Ross Autech

Sam said:
Did you put a piston side by side with a 16ve?
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Narp.

By my calculations the 1mm higher deck height adds 6cc to the piston. Which is roughly the dome volume of a vzr piston iirc.

Autech must have a hella tight quench zone in the head...

Only downside to my block is it has det rash around the top of one of the cylinders. Its not fatal imo, and probly a result of the terrible map i have
 
RAJackson said:
Narp.

By my calculations the 1mm higher deck height adds 6cc to the piston. Which is roughly the dome volume of a vzr piston iirc.

Autech must have a hella tight quench zone in the head...

Only downside to my block is it has det rash around the top of one of the cylinders. Its not fatal imo, and probly a result of the terrible map i have
Click to expand...

Did you not have another block?

I plan to get on track too the N1 isn't built for drag :)
 
Going great guns there Ross. Well done mate. I'm sure you'll feel the difference with that crank in place. I remember taking an 8CW out for long Steve and it weighed an absolute ton. They were used as they were easier to balance than the 4CW crank (originally). Hence the term 'fully balanced' when people refer to them.
 
Fooking sweet progress there bud nice to see the bits of the Autech engine I didn't take out ;) she's gonna run like brand new :)
 
Good Job Ross.. was any work done to the 4CW crank before fitment?

Im guessing you have alternative transport whilst this is off road... bottom end aside any plans for head upgrades
 
Nice findings... i'd like you to check something for me before you call me wrong, i had measured a few cylinder heads to come to my conclusion of the headskim.

At this stage, your picture isnt definative enough.

Can you measure the distance from the centre of the wrist pin to the top of the piston please, on both pistons.

Assuming what you are saying is correct about these autech pistons having a 1-1.5mm taller height, you are implying stock DE pistons have a piston to deck clearance of 1- 1.5mm??

That doesnt ring true with me, its more like 0.5mm max.
 
Spook said:
Going great guns there Ross. Well done mate. I'm sure you'll feel the difference with that crank in place. I remember taking an 8CW out for long Steve and it weighed an absolute ton. They were used as they were easier to balance than the 4CW crank (originally). Hence the term 'fully balanced' when people refer to them.
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I've always wondered the reason why both were used and it wasn't just the 4cw instead. Keep seeing people say 'the 8CW is better balanced'....a rotating component is either balanced or not, no two ways about it!
 
Dale said:
Nice findings... i'd like you to check something for me before you call me wrong, i had measured a few cylinder heads to come to my conclusion of the headskim.

At this stage, your picture isnt definative enough.

Can you measure the distance from the centre of the wrist pin to the top of the piston please, on both pistons.

Assuming what you are saying is correct about these autech pistons having a 1-1.5mm taller height, you are implying stock DE pistons have a piston to deck clearance of 1- 1.5mm??

That doesnt ring true with me, its more like 0.5mm max.
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Nope. Cause the bottom end is together and i aint pulling it apart again.

I put the pistons side by side, the rr top ring in the top ring gap on the autech piston. The pins were level, as were the bottom of the rods.

A stock de has a piston deck clearance of 1mm, for both de and det pistons. And to put this into theoretical proof, find a compression ratio calculator and punch in all the info,

86mm bore, 86mm stroke, 0cc dish/dome. 1.2mm compressed hg thickness, and a 1mm deck height brings out 10:1 compression ratio using the combus chamber cc figures i got from you. Do the same for an autech, yeah you get 11.5:1, however, you now cant ignore the fact there are 6cc more piston, no deck height.
 
5Zigen_Eddie said:
Good Job Ross.. was any work done to the 4CW crank before fitment?

Im guessing you have alternative transport whilst this is off road... bottom end aside any plans for head upgrades
Click to expand...

Nah just a stock gti crank. The 7lbs loss is nice enough. Takes my total crank weight loss up to 20lbs...

No alternate transport, just walk or bus.

No head upgrades apart from intake port matching
 
I cant get any of this to check out. What numbers and calculator are you using Ross?

I use this one http://www.csgnetwork.com/compcalc.html

If i plug the numbers of a 1mm piston to deck clearance into 10:1 DE specs, i get this:
Bore: 86mm
Stroke: 86mm
HG Bore: 87mm
HG thickness: 1.2mm
Combustion chamber CC: 46.5cc
Piston Volume: 0
Piston to Deck Clearance: 1mm

= 9.4:1CR


If i plug the numbers of a flush deck, which is Ross' Autech theory im getting:.

Bore: 86mm
Stroke: 86mm
HG Bore: 87mm
HG thickness: 1.2mm
Combustion chamber CC: 46.5cc
Piston Volume: -0.5cc (accounting for valve reliefs)
Piston to Deck Clearance: 0mm

=10.23:1CR


Neither of these are even close?

.......................................................................


The thing that bugs me is that i cant get this bang on 100% with my own theories.

Here's what i mean, its much closer, but still not perfect:

These are my 10:1 DE stats

Bore: 86mm
Stroke: 86mm
HG Bore: 87mm
HG thickness: 1.2mm
Combustion chamber CC: 46.5cc
Piston Volume: 0
Piston to Deck Clearance: 0.05mm

=10.26:1CR


My Autech headskim Theory

Bore: 86mm
Stroke: 86mm
HG Bore: 87mm
HG thickness: 1.2mm
Combustion chamber CC: 40cc
Piston Volume: -0.5cc
Piston to Deck Clearance: 0.05mm

11.42:1CR
 
I thought it was always believed they were hi-compression forged pistons?
Anyway, my calcs were:

Bore (mm) 86.00 mm
Stroke (mm) 86.00 mm
Displacement (cc) 499.56
Cylinders (qty) 4 qty
Displacement (cc) 1998.23 cc

Gasket Bore (mm) 86.50 mm
Gasket thickness (mm) 1.20 mm
Gasket Volume (cc) 7.05 cc

Deck Clearance (mm) 0.05 mm
Deck Clearance Vol (cc) 0.29 cc

Piston Volume (cc) 4.75 cc

Head volume (cc) 45.00 cc

BDC Volume (cc) 547.15 cc
TDC Volume (cc) 47.59 cc


Compression Ratio 11.50 :1


Deck clearance is meant to be 0.05mm, its not a typo. I cant remember where I found all this info as it was a couple of years back. Assuming the highport head was the same as any other with a volume of 45cc, i just changed the piston volume to get the desired CR as I think at the time I was trying to work out what the pistons were. I had N1s down as being 8cc and 16VEs as 6cc
 
sri_alan said:
I thought it was always believed they were hi-compression forged pistons?
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It was a myth though Alan, like the majority of the Autech internals.

The Autech piston is perfectly flat, with 1mm deep valve reliefs. It not a high comp piston. Its not a domed piston like the 16VE ones.

Because of the valve reliefs, the Autech pistons are slightly lower comp than (10:1) UK GTi pistons.

All Ross has done is confuse matters again for other people and frankly i didn't appreciate being called wrong, more so because he put it so bluntly, so lets cut this nonsense about a taller compression height/high comp pistons.

The RR piston has a shorter top ringland than other DE pistons. Thats why people say they aren't as strong as the Non RR motors when being turbo'd. The compression height (height from wrist pin to piston deck) is still the same though, and thats becuase the wrist pin is moved. Ross made the mistake of lining up the top compression rings on both pistons, instead of measuring from the wrist pin.

The one thing i can take away from this though is that Ross has confirmed no oil squirters, which was just another myth.
 
isn't there a way to calc comp ratio from a given psi reading? as in 499cc's of air at 1bar needs to be compressed bleh times to have bleh pressure

so say a given cylinder pressure is 180psi, take away 14.7psi for atmos pressure which gives 165.3psi then divide that by 14.7 which would give a 11.2:1 comp ratio?

or am i just talking nonsense lol
 
Dale said:
It was a myth though Alan, like the majority of the Autech internals.

The Autech piston is perfectly flat, with 1mm deep valve reliefs. It not a high comp piston. Its not a domed piston like the 16VE ones.

Because of the valve reliefs, the Autech pistons are slightly lower comp than (10:1) UK GTi pistons.

All Ross has done is confuse matters again for other people and frankly i didn't appreciate being called wrong, more so because he put it so bluntly, so lets cut this nonsense about a taller compression height/high comp pistons.

The RR piston has a shorter top ringland than other DE pistons. Thats why people say they aren't as strong as the Non RR motors when being turbo'd. The compression height (height from wrist pin to piston deck) is still the same though, and thats becuase the wrist pin is moved. Ross made the mistake of lining up the top compression rings on both pistons, instead of measuring from the wrist pin.

The one thing i can take away from this though is that Ross has confirmed no oil squirters, which was just another myth.
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Easy dale. I never actually said you were wrong... Just the head skim theory. Which was the theory even before you pulled your head off.

As far as i was aware... Non rollers are 9.5:1 with dished pistons...

But to be perfectly honest, i couldnt give a fuck about rumors or whatever anymore cause i have lost interest in the car tbh
 
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