N/A 6G72

[6G72gearhead]

Something I've been thinking about. It is well known that our engines are not considered a very good platform for N/A. Why exactly is this. I've seen Honda's producing 250 N/A HP, and this is considered the limit for the 6g72 N/A. Why? It occured to me, our problems is rpm, the engine needs to spin higher, which begs the question, what is truely the rpm limit for the 6g72 in stock form. 6700 maybe, just a guess. With proper balanceing and clearences and valvetrain is 7500-8k possible? Or will the heads restrict flow before this point cancelling out any gains through rpms. It is well known that high output honda's can spin in exess of 11k when heavily modified. What is the limit on our engines.

[hsinya]

there is suppose to be a stratus (6g72) with rpw's 6pack running 500hp? can anyone else chime in on it?

if the money is there it can be done. u see it on hondas all the time because everyone and their grandma drives a honda.

[6G72gearhead]

I know its cheap to build a Honda but that example was primarily designed to show how a platform is able to make hp through rpms instead of boost and displacement. How high can you spin a streetable 6g72

[DOHCstunr]

i'm sure you copudl take it to 7k no problems.
but honestly there is no point to taking it there unless you have some cams.
valvesprings and retainers are a definatly plus up there. but the power woudl be made form the cams modifying the volumetric effeiciency.
im sure you coudl rev to 7 all day long.
but in the end its up to the rod angles and subsequently the piston velocities.

if you want to make REAL power,
get ahold of some way to control/ tun eyour timing.
timing is EVERYTHING,
especially on an n/a motor when you are trying to squeeze ponies.

i imagine your stock plenum coudl be restrictive at those rpm.s
you coudl swap over to a diamante plenum.
or a gts eclipse plenum.
although the upperintake manni has the largest plenum,
it also has long runners. (and you get a larger throttle body if you score a plenum w/ it still attatched.
porting/polishing the lower intake manni wouldnt' hurt anything i'm sure.
wouldn't be hard to do either.

but again.

power is all in the timing,
and

[6G72gearhead]

My question does not lie in the valvetrain as I know how to adress that. My question is will the sortblock handle it. Will the mains suffice, will the con rods be up to the task. Valvetrain wise, stiffer springs, very high lift cam, and some tougher valves, I dont think it would spin high enough to warrent titanium valves, as there are cars without 'em spinning as high or higher. As for the upper intake, the rpw unit looks pretty good with its internal velocity stacks and availability with a holley twin 58mm throttle body. I know its tuning tuning tuning, but what is possible with our 6g72 shortblock.

[heeroborn1016]

sorry for asking this but i have a 4g64 and wondering if the throttle body sold for the 6g72 will fit from what i understand its wether the #of screws match up?

[DOHCstunr]

My question does not lie in the valvetrain as I know how to adress that. My question is will the sortblock handle it. Will the mains suffice, will the con rods be up to the task. Valvetrain wise, stiffer springs, very high lift cam, and some tougher valves, I dont think it would spin high enough to warrent titanium valves, as there are cars without 'em spinning as high or higher. As for the upper intake, the rpw unit looks pretty good with its internal velocity stacks and availability with a holley twin 58mm throttle body. I know its tuning tuning tuning, but what is possible with our 6g72 shortblock.


lets put it this way.
yoru block has a well oiled forged and nitrided crank. your rods are forged rods(same rods as come in the 3kgt)
your block is cast iron so it can take any kind of abuse you want.
i doubt that yoru hardware will be a weak point at those rpms so i woudln't even bother upgrading the rod bolts.

so yeah, you can rev as that high.

but the key is rod angles.
revving that high causes piston velocity to increase dramatically.
there is a point where your pistons are moving so fast that the cylinder literally will not fill up with the full 1.5 liters of air per rev. and thus.. even thoguh you can rev that high there might be no power to be made up there... understand
the stroke is another important factor...
since the piston has to travel so far up and so far down, lubrication becomes an issue when runnign higher rpms, and of course piston velocity and rod angle factor back in. as the oil beings to sheer up there, you will wear your cylinders oblong. the steeper the rod angle the greater the wear.

destroked motors can rev to the moon cause the piston moves a very short distance and the rods are long enough that there is very little rod angle.

but back o limiting factors,
if you codl rev to 8k on a stock motor coudl you shift there too?
automatics are a no brainer... not only woudl it take forever to get up that high, the stock torque converter and clutch packs would not be able to survive.
and in the case of a manual... synchro's will lock you out when revving that high.


its a complicated mess.

so 8500rpms idk man just too much stroke.

but 6500-7 its doable, but you will have restrictions... be it the asthmatic sohc head, or the block geomerty itself.

i'm not saying that there isn't any power lurking up there. i'm saying its possible that it woudln't be worth it. especiilay N/A


are you still automatic?

[SinSere]

You really are a wealth of knowledge man, just though I'd throw that in there.

[6G72gearhead]

Yeah I'm auto until this one blows, which the way I drive wont be long. What do you mean about the syncro's locking up, I race with a guy in a '94 integra that revs to 10,500 and he shifts it there with the stock 5spd. Not that I'd do this but I've seen it done, that doesnt mean that things dont change when I get back to our application but its there. I see what your saying about the intake path, and with cams and a tune I think you could truely utilise a 7k redline. I'm not saying that I'd do this per say, I just love theorizing and having technical discussion. I'm currently going to school to learn as much as I can about tuning engines, engine theory and physics, so if I were to get the home machining capabilities I might consider having some fun with this, but that will be far off. I know you can bore and sleeve these engines, and I'm guessing you could destroke it as well given you have the crank, or can machine it yourself. But this doesnt adress the airflow problems you have posed. Is it the extreme angle the intake feeds at or could this be adressed with machine work? I know RPW has the ITB set up, does anyone have or know of any dyno graphs for engines running this set up? If the block is up to it then that clears that hurdle but there are definatly many more to be adressed.