i am about to start building my car for autocrossing..i just want something fast and powerful..

i was wondering what would make more power after being fully built a gsr or ls/vtec ?

i was thinking about gsr with ls crank but i dont know the pros and cons..

im trying to push 220+ whp all motor.

what im trying to say is which motor would hold more power .
if i do go gsr should i use stock crank or ls crank ?

 

if it were me, i would use a gsr, the blocks are stronger than the LS block. eagle has a forged kit thatmakes it a 2097cc engine, with autox you need a wide torque range and the 2 best ways to do that are more displacement and supercharging. and as far as displacement goes......stroke is the best thing for torque. so i wouldnt put a WHP goal on it because thats gonna be at high rpm........my goal would be a broad(wide rpm range) flat torque curve as high as i could get it. if that means sacrificing some top end power then so be it. you have to be able to explode out of the tight corners and that means low end torque usually, but then you need to carry that into somewhat high rpms for the straights.

 

im going to build a gsr block but is it worth putting in the ls crank ?

 

for the small displacement increase i wouldnt use the ls crank. if you want a significant increase in displacement and therefore a significant increase potential power and torque.....id go with a stroker kit.

 

I WOULD use the LS crank for the additional torque in the midrange of the powerband needed for autocross. POWER is not your main concern, its actually torque (though HONDAS rarely make it, regardless, so I know we're being technical) but I have found Vast improvements of torque with the LS crank in the GS-R block. over 20ft/lbs.

 

i have a somewhat basic/budget (if i hadnt started with an absolutely bare block) LS/v that last year made 203/140 on a dynapack. new exhaust and header should easily yield greater than 210whp. factory 81mm block/rods/p30 pistons witha ported head and pro 1 cams.

with my gearing upgrades i think it would rip on a race track if i could get it to handle.

 

Autocross will require the extra torque a LS vtec provides. I have a LSV and LOVE it. I pull about a car with every shift. Top end is about the same

Nick

 

if you are really worried about torque in a easyish swap........might as well go with a b20/vtec..........

 

GSR Head-
CCCylinder head max flow Package
BluePrint Racing Valvetrain kit -high comp.valves
Crower Stage 2 cams
toda cam gears
blox intake manifold-ported
max bored tb
thermal im&tb Gasket
b&m fpr and fpg
high comp. gsr head gasket
370cc injector

GSR BLock-
Engine specs:
ge block guard
82mm pr3 piston
ls crank
new arp rods bolts and shotpeended ls rods
ARP bolts,main,head,rods
Hot tanked,Hone
Crank balanced and micro polished
Rotating assembly balanced
balanced rotating assembly including flywheel and clutch
oem bearing
oem gasket kit
oem water pump,timing belt,tension


this is the way i wanted to build a gsr with ls crank..i know if i do all this and a good good tune i can push out alot..tunning is gonna be done by a p28 with hondata s200

 

if you are going to all that trouble of building.....you are going to use the LS 89mm crank.......so instead of that why not go with a B20/vtec? its already 84mm bore(more than the 82mm you have planned) and 89mm stroke same as the LS. so you balance all of that, and you have a better platform to start with. get some better rods and higher CR pistons.........then all you have to worry about is converting it to vtec..........B20 blocks are cheap too.

so what you are looking at is a GSR block with LS crank and 82mm pistons that gives you about 1880cc, or you could go with the stock B20(or even bore that if you like) which gives you a minimum of 1973cc......... which would be a 5% increase in displacement over your planned build......and also means a 5% increase in potential power..........so with the LS stroke GSR......lets say you are looking at 200whp, then with the stock B20 at the same CR you should be looking at more like 210whp........and a similar bump in torque too. also the B20 having bigger bore moves the cylinder walls away from the valves which allows the head to flow better.

your decision, but the math doesnt lie.

and just to make sure it stuck.....with autox you really need to be concerned with torque more than hp..........high HP numbers come with RPM.............which you wont always be able to use high rpms in autox..........keep your sights set on as broad and high a torque curve as you can get.

 

This is true with the math. What you're NOT looking at is the effort involved in using a proper B20/VTEC kit-assembly just to get the extra 2mm in bore. For the purpose of the car, stroke with torque is a little more important than the bore that would make a better NET increase for the amount of work he's willing to put forward. Yes, a B20/VTEC is IDEAL, but based upon availability and difficulty of proper assembly (depending upon his mechanical inclination), the LS Crank/GS-R block is not a bad way to go.

I personally felt there were little advantages for doing the B20/VTEC swap with my use on the circuit. Too many things to go wrong if that cylinder head wasn't properly oiled. I had similar torque with a good friend's B20/VTEC at only 1857cc to his 1998cc. Of COURSE 2.0 litre would make more, but for the EFFORT, I'm glad I stayed where I was.

 

nice to see another view on this. i do understand the extra effort is a pain....especially if you dont have the experience or knowledge to do it yourself.

but like i said, its an option he might not have thought about. just throwing ideas out there.

also, i wouldnt rev a moderate build LS over about 8500..........piston speed will start getting into the dangerous range and with stock length rods(137mm) the rod/stroke ratio is pretty low so the gforces put on the rod, wrist pin, and piston are higher. you have to use race bearings. and even balancing needs to be done differently for very high rpms.

 

i have read and heard everything about ls/vtec and b20/vtec but i want to something different but if it wouldnt make a different i rather build a gsr ..but overall i just want the power of a gsr with tq of a ls...but by putting a ls crank and stuff into a gsr wouldnt do much then i wont do it..that is what im trying to figure out now...

 

keep it all gsr man. micro that crank if you want. or maybe you can just put a stroker in a b16 that seems to be the money ticket in j-pan

 

If you build the GSR right you can get torque out of it. I'm at 190/136 in my GSR with ITR cams. If you use a cam built around torque you should be in good shape. Buddy Club Spec 3+, nice torque curve bit low on peak, Skunk2 Pro1's are also another cam that gives a strong torque curve.

Two things on you list you must change,
Blox IM, get a Skunk2 or a Performer X (I am running this).
Get FIC 525cc injectors, nearly the same cost as RC's but a much better spray pattern, more power.

 

Doing the LS Crank in the GS-R is a torque maker, simply put. It's an option I decided to follow and wouldn't change a thing. What does "enough" for you or not really is determined by the rest of the build. Not just the crank/rods alone.

This is true to a point, I've noticed. But I look at it as this; if you plan to build the block whether it is all GS-R or GS-R/LS Crank, it would be best to balance the assembly anyway, then they can safely reach over 8500rpms, or survive a misshift as a worst case scenario.
I myself accidentally revved the engine to over 9586rpms on my LS/Crank GS-R build, (it will be forever etched into my brain) and not one issue has resulted in over a year after that incident. But that was because everything was properly balanced from the beginning.

As for the R/S ratio argument, that's been beaten to death, and still IMHO is based upon the balancing of the engine.

 

agreed, i was referring more to sustained engine speeds above 8500, a mis-shift, or a very occassional run to 9k will probably be fine as long as its got a good balance. and any numbers and examples i gave are assuming that the engine has been balanced.

and as far as the R/S ratio, the balance doesnt have anything to do with how fast the piston is acceleration..........and except during compression, the rod and wrist pin have to keep the piston from being flung up through the head. this is where R/S comes in, and by keeping the ratio higher, there is less force trying to sling the piston or rod off the crank. so even the best balanced engine with a horrible R/S ratio will still require serious beefing of the rod, pin, and pin bore anchors to survive at high rpm. but that beefing is going to come at a price too, and that price is weight(if you go with stronger forged components), or money (if you go with stronger titanium components).

also ive seen dyno charts of indentical engines with different rod lengths, higher R/S makes more power. they were all pushrod V8s too.

BUT i will add that i read an article recently by a very reputable cam designer and engine builder. his article states that 4-valve engines tend to flow better with a lower R/S ratio(closer to 1.55:1) BECAUSE the piston is accelerating so fast that it helps creat more vacuum and pull in air faster which is what multivalve heads need since you run into the volume vs velocity roadblock at low RPMS.........which is exactly why honda invented vtec. and that info is completely opposite on 2 valve engines such as the old american V8s, more R/S gives better head flow.

so to settle this discussion, we would need a bone stock engine on a engine dyno, flow-bench the head and get good baseline info. then just start playing with it and record what we find.......oh yeah a very sizeable budget would help too since we would need a bunch of custom parts..............might be a good pitch for a tuner mag.........although it seems like most of them ONLY are seeking a monster peak HP number and could care less what else is sacrificed.

but i think ill send some emails and see if anything comes of it.