequate heat transfer.
Problems like this pop up from time to time but that's what pre-assembly
checking is all about. Warren says that the other day, on another engine, he
found that the notches for the tangs were too narrow. Any sort of quality engine
build should include thorough pre-assembly as part of the process to catch
things like this before everything gets tightened up.
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A custom manifold had to be fabricated to take the
aftercooler. The Mondo Cooler features a triple-core, double pass system that
can pass up to 2500cfm. That's enough for around 1700hp. |
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NOT MUCH NEEDED
We also spoke to Graeme Cerini about the heads. He points out
that these 18° Racer Pro units are good straight out of the box and don't need
much work for excellent results.
Inlet port volume is 250cc and a bit of bowl-work and a general clean-up in
combination with widened short-turns on the inlets sees them right. However, in
this application, because of the supercharger, flow through the exhausts was
lifted to about 75-80 per cent of the inlets whereas 65-70 per cent is the usual
figure. Graeme says the preparations described are all that's needed as long as
the cuts for the seats are all of the appropriate size and where they should be.
On that matter, the top-cuts were 30°, the seats 0.050", the 60° cuts
0.100" and a 75° cut blending all that work into the bowl. Valves are
2.150" and 1.625" with Comp Cams springs, titanium retainers and 10°
collets. As just about always, Graeme polished the chambers too (although they
don't shine like the iron units).
Finally, the whole package was assembled and ready to go. Chris from McDonald
Bros says it was all run in and happy about 20 minutes after they got it bolted
in to the dyno. Lovely.
They started mapping the Autronic and things were going well until about 4500rpm
when it started to carry on a bit like it was misfiring. Initially they thought
it electrical, but then looking at the computer screen showed the injectors were
running at 95 per cent and running out of fuel. The top two injectors in the
manifold were set to come in on 100 per cent at about 3000rpm and that got the
whole thing to 5000rpm before it ran out of fuel.
A set of Indy Blue injectors were fitted and it ran straight to 6500 on the
first pull, sounding clean all the way and making about 950lbs/ft and 1090hp.
Once that figure was established it was re-mapped everywhere else.
On the last day they did eight runs and managed 1150hp on the final run at
6800rpm with 30lbs/in2 boost. Earlier, at about 4000rpm, they only had about
12lbs/in2 and thought there wouldn't be enough because they only planned to turn
it 2500rpm faster than that, Chris says that between 4500 and 5500rpm another
13lbs/in2 appeared.
Originally, they'd never intended to go past 20lbs/in2, so the intention is to
fit a smaller pulley (on the crank) to slow the supercharger down a bit. This
will allow them to rev the engine harder for a higher top-end figure while
maintaining a sensible pressure ratio (see our turbocharger article), although
the supercharger is rated to 35lbs/in2.
The high boost was all a bit stressful on the various components and Warren
Duggan's concern about piston crown thickness was justified. Chris says that
when they pulled it down, the areas around the fly-cuts for the valves showed
signs of starting to soften. The gasket was also starting to show signs of
movement in a couple of places. On the other hand, the bearings looked brand
new, like the engine hadn't been started.
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Far
Left: Before...
Left: ...after. It took a reasonable amount of wriggling but it went
in quite easily. There'd certainly have been some tears if
modifications to the tower hadn't been accurate. |
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WHEN THE'RE RIGHT THEY'RE RIGHT
We looked at some of Vortech's technical
information relating to the Mondo cooler and they make the point that,
technically speaking, this is really an aftercooler, along with virtually
everything else described as an intercooler in automotive applications.
An intercooler, they point out, is a heat exchanger positioned between two
compressors in a two-stage pressurised setup. I hate it when I find out things
like that. The world isn't going to change and now, every time I yield to
popularism and write intercooler, I'm going to twitch.
In any case, the a-f-t-e-r-c-o-o-l-e-r worked well and inlet temperature stayed
around 30-35°C until they gave it a serve and temperatures jumped up to about
45° at 7000rpm.
Apart from the tremendous amount of heat an air/water aftercooler can absorb,
the other advantage is that these units can be positioned right at the engine
because they don't rely (directly) on airflow to remove the accumulated heat.
This results in reduced flow loss compared to that seen in some air/air
applications with convoluted ducting. Vortech summarises the advantage by
stating that their air/water aftercoolers take the "cool to the inlet
charge" rather than the "inlet charge to the cool". Sounds cool
to us.
Story and Photos by Paul Tuzson
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