Effect of reducing compression ratio from 9.8 to 9.4???

**TERRA Operative** · 19-08-2010, 08:50 AM

I've got a 5E-FHE here I'm rebuilding and due to time constraints it's looking like I can't wait for new 5E-FHE 9.8 compression ratio pistons to come from Toyota (no one else makes 5E-FHE pistons...) so I'm looking at the alternative of the much more common 5E-FE pistons which have a compression ratio of 9.4.

What will the effects be of dropping the compression ratio this much, all other things being equal? Can I work out how much power I will loose somehow?

Or can some one get me a set of 5E-FHE pistons in a few days???

**Hiro** · 19-08-2010, 10:18 AM

If you just look at the difference in power between a 9.4:1 5EFE and a 9.8:1 5EFHE there's about a 10-15HP difference, assuming the rest of the engine is identical (you'd assume the ECU would be tuned to match the 9.8:1 ratio though so that might change things a bit differently though).

**TERRA Operative** · 19-08-2010, 10:27 AM

Yea, I assumed that would be the case. Hmmm, I need a set of 5E-FHE pistons yesterday.....

**trdee** · 19-08-2010, 10:29 AM

it wouldnt be a massive difference, could make up for it with a thinner headgasket?

**TERRA Operative** · 19-08-2010, 10:38 AM

Looks like the ones I had on order are now in transit at the 11th hour, freak out over.
We have already got a metal gasket to stick on, I should work out what the final compression ratio will be.

All good now.