if you build a bottom end that can handle it, why cant you run say a 9:1 compression and 30psi on a zetec turbo for example? surely this would be more drivable off boost ect..

explain

 

det is the problem i belive and the increas in temprature will break the block .maybe

 

what if the block was decent?

surely it can be mapped so it doesn't DET?

 

i know fook all about zetecs but it isnt a problem on a yb

 

if you want to high compression run methanol ur get a stupid increase in power without the det!

 

surely if it can be run on a YB it can on zetec?

 

er....itll just be harder as there will be more heat,so youll need more fuel and cooling! and probably heavier duty components such as hg i would have thought as more heat/pressure etc

 

The An rover runs 45psi on 10:1 comp according to steves very good magazine editorial skills.

 

IMO 30psi on a 9:1 comp engine sounds like asking for trouble. Would have thought it would det its tits off?

 

Ian @ Racetek runs 2 bar on 9:6:1 comp I think but thats a yb.

 

ive been running more comp than that for over 4 years pal and used up to 2bar of boost on it

 

Ian used to run circa 9-1 but not anymore lo comp now i beleive.


High comp ='s mental peak boost but has to tail off late RPM or det det det...unless on rocket fuel.

 

And even when on rocket fuel......

 

mine doesnt - unless i have the restrictor in, without it will hold 2 bar to the limiter

 

...billy....you can run more boost the higher the octance....obviously you have to still tail it off but not as low

 

Markk, where's your limiter and what fuel injectors, turbo??

That was my point

 

Oh yeah its still high comp I think but not as high as 9:1.

 

hmmm.. interesting

 

You need a way to combat det, ie run rocket fuel, on pump fuel its a nono.

Next problem is huuuuge in-cyl pressures, so you need a properly mega strong engine (inc block generally).

Long duration cams and huge exhaust housings will help too, but frankly, i dont see the point in most cases.
The long duration cams and huge ex housings will push the boost threshold mega high, so although it will drive like a standard n/a cammed engine until it comes on boost (wowee, 100bhp on a good day from a 2litre sub 4500rpm), it wont come on boost till higher up.

Personally id rather run lower comp with smaller ex housings and lower duration cams, so it wont have quite as much power off boost, but who gives a fuck if it comes on boost sooner.

Hi comp has its uses, but for road cars running big bhp per litre on pump fuel, its pointless/useless IMO.

 

Cheers for clearing that up so would you need Nikasil liners and billet steel crank and rods to run mega comp, mega boost?

 

Probably, but more than that still, as said.

 

I was just thinking of the bottom end side of things.

 

Well yea, bottomend wise thatd be the way for ultimate strength.

Maybe some clever shaping of the piston and combustion chamber to minimise the squish area and avoid all sharp edges too, to help combat det.

 

Cheers mate.

 

bill

 

Thanks

 

always love these 'high comp 'posts

 

 

Thats compleltey wrong.

The only reason you need to peak boost and then tail it off is injector cyle generally.

Engines get less volumetric efficient at higher RPM, therefore at higher RPM you can get away with massive boost on a high compression engine.

Thats what a lot of jap motors do, especially the honda turbo boys.