Compression Ratio

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Compression Ratio

Postby Muppet » Tue May 22, 2012 9:02 pm

Evenin all

got a techy question

if I have my ABL 1.9td bored to fit a set of oversized Pistons, what effect
would that have on the Compression ratio?

Would there be any useful effect on power output?

Info
original Piston 79mm
Stroke Length 95.5mm
Bore size 79.5mm

O/S piston 79.5mm
Not sure what size Bore would be poss 80mm

cheers
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Postby Globbits » Tue May 22, 2012 9:24 pm

Oversized = slightly bigger capacity = slightly lower compression

But slightly sounds like about 0.5% so I don't see it being a major issue. You might find it a teeeeeeeny bit more awkward to start on very cold mornings, and the low-end torque might be ever so slightly down. But if you notice the difference at all (bearing in mind you're going to have a better ring clearance than you had before, meaning a better seal/compression) I'll be surprised
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Postby Muppet » Tue May 22, 2012 11:03 pm

Just wondered

Didn't think it was gonna make a whole lot of difference
will be thinking of the Rover Pin Mod while at it.

hows the outlook for Mertle?? Has the Lip retracted yet??
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Postby regcheeseman » Wed May 23, 2012 12:44 pm

no - not the BS rover pin mod. don't believe what you read on the net.

I trust you are running an AAZ pump? In which case it's highly likely that any taper on the pin will remain unused as other pump restrictions will stop it adding any fuel.

Give me your pump..... I'll sort it if you want.

Gov mod, ground pin , re sealed and a few other tweaks :wink: It'll give you enough fuel for 150 brake and 30+psi (if you wanted it and the rest of the motor was up to it)
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Postby Muppet » Wed May 23, 2012 7:17 pm

regcheeseman wrote:no - not the BS rover pin mod. don't believe what you read on the net.

I trust you are running an AAZ pump? In which case it's highly likely that any taper on the pin will remain unused as other pump restrictions will stop it adding any fuel.

Give me your pump..... I'll sort it if you want.

Gov mod, ground pin , re sealed and a few other tweaks :wink: It'll give you enough fuel for 150 brake and 30+psi (if you wanted it and the rest of the motor was up to it)


hi ya

might come knocking. I have my original ABL pump as aswell as another that i'm not sure what its from, has full electronic hook up on it??

Van running an AAZ I think bit vague on history and numbers not easy to see.
just wanna give it a little more chance of getting up those damn Devon hills. not hoping to
blow the nuts off of anything at the lights, cause I'l get it in the neck for leaving
all the cups and plates in the sliding door step.

Well i started out well today by Buying an Engine Stand :D :D
happened to be in Plymouth and knew there was a Machine Mart down there.
some what better built than the pile of Metal and Mig spatter that I had started.

If i was thinking 150 i'd be needing that Crank Gurdle you were showing a bit back. But think thats a bit extreme for our Bus
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Postby Globbits » Wed May 23, 2012 8:21 pm

Mr Cheeseman is right - the boost pin did make a difference, but not an awful lot. Unfortunately, she's belched out a load of oil from her breather, so I have a suspicion I'm due an engine replacement :(

Have just bought a Mk3 Golf TD donor though, so Reg, expect a call shortly :wink:
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Postby regcheeseman » Thu May 24, 2012 12:21 pm

I have my original ABL pump as aswell as another that i'm not sure what its from, has full electronic hook up on it??


Could be a late AAZ pump - easily sorted - could even build you a hybrid ABL/AAZ pump if wanted.

Have just bought a Mk3 Golf TD donor though, so Reg, expect a call shortly


No problem - happy to help
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