[Diy_efi] Compression figures - was those bosch 4 point plugs

[Mike]

At 08:00 AM 10/10/05, you wrote:
>>Did a compression test, its 150KPa all round, ie Dry test, no
>>extra table spoon of oil in chamber, 2 valves per chamber, engine
>>done about 262,000Kms  etc, I think its a bit low but each
>>chamber is within 5% of the average...Right now the car is running
>>very smoothly on cruise but have a bit of tappet noise when
>>accelerating hard at 3,000+ rpm <sigh>
>>
>>Comments, anyone know their last compression test on a 2-valve ?
>I'd do that comp test again. Don't know the comp ratio of the VL Turbo (Nissan RB3?)

RB30ET, 7.8 to 1, block height same as the n/a at 9:1, comes down to pistons only, that block
can take some serious boost, well it would have to with such a low CR. The bottom end
has a girdle holding all the caps together, pretty solid - though if you try to
get more than 1200Hp for any length of time the block tends to split between
cyl 3 and 4, wont be going there for a while, couldnt afford the transmission...!

>but 8.5:1 should be around 800KPa,  8.8:1 about 1100KPa. Warm engine, WOT.
>I'd be expecting around 700 KPa.

Geoff ! You jogged me !
Silly me, those f..... units on the gauge, its actually 150psi but peaks at 160,
so that average figure is around 1000Kpa, so its ok then <sigh> <phew> !

mmm, Which is actually a bit strange I guess, unless I have an exhaust restriction
you wouldnt expect it to go above the 7.8:1 now would we... ? mmmm ?

The engine spec data in the service manual states hot compression pressure test
at 1138 kPa standard (n/a 1196) and 834 kPa minimum...

>Does any one have actual data / experience with this engine?
>
>It was easier pre metric. Less than 100 PSI meant spend money.

Yeah true, I'm ok for a while then, cept that tappet growl I just dont like,



Regards from


Mike
Perth, Western Australia
VL Commodore Fuse Rail that wont warp or melt !
Twin tyres for most sedans, trikes and motorcycle sidecars
http://niche.iinet.net.au