3s head on 5s Options

[Boss-Celica]

I got some extra cash laying around just waiting to be spent on my car. So I was thinking on puttting a 3S head on my 5S. Has anyone done this before?

[Kwanza26]

Understand that a 5SGTE swap would be no different than a 3SGTE swap. You will have to use the 3SGTE wiring, ecu, and electronics. Also, I will add... the MR2 guys who made 600 some odd horsepower do not do it solely because they have a 5SGTE. Understand that the head only changes the horsepower characteristic... but the power maker is the turbo. If you build up the 5S bottom-end... even the FE head can make that power with boost. Take for example Paradise Racing's drag AE86. 8 second 1/4 mile car with a stock FE head and built bottom-end. A typical 5SGTE build will probably yeild less power but more torque than a regular 3SGTE mostly because of the displacement... the only major difference the head will provide would be the power delivery. The 3SGTE will always have a better top-end because of the 5S block's geometry.

Also know... that sort of power doesn't make a car very streetable or reliable.

[jgreening]

A typical 5SGTE build will probably yeild less power....  The 3SGTE will always have a better top-end because of the 5S block's geometry.
[right][snapback]325519[/snapback][/right]

Can you explain these two sentences in greater detail please? What are the geometric differences you speak of and why do those differences result in less horsepower for a higher displacement engine?

[Kwanza26]

A typical 5SGTE build will probably yeild less power....  The 3SGTE will always have a better top-end because of the 5S block's geometry.
[right][snapback]325519[/snapback][/right]

Can you explain these two sentences in greater detail please? What are the geometric differences you speak of and why do those differences result in less horsepower for a higher displacement engine?
[right][snapback]325620[/snapback][/right]

Rod-stroke ratio. per psi of boost... a 5SGTE will make much more torque than a 3SGTE (because of the displacement), but because of it's poor piston dwell (relatively short rods in comparison to its stroke)... it won't make as much top-end power. It's the same reason why you don't see many n/a 5SGE's. The GE head can help change where horsepower peaks in the rpm band... but the engine's design is against top-end power.

If you compare the 5S rods and the 3S rods... they are almost identical in length. Considering the 5S has .2 liters more displacement... this means the 5S bottom-end is not designed with horsepower in mind. Even with a GE head... this characteristic isn't gonna change too much.

Comparatively speaking... take the 7AFE and the 2ZZGE. Both have nearly identical specs in terms of bore/stroke (82mm bore 85mm stroke for the 2ZZ and 81mm bore 85.5mm stroke for the 7A)... but the 2ZZ is a horsepower engine and is designed with rods, again, nearly identical in length to the 7A even though it lacks the stroke the 7A has. Compared to its (2ZZ) stroke, it has enough rod length to maintain good piston dwell and a stroke ratio to maintain top-end torque/power. As for the 7A... it's a very good design and has good performance potential... hence is why you see more n/a 7AGE's than n/a 5SGE's. Even turbocharged... these characteristics stay with the engine. In the 5S's case... n/a 5SGE isn't gonna be worth while. a turbo 5SGE (5SGTE) is the equalizer, since the turbo takes greater advantage of the displacement.

Am I starting to make sense yet? I'm not saying a 5SGTE is a bad build... it's an excellent build for say... a drag engine... but strictly speaking horsepower... a 3SGTE can match it. Hell... when people start talking about how such and such made 600 horses with a 5SGTE... I'll answer... you can make that much with a 5SFTE if you match the 5SGTE mod for mod. It's all about $$$ when it comes to boost...