Engine BHP

monseiur · 17-07-2019 3:03pm #1

Can someone confirm if the following is true -
Take for example 3 versions of say a Skoda Octavia Diesel car, say it's available with 85 BHP, 100 BHP and 130 BHP engines, all have the same CC etc.
Is it the case that all 3 have the exact same engine block but that the different BHP is to do with all 3 having different injectors, fuel pumps, electronics etc.
So technically the 85 BHP could be chipped / mapped (?) to 130 BHP without blowing the engine.
Not planning to do this by the way, just following up after a pub discussion- I suggested the above and all my buddies said I was wrong, one who's a mechanic

tossy · 17-07-2019 3:15pm

Usually but not always (but usual in VW group engines) the different BHP figures will be down to different bolt on components such as intercoolers,Turbo, Injectors, MAF etc. It's also worth noting that highest output variant may also have different suspension and brake parts too.

kirving · 17-07-2019 3:27pm

In many (I think the majority of) cases, some bolt on parts will be different. In some cases, the only difference is in software ie: mapping.

hi5 · 17-07-2019 6:37pm

Different profile camshafts will keep the same cc but can have a huge affect on power output.

colm_mcm · 17-07-2019 6:41pm

hi5 wrote: »

Different profile camshafts will keep the same cc but can have a huge affect on power output.

I don’t think that happens much these days.

ianobrien · 17-07-2019 9:16pm

For VAG cars, some of the internal components can be different. For example, in the 2.0 diesel Leon, the 184PS engine has a lower compression ratio (15.8:1) than the 150PS (16.0:1) from looking at the specs in the brochure. The lower compression ratio is because of the higher turbo pressures.

For some Merc, there can be differences in the turbo (variable geometry or not) and I think FCA do the same thing.

Henry Ford III · 17-07-2019 9:56pm

Identical cc Ford's have different injectors and turbos to give variable outputs

Mjolnir · 18-07-2019 1:13am

Jesus never let him work on your car so.

As previously said it for the most part is simple bolt on parts, like turbo, injectors and a different map

320d and 318d for example 318d's have smaller injectors, turbos and a different map same motor

monseiur · 18-07-2019 9:37am

Thanks all for your very interesting and informative replies, now I'll have more solid info. for round 2 of this discussion with my bar stool mechanics:)

zilog_jones · 18-07-2019 10:19am

The lowest power diesels may have no intercooler - colder air can help deliver more power.

CorkMan_ · 18-07-2019 11:31am

Over time/miles would that make the lower bhp engine more reliable?

swarlb · 18-07-2019 12:13pm

monseiur wrote: »

Can someone confirm if the following is true -
Take for example 3 versions of say a Skoda Octavia Diesel car, say it's available with 85 BHP, 100 BHP and 130 BHP engines, all have the same CC etc.
Is it the case that all 3 have the exact same engine block but that the different BHP is to do with all 3 having different injectors, fuel pumps, electronics etc.
So technically the 85 BHP could be chipped / mapped (?) to 130 BHP without blowing the engine.
Not planning to do this by the way, just following up after a pub discussion- I suggested the above and all my buddies said I was wrong, one who's a mechanic

I think that most (modern) diesel engines start life (on the drawing board) at the top end, in your case 130, and are detuned according to the market they are destined for...
This saves both time and money as the initial 'block' or engine is assembled to one spec, then the items to fit the required power are fitted later.

colm_mcm · 18-07-2019 12:21pm

CorkMan_ wrote: »

Over time/miles would that make the lower bhp engine more reliable?

Depends on how it’s driven. A lower bhp version may be driven harder to compensate.

Cee-Jay-Cee · 18-07-2019 12:51pm

ianobrien wrote: »

For VAG cars, some of the internal components can be different. For example, in the 2.0 diesel Leon, the 184PS engine has a lower compression ratio (15.8:1) than the 150PS (16.0:1) from looking at the specs in the brochure. The lower compression ratio is because of the higher turbo pressures.

For some Merc, there can be differences in the turbo (variable geometry or not) and I think FCA do the same thing.

Compression ratio is determined by piston size/dome, cylinder volume and crank length. It has nothing to do with turbos.

cruizer101 · 18-07-2019 1:00pm

Do they not mean that because it has a turbo the initial pressure is higher and because of that it has a lower compression ratio. Where as without the turbo the initial pressure is lower so you want to try compress the air more.
The turbo isn't directly effecting the compression ratio but its presence is a design consideration in deciding the compression ratio.

swarlb · 18-07-2019 1:12pm

cruizer101 wrote: »

Do they not mean that because it has a turbo the initial pressure is higher and because of that it has a lower compression ratio. Where as without the turbo the initial pressure is lower so you want to try compress the air more.
The turbo isn't directly effecting the compression ratio but its presence is a design consideration in deciding the compression ratio.

Compression ratio is measured between the largest capacity and smallest capacity of the area between a fully opened and closed piston in an engine.
Skimming the head or block or fitting a thicker or thinner head gasket can change the ratio, but that's about it.
A 1.0 L basic engine with no turbo could have a higher compression ration that a 5.0 L engine with twin turbos.

cruizer101 · 18-07-2019 1:36pm

swarlb wrote: »

Compression ratio is measured between the largest capacity and smallest capacity of the area between a fully opened and closed piston in an engine.
Skimming the head or block or fitting a thicker or thinner head gasket can change the ratio, but that's about it.
A 1.0 L basic engine with no turbo could have a higher compression ration that a 5.0 L engine with twin turbos.

I know how its measured my point is as part of the design it may be decided that if the engine is to have a turbo they may alter the compression ratio compared to the non turbo version.

Surely they can alter it with different piston, connecting rod or crankshaft but still using same block

swarlb · 18-07-2019 5:23pm

cruizer101 wrote: »

I know how its measured my point is as part of the design it may be decided that if the engine is to have a turbo they may alter the compression ratio compared to the non turbo version.

Surely they can alter it with different piston, connecting rod or crankshaft but still using same block

Of course you can... The Brabham F1 cars of the 1960/70's managed to get in excess of 1000 BHP from a 1.5 iron blocked engine originally used in a family saloon car.
Anything is possible...

Kenny Logins · 18-07-2019 5:30pm

Cee-Jay-Cee wrote: »

Compression ratio is determined by piston size/dome, cylinder volume and crank length. It has nothing to do with turbos.

The compression ratio is lowered by design to allow for forced induction. I guess that's what was meant.

Engine BHP

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