OK…Ill try to explain this as simple and accurate as I can…
In alot of high end sports car, if u rev em…you see the tach shooting upwards fast…which basically means the engine can reach top RPM in very short amount of time…my question in hand is…
how would you replicate this in an SR or KA setup? Please elaborate on the dynamics if you can not just listing the parts that I’d need etc…
Thanks much
Better valve springs?
well, my bro’s F20b is basically a de-stroked H22a… with Type S head (cams, valves, etc.). it quickly and easily makes power all the way to 9k rpm. :shock:
not sure about SR’s, but i’d assume it’s all in the head. :dunno:
lightened flywheel helps alot in order to do this…more then anything else…pulleys might help a lil bit on n/a motors also.
Removing you clutch fan and stock intake resonator box/pipes helps a bit.
yea…i figured lightened parts would do some of the trick…(lightened cams, pistons, rods, crank, flywheel etc) but my friend mentioned something bout the piston design/setup?? anybody know what im talking about?
He could mean slipper pistons.
Look into titanium rods, valves, valve spring retainers, lightweight flywheel, electric fans, electric waterpump, removing PS and AC, forged pistons, lightened/knife edged crank, dry sump etc.
anything that will allow the crank to spin more freely, I took out the fan and air box on my stock KA and it helped a lot.
My last car had an SR with no powersteering and no A/C… one belt, it revved like a champ.
Has a lot to do with the head, how freely the crank can spin, the bore & stroke of the motor, and the rod/stroke ratio as well. The higher the rod/stroke, the less bending stress applied on the rods, and more going into compressive and tensile. But that’s reliability at high revs, not getting to high revs. Either way, you’re gonna need the reliability once you get there 
Oh, and it’s wise to heat treat things like your rods since that will improve their ductility and increase their yield strength.
regarding the bore/stroke and rod/stroke ratio…which setups are favored? undersquare bore/stroke i presume?
The BIGGEST thing here, is that acceleration is dependant on weight. the LIGHTER the components not only the faster will the engine rev but dont forget a piston and rod has to be STOPPED and then ACCELERATED and then STOPPED and then ACCELERATED again in one rotation. The lighter your engine components and the less the piston has to travel (stroke) in realtion to the surface area that receives the burn (bore) the faster it will rev.
However, lightweight pistons and rods will help you rev out the most, since they literally have to stop and start so often. A flywheel would be second as it is the heaviest constant rotating object, followed by little things like a lightweight valvetrain, free flowing head etc.
There are other things to consider as well, turbo cars generally have more backpressure from the turbo which could restrict revability, as well they often have heavier internal components for more overal strength
Once the engine mechanically wants to rev you need to tune it to be able to rev quick. Sometimes my motor will rev up really really quickly and sometimes it’ll feel like a pile. Why is this? well when you first blip the throttle it is very hard to tune the afr to be pricsise without overshooting or undershooting the target fuel since you are adding so much air all of a sudden. A poorly tuned acceleration fuel could cause even a free reving motor to wind up like a dog.
all that being said i still dont understand how hondas rev up SO SO SO fast. like my buddys oddesy, its a friggin van! WTF!?!?!
i think your SR was one of the sloest revving SR’s ive known, mostly due to the fact that it was pig rich and the timing felt pretty retarded as well.
I honestly had to blip the throttle for about twice the time that normal to rev match the shit
My moms altima is insane,
the thing just FLYS through the revs. blows my mind
once you’ve freed up the respiration system if you will (intake/exhaust) and lightened the components…would this lead to a higher redline given that your aftermarket components could withstand the higher RPM?
Hope my question’s dont seem kinda stupid…Im still a young grasshoppa with these things…
do you know what valve float is? If an engine had no rev limiter what so ever, it would obviously naturally stop revving at some point. This is called “valve float” Its crutial in understanding how to make an engine rev higher, because it is what stops an engine from being able to rev any higher.
Basically what it is is you get to a certain rpm and the vavle springs are not stiff enough to close the vavles fast enough anymore. By the time the valve is fully closed, the cam is already on its way down again. hence the name “valve float” the valves are never full closed they open and then close half way. Valve float isn’t one distinctive rpm, you will over about 100rpm go from having decent power all the way to only enough power to hold you at that maximum rpm.
So the first way to counter valve float is with stiffer strong valve springs. But the higher you rev the more shit doesnt work so well anymore. For example, everything thats heavy is now REALLY weighing you down, and should be replaced if you want to make any decent power. Cams start to become a huge restriction unless they are really big and were designed for a high revving application (thats why VTEC is so sweet), valvetrain components start to take a shit, and anything thats not balanced starts to put a hell of a lot of weird forces on things that wered designed to take it.
Thats why you’ll see balanced engines. this isn’t so that they’ll neccesarilly make more power (they might make 1hp more), but instead so that they will last longer at very high rpm. The wrong vibration will fatigue the metals inside the motor and cause premature failure.
So basically
yes you could raise your rev limit with aftermarket parts. lets make a parts list foran SR.
7500rpm:
Stock redline is 7500rpm. At this rpm we already have guys launching rocker arms all over the god damn place. So first thing first is rocker arm stoppers.
8000rpm:
Not making any power here what so ever. Cams are an absolute requirement if you want to have useable power at this level, however the engine wont blow up any time soon without them. An intake manifold wouldn’t hurt either, as the stock plenum is not tuned for engine speeds this great and you’re losing a lot of power here as well. Bigger cams require valve springs right away as they have more lift and a more aggressive drop off (faster valve close)
8200rpm:
Hydrolic lifters have got to go right about now, and you seriously need cams. Valve springs are a must aswell (however stock valve float is 8992rpm, dont ask how i know :P). Solid lifters, big cams and stiff valve springs. sweet.
8500rpm:
time to start getting serious, at this point i’d really try to lighten up the valve train, titanium retainers, titanium valve springs if you cheaped out last time, big big cams are needed to have any efficency at this rpm as well. Knife edge and balance the crank as well as blueprinting the rest of the shortblock. N1 waterpump is absolutly required at this point as you will be entirely out of hte efficency range of the stock water pump. N1 oil pump is a good idea as well. This should be good for about 9200rpm, if you can make power up there.
Ive never seen many SRs go much above 8500rpm.
All good points.
One other thing to consider if you’re serious about making lots of power up high is gasket/port matching the intake and the head. Greatly improves flow.
I’ve seen 1, great points though…
Yeah Sasha is totally on the money with that.
The only other thing to consider is that turbo motors really tend to not like big cams, so most of the gains seen here would be better seen on an NA engine.
Shorter stroke engines rev better also because of the simple fact it doesn’t take as long for the piston to reach TDC.
Changing your airbox and exhaust won’t alter your safe RPM. The motor might pull better at higher RPM, but this is actually putting more strain on it than if it was stuffed up and couldn’t make power.
Just to touch on valve float, it’s not so much the valvespring (but it is a huge portion of the equation) but it is the design of the lifter itself. It needs to pump up with oil to lift. At very high RPM the lifter will just stop moving, because oil pressure is so high, it cannot bleed it away, so it never drops. Stiffer valvesprings will make this harder by pushing back against the lifter harder, but it could just destroy the lifter or break something else.
This is why hydraulic valvetrains are so shit. The ONLY advantages to hydraulic valvetrains are that they are quieter and cheaper and don’t require maintenance. Well, in the SR they do, and it’s a PITA. The SR doesn’t have adjustable rockers, so they couldn’t even install anti-pump lifters. You have to rely on shims to set the lash. This is why you snap rocker arms, well that and their ultra cheapo divorced shared-duty valvetrain. (16 valve 8 rocker)
If the tolerances are off, instead of having a nice smooth operation, the cam, lifter and rocker get slammed together as they take up the slack.
High revving KA24DE…anyone agree?