Just picked up!! SmallPort 4A-GE!, One Question???? Options

[94STcoupeKyle]

How much difference is between the smallport and the bigport?
like the HP and internals?

[Kwanza26]

How much difference is between the smallport and the bigport?
like the HP and internals?

There were two versions of the bigport... the 7rib block version and 3rib block version. The later (87.5-89) had the 7 rib blocks with 42mm rod journals as opposed to the older bigports with 3 rib blocks and 40mm rod journals. The newer big internal versions also used different piston pins, which were full float with clips as opposed to the older ones which used 18mm press fit piston pins. The older "smaller" internal versions aren't as strong as the much more stout "big" internal versions. I wish I can find pictures of the rods side by side to show the significant differences in size and strength... however, the side effect of the "big" internal version of the bigport engine was that it made less power because of the added weight of its moving parts. The good thing about it, was it was a hell of a lot stronger than the small internal version. The reason this engine was called "BIGPORT" is because of the intake design and the head's ports. Bigports used TVIS, which were a series of butterflys built into the intake manifold designed to increase intake velocity and in turn, increase low-end torque. Smallports, which came much later (1990+) eliminated this system. Bigports made anywhere from 112-127 hp depending on which ecu and metering system is used. Mechanically speaking... there is no difference between the motors besides the big and small internals. The heads, compression, etc, were all identical.

Smallports are just that... they have smaller intake ports and were designed to eliminate TVIS. Because TVIS was eliminated, they do have slightly less grunt in the low-end, but make up for it with a superior port design and higher compression. Smallports had the 7rib "big" internal block with high compression pistons (10:3:1). That's pretty much it as far as differences go. The rest is pretty much the same as the bigport. Smallports made about the same amount of torque as the bigport, however on a very different curve. They however, made more horsepower... between 130-140 depending on the ECU and metering system (MAP or AFM).

Visit Bill Sherwood's page for more detailed information...

http://www.billzilla.org/4agstock.htm

This post has been edited by Kwanza26: Jan 31, 2006 - 10:02 PM

[94STcoupeKyle]

Dang! thanks for the info it really helped.


Kwanza what year car do you think this motor came out of?

[Kwanza26]

Dang! thanks for the info it really helped.


Kwanza what year car do you think this motor came out of?

Don't know which Japanese spec cars had these motors... but here in the US... 1990-1991 AE92 Corolla GTS's had them, and Geo Prizm GSI (1990-1992) had them. Probably something in the realy 90's... cause Silvertop 20V's replaced most 16V's by 1992-1993...

[94STcoupeKyle]

Yea thats what i though but i wasnt sure, yea im not really sure what japanese cars these came in. it doesnt even matter that is came from japan does it, like power wise or anything?

[Kwanza26]

Yea thats what i though but i wasnt sure, yea im not really sure what japanese cars these came in. it doesnt even matter that is came from japan does it, like power wise or anything?

The engines are all mechanically the same. What's different was the ECU and wiring. Japan go MAP sensored just about everything while we in the States and elsewhere got AFM's. We also had other things like EGR, extra emission related sensors and whatnot.

[94STcoupeKyle]

How much would a stand alone ecu would cost me?

[yungazzdriver]

well megasquirt is the best bang for your buck but check it out at club4ag buying/selling section

[94STcoupeKyle]

right now im trying to get everything together so i can try to swap it as soon as possible