984 replies to this topic

[Arno]

Option 2 is no longer allowed/supported by Rotrex, they only allow option 1.

 

The vacuum in the charger will pull gear oil from the charger and damage the turbine oil seal.

 

Also the Rotrex oil is very, very expensive and you don't want to be refilling that on a regular basis.. 

 

Option 1 works fine. Just use a big external wastegate on the compressor pipe to either blow off or recirculate under part load. Turbo blowoff valves are often too small for this application of (near) constant air venting.

 

It's a little less efficient than option 2 on part load as the charger is constantly pulling maximum air and you may need to fit some sort of diameter restrictor on the inlet to cap the ultimate power output if the charger can do more than the engine is capable of at full throttle.

 

This is where electronic throttle setups are useful as then you can just let the ECU limit the actual throttle opening to a safe power level at certain loads and not need any restrictors.

 

Bye, Arno.

[aquilaproejct]

Would have thought it would be bad to starve the turbo of air by closing a throttle body, plus disrupted flow on partial throttle on the turbo where you spend most of your driving.. Better to have a wastegate, blow off valve to manage high pressures on #1 post throttle close.

[Aerodynamic]

Again, you are unstoppable Arno  :-)

 

How do you know so much?!

 

Thank you.

 

Option 2 is no longer allowed/supported by Rotrex, they only allow option 1.

 

The vacuum in the charger will pull gear oil from the charger and damage the turbine oil seal.

 

Also the Rotrex oil is very, very expensive and you don't want to be refilling that on a regular basis.. 

 

Option 1 works fine. Just use a big external wastegate on the compressor pipe to either blow off or recirculate under part load. Turbo blowoff valves are often too small for this application of (near) constant air venting.

 

It's a little less efficient than option 2 on part load as the charger is constantly pulling maximum air and you may need to fit some sort of diameter restrictor on the inlet to cap the ultimate power output if the charger can do more than the engine is capable of at full throttle.

 

This is where electronic throttle setups are useful as then you can just let the ECU limit the actual throttle opening to a safe power level at certain loads and not need any restrictors.

 

Bye, Arno.

 

[Aerodynamic]

Arno, do you know any BOV good for this application or little more, that is not to pricy?  re-circulating.

 

I thought if you stay on middle gas through a corner, cant it be that the valve open and closes, open close, open close and so on.

 

Br, Per

[alexb]

I actually run a Rotrex (C38) and use a Tial QRJ recirculating BOV. I think it's 38 mm. Before that I used two standard 20 mm VAG BOV's, which you can have for next to nothing second hand. That worked well too, the only issue was the piping. And yes, you should recirculate. Blowing off to free air is fun for a while, but it's like you have a giant hairdryer in the back of the car, as the Rotrex generates a lot of air only depending on RPM. The BOV is not flipflopping, but beware that you should take the weakest valve spring. Tial offers a special spring for blower applications.

[Bloke]

Don't run a restrictor on the charger, run an external wastegate on the boost side.

[Arno]

Forge FMCL007P worked well, but now discontinued. Replaced by FMDV008

If you don't recirculate it's also an option to feed the outlet of the valve with a hose down and towards the exhaust silencer area of the car to get rid of the 'hairdryer' noise.

Not recirulating can have the small advantage that the rotrex keeps pumping fresh, cool, air into the system that's not heated much as there's not much pressure generated under these conditions. When the valve is fitted after an intercooler so the rotrex constantly blows through the IC it can help recover quicker when it heat soaks on full throttle. Good for road cars that see only short bursts of power.

 

Of course that's all moot under sustained high load and max boost on track or an autobahn as then the heat-shedding capacity of an intercooler in steady-state is the key.   

For bigger pressure-limiting valve sizes you have to go to an external wastegate (most BOV's end at around 40mm) and use that for the air diverting. These go up to 60+mm or so. Needs a more 'complex' wastegate type though that can be driven on both sides of the diaphragm and not a 'stupid' single drive (but most are these days anyway as you need that on a turbo with good electronic boost control too..).

Like alex mentioned, weak spring(s) are your friend as in this application you are using either a BOV or wastegate valve different from their original/intended use. Here it's more a regressive bleed-off setup that squeezes the bleed off shut as the manifold vacuum gets less and turns into positive pressure.
 

Bye, Arno.

[Aerodynamic]

I understood it as Rotrex previously recommended to place the TB before the supercharger but they changed it later on because of the seals. 

This car is built as a track car, so not much road driving.

 

,Per

 

Edited by Aerodynamic, 31 December 2020 - 12:22 PM.

[Aerodynamic]

I had a chat with Rotrex, didnt get to much details, but they recommended to have the supercharger before the TB and said I could get idleing problems

with the other installation.

 

So I guess I´m going with this option

[Aerodynamic]

Now I have worked on with both car and garage.
Since we moved, I have got a smaller garage than before, so I must try to be creative
and get rid of some things.

So got up some hooks for the clam and a kind of shelf for the hard top where I hope it does the least damage to be able to continue to decorate the garage.

 

Then what about the exhaust system together with the supercharger
Today with about 220hp it sounds 92db on Kinnekulle ring (a swedish nearby racetrack)
With a supercharger and about 350hp.
What can you expect?
Will the sound level be raised much?

In that case, consider cutting off the megaphone and installing another muffler.
Or maybe a bend on the end pipe directed into the ground is enough?

 

Br, Per

Edited by Aerodynamic, 05 January 2021 - 09:22 PM.

[Aerodynamic]

I have a anti problem.

I have no issues at all with wheel spin, but now when I plan to supercharge

I want to know if I could have a LSD. 

I know it cant be a plate type LSD

 

But how do I check if  I have a Quaife type LSD?  The gearbox is bought second hand some years ago.

 

Br, Per

[FLD]

In old skool cars to check for an LSD you'd jack up both sides and turn one rear wheel.  If the wheel on the other side turns the same way it has an LSD, if it turns the opposite way its an open diff.  The diffs under test were plate diffs and they were solid axles so I'm not sure if this is still applicable but worth a go.

[Arno]

Also, normally on an open/normal diff when you take out the driveshafts you see a shaft of the smaller gears inside the diff.

 

 

 

Usually a torsen style LSD like a Quaife will be totally open when you look through and there will be no shaft:

 

 

There may be a plate or some smaller diameter section, but no shaft.

 

Bye, Arno.

 

Bye, Arno.

[Acidpopstar]

Now I have worked on with both car and garage.

Since we moved, I have got a smaller garage than before, so I must try to be creative

and get rid of some things.
So got up some hooks for the clam and a kind of shelf for the hard top where I hope it does the least damage to be able to continue to decorate the garage.


Then what about the exhaust system together with the supercharger

Today with about 220hp it sounds 92db on Kinnekulle ring (a swedish nearby racetrack)

With a supercharger and about 350hp.

What can you expect?

Will the sound level be raised much?
In that case, consider cutting off the megaphone and installing another muffler.

Or maybe a bend on the end pipe directed into the ground is enough?

Br, Per

With the M62 on my car the noise mainly came from intake. Swapping the massive foam cone for a drilled Saab air box greatly reduced the noise.


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[speedster norway]

I have Quaife and both wheels turn the same way, but I did not check that they went the opposite way before I mounted Quaife 

[Aerodynamic]

Thank you Arno

 

Also, normally on an open/normal diff when you take out the driveshafts you see a shaft of the smaller gears inside the diff.

 

 

 

Usually a torsen style LSD like a Quaife will be totally open when you look through and there will be no shaft:

 

 

There may be a plate or some smaller diameter section, but no shaft.

 

Bye, Arno.

 

Bye, Arno.

 

[Aerodynamic]

Ok, I will need to look at reduce intake noise. it seems. 

 

What about if I place the Rotrex above the intake manifold, will the intake manifold be able to "carry" the weight of the Rotrex?

 

Br, Per

[Aerodynamic]

Another thing I´ve been thinking of for years and am now seriously considering  to buy

is a SQS racing sequential gear shifter.

Since I´m really bad  at gear shifting and trying  to avoid it as far as possible when beeing out on track.

I´ve also miss shifted from 4th to 3rd gear when I was planing to shift to 5th gear a few times

I thought this could be my saviour

 

 

what do you think?

 

Br, Per

[NOSBandit]

The SQS shifter works really well, I've got one fitted

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[Aerodynamic]

Nice to hear. In which car and which engine?

 

 

The SQS shifter works really well, I've got one fitted

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