Turbo or supercharged 2Ts?

[TZ350]

That's probably 6hp more than any bucket has hit the track with.

30 hp has been out there.



And ended when the ring jumped the peg and turned into the exhaust port.

And the 31hp version expired at Kaitoki, thats when we learned that if you run a 2T in the power band on part throttle you need to retard the ignition timing to avoid detonation. Who would have thought you needed to do that! another lesson learned.

copper cooling fins on what is hoped to be a mid 30's hp engine, or maybe even the first to touch 40.

The 30 and 31hp engines didn't seem to suffer the same power fade as Kels does at 29hp. Kel has some very effective looking air scoops and I expect his bike will run stronger for longer when he incorporates a bit of copper into the air cooling system.

[sonic_v]

310379[/ATTACH]

Been close to that already with the air cooled Suzuki GP125.

From what I can see, 70cc for turbo 2T's still looks about right.

TZ, Hp is not directly proportional to cylinder capacity in two-stroke engines. It actually follows a 2/3 rds power law.

Hence for a 70cc v's a 50cc you have 24 * (70/50)^0.6667 =24 * 1.251 = 30.0 hp

Basically hp is directly proportional to cylinder bore surface area - hence the reason over square 2 strokes are so poor.

[TZ350]

TZ, Hp is not directly proportional to cylinder capacity in two-stroke engines. It actually follows a 2/3 rds power law.

24 * 1.251 = 30.0 hp

(Using the Buddfab turbo 50 that makes 24hp as an example Sonic_V suggests a turbo 70 might achieve 30hp)

Thanks, so 70cc is still looking good, maybe even a bit on the small side because some F4 2T motors have made over 30hp now and it would take a lot of work to develop ones 70 to anything like the Buddfab motor.

[lodgernz]

Interesting thread, but if I might be permitted to add a note of caution:

4-stroke + supercharging = blowups = oil on kart tracks = end of bucket racing.

Just sayin'...

[TZ350]

Interesting thread, but if I might be permitted to add a note of caution:4-stroke + supercharging = blowups = oil on kart tracks = end of bucket racing. Just sayin'...

Plenty of NA 4T's have dumped a shit load of oil on the track and then some 4T riders have had the audacity to point the finger at the blowback from 2T carbs.

In fairness I guess 2T's blow back all the time and 4T oil dumps are mostly spectacular localised events or in some cases long snail trails as they slowly bleed to death.

A broken rod from a forced induction 2T probably won't dump as much oil as a similar 4T blow up but I can see what you mean.

[TZ350]

The proposed change to allow super/turbo charged 2T's

Write to MNZ to have your say.

http://www.mnz.co.nz/docs/default-source/regulations/2015-summary-of-all-proposed-rule-changes-for-websitea97dfb456e51694ab575ff0000938921.pdf?sfvrsn =2

The proposed change is on Page 5

4T's have a forced induction option now and its proposed that 2T's have the same opportunity. MNZ would welcome sensible input that would help them to judge the merits of the submission.

[speedpro]

A broken rod from a turbo 2T probably won't dump as much oil as a similar 4T blow up but I can see what you mean.

Speaking from experience, breaking a rod and poking a hole in the cases "may" cause a few drops of oil to fall out of a 2T, unless you manage to poke a hole through to the gearbox. Done it on the track, don't actually recall any oil but I did wake up strapped in a stretcher. Done it on the dyno where it poked a hole in the gearbox as well. It still only leaked a couple of spoonfulls

[speedpro]

It does seem to me to be another option for Rob to explore with regard to destroying 2-stroke engines

[jasonu]

(Using the Buddfab turbo 50 that makes 24hp as an example Sonic_V suggests a turbo 70 might achieve 30hp)

Thanks, so 70cc is still looking good, maybe even a bit on the small side because some F4 2T motors have made over 30hp now and it would take a lot of work to develop ones 70 to anything like the Buddfab motor.

How many of the 30 and 30+hp Bucket motors have proven rideable or reliable and have won championships and or GP's? The winning bikes (at the present time) make 24-27hp. Using the above calculations a forced induction 2T f4 motor capacity limit should be around 60cc.

[TZ350]

How many of the 30 and 30+hp Bucket motors have proven rideable or reliable and have won championships and or GP's? The winning bikes (at the present time) make 24-27hp. Using the above calculations a forced induction 2T f4 motor capacity limit should be around 60cc.

Personally I wouldn't expect a 70cc 30+hp turbo 2T to be any more reliable and a winning combination than the 30+ NA 125 air cooled 2T's, but the turbos would be great learning experiences if you're into that sort of thing.

[Henk]

Personally I wouldn't expect a 70cc 30+hp turbo 2T to be any more reliable and a winning combination than the 30+ NA 125 air cooled 2T's, but the turbos would be great learning experiences if you're into that sort of thing.

Could you dial in some reliability by backing off the boost? If full noise 60cc gets the required HP in a pull pin stand back engine, then maybe 70cc but not quite so on the edge is the right number.

[F5 Dave]

Sweet can I have a bigger engine? Those mito and Apr 125 do about 25, 26 std road bike and touching 30 with carb and pipe. That'd be enough for me.

[bucketracer]

Sweet can I have a bigger engine?

Sure you can have more power, no one is stopping you, instead of looking for the easy options and bigger capacity with stealthy rule submissions, its Buckets, you just have to apply yourself and build a better motor.

Maybe fitting a 70cc big bore road kit and turbocharging your Derbi could put you at the very sharp end of F4, it is something to think about.

[F5 Dave]

The bigger CC request was above, I was just echoing it to show it's absurdity.

And my Derbi is an F5 bike. Not everything rotates around F4.

[husaberg]

Im all for 2t turbo but for f4 it has to mirror the commonly accepted 1/2 displacement. ie 50cc only.