ProCharged Can-Am - Raising the bar

[ezakimak]

CanAm Dave said:

Scuffers said:

eliot said:

qwick said:

So, a bypass valve goes before and after the supercharger routing air around it rather than through it under low load, when the vacuum increases the bypass shuts and air is drawn into the supercharger and forced into the inlet under pressure, is that right?

Yes - but not on centrifugal chargers like Daves.

qwick said:

If so, is that how yours fits Dave or have you something slightly different which releases pressurised air between the supercharger and the inlet?

His is a std dump valve I believe, to release boost on gearchange or when snapping the throttle shut.

that's how I am understanding it....

I actually don't think this is such a great way to plumb it as unless the dump-valve is HUGE, you will still have some pressure behind the throttle all the time, this has several issues:

1) heat, pushing what will be a huge volume of air though a dump-valve continually is going to heat it and the surrounding parts up
2) the charger is basically running flat out all the time (for a given engine speed), this not only heats up the compressor, but also causes significant parrasitic looses (with no gain)
3) the air filter is going to get clogged up somewhat faster than normal, as the charger will be sucking air though it 100% of the time as fast as it can.

now, the reason people do this is that they argue that it speeds up throttle response, however, whist this is true of turbo's, the same logic does not apply to a crank driven charger, which is why just about every OEM Supercharger setup has the throttle in front of the charger, this means that when throttle is closed, the charger is spinning in a vacuum, thus not consuming much power and heating stuff up (roots/screws/etc tend also to have by-pass valves as well to manage the airflow at small throttle openings).

My first point is that neither of you can read as quicks first point is wrong as vacuum opens the valve not shuts it.
Your first point Scuffers is oh so wrong! The air passing through the bypass valve is a lot cooler than than the surrounding heat in the engine bay so it actually has a cooling effect. My chargecooler is very efficient. The bypass valve has a 38mm valve.
Your second point makes no sense. The supercharger runs at a speed relative to engine speed so it is only running flat out at max engine rpm. The bypass allows me to run better economy off boost.
Your third point is not worth a reply.

OEM supercharger setups I really don't care how they do it! This works for me! There is not one supercharged car produced today that is faster than mine! Even the twin supercharged E85 fuelled CCXR that produces 1004bhp is slower than my car.

I have done some 3,000 miles with my setup and I have no issues with it. It works and next year I will prove it at various events.

Regards Dave

Dave your logic sounds right to me. i cant see any problem with it.
it the bypass valve is positioned so that either side of the valve is around the charger, ie between intake manifold and air filter then it is just another alternate air intak path that may be less restrictive and more efficent at low engine speed/revs/load

ryan

[Scuffers]

CanAm Dave said:

My first point is that neither of you can read as quicks first point is wrong as vacuum opens the valve not shuts it.
Your first point Scuffers is oh so wrong! The air passing through the bypass valve is a lot cooler than than the surrounding heat in the engine bay so it actually has a cooling effect. My chargecooler is very efficient. The bypass valve has a 38mm valve.
Your second point makes no sense. The supercharger runs at a speed relative to engine speed so it is only running flat out at max engine rpm. The bypass allows me to run better economy off boost.
Your third point is not worth a reply.

OEM supercharger setups I really don't care how they do it! This works for me! There is not one supercharged car produced today that is faster than mine! Even the twin supercharged E85 fuelled CCXR that produces 1004bhp is slower than my car.

I have done some 3,000 miles with my setup and I have no issues with it. It works and next year I will prove it at various events.

Regards Dave

here we go again...

Look, I am not going to ardue with you, you cleary have it in your head you are right, but suffice to say, you are not.

running a dump-valve on a SC like you are is a bodge, period. no matter how big it is, you will be casuing an amount of back-pressure - in much the same way the intercooler does or just about anything else in the air-path. 38mm may sound big, but in terms of it's airflow, it's not, they are designed for turbo's where they only have to dump a limited volume of air, not a continus high volume.

if you really are making the power you think, you are looking at some 1,200+ CFM of air
have a think about how that's going to get though a 38mm valve etc...

as for your last comment, I really don't see the relevance it has to the subject appart from some willie waving, if you want to get into that, I am sure I have a car here that can whip your arse round any cct, however, what does that prove re: supercharger plumbing?

I am sure your now going to argue till the cows come home, etc etc, but that is never going to make you right, except in your own little world.

[CanAm Dave]

andygtt said:

CanAm Dave said:

The supercharger runs at a speed relative to engine speed so it is only running flat out at max engine rpm. The bypass allows me to run better economy off boost.

Hi Dave
Not trying to get involved as my undersatnding of Superchargers is limited, just genuinelly trying to understand the logic.
I understand that the supercharger runs at the speed 100% dictated by the crank, but doesn't it draw a different amount of parasetic power from the crank depending upon how much load is on the impeller?
If the impeller is spinning in vacume then surelly it will sap less power than if it was producing boost? or does it draw the same amount of power regardless of the load?
Isnt the buypass you have large enough to remove boost completely, I dont' have any real idea but 38mm seems large enough to me? am I missing something?

Gotta say I really need to have a proper catch up with you and take a real good look at your car as I keep missing you at the shows.... your in Suffolk arn't you?... maybe me and Graham can go for a blast and meet up somewere?

Hi Andy

Yes if the supercharger could run in a vacuum it would draw less load! But I don't think it would make much difference in my case and it would be very hard to plumb in a setup like that in a Can-Am. If it was a GTR I would have more space for the plumbing and it could be worth exploring. My 38mm does get rid of all the boost as I have taken pressure/vacuum measurements above the throttle plates.

I live in Chester but I will be at the factory open day this weekend. Grahams coming!

Regards Dave

[GTWayne]

CanAm Dave said:

My first point is that neither of you can read as quicks first point is wrong as vacuum opens the valve not shuts it.
Your first point Scuffers is oh so wrong! The air passing through the bypass valve is a lot cooler than than the surrounding heat in the engine bay so it actually has a cooling effect. My chargecooler is very efficient. The bypass valve has a 38mm valve.
Your second point makes no sense. The supercharger runs at a speed relative to engine speed so it is only running flat out at max engine rpm. The bypass allows me to run better economy off boost.
Your third point is not worth a reply.

OEM supercharger setups I really don't care how they do it! This works for me! There is not one supercharged car produced today that is faster than mine! Even the twin supercharged E85 fuelled CCXR that produces 1004bhp is slower than my car.

I have done some 3,000 miles with my setup and I have no issues with it. It works and next year I will prove it at various events.

Regards Dave

We know what buttons to push now Dave , see you on Sunday

[qwick]

CanAm Dave said:

Yes if the supercharger could run in a vacuum it would draw less load! But I don't think it would make much difference in my case and it would be very hard to plumb in a setup like that in a Can-Am. If it was a GTR I would have more space for the plumbing and it could be worth exploring. My 38mm does get rid of all the boost as I have taken pressure/vacuum measurements above the throttle plates.

I live in Chester but I will be at the factory open day this weekend. Grahams coming!

Regards Dave

Hi Dave,

Also trying to understand supercharging...

So... at low engine speeds your valve releases the pressure after the supercharger which means that the supercharger runs under less load although it is spinning. When you get on the throttle the valve closes (noise of air going through valve disappears) and engine gets all the boost the Supercharger is already making.

I guess that with a larger pulley like the one you now have even the boost on tickover is increased an this is one of the issues cured by the valve? The advantage you now have is high power from the larger pulley and smoother power delivery and better economy when cruising thanks to the valve....

Damn, I hope I got that right.

[eliot]

Scuffers said:

running a dump-valve on a SC like you are is a bodge, period. no matter how big it is, you will be casuing an amount of back-pressure - in much the same way the intercooler does or just about anything else in the air-path. 38mm may sound big, but in terms of it's airflow, it's not, they are designed for turbo's where they only have to dump a limited volume of air, not a continus high volume.

The dump valve isn't in the air path, so its not causing backpressure.

Why would the DV be flowing continous high volume? - at high rpm (when the s/c is generating high flow) then engine is in low or NO vacuum and so the DV is closed.

The dump valve vents to atmosphere - when the thottle is snapped shut. The air that flows through it, is the air that is excess to the engines requirements (the engine is in high vacuum, which pulls the DV open) - at this point revs are dropping, so output from the s/c is reducing - so the dv helps this transition.

As soon as you get on the throttle, the valve closes and all air from the s/c goes into the engine (because it needs it)

ETA:
Here's a diagram which should help....

Edited by eliot on Thursday 31st July 13:16

[Scuffers]

eliot said:

The dump valve isn't in the air path, so its not causing backpressure.

Why would the DV be flowing continous high volume? - at high rpm (when the s/c is generating high flow) then engine is in low or NO vacuum and so the DV is closed.

The dump valve vents to atmosphere - when the thottle is snapped shut. The air that flows through it, is the air that is excess to the engines requirements (the engine is in high vacuum, which pulls the DV open) - at this point revs are dropping, so output from the s/c is reducing - so the dv helps this transition.

As soon as you get on the throttle, the valve closes and all air from the s/c goes into the engine (because it needs it)

Err… no

When the throttle is closed (or at part throttle enough for the MAP pressure (Vacume) to open the dump valve) said valve is un the air path, as in the air is going from atmosphere >>> filter >>> Supercharger >>> Intercooler >>> dump valve >>> atmosphere , that’s in the air path.

This will be the case 99% of the time, as unless you are driving the car on boost, it will be doing this. (and if the valve is not open it's even worse as the SC will be pushing up against a closed (part or othersie) throttle)

Yes the SC will not be running at peak output, but it’s going to be running at the same RPM relative to the engine at all times, and thus shifting the corresponding amount of air though the induction system and out the dump valve (hence it can be heard).

Now, this is the same as a turbo setup would use, the difference being that when off boost, a turbo will slow down very fast (without the exhaust volume to drive it) and thus the actual airflow though it will be negligible, all it has to do is dump the air in the system and cope with the inertia of the turbo. (if you think about why they are fitted to turbo’s it to prevent the turbo stalling when the throttle is shut, so that on up shifts the turbo does not stop dead and have to start again – as in turbo lag).

So what we have here is a supercharger pumping a (relatively) high volume of air thought the intake system and out of the dump valve all the time the engine is not on boost, whichever way you look at this, it’s a bad idea, only time I can see it being acceptable is in a car that’s very rarely off boost (as in a race car or the like).

Edited by Scuffers on Thursday 31st July 13:28

[eliot]

Are you talking from direct experience or just what you believe?

[Scuffers]

eliot said:

Are you talking from direct experience or just what you believe?

LOL!

I have installed some 100+ SC setup's in the last 2 years, that enough 'direct experience' for you?

either way, that's irrelevant, you seem to be missing the point that so long as the SC is turning, it will be moving air, that air has to either go somewhere or be held back by something, either way, it's causing drag and thus heat etc etc etc...

[qwick]

Ahh, a good debate and I think I am learning, thanks for the pic it helps. I look forward to Dave's response a bit later.

Scuffers, IYO what is the best way to install a dump/bypass valve and why?

[GTWayne]

Is it not possible that we have more than one way to skin a cat here?
On the one hand we have scuffers opinion, and on the other, the rest of the world ( well our little world in any case )

[kylemrushall]

Im sure Dave will respond but he is currently working in Ireland.

[Scuffers]

GTWayne said:

Is it not possible that we have more than one way to skin a cat here?
On the one hand we have scuffers opinion, and on the other, the rest of the world ( well our little world in any case )

yes, of course there is...

however, if you consider that supercharging is hardly a new idea and that it's been used for almost 100 years now, and that almost *every* single OEM SC installation put's the throttle ahead of the SC (I actually can't think of a single one that does not do this).

so, remind me, who are you calling the rest of the world?

[peterpsg]

You guys aren't still smarting about that whole bendy chassis thing are you ? ;-)

[stevieturbo]

Scuffers.


Show me a centrifugal blower setup that runs a "bypass" ???

Tell me why Paxton, Vortech and Procharger all make DV/BOV style dishcarges for their systems, if it it such a wrong way of doing it ?


OE manufacturers with SC installs.....how very few there are, run the TB before the blower to simplify the installation, and add refinement.
Given most, if not all are either Rootes or Screw types......fitting the TB between blower and engine, would be complicated for a variety of reasons.

38mm....is NOT a big discharge. The Mondo for example is closer to 50mm. There will be an element of pressure build up in plumbing, but so what ???
You only need to discharge enough to keep the blower happy.

At part throttle when its opening.....air is simply flowing, so its no big deal.

[eliot]

Scuffers said:

and that almost *every* single OEM SC installation put's the throttle ahead of the SC (I actually can't think of a single one that does not do this).

Yes many positive displacement blowers have the TB before the blower (jag XJR for example) and yes they run a bypass, to circumvent the blower off boost - but I haven't seen bypasses on centrifugal blowers.

[CanAm Dave]

stevieturbo said:

Scuffers.


Show me a centrifugal blower setup that runs a "bypass" ???

Tell me why Paxton, Vortech and Procharger all make DV/BOV style dishcarges for their systems, if it it such a wrong way of doing it ?


OE manufacturers with SC installs.....how very few there are, run the TB before the blower to simplify the installation, and add refinement.
Given most, if not all are either Rootes or Screw types......fitting the TB between blower and engine, would be complicated for a variety of reasons.

38mm....is NOT a big discharge. The Mondo for example is closer to 50mm. There will be an element of pressure build up in plumbing, but so what ???
You only need to discharge enough to keep the blower happy.

At part throttle when its opening.....air is simply flowing, so its no big deal.

And here's a man who knows his stuff!

Thanks for those words Stevie! Saves me the the trouble!

How's the Granada running these days? Have you been out on the drag strip much this year? Just seen some new pics on your site. This I like!(link to pic below) What ECU are you going to use to run this twin injector setup?

http://gallery112848.fotopic.net/p50310880.html


Regards Dave

PS Just seen you on the list for Fighting Torque! Good luck!

Edited by CanAm Dave on Thursday 31st July 19:18

[andygtt]

I'm really struggling to see why the blower would be working hard off throttle if the dump valve is actually relieving the boost, 38mm to me seems to be more than enough to remove almost all the boost not matter how big the charger.

BTW personally doing more than one blower installation every week for 2 years is bloody impressive.

Edited by andygtt on Thursday 31st July 20:07

[stevieturbo]

Hi Dave...

I was at Santa Pod on Friday and TOTB on Sunday at the weekend there...car seems to be going well
Im using the DTA S80Pro to run my car...have been for last year or so. Although my old P8Pro would have run the injectors too.
I just wanted more flow, and resolution than 8 big injectors could do with my setup ( batch fire still, and big high impedance injectors arent very common, although I know of a few types now )
So figured best way for the long term, was to run 2 inj per cylinder


Got my first 9 at the Pod, albeit on ET Streets....so while its good...I'm still not that happy with it. The time was down to traction more than anything.

Ran 181.9mph over a standing kilometre at TOTB though on my normal 888's......so things are looking good for next weekend if all goes well, and its dry.
If its wet, I aint risking it.

Ive a few adjustments to make before next weekend....but I am really looking forward to it !!!
Noise is touch and go at the minute....just hope my new silencers arrive in time to be 100% safe.
It is below 103db at the minute, but just barely.


And just because someone installs hundreds of something....doesnt make them an expert.

I bet KwikFit fitters install thousands of tyres every year.....I still wouldnt go near one, or ask their advice

Edited by stevieturbo on Thursday 31st July 21:39

Edited by stevieturbo on Thursday 31st July 21:51

[chuntington101]

Dave, i dont want to start any more arguements as thsi thread seems to have enough. but have you seen the ford guy running a WASTEGATE after the blower to limit the boost in each gear?? worked really well for him. just wondering if you would have any use for it.

Cheers

Chris.