7thGear

i'm getting closer in my search but i got to hit the sack,

so i'm asking for any imput possible, articles, personal experiences, etc.

I am planning on getting a b20z into my 98 hatch, and it will remain like that for the moment ( maybe half a year, atleast for the upcoming winter)

in the meantime i am doing mad research in terms of mods that could be done.

i want to go NA with a v-tec head, but as we all know engines like that NEED to rev high to be able to show their true power, and the b20 has a pathetic rod ratio of 1.54 i belive.

There are people here that go the non-vtec route for the b20, i laugh at them, but i assume they do it because of the lack of a good rod ratio, and simply take the route of power down below, not very honda-like at all IMO.

and so, i ask you, the xperts which parts do i need to bump up my rod ratio at atleast a 1.65, if not a 1.80 ++ ( honda s2000 has a r/s of 1.95 !!!! )

alright thx guys. ( no beef with the non-vtec b20 guys)

Spoonin

Rod ratio or rod to stroke ratio is found with the following formula:

<U>rod length in mm</U>
stroke in mm

Stroke is determined by the crank. And the rod length....well, you get the idea. If you want to change the rod ratio you will need to change the crank and/or rods. I am not sure what oem parts you can swap around. I know what you can do with a B16 but, I don't know much about parts that you can interchange with a B20. Eagle makes stroker kits for just about any B-series motor, try them! It may also change your displacement.

displacement is determined by:
bore in mm x bore in mm x stroke in mm x 0.0031416 = displacement in cc

Hope this helps. The rest is up to you and your research skills.

motoman

You could use a longer rod by using a piston where the wrist pin is closer to the top of the piston, but I am not sure if the pistons from the B series engines have much space left to reduce the compression height.

Spoonin

That is a good idea. If you do that make sure you use an oem piston. I believe that most people use the USDM ITR pistons. Don't use these in a B20 without the VTEC head. Piston to valve clearance won't be too good from what I am told.

dfoxengr

rod stroke ratio really isnt that important for a drag motor.

Spoonin

Yeah, that is true. I just always think about how to keep a motor that will be reliable and last a long time.

10K2HVN

:sign: ..another Rod/Stroke Ratio thread....
the only way to get a better r/s ratio is to either put in a smaller stroke crank longer rods () or get longer rods and raise the Piston Pins or get a Deck Plate with longer Rods which is a lot of trouble.
The most you would want to raise the pins is .250" of an inch which is to have the pin in the oil ring! Like Endyn's Kit..

..this is Endyn's Roller-Wave Piston with custom Crower extended-lenth and lightened (for NA) Rods.
http://theoldone.com/components/pistons/
(scroll all the way down..second to the last picture)
.250 inches = 6.35 millimeters
B20 Rods = 137.0076 millimeters
New Rods = 143.3576 mm
Rod lenth / Stroke = Ratio
143.3576 / 89 = 1.610759... ~ 1.61 R/S Ratio
now thats about the best you can get with an 89mm stroke and stock deck which is pretty good since the B18C is 1.58 and the B17A is 1.62.
now if you really want a higher r/s ratio (note: i said "higher"..not better..but im not saying its bad either...) you would either get a Deck Plate are smaller stroke.. since the deck plate is soo much trouble so lets look at the smaller stroke.
the smallest stroke is 77mm (b16) next is 81mm (B17) then 87.2mm (B18C).
Honestly, 77mm is really small so lets not even think about that one.. B17 crank, too hard to find so that leaves us with the B18C crank. Now, if you gonna buy a B20 then Destroke it to 87.2mm why waste that time and money (time is money) and go through all that trouble when you could just buy a B18C that already has that crank!!
so lets do this again...
B18C Rod Lenth = 137.8966 millimeter
New Rod Lenth = 144.2466 mm
144.2466 / 87.2 = 1.65420 ~ 1.65 R/S Ratio
Theres your answer/goal!

HTH you, now if anyone would like to try to help me out....?
https://honda-tech.com/zerothread?id=572809


Modified by 10K2HVN at 12:15 AM 7/25/2003

haggar

Wouldn't the ITR pistons not work in the B20, since its a large bore than a B18 of any variety....

b20_ed

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by haggar &raquo;</TD></TR><TR><TD CLASS="quote">Wouldn't the ITR pistons not work in the B20, since its a large bore than a B18 of any variety....</TD></TR></TABLE>

I was thinking the same exact thing...

_Not_So_Nice_Guy

You can do this for a race motor, but for an every day motor, Larry says those are for race appliation only.

I have his other kit, which uses a .137" longer rod, and wrist pin moved up just before the oil scraper ring in my B20/VTEC. No problems, 10k miles later. They help produce a very flat torque curve.

10K2HVN

0.137 inch = 3.4798 millimeter
yeah, know its only for race applications..just trying to give any idea...
..but do you have any pictures of you Piston/Rod setup???
or if you can tell me how far is the Pin from the Oil Ring..?
because i wanted my Pin 1 millimeter away from the oil rings..which i was guessing around 4mm's raise..but 3.4798mm's sound about right...
confirm?

fox297

If I have the fund, I would get the B17 crank and custom rods. Your R/S ratio should be around 1.75, which is the ideal ratio. With a built valve train and cams, you should be able to rev up to 10k with no problems. If you want some fun, go for 12.5 compression ratio pistons.

nickzed20

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 10K2HVN &raquo;</TD></TR><TR><TD CLASS="quote">:sign: ..another Rod/Stroke Ratio thread....
the only way to get a better r/s ratio is to either put in a smaller stroke crank longer rods () or get longer rods and raise the Piston Pins or get a Deck Plate with longer Rods which is a lot of trouble.
[/i]</TD></TR></TABLE>

When you say that the deckplate is alot of trouble, do you mean that it will cause engine problems? or that it is just alot of work?

Suprdave

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by fox297 &raquo;</TD></TR><TR><TD CLASS="quote">If I have the fund, I would get the B17 crank and custom rods. Your R/S ratio should be around 1.75, which is the ideal ratio. With a built valve train and cams, you should be able to rev up to 10k with no problems. If you want some fun, go for 12.5 compression ratio pistons.</TD></TR></TABLE>

Tell me why it's the ideal ratio...

Suprdave

nickzed20

I believe that if you can squeeze a rod in to make 1.75:1 would allow you to maximize the stroke while also maintaining good rod angles, which will reduce friction and wear. Im not sure if this is it exactly, but these could be some of the reasons why it is ideal. I've heard many places that this is the ideal ratio.

But you do have to admit, that with a ratio of ~1.5:1 your engine will not perform as well as an engine with a ratio of 1.75:1. The rod angles cause way to much friction when the crank is at 90 degrees. The 1.75:1 will allow for smoother movement of the lower end.

10K2HVN

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by nickzed20 &raquo;</TD></TR><TR><TD CLASS="quote">When you say that the deckplate is alot of trouble, do you mean that it will cause engine problems? or that it is just alot of work?</TD></TR></TABLE>
Here is some reasons...
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Suprdave &raquo;</TD></TR><TR><TD CLASS="quote">Tell me why it's the ideal ratio...
Suprdave</TD></TR></TABLE>
Kid's these dayz.. huh super...

Spoonin

The rod/ratio would actually be 1.68:1 using the B17crank and stock LSrods. With B17 rods it would be 1.62:1 . Your rod length would have to be 142.45 and then you would probably need a deck plate.

There are ways to work around an undersquare motor or a poor r/s ratio. Look at the B18c 1.58:1 and the B18a is 1.54:1. The way honda makes the B18c a little more reliable is with the use of tougher rods, block girdle, higher psi oil pump, oil squirters for the pistons and a higher flowing head.

I heard somewhere that some people plug the oil squirters cuz in a high horsepower all motor application it will reduce windage, or something like that.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by fox297 &raquo;</TD></TR><TR><TD CLASS="quote">If I have the fund, I would get the B17 crank and custom rods. Your R/S ratio should be around 1.75, which is the ideal ratio. With a built valve train and cams, you should be able to rev up to 10k with no problems. If you want some fun, go for 12.5 compression ratio pistons.</TD></TR></TABLE>

fox297

I think you have to order custom rods for the B17 crank since LS rod will not fill up the deck. I heard of some people using the rods from the B20A, but I wouldn't trust those thing since you'll be reving pretty high.

As for the R/S ratio, most people have found 1.75 to be a the perfect compromise between high-end power and low-end torque. I've heard of people complaining that the S2000 lack of mid-range power because of the long rods.

eg_type_r93

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Spoonin &raquo;</TD></TR><TR><TD CLASS="quote">That is a good idea. If you do that make sure you use an oem piston. I believe that most people use the USDM ITR pistons. Don't use these in a B20 without the VTEC head. Piston to valve clearance won't be too good from what I am told.</TD></TR></TABLE> come on man itr pistons in a b20 come on now

eg_type_r93

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Spoonin &raquo;</TD></TR><TR><TD CLASS="quote">That is a good idea. If you do that make sure you use an oem piston. I believe that most people use the USDM ITR pistons. Don't use these in a B20 without the VTEC head. Piston to valve clearance won't be too good from what I am told.</TD></TR></TABLE> come on now itr pistons in a b20 come on now

JCushing

i cant belive i read this post.

i think you should just swap in a f20c

AzG35

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by nickzed20 &raquo;</TD></TR><TR><TD CLASS="quote">But you do have to admit, that with a ratio of ~1.5:1 your engine will not perform as well as an engine with a ratio of 1.75:1. The rod angles cause way to much friction when the crank is at 90 degrees. The 1.75:1 will allow for smoother movement of the lower end.</TD></TR></TABLE>

I don't think this is true. Changing your rod/stroke ratio will change your powerband, but you will usually make the same or close horsepower, but peaking at different points. Longer stroke motors will tend to make better torque while giving up "some" high RPM power. This is great for a daily driver because you will get more low end torque and won't have to rev as high to make good power.

10K2HVN

im never gonna be in another R/S Ratio thread ever again....

JCushing

hehe.... my favorite part was <TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 10K2HVN &raquo;</TD></TR><TR><TD CLASS="quote">the b20 has a pathetic rod ratio of 1.54 i belive. There are people here that go the non-vtec route for the b20, i laugh at them
</TD></TR></TABLE>

10K2HVN

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by JCushing &raquo;</TD></TR><TR><TD CLASS="quote">hehe.... my favorite part was</TD></TR></TABLE>
awww..but i didnt say that.....? 7thGear did.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 7thGear &raquo;</TD></TR><TR><TD CLASS="quote">...the b20 has a pathetic rod ratio of 1.54 i belive.

There are people here that go the non-vtec route for the b20, i laugh at them...</TD></TR></TABLE>