True, there is no "cave" carved out left to right like on some egnines. Any idea why some do carve out a cave and others don't?

Of course, there is more space/volume in the case for fuel/air mixture, but that still does not answer why some do and some don't make a cave/enlargerd chamber.

In my oberservation the following modify this area to the maxiumum: Max Power, Capricorn and Mag

And the following do not: MH, Murnan, JP, IDM mods, Nova tuned, OS tuned. These guys do carve out/grind/polish the existing channels like in pic 14, but they do not carve out the whole chamber area left to right.

Fuel consupmtion could be one reason, max or optimum scavenging could be another -- but anyone got an more substantial ideas why some do and some don't do this? Lets hear them!

turbo button,piston,crankcase inlet still can do some mod

But how much is the gain?

smoother from mid to high and engine don't sound struggle

.21 RS7
 

According to the write-up, ORCAN's new .21 RS7 is tuned for 16% fuel.

The engine comes with 0.4mm head shims.

If I were to run this engine on 25% fuel, do I need to increase the shims? If so, by how much?

Thanks in advance.

Sam

Hi Sammies,

I asked the guy behind ORCAN and this is his reply

---///
The RS7 is with 0.40 shims perfect for 25% nitro at sea level and also for 16% by 300m above sea level.

If they drive with 16% at sea level they can drive so, or can put 0.05 shim out maximum 0.10 so they have with 16% nearly the same power as with 25%

Hmmm...... something looks wrong to me....

Normally the higher from sea level the lower the head clearance or the more nitro you have to run. Your answer is telling otherwise......

Interesting point Roelof. Thanks for sharing.

I will check.

"Put out" is not clear (add or remove) perhaps due to translation.

getting the same power like 25% nitro running 16% is to remove shims and getting more compression. The bang with 25% is better then with 16%.
Thats is what i understand from h answer. remove 0.05 shim to max 0,1 shim.

HHH I have a question:

I think you had a GT3 C MH Orcan not?
What is the difference in performance compared to Orcan Orcan RS3 with GT3 C MH?

The RS3 has more power and revs higher. I only have one liter through after break-in and race tune, but initial observations are that there is much more low end (I have to be very gentle out of corners), similar or a little less mid and then tons more top end. The RS3 is uses more fuel but is easier to tune and idles better than the GT3C.

The revs are so much higher can gear lower and ORCAN recommends changing the conrod and wrist pin after 3 liters on large tracks and 5 liters on small tracks! The engine uses the 7601 rod which has never been a long life rod.

Even though I am notoriously greedy when it comes to power the RS3 could have too much power and torque for some people. I am tempted to say it is too powerful for my taste, but I am still experimenting with ways to get more traction/less wheel spin and tuning the engine to make it more mellow.

You should try for yourself as the RS3 is a beast!! I need more time to say for sure. I love the GT3C and it has really served me well. I need more time to either get used to or figure how to better handle the RS3. My buddies are going to give it a try soon and we will see what their reaction is.

the rod are compatible with flash PT(N2) and more reliable

the 7604 rod is 'fatter' at the lower end and the clearance between crankcase and rod is very small.
so you risk to hit the rod in the case at high rpm.

I was told the N2 (7604) does not fit or work, but I have not tried it.

i had tried in my nova 3ST,it's work well.maybe you need to do some measuring since this engine is nova LL3 based