Starting to sound good. Getting deeper into the theory and the how to is what I'd like to know more about.

THere are a couple of places that have done work with the cam for the G16B but one of the issues with it is the variable rocker ratio and there are physical limits on what lift can be had with the cam.

I know you're talking about a stroker but I wonder about the Rod Ratio. I'd like to discuss the pros and cons of say a 78mm big bore instead. A low boost turbo would be interesting to look at too.

Here's our starting point

D'OH Metric

    95hp  |removethispart|@ 5600rpm
    98ft/lb|removethispart|@ 4200rpm


AHHHHH

Thats more like it....

Zag

OK, so lets have a look at a couple things. The G16 (1590cc) has a bore of 75mm and a stroke of 90mm and a rod length of 139.5mm. The consensus seems to be that an ideal rod ratio would be in the vacinity of 1.65 to 1.8 and 1.5 is the lowest that you would look at for a general motor. The G16 has a rod ratio of 1.55 (139.5/90) so it's pretty close to the limits. At a ratio of 1.5 using the stock length rods you would have a stroke of 93mm. So, 75mm bore and 93mm stroke would give a new capacity of 1644cc, an increase of 54cc.
My thoughts are that with a 78mm bore (Miata pistons and sleeves) and stock stroke the rod ratio gets no worse and you have new capacity of 1720cc which is an increase of 130cc. Of course you could always do both so you would have 78mm x 93mm giving a new capacity of 1778cc which is starting to get up there. While we're at it as have a nice alloy head we could lift the compression ratio from 9.5:1 to say 10.5:1 which would give a nice boost. We could also lift the comp. ratio while keeping the stock bore by using Honda D15/D16 pistons (same bore and piston pin dia.) as they use G16 pistons to lower their comp. ratio for use with turbos.
What sort of stroke and compression ratio were you thinking of if keep it NA? As to the turbo side of things what sort of comp. ratio and boost pressure did you have in mind? I love this topic as it's making me think and learn more about options on how to build an engine.

Man CJ

     This is the homework I hadn't got to yet............but off the top I'm leaning 1 or 2 ways

1) N/A
a) Long Block
- .030" overbore (approx .75mm)
- stroke increase to be determined, but done by offset grinding existing crank (1-2mm?)
- Stock pistons machined for clearance
- "0" deck height block/piston clearance (yeah I know it will become an interferance engine
- rods TBA
- Ports matched only
- Seats back cut
- Valve bowls pocket ported
- 3 angle grind, valves back cut
- head surface machined .030"

- custom cam...TBA

- This should take us to about 1635cc
- c/r approx 10:1

b) Intake system will need to be a custom long runner manifold (gotta do math) with Velocity
    stacks on the intake side, in a correct displacement plenum...all using stock 1.6/16v
    hardware and injection parts.

- Throttle body will need to be modified with a velocity stack type inlet to increase flow
- Aluminum intake tube all the way to keep it smooth enhancing flow
- Custom air intake to enhance flow but still be off roadable.

- Header will be custom (gotta do math) but bias to extreme low end velocity, some form of
  extended tri y with a long collector.

     I really like your 1778cc combo, I think you brought it up with "Wild", but I want to try and make the on-line build ups something someone with little experience and stuck in the back waters can do.
    While I, like you, think the rod ratio is important it may get compromised to make this a build up that can be copied....but I still need to do some home work. Especially on the intake and cam.....gotta take another look at that 1778cc combo again too!

The goals on the N/A engine I have kinda set in my mind at
- 95hp     |removethispart|@ 4500rpm
- 115ft/lb |removethispart|@ 3000rpm

So about the same horse power but at 1000rpm less and approx 20% more torque at 1000rpm less....in short a real trail grindin / rock crawler.

The Turbo engine I don't have my head wrapped around yet...I just got a Turbo from a 1.5 Isuzu (brand new, never used) and it's the right size for a low down boost beast, but I have to work through details.

For a guy that has lived for big hp and big rpm I'm going through a pretty steep learning curve right now...so I'm open to ideas.


Thanks
Zag

Damn CJ

Now you're making me think........

I've got to dig in my magazine library, Hot Rod did a back to back series of dyno runs on identical small block chevys........if I remember right 1) used 4.7" rods (stock is 5.7) the 2) engine used 6.7" rods.....the long rod produced more hp and torque across the board but I can't remember how much. And lets face it a 2" difference is rod length is extreme...but now I gotta find it and see if it's gonna be worth pursuing for this project.

Thanks

Zag

The theory behind the longer rod is that it increases the piston dwell time thus letting in more mixture. Still need to take into account the Rod Ratio as the G16 is almost at the reasonable limits.

     The increase in dwell time is only part of the theory...The larger part is considered to be the reduction in rod angularity decreasing the power loss in changing the linear motion of the piston/rod into the rotating motion for the crankshaft. I gotta find that article!
     But you are right the time at TDC during combustion does help matters a bunch.

Thanks

Zag

Were the tests done with the same stroke and a taller and shorter blocks or the same height block and  altered strokes or were there changes to the compression heights too?

So many variables, so much to learn.

    I've missed some discussion

Stroke = increase of torque too

As stated, so many variables, a larger piston requires
less pressure (burned fuel/air) to perform the same work
as a smaller cylinder, this is basic hydraulic theory, and
engines share some of the same theories.

Lets face it, small engines have the air flow, pressure cards
stacked against them, get a big bore (4" ) engine and a longer
stroke and less PSI gives more work.

There are ways of making HP and Torque at lower RPM, but
smaller engines just don't do it as easy as bigger ones, I don't
think there is much better torque available in a 1.6 than the
stock cam can provide, but a supercharger boosting low down
could help alot

Low down for a 1.6 is in the 2500-3000 range,  high being 6500
(in 4x4 trim) I don't get much over 6000 RPM under boost on the
hill climbs, and that's fine for me, that's where I want it

1 mm stroke on the crank is 2mm at the piston, how far can we go
and stay at the ideal ratio about 2-3mm

I might have a stroker crank ground out of the toasted 1.6 8V
that is sitting in the old block

Hey CJ
     
      Found the article, it's at home but I believe it was the May 95 issue of Hot Rod Magazine.
The engines were absolutely identical except for rod lenght and pin to crown heights, same everything.
     The difference in power was fairly impressive,bout 15% across the board (all rpm ranges) also dug out Smokey Yunicks book (Power Secrets) and he had similar results on various engines since the 50's. Smokey went into great glorious detail on the theory but in short he felt it was the reduction in rod angularity that made the biggest portion of the difference,  the increase in time at TDC was secondary. It makes sense when you read it through, but basically the straighter the push DOWN on the rod journal the less energy is lost and more power to the crank. Longer rod, less angle-more power, shorter rod, more angle less-power.
     Interestingly both pieces made the same comment that unless you can make a dramatic difference in rod length there are easier places to find power.
     That said it will be interesting to do some reasearch to see how long a rod can be found to work with out hitting the ring lands and if it can be done affordably?

        "Now I remember why I keep all those magazines and manuals"

All dis dare thinkin makes me head hert!....Good topic though CJ we will have to pursue it a little more!

Hi "Wild"

     Wondered when you were gonna get in on this?

     I'm gonna disagree with you on getting more torque down low with the cam. I was amazed at the power I saw in an 8v with a special cam and some other tuning in a tractor a while ago...it pulled like a monster (comparatively) down low (under 3500rpm). The cam had significantly less duration (over 10 degrees) and signifigantly more lift (almost .050"). Based on seat of the pants measuring it had a lot of low down power. I was really surprised and impressed.
     I think that for the 16v it can be very effective, especially with what I've been reading on 16v's and using the lobes progressively to make valve timing changes....gotta try it anyway!
     Back to the rod ratio's, after reading through that stuff last night, I wouldn't get excited about the changes of rod ratio in your engine. Everything was saying it would take significant changes to get any effect and what you're doing is talking percentage points. The power increases in stroke on your project would overwhelm any percentage point losses caused by the rod ratio (IMHO).

Excellent topic and great discussion guys

Hey "Wild"
            What are your thoughts on low rpm turbo charging?

Thanks guys

Zag

We could also lift the comp. ratio while keeping the stock bore by using Honda D15/D16 pistons (same bore and piston pin dia.) as they use G16 pistons to lower their comp. ratio for use with turbos.

I read that they pushed the little end to fit the Zuk pistons. That would mean that you would have to bore the little end to fit the Honda pistons to the Zuk which could compromise strength.

Quote from: cj on August 07, 2005, 07:17:20 PM

We could also lift the comp. ratio while keeping the stock bore by using Honda D15/D16 pistons (same bore and piston pin dia.) as they use G16 pistons to lower their comp. ratio for use with turbos.

I read that they pushed the little end to fit the Zuk pistons. That would mean that you would have to bore the little end to fit the Honda pistons to the Zuk which could compromise strength.

The Honda pistons have a 19mm dia. the same as the G16 so it's no problem. When using the Miata/MX-5 78mm pistons though the little end needs attending to as they are 20mm. Hasn't been a problem so far for the engines I've heard of that have done this.

I just reread that, I meant bushed, lol, you obviously understood anyway. OK I'm at work now and I have that ACL catalogue to refer to. The deck height (comp height) id higher on the MX5 piston and it looks to have a relatively deep dish. Is the top skimmed down to fit in the Zuk engine?

I just reread that, I meant bushed, lol, you obviously understood anyway. OK I'm at work now and I have that ACL catalogue to refer to. The deck height (comp height) id higher on the MX5 piston and it looks to have a relatively deep dish. Is the top skimmed down to fit in the Zuk engine?

Yes. I don't know how much but I was told that there was still at least 0.100" at the thinnest point at the top of the piston and the compression ratio was lifted to 10 or 10.5:1 (can't remember, have to check).