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Holden V6s with Leon Vincenzi

We tap into the mind of one of Australia's best Holden tuners to give you the ins-and-outs of the local 3.8-litre V6...

By Michael Knowling

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Who is Leon Vincenzi of Awesome Automotive?

After completing an electrical fitter apprenticeship and working as an industrial electrician for about 9 years, Leon started his own business working on cars; he'd already done engines, gearboxes, diffs, paint, panel, interior and fabrication work on his own vehicles. At first, Leon ran a successful crash repair and spray-painting business, then about 5-6 years later he took yet another turn. Having already branched out into installing exhaust systems, he happened to build an engine for a bloke - and that turned out a "real winner." The next thing he knew, he was building engine after engine...

That's when he opened up Awesome Automotive. The workshop is equipped with a good collection of fabrication equipment and - perhaps more importantly - a Dyno Dynamics chassis dyno. Leon guesses that he's dyno'd over 1000 cars - about 60 percent being Holden ECU re-maps. Mr Vincenzi is not your average chip cooker, however. Using the fantastic Kalmaker software system, Leon can access, recognise and change every seemingly insignificant part of the factory Holden management system. Through experience, he now knows Holden's mapping absolutely backwards - perhaps only behind Holden's software engineers in this regard.

Okay, so there's the background, here's what Leon has to say about Holden V6s....


First of all, how much power does a stock Holden Commodore V6 produce on the rollers of your Dyno Dynamics chassis dyno?

In my experience, an early (VN to VR) Commodore V6 puts out about 125 horsepower at the wheels, and the later ones (VS-on) average about 132hp. Having said that, I've measured them from 112hp right up to 135hp; bog stock, untouched. And, as a guide, I'd say there's a 20-24 percent drivetrain loss in a manual and around 30 percent in an auto.

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Why is there such a huge power variation from car to car?

Well, the timing chain in the V6 is a piece of crap, so you can often end up with retarded cam timing. This knocks power on the head a bit - but it's a problem that can be fixed. You can buy an aftermarket replacement that's a lot stronger.

In my experience, the valve guides also thrash out in them - and I've had Holden V8s with same sort of problem. Of course, as soon as your guides go, you've got no valve sealing and you drop power. I have been told - I don't know if it's true or not - that Holden had problems with the hardness of their guide metal - they just run the valve straight in the head, with no bronze guides.

The standard knock sensing is pretty sensitive too. It can get triggered (causing retarded ignition timing) once the engine's done a few kays and so there's a bit of timing chain and balance shaft gear noise.

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What running changes have been made to the V6 engine?

There were mild changes in compression - from about 8.5 to 9 to 1. Holden changed the chamber volumes pretty early in the piece and dropped the deck height in the VS. The V6 bottom-ends are pretty good for a standard car - but once they get over about 160,000-180,000 kays, you've gotta think about doing a freshen-up on them.

The heads were also changed from a rectangular port to a round port in the VS. We haven't flow tested them here, but the rectangular ones can be ported to give substantial increases - that's what they use in Formula Brabhams. The cams have improved all the way through. Once you start getting into VS, I think they're a bit more aggressive - the exhaust profiles change quite a bit compared to VN.

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There's nothing really wrong with the VN-VR intake manifold as far as I'm concerned. But the VS-on have a removable lid on top that let you look inside. You can see problems in those manifolds - especially ones with a few kays. There will be a couple of trumpets that are clean and a couple that are black as anything - so your getting fuel reversion out of some. And you can't tell me reversion is a good thing... Throttle body diameter stayed the same the whole way through - 65mm.

There was a big improvement in the VS exhaust manifold, when they went to a tubular style manifold. The earlier ones were just cast iron - and the used to crack. They're not interchangeable, unfortunately.

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What sort of engine management changes occurred over this time?

All Holden V6s run multi-point injection, but - on the induction side of things - the VN to VR V6 Commodores ran a MAP load sensor, while the VS onward uses an airflow meter.

Basic 16k ECU programs were used in the VN to VP - both manuals and autos. VR manuals stepped up to a 32k program, while the auto version got a 64k program. The 64k program is actually a full PCM (powertrain control module), which also controls the VR's full-electronic 4-speed auto and torque converter. A big difference is the basic 16k ECU on VN-VPs has one-way diagnostics, while the VRs use two-way. This enables the technician - or whoever's doing the diagnostic - to force certain functions. The VR program also had revised closed-loop oxygen sensor data and was the first Commodore to use what's called lean cruise. It was all targeted at improved economy and emissions.

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The VS computer is a new design again. It runs sequential fuel injection, an airflow meter and the programs - for auto and manual - are all 128k. They're simply using a PCM in both the manual and auto. VT-on software is essentially the same as VS - the only real difference is that the 3-2 downshift solenoid is pulse width modulated. I think that's just to do with smoothness in the shifts.

All of the V6 Commodores use Memcals. A Memcal is a removable UV-light erasable chip; so - basically - you switch on a high-intensity UV light to blank it and then you burn your program in. Interestingly, there have been a fair few different factory tunes devised for each model car. There are no Memcal number patterns to go by, but - generally - the latest tune-up software is best. They've had more time to refine it.

What sort of air-fuel ratios and ignition timing maps do the stock programs contain?

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The VN to VRs give about 12 to 12.5 to 1 air/fuel ratio at wide-open throttle pretty well all the way through the rev range. They run a little bit leaner straight off the bat - maybe about 13.5. Ignition timing is set to around 22 degrees BTDC at full noise. The first ignition programs were pretty lame, but they picked up a bit by the VP. Actually, VNs weren't that bad, but they really used the knock sensor more in the VP, so its ignition mapping was more aggressive. All Holden V6s have a knock sensing system, which works fairly well. Early systems started off pulling out up to 8 degrees of timing, and the VT is capable of 12 degrees.

Given the sensitivity of the knock sensor, are there any gains in filling a stock Holden V6 with premium (higher octane) unleaded?

Nah, there's no point in running premium in the standard engine. It doesn't respond.


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What mods would you recommend with a budget of around $1000?

The first thing I'd do is extractors and exhaust. The gains vary from car to car, but there's probably a healthy 15-20 hp at the wheels. We've had cat-back systems pick up maybe 5-8 hp at the wheels, so it's the extractors that can make a big difference - I've always used good mandrel bent extractors, never crappy ones. Two and a quarter inch piping is nice on a V6 - 2? is over-kill. They sound shit-house and they don't make any more power - even with a thorough re-map. The standard cat, so long as it's in good condition, is fine - unless you're going supercharged.

Don't forget, the factory has to make their exhaust system comply with emissions, noise levels etcetera - an aftermarket system doesn't have to comply with that. It's just a matter of what you can get away with from day to day.

What would come after an exhaust?

Depending on what bonnet frame you've got - they changed them during the VP model - you can put a factory over-the-radiator intake on it. On the dyno I haven't seen much gain - but out on the road there appears to be about 6hp at the wheels in it (as calculated from a G-Tech). I remember a VR V6 Commodore with extractors, exhaust and mapping dropped its 0-100 km/h time by about 0.1 second with the fitting of the intake.

Rather than go over-the-radiator, you can always cut a hole and go down through the guard - but the country guys don't want to run that kind of set up. There's always that very real fear of getting water into the engine.

Would you suggest a computer re-map at this point?

I wouldn't remap the engine if you had immediate plans to go further, but - if you were going to leave it at an exhaust and intake - I'd definitely get it re-mapped. That costs about $600. We've seen from 20hp to around 36hp from a re-map at this stage - but it depends a lot on the condition of the engine.

When we map a car - depending on its application - we might program it to run 13 to 1 air-fuel ratio at WOT; they love it. In terms of timing, we'd put in around 26-28 degrees at full noise (22 is standard). Going up to 30 degrees doesn't make much difference - so I don't like to go that high. And that'd be running on unleaded fuel still - there still isn't any advantage in mapping for premium. There's nothing to be gained in that area.

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You can do extractors and exhaust on a late VS-onward car (which uses an airflow meter) and the management system will know what's going on and it'll maintain about the standard air-fuel ratio. The same exhaust on the earlier cars (with a MAP load sensor) will still be running of that same base program - oblivious to the effects of the changes. That means there'll be a mixture variation at high load - it goes leaner. This leaner mixture helps to make power in itself, but you'll often end up with flat spots. Despite the favourable effect on the early vehicle's air-fuel ratios, you'll find that the later model cars actually respond better to exhaust and intake. That's largely because of their better heads and intake.

With an exhaust, intake and re-map, I'd say around 138-140 rear wheel horsepower is not out of the question on a VN-VR. The same on a VS should give around 155-158hp - but I've had some do more and some do less.

Best of Both Worlds

Leon tells AutoSpeed he's now got software to convert earlier V6 Commodore ECUs to run with an airflow meter as well as retaining the standard MAP sensor. The MAP sensor is said to give best transient throttle response, while the airflow meter delivers more accurate constant-state air-fuel ratios. Leon goes on to say, "We've pulled the best parts out of the VT software and crammed it into the earlier ECM". Contact Awesome Automotive for more details.

So - given your extractors, exhaust, intake and tuning mods - how would fuel consumption be affected?

Under load, pretty well all of the Commodore V6s are set up too rich. Leaning them out will obviously save a bit of fuel during point and squirt.

Under cruise conditions, the VN-VPs cruise on 14.7:1, while VRs onward use a lean cruise function. Lean cruise kicks in once coolant temperature is over 80 degrees C, you're travelling faster than 68 km/h, the engine is spinning at between 1600 and 2800 rpm and manifold vacuum is between 40 kPa and 60 kPa absolute (the VS-on works on an airflow meter signal). Once 150 seconds is timed out under those conditions, the air-fuel ratio will lean out one point every 0.15 seconds. They're set up to run as lean as 16.5:1 - but only at that light load cruise situation. You can't be driving on and off the throttle.

When we map an early V6, we'll usually put VR lean cruise into the program. We can also change the parameters - like the 150-second delay - inside the software. This all makes your fuel economy skyrocket.

The next traditional mod would be a heads and cam package - is this what you'd recommend?

Regardless - whether you go blower, cam or whatever - the first thing I'd do at this stage is check the seat pressure on the valve springs, make sure the springs are okay, ditch those retainers and locks and put chrome-moly ones in. That's your insurance policy against losing an engine through a cracked retainer.

We've never broken a V6 with torque - but they have been broken with revs. If you have a look at the crankshaft, they're very thin on the overlap on the journals. Leon's Rule of Thumb is - don't consistently rev them over 6500. You're asking for trouble.

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Instead of the traditional stuff, I'd say a supercharger is the way to go. Sure, it costs more - but, if you decide to sell the car, you can un-bolt it all really easily and return the car to standard. A standard vehicle appeals to anybody - whether it's Mum and Dad or somebody that wants to do one up. Then you can either sell the blower separately or keep it for your next car.

A high performance cam will always give you a lumpier idle, which can attract police attention. Plus, a new aftermarket camshaft often costs around $650. And - let's face it - when you've spent $650 on that stick, you'll want to have the heads re-con'd and you might as well do some porting. You'll have spent $1400 - easy - on the heads, $650 for the cam and then there's the necessary re-map. Of course, a cam'd re-map takes longer to do, which means it'll probably cost about $800 to get spot-on. On top of all this, you really don't have the compression to use the cam properly; it'll work, but it could be heaps better. So, really - to make the most of it - you'll need a full rebuild.

Then, at the end of all that stuffing around, all you've got is an engine that makes power at about 6000 rpm. And these engines don't like to rev that hard. If the car is an auto you can put a high rev stall in it you'll get away with the lack of bottom-end; but you're turning it into a drag car.

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Given supercharging is your preference, what would be your recommended type of blower?

I'd go for positive displacement blower. With a centrifugal blower, you'll only attain maximum boost at peak revs. So down at around 2800 rpm, you'd be lucky if you have 1 psi boost. It's all top-end - a bit like a cam. Everyone drives from idle to about 3500 - wouldn't you be better to have boost straight off idle? A positive displacement blower will do that.

If I had unlimited bucks I'd go for an Autorotor or any type of screw blower for sure. If you're on a budget, go for the factory Roots style blower. There's the 122 Eaton, which is a little bit bigger than the factory one, and it bolts straight in its place. Well, it will in the VS-onward - they've got the injectors in the heads, but the previous models had the injectors in the manifold. Of course, you could always mount them off the side - but, to me, they look ugly. A displacement blower sits in the valley and that's it. Depending on the set-up, you can maybe find a carburettor manifold and put injector bosses into it - and an Autorotor will bolt straight onto a 4-barrel flange.

That's not to say a centrifugal is a bad blower. What you can do is use the base aftermarket V8-trim blower and put it onto a V6. You can spin that blower faster and bleed off excess boost at high rpm. There's nothing stopping you spinning it at double the speed and making - you know - 5-6 psi straight off idle and bleeding off the excess at higher rpm. Then you'd have the same characteristics of a displacement supercharger. We've got the software to control a boost control valve - you know, you could run a big Goyen valve and bleed off excess boost. It's probably a bit of an inefficient way of doing things - but you can have boost straight off idle.

With a displacement blower, I'd put up to about 12 psi into an engine with the standard compression ratio - but that'd be on premium unleaded. And it'd be good to run an intercooler. That's where the centrifugal blower has the advantage - it's easier to hook up an intercooler.

Depending on the particulars, about 8-psi boost will take you up around 180 horsepower at the wheels. That's pretty serious - standard 125hp up to 180hp. But keep in mind, if you're doing it with a centrifugal blower, you're doing it all at the top-end. But, come to think of it, the V6s don't go bad off the line anyway...

Speaking of supercharged V6s, what sort of tweaks have you done to the factory blown VS-VT?

We haven't done many here, but they're an intriguing bit of gear. They run about 11.2:1 air-fuel ratios standard - sustained. They also back a l-o-t of timing off with rising intake air temperatures as well. Stick one on the dyno and the first run you do it'll make some serious horsepower - about 158hp - but each subsequent one will keep dropping and dropping. Over about 7 or 8 pulls in succession, we've seen 38hp lost at the wheels! It was cookin' - but you'd probably never get it that hot on the road.

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Here's a stockie graph compared to the same car with a full re-map - that's all we did. Not too bad eh?

Well, there you have it Holden V6 fans - words from one of the most knowledgeable tuners you'll ever find. Next time we speak to Leon, we'll be asking him about Holden V8s - so stick around.


Awesome Automotive, South Australia
+61 8 8277 3927

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