ATTENTION expert engine designers/builders.

I'm looking for some advise building up a 1.8l D16 daily driver (yes that's 1.8l).

The general idea here is to stroke and overbore a D16 using a D17 crank and 78mm pistons.

Based on what I've researched so far I'll need to use custom internals using 1 of the following 2 options:


1) Aftermarket D17 rods, custom 78mm D17 pistons

2) Custom D17 rods, aftermarket 78mm D16 pistons


Here are some quick numbers:

Stroke Rod Comp Height R/S ratio
D16 stock 90 137 29.5 1.52
D17 stock 94.4 137 27 1.45
Option 1 94.4 137 27 1.45
Option 2 94.4 134 29.77 1.42


From these numbers we can see that Honda compensated for the extra stroke in the D17 by reducing the compression height of the piston. This resulted in a significantly lower R/S ratio that many racers and enthusiasts feel was already undesireable. Yet these engines exist and are reliable and sufficient for most consumers.

As I mentioned earlier this will be a daily driver and so it will mostly run below 5k rpm. The compression ratio I'm looking for is about 10:1 and it will eventually see mild boost (6-10lbs).

So my question is, how much of an impact is the R/S drop from 1.45 to 1.42 in choosing option 2 over option 1? I realize that the the R/S number is heading in the wrong direction but given that is just .03 less, is it that significant?


Your comments are appreciated.

 

Any input, please?

 

i don't think that much difference in R/S will matter.
sure it's low compared to a B16, and i wouldn't rev it to 10k rpm. but it's going to have a nice broad torque curve at 1.8 liters and with the low R/S Ratio.
definitely a nice autocross engine, also lighter then B series of course!

the rod length for D17 and D16 is the same. i believe that the rod journal width is slightly smaller on the D17 crank. you could get a D16 eagle rod and have it milled on each side to proper size. then just get custom pistons with the correct Pin diameter and compression height for your desired compression.
only aftermarket D17 rods i think i've seen were close to 3x the price of some D16 eagle H beams.

that's just what i've found out researching the same setup. i might be wrong though regarding the difference in rod width. most people seem to use the stock D17 rods and crank in a stock bore D16 block.

 

Yes the BE width is 22.66 for a D16 and 19.81 for a D17. Would removing 2.85mm of material be excessive?

Nevertheless, I'm leaning hard towards the lighter Crower maxi-light rods designed for the D17. Since I already have D16 78mm pistons, I'm considering getting these rods in a custom length only that will further reduce the R/S to 1.42.

What else could go into the build to compensate for this? Wouldn't side loading increase and would it make sense to coat the pistons and also use tight piston to wall clearances?

 

Thanks Hybrid.

I'm still looking for thoughts.

 

not sure if removing that much material from the rod would cause any bad effects.
if you already have the pistons, then you'll either have to get the crower rods, or see if a machine shop can modify some D16 rods.
might be best and just go with the crowers.

 

One last bump for some input, please.