3.9 Range Rover Supercharger manifold bypass question
Posted: Tue May 24, 2011 6:51 pm
My question concerns the bypass operation.
This is to me quite a brain teaser!
See my previous post on Manifold design.
I have been away from this site for some time, for that I apologise.
Great response last visit, find myself with a mind bending problem, needing your expert help.
Bare with me please in my long winded endeavours’ to explain.
Yes it could be said I am quite mad.
Try please to be constructive.
I have almost completed this project. (Waiting for the Bang)
In brief: 3.9 Rover v8, M90 charger. Sequential everything. Wolf v500. LPG and Petrol.
(I am only prepared to start on petrol initially.)
Have started but few issues to rectify
S ounds sweet in Garage standing still!
Currant Mods: Added separate crank and cam sensors removing VT distributor making room for home made air to air intercooler sandwich plate and outlets.
Zero decked the block . Rover now has squish. (Big risk) Comp probably 11.5 : 1 Possibly More.
Big risk yet again.
Grooved the heads after reading on net
Front mount 450 x 300 x 76 intercooler 75 mm pipes.
By the Way no one would deck the block without the pistons Removed,
So I squared it up and decked by hand. All is good with that.
Suck and see approach is very much out of caricature for me not normally a risk taker, just hoping to do better than the experts that designed the old girl.
When I fired it up, it sucked in the silicone on the temporary intercooler bypass pipe work, still was wafting for delivery of front mount cooler.
Rough tune, few Bangs, Retrieved pipewort from neibours house, running and got it to idle.
Thought all OK
Couldn’t restart
Decided to re think bypass area.
Here is my dilemma: Good luck understanding. On reflection I think I will introduce a drawing or pick.
Bit late hear in Aus.
You are welcome to ponder whilst I sleep.
This issue has been giving me curry and a head ace for some time.
Have a go all as I am very interested in all impute before Decision time. Crossing fingers so to speak.
1. I believe that the function of the bypass in the Eaton M 90 is to negate the pressure coming from the rotors and to redeliver it above them in the vacuum upstream of the throttle body butterfly.
2, I had two totally separate areas to the plenum beneath the charger.
One under the rotors and one under the bypass.
The one under the bypass is the feed, return cooled air that dumps into the top of a cut down SU manifold. It also serves the MAP sensor and air temp.
3. I am aware that at idle and low RPM the Pressurised air passes through the bypass butterfly to the intake of the charger downstream from the mostly closed throttle body butterfly to the vacuum area.
4, In my setup that air also spills into the inlet manifold when bypass open.
DONT KNOW IF THAT IS A PROBLEM.
CHOICES
1, Leave as is all ok (I didn’t observe wether the bypass was actually open when idling, vac line may have been wrong. I did also have an electrical problem hindering starting at the time.
2, Construct a chamber the same cross sectional area as the bypass venturi , install between the rotor plenum and the cooled return air plenum thereby bridging the separate areas and in doing so allowing some idle boost to be available to the intake manifold?
3, Should I also isolate that idle boost air from my return air area and intake manifold throat, thereby having a fully separate dedicated ducted air passage just for the bypass valve to serve beneath the rotors.
Peter From Aus.
This is to me quite a brain teaser!
See my previous post on Manifold design.
I have been away from this site for some time, for that I apologise.
Great response last visit, find myself with a mind bending problem, needing your expert help.
Bare with me please in my long winded endeavours’ to explain.
Yes it could be said I am quite mad.
Try please to be constructive.
I have almost completed this project. (Waiting for the Bang)
In brief: 3.9 Rover v8, M90 charger. Sequential everything. Wolf v500. LPG and Petrol.
(I am only prepared to start on petrol initially.)
Have started but few issues to rectify
S ounds sweet in Garage standing still!
Currant Mods: Added separate crank and cam sensors removing VT distributor making room for home made air to air intercooler sandwich plate and outlets.
Zero decked the block . Rover now has squish. (Big risk) Comp probably 11.5 : 1 Possibly More.
Big risk yet again.
Grooved the heads after reading on net
Front mount 450 x 300 x 76 intercooler 75 mm pipes.
By the Way no one would deck the block without the pistons Removed,
So I squared it up and decked by hand. All is good with that.
Suck and see approach is very much out of caricature for me not normally a risk taker, just hoping to do better than the experts that designed the old girl.
When I fired it up, it sucked in the silicone on the temporary intercooler bypass pipe work, still was wafting for delivery of front mount cooler.
Rough tune, few Bangs, Retrieved pipewort from neibours house, running and got it to idle.
Thought all OK
Couldn’t restart
Decided to re think bypass area.
Here is my dilemma: Good luck understanding. On reflection I think I will introduce a drawing or pick.
Bit late hear in Aus.
You are welcome to ponder whilst I sleep.
This issue has been giving me curry and a head ace for some time.
Have a go all as I am very interested in all impute before Decision time. Crossing fingers so to speak.
1. I believe that the function of the bypass in the Eaton M 90 is to negate the pressure coming from the rotors and to redeliver it above them in the vacuum upstream of the throttle body butterfly.
2, I had two totally separate areas to the plenum beneath the charger.
One under the rotors and one under the bypass.
The one under the bypass is the feed, return cooled air that dumps into the top of a cut down SU manifold. It also serves the MAP sensor and air temp.
3. I am aware that at idle and low RPM the Pressurised air passes through the bypass butterfly to the intake of the charger downstream from the mostly closed throttle body butterfly to the vacuum area.
4, In my setup that air also spills into the inlet manifold when bypass open.
DONT KNOW IF THAT IS A PROBLEM.
CHOICES
1, Leave as is all ok (I didn’t observe wether the bypass was actually open when idling, vac line may have been wrong. I did also have an electrical problem hindering starting at the time.
2, Construct a chamber the same cross sectional area as the bypass venturi , install between the rotor plenum and the cooled return air plenum thereby bridging the separate areas and in doing so allowing some idle boost to be available to the intake manifold?
3, Should I also isolate that idle boost air from my return air area and intake manifold throat, thereby having a fully separate dedicated ducted air passage just for the bypass valve to serve beneath the rotors.
Peter From Aus.
