Originally Posted by wangcc61
I have some STS engines for awhile and finally taken measurement of their porting. I modified the exhaust port and intake timing on my engines for experiment. The result is better top end but slightly less punch. Good for smooth and large track. I just want to share the data to STS fans. Ok. here they are.
STS RS3
Schnuerle: 112 degree
Boost: 108 degree
Exhaust: 162 degree (mod.)
Induction(stock): 207 deg. (30 ABDC - 57 ATDC)
Induction(mod.): 212 deg. (30 ABDC - 62 ATDC)
STS D5
Schnuerle: 118 degree
Boost: 116 degree
Exhaust: 162 degree (mod.)
Induction(stock): 204 deg. (30 ABDC - 54 ATDC)
Induction(mod.): 212 deg. (30 ABDC - 62 ATDC)
I will take the measurement of my D3 next time.
I got the following data from rc magazine
Collari .12
Schnuerle: 114 degree
Boost: 114 degree
Exhaust: 159 degree
Induction: 213 degree (32 ABDC - 65 ATDC)
It looks like the induction of STS opens 2 degree sooner than Collari .12
By the way, if the crankshaft is lightened, say 1 or 2 gram, the engine will have quick acceleration from low rpm to high rpm. But the idle might not be as stable as stock one. Just need to tune the bottom and idle needles again, and it will be fine. Not sure if it is legal for ROAR to lighten the crankshaft....
I just want to add more info to my own post.
I got a D3R from Geoff couple months ago and I believed it was modified before I got it. Anyway, this engine is still running strong after 3 gallons and here is the measurement of the port timings.
STS D3R
Schnuerle: 116
Boost: 114
Exhaust: 156 Degree
Induction: 236 deg. (24 ABDC - 80 ATDC)
If you noticed the induction timing, it was retarded so much compared to stock one. I also noticed this D3R has different chape of conrod (both side of the conrod have grooves), and the fit between the piston and sleeve is tighter.
By the way, I also took the measurement of the new parts in case you need to compare to your engine to see if it has worn out or not.
Conrod: 4.32mm in diameter for crankshaft pin, and 3.94mm in diameter for wrist pin.
Wristpin: 3.88mm in diameter.
Crankshaft pin: 4.28mm in diameter.
The inaccuracy is 0.01mm to 0.02mm
Oh, last week I try to run-in the rebuilt D5 (6 gallons through before rebuilding; only replaced the P/S/Rod), it started to eat my glow plugs. After inspecting the components, I found out the crankshaft pin was only 4.11mm in diameter and I saw the damaging on the piston and button head due to detonation. I guess the worn out crankshaft had the same result as taking out the head shims.
