GT3 engine comparison with rivals

[boxerTen]

A comparison of the current GT3 engine with engines from other manufactures suggests the GT3 engine is somewhat understressed! In particular, comparing the stroke and revs at maximum power for various engines (in order of decreasing piston acceleration)

Gallardo ...... 92.8mm and 8000rpm
Ferrari F430 .. 81.0mm and 8500rpm
Honda S2000 ... 90.7mm and 7800rpm
BMW M3 V8 ..... 75.2mm and 8300rpm
911 GT3 ....... 76.4mm and 7600rpm

Given the significantly shorter stroke of the GT3 it ought to be able to spun faster. A back of the envelope calculation suggests 8800rpm is realistic ... which implies around 470bhp i.e. 130bhp/litre.

[PolarExpress]

boxerTen said:

A comparison of the current GT3 engine with engines from other manufactures suggests the GT3 engine is somewhat understressed! In particular, comparing the stroke and revs at maximum power for various engines (in order of decreasing piston acceleration)

Gallardo ...... 92.8mm and 8000rpm
Ferrari F430 .. 81.0mm and 8500rpm
Honda S2000 ... 90.7mm and 7800rpm
BMW M3 V8 ..... 75.2mm and 8300rpm
911 GT3 ....... 76.4mm and 7600rpm

Given the significantly shorter stroke of the GT3 it ought to be able to spun faster. A back of the envelope calculation suggests 8800rpm is realistic ... which implies around 470bhp i.e. 130bhp/litre.

The GT3 engine is relatively unstressed at the 7800rpm (Mk1), 8200rpm (Mk2), and 8400rpm (7GT3) rev limiters. The engines were designed to safely run to over 9000rpm from the outset, but Porsche placed the lower limiter on in the interests of longevity/reliability.

Edited by PolarExpress on Monday 28th May 00:59

[andy tims]

One of the theories behind why GT3 geraboxes so often need rebuilding after 40 - 50k miles (when they are basically the same as the 993 GT2 gearbox that coped with more power), is that with gear changes occuring at higher revs than with the 993, the gearbox sustains a higher shock loading. Whether Porsche understood this when the GT3 was designed, who knows?

However, even higher revs would probably shorten gear box life even further.

[Murcielago_Boy]

I'm not that technically minded but when my 996RS was being dynoed (403bhp) it's power would tail off after some 7000rpm. The Ferrari 360 CS which was being dyno-ed would produce peak power at peak revs..

I was told that if you add revs to the Ferrari it would continue to increase in power whereas the there was no benefit to lifting the revs on the Porsche.

[DJC]

boxerTen said:

A comparison of the current GT3 engine with engines from other manufactures suggests the GT3 engine is somewhat understressed! In particular, comparing the stroke and revs at maximum power for various engines (in order of decreasing piston acceleration)

Gallardo ...... 92.8mm and 8000rpm
Ferrari F430 .. 81.0mm and 8500rpm
Honda S2000 ... 90.7mm and 7800rpm
BMW M3 V8 ..... 75.2mm and 8300rpm
911 GT3 ....... 76.4mm and 7600rpm

Given the significantly shorter stroke of the GT3 it ought to be able to spun faster. A back of the envelope calculation suggests 8800rpm is realistic ... which implies around 470bhp i.e. 130bhp/litre.

It doesnt work like that! Throw the S2000 engine away, it isnt comparable in this example because of the engine size.

Engineering doesnt work in linear thoughts like this, Porsche's line of thought certainly doesnt! Now, Im not the world's biggest fan of the GT3 (in any guise) as most ppl know, but its engine really does brook no argument. Ive asked the question many times has anybody seen a GT3 block do 50,000 miles yet (Im still waiting for a yes actually) but if I was putting money on it, my cash would be on the GT3 block to do the most miles before needing a rebuild than any of the others ...S2000 excepted. The Ferrari and Lambo units might be more funky, but no way in hell would I trust an F430 to take the same punishment from such a wide variety of drivers as a GT3 and last aswell. Given the play off between 470BHP and lasting 20,000 and miles 420BHP and lasting 50-80,000 miles I think we all know which way Porsche will always leap, whereas I think we all know which way Ferrari will leap!

[boxerTen]

DJC said:

It doesnt work like that! Throw the S2000 engine away, it isnt comparable in this example because of the engine size.

...

Given the play off between 470BHP and lasting 20,000 and miles 420BHP and lasting 50-80,000 miles I think we all know which way Porsche will always leap, whereas I think we all know which way Ferrari will leap!

The engine size is not important, rather its the individual cylinder size. If Honda put 8 cylinders of S2000 dimension on a single crank you'd have a 4.3 litre eight producing 475bhp - and you can bet it would last 100,000 miles. The bhp/litre is close to the GT3s but Honda is using a stroke nearly 20% longer. The stresses are 40% higher as a result. That puts their engine in a different league to the GT3s.

The conclusion is the GT3 engine is simply under-performing. It may be the block isn't strong enough to handle higher stresses - in which case Porsche should design a more modern one that can.

[ukwill]

I reckon an NSX with a cherrybomb exhaust and K&N filter would murder a GT3.

[johnfm]

ukwill said:

I reckon an NSX with a cherrybomb exhaust and K&N filter would murder a GT3.

you forgot the 'thank you' at the end.

[ukwill]

johnfm said:

ukwill said:

I reckon an NSX with a cherrybomb exhaust and K&N filter would murder a GT3.

you forgot the 'thank you' at the end.

thank you

[andy tims]

Murcielago_Boy said:

I'm not that technically minded

Me neither

Murcielago_Boy said:

I was told that if you add revs to the Ferrari it would continue to increase in power whereas the there was no benefit to lifting the revs on the Porsche.

Simplistically - Ignoring friction losses, power is a factor of torque x revs so the higher the revs the higher the power output. Thats why with lighter internals / less friction losses bike engines & F1 cars rev so fast - it's to get more power.

Edited by andy tims on Wednesday 30th May 20:37

[johnfm]

andy tims said:

Murcielago_Boy]I'm not that technically minded [quote said:

Me neither

Murcielago_Boy said:

I was told that if you add revs to the Ferrari it would continue to increase in power whereas the there was no benefit to lifting the revs on the Porsche.

Simplistically - Ignoring friction losses, power is a factor of torque x revs so the higher the revs the higher the power output. Thats why with lighter internals / less friction losses bike engines & F1 cars rev so fast - it's to get more power.

Ah, but the heads must be able to flow the air at these high revs. There comes a time when VE reduces to a point where extra revs do not equate to extra TQ or HP.

[gdunc]

DJC said:

Ive asked the question many times has anybody seen a GT3 block do 50,000 miles yet (Im still waiting for a yes actually)

53k and in very rude health. Think there will be loads in the 40k band at the mo and think someone on here has one which has done 70k odd and is also strong (all mk1s btw)

[Merritt]

Im sure Timmo put more than 50k miles on one of his 996RSs... im sure he'll be along soon to confirm or deny..

Steve M

[Rob_R]

boxerTen said:

It doesnt work like that! Throw the S2000 engine away, it isnt comparable in this example because of

The conclusion is the GT3 engine is simply under-performing. It may be the block isn't strong enough to handle higher stresses - in which case Porsche should design a more modern one that can.

But you have to bear in mind what both engines are designed for. It wouldn't surprise me one iota if the GT3 engine is less stressed than the S2000 engine even if GT3 engine internals are made of more exotic materials. The simple fact of the matter is the GT3 has to race - hard. And every last component has to last periods of up to 24 hours sustained heavy loading.

We prepare a GT3 for race events every other weekend here, and over the last two seasons of racing the only faulty component in the engine was a spark plug.

Not trying to undermine your knowledge (which is very probably superior to mine), just offering the standard salesman's reply!

[DanH]

boxerTen said:

DJC said:

It doesnt work like that! Throw the S2000 engine away, it isnt comparable in this example because of the engine size.

...

Given the play off between 470BHP and lasting 20,000 and miles 420BHP and lasting 50-80,000 miles I think we all know which way Porsche will always leap, whereas I think we all know which way Ferrari will leap!

The engine size is not important, rather its the individual cylinder size. If Honda put 8 cylinders of S2000 dimension on a single crank you'd have a 4.3 litre eight producing 475bhp - and you can bet it would last 100,000 miles. The bhp/litre is close to the GT3s but Honda is using a stroke nearly 20% longer. The stresses are 40% higher as a result. That puts their engine in a different league to the GT3s.

The conclusion is the GT3 engine is simply under-performing. It may be the block isn't strong enough to handle higher stresses - in which case Porsche should design a more modern one that can.

The Honda engine is crap though - absolutely no torque. All peak bhp at the expense of torque.

[kayc]

DanH said:

boxerTen said:

DJC said:

It doesnt work like that! Throw the S2000 engine away, it isnt comparable in this example because of the engine size.

...

Given the play off between 470BHP and lasting 20,000 and miles 420BHP and lasting 50-80,000 miles I think we all know which way Porsche will always leap, whereas I think we all know which way Ferrari will leap!

The engine size is not important, rather its the individual cylinder size. If Honda put 8 cylinders of S2000 dimension on a single crank you'd have a 4.3 litre eight producing 475bhp - and you can bet it would last 100,000 miles. The bhp/litre is close to the GT3s but Honda is using a stroke nearly 20% longer. The stresses are 40% higher as a result. That puts their engine in a different league to the GT3s.

The conclusion is the GT3 engine is simply under-performing. It may be the block isn't strong enough to handle higher stresses - in which case Porsche should design a more modern one that can.

The Honda engine is crap though - absolutely no torque. All peak bhp at the expense of torque.

Similar to the Gt3 engine then?

[993rsr]

gdunc said:

DJC said:

Ive asked the question many times has anybody seen a GT3 block do 50,000 miles yet (Im still waiting for a yes actually)

53k and in very rude health. Think there will be loads in the 40k band at the mo and think someone on here has one which has done 70k odd and is also strong (all mk1s btw)

Mk1 GT3 Manthey K400 65k miles still spot on.

[wheeljack]

All very well saying it is understressed by having lower piston acceleration due to the smaller stroke, but what about the extra mass from the significantly larger piston! 100mm versus 92mm (Ferrari & BMW) next largest from your list.

The higher mass will not only come from the diameter but also potentially a larger diameter gudgeon pin. A larger pin will also force a taller piston crown height and a larger con-rod small-end. All adding to the reciprocating mass.

Also taking the revs up higher will mean having to shift the tuning "sweetspots" higher up the rev-range, however not necessarily with the corresponding BMEP to achieve the 130bhp/litre @ 8800rpm. And lets face can the GT3 afford to lose anymore low-end torque!

Edited by wheeljack on Wednesday 30th May 18:56

[maximu5]

saw an MK1 the other day with 120k plus miles on the clock and which has done quite a few track days and still delivers 370 hp from a standard engine.

[andy tims]

Tim Court's GT3 has done 50k

Mine is not that far behind at 42k

Glad to see we are ignoring kayc the GT3 troll so far - can we make that a policy please?

Edited by andy tims on Wednesday 30th May 20:41