Corse-R

Uhm. Some interesting points that may shed some more light and some more Q's to put some life on this thread that I find very interesting.

1. EFRA doesn't limits Exhaust transfer height. Ran a sleeve on a very large track (Lostallo - Swiss) with more than 4.6mm of transfer height (low-end was completely killed, but talk about high speed -engine sound was wickening on all the backstraight- ).

2. That slightly longer stroke will be beneficial (IMHO) because the increased dwell time at TDC, powerband will be different from RS12/NS12, but I bet that new engine will be 'something boring' on high traction tracks due to their sweeter powerband and how develops the power (Attention to this...). Probably will not be soft at low-end and more like an electric motor like. Think on it like a truck engine with an almost flat torque curve.

3. Figuring a longer dwell time (uhm, a slightly longer conrod to round this will be perfect), engine will be slightly more fuel efficient, because it has more time to push the piston downwards, probably can authorize more static CR to make it more efficient.

4. Longer stroke means higher linear velocity of the piston and more inertia, so 'theorically' less ability to hold the high rpms that we're getting nowadays.

5. Trying to figure the timing of an engine who no one has seen it is futile, better to wait to see it and degree it. But much probably will be quite similar with more 'lobe centerline' on their distribution scheme talking in the '4 stroke jargon' - not much, but probably make a difference. On the .21's this made their magic and made it more controlable.

Corse-R

Location of windows and their height affect to the distribution scheme globally, a change of .25mm on the transfers makes it a great difference.

Probably (and I'm making some guesses) their induction transfers will be slightly larger (I bet about .10mm higher to have more induction time), but located on the same 'height' or timing.

Read it on the traduction that altavista made from the page that sleeve will be slightly thicker (2,5mm thick), this changes too the shape of the transfers, making specially the boost more steeper (any want to bet that they changed the boost transfer height too?)

Francis M.

iTrader: (2)

just by observing the way engines were
teched for the roar nats 4.5 mi. port height
was measured from bottom dead center.
they would set the dial at zero from the
pistons bottom position and they would
raise the piston 4.5 mil. and if the ehxaust
port is still open then the engine was failed.
that is why you had engine modifiers shaving
the outside lip of the sleeve so it will sit lower
in the casing however mil. they went overl.
So i guess for roar they measure how much
exhaust opening you have from the pistons
upward stroke till it is fully closed.

as for crank timing they did not measure that.
they just took a look at the diameter of the
crank outlet facing the backplate.

EdwardN

iTrader: (1)

The difference between your assumption and mine is-I work by degree in timing and don't realy care the height of the ports, the angle-yes very important point, but on engines which we already have on hands, no much we can do, just make them more steep, that is all. about te induction, I am sure new nova engine-the engineers put it on the way where it got to be. If somebody realy wants to change it-easy to go. It is realy questionable how much it got to be on induction and I am sure everybody has their own opinion, so here no way to discuse about it.
Location ( the same as timing duration) of exhaust port dictate by ROAR, EFRA, IFMAR etc regulation and location of transfer ports and buster are dictate by common sence design. If you decide to make timing duration let's say some number-it will automaticaly bring you to sertain place and you will not be able to change it. On the exhaust and transfer duration you can't make it open earlier and close later or opposite, it is semetric from both side, so realy doesn't metter location, just make sure you keep in regulations and common design sence.

EdwardN

iTrader: (1)

I hope I understood you right-you mean transfer, not exhaust.

Corse-R

Is a wrong way of measuring the exhaust port, basically because tech inspectors think wrongly that an exhaust port starts at the BDC (and sometimes this is not true).

For example. Nova engines have their exhaust port slightly over the piston at their BDC, don't know this measure, but think about 0.10 or 0.15mm over the piston at BDC, the measure isn't real.

Unique way of measuring correctly is to remove the sleeve from the crankcase and measure it with a machined 4.51mm feeler gauge. If gauge enters, the sleeve isn't legal, if not fits is legal. Simple and clear.

BTW: There's much hype about how to measure the port height and found many ways to measure it, some times and depending how measured a sleeve can be deemed legal or illegal depending on how is measured.

Corse-R

Uhm. sorry, is a deformation of thinking on Spanish and writing on english. Here to the exhaust port is literally named Exhaust transfer (whose correct name will be exhaust port). Sorry if this confused you.

BTW: Working on timing is the same as working in height, are two ways to find the same, but for avoiding the hassle of measuring and talking about exhaust events with a pair of degrees wheel is commonly named with the height (height of a known port can be translated into degrees and viceversa).

EdwardN

iTrader: (1)

I am working on different size of engines and different brands, so for me to remember in MM is sort of extra headache, so I prefeard to work with degree wheel.
Don't worry about english, my english much worse then yours At work I also have to speak in spanish too, that one is real sucks

EdwardN

iTrader: (1)

I think ROAR and EFRA and IFMAR rulls state-exhaust height is must to be 4.5 mm and it mesure from the highest point of the piston in BDC to highest point of the top of exhaust port on sleeve. So It can be done custom engine where psiton will go below botom line of exhaust port on sleeve and this method will be not correct (according to ROAR, EFRA, EFMAR ect).

AMGRacer

At IFMAR events the exhaust timing is checked with a derlin (or plastic) 4.5mm cylindrical bung which is inserted into the engine through the top of the sleeve. The piston is pushed down to BDC and if there is a gap between the top of the exhaust opening and the top of the bung it is illegal.

EdwardN

iTrader: (1)

This method looks absolutly correct.

EdwardN

iTrader: (1)

Any news from your nats?

AMGRacer

Rain. Bad news

EdwardN

iTrader: (1)

Yep, it is realy bad news. Any good prognosis for next couple days?

AMGRacer

Weather channel says getting finer. But they are usually wrong!!!

I hope they are right!!!