The Forced Induction 16V Thread

[CTWG60 0]

a 95.5mm crank only affects piston deck height by half the stroke difference ( 95.5-92.8 )/2 = 1.35mm. So if you used a slightly thicker head gasket you could rid yourself of this extra height or when you have the pistons valve clearanced you could have the compression lump ground off which doesn't help combustion on a 16v head, they are usually around 0.89mm so you only then have to deal with .45mm of extra piston height which would nicely bump up your CR to around 8.7-9:1. :salute:

Hmmm, I'm liking the sound of that. So if you are using the 2E pistons, that have a cross-section of ------\______/------ as opposed to being flat like the normal 16v ones, would that be worse for the combustion or would it be better to get some 9A pistons and machine some of the piston crown off as required to get to 8.5-9:1 compression instead, or stick with the 2E pistons and get them valve clearanced

 

If it were me I'd either

 

a: clearance the current 82.5mm pistons and remove the compression lump and fit the 95.5mm crank with new diesel bearing shells. quick and dirty method

 

or

 

b: buy good quality forged pistons that are made for the job and have the bottom end rebuilt with forged rods and have everything balanced at the same time. Do it once and do it right method. :D

[Kevin Bacon 5]

[Do it once and do it right method. :D

 

:salute:

[CTWG60 0]

OK I have a spread sheet for this sort of thing and just quickly punched in the numbers in. And simply removing the compression lump from the 2E pistons means you would have a 0.000000 piston to head clearance :D with an ABF head gasket of 1.65mm thickness so you would need to take another .6mm out of the piston compression height. So anyway if you did this on the stock 82.5mm pistons you'd have a CR of 8.95:1 on 83mm pistons you'd get 9.044:1 CR. By the way a 95.5mm crank on stock pistons would only get you to 2042cc is it worth it? 83mm gives 2067cc.

 

You can get a 1.9mm metal head gasket so I've read which means you wouldn't have to take as much out of the pistons.

 

I'd say stick to the standard crank to be honest unless your curious to see what you can achieve, like myself! :lol:

[dirtytorque 0]

Generally..

I was always under the impression that a high rev engine benefited from a slightly larger rod ratio.Less bore wear due to smaller rod angle,less stress on rods due to slower pistons speeds.Smaller dwell angle helping cylinder filling at higher rpm..

You see, this is the problem, as you say, it's one argument against another. I'm not overly convinced that it would actually be possible to use the longer rods from the tall block as this would take the standard pistons above the deck of the block by around 3mm, so with that in mind the shorter 144mm rods would then yield a rod ratio of 1.5, which isn't particularly ideal. As you say, with the lower rod ratio the piston dwell would be less, more stress on the rods and a much faster piston speed. But...does this resultant poorer cylinder filling matter so much when forcing the air into the cylinders?

 

fair point but you would still want things to be in harmony as much as possible anyway.

i.e if your turbo is coming to life at 3.5krpm and your cam profile aids high end breathing then your going to want a bottom end that aids air ingestion further to the right of the guge so to speak.?!?!?!

 

This is all just talk.

I'd love to have a massive part bin and the time to try all different manner of things to see where perfomance gains could be had etc with different mods.

*sigh..*

[mrbeige 0]

OK I have a spread sheet for this sort of thing and just quickly punched in the numbers in. And simply removing the compression lump from the 2E pistons means you would have a 0.000000 piston to head clearance :D with an ABF head gasket of 1.65mm thickness so you would need to take another .6mm out of the piston compression height. So anyway if you did this on the stock 82.5mm pistons you'd have a CR of 8.95:1 on 83mm pistons you'd get 9.044:1 CR. By the way a 95.5mm crank on stock pistons would only get you to 2042cc is it worth it? 83mm gives 2067cc.

 

You can get a 1.9mm metal head gasket so I've read which means you wouldn't have to take as much out of the pistons.

 

I'd say stick to the standard crank to be honest unless your curious to see what you can achieve, like myself! :lol:

Interesting! I think I'm a bit of a fiddler to be honest :fondle: and the engineer in me is curious to see what can be done without spending shed loads. I like the quick and dirty method. It's not as if I will be driving it every day, more for the tinkering aspect :D

[mrbeige 0]

fair point but you would still want things to be in harmony as much as possible anyway.

i.e if your turbo is coming to life at 3.5krpm and your cam profile aids high end breathing then your going to want a bottom end that aids air ingestion further to the right of the guge so to speak.?!?!?!

 

This is all just talk.

I'd love to have a massive part bin and the time to try all different manner of things to see where perfomance gains could be had etc with different mods.

*sigh..*

Wouldn't we all, but I think I might have to give it a go to see what happens. Given that the idea is to use standard/OEM parts, then to build a block isn't going to cost the earth, so why not give it a whirl? The tried and tested approach isn't always the best....

 

I think if you can still utilise the longer rods, then the compromise will not be too great and the longer stroke should improve low down torque. Maybe that combined with the 16v equivalent of schimmel 263s? In fact that's another good question. Camshafts...

 

From what I can gather, ABF cams seem to be the optimal arrangement for turbo applications. They are the same duration as the KR ones @ 254deg, but have more lift, thus aiding the cylinder filling (10,76int/10,73exh mm for the ABF and only 9,2int/10,21exh mm for the KR) They also have less overlap (2deg for ABF and 6deg for KR), again better for the turbo application.

[Yandards 0]

Link to piston speed article here and advantages of 16v heads vs 8v heads.

[Toad 0]

OK I have a spread sheet for this sort of thing and just quickly punched in the numbers in. And simply removing the compression lump from the 2E pistons means you would have a 0.000000 piston to head clearance :D with an ABF head gasket of 1.65mm thickness so you would need to take another .6mm out of the piston compression height. So anyway if you did this on the stock 82.5mm pistons you'd have a CR of 8.95:1 on 83mm pistons you'd get 9.044:1 CR. By the way a 95.5mm crank on stock pistons would only get you to 2042cc is it worth it? 83mm gives 2067cc.

 

You can get a 1.9mm metal head gasket so I've read which means you wouldn't have to take as much out of the pistons.

 

I'd say stick to the standard crank to be honest unless your curious to see what you can achieve, like myself! :lol:

Interesting! I think I'm a bit of a fiddler to be honest :fondle: and the engineer in me is curious to see what can be done without spending shed loads. I like the quick and dirty method. It's not as if I will be driving it every day, more for the tinkering aspect :D

 

It's just interesting to work out what could be achieved through OE parts, a bit of engineering and some imagination. Really the only VW parts that need to be used are the head, block and crank. Everything else could potentially come from other marques, that's what I am most interested in.

 

Useful info there Chris.

[Toad 0]

wouldn't removing too much material from the crown also give issues with cooling and mean that the top rings would indeed get hotter and thus be more inclined to fail?

 

I don't know how big an effect the 16v oil squirters would have?

 

I'd have thought that the piston could cope with a mm or two being taken off, the oe units were built with durability in mind, just might need to keep any pinking tightly under control.

[mrbeige 0]

Link to piston speed article here and advantages of 16v heads vs 8v heads.

That makes very interesting reading! A quick calculation shows the follow piston speeds.

RPM     92.8mm     95.5mm
1500     913.39    939.96
2000	 1217.85	1253.28
2500	 1522.31	1566.60
3000	 1826.77	1879.92
3500	 2131.23	2193.24
4000	 2435.70	2506.56
4500	 2740.16	2819.88
5000	 3044.62	3133.20
5500	 3349.08	3446.52
6000	 3653.54	3759.84
6500	 3958.01	4073.16
7000	 4262.47	4386.48

 

Now I don't see a particularly huge difference there. Both the standard crank and the TDI crank result in piston speeds are just above the limit (as per Bill :) ) of 4000 ft per minute for any engine.

[Toad 0]

I think if you can still utilise the longer rods, then the compromise will not be too great and the longer stroke should improve low down torque.

 

As we were saying on the phone earlier. If you use a big rod ratio, and accept the compromise of a lower max rpm, for better low end torque, then you would achieve a lower max bhp, which would mean you could run a far smaller turbo, which would spool and achieve peak boost far sooner, this would accentuate the low end torque. Would potentially be a far more usable weapon.

[boost monkey 0]

like a tdi.

[CTWG60 0]

It's just interesting to work out what could be achieved through OE parts, a bit of engineering and some imagination. Really the only VW parts that need to be used are the head, block and crank. Everything else could potentially come from other marques, that's what I am most interested in.

 

Well that was my initial plan with the 220mm block 2008cc >9:1 CR 8v engine I'm very close to fitting, but I ended up getting custom length forged rods made to make it all work (in theory) just got to fit and put the theory to the test. :D Got myself an EGT probe so I can keep an eye on it! 8)

[mrbeige 0]

Got myself an EGT probe so I can keep an eye on it! 8)

Are you integrating that into your management, or is it for a read back from a dial only?

[Toad 0]

It's just interesting to work out what could be achieved through OE parts, a bit of engineering and some imagination. Really the only VW parts that need to be used are the head, block and crank. Everything else could potentially come from other marques, that's what I am most interested in.

 

Well that was my initial plan with the 220mm block 2008cc >9:1 CR 8v engine I'm very close to fitting, but I ended up getting custom length forged rods made to make it all work (in theory) just got to fit and put the theory to the test. :D Got myself an EGT probe so I can keep an eye on it! 8)

 

How close are you to having your car finished then?

 

How far out would your C/R have been with oe rods, or could you not get anything suitable?

 

Out of interest, could a tallblock be machined shorter to suit?

[dirtytorque 0]

It's just interesting to work out what could be achieved through OE parts, a bit of engineering and some imagination. Really the only VW parts that need to be used are the head, block and crank. Everything else could potentially come from other marques, that's what I am most interested in.

 

Well that was my initial plan with the 220mm block 2008cc >9:1 CR 8v engine I'm very close to fitting, but I ended up getting custom length forged rods made to make it all work (in theory) just got to fit and put the theory to the test. :D Got myself an EGT probe so I can keep an eye on it! 8)

 

 

A real home brew engine this.iIcan't wait to see how this performs.Now bugger off to the 8v thread where u belong. :lol:

[junkie 0]

 

A real home brew engine this.iIcan't wait to see how this performs.Now bugger off to the 8v thread where u belong. :lol:

 

And as we all know it is truly the only worthwhile thread to be involved in on this forum lol.....

 

Rob regarding the rod ratio.

 

My 1900 conversion is achieved by the usual 83mm bore, the rods though are 144mm 16v/20v rods as opposed to the G60 139mm i think they are, i never knew why but recently read somewhere that due to a longer rod and shorter pistons the forces or less on the cylinder bore walls so less stress on them and less chance to pop a piston through the wall.

 

So my question is do i have more, less or the same rod ratio and apparently the piston can be designed better using the longer rod but whether thats for strength or something i do not know any ideas dude?

[boost monkey 0]

You're way more likely, logistically speaking, to throw a rod (than a piston) through a bore wall Si!

[CTWG60 0]

EGT is just a heads up readout to let me know that things aren't going horribly wrong, :eek: sticking with standard management for the time being.

 

I wanted a standard looking engine bay with as many parts internally and externally remaining VAG as possible.

 

The thing with a 220mm block 8v's and the 92.8mm crank is that you only have 30cc in the head and so you have to find another 30cc'ish to get your compression below 9:1 and if you want to stay with cast pistons like I did then you have to give more room for the piston. Also changing the deck height of a 236mm means that the valve timing would need playing with and the brackets for the alt and G60 would need to be customised for the extra height of the block so I did it the expensive way and changed the rod length to suit the block pistons and crank. I knew that VW had used 141mm rods in the early mk4 2.0l 8v which gives quite a low rod ratio but the low end torque would be picked up, also the CR is just what I wanted at around 8.8:1 The pistons are cast so no worries about piston slap on cold starts and oil usage and they have that nice little compression lump to push the mixture toward the spark on the 8v head. :D It's the little things. :grin: To make the engine run smoother with the low rod ratio I didn't lighten the bottom end or flywheel at all but did get them finely balanced.

 

I think a tall block machined shorter would be a possibility but the pistons I used came from a tall bock (236mm) Audi engine that was N/A but only had a CR of 9:1 I don't know if they sold it in this country but I never did figure out why they did an N/A engine in 1995 at 9:1 real wierd! :shrug: :scratch: So anyway if you had a 236mm block and you wanted low comp cast pistons for an 8v head you could just fit the ones I did straight out the box, so to speak!

 

Engine should be ready to go in if not this weekend then maybe next weekend if I can get a day off from being a daddy and working. :)

 

But then I have to run it in and get it mapped, I don't think I'll stay for the rolling road map though I could not stand listening to an engine I specced/designed getting readlined. :pale:

 

EDIT: All my knowledge and understanding comes from this forum, books and from talking to people who know their schitt! I'm not an engineer and have no qualifications in anything other than construction! :D :eek: :ignore:

[junkie 0]

You're way more likely, logistically speaking, to throw a rod (than a piston) through a bore wall Si!

 

Yes true dude thats what i meant lol

[boost monkey 0]

I'd be impressed if you managed it though :nuts: :notworthy:

[junkie 0]

If anybody is going to do it then its going to be me lol.

[boost monkey 0]

When you were just a whipper snapper right?

 

We're modelling screw pumps this term, I'm sorely tempted to ask if I can model a G-lader :norty:

 

Do it, could do with some nice computer flow info for a G60..

 

 

Not allowed to, have to do a screw compressor type water pump. Lame :|

 

@Stu, since when are feet per minute useful units of speed? :hitler:

[Kevin Bacon 5]

EGT is just a heads up readout to let me know that things aren't going horribly wrong, :eek: .

 

Awesome, let's pick up on this...... not teaching anyone to suck eggs but I'm a big fan of EGT! It's a clear window into what you're engine is up to.

 

EGT is an absolute must for turbos imo! Well, look at the Audi TT 1.8T engine, even that has EGT contingency fuelling.

 

Ideally though, you want CHT + EGT (Cylinder head temp + exhaust gas rah rah rah). If you want a superior knock indicator, look no further. If your CHT rises rapidly and your EGT drops equally fast, you know you are pinking.

Sometimes you can't hear pinking over rev and exhaust noises, which is where these measurements are handy, like gassing it hard in top gear on the motorway with the window open toking on a fag :lol: . The problem is CHT doesn't react particularly fast, so you really do need to be on the ball to make the most of it. EGT though, reacts WAY faster than any knock detector.

 

Knocklinks et al are all well and good if they're tuned into your engine's specific detonation resonant frequency, but a lot of the time they're not. They pick up too much peripheral noise. That is why standalones don't have knock detection.

Sure, knock algorithms are the hardest maps to write, but race engines run on the edge of knock for peak power. They certainly don't want knock detectors pulling timing mid bend cause they're confused by rumble strip vibration. Knock control was implemented purely to stop dear old Mable flooring her Micra in 5th at 10mph buggering up the engine. Racers know exactly when to expect knock and drive round it, aswell as adjusting fuelling and timing on the fly with their clever steering wheels.

 

I treat EGT as an indication only, so I mounted mine after the turbo. I know the most accurate picture is when it's mounted in the manifold where all the runners converge, but being the cautious type, I don't want an EGT probe breaking off and taking out the turbine wheel.

 

Anyway, rambling over..... just my 2p :D

[dirtytorque 0]

 

Knocklinks et al are all well and good if they're tuned into your engine's specific detonation resonant frequency, but a lot of the time they're not. They pick up too much peripheral noise. That is why standalones don't have knock detection.

Sure, knock algorithms are the hardest maps to write, but race engines run on the edge of knock for peak power. They certainly don't want knock detectors pulling timing mid bend cause they're confused by rumble strip vibration. Knock control was implemented purely to stop dear old Mable flooring her Micra in 5th at 10mph buggering up the engine. Racers know exactly when to expect knock and drive round it, aswell as adjusting fuelling and timing on the fly with their clever steering wheels.

 

I treat EGT as an indication only, so I mounted mine after the turbo. I know the most accurate picture is when it's mounted in the manifold where all the runners converge, but being the cautious type, I don't want an EGT probe breaking off and taking out the turbine wheel.

 

Anyway, rambling over..... just my 2p :D

 

Hmm..Interesting.

In my experience there is a fine line between a knockless engine and a gutless one.I fink I need more practice. :)

I want to integrate EGT with MS but I am waiting for them to release their General purpose input/output board which has EGT provision.

At the moment as you suggest I am driving around Det.In fact it dosn't pink that easily.Its just at lowish RPM under high very high load,i.e going up a steepish hill in a high gear.I have been doing this deliberately to try and load up the engine to tune det out.But as i say there is a fine line to a nice det free engine and one that just doesn't pull as hard.

I'll have to check out the MS website and see if they are near completion of said input/output board.

It would be useful to see the EGT's in my logs.

 

Interestingly enough though in some areas I have come to appreciate that less timing is more anyway..