Any ideas on horsepower rating for the 3.3L if it wasn’t turbo?

[Turd Ferguson]

I am often surprised when watching my turbo gauge how it sometimes indicates very little to no turbo pressure even when I’m giving it more throttle and making it work a little. It kicks in when it’s supposed to and t’s operating normally, so I have no concerns.

What I find interesting is how strong the motor seems BEFORE the turbos engage. This brings me to my question: How much power would the engine produce if it was not fitted with twin turbos?

Any input appreciated.

I recently got a ‘22 GT2 Scorpion in Aurora Black. Loving it.

 

[Snicklefritz]

Without turbos the 3.3L engine on this heavy car would be a dog. You apparently don't know that the turbos are engaging before you feel the big boost. It isn't just off or on.

 

[D.J.]

Our cars have peak torque from ~1300rpm....(LITERALLY DUE TO THE TURBOS)

Peak power occurs at 6,000 RPM.
Without the turbos, it would be an entirely different driving experience.

The Kia Stinger 3.3 L V6 engine has a torque curve of 376 lb-ft of torque at 1,300–4,500 RPM. The engine also produces up to 368 horsepower at 6,000 RPM.

 

[Thomby]

For a very rough guesstimate, we could start with the fact that 1 atmosphere is ~14.7psi, and stock Stingers generally hit about 12-13 psi, or about 80-88% of an atmosphere.

In an idealized world, turbos adding ~85% more air would mean 1.85x the NA power. But since they generate heat, the air they add is less dense and an 85% increase in pressure adds fewer than 85% more air molecules.

So maybe the turbos are adding something like 60-65%, so divide 368hp by 1.6-1.65 and you're at ~225-230 horsepower without them. And that's peak, so it would feel even less powerful in the low/midrange since you wouldn't have the torque fill of our quick spooling turbos.

(Of course if the engine was intended to be NA, it would run higher compression and probably have more optimized valve timing, maybe getting back in the low 300hp range, like a slightly smaller Nissan VQ 3.7.)

 

[Grump]

Wikipedia says our motor is the twin turbo version of the Lambda II GDi 3.3, but doesnt specifically say its the RS model. Non RS models are 280-294HP and 280-290HP. The RS models are 278HP or 250HP. But like Thomby said the compression ratios are probably all different. I dont know how closely those models represent our engine but they are also 3.3L.

 

[Landshark]

my '97 Subaru SVX w/3.3L flat 6 had 230 hp

 

[Thomby]

Wikipedia says our motor is the twin turbo version of the Lambda II GDi 3.3, but doesnt specifically say its the RS model. Non RS models are 280-294HP and 280-290HP. The RS models are 278HP or 250HP. But like Thomby said the compression ratios are probably all different

Looks like those are mostly 11.5 and 12:1, versus 10:1 for the TT. I don't know if there's a rule of thumb for scaling power with compression ratio (I doubt it's completely linear), but going from 280-290hp to 225-230 is about a 20% reduction, which seems reasonable.

 

[oddball]

By "turbo gauge", are you watching the one in the dash? It updates extremely slowly and doesn't give useful detail. You'll want to use a real gauge if you want to watch manifold pressure.
The turbos are almost always affecting the engine performance. e.g. when lightly accelerating, the manifold pressure will be right around 0psi. A non-boosted car would have manifold pressure of 12 t o18 inches of mercury of vacuum. So the turbo gauge won't show anything, but it's already pushing air in there.
I haven't bothered with logs or anything but it appears there's a bit of a step function. The ECU will aim for around 0psi, 4psi, 8psi, 12psi, etc. depending on throttle. Very roughly stating.

 

[BIG-D]

I often wonder why no one has built a 3.8L yet and swapped it in with a pair of custom High mount turbos...

 

[rtv900]

For a very rough guesstimate, we could start with the fact that 1 atmosphere is ~14.7psi, and stock Stingers generally hit about 12-13 psi, or about 80-88% of an atmosphere.

In an idealized world, turbos adding ~85% more air would mean 1.85x the NA power. But since they generate heat, the air they add is less dense and an 85% increase in pressure adds fewer than 85% more air molecules.

So maybe the turbos are adding something like 60-65%, so divide 368hp by 1.6-1.65 and you're at ~225-230 horsepower without them. And that's peak, so it would feel even less powerful in the low/midrange since you wouldn't have the torque fill of our quick spooling turbos.

(Of course if the engine was intended to be NA, it would run higher compression and probably have more optimized valve timing, maybe getting back in the low 300hp range, like a slightly smaller Nissan VQ 3.7.)

^this is pretty accurate

 

[5tinger]

I really like how they've tuned so much instant low end power for the GT Stinger V6.

The motor feels very smooth and powerful.

 

[rtv900]

I really like how they've tuned so much instant low end power for the GT Stinger V6.

The motor feels very smooth and powerful.

it's not a "tune"
it's two small turbos that boost quick

 

[Buzzman12]

I've owned a few vehicles with V6 NA engines (Nissan, Toyota) and they all seem to fall into the 260-300 hp range.
Pure guesswork here, but I imagine the 3.3 would also fall into that range. It wouldn't be a complete dog, but certainly a lot slower.

 

[SRV]

The peak power calculation is easy to do.

NAhp = normally aspirated horsepower

NAhp x Boost = BoostedHp

NAhp x ( 1 + 13psi/14.7psi) = 370hp

NAhp = 370hp / 1.88

NAhp = 197hp

Therefore, the 3.3 TT engine puts out ~200hp without TT's.

This is why the car feels like a dog when there is an overboost condition.

 

[Thomby]

NAhp x ( 1 + 13psi/14.7psi) = 370hp
NAhp = 370hp / 1.88
NAhp = 197hp

This would be true if the turbos perfectly compressed the air with no increased heat. But in reality, 88% higher pressure does not mean 88% more air molecules. I used 60-65% which gives you around 225-230hp.

You could run the engine without boost and measure IATs, then again with boost, to better estimate how much air you're actually adding, but at that point you might as well just dyno it without boost.

 

[rtv900]

there's no way a modern NA 3.3 would only make 200hp. It would be more like 300.
The engine is a dog after an overboost because the ECU cuts it way down, it's not just the lack of boost.
Hell the GT3 is a NA 4.0 that makes 500hp.

 

[Thomby]

there's no way a modern NA 3.3 would only make 200hp. It would be more like 300.
The engine is a dog after an overboost because the ECU cuts it way down, it's not just the lack of boost.
Hell the GT3 is a NA 4.0 that makes 500hp.

An engine designed to be NA would have higher compression, higher powerband, and its intake, valve timing, and ignition all oriented around making NA power. An engine designed for turbos lacks all that.

The GT3 engine has 13.3:1 compression and revs to 9000. Dialing it back to 6000 rpm and 10:1 would probably cut it to 350hp. Even "older" engines like Nissan's 3.7 VQ or the Mustang's Cyclone V6 were 11:1 and 10.5:1, and those didn't have direct injection. Honda's latest 3.5 has 11.5:1 compression and about 285 hp (presumably tuned for midrange torque in family cars).

So if you stripped the turbos off our 3.3, increased the compression ratio to 11.5:1 or 12:1, and redid the intake & timing, you could hit 300hp. And if you cut the compression ratio on those other V6s to add turbos, you'd likely be at 250hp or less, which is probably the most our engine makes without boost.

 

[rtv900]

An engine designed to be NA would have higher compression, higher powerband, and its intake, valve timing, and ignition all oriented around making NA power. An engine designed for turbos lacks all that.

The GT3 engine has 13.3:1 compression and revs to 9000. Dialing it back to 6000 rpm and 10:1 would probably cut it to 350hp. Even "older" engines like Nissan's 3.7 VQ or the Mustang's Cyclone V6 were 11:1 and 10.5:1, and those didn't have direct injection. Honda's latest 3.5 has 11.5:1 compression and about 285 hp (presumably tuned for midrange torque in family cars).

So if you stripped the turbos off our 3.3, increased the compression ratio to 11.5:1 or 12:1, and redid the intake & timing, you could hit 300hp. And if you cut the compression ratio on those other V6s to add turbos, you'd likely be at 250hp or less, which is probably the most our engine makes without boost.

^totally
a 3.3 NA would be making 200hp in 1994
2020+ would increase that by about 50%

Interesting contrast (just since I'm watching mecum auto auctions) the original 90's viper got a pathetic 400hp out of 8 liters NA.
The 5th gen viper was 650hp with essentially the same displacement also NA

 

[Ah GetFd]

Just going by the Wikipedia Lambda description the most likely kw/hp output of a Lambda Engine is this

Hyundai Lambda engine - Wikipedia

en.wikipedia.org

Lambda II RS T-GDi​

​

It is a version of Lambda II GDi 3.3 engine with two turbochargers.

It produces 370 PS (272 kW; 365 hp) at 6,000 rpm and 52 kg⋅m (510 N⋅m; 376 lb⋅ft) of torque between 1,300 and 4,500 rpm.

I believe this is 274kW with the now fitted Bi Modal exhaust

Lambda II RS GDi​

Hyundai released a GDI variant of the Lambda RS engine for the 2012 Genesis and 2013 Genesis Coupe

3.3L (G6DH)​

The engine produces 282 PS (207 kW; 278 hp) at 6,000 rpm and 35.4 kg⋅m (347 N⋅m; 256 lb⋅ft) of torque at 5,000 rpm, earlier version of this engine were making 300 PS (221 kW; 296 hp) at 6,400 rpm and 35.5 kg⋅m (348 N⋅m; 257 lb⋅ft) of torque at 5,200 rpm.

Applications:

• 2016–2020 Genesis G80 (DH)
• 2011–2016 Hyundai Genesis
• 2012–2018 Kia K9 (KH)

3.3L (G6DM)​

The engine produces 253 PS (186 kW; 250 hp) at 6,000 rpm and 35.4 kg⋅m (347 N⋅m; 256 lb⋅ft) of torque at 5,000 rpm.

Applications:

• 2018–2021 Kia K9 (RJ)

So based on this information, the twin turbo setup 274kw/367Hp adds as I expected around 67kW/90HP to the base 3.3L Non Turbo engine being around 207kW or 277Hp.

 

[Thomby]

a 3.3 NA would be making 200hp in 1994
2020+ would increase that by about 50%

Interestingly enough, the early/mid-90s trio of Japanese sports cars (Toyota Supra, Nissan 300ZX, Mitsubishi 3000GT) all got around 220-225hp from their naturally aspirated 3 liter 6 cylinders, and around 300hp from their twin turbo versions.

In the case of the 300ZX, the engine dropped from 10.5:1 to 8.5:1 to accommodate the turbos. And 10-15 years later when they re-launched the Z with a 3.5, it got around 300hp (depending on trim/year) naturally aspirated with 10.3:1 CR.

For the Viper, I think at first they just added a couple cylinders to a low-stress, high-torque truck engine, made it out of aluminum, and called it good enough for their exotic coupe until the newness wore off, and then just a bit of optimization let them add 50-100hp (and later even more) to compete with Corvette and the Italians. And remember that even with "only" 400 hp it had something like 475 lbs-ft.