Blacktop 20v: Displacement Increase.

[Jamehij]

Hi all.

The plan is to build a hard tune n/a 20v. Ridiculous compression ratio etc.

I just want to know what can be done to increase the stroke.

The plan is to bore the block to 82mm with custom forged pistons.

HKS 5age kit? I wont be able to use the pistons any way right? Cause they are made for the 16v head. But if i could get my hands on the crank or similar is that all i need?

Any help would be gratelly apreciated, Flaws, easier routes etc.
Cheers,

86 lover, 4age noob.

[focus_7]

Well theres alot of discussion about 7age's in the 7age thread.

[julzy]

7age or custom made 'stroker' crank
but there not cheap, $2500

[xero]

mate im already using WISECO hi comp 82mm pistons in my small port 16v. my capacity is roughly 1630cc. no hardly a massive increase

to get closer to the 1700cc that the '5AGE' is, you will need minimum 83mm pistons (called 4.5AG sold via RS yasu in japan) which will give you a capacity of about 1670-1680cc. this uses either a mazda bp1800 piston or nissan ca18 piston.

more info here
. hachiroku. com. au/blog/?p=1667#more-1667

[Jamehij]

Cheers thanks for the help.

[Jamehij]

What kinda power outputs have been seen by the members thru a 4age or 7age. My project is going to be long term. I am looking to get a very powerful n/a. So i figured displacement was the biggest power gainer long term.

[xero]

4age be it 16v or 20v your looking max about 180-200hp. thats for a reliable engine being driven on a semi regular basis or flogged at the track.

7age would be about 200-240hp max.. but that would require a hell of a lot of work to do that. mostly with the 7age is you get a massive torque increase than a power increase.

[slydar]

not many members here have done a heavily tuned NA engine. no one has a 5ag unless they were lucky enough to buy an import that already had it, sometimes, not even knowingly

on HR recently there has been a thread about toda (i think, or tomei?) doing a stroker kit for the 4age soonish but..

i personally think though, its kinda pointless. either stick with close to 1600cc. or go 7age.

the deck height of a 4age is quite short, and so stroking the engine isnt really the best idea maybe, considering the rod ratio is already fairly low at around 1.5 : 1 from memory. not enough room in the crank case for a really long throw either. even 5ags need extra machining for rod clearance.

all that = money.

the most you should pay for a 7a is $700. rods can be had for them, if you desire, for about that again or less. so worse case scenario. $1400. if you had planned a serious engine, then possibly you would have done rods in a 4age anyway.

this = close to 1800cc, still a decent rod ratio (just marginally under a 4ag). a big pump up in compression ect.

refer to the 7ag topics for more info

[Vance]

7age blacktop 20v maxes out at 220 but thats with aftermarket cams, pistons, rods, crank, computer + being very well built. torque is what makes the engine worthwhile

a good 7age build for about 180hp-200hp and compression at about 13:1 is toda 272in 288ex 9mm lift cams (lets you retain vvt), aftermarket rods, standard 7a block, crank, standard blacktop pistons, head, trd 0.8 head gasket, aftermarket computer.

will cost a MINIMUM of 6k to build but more like 8k. get a GOOD engine builder

[Sam-Q]

behold



Jamehij: dont bother boring out any 4A engine unless its just one size up to fit new pistons. Otherwise your just wasting your money for no real power gain. There is also some real debate over the reliablity of running 83mm pistons. Something that hasnt been asked yet is what do you really want out of this engine? max top end power?