For literally years we have warned against re-mapping naturally aspirated cars that are otherwise standard. Sure, it can be done, but an adequate gain for the dollars we have never seen. Mechanically modify the car - exhaust, intake, perhaps even cams - and without a doubt there will be improvements to be had out of the standard management system. Mapped real-time on the dyno and the results will be there. But not on standard engines - why would the manufacturer have left that power untapped?
But that philosophy may no longer apply, not with the Holden/Chev LS1 engine as fitted to the Australian cars, anyway. Why? Well we recently watched a dead standard Holden Special Vehicles GTO coupe (a 255kW Monaro by any other name) get re-mapped real-time at ChipTorque in Queensland. And the dyno results were nothing less than magnificent - a power gain right through the rev range from 2600 rpm to the redline, peak power lifted by 8 per cent, and over the last 1000 rpm, gains as great as 25 per cent!
And having watched all the hard yards, we might add that it was obviously no easy task - this wasn't a case of whacking in a pre-designed set of maps and then doing some minor tweaking to get it maxing. No, it was more a long hard real-time struggle to get those kW happening.
With around 6000 kays on the clock, the GTO was simply a well run-in standard car. Apart from looking brilliant in (exterior and interior) yellow, there was nothing to make it different to any other 255kW HSV version of the Monaro. As we covered in our test of the GTO ["New Car Test - HSV GTO Coupe"], the HSV version of the two door differs significantly in its driving outcome from the Holden car, however from an engine perspective all is identical to any other 255kW HSV. For example, the GTO doesn't get the roar-inducing Monaro airbox intake; it uses the same subtle sounding intake to the airbox as other HSV cars.
So just because it's a two-door there's no reason why it should have any more power than any other HSV 255. However, with a dyno'd 184kW at the wheels it was a lot stronger than the last HSV 250-255 we saw on these rollers. In fact, that particular engine was the previous model's 250kW version, but it made only 168kW at the rollers. Using the normal 30 per cent driveline loss (in reality, lots of the loss is actually caused by the tyres on the rollers and other factors), that would make this GTO engine good for 262kW at the flywheel - from an engine rated at 255! Give up? It certainly can be hard trying to draw any relationship between rear wheel and flywheel figures; best to just say that on this dyno on this day this car had a rear wheel peak of 184kW.
Once the baseline had been established - complete with a nasty trailing-off in power over 5000 rpm - it was time to start the re-mapping. ChipTorque's Lachlan Riddel downloaded his 'best guess' program, one that reduces the severity of the ignition timing knock retard, takes out some of the high-intake-air temp fuel enrichment, and puts in a little more ignition timing. This is the mix of factors which in the past has shown good, safe results on this engine - but not this time. Dyno run Number Two placed a line on the screen which had exactly the same peak power - and was within a few kilowatts elsewhere as well.
Not good.
The next step was to lean the commanded air/fuel ratio a little (so that the computer would also be actively striving for this new value under full load), and take out a bit more of the high intake air temp enrichment. But again there was almost no change in the shape of the power curve - just a little blip of perhaps 5kW at the extreme top end.
We won't say that Lachlan started to sweat - that'd be untrue. But certainly this was a car where whatever he had found to give immediate results in the past was doing little this time. And that's as good an argument against off-the-shelf one-size-suits-all chips as you're likely to find.
Over the next hour Riddel punched the keys to his laptop, listened intently on earphones for the sound of detonation (the 'phones are fed from a small amplifier which in turn uses a block-mounted microphone), and data-logged the amount of knock retard that the ECU was using during each run. This - and plenty of other info - was available on the GM Tech 2 diagnostic tool plugged into the car's ECU and hung from the steering wheel centimetres from his eyes.
It was a slow process - at one stage the factory ECU was pulling out as much as 5.5 degrees of ignition timing because of detonation - but gradually the numbers were whittled back until no detonation was audible through the earpieces and the factory ECU knock retard under these hot and difficult dyno conditions was only 1.3 degrees. Incidentally, as with all very experienced tuners, Lachlan wasn't listening so much for the 'tink tink' of detonation, but instead to that 'sharp' edge that characterises the sound of an engine near knock.
In fact, with a fair degree of knock retard still showing on the Tech 2, an interim power graph showed power well over the 200kW at the wheels figure: the final lower output curve was deemed by the tuner as both giving good results but also being safe. Of course, premium fuel will be obligatory for this engine from now on. Perhaps more confusingly, if the owner decided to drop the exhaust or make some major free-breathing intake mods, the engine may now well go backwards in power - the greater cylinder filling would yield higher combustion pressures and so may result in increased detonation, resulting in lots of knock retard and so reduced power.
And so what are the actual dyno results? From around 3000 - 5000 rpm the power is up by 8-16kW (typically about an 11 per cent lift), while as mentioned earlier, peak power rose from 184 to 200kW - a gain of 8 per cent. But it was at the top end - where almost certainly too much fuel and too sensitive a knock sensor were conspiring to keep the engine safe but well down in power - that the huge gains were made. Sure, the engine won't see over 5000 rpm very much in normal duties, but unlike a turbo engine (where short-shifting can bring boost up faster and so give better acceleration) holding this engine to higher revs will certainly give faster acceleration. At 5500 rpm power is up by 16 per cent - that's 18kW! - while at 5800 it's up by a truly massive 40kW, or 25 per cent! Now if the gain was there and nowhere else, there'd be less cause for excitement - even with those numbers. But over the whole rev range from 2500 rpm there is a solid power gain.
Well, that's what the dyno said - but how'd the owner feel? When we talked to him a few weeks later he was ecstatic. "It's totally different to drive," he said. "I didn't think that they'd be this much difference."
"The throttle response is much better at the top end - when I drove it out of the workshop I stood on it, and I found I was changing gear earlier than I normally would - there was about a thousand rpm left each gear change. It wasn't looking at the tacho - just listening to the engine - and it was so much faster I was changing earlier.
"I am not really sure about fuel economy - there's no difference on the highway. But around town - where I drive it pretty hard - it was using a lot and now it seems to be using a bit less.
"I don't think that there is anything else you could do to get that much power - I priced a cam alone and it was $900. But I'd only recommend getting a custom chip tune - not just sending the PCM down to get the chip changed over."
Of course, with any engine management modification like this, getting just the same results on another car may be problematical. After all, to start with this one had more power than other similar engines we've seen on the dyno - and it certainly responded very well to modification. That's to take nothing away from what was achieved here - but we'd be loathe to say that an identical result could be able to be achieved on all HSV GTO coupes.
Still, it's bloody impressive, you have to agree!
www.chiptorque.com.au
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