Summary

Superchargers have long been a popular choice for boosting the performance of our engines, however when it comes to selecting a supercharger there are actually a wide range of options. In this webinar we’ll discuss the various supercharger styles and explain the pros and cons of each. We’ll also discuss the mounting considerations you need to keep in mind when fitting a supercharger.

 

00:00 - It's Andre from the High Performance Academy, welcome along to another one of our webinars.
00:04 Now today we're going to be talking about the topic of superchargers.
00:07 And this is a topic that I know a few people are confused about, particularly when it comes to choosing a supercharger for a particular application.
00:15 Now on face value you may think that a supercharger is a supercharger but there are three broad families of supercharger that we do need to understand.
00:24 And their performance and their characteristics as well as everything that goes into mounting them are quite dramatically different.
00:31 So we're going to be finding out today about the roots style supercharger, positive displacement supercharger.
00:38 We're going to also be talking about the twin screw style positive displacement supercharger and then we're going to be talking about the centrifugal supercharger.
00:46 Now I guess it's probably actually best to start about talking about the difference between superchargers and turbochargers.
00:53 And realistically the main difference here is that the turbocharger, which I've got a little exhibit A sitting here up on the bench.
01:02 These are a exhaust gas driven supercharger, so they're an exhaust gas driven compressor if you like.
01:11 The advantage with the turbocharger is essentially it's harnessing waste exhaust gas energy from the engine.
01:17 Now that still doesn't come as any free lunches there, there is some parasitic losses as a result of gathering the exhaust gas energy to drive the turbine wheel.
01:27 In particular it creates exhaust gas back pressure so that has an effect on the efficiency, volumetric efficiency of the engine and the engine operation in general.
01:35 But basically it's harnessing that exhaust gas energy, it's spinning the turbine wheel which is attached to a common shaft with a compressor wheel.
01:44 Now the advantage of the turbocharger and why we've seen them become really really popular in high performance applications, is that the turbocharger can be made to be very very efficient.
01:58 And what I'm talking about with efficiency there is basically when we add boost pressure to our engines, we by definition must end up heating up the air that's coming out of the compressor.
02:11 Of course hot air is the enemy to engine performance.
02:15 So the hotter the air is, the less dense it is, the less oxygen it contains and the less power we can make.
02:21 So it's all very well and good jamming more air into the engine and increasing our boost pressure, but if we're creating a very very hot, low density charge air that's going into the engine, the result of this is that he engine isn't actually going to make as much power as it can.
02:36 So in terms of this, what we want to do is make sure that the compressor is working as efficiently as it possibly can, the more efficient it is for a given boost pressure at the outlet, the less heat that we're putting into the air.
02:49 And I'm just talking about this because efficiency is a concept that's important to understand and that plays into our selection with superchargers.
02:58 So unlike our turbocharger here, the supercharger, regardless which option you're going for, is going to be driven directly from the crankshaft of the engine.
03:08 And that creates some advantages and it creates some disadvantages.
03:14 One of the problems with our little friend the turbocharger here is that they don't do a great job of producing good boost at low RPM, and also there's some inherent lag with the operation of the turbocharger.
03:25 Now what I mean by this, and these two terms are often confused so I want to just dive into this for a second.
03:31 What I mean by this is that if we put our engine on a dyno and we start it at 1000 RPM and we go to wide open throttle, chances are at 1000 RPM we're going to see little, if any positive boost pressure in the inlet manifold.
03:46 At such low RPM, there physically just isn't enough exhaust gas energy to spin up the turbine wheel and produce positive boost pressure in our inlet manifold.
03:54 So as we increase our RPM, we end up supplying more exhaust gas energy to the turbine wheel, this creates more compressor outlet flow and in turn we start to see our boost climb.
04:07 So of course, depending on our engine's capacity as well as our turbo sizing, it would be common with a street size turbo to not see our full boost pressure until perhaps 2500, to maybe 3500 RPM.
04:20 Somewhere around about that point.
04:23 So this terminology here is called boost threshold.
04:26 And this is just down to the exhaust gas energy being available to drive the turbocharger.
04:32 The other aspect, and these two as I've mentioned, are often confused, is turbo lag.
04:36 Now turbo lag is due to the inertia of the compressor and turbine wheels and this happens when we're up at higher RPM, so we're already operating at or above the RPM where we can actually achieve full boost pressure.
04:50 So in our example that I've just given, let's say we're now operating at 4000 RPM, we're at full throttle and let's say we've got 15 psi of boost pressure available in the inlet manifold.
05:00 Now what we're going to do is back completely off the throttle.
05:02 Now when we do this, our blow off valve will probably open, that vents out our boost pressure that's built up between the turbocharger and our throttle body, and because we've backed off the throttle, we've also reduced the available exhaust gas flow to the turbine wheel.
05:17 As a result of this, what we see is the turbine wheel will slow down.
05:21 When we jump back on the throttle now, we're going to find that there is a momentary delay as the turbo comes back up to full speed and gets us back to our target of 15 psi.
05:31 We've seen massive improvements in the lag factor over the last decade that I've been involved with turbocharged engines and today some well sized turbochargers, this is almost impossible to notice but it is there, there's always going to be some small delay.
05:49 So that's turbochargers, obviously our topic today is superchargers but important to get that differentiation in there.
05:54 And the advantage that we can see with a supercharger regardless which style we go for is that because it is belt driven, or maybe sometimes chain driven, directly off the crankshaft it is always maintaining a fixed speed.
06:08 So when we jump off the throttle and get back onto it, there is no lag, there is no delay, we should have instant response.
06:15 So that's our key difference there but as I've said, when we're talking about the family of superchargers in general, there are three different varieties and they are quite different.
06:25 So it's important to understand what those are and what those differences will equate to in terms of the way our engine operates.
06:34 So let's jump across to my laptop screen for a moment.
06:37 We're going to start by talking about probably the most well known traditional positive displacement style supercharger which is our roots supercharger or roots blower and that's what we've got sitting on our screen here.
06:51 So this particular blower is set up on a V8 inlet manifold and they do actually lend themselves quite nicely to the V8 style engine because they're really easy to fit in the valley between the two banks of cylinders.
07:06 So basically we've got an inlet at the top and of course the air is compressed and comes out the bottom or actually it's forced out the bottom, it's not really compressed in so much as the way the supercharger operates, we'll talk about that as we go through it.
07:22 So the roots supercharger involves two counter rotating lobes that will rotate together and basically it draws air in through the top of the supercharger, passes it around the outside of the supercharger and then pumps it down into the engine.
07:38 The point here is that this is referred to as a positive displacement style supercharger.
07:46 Our twin screw which we'll talk about next is exactly the same.
07:50 What this means is that for a given rotation of the supercharger it's going to displace a fixed volume of air through the supercharger.
07:58 And the theory here around creating positive boost pressure is what we need to do with our supercharger is force or displace more air than the engine is consuming naturally.
08:13 If we can do that, we're going to end up with positive pressure being created inside of the inlet manifold.
08:20 We'll just have a quick look here.
08:23 Alright so if we jump across to my laptop screen, again, this is sort of an idea of the inner workings and I've shamelessly found these on the internet so I don't take any credit for these drawings at all.
08:35 Just so you're aware.
08:38 So we've got our two counter rotating lobes here inside of the supercharger, and essentially our air is going in through the top and then is being forced out the bottom into the engine so we can see the inlet cycle here, our air goes into the supercharger, it is trapped and runs around the outside of the supercharger and then it's discharged out the bottom.
09:01 So because it is positive displacement as well, it does rely on quite tight tolerances between the lobes where they mesh together as well as the outside casing of the supercharger.
09:11 If we've got any gaps there, this is going to reduce the efficiency of the supercharger and it's going to make it possible for leaks to occur.
09:21 Alright so with our roots style supercharger, again probably one of the earliest styles of superchargers, one of the advantages is that because it's positive displacement, we can provide pretty great boost response at low RPM.
09:36 It's great for producing positive boost, basically straight off idle as soon as we go to full throttle.
09:43 What we also see is that the air flow out of the supercharger, obviously because it's crankshaft driven, is directly linked to our engine RPM.
09:51 So we're sort of matching within reason because of the changing volumetric efficiency of our engine as we go through the rev range and we kind of try to match with the positive displacement supercharger, the air flow out of the supercharger, with the air flow into the engine.
10:07 So what we see is a relatively flat boost curve as we go through the RPM range.
10:12 Problems with the roots style supercharger though is that they don't give great efficiency, particularly if we want to make a reasonable amount of boost pressure.
10:23 So again I've just found a typical, don't have a lot of numbers on this, but a typical kind of efficiency graph for a roots style supercharger so we'll have a quick look at this.
10:37 And what we can see here is we've got our pressure ratio on the vertical axis and we've got our speed or RPM on the horizontal axis.
10:45 So what we can actually see is that at very low speed and low positive boost pressure, we've actually got quite good efficiency.
10:53 Supposedly up around 80% to 90%.
10:57 The problem is that as we've wanted to make more power out of our engines and as we've wanted to push superchargers harder and harder, we are probably, oops that's a pretty terrible arrow, we're going to be probably wanting to operate more up in the higher right side of this efficiency map.
11:15 As you can see, the efficiency's getting pretty shocking down around 50% to 55%.
11:20 Now compare that again to our turbocharger that we talked about briefly, a well sized turbocharger, it's not uncommon to have efficiency in the 75% to 80% range.
11:30 Again, just to reiterate, this refers to pound of boost, per pound of boost, how much additional heat we are adding in.
11:38 As our efficiency drops we're adding more heat and of course we know that heat is the enemy of power.
11:44 So they're really not that great if we want to run very high boost pressures.
11:48 We're going to be able to run high positive boost pressures but we're going to have the downside of that being that they'll do it very inefficiently, creating a huge amount of heat.
12:01 The other aspect with the roots style supercharger is that they take quite a lot of mechanical effort to drive them and, I mean depending again on the supercharger you're running and the amount of, or how hard we're running it, how much air flow you want out of that supercharger, it's not uncommon for a roots style supercharger to absorb 50 to 60 horsepower from the engine or more.
12:26 So yes it's making you more power but it's actually absorbing quite a lot of power in order to do that.
12:31 They are also relatively high maintenance, as I've mentioned they do rely on really tight fitment between the lobes of the supercharger as well as the housing of the supercharger.
12:42 Once we start getting wear in any of those components, it's essentially creating an internal leak path that's going to reduce the boost pressure at the supercharger outlet and as a result, they are quite high in maintenance if you want them running at their best.
12:56 Alright so that's our first one and realistically these days unless you are wanting to go for a certain look in your engine bay for an old school style hot rod, there's probably not a lot of great reasons why you would reach for the roots style blower.
13:12 Coming from the roots style blower, the next one we're going to be talking about is our twin screw supercharger.
13:18 So similar in essence to the roots style blower in that we've got two intermashing lobes and at a glance if you didn't really know what you're looking at, they do look relatively similar to the roots style blower.
13:32 They're still going to be in a V8 configuration mounted in the valley between the two banks of cylinders.
13:38 They're still going to be driven by a belt generally at the front of the supercharger as well.
13:43 So similar in that essence but very different to how they actually operate.
13:46 So let me just head across to our laptop screen again and we've got another image here.
13:54 So this time we can see the design of the lobes is quite different, we've kind of got some intermeshing worm drive style lobes and the idea between, with the twin screw style supercharger is you'll remember that with our roots style blower, the air actually comes in the middle and then it passes around the outside of the lobes and then it gets forced down into the engine.
14:17 This is quite different in that the air actually ends up being trapped between the lobes and due to the design of the lobes, as the lobes come together, this actually does the compression of our air, so it's compressing the air between the two lobes.
14:33 There's some upside and there's some downside with this.
14:36 First of all, these are much more efficient than a roots style supercharger and as well as this, they don't take quite as much horsepower from the engine in order to drive them.
14:49 So basically pound for pound of boost pressure, you're going to end up with cooler charge air, so that's going to make more power, and as an added bonus, you're not actually going to be sapping as much power from the engine in order to make that boost pressure.
15:02 So all positive things there.
15:04 Downside though is that as you can probably already see by looking at the design of those lobes, they are a lot more intricate than a roots style blower so generally you're going to find that the twin screw style superchargers are a little bit more expensive to manufacture and of course that gets passed onto us as the consumer.
15:22 They do still rely on tight meshing between those twin screw lobes and again they will be affected over time by wear, that again drops their efficiency.
15:35 In terms of the way the twin screw supercharger produces boost, very very similar to the roots style blower in that they're great at producing good boost pressure at low RPM and you're also still going to get that relatively flat boost curve throughout the rev range.
15:52 So very similar in that respect.
15:54 Again why we see them very commonly used on a V8 configuration engine, great for low RPM torque.
16:00 These will work better at high boost levels than a roots style blower but probably not quite as efficient at very high boost pressures as a turbocharger, which we've already looked at.
16:13 And definitely even compared to a turbocharger compressor, the twin screw still can't see the sort of efficiency levels that we would see on a turbo style compressor as well.
16:29 Alright, the last option that we're going to talk about today is the centrifugal supercharger and basically the centrifugal supercharger is a engine driven turbocharger.
16:42 That's probably the easiest way of considering it.
16:45 So we've already talked about our turbocharger and how we can get a compressor that's sized pretty well for the application we're going for and is able to produce boost pressure really efficiently, somewhere in the 70% to 80% efficiency range, which is something that's definitely unheard of with a roots style blower for example.
17:05 So we'll jump across to my laptop screen and have a quick look at what we see with a typical centrifugal supercharger.
17:13 So it's a little hard to see from this angle but basically the section that I've just highlighted there is really no different at all to our turbocharger.
17:21 We've got a centrifugal compressor wheel and we've got our compressor housing so basically at this point, simply no different to a turbocharger.
17:31 The problem is that in order to produce meaningful boost pressure with a centrifugal compressor wheel, we need to spin it at really really high RPM and when we've only got our engine crankshaft speed to work with, that can be pretty tricky, wouldn't be uncommon to see these centrifugal compressor wheels operating in the region of 80000 to 100000 plus RPM quite easily.
17:57 And it's pretty tricky to get there if you've got a crankshaft speed that's only getting up to 7000 or 8000 RPM.
18:03 So the key point here is that there is a gearbox attached to the centrifugal supercharger and that's designed to gear up the rotation speed between what we get in at the pulley, so this little part here, this is driven by a belt from our crankshaft, and then the rotation speed is stepped up so that we actually get up to an RPM where our compressor can actually pump air and create positive boost pressure.
18:33 So these are available again from a range of manufacturers and they are able to match, unsurprisingly our turbochargers in terms of their efficiency.
18:44 Reason being that they are essentially just using a turbo compressor wheel as well.
18:49 So on that note they're basically same for same there.
18:52 There are some problems though with a centrifugal supercharger.
18:56 The main one is that because it is belt driven, we're going to find that our boost pressure is very very tightly linked to our engine RPM.
19:08 What I mean by this is at low engine RPM we essentially don't have enough compressor speed to really produce much, if any positive boost pressure.
19:19 So what we'll find is that our boost pressure at low RPM is going to be essentially zero.
19:23 As we move through our RPM range we're going to find that our boost pressure continues to climb linearly all the way to our engine rev limit.
19:32 So to just sort of show you how that all works, let's just jump across to my laptop screen again and this is a comparison of the sort of boost response we can expect.
19:41 So on the vertical axis here we've got our boost pressure.
19:45 The red line that we can see in here, this is our boost pressure curve that we're likely to see with a roots or twin screw style positive displacement supercharger.
19:57 So as I mentioned, we've basically got really good boost response as soon as we open the throttle straight off idle.
20:03 And we're going to find that that boost curve is probably not quite as flat as what we've got here but reasonably flat right through our rev range.
20:10 Just for a comparison, we've got this purple line shown in here which is what we'd typically see with an exhaust driven turbocharger.
20:18 So we've got that lag where in this case we haven't reached 10 psi of boost until about 4200 RPM.
20:25 And then finally we've got this light blue line which shows us what we're likely to see with a centrifugal supercharger.
20:32 So the problem is that with the centrifugal supercharger, we're going to be giving away a lot of potential performance at low RPM because at low RPM we've got little to no real boost pressure, what this results in is that we're going to end up with very little increase in engine power and torque at low RPM.
20:54 Of course as we move further through the rev range and we get to a point where we're actually starting to get enough compressor speed to get positive boost pressue or a decent amount of positive boost pressure, and we start seeing the power and torque increase quite dramatically.
21:08 And because we've got this boost curve, which continues to increase right through to the rev range, what we end up with is a situation where this does kind of artificially skew our torque curve and our power curve.
21:22 What we find is that if we run a fixed boost pressure, maybe a consistent boost pressure right through our rev range, we're going to end up with a fairly typical power curve where our torque in particular starts out low, increases, peaks maybe around 3000 to 4000 RPM and then starts to drop away.
21:39 With the centrifugal supercharger, that is all skewed towards the higher RPM range and we tend to see our torque continue to climb and it will hold a lot more torque through higher RPM.
21:52 So we're going to see, if we ran the same engine with these three different superchargers, we're going to see that the roots and twin screw style are going to produce good low RPM torque and power.
22:05 For the same amount of boost pressure we're going to see more power from the twin screw because it's more efficient and it saps less power.
22:12 On the other hand, with the centrifugal we're going to see that we're well behind the eight ball in terms of power and torque at low RPM.
22:19 But by the time we get about halfway through our rev range, potentially, depending on the gearing and the boost we're actually running, we're going to see the centrifugal supercharger match the power from our two positive displacement superchargers.
22:32 Then the further we rev it, the more power we're going to end up gaining.
22:36 And for a given boost pressure we're going to see the most performance out of the centrifugal supercharger.
22:44 Alright so there's a few considerations here which we're going to move into and talk about but before I mention that, I'll just say that we are going to have some questions and answers really shortly so if you've got any questions that have cropped up during this webinar, please ask those in the chat and we'll deal with those shortly.
23:00 The first question would be, given the amount of power and torque that we are giving away at low RPM with a centrifugal supercharger, why would anyone in their right mind choose one of these over a positive displacement style supercharger? Fair question, the advantage of the centrifugal as we've probably already cottoned onto here is at higher RPM.
23:24 And provided that the boost pressure is set correctly or the ratio between the pulley sizes is set correctly, we will find that the centrifugal supercharger does provide really really good power, better than the other two, from around about halfway through our rev range all the way through to our red line.
23:43 So this does suit quite well a competition car, particularly circuit racing for example where typically the higher end of the rev range is going to be used.
23:54 As we already know, we're going to end up with more power for the same amount of boost, we're going to be putting less heat into our air and actually something I haven't mentioned as well, the centrifugal supercharger will draw the least power of all three from the engine so if you're going to be operating in that higher RPM range, these are all positives.
24:12 The centrifugal supercharger starts to make a bit of sense.
24:15 The other aspect that is a little bit more tricky to understand but this is something that we've seen repeatedly in some of the front wheel drive time attack cars that run at World Time Attack, they will choose quite often, the centrifugal supercharger over a more traditional turbocharger and the reason for this is that the torque and power development of the engine is much more controllable often with a centrifugal supercharger.
24:42 What I mean by this is obviously again our boost pressure and hence our power and torque is linked directly to our engine RPM.
24:52 What this means is that if we are coming out of a low speed corner where particularly a front wheel drive circuit car is going to be heavily traction limited, with a turbocharger as soon as you get back onto the power, even from down at 3000, 3500, 4000 RPM, you're going to find that very quickly that turbocharger reaches full boost and that can easily overwhelm the traction available with a front wheel drive car.
25:18 However with a centrifugal supercharger at lower RPM you've got less boost pressure, you know for a given RPM what the boost pressure and hence engine torque is going to be, it's not going to change at the same RPM like it can with a turbocharger.
25:32 So this can make the centrifugal supercharger make the engine a little bit more predictable to drive and it can help with low traction situations.
25:42 Why we see predominantly the roots style or more likely the twin screw style supercharger being chosen for a V8 application, comes down to the usable powerband from a V8 engine.
25:57 Generally with the V8s, we tend to favour low RPM torque anyway.
26:01 Obviously both positive displacements are ideal here.
26:05 And the other advantage there which we need to consider is the mounting complexities.
26:12 So with a twin screw or a roots style supercharger, as we've already mentioned a couple of times, really really suit themselves well to a V8 configuration because it's easy to make an adaption between that supercharger and an inlet manifold, it's gonna sit there nicely in the V, in the valley between the two banks of cylinders so that makes it really nice and easy.
26:33 On the other hand, fitting a centrifugal supercharger, actually can be quite tricky and it needs to be done really really accurately because if there's alignment issues between the pulley drive on the crankshaft and the pulley drive on the centrifugal supercharger, you're going to have all sorts of problems with valve reliability which is exactly what we don't want.
26:53 So particularly with a centrifugal supercharger, that alignment is key and it needs to be really well supported so this requires quite an intricate bracket to be made up to mount the supercharger to the engine.
27:05 Of course in some applications, this also makes it really tricky because we need to be in line with the crankshaft or wherever our pulley drive is for the supercharger, and this could be limited on exactly how much room you have available.
27:19 The other aspect we do need to talk about here is the intercooling aspect.
27:25 So as we've talked about, when we create boost pressure, we create heat.
27:30 Regardless how efficient our compressor is, we're still going to be creating heat and we do need to manage this.
27:37 So this is where I think personally the positive dosplacement superchargers do make life a little bit more tricky, I think it's harder to intercool them as effectively as we can with a centrifugal supercharger.
27:51 And let me just show you, OK let's head across to my laptop screen here.
27:55 So this is the traditional approach we see here, this is a Whipple twin screw supercharger for a V8 engine.
28:02 And what we can see is that it's mounted on top of a specific inlet manifold that actually incorporates a water to air intercooler core.
28:12 Now nothing per se wrong with water to air intercoolers, they do add a little bit of complexity and in general compared to a front mounted air to air intercooler, we're generally going to struggle, particularly with a manifold mounted intercooler like this, we're going to struggle to get enough area to probably produce the same outlet charge temperature as what we could with a front mounted intercooler.
28:39 Obviously we then need to plumb a cooler into the front of the car to get heat back out of our water as well.
28:45 So while there have been some pretty big advances in water to air intercooler technology, there's certainly a big step forward over no intercooler at all.
28:55 It is a little tricky with some applications just because of the room available to fit a suitably sized core and get rid of enough heat so basically we have, compared to a well sized air to air intercooler fitted on the front of the car, we're almost certainly going to end up with a higher charge temperature and again, higher charge temperature means less air density and less power for our engine.
29:19 The centrifugal style supercharger, we can address this by using a conventional air to air intercooler core mounted in the front of the car.
29:26 Basically we're going to plumb everything up just like we would if it was a turbocharger.
29:32 Advantages there in terms of our ability to get more heat out of the air, disadvantages in terms of the complexity, there's a lot more going on, particularly with modern cars, can be pretty difficult to find room to fit that intercooler core in the front of the car and also to plumb the intercooler plumbing both from the compressor to the intercooler and then from the intercooler back up to our inlet manifold.
29:55 So there's no clear winner here because while yes the centrifugal supercharger can get more heat out of the air, and make more power, the problem with this is that we're going to end up with a much more complex installation.
30:10 So this is why, particularly for customers who are looking for a mild to moderate increase in engine performance, they don't really want to have to cut the car up and go to extreme lengths to fit it.
30:21 Some of the off the shelf twin screw style supercharger kits, particularly for the LS V8s just as one example, can be a really easy solution.
30:31 Yes you could make more power with a centrifugal supercharger, but you're going to be giving away that bottom end performance and you're going to be paying the price with the complexity of your installation.
30:41 Right so that covers hopefully the pros and cons of those three options, and again really there is no clear winner, it's just dependent on what you're trying to achieve and what you actually want out of the supercharger.
30:54 But there are some really big differences between the three and it really is important if you are selecting to make sure you know what's going on there.
31:04 We'll head across to our questions, if you have any more questions, please ask those in the chat and the team will transfer those through to me.
31:13 Ben has asked, how do you set up a blow off valve on a centrifugal blower setup, is is the same as a turbo system? Yeah essentially yes it is, there is one difference though.
31:23 With the centrifugal supercharger, because it is crankshaft driven, if you back off the throttle at high RPM and the engine remains at high RPM, you're going to be constantly pumping air.
31:35 You can deal with this with an atmospheric venting blow off valve provided your ECU configuration is not MAF sensed, that's going to make some tricky aspects in your operation but that's a bit beyond the concept of today's webinar, I would generally suggest that venting the air back into the inlet pre supercharger is probably going to be beneficial because what you end up with, particularly if it's a street car is a horrible hissing noise that's quite continuous as the blow off valve continues to vent air.
32:05 So quite different to that single chuff you get out of a blow off valve on a turbo setup so venting back to the inlet will help reduce that.
32:15 Mr Wild has asked, so would I be better going with a air to air with an L67 and an Eaton M90, plumbing's a little more tricky with an air to air.
32:26 So with a positive displacement supercharger, really really tricky to add an air to air intercooler.
32:33 The reason for this is that your throttle body is going to be pre supercharger, so by adding an air to air intercooler and all of the associated plumbing from the blower to the front of the car and then back to your inlet manifold, you're adding a huge amount of volume to essentially what is your plenum chamber and that's going to really create some problems with the drivability.
32:53 Particularly what's going to happen is when you shut the throttle, you're going to end up with the engine consuming all of the air that's in that plumbing, that takes some time, so you end up with a really lethargic response to throttle input.
33:06 So water to air does unfortunately lend itself best to that sort of setup.
33:11 Alright looks like we're short on questions for today, we've only got the two of them there so again as usual for our members, if you've got any questions that crop up after today's webinar, please feel free to ask those in the webinars section on our forum and I'll be happy to answer them in there.
33:28 Thanks to everyone for joining us today and hopefully we'll see you in our webinar next week, cheers.