2.5 Turbo

I dont think the answer is straightforward, so it might get someone's grey cells moving.

What do you believe would be an accurate normally aspirated equivalent of the 2.5 litre turbo GTA ? Assuming that the boost pressure is standard.

I know the 3 litre GTA produces less grunt, so I assume it would had to be at least 3.5 or perhaps 4 litre ?

Can't you just pro rata the BHP in an atmo by cc's?

My Slaguna 3l 24v V6 is 210 It's all about EFI

My Slaguna 3l 24v V6 is 210 It's all about EFI

Nah. Its also about induction, heads etc

My 4.0l V8 with EFI had 225 bhp at the fly
My 4.0l Straight 6 with EFI had 380bhp at the fly

Atmo is 2.85l and develops 160 bhp, therefore to get to 200 bhp

160/2.85 = 56.14

Turbo is 200 bhp, so 200/56.14 = 3.56 ie 3560 cc

That assumes that you can replicate the bhp per litre as the engine gets bigger, but with no major head or efi work

Brain is addlled (been doing financial models all day) so I apologise if my maths and assumptions have glaring errors

My Alfa 159 is 3.2l V6 n/a with 250 bhp
My Defender is 2.5l TD5 with 122 bhp
My M6 was 5l V10 n/a with 500bhp

The M6 vs Defender: 2x as many litres, 2x as many pistons, but way more than 2x bhp. Admittedly that's the difference diesel vs. petrol, performance vs. pure grunt work... but the math still addles my brain too

[stephendell]

What do you believe would be an accurate normally aspirated equivalent of the 2.5 litre turbo GTA

What do you mean by equivalent? Performance, Lap times, BHP?

Atmo was usually faster round shorter test circuits as the turbo car could not exploit the smaller length straights.

h

What do you believe would be an accurate normally aspirated equivalent of the 2.5 litre turbo GTA

What do you mean by equivalent? Performance, Lap times, BHP?

Atmo was usually faster round shorter test circuits as the turbo car could not exploit the smaller length straights.

I dont think you can compare aturbo lump to a N/A the turbo increases torque by a considerable amount in order to get the torque you need major capacity increases hence 5ltr V10 giving 500bhp nobody mentioned torque so bhp is only part.of the story. i beleive the number of cylinders also increases torque. so i beleive the turbo car will always out perform the N/A engine making the same power...ill stand corrected if someone of greater knowledge will enlighten us all?

Si21

Not quite sure what your trying to get at but I'm reading it as what Atmo engine produced close to the Gta's power and torque figures. You can't just say a 4.0 v8 for instance because a 4.0 v8 in aRange Rover puts out about 170 bhp whereas a 4.0 v8 in say an M3 is over 400 bhp. The closest engine I can find is a 1979 E23 732i which put out 200 bhp (200 for GTA) and 284 n/m (285 GTA). The power delivery of the engines would be very different though. V engines tend to produce more torque low down but don't rev as freely

What do you believe would be an accurate normally aspirated equivalent of the 2.5 litre turbo GTA

What do you mean by equivalent? Performance, Lap times, BHP?

Atmo was usually faster round shorter test circuits as the turbo car could not exploit the smaller length straights.

I dont think you can compare aturbo lump to a N/A the turbo increases torque by a cosiderable amount in order to get the torque you need major capacity increases hen vQp 5ltr giving 500bhp nobody mentioned torque so bjp is only part.of the story.

Si21

[BIG_MVS]

Sounds like someone's been playing that popular "my cars better than your car" pub game

Not sure Paul to be honest but I guess the 3.5 Renault V6 engine would be about the same performance (not BHP obviously).

Sounds like someone's been playing that popular "my cars better than your car" pub game

No, I was (for some unknown reason) thinking of the F1 Turbo days where they had a 1.4 (I think) turbo charged engine that chucked out near on 900 BHP - more in qualifying as they used one lap 'grenade' engines with over 1300 BHP.

I know this, as a comparison, is about as far away as Pluto, but it just got me thinking as to what size a normally aspirated lump would need to be to meet the power output of the Turbo verison. I think Blueg33 estimate sounds about right. Thats what I would have calculated, but I thought there may had been other considerations.

[Alpineandy]

The comparison starts to look a bit out when you add a fireblade into the equation.

My Slaguna 3l 24v V6 is 210 It's all about EFI

Hey Clee,

Have you pulled the pipe off the air filter box that goes down to the anti-resonance / restrictor box ?. Do it, Do it...
You will not beleive how much better it picks up over 4000rpm, oh and the noise !