okay I have a F20B with a close ratio gear box. I have two options here

1. take advantage of the higher r/s ratio that the f20b offers and rev it very high (9000+) with a built head)
2. stuff f23 crank, rods + custom pistons in there


I realize that there are advantages and disadvantages with both. But which is "best"

 

il say.. build it to rev, lol

the close ratio gear box will agree,

 

Have you already picked out a cam? Or will you pick once you decide what your engine characteristics will be?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by gibsanez &raquo;</TD></TR><TR><TD CLASS="quote">Have you already picked out a cam? Or will you pick once you decide what your engine characteristics will be?</TD></TR></TABLE>

haven't picked out a cam yet.

will pick one out once i decide what engine characteristics will be.


If I rev to 9000 when i shift my gears will fall to 7200.

 

holy fawk, nice and high eh.

My question is, if you were to go with the 9k rpm idea, can you find a cam that will make power in that area and still have a half-decent torque curve?

 

well what will the car be used for?

 

My stand on bore/stroke is unless your displacement limited by rules always go big.The increase in stroke may move peak power a few hundred rpm lower,but will make more torque/hp everywhere.Thats assuming you have enough head flow to support more power.

 

i agree with njin buildr if it is a street car go big if it is a race motor build the head and go from there... besides with the short gearing and a **** load of torque that little eg would fly.

 

why not use the h22a crank/rods and rev it high?

 

high high ...lol

with the tranny you have i tihk it would be a good setup . plus i just want videos of a f20 pumping 9g

 

what tranny you using?

 

stroke it
Go Big Or Go Home

 

stroke it. There is no reason not to. You will end up with a much more useable power band. If you build a motor to rev to 9k, alot of the time they end up kinda torqueless in the lower rpm's which means you HAVE to rev the **** out of it to get what you want.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by gibsanez &raquo;</TD></TR><TR><TD CLASS="quote">holy fawk, nice and high eh.

My question is, if you were to go with the 9k rpm idea, can you find a cam that will make power in that area and still have a half-decent torque curve?</TD></TR></TABLE>

The F20B uses H22 cams, so I am assuming that if I find an aggressive cam for the larger h22 that it will supply even more air for the smaller f20b cylinders. Maybe I'm wrong, but it seems to make sense, correct me if I'm wrong.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Professor15 &raquo;</TD></TR><TR><TD CLASS="quote">well what will the car be used for? </TD></TR></TABLE>

Honestly just whatever I want. I don't really have a good reason to build it. I just enjoy "building" so maybe just romping around on the interstate maybe doing some time trials on a road course, I dunno.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by NJIN BUILDR &raquo;</TD></TR><TR><TD CLASS="quote">My stand on bore/stroke is unless your displacement limited by rules always go big.The increase in stroke may move peak power a few hundred rpm lower,but will make more torque/hp everywhere.Thats assuming you have enough head flow to support more power.</TD></TR></TABLE>

I guess i'm kinda old school with my thinking mentality here, but I just think that a lower r/s would have an adverse effect under constant high rpms. with my 5th gear being at 4950 @ 80mph I'm kinda more interested in leaning more towards the 1.65, but I'd be willing to change that.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by slofu &raquo;</TD></TR><TR><TD CLASS="quote">why not use the h22a crank/rods and rev it high? </TD></TR></TABLE>

I've considered that but I just don't know if it's worth it for only a 2.7mm of stroke increase. My money would prob be better spend elsewhere.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by fatboy1185 &raquo;</TD></TR><TR><TD CLASS="quote">what tranny you using?</TD></TR></TABLE>

I am using a custom geared d-series LSD transmission that I built




Using a bisimoto H/F2D adapter plate






I'm open to all ideas

 

As gearboxes are TQ rated not BHP rated and you are using a D-series box, I would go for the short stroke, more rev's.

 

Don (or anyone) do you know any rough limits of the amount of TQ a d-series trans can handle?

High revs would be great for a race car but to drive around on the street to mess around in having to rev all the way to 6k to start making power sucks. Thats the way my old h22 setup was and I hated it.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by DonF &raquo;</TD></TR><TR><TD CLASS="quote">As gearboxes are TQ rated not BHP rated and you are using a D-series box, I would go for the short stroke, more rev's.</TD></TR></TABLE>

The only question that arises with that said is how are the turbo D guys not experiencing any problems with a lot more tq running through their gearboxes?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by mgags7 &raquo;</TD></TR><TR><TD CLASS="quote">High revs would be great for a race car but to drive around on the street to mess around in having to rev all the way to 6k to start making power sucks. Thats the way my old h22 setup was and I hated it.</TD></TR></TABLE>

keep in mind that my gears are very close and even in a cx hatch a stock f20b has more than enough power down low and up high.

 

Torque makes fast, RPM makes noise.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Hardt &raquo;</TD></TR><TR><TD CLASS="quote">Torque makes fast, RPM makes noise.</TD></TR></TABLE>

did you read the part where i said "I have a close ratio gearbox"

This post means nothing.

 

+2.7mm stroke of the the h22a crank &gt; f20b crank seems worth it. 89mm ls/crv crank &gt; 87.2mm gsr/itr crank makes a noticeable difference. you'll be able to carry the power for longer more reliably than with the h23 crank, and you'll have a good chunk more tq than the stock f20 crank affords. = you can sell the f20 crank/rods to cover the cost.

 

I can agree with that, though I do think that a well-put-together 95mm bottom end can definitely last long, **** do you remember the big RLZ h series build, it's my roommate's car, The Birdman. Anyways he's got a 95mm crank in it and she is revving to near 9k and is in perfect condition over a year later. It does have carrillo rods in h22 length and custom, light ***, short skirt pistons in there from wiseco so the rotating assembly is pretty damn light, even so though, I would still say that the 95mm bottom end can last under rpm.

There are plenty of guys running around with 4+ year old h23 vtecs revving to near 8k.

That is all circumstantial evidence and such, just examples, so I'm not trying to prove any points.

I think it would be up to a peace of mind vs a few lbs of torque debate. LOL thats a classic one.

If it were me, I'd stick with the h22 crank if this car will see more than 10k miles a year. Otherwise 95mm would be in the sights for me.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Bense &raquo;</TD></TR><TR><TD CLASS="quote">

did you read the part where i said "I have a close ratio gearbox"

This post means nothing.</TD></TR></TABLE>

You are right, the worlds fastest NA cars with their 2600+cc engines and short gear boxes making power over 10K.... Yeah, what the hell are those guys thinking???

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Hardt &raquo;</TD></TR><TR><TD CLASS="quote">

You are right, the worlds fastest NA cars with their 2600+cc engines and short gear boxes making power over 10K.... Yeah, what the hell are those guys thinking???

</TD></TR></TABLE>

horsepower is a function of torque and RPM. Lets keep the elementary lessons out of this thread please. Thanks.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Bense &raquo;</TD></TR><TR><TD CLASS="quote">

horsepower is a function of torque and RPM. Lets keep the elementary lessons out of this thread please. Thanks.</TD></TR></TABLE>

zam!