ORIGINAL: jaka
Hi!
Well, my opinion is that all .40-.46 sport two stroke engines (except the non ballbearinged engines) are more or less the same powerwise when you use them in a trainer with a 10x6-11x6 prop.
I know there are differences..like for instance over here in Sweden where we run Q-500 pylon using standard sport .40 engines (like OS .40 FX and Webra GT .40) and here the Webra .40 has got the edge.It swings a 10x6 prop (Graupner) at around 14000rpm (80/20 fuel)which is more than all other .40 engines do (we don't allow Nelson and Jett).
Regards!
Jan K
That is your opinion Jaka & you are perfectly entitled to it. My opinion is different.
Dave Geirke did exhaustive dyno tests on nine different 40 size engines, including five BB types & four plain-bearing types. The BB engines were:Enya SS 40 BB, Magnum XL .40 A2, MDS .38 FS Pro, Supertigre GS .40 & Thunder Tiger .40 Pro. The plain bearing engines were: Enya SS .40, OS Max .40 LA, Thunder Tiger .42 GP and Tower .40 R/C ABC.
In dyno tests, turning an APC 11-6, the five BB engines varied in RPM from 10,400 (MDS .38) to 13,000 RPM (TT 40 Pro) -- a 25% variation, & HP figures varied from 0.55 (MDS 38) to 0.95 (TT 40 Pro) -- a stunning 72% difference.
Similarly, for the same BB engines with a 10-6 prop, the RPM's varied from 12,900 (MDS 38) to 14,900 (TT 40 pro) & the HP figures varied from 0.79 (MDS 38) to 1.22 (TT 40 Pro) -- a similarly enormous 54% difference.
If you take the four plain bearing engines with an 11-6, the RPM's varied from 10,400 (OS 40 LA) to 10,900 (TT 42 GP) -- 4.8% difference, & HP varied from 0.53 (OS 40 LA) to 0.62 (TT 42 GP) -- again closer, but still a 17% difference.
With a 10-6 those same engines had RPM variations from 12,100 (OS 40 LA) to 13,000 (TT 42 GP) -- 7.4%, & HP varied from 0.72 (OS 40 LA) to 0.85 (TT 42 GP) -- a 12% difference.
When the engines were propped to reach their maximum outputs, the BB engine differences varied from 1.27 HP (Enya SS .40 BB)to 1.42 (Magnun XL 40 A2) -- a 12% difference, & the plain bearing engines varied fron 0.78 HP (OS 40 LA) to 1.11 HP (TT 42 GP) -- a huge 42% difference.
In my opinion, prop-fit & engine characteristics matter very greatly --- even for trainers.