13.5:1 Compression

[Wobba]

Hi. I know I can go higher than 12.5:1, which is what I have now.

Is there anywhere that does 13.5:1 pistons anywhere for the F7R? Or higher?

Thanks :D

[dkrevs]

Are you building a BTCC engine Wobba?

[cliokongen]

You can have pistons made to order - your choice really.... :D

A small selection...
http://www.jepistons.com/OrderInfo/Index.aspx
http://www.ariaspistons.com/custompistons.html

M

[Wobba]

BTCC engine??? NO! Building a Wobba engine!!!

I am just looking at the limits of N/A F7R tuning, where the car is still road legal and driveable.

I am looking at what I can do with this spare F7R I have here before I buy another Mk1 to dump it in

I think Sodemo F7R's made 300ish BHP?

[dkrevs]

Sodemo engine used in BTCC and Megane MAXI was destroked from 93mm to 90mm. Clio MAXI used 93mm stroke. Those engines were great but as any other thing that is on the limit, didn't last very long(unusable for daily).
Here an interesting project, although on F4R:
http://www.cliosport.net/forum/showt...ting-big-power

[chip]

More compression is only going to be useful if you dont have enough compression at the moment, sounds like a silly statement, but what I mean is that there is an optimum compression, higher isnt always better.
If you go too high you will start needing to pull out timing.

Two ways to avoid that, either you rev it harder so you are squeezing less charge but more often, or go onto a hotter fuel.

Neither of those things is condusive to being a road engine.

If you want to really rev it, you'll need mega short 2 ring pistons with hardly any skirt to keep the weight down, and thats going to mean very frequent rebuilds.

300bhp sort of ballpark from a 2 litre engine isnt particuarly difficult to achieve in that its been done before so lots of knowledge around to copy so at least you wont have to build 20 engines to get there (ie no development needed), but it is very expensive and doesnt last long though.
For example, to make use of the rpm that 13.5 is suited to (9K+) you're going to want to be dry sumped and solid lifters etc


Definately possible, but wether its actually worth the money just to create something that doesnt last many miles is of course your decision to make.

[Wobba]

The mapping we did at Emerald showed we had to shave a heck of a lot of advance off to avoid det compared to the previous map using a standard compression engine. Made good figures though.

I think for the big figures I'll have to go the forced induction route!

[chip]

The mapping we did at Emerald showed we had to shave a heck of a lot of advance off to avoid det compared to the previous map using a standard compression engine. Made good figures though.

They'll be parts in the rev range where the shaved timing will cause a drop in power, and when going from 12.5 - 13.5 that part of the rev range is upto about 7Krpm, lol

I think for the big figures I'll have to go the forced induction route!

Yes thats a far better option, but bear in mind that with torque comes dead gearboxes if you are going to use the car hard on the track, hence im going honda engine and box with mine before I bother tuning it.