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Engine rebuilding-overbore
tegwin - 14/9/09 at 09:27 AM

I want to play with an engine, as a learning tool and for a bit of fun.

I am looking into buying the same engine that I have in my polo and have a "play" with it.

its a 1.6 16V VVT Steel crankcase alloy head engine (standard its 125hp and 130nm)

What I was thinking was, strip it down and rebuild from the ground up with the possibility of adding a bit more bite to it without damaging reliability too much.

I was thinking about getting the block overbored to increase capacity, but how do you work out how much is possible without compromising the block?

And assuming you have managed to overbore the block, where do you buy suitably sized pistons for such an obscure engine?

Can a reasonable power increase be gained from higher capacity like this?

As well as the above I was contemplating fiddling with the head and fitting larger valves and intereting cams...

[Edited on 14/9/09 by tegwin]

[Edited on 14/9/09 by tegwin]

02GF74 - 14/9/09 at 09:38 AM

quote:
Originally posted by tegwin
And assuming you have managed to overbore the block, where do you buy suitably sized pistons for such an obscure engine?
Buron Power - they can supply pistons made to your spec. - not locost

Can a reasonable power increase be gained from higher capacity like this?
How much is reasonable and how much more capacity? Put it this way, the bhp of most production engines is around 75 % of the capcity i.e. 120 bhp for 1,600 cc ; if you get 100% then that is really good going i.e. 160 bhp from 1600 cc.

tegwin - 14/9/09 at 09:41 AM

Do you think its possible to get nearer 100% from an engine, but still keeping it normally aspirated?

l0rd - 14/9/09 at 09:47 AM

yes look at civic VTec

02GF74 - 14/9/09 at 09:49 AM

sorry but I am no expert but we do see figures aproaching 100% for certain engines;

e.g. Raw engineering getting 180 bhp from 1.6 16 valve 4age engine;

ISTR seeing 225 bhp from vauxhall red top

also 185 bhp from 1700 crossflow?

all normally aspirated but at eye watering prices plus only useable on the race track.

l0rd - 14/9/09 at 09:50 AM

I know someone that had a Renault 19 RSi. Same engine with my ex clio.
He turbocharged the engine and used pistons and conrods from the 1.9 diesel renault engine.

I assume as diesels run on high compression ratios they can be used on petrol turbocharged engines

sickbag - 14/9/09 at 09:54 AM

quote:
Originally posted by tegwin
Do you think its possible to get nearer 100% from an engine, but still keeping it normally aspirated?


It's easy to attain if you just increase the rev limit - 1000cc R1 motor makes about 160BHP, but at 11,000RPM. The torque figure is around 84Ft/Lbs though.

So, if you want more BHP then just raise the rev limit, if you want more torque then tune the rev range you have.

blakep82 - 14/9/09 at 09:54 AM

red tops can get near 300bhp. sbd have kits for 292bhp for a N/A engine

click

230~bhp is possible from a red top with standard internals i think

[Edited on 14/9/09 by blakep82]

MikeRJ - 14/9/09 at 11:31 AM

quote:
Originally posted by l0rd
I assume as diesels run on high compression ratios they can be used on petrol turbocharged engines


Diesel pistons are in general completely unsuitable for high performance petrol engines. They tend to be very heavy, have very thick rings and most have the combustion chamber built into the crown.

02GF74 - 14/9/09 at 12:34 PM

quote:
Originally posted by l0rd

I assume as diesels run on high compression ratios they can be used on petrol turbocharged engines


I am puzzled by this too ...... Diesel use high CR to heat up the air so much that the injected fuel commusts;

Petrol turbo enignes use air that has already been compressed so to avoid detonation (?) the CR of the engine is reduced. That is why you can buy decompression plates as a cheaper alternative to lower CR pistons.

Can't see how you can use a rod and piston from high CR piston to work in a low CR turbo engine.

Canada EH! - 14/9/09 at 01:58 PM

Check the manual and suppliers of pistons, they will tell you how far you can go, 60 thou is usually about tops for small 4 cylinder units. Larger pistons will also increase the compression ratio, which adds performance.

Coose - 14/9/09 at 02:16 PM

quote:
Originally posted by Canada EH!
Check the manual and suppliers of pistons, they will tell you how far you can go, 60 thou is usually about tops for small 4 cylinder units.


It depends on the motor. I've just taken out my '72 Yamaha XS-2 (653cc parallel twin) by 3mm (100 thou) taking it to 707cc, though the stock liners won't take much more. But, with new liners in the stock block I could go to 860cc, with a new block I can go to 990....

MikeRJ - 14/9/09 at 04:39 PM

quote:
Originally posted by 02GF74
quote:
Originally posted by l0rd

I assume as diesels run on high compression ratios they can be used on petrol turbocharged engines


I am puzzled by this too ...... Diesel use high CR to heat up the air so much that the injected fuel commusts;

Petrol turbo enignes use air that has already been compressed so to avoid detonation (?) the CR of the engine is reduced. That is why you can buy decompression plates as a cheaper alternative to lower CR pistons.

Can't see how you can use a rod and piston from high CR piston to work in a low CR turbo engine.


I think l0rd was possibly referring to the fact that diesel pistons are designed to cope with very high combustion pressures which you find in turbocharged petrol engines.