2.4E Compression boost

Luke Hudson · 10-17-2005, 12:02 AM

Hi Guys,

My grand plans to build a 2.5 short stroke have been scuppered by a realisation that I don't really have the time or the expertise to do it myself, and the fact I bought a new flat which needs a bit of tlc. However my 2.4E enigne is still getting close to needing a rebuild, as such I'm keeping this cost effective and just going to swap my 2.4E pistons from some 2.2's to bump the compression ratio.

My question, I have E cams, ports etc, and matched MFI and don't want to fit S cams (I like torque) so should I be looking for 2.2E pistons, or will 2.2S pistons be better?

Should I be looking for Mahle pistons ONLY or do JE make them too? Any idea's on piston prices?

Thanks

Luke

Henry Schmidt · Henry Schmidt's Garage

Oversized JEs are new and easier to find. Either way you will end up with a nice combination.

With the JEs you could go up to 87.5 by boring your existing cylinders. JEs cost about $1000 in any size.

There is another option. Malvern Racing here in the states offers Cosworth pistons for a little more but what a sweet piece.

Cheers

Luke Hudson · 10-17-2005, 05:27 AM

thanks Henry,

I'll check out Malvern Racing to see what they have

So would the E or S profile pistons be the way forward given I'm keeping the E cam? (or are they the same?)

Luke

Henry Schmidt · Henry Schmidt's Garage

With "E" cams I would try to limit the compresion ratio to around 9.5 to 1. for two reasons cams and fuel quality.
2.2 "S" pistons on a 2.4 crank would put you way over that target figure.
From a compression ratio point of veiw only the "E" pistons might be better.

mpdevelopment · 10-17-2005, 07:31 AM

Henry 87.5 seems BIG for 84mm biral cylinders?

Luke Hudson · 10-20-2005, 12:15 AM

thanks Henry,

so it's a straight swap for 2.2E profile pistons , no port work, no change to the cylinders but will probably need to tweek the MFI pump a bit. sounds nice and simple!

Luke

davidppp · 10-20-2005, 03:09 AM

Hello Luke.

The exact CR when fitting the 2.2S piston on the 70.4mm crank is a matter of some debate...and mystery..

Have a look in Bruce Anderson's book for some of this..he reckons 9.66....which does eem at variance with the factory figures,..it seems the factory may have also overstated some other CR's..
FWIW I have just such a motor running in the 914 just now, with 9.8:1 and retarded E cams etc...

It runs fine on the LRP type petrol we can get in UK, but would pink when lugged at low revs when very hot on the cheaper stuff..

It is a very nice fast road motor, coming on hard from 3000 to 7500...

I am sure the S cams would allow a higher CR still..

Kind regards
David