changing engine compression bam ????

[paul-murphys]

can anyone tell me the compression ratio on a lcr engine code bam please? and what are standard size pistons? thankyou

 

[Dan1720v]

9:1 compression, not sure on standard size bore though.

 

[paul-murphys]

what would be a benafits of changing to 8,5,1 or 9.25.1

gone hybrid but may go big turbo in future an want engine to be strong, going 83mm bore but not sure what to change compression ratio to. anyone shed light on benafits of changing and whats best option? thankyou

also found this

http://www.clubgti.com/FORUM/showthread.php?t=34368&page=4

 

[Willie]

its 9.5:1

 

[Muttley]

AMK and BAM engines
Compression ratio 9½:1
Bore x stroke 81x86.4 mm

Increasing bore will increase CR if everything else is left equal.

By my rough calculations, if you increase the bore to 83mm, swept volume goes up to 467.5cc, (engine becomes 1870cc from 1800) and CR goes up to 9.9:1. That's quite an increase.

But in a turbocharged engine the effective compression ratio is also affected by the boost.

I'm pretty certain you'll need a new map in the ECU . . .

 

[paul-murphys]

im going to stick with the 9.1 compression ratio but go 83mm bore, i believe keeps same compression ratio by the way the pistons are machined so will have a 1.9 but with standard compression ratio.

 

[Dan1720v]

how odd, mines 9:1... measured properly too!

 

[paul-murphys]

I'm thinking of changing compression as want to go big turbo in future but also changing engine to a 1900cc by using 83mm pistons which I believe are a good upgrade for engine. Does anyone know benafits of changing from 9.1 to and 8.5.1 as can get pistons with 8.5.1 straight away or have to wait if want 9.1 for pistons to be machined.

 

[Dan1720v]

8.5:1 means you can run higher boost, but will mean throttle response and general off boost driving wont be as good.

 

[paul-murphys]

How about 9.25.1 heard that's good for low down power

 

[Willie]

How about 9.25.1 heard that's good for low down power

If I were you I'd try and limit the low down power and sacrifice this for more top end power unless your planning on running a multi stage boost controller, sticky tyres, differential and uprated engine mounts to allow you to get this power to the road

 

[paul-murphys]

How much power would I lose low down and I though hybrid turbos run out of puff at 6.6 k guy who mapping was talking about altering the rev range so the car can rev higher he said 7500 is easy achiavable to have my peak power and yh updated engine mounts and after getting same diff as you. So what compression think should go for?

 

[Willie]

Sorry Paul I don't have the foggiest about compression.
All I know is the AMK/BAM OEM compression is 9.5:1

This is from the OEM spec sheets for the engine

 

[Dan1720v]

ah mines an APX bottom end..

Compression i'd try to keep at 9:1. or as close as possible.

You can go 8.5:1 pistons then check the squish and work out how much you need/can skim off the head.

 

[BBoy82]

Have you tried talking to the supplier of the turbo? If you run too high a compression ratio with higher boost, you risk 'pinking' or pre-detonation. IMO theres a reason you cant get those pistons off the shelf...

 

[paul-murphys]

I have to get them machined to that size as only go up to 82 and I want 83 also was doing a
deal on piston rod combo and only had pistons with those 2 compression ratios. Will just wait out and see what can offer me and how long will take to make pistons in size 83 mm. Will keep 9.1 cr

 

[Muttley]

9 to 1 is a reduction on the standard, which is 9.5 to 1, as several people have already said.

 

[paul-murphys]

Ok cool thankyou I read some where it was 9.1 which thought was same as 9.5.1 I'm not clues up on compression ratio but understand now
and you no if changing it to a 1.9engine will add much power and torque, thankyou