Turbo or supercharged 2Ts?

[kel]

Oh is this the 85 mx thread? Oh wait, same rules should apply to this, only fair...

Struggling to see the connection. I'm not against the 85 MX per se, but this is completely different. Non competition motors with non competition turbos or blowers, could it be any more true to the spirit of buckets? Just agree on a sensible cc limit and get it done. I won't block this one

[F5 Dave]

I wouldn't block it either if I knew what a sensible limit was. But I don't. A 70cc Derbi with a blower wouldn't need much pressure to do the job you'd think.

[husaberg]

I wouldn't block it either if I knew what a sensible limit was. But I don't. A 70cc Derbi with a blower wouldn't need much pressure to do the job you'd think.

Double of original power output with each additional atmosphere of boost is generally considered a good rule of thumb........

[F5 Dave]

So say 19hp at 15psi would double?

[Grumph]

So say 19hp at 15psi would double?

And IMO, life expectancy would halve....

[speedpro]

life expectancy would halve....

[speedpro]

Double of original power output with each additional atmosphere of boost is generally considered a good rule of thumb........

1 turn on the waste gate screw was worth about 30hp. 3 turns resulted in a noticeable improvement

[husaberg]

So say 19hp at 15psi would double?

And IMO, life expectancy would halve....

AS a general rule if it was 19hp then at 15psi boost it could be expected to produce 28hp without any additional tuning assuming it could be keep in one piece and thermally sound.
Grumph said life expectancy would half ....perhaps.
but it would still expect it to last far longer than a engine of similar size tuned using traditional forms of atmospheric tuning to the same output would.

1 turn on the waste gate screw was worth about 30hp. 3 turns resulted in a noticeable improvement

So what did that add in boost and Hp terms Mike ..........

[Grumph]

1 turn on the waste gate screw was worth about 30hp. 3 turns resulted in a noticeable improvement

Quite agree - but we're not talking a big 4T with a forest of cylinder studs, thick wall gudgeons and forged pistons...
Most small 2T's available for this use will have 4 X 6mm cylinder studs, maybe 12mm gudgeons and pistons which won't stand the heat.
You and i and a few others can do the engineering required to bring the basics of the motor up to scratch, it won't just be buy from a catalogue....
I'm quite prepared to support the proposed remit, but have no intention of going down this track myself.

[F5 Dave]

AS a general rule if it was 19hp then at 15psi boost it could be expected to produce 28hp without any additional tuning assuming it could be keep in one piece and thermally sound.
Grumph said life expectancy would half ....perhaps.
but it would still expect it to last far longer than a engine of similar size tuned using traditional forms of atmospheric tuning to the same output would.


So what did that add in boost and Hp terms Mike ..........

Erm so in what way is double 19hp = 28? Has the rule of thumb changed or did the math get a typo?

[husaberg]

Erm so in what way is double 19hp = 28? Has the rule of thumb changed or did the math get a typo?

Me math got a typo.....mine erngerish is far more betererer.....
it was meant to be 38

Later when you think about it the rule of thumb although it excludes some thermal issues makes perfect sense.
if a NA engine makes Y amount of power (at normal atmospheric pressure) if you double the atmospheric pressure it equals Yx2 hp

[Yow Ling]

Dont forget
21 degrees C inlet
60% compressor effieiency
Compressor pressure 14.7 psig
Compressor Output air temperature 131 degrees C

Very hot engine

[husaberg]

Dont forget
21 degrees C inlet
60% compressor effieiency
Compressor pressure 14.7 psig
Compressor Output air temperature 131 degrees C

Very hot engine

But that's what intercoolers are for though...........
To make the same HP with traditional atmospheric tuning also create a fair bit of additional heat also.......
Any ic engine is at its very essence a pump.

[TZ350]

I wouldn't block it either if I knew what a sensible limit was. But I don't.

I am not sure what a sensible size is either, but the way I figured it, the supercharged 4T limit of 100cc is 2/3rds the normally aspirated 4T. So 2/3rds of 125 is 82.5, but there is talk of MX85's so I chose a 70cc limit for 2T forced induction.

70cc for 2T forced induction? would that seem sensible....

[mr bucketracer]

I am not sure what a sensible size is either, but the way I figured it, the supercharged 4T limit of 100cc is 2/3rds the normally aspirated 4T. So 2/3rds of 125 is 82.5, but there is talk of MX85's so I chose a 70cc limit for 2T forced induction.

70cc for 2T forced induction? would that seem sensible....

the other way to look at it is a 100 4 stroke is a f5 bike , with a turbo its a f4 bike , maybe should be the same been the 2 stroke been 50 cc ?