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Compressor Ratio 11.5:1 and boost

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I have a motorcycle with compressor ratio is 11.5:1 .

It is possible to upgrade turbo for this engine ( keep stock internal engine and using Ron 95 petrol ) .

Thanks for addvances

The answer is that yes, you will be able to turbo the engine even with 11.5:1, however on a 95 octane fuel you are almost certainly going to be knock limited so you will need to be quite careful with your tuning. I'd also suggest that you're going to want to keep the boost quite low (I'd start with around 5 psi) in order to avoid knock and the requirement for excessive ignition retard.

Some kind of this, planning to upgrade into ram air intake instead of turbo charger. Is it advisable for 1 cylinder all factory parts? Currently using 97-100 petrol gasoline

At best, ram air - if you mean an opening to the front of the vehicle with a direct feed of air into it - is worth only a percent or two, so should have negligible affect on the engine. The main gain is usually from the air being cooler, denser, but as you've a motorcycle the charge will already be close to ambient.

Is it worthwhile? Maybe if chasing the last percent or two, but a decent feed tot he airbox is going to be very near as effective and reduce the chance of swallowing a stone.

Thank you Gord.. do you have any idea how to make air denser on motorcycle?. My custom airbox now is having direct intake from front then feed to airbox, before air filter

The only way to make air denser is to cool it (and you are already at ambient temperature), or compress it (super charger / turbo charger).

Thank you David., I will try to add more modification on my bike.

Basically, with a 'ram air' intake you're trading air velocity (relative to the vehicle) for pressure in the airbox/plenum - at 100mph (160kph) it's in the range of 1-1.2% greater density and hence power/torque potential. The greater the speed, the greater the gain. There are formulae on-line for the optimal airbox size.

The main benefit is in the air temperature being at ambient rather than potentially picking up heat as there is a ~1% loss/gain in density for every 5C change in air temperature, with colder being denser.

You have several enquiries about single cylinder engines, is/are they for practice and road use or do you have a race series to compete in - I know there are several around the worls based on 'cheap' bikes and some have unlimited classes. Either way, I'd suggest looking at exhaust design as a correctly made expansion chamber may be very helpful, same with inlet tract diameter and length. Some carburetors can also gain from careful modifications to improve flow and response, but I gather you've a form of EFI on your engine? I assume you've done head/port work, valve and seat re-shaping, camshaft upgrade if applicable, etc?

Hi Gord, thank you for your suggestions. I'm using EFI 150cc bike, for both road and small track.