The release in Australia of the S15 Nissan Silvia has been greeted with mixed reactions. On the one hand, here is a replacement for the S14 200SX which first saw the light of local day way back in 1994. On the other hand, the SR20DET engine of the latest model is, um, pretty much the same as that which graced the mid-Nineties car! The S15 may well be winning local awards as a top performance car.... but at least in any straightline measure, its performance is simply more of the same. And 'more of the same' is also a phrase that's been applied to those who have had a close look at a S14 and S15 side by side on hoists - the undersides look damn' near identical.
All of which kinda drops the enthusiasm level of new S15 owners. Sure, it's a good car - but shouldn't it be a bit better? In fact like the much more powerful model released at the same time in Japan?
They're good questions, but ones that can be answered with some very simple - and relatively cheap - power upgrades. Cos one's things for sure - we've never seen so much extra grunt available from doing so little. And that's coming from people who regularly see turbo car percentage power upgrades of the order of 30 per cent from some easy changes - gains that NA car owners would kill for. But nope, in the case of the two Silvias we have lined up here, there was a power gain of around a staggering 50 per cent!
The Cars
Two Silvias, two colours, two owners and two workshops. Coincidentally, both Tony Rigoli Automotive and ChipTorque had - on the same day, no less! - two Nissan Silvias, with both workshops performing similar mods. At Rigolis there was a bolt-on happening to the white car - huge Apexi GT-series stainless exhaust, Apexi AVC-R electronic boost controller, and K&N filter. At ChipTorque, a locally made Lambros exhaust, new custom chip and TurboSmart boost control was matched with the only modification ingredient common to the two cars - another K&N exposed filter.
And, before you ask, both cars made similarish top end power...
As you'll see, a key ingredient in the power-up is a replacement exhaust. Pretty well any turbo car ever made benefits from a new hi-flow exhaust, but the Silvia is born with more of an impediment in this area that most cars. Why? Cos its exhaust is damn tiny! Off the turbo dump it's 57mm (2ΒΌ inch) but from there it gets worse. By the resonator it's down to just 47mm (1.85 inches) and it stays at that size all the rest of the way.
Yup, on a car with a factory 147kW (197hp) there's an exhaust diameter of well under 2 inches - and that's the OD! Add to that the squeezy press-bends and you're looking at an exhaust that appears suitable for a car boasting - maybe - a factory 85kW...
Hmmmm.
The White Car
In for a full upgrade that also included a $4050 HKS coil-over suspension, the white Silvia copped the Apexi exhaust without too many hassles. An off-the-dump system (as opposed to off-the-turbo), the Japanese exhaust did not include a new cat - so the standard unit was retained. The supposedly-for-S15 exhaust also needed a few minor mods to clear the tailshaft, but otherwise bolted on without probs.
A cute addition to the system is this easily fitted rear silencer insert - just the
thing when you want to be aurally anonymous. The new exhaust cost $2150 fitted.
Next up was the electronic boost control, which also includes a range of gee-whiz instrumentation functions. The Apexi AVC- Type R allows the setting of boost relative to engine rpm, displays throttle position and injector duty cycle, and looks pretty cool.
It uses a new wastegate pressure control solenoid (pictured here next to the now unused factory original) and....
... an underbonnet boost pressure sensor. Cost was a fitted $1350.
The final step was to remove the factory airbox and intake snorkel....
... and replace it with a cylindrical K&N filter. That added $250 to the bill.
So equipped, the car belted out 183hp at the wheels on 11 psi boost. (And remember US readers, we're using a Dyno Dynamics dyno here, not a DynoJet. The car as standard developed around 130hp at the wheels - and no, it wasn't a sick puppy. That's just the power loss you get through the tyres and the transmission and two small rollers....). So with boost up from the standard ~8psi to 11psi, with the new exhaust and new intake, power was elevated around 40 per cent! Stunning, huh? And then with boost up a bit further to 15 psi, hold on tight while power peaked at 199hp at the wheels.
And was the car happy at this power level? Well, with a fresh fill of premium fuel there was no sign of detonation (though on the old fuel that was previously in the tank the car was detonating on even low boost), and the mixtures were very rich at around 10:1.
The Yellow Car
And less than 15 kilometres away, another Gold Coast workshop was also modifying an S15. A car that arrived boasting...
...a $260 Turbosmart blow-off valve attached to a $160 shiny crossover pipe....
...and a $270 Turbosmart hi/lo (8/14 psi) boost control and a $95 K&N filter, this car made 127hp at the wheels on its 8 psi boost. Incidentally, the owner commented that he couldn't feel any performance difference with these initial mods...but there was more to come - much more!
An $1850 3-inch exhaust off the turbo was then fabricated and fitted by Lambros Hi-Tech Mufflers, along with a new hi-flo cat. With boost kept at the same 8 psi, this resulted in a dyno power pull of 154hp, a gain of 21 per cent!
Yes, those rumours of awesome S15 power gains from nothing more than an exhaust upgrade are certainly true...
Then what happened with some added boost? Upped to 14 psi, power rocketed. However, ChipTorque was concerned about the midrange detonation that they could hear, and the richness of the mixtures. The company then burnt a new chip ($975 including dyno time) which took out about 2.5 degrees of ignition timing through the midrange (3200 - 4800 rpm) and dropped the measured air/fuel ratio from the mid Nines to the high Elevens.
With the boost and these changes, power peaked at 203hp, a measured gain of a staggering 60 per cent!
Conclusion
One thing shows as clear as day.
The S15 Silvia is more responsive to simple changes than any other turbo car that we have ever seen. No - make that any car at all that we have seen!
Increasing the power at the wheels by a staggering 50 - 60 per cent is the stuff that dreams are made of. And that's without having to change the intercooler, fuel pump, turbo or injectors....
Contacts:
Tony Rigoli Automotive (Gold Coast)
07 5528 4666
ChipTorque
07 5596 4204
www.chiptorque.com.au
Lambros Hi-Tech Mufflers (Gold Coast)
07 5527 0053
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Us?
A few times during the period when we were assembling the material for this story we were asked what approach we'd take to modifying the S15 - what we would we do and not do? Well, starting off at the airfilter, we wouldn't place a new filter exposed to underbonnet heat and airflow in there. Instead, we'd just fit a big extra cold air duct to the standard airbox, modifying the box to take the new intake and placing the other end of the duct in a high-pressure frontal area. That'd both save a few bucks and also make sure that the engine (still with the standard intercooler, remember) breathes only air that's at the same temp as atmospheric. As for the exhaust, we'd prob go with a combination of the approaches taken in this article. The Japanese aftermarket exhausts are generally wonderful in their combination of flow and quietness, but we'd add a big-bore cat and have a new section of pipe made to connect the Japanese exhaust directly to the turbo - rather than going off the factory turbo dump. For boost control we'd go with neither of the approaches taken here. Instead, when we had a new chip custom-tuned on the dyno to provide the right timing and mixtures, we'd also have the boost lifted electronically. The ECU controls boost, so the right map can be re-written to change that parameter upwards. That has the potential to save lots of dosh over an add-on electronic boost control, while at the same time giving a factory neat result. (Extra cost over just having the timing and fuel done? Zilch!) And a new blow-off valve? Why bother? Julian Edgar
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