Supercharger question

Red_Bullet · Postby **Red_Bullet** » Tue Apr 08, 2014 11:31 pm

Ok, I'm new here. I've been lucky (I think) and have picked up a 1994 Clubman with a Rotrex supercharger on it. The engine was built and supercharger fitted by Bullet supercars at Yatala QLD. I'm guessing the Rotrex is a c30-74 although I've not been able to spot any info on the blower itself, maybe the data plate/part number is underneath the SC.

Anyway, there appears to be a bypass valve, but where it is fitted does not make a lot of sense to me, but then again I have plenty to learn. It appears to be plumbed in on the intake side of the SC and a hose runs away and ventilates to atmosphere. Any idea why anybody would do this? :?:

My understanding of it is that a bypass valve would normally be plumbed in to release pressure from the outlet side of the SC. Other info I have read indicates no bypass is necessary with a SC, more of a turbo thing really.What am I missing here? :?:

cheers
Keith

Hellmun · Postby **Hellmun** » Wed Apr 09, 2014 12:24 am

They're still useful on superchargers as you'll still see spikes when the throttle closes as momentum keeps feeding the motor when it doesn't want more air. I think you'll find that it may look like it's on the intake side but there'll be a passage to the pressure side.

Postby **Okibi** » Wed Apr 09, 2014 12:28 am

Spot on

WASP · Postby **WASP** » Wed Apr 09, 2014 8:28 am

Hi
I had an NA8 fitted with a ROTREX, brilliant unit, by the same people and it didn't have any type of blow off valve. Does yours have the 5th injector. I do have some photos which I can post if you wish.
Steven

Red_Bullet · Postby **Red_Bullet** » Wed Apr 09, 2014 5:57 pm

Hellmun wrote:They're still useful on superchargers as you'll still see spikes when the throttle closes as momentum keeps feeding the motor when it doesn't want more air. I think you'll find that it may look like it's on the intake side but there'll be a passage to the pressure side.

Thanks Hellmun, yes I can see how you would get a pressure spike as the throttle closes and that would be undesirable.
Yes it sure looks like it's on the intake side, trigger tube to manifold, dump tube to atmoshere. It appears to be connected between the air filter on on the CAI and the SC unit. One concern I have is that it could maybe suck unfiltered air into the motor through the dump pipe, although the throttle would be shut anyway so i guess it would be unlikely. There is no filter on the dump pipe. I've taken a few photos if I can figure out how to post them up here I will.

Red_Bullet · Postby **Red_Bullet** » Wed Apr 09, 2014 6:01 pm

WASP wrote:Hi
I had an NA8 fitted with a ROTREX, brilliant unit, by the same people and it didn't have any type of blow off valve. Does yours have the 5th injector. I do have some photos which I can post if you wish.
Steven

Hi Steven, yes I'm pretty happy with it so far, the car has done about 18000km since it was fitted about 5 years ago. I don't think it has a 5th injector. Where is the 5th injector anyway :?:

I've only owned the car for a month or so.
I've tried unsuccessfully to post up a photo, but I won't give up trying.

Red_Bullet · Postby **Red_Bullet** » Wed Apr 09, 2014 6:13 pm

photo

http://s1284.photobucket.com/user/kwsmc ... c.jpg.html

Red_Bullet · Postby **Red_Bullet** » Wed Apr 09, 2014 7:03 pm

5th injector, I see... water injection...no water injection on this one. Fairly moderate setup 90 mm nose pulley, 141 RWkw. Nothing too radical.

Hellmun · Postby **Hellmun** » Wed Apr 09, 2014 8:38 pm

Looking at the cutaway of a rotrex that outer ring of the supercharger will be pressurized, it's where the impeller disperses the air it pulls in so that valve simply allows the pressure to exit to the intake of the impeller. That's all plumbed behind the air filter as well I would've thought? Isn't the air filter at the end of the pipe with the 'Bullet Supercharges' logo?

WASP · Postby **WASP** » Wed Apr 09, 2014 10:19 pm

Not water, fuel, mine had a fifth fuel injector just before the manifold . Nothing wrong with 141 rwkw. I did however fit a Devilsown water injection system

Red_Bullet wrote:5th injector, I see... water injection...no water injection on this one. Fairly moderate setup 90 mm nose pulley, 141 RWkw. Nothing too radical.

WASP · Postby **WASP** » Thu Apr 10, 2014 8:05 am

Hi the fifth injector can be seen mounted just below the blue silicon elbow on the left of photo

WASP · Postby **WASP** » Thu Apr 10, 2014 8:14 am

Sorry my memory failed me, it did have a bov of sorts which can be seen in the photo

WASP wrote:Hi
I had an NA8 fitted with a ROTREX, brilliant unit, by the same people and it didn't have any type of blow off valve. Does yours have the 5th injector. I do have some photos which I can post if you wish.
Steven

Red_Bullet · Postby **Red_Bullet** » Thu Apr 10, 2014 5:33 pm

Nice looking bit of kit, and yours had a typical BOV plumbed from pressure side of the SC back to intake side.

Having had a chat to my son who is doing an engineering degree we reckon mine works like this.

Throttle closes > Bov opens >revs fall causing less boost,> when boost pressure falls below input pressure from falling revs then air flows backwards through the SC impeller and vents to atmosphere. If there was no Bov it would exit backwards through the air filter and CAI.

There may be a possibility of sucking air back in backwards through the Bov as throttle is reopened but this depends on the latency of the Bov and length of dump tube on the Bov...

Hmm what to do?...Maybe I should get it plumbed back into a normal position.

When was your supercharge job done by Bullet Steve? Mine was SC'd in 2007 then engine internals done in 2009. CAI was changed in nov 2013 all by Bullet Cars, maybe I should ring them and ask the question seeing as they obviously reckon it makes sense to them.

WASP · Postby **WASP** » Thu Apr 10, 2014 6:13 pm

In 2008 if my memory is correct

trader · Postby **trader** » Fri Apr 18, 2014 4:06 pm

I have the kraftwerks kit and it has a bov setup similar to Wasps pic. In my view the set up you have red_bullet is entirely superflous if the pipe going down from the BOV is not connected to anything (it should be attached to the charged air pipe).