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Discussion in 'A3/S3 Forum (8L Chassis)' started by StaceyS3, Feb 7, 2012.
Bung it together, turn up the boost and be happy!!!
Dropped crank, rods and pistons @ applebee engineering today to be with them a week but all being well will be done by wed morning then will actually start tightening some bolts
Hard to decide which calendar is better.
My only worry with the build progressing so quickly is we won't see the later months
You've got me looking at GTX30's now, wishing. A GT28 seems so inadequate compared.
Andrew are you taking the inlets out to match the gasket? As got some spare time today and could port the Mani to match?
How on earth have you got "spare time" with a new born!
I do prefer the other calendar....don't panic I will always find excuses to post up pics with calendar shots
Gt28 will still be punchy mate and of coarse will make a lovely road car with good response
No it wouldn't
if you know the bore / stroke / head volume, which you should to know the CR in the first place, working out the change from a different head gasket is VERY easy. Just simple maths and a bit of Pie! (Pi)
I've never done it for the A3, as I've not needed to, but I've spent loads of time experimenting with different hardware configurations to give different CR's on my Mini
You can send that if you want
Knew it is simple just volumes but unsure of head volume, as a skim will in effect change this
All it was that I was discussing with a friend about CR's as he's going run a thinner gasket on his c20xe to raise the comp some more and wondered if it was a worthwhile way to possibly increase comp some more on these engines??
Not for myself as will be running N/A gasket regardless due to having 83mm bores but wondered if it was a worthwhile mod for others as people go to the lengths to change from Bam to Agu pistons for 0.5cr then maybe a gasket would be another route to net some gains or an easier route
That'll be brilliant if you dont mind?
Some of the exhaust ports are done spent most of the day yesterday and most of sunday morning doing them, will be finishing them off tonight. I will start on the inlets monday i hope.
Looks wicked mate
Inlet mani's booked to be collected tommorrow and will be with you Tuesday
Not a problem
On another note, I've managed to bed my new rings in and connected the N75 to run full boost. You will be happy with the .82 housing!!
Problem is now it feels like a rocket has gone off when it comes on boost and thats putting out around 440+bhp
ahhh yeh you're right, i thought you might have to work out the combustion chamber volume by taking a mould or something or using gas etc. but you could just rearrange the CR to find it.
weird. im getting a standard combustion chamber volume of 49.4 but that gives a CR of 10!
i think audi do alot of rounding!
how did you measure the combustion chamber
This is one way to do it CCing cylinder heads I never did a guide on cc'ing a head with all the proper gear but the link will give you a idea
well manufacturers CC doesnt include the combustion chamber at all, purely bore and stroke of the block. so pi/4x81^2x86.4x4 would be our capacity which is right as we know.
and CR is: capacity of one cylinder: pi/4x81^2x86.4 plus combustion chamber volume. all over combustion chamber volume again.
thing is manufacturers dont quote EXACT CR. so the 9 we know is rounded down to 9.
Very nice mate glad it's all back and running sound, can't wait to see what yours is capable of and how the gtx performs
Will have a sit down myself when I get a chance and have a read through that link and have a play with some figures
Top work Karl keep investigating
ok I got it, put my head down last night and 55.6 came to me. Took me a while to realise how after being a retard. But
Divide block capacity by 8, can't explain via here, I need to wave my hands around and babble on to explain, this give you the absolute max combustion chamber volume, plug it in and you'l get near as dammit 9.
500.4:55.6 = 9:1 ratio
- your 0.5mm from your stroke (although technically you aren't, but it works) and you can find your new chamber colume and new CR.
Boom. *** 2am that came to me
Another small update, not much of one but every time i get change i will
With a large port head you would think that not a lot of metal would need removing from the inlets but your wrong, if anyone plans to do work on a large port head you need to do lots of work behind the seat to blend them in.
Cheers for keep bringing the updates, did the inlet Mani runners land your end today?
Sorry Karl only just seen your post
Will have a play with some figures when I get a spare few mins
Bit of an update today I've collected the parts from being balanced this morning (will upload pics in next few days) changed front drop links, sent the liquid off for a software update as really fancy using the multigauge on the Bedford track day and last but not least been pissing around with another part which has resulted in it being broken but am not dissclosing details until it's replaced or repaired
I think i will have to send my liquid off for a update as the peak power only goes to 450 ish?
Can anything be changed on the liquid if needed?
I had a quick breeze through the updates and the software seems to have moved on quite a bit since I last looked and from when I bought the liquid around start 2010 so should be more gadgets and bits n bobs to play with
Also when speaking to Jim the turnaround is really quick for the updates so was a no brainer.....I should be getting it back latest Monday....result
I think i'll get mine sent off then
i forgot to add, increase in CR of .35 by reducing the gasket 0.5mm. assuming both gaskets compress the same.
and i think its an easy and feasible way of doing it too. afterall its whats done when charging an N/A engine alot of the time, fitting a thicker gasket.
so you're fitting an N/A gasket then? what bore are they?
Yeah I'm fitting an N/A gasket as standard gasket allows up to 82.5mm bore but N/A allows 83mm which is what I'm running
IE do sell an overbore gasket that is standard thickness but is $100 compared to Â£20 odd N/A
Just thought it was another viable way to raise comp (not for myself) but for peoples trying to eak every last drop out of smaller turbos and comp has seemed to be one of the biggest shouted about contributors to making good power (although is subjective) but this could be another step closer to a 10.1 ratio
You going to be the guinea pig
Good work Karlos, I said it wasn't that hard, but I wasn't prepared to sit down and do it myself, so good on you for being bothered!
I was thinking earlier, do you think the factory CR calc is purely head volume and cylinder volume derived? or do you think they are taking the gasket into account in the calc too?
Would have thought gasket would have been taken into account as wouldnt be a true CR? also iirc there is 3 different headgaskets for the 1.8t....I wonder if any of them are different?
chamber volume is inclusive of the head gasket. that seems to be for all manufacturers. if not, there claimed CRs will be way out.
yes stacey il be a guinea pig lol. if i can get some 9.5:1 pistons and an N/A head gasket il be 9.85:1. a manufacturer would prob class that as a 10:1 ratio. Like i said, they seem to round it off, so my calcs are all based on the maximum values of capacity, giving as close to the manufacturers claimed CR.
So above the max volume of our combustion chambers is 55.6cm^3, which gives us the lowest CR close to 9.
its accurate though, because you can get the changes as a percentage. Essentially it doesnt matter if my calcs are a bit out, as long as we can say decreasing/increasing by X% increases CR by Y%.
so for my calcs, decreasing the head gasket, and the capacity of the combustion chamber (Vcc) by 0.5mm is a decrease by 4.24%
And it seems that any decrease in Vcc increases CR by a factor of 8.
decrease Vcc 1%, CR increases 8%
Did you measure the volume of the dish in the pistons in the calculation?
that would be near impossible for me to do.
my Vcc is inclusive of piston, headgasket, and head. thats for all Vcc measurements.
i could take into account lower comp pistons, calculate the Vcc with them, and compare the higher comp Vcc and that would give a change in piston dish area. seeing as pistons would be the only variable
So, i understand you didn't take a physical measurement of the combustion chamber but deducted it from the unitary displacement and CR yea?
Want to say cheers to Karl for putting the effort in with the comp ratios and how a headgasket will change this as I didn't get round to it and saved me the effort
Little update I have picked internals up from the eng firm (who were probably down the worst road I've ever been down) that done the balancing and its pretty surprising how much have had to remove to get them all to identical weights
They had to take a tiny bit off of one of the small ends as the rods were balanced end to end
Big ends where can see 3 have been ground on the 45 degree part
Pistons which were surprisingly more uneven weights than I thought they'd be
Closer shot of the piston they removed the most material off
Crank factory balancing drill holes
The material they removed to balance
I then started prepping the block a bit more giving it a thorough clean after all the machining, followed bolting on a couple of bits and bobs but nothing to interesting
I did then find that one of the bearings had a couple of nicks in it creating a couple of burrs which a little bit of attention with a needle file sorted
I also had a few issues with a rear tie bar but have to say forge customer service has been excellent and they sent me a new set to replace them and will return the old ones to them
Rather cold changing them last night and of coarse dark
Whilst the car was off the road for two days I attacked a couple of other issues....downpipe studs that had wound there self out....again
I changed the front drop links which has got rid of an annoying clonk that has been present for ages which also partially influenced me changing all my front bushes
I had got down to the point I only had 1 interior led working (like a strobe) so checked them to find that a lot of them had died but the festoons had got a bit hot and distorted causing the resistor to not make contact with the end cap
Just moved it round to the other side, refitted the cap and all works again but the littler LEDs for map reading lights are all RIP
Last but not least an embarrassment (cowboyed pikey) heatshield for Bedford knocked up very quickly with tinsnips, bit of steel and a jubilee clip....cue abuse lol
Considering going for the Tuscan rods in my build. Probably worth building a solid block first time and save the effort later eh?
Nice one for wearing gloves, can't believe the amount of mechanics that don't bother.
Can't see any problems with other rifle drilled rods but did get a little carried away when was ordering from IE and went for the tuscans
I never used to wear gloves but there's a lot of chemicals where I work and developed quite bad dermatitis so is a necessity now to prevent it getting to bad
heatshield looks great!
have fun at bedford