View Full Version : forced air induction for Tzr

mick - n/a
21-Jun-06, 09:41 PM
I had been podering this idear for some time, can the power of the Tzr be increased by directly forcing air from the plemium preasure directly into the air box, im imagining that the jets would have to be increase significatley.

ok you Tzr exsperts ,whts the verdict.

team black - n/a
22-Jun-06, 01:28 AM
Yes it can be done, but you'd end up with a F2 craft, since it would be a forced induction system

mick - n/a
22-Jun-06, 12:53 PM
hi ewan its ricky

why would it become a f2 beacuse i am not changing the cc of the engine. it will still be a tzr250 but im just putting more fuel and air into the engine correct me if im wrong thanks rick

Nick Long - n/a
22-Jun-06, 01:09 PM
[quote im just putting more ... air into the engine [/quote]


That's what forced induction is. The HCGB rules are that you then count the engine as double the cc when deciding the formula.

This, however, was meant (and may even be written as such) for superchargers and turbochargers. Technically you would actually be using the fan as a crankshaft driven supercharger. On the other hand the plenum pressure is so low compared to a proper supercharger that the end result would be difficult to measure.


mick - n/a
22-Jun-06, 01:12 PM
so if i was to put forced induction on my craft i would automaticly be classed as a f2 craft http://hovercraft.org.uk/images/icons/smiley_icons/icon_confused.gif im confuzzled thanks rick

team black - n/a
22-Jun-06, 06:38 PM
The competition regs are on the download area:

"Pressure charged engines e.g.: supercharged, turbo charged, shall be rated at twice

their swept volume."

Paul Fitz - n/a
22-Jun-06, 07:10 PM
You evil lot. Stop winding them up http://hovercraft.org.uk/images/icons/smiley_icons/icon_surprised.gif)


Feeding air from the distribution plenum to an engine will not give any significant increase in power because the plenum pressure is about 1/100 of the additional pressure required to give practical "supercharge pressure" to any engine (4 stroke).

It is *impossible* to supercharge a *piston ported* two-stroke engine!! The first port to open in its cycle is the exhaust. The induction occurs whilst this port is open.

Graham Harvey - n/a
22-Jun-06, 11:23 PM
My mate did this guide on why supercharging 2 strokes is impossible (when the ports are inline, like in most 2 strokes)and explains the physics behind it if your interested with nice colourful, engineer friendly pictures!!

It is for small model engines for cars but the principle is the same,

http://www.glypo.co.uk/hiw-supercharger.php (www.glypo.co.uk/hiw-supercharger.php)


Sean Atterbury - n/a
23-Jun-06, 06:52 AM
What about "NOS" Would that work, and what are the regs on that, if any.

I was watching 5th gear last night where they kitted out a golf diesel and it practically doubled the performance, not so sure how long it would last for though.

In most high power sports nos is comming in as a must, maybe this too could be true for ours.

Just a thaught. http://hovercraft.org.uk/images/icons/smiley_icons/icon_biggrin.gif

tonybroad - n/a
23-Jun-06, 07:45 AM
Adding NOS would make it a special fuel engine and so it would be classed as F1 if i'm not mistaken - even worse

look at weight reduction to go faster - worked for me !!


andycollins - n/a
23-Jun-06, 07:56 AM
<table border="0" align="center" width="90%" cellpadding="3" cellspacing="1"><tr><td class="SmallText">Quote:</td></tr><tr><td class="quote">

look at weight reduction to go faster - worked for me !!


Hmmm. There's a feed line if ever I saw one.

Just turn away Andy. Walk towards the light...



Sean Atterbury - n/a
23-Jun-06, 08:07 AM
In my case that would be the PC http://hovercraft.org.uk/images/icons/smiley_icons/icon_lol.gif http://hovercraft.org.uk/images/icons/smiley_icons/icon_lol.gif

hovercad - n/a
23-Jun-06, 08:24 AM
Any one seen the chargers for scooters that were on ebay.

They may be still on there.

Basically a hair dryer forcing the air into the carb.

Dont know if they work dont want to find out and doubt if they work.

Could be an alternative (2 hair dryers for a tzr?) Make sure you take a very long extension lead to races.


Sean Atterbury - n/a
23-Jun-06, 09:13 AM
Cummin down the start finish streight and the extention gets caught in the fan, Pullin you all the way back to the start finish line in record time. http://hovercraft.org.uk/images/icons/smiley_icons/icon_lol.gif http://hovercraft.org.uk/images/icons/smiley_icons/icon_lol.gif http://hovercraft.org.uk/images/icons/smiley_icons/icon_lol.gif

tonybroad - n/a
23-Jun-06, 09:22 AM
now then - would a scavenge supercharger sucking the exhaust gasses out be classed as forced induction - the induction isn't being forced as the air is simply being drawn in due to a pressure reduction


mick - n/a
23-Jun-06, 12:06 PM
back to the air induction they way i was thinking was if the engine doesnt have to work as hard to get the air then maybe it would produce more power beacuse the air is being fed to the engine instead of the engine sucking it in thnaks rick

tonybroad - n/a
23-Jun-06, 12:53 PM
Hi Ricky

it not about the engine doing less to get the air in it's about trying to get more air in your engine fullstop. - more air = more oxygen = bigger bang = more power

if you want to do that you are looking at porting and bigger carbs - don't go there(yet)

try the plenum as an experiment by all means - answer your own question( but watch your jetting be careful you don't melt pistons) - i don't honestly think you'll see any significant improvement and you certainly won't be able to race in F3


simonollman - n/a
23-Jun-06, 01:09 PM
you could buy one of these sets of plans?


maybe ?

hovercad - n/a
28-Jun-06, 05:48 PM
Whilst asleep driving on the M25.

Thought Y not mount the engine behind the fan (carbs facing fan)with the fan at the front.(opposite type blades fitted.)

When someone complains u got forced air.Just tell them your actually stuck in reverse and your flying backwards. http://hovercraft.org.uk/images/icons/smiley_icons/icon_confused.gif

Admittedly a bit difficult to see where your going.

Make note.:--

Must get life.


jon_curtis - n/a
28-Jun-06, 06:03 PM
two stroke tune pipes scavenge the cylinder, via the shock wave created by the exhaust gases anyhow. it also couldnt suck in, as paul explained which port being open etc.

J Bucknall - n/a
29-Jun-06, 01:08 PM
the TZR is not a piston ported engine (reed valved) and charging does work in moderation. (have seen it in action) but the gains are not huge. you are better off just porting and setting the thing up correctly.

also to get it to work properly you have to place the whole carb in a presurised box or all you do is blow the petrol out of the carb bowl via the overflows.

also to get any serious power you have to REDUCE the compression ratio or you get knock and detonation due to the peak in cyl pressure being too high.

genral theorey being that by increasing the volume you can get the more stuff in there at the same pressure (with out knock)meaning when burned you have a higher average pressure thoughout the power stroke or a higher break mean effective pressure (bmep). but the peak presure is still the same.

confused? - tough. find a book on thermodynamics.


Paul Fitz - n/a
29-Jun-06, 07:26 PM
The TZR **is** piston ported. It works in the same way as a non-read valve engine with the exception that only the intake tract is not closed by the piston skirt. The main advantage of the read valve is to allow a longer intake period for the crank induction, hence improving the volumetric and 'stuffing' efficiency. The fact still remains that the exhaust port opens first followed by the transfer port(s), and the exhaust port is therefor the last to close. Consequently it is not possible to significantly increase the supplied pressure to the upper cylinder. With very carefull design of the exhuast, tuned to provide high back pressure, it is theoretically possible to gain advantage from low pressure boost, but even the mighty Yamaha gave up on this one.

It is possible to improve the stuffing efficiency slightly which would give more power, but as you rightly say the easiest way to do this is with "porting". I would not however recommend this to anybody unless they have some experience of tuning 2-strokes, or are willing to sacrifice heads and barrels to experimentation. It is very easy to wreck 2-stroke performance by opening ports too far, reducing velocities in the intake tracts and obtaining overall lower volumetric efficiency.

fishy_fish - n/a
30-Jun-06, 05:14 PM
whos the clever one!