The Forced Induction 16V Thread

[mrbeige 0]

a 5 cyl Audi 20vT but i think he was running 2.5-3bar dynamic boost pressure

Shit me, that's a funk load of boost. To be fair I'm not surprised it blew the welds running that :nuts:

[don_stavrou 0]

 

I got this off of the vwsport site, not sure whos car it is, but they running 18psi, 340bhp and the "cut and shut manifold" still looks in one piece. I get what your saying about going down the custom manifold route, but its the same story with everything, like the people who use standard pistons etc..

[Kevin Bacon 5]

I used to run the standard intake manifold on my 16VT and it was a torque monster. I used a schitt turbo, only a crummy little T25, but at 10.5psi, it made 221hp and 230lb ft. Not sure I'd want to run huge boost through the stock fanimold tbh but those long runners + turbo really gave it huge midrange shove. Fell off a bit past 6K though, but that was down to the ickle turbo mostly.

 

16V Ts are incredibly smooth with K jet + piggy back and additional rail of injectors. I miss it tbh!

[boost monkey 0]

 

I got this off of the vwsport site, not sure whos car it is, but they running 18psi, 340bhp and the "cut and shut manifold" still looks in one piece. I get what your saying about going down the custom manifold route, but its the same story with everything, like the people who use standard pistons etc..

 

Nice engine, it's always interesting to see how other people build theirs. 18psi doesn't exactly disprove my point though: welded manifolds may be weaker than stock but they're still metal and still have internal strengths! I just wouldn't trust one but that's my opinion.

 

I used to run the standard intake manifold on my 16VT and it was a torque monster. I used a schitt turbo, only a crummy little T25, but at 10.5psi, it made 221hp and 230lb ft. Not sure I'd want to run huge boost through the stock fanimold tbh but those long runners + turbo really gave it huge midrange shove. Fell off a bit past 6K though, but that was down to the ickle turbo mostly.

 

16V Ts are incredibly smooth with K jet + piggy back and additional rail of injectors. I miss it tbh!

 

You're not allowed back now you have a VRT :lol: Interesting stuff though Cheesonator, any graphs of your old cars at all? that would be ace (you can leave out the morris minor you learnt in :nuts:)

[Kevin Bacon 5]

Yeah but I can have a VRT and a T16, ha ha :D

 

I haven't got any plots of the 16VT because AmD dynoed it back in the day when they were close to Stealth Racing.

 

Actually, I think I may have dynoed on it Stealth's rollers shortly after they got them, so I'll ask Vince if they're still on his computer. This was about 7 years ago, so they may not be :D

[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:

[Yandards 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..

[mrbeige 0]

Been doing some thinking and had a long chat with the Toad-meister last night with regards to what blocks to use/build as a basis for a 16vT. Now, I have in the garage a 2E tall block stripped down ready to be built back up. I was going to adopt the same principle as the Americans do with the ABA block and 16v head. This combination gives you a compression ratio of ~8:1 straight out of the box, as the pistons have a dish and the 16v head has the combustion chamber set into the head. The only other thing you need to do is use the 16v crank pulley, intermediate shaft and pulley, as they differ between the 8 and 16vs.

 

So, following on from that I started thinking about whether it would be possible to stroke the tall block and get some more capacity out of it but still maintain the low compression. The first thought was a TDI crank. The standard stroke on a tall block is 92.8mm and the TDI crank will up that to 95.5mm, then an over bore of 1mm on the block to take it out to 83.5mm. The two together will give you 2092cc. The only issue I can see is the length of the rods. short block ones are 144mm and tall block are 159mm, but as the crank now has an additional 2.7mm, the tall block rods will be too long. I suppose it could be possible to offset bush the pistons, but would it be possible to offset them that much? I'm not sure about this. The only other with would be to see if there are any other off the shelf rods, that are that little bit shorter? I think the short block rods would be too short. Another option i suppose would be to have the block machined so that it is slighly shorter, but again I think there must be a better option.

 

What are the potential gains from going down the stroked turbo route? I would think that it would improve low down torque somewhat? But then would it hamper the engine's ability to rev? Finally I have one more question. Would such a stroked engine really need to have lightened crank/forged rods and pistons? For me it is more of an engineering exercise, so using OEM components is preferable :)

 

Oh and one last thing, it appears from my coversation last night with the Toad-meister that although we both have engineering/sciencey type degrees, Tom couldn't work a calculator and I don't know how to calculate the area of a circle :camp: :lol:

[junkie 0]

I forget which way round but its all about been under or over square on your engine, going long stroke will hamper the revs.

[mrbeige 0]

I forget which way round but its all about been under or over square on your engine, going long stroke will hamper the revs.

Under or over square what dude? Thought as much about the hampering revs, but as I said, could that be offset by using lighter components?

[junkie 0]

Lighter components will rev quicker and allow higher revs more reliably, but im not sure how it will be on an over square engine [stroked]

 

I think over square is stroked, as in the mm measurements on the stroke is greater than the bore diameter.

I think under square is bored, as in the mm measurements are larger on the bore than the stroke length.

 

Or they are the other way round but basically the under square will be high and fast revving naturally and the over square will be lower and slower revving naturally, both give different engine characteristics obviously, what your trying to do is create the best of both engines without the draw backs i suppose.

[mrbeige 0]

basically the under square will be high and fast revving naturally and the over square will be lower and slower revving naturally

So the standard 16v is an 'over-square' engine anyway, you are just making it more 'over-square' :D

 

Still, what would you expect to gain then, when clearly you will be losing the engine's natural ability to rev....which kind of goes against the point of a 16v in the first place??

[dirtytorque 0]

basically the under square will be high and fast revving naturally and the over square will be lower and slower revving naturally

So the standard 16v is an 'over-square' engine anyway, you are just making it more 'over-square' :D

 

Still, what would you expect to gain then, when clearly you will be losing the engine's natural ability to rev....which kind of goes against the point of a 16v in the first place??

 

I'd say.

 

 

The tdi setup you mention would give you a 1.66 rod ratio.(159/95.5)

the tall block setup using the 92.8 crank yields a rod ratio of 1.7.

 

As for what rod ratio is best torque at a particular target rpm band ?

Well for every arguement for one case I seem to be able to find a counter arguement.It seems it's one of those things that is very dynamic depending on other engine variables.

Interesting stuff tho.

:)

 

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..

[mrbeige 0]

The tdi setup you mention would give you a 1.66 rod ratio.(159/95.5)

the tall block setup using the 92.8 crank yields a rod ratio of 1.7.

 

As for what rod ratio is best torque at a particular target rpm band ?

Well for every arguement for one case I seem to be able to find a counter arguement.It seems it's one of those things that is very dynamic depending on other engine variables.

Interesting stuff tho.

:)

 

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?

[Toad 0]

Excellent... Proper engineering debate has begun.

 

Stu. Why not look to find shorter pistons, or offset the gudgeon pin to get rid of the 3mm overlap. or fit spacer gasket and try to balance the C/R somehow. The website with the calculator on helpfully had capacities of the cylinferhead and piston dish. You also need to work out how much your valve reliefs will add to capacity.

[mrbeige 0]

Excellent... Proper engineering debate has begun.

 

Stu. Why not look to find shorter pistons, or offset the gudgeon pin to get rid of the 3mm overlap. or fit spacer gasket and try to balance the C/R somehow. The website with the calculator on helpfully had capacities of the cylinder head and piston dish. You also need to work out how much your valve reliefs will add to capacity.

The valve reliefs shouldn't add capacity, just combustion chamber volume, AFAIK. I was taking to Mrs B last night about all this, and during the discussion I realised that to get the 2092cc I'd need an 83.5mm piston, soooo, I wonder if there is another engine with an 83.5mm piston and 21mm wrist pin that would work. Doesn't even need to be VAG (to be fair I don't think they have anything larger than 82.5mm anyway). Perhaps Volvo or Saab?

 

A spacer gasket could work, but then you are adding undesirable additional weaknesses into the engine, although it is a possible solution.

[Kevin Bacon 5]

Indeed......interesting stuff!

 

3mm is a lot to take up in the bush alone. I'd say you'd need a combination of offset bushing and piston crown skimming. I'd suggest 1mm offset, plus 2mm skim. I know H8RRA skimmed the pistons on his stroked VR6 for the same reason.

But...he reckoned the revs fell off too abruptly past 5000rpm, which is a long stroke trait and worth bearing in mind.

You'd need diesel gearing to go with it imo, otherwise you'll be forever reaching down to upshift when you ran out of gears ages ago :D

 

Good project, especially if can be done by parts bin raiding....

[Yandards 0]

Indeed......interesting stuff!

 

3mm is a lot to take up in the bush alone. I'd say you'd need a combination of offset bushing and piston crown skimming. I'd suggest 1mm offset, plus 2mm skim. I know H8RRA skimmed the pistons on his stroked VR6 for the same reason.

But...he reckoned the revs fell off too abruptly past 5000rpm, which is a long stroke trait and worth bearing in mind.

You'd need diesel gearing to go with it imo, otherwise you'll be forever reaching down to upshift when you ran out of gears ages ago :D

 

Good project, especially if can be done by parts bin raiding....

 

Very interesting topic.

 

Gearbox is an easy one, CTN from a diesel passat 1z engine code estate, very long legged and a bolt on option.

 

As for rod stresses, bore wear etc given that you are going down an FI route I would want to reduce both piston velocity and rod stress, purely for reliability. As for running with lighter pistons and rods this will enable you to run more RPM and counter the effects of the long stroke to an extent; the reason being that the lighter parts allow the dynamic motion of the engine to be overcome faster and less energy is required to accelerate. Piston speed as a figure is fairly meaningless on its own, you need bore size and some weight to work out the problems; image a motorcycle engine piston - this spin up to over 15k in most cases for sports bikes as such the piston speed is massive when compared to a 2l car block. But its the weight and size of the pistons that allow the bike engine to achieve such high speeds. Got a few links to some good articles but not at PC right now.

 

The 16v element (high revving) is purely one of hearsay and rumour, a 16v set-up will usually produce more power and torque than a 8v engine accross the entire rev range, the real difference is that there is a big surge of torque at the 4k mark - unlike the 8v units. As such a turbo'd 16v head will make more than an 8v head, especially when you throw in counterflow (standard VAG 8v) vs crossflow arguments.

[Toad 0]

The valve reliefs shouldn't add capacity, just combustion chamber volume, AFAIK. I was taking to Mrs B last night about all this, and during the discussion I realised that to get the 2092cc I'd need an 83.5mm piston, soooo, I wonder if there is another engine with an 83.5mm piston and 21mm wrist pin that would work. Doesn't even need to be VAG (to be fair I don't think they have anything larger than 82.5mm anyway). Perhaps Volvo or Saab?

 

A spacer gasket could work, but then you are adding undesirable additional weaknesses into the engine, although it is a possible solution.

 

Sorry capacity was indeed the wrong word, I was just thinking of the effect they would have on the C/R.

 

I wonder where we could get a list of bore diameters and pin sizes.

 

Don't need to limit ourselves to 83.5, just something in that region, we'd be using 3rd party pistons and rings so would just need the bore to be machined to that size. Could bushings be made for the pins?

 

If we're taking material off the piston, then the gap between the crown of the piston and the first ring would be reduced, again affecting the C/R.

[boost monkey 0]

Weeheheheelllll, look who drop kicked this thread in the crotch!

 

Engineering = :luvlove: I would comment more but I have a engine dyno lab at the mo (diesel :/ ) and ICBA to go back about 5-6 posts and start quoting stuff.

 

but, undersquare IS bikes, and oversquare IS cars. That's it in a nutshell.

 

Gotta go! :nuts:

[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:

[mrbeige 0]

Oooooh, all this talk is making me wet :lol:

 

Anyhoo, After a quick checkeroo of some standard piston sizes from different manufacturers, it seems the closest to 83.5 I'll get is 83mm, but the problem is the wrist pins are 22mm, which is too big, but then that might well be an advantage if offset bushing is required. Also can you over bore the cylinders to 83.5 and just use oversize rings? I suppose that is only desirable when using forged pistons as they expand considerably more than their cast counterparts?

Indeed......interesting stuff!

 

3mm is a lot to take up in the bush alone. I'd say you'd need a combination of offset bushing and piston crown skimming.

If we're taking material off the piston, then the gap between the crown of the piston and the first ring would be reduced, again affecting the C/R.

Indeed, and 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?

[mrbeige 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

[CTWG60 0]

http://www.motorenteile.mahle.com/eLIZA/app/queryEngine

 

For mahle pistons you can search by spec ie pin dia bore etc. I'd stick to 83mm as 83.5mm weakens the cylinder walls too much so I've been told and .5mm really doesn't give you that much more capacity to be honest.

 

Eurospecsport do 236mm block low comp forged pistons for 16v engines.

 

As far as ring damage!! the closer the piston perimeter gets to the head the better protected they are from heat as the burn of fuel will be more concentrated to the centre of the combustion chamber. The 8v compression lump will actually force the mixture toward the front of the cylinder and cause ring damage.

[Kevin Bacon 5]

Depends how much meat there is in the crown. As I say, it's already been done successfully in the VR6 a few times.

 

I think you're finding problems that don't exist :D