compression, how high is too high on 98fuel.

[SuperDave]

The 2ZZ-GE comes with 11.5:1 pistons with the high cam duration of: IN 272* EX 292*.

No one runs higher comp pistons without tuning on this motor so is hard to say how high it can go with 98. Some Americans are running the TRD 13:1 pistons on (converted to our system) 98 octane.

[ed]

piston and cams NEED to be considered, designed, and manufactured together. figure out your DYNAMIC COMPRESSION - everything is dependent on that. timing wont save you if your cyl pressure is too high. get an engine analyser program to calculate your dynamic cyl pressures. if youre going to start playing with stuff like this, please dont try and "do the cams first" and sort out other bits later. build it once

PS i HATE stage 1/stage 2 cam nomenclature!! lol

[fixeruperer]

what about 3/4 race cam

[jeffro ra28]

PS i HATE stage 1/stage 2 cam nomenclature!! lol

Likewise Ed.
e.g. full race port job, full race cams, stage 5 portjob, stage 5 cams! full sick massive lumpy cam!

I actually dont like advertised duration either

[The Real Roadrunner]

I actually dont like advertised duration either

but it will atleast give you some info.

ie : if you know the total duration aswell as the duration at 50thou it will give you an idea of how aggressive the ramp is.

but stage 1/2/3/4/5/6/7/full race, is just F'n ghey.

if they wont tell you the real numbers then go elsewhere to get your cams

cheers
linden

[jeffro ra28]

Its ok if you have BOTH figures.
But whats the point of comparing the ramp speed to only .050"? It means SFA when you have another .400" odd to to go.
Sure its great if you are trying to decide between brands of cams, most people may choose the "faster" ramp acceleration for performance. But it is really only telling you how aggressive it is for the first .050" of lift
Good luck trying to obtain TOTAL cam lobe acceleration from the manufacterer Probly be easier to spend 6000 aud on a cam doctor.

[The Real Roadrunner]

^^^ true,

i wanna see some poor bastard work out the ramp angle, duration and lift on my RS6 engine. roller followers would make life very interesting for the poor bastard that needs to do it shortly.

[jeffro ra28]

Hmm. I just had a rethink. Ramp speed up until .050" is still very important as we can never open a valve instantly in just about all engines.

Oh and linden, anyone that knows how to use a cam doctor well will turn that task of yours into a peice of piss. I had to work out the valve timing events and accelerations of a KTM 250sx with a pivoting knife type roller, slightly different to a 4g63 style. Having a cam doctor made it a peice of piss. The program does it all for you! You need to find someone with an "audie" cam doctor.

Anyhow, sorry for veering off topic

[nilprospects]

i'm subscribing to this thread, as i am in the planning stages of high comp, cams, head porting, springs, inlet manifold and crank angle sensing(no dizzies)

[Celica RA45]

im using 13.5 to 1comp on 98 fuel with cams that are 262 at 50 thou and 545 thou lift on inlet and 520 on the exhaust 3sge motor with cam control ,but can only get away with 27 degrees total ignition .shell v power was 29 degress and ELF lms was 32degress but between the lot from 98 to 100 there was 3 kws and from 100 to the ELF was 4kws

[merc-blue]

This question is such a dreamers question.
Firstly whats you engine build budget.
and what is the engine build for?
Who is building it and where.
Who is tuning it and where.

The difference between a Good realiable top HP engine and and hand grenade has very little to do with ports, compression, cams whos pistons you use or which rods you use.

a engine is 40% hardware 30% knowledge and 30% skill.

you need to have a set goal. and a budget which allows you to obtain it.
what i cant see is why you need to push the compression so high just to take ignition out of it..

safe compresion isnt about a number its about combustion chamber and crown design abit of correct port flow. good valve seats and a proper ignition,

A engine is a package and you need to balance all things involved.
On all our historic engines we dont run more than 12:1 really even on ELF purely becasue we cannot get a good combustion chamber design to allow higher. while the same fuel in a built up Duratec would alow a much higher compression.

Answer my questions.


P.S are you the same 13B in a MZ10 guy?

[jeffro ra28]

This question is such a dreamers question.
Firstly whats you engine build budget.
and what is the engine build for?
Who is building it and where.
Who is tuning it and where.

The difference between a Good realiable top HP engine and and hand grenade has very little to do with ports, compression, cams whos pistons you use or which rods you use.

a engine is 40% hardware 30% knowledge and 30% skill.

you need to have a set goal. and a budget which allows you to obtain it.
what i cant see is why you need to push the compression so high just to take ignition out of it..

safe compresion isnt about a number its about combustion chamber and crown design abit of correct port flow. good valve seats and a proper ignition,

A engine is a package and you need to balance all things involved.
On all our historic engines we dont run more than 12:1 really even on ELF purely becasue we cannot get a good combustion chamber design to allow higher. while the same fuel in a built up Duratec would alow a much higher compression.

Answer my questions.


P.S are you the same 13B in a MZ10 guy?

Think about the actuall question this guy is asking. He wants to know peoples experiences on what they have acheived with what motors. He has given the example of 1uz motor and clearly this chamber can be made to work with more compression.

Its not like he has asked, Whats the highest compression any motor can run on 98 ron fuel? Thats just stupidity

People have expressed their experiences and that what he is after.

Also to, i think the difference between a top HP engine and a hand grenade has EVERYTHING to do with your compression, ports, cams, pistons and rod choice

[af300e]

The difference between a Good realiable top HP engine and and hand grenade has very little to do with ports, compression, cams whos pistons you use or which rods you use.

Yeah, the current toyota F1 motor is probably just a stock 1uz but the bolts were tightened by an AWESOME mechanic....................


I sort of know what you mean, that even the best components thrown together by a douche bag mechanic are not going to result in a reliable system, but I'm with Jeffro - the quality of engine components in a max/top HP application are much more than a little important.

Your post is a bit interesting, you probably need to qualify that statement a little.

[merc-blue]

yeah i do, what exactly im refering to is a proper race engine build.
There is no doubt that your going to have top end compnenetry in it,
But getting it built be a knowladgeable engine builder will make you more horsepower than having the absolute best rods and pistons.. who knows there may be a fatal flaw with valve position. you could spend 50 grand on a engine and the bloke does know that you need to offset grind the valve re-slevel the valve tubes to move the exaust port over 2mm so your down 70 HP on the guys who may have only spent 30 grand on there engine but the bloke who built it knows what he was doing.

I have watched one of aussies better engine builders (has built the engines that won the past 2 V8supercar championships) throw together a Ex-stone brothers engine for a ski race boat and the attention to detail and understanding of the full dynamics of that particular block/engine was amazing..
He was like oh the 3rd main bearing needs a extra thou clearance becase at high revs the block deforms in a way which it clamps down abit... etc or this particular driver uses heaps of clutch so i will tighten up the thrust washer and champhor the enges to increase oil flow to it to ensure it doesnt cook the crank..

That sort of knowledge about a engine is what will build you the best possible engine for your money.
habib and bambis motorworks will probly be able to build the engine out of the same components but you will probly be down a fair chunk of horses and on a long straight like darwin it will tighten up the 3rd main every time and by the end of the weekend have fubared the crank, and possibly the rest of the engine.

hope this clarifys what im talking about...

Im just trying to help the underlying issue of why. and the means of doing so, as opposed to giving a number and letting him run with that

[abently]

Lets be honest here, the amount of power to be gained by an increase in the CR is SFA unfortunately...

The advantage of increasing the static CR is in reality just to make some wild cams work better.

Unfortunately, if you want real power from an N/A Engine it needs RPM's. And then the Engine will probably be louder then the exhaust......