Compression

[Zafar16]

What is the highest compression ratio you can run on a 1st gen 4e-fe/5e-fe engine without causing detonation or damage on normal pump gas?

How can you check your normal unleaded gas octane level?

[toyotasera.co.uk]

Ask your petrol company what the RON or MON rating is.

[Zafar16]

I did that but they dont know. (Funny isnt it?) Any kind of test you can perform?

[Zafar16]

would 10.0:1 be too high?

[toyotasera.co.uk]

depends on the RON rating of your locally available fuel!

No you can't easily test fuel.

If its really poor quality fuel, the compression ratio will be too high.

If its really good fuel - eg 100RON Japanese fuel, it will be fine,

If fuel quality is variable - then better be safe than sorry.

[Zafar16]

I am planning on making a hybrid engine from a 5e-fe dis bottom end and a 4e-fe head(1st gen 5e-fe very rare). I have found the difference in compression between the engines is the amount of crown on the pistons. roughly 2mm crown=9.8:1, 1.5mm=9.6:1 and 1mm=9.4:1(figures for 5e-fe engines) I want to use the normal head gasket(TRD difficult to import). I will be using the 4e-fe pistons as the crown is 3.5mm which i can then shave to get the desired compression.

The 4e-fe is 9.6:1 no problems with fuel.