pressurised Airbox PWK35 combo?

scooble · Post by **scooble** » Fri Aug 27, 2010 9:39 am

I'm just finishing off my fully enclosed airbox which I will be using with my PWK35's.

As a starting point, can anyone recommend Main Jet, and Needle jets for this kind of setup?

TwoStroke Institute · Post by **TwoStroke Institute** » Sat Aug 28, 2010 3:36 pm

First is the airbox fully pressurised with the only atmospheric opening in the nose of the fairing or just has the carbs inside a airbox with no duct to the front of the fairing?
If the former, what you MUST do is connect the fuel tank breather to the air box. This will pressurise the tank and force fuel in at a a proportional rate as what it did without the pressure. h***a system has a soleniod when the brakes are applied the feed to the tank is shut.
With the latter there will be no increase in airbox pressure. So either way roughly the same jetting.
There is a schemetic of the HRC system on the WWW 'somewhere' post some pics finding when you trial it please.

scooble · Post by **scooble** » Sun Aug 29, 2010 3:05 pm

I've nearly finished the airbox, just need to cut a hole in the top to get access the carbs and create a duct and piping that will be fed by two forard facing air ducts just below the hand blisters on the fairing.
I will ensure that the tank breather is also fed into the airbox too. It'll be a week or two before the whole lot will be fully assembled and running. I know theres going to be some messing about with jetting, so was wondering what would be a safe size to start with and then order a range of jets to start experimenting with.

Charles · Post by **Charles** » Sun Aug 29, 2010 3:07 pm

just ask The Elf. he's using the same setup IIRC

Charles

KR-1R · Post by **KR-1R** » Mon Aug 30, 2010 9:50 am

.
.
I think full tank vs half tank of fuel probably has more effect than < +0.1psi @100kph
...has more to do with refilling the airbox than positive boost?
... theres been a few magazine articles on the benefits - cant recall the results - the carb float bowls/carb overflows should be exposed to the increase rather than outside the airbox?
... others have done their airboxes - Ive yet to get further than verify (but fully enclosed is on the agenda)

... I think some others are on 150-155 mains - so somewhere 150-160

ps how much does an R6/R1 exup servo weight? (plastic) vs KIPS and is its the wiring/control similar?

TwoStroke Institute · Mon Aug 30, 2010 11:17 am

Geez when someone inevidably asks "Hey mate what's ice cream container for?" you reply?

If the carbs are in the airbox no need to do anything with breathers, if carbs are outside a pressurised airbox the vents tubes must go to the floatbowl.

KR-1R · Post by **KR-1R** » Mon Aug 30, 2010 9:04 pm

TwoStroke Institute wrote:Geez when someone inevidably asks "Hey mate what's ice cream container for?" you reply?

.
.
and coming from the land of Yahoo Serious?

ok Reckless Kelly - I know what other use dustbins have...

:

Australia: 0 .............. New Zealand: 1

TwoStroke Institute · Tue Aug 31, 2010 11:25 am

The Reckless Kelly bike was one of our better efforts, but we don't build them we just ride them.

Luders · Post by **Luders** » Wed Sep 08, 2010 10:53 pm

How are you getting on with this?

I know MJ has 35's on his race bike with an air feed running from the front, so it might be worth asking him.

When I get chance, I'll be going down the scientific route with setting my mixture up, but this will be on standard 28's so my data won't help you much, but you're welcome to it.

KwakOn · Post by **KwakOn** » Sat Sep 11, 2010 8:08 pm

I'm running pressurised airbox, (28mm carbs not enclosed) and use 150 main jets which are fine on track, probly bit too rich really (below 90mph). I have read that 35's use 150's as well so as mentioned at least 150 to be safe.

std tank is not easy to send pressure to, if you did think it was worthwhile. I have put two gravity fed fuel taps anyway.

KR-1R is that the reading you got " < +0.1psi @100kph " ?
what about @ 100mph?

"just ask The Elf." noooo he runs Avgas and his jetting advice cost me a barrel and piston when I first ran pressurised airbox.

mj43 · Post by **mj43** » Sun Sep 12, 2010 10:37 am

Luders wrote:How are you getting on with this?

I know MJ has 35's on his race bike with an air feed running from the front, so it might be worth asking him.

When I get chance, I'll be going down the scientific route with setting my mixture up, but this will be on standard 28's so my data won't help you much, but you're welcome to it.

I run a cold air feed into the airbox but the normal intakes are open, i.e. it is not a sealed airbox. Even so at speed it does pressurise relative to the air around the carbs and until I fed all the carb breathers into the airbox it would stutter on 4 to 5 and 5 to 6 gear changes. Fuel is gravity fed and I don't pressurise the tank. With 35mm carbs main jets are in the 152 to 158 range. I did change the needle think it is a DEN or DEL will need to check it out.