Hey all

 

ive got 3Q's, hopefully some 1 can anwser them !

 

With the K Series engines - 3k, 4K, 5K etc - What was the largest capasity K engine that came out? - 7K? 8K?

 

&

 

Out of all of those K motors - which 1's came out as a carbie motor not efi?

 

1 More !

 

WHich is better in an engine when u rebuild it - (similar like simons - 5K block, 3K race head) - Hi compression or Low compression?

 

Thanks for all ure help people :)

 

Teddy

ok, ill put a bid for both

 

What compression is better for a race engine

 

and what compression is better for a standard engine

 

thanks :)

 

 

Its got on here

 

"The new Toyota 7K-C engine has 90 percent of its peak torque in the normal operating range, from 1500 to 4400rpm"

 

I would a higher compression motor make the 4400 rpm move to a higher number?

 

:D

well, I'm just thinking about all different motors, how they work, differnt possibilities.

 

the only reason i am intrested in the 7K is because its a 1.8L - where as the 4K is only a 1.3L

 

I am thinking if u could apply similar princibles to what simon has done to his motor, but with a larger capacity - 1.8 L

 

The reason i ask about compression is because if u look @ a standard 5K motor with the standard head = u get 'x' compression.

 

If u get a 5k Motor, and put a 3K race head on it (eg simons) u get the different compression (well, to what ive herd / red anway, i stand corrected if i have miss red / listened)

 

see what i mean?

 

- it all a learning curve for me :) -

ah ok, i get u ! - thanks for that nick :)

have a look in my faq for K motor engine capacities

 

http://e30m3performance.com/myths/more_myt.../comp_ratio.htm

have a read of that to learn a little about compression ratios, after reading this:

 

an engine works by igniting atomised fuel in air to make an explosive force to move a piston to rotate a crankshaft. this force then goes thru the flywheel, clutch, drivetrain, tyres, and pushes your car. essentially, the more you can compress that atomised fuel and air, the more power it will make when it explodes. more compression equals more power

 

however there is a limit, based around the camshaft (see "dynamic compression ratio" in the link above) and the actual design of the head. too much compression, and a motor will "detonate" or "pre-ignite" because of the head, which means the air-fuel mixture is exploding before the spark lights it. you can also get the fuel exploding from one side, the spark exploding from one side, and a harsh shock wave happening in the middle, good for destroying pistons

 

as a general rule, in a factory-type motor, you can run a compression ratio about 1/10th the RON number of your fuel. run 98 RON BP Ultimate and you could safely run 10:1 (with proper ignition timing). run 91 RON regular unleaded, and you'd be safer with a motor running 9:1. a more severe camshaft will change this, as the piston moving up on the compression stroke forces some of that air and fuel out of the exhaust valve before it gets compressed (if you understand this sentence, you understand dynamic compression ratio)

 

case in point, to get the most out of my cam, i should be running MAX 10.6:1 compression. nick's ke70 cam is alot more severe, he would need to run 13.5:1 to get the most out of it. that's the difference in the air being force out of the exhaust valve because of the different cam timings. i don't think you'll ever design a combustion chamber good enough to handle 13.5:1 in a K motor. larry endyn (www.theoldone.com) is an old racer in america, he used to build motors that could run 17:1 compression and more!

 

when you force induct a motor, this all changes, because you're forcing more air into it on boost, to raise the dynamic compression again. it depends on how much boost you run. you could probably force 6psi into most regular (9:1ish) factory motors and get away without changing the compression, this will make the car quite quick to drive, because the dynamic compression is still high at low rpm, off boost it would be just like driving a normal car. if you want to wind say a huge 30psi into something, you need a LOW static compression (8:1 or lower) because your dynamic compression gets so high once the turbo/blower starts making boost. this will give you less performance off boost, like driving a lawnmower. it's all a tradeoff

 

is that kind of what you were looking for?

wow - i have learnt more in the last 15 mins than i have all day @ school - thanks !!!!

 

yeah, that anwsers my question lol - Cheers!!!!!!