superchargers in racing...

[pitviper]

okay...what is everyone's opinion on superchargers and their use in road cars or the use (or lack of) in racing? what advantages/disadvantages do you forsee in racing applications? am i correct in that superchargers are used primarily (in racing) in drag racing? for the throttle response, no? reason i ask...there are a lot of cars out there that would be good to see on the track, particularly in GTS, but they are supercharged, which is forbidden if i'm not mistaken. examples? the Ford GT, many AMG models, the Mercedes/McLaren SLR, even the new Zonda to be launched Geneva 2006 may be carrying the AMG supercharged V8 (that's still up in the air, the only thing i do know is that it will be an AMG engine, and i can think of better ones in that lineup). so do you allow supercharging to cater to these cars? what would be involved in switching to a Turbo setup instead? obviously spacing, engine mapping, etc...anyway...jsut wanted to get the general opinions, since we are all experts

pit

[gttouring]

well you know supercharger feed air into the motor but they (on many road car applications are part of the intake manifold-AMG, and i know Paxton and powerdyne superchargers are of the turbine type not roots...)
so this present the trouble of a hot intake charge and not doing as well a job in race conditions i feel. they have been used in the past but they aren't around nowfor some reason-although in SPEED GT the realtime Acure NSX is fitted with one. i also believe that the torque benefit of a supercharger is a bonus but the top end of it isn't
exactly to turbo spec. you see the pulley driving the blowercan slipp at ridiculously high rpms and thus lessing the benefit of the boost.
now the internals for a Turbo and a super charger should be alike as they both deal with very high cylinder pressures. The turbo has the benefit of spinning and producing consistant boost at higher rpms as slipping is not a problem- heat is as a supercharger, but the amg design involves crazy plumbing to use an inter cooler and the turbo can use it with less headaches. so the turbo now will continue adding air into the upper ends of the rpm ranges and that is good at LeMans at any long track, in a tighter circuit like washinton DC in the ALMS last year A supercharger may have worked well as there was less need for ultra high rpm, when it is going right a supercharger acts alot like a big Naturally aspirated motor. a Turbo doesn't ow we'll let someone fight over turbo Lag and supercharger parasitic drag. (I don't think either are a problem anymore with bearings and friction material nowadays

[Dani Filth]

I don't think the SL55 AMG/SLR .. have Kompressors .. but the SLK 32 AMG does ....

[BSchneiderFan]

I'm fairly sure the new SLR is supercharged, you know.

[gttouring]

or is the new slr a twinturbo from the Maybach?
Kompressors are the superchargers aren't they

[noise boy 2]

I actually floated this one a while ago, at the IMSA forum. The problem with superchargers (both roots and centrifugal) is that the turning of the impeller takes horsepower, the turbo, on the other hand, uses the exhaust gas flow to turn the impeller, so it is effectively making something out of nothing. Hot Rod just ran an article last month where the ran a roots style supercharger(ie the top fuel type), a centrifugal supercharger and a single turbo on a 5.0 ford motor. All three units ran at 9.5 lbs boost, (except the roots unit which could not be spun fast enough to generate that much boost, the verdict was that it was probably too small for the engine), and the turbo whipped the other two by a substantial margin. The only type that didn't test was a screw type supercharger which doesn't suffer the same problems with heat generation that the roots type does, although they look very similar on the outside. The problem with the turbo is packaging in a street car, the exhaust routing is a lot more involved and there has to be room for it under the hood. The other part is that turbos are much more sensitive to cam profile as the exhaust gas is an intregal part of the operation. For street cars, the supercharger is easier to package and to control the boost on. As an example, my father owns a 1999 Lightning pick up with a factory installed roots type super charger with a air to water intercooler (to cool the inlet charge, every 10 degrees of inlet temp reduction is worth about 1% horsepower increase and a lessened likelyhood of detonation) and it is docile as hell around town, but if you stomp on the loud pedal, it accelerates like a rocket (turns and stops great too thanks to the kind folks at SVT). I will try and remember the magazine tommorow to get the actual performance figures. Robert

[Tim Northcutt]

A contributor to this forum, IanGrohse, has worked with both turbos and superchargers in actual race cars and for this type of racing, he says that a Turbo is much more effective than a supercharger, and that the heat is a big factor in this equation...

Concerning the twin-screw type supercharger...

Two years ago, I got a lot of info from one of the Whipple family members who runs Whipple Superchargers....they build and license the Lysholm-type twin screw supercharger....

These things I do know....

A twin screw blower is the most effective supercharger throughout the entire rpm range....and due to it's efficient design, it generates approximately as much power at the top end (amybe a little less, but not much less) as a centrifugal unit, and any actual dropoff is not as significant at compared to a roots-type vs a centrifugal blower,

Also, the twin-screw system more than compensates for the "robbing of horsepower" that a belt-driven centrifugal unit suffers from in the lower rp.m. range before the pressure can build enough for it to kick in...a definite plus in a road racing application...

Intercooling always helps with the horsepower and reducing heat build-up, but Mr. Whipple said that the twin-screw sustem does not suffer from excessive heat in the same ways as the other types of blowers due to its efficiency of its design...

When you read the stats on a Whipple twin-screw system, they can pump up horsepower by as much as 30-35% in an engine....

go to www.whipplesuperchargers.com if you want to read the specifics of this type of blower, and take advantage of their "contact us" link on their site...they were very responsive to me, and were very comprehensive in the information that they gave to me...

I still don't know if they are as efficient or as effective as a turbo for total power, but turbos certainly are more expensive due to the wastegates and even more plumbing needed to make them work, and they run hot as well...

Overall, I would probably go with a turbo, just because there has to be a whole list of specific reasons why no one seems to run superchargers in endurance or sportscar racing applications -- heat build-up and subsequent reliability vs. the power efficiencies of the two systems among the most prevalent reasons...

But I'm not an engineer....

I'll bet Whipple could make a pretty strong case for why they could or should be used in sportscars, and you'll learn a lot about both turbos and blowers from them....

[gttouring]

um belt slippage- I brought it up and actually would like to know more about it, it even happens in Top fuel, a tooth in the cog gear breaks and the belt slips- this is just a loss of power then, a turbo won't have to deal with this problem, as no belts are there to break or slip, hence the extra power is available, of course you could run a gear set up to the supercharger but I imagine the HP gain vs. the boost you run would be less.
when a belt slips the SuperCharger cannot provide boost it is supposed to, as the pulley isn't spinning fast enough and so your motor isn't huffining liike it should.

[Dauntless]

Tim, Whipple makes a fine product for low and moderate rpm levels, but is inferior to a turbocharger in racing applications for several reasons.

The simplest and most obvious reason is that it's axiomatic that any mechanically driven supercharger must draw net power from the cylinders' combustion process. If a typical Roots blower draws 60 hp to turn it at its design RPM, and a Whipple is 50% more efficient, it must still draw 40 hp net from the engine. A turbo, OTOH, uses (primarily) the waste heat ejected from the cylinders AFTER their net mechanical work is complete. This is, in essense, "free" energy that the engine would otherwise reject into the atmosphere. Of course, there is no such thing as a free lunch in nature, and it can be shown that all turbos do in fact extract a certain amount of additional energy from an engine, but it is comfortably under 1% of the engine's output.

So, fast-forwarding to a hypothetical racing engine on the dyno for a back-to-back test, we would see that, all other things being equal, a turbo engine would have that 40 hp drawn by the Whipple available to do useful work at max power output. THAT'S why an otherwise identical turbocharged racing engine will always appear superior to the same engine supercharged.

OTOH, a Whipple is often superior to a turbo in "power under the curve" at low and moderate RPMs, which is why many car makers have gone to superchargers in place of turbos. Each has their place, and in racing, that place is taken by turbos.

[pitviper]

so is there no place in racing for cars whose which road versions use superchargers?

pit

[dretceterini]

Lancia was pretty successful using superchargers and turbos at the same time

[gttouring]

well pitviper, the racing application for a supercharger for say 650 hp as a comparable twinturbo V8, the turbo run much less boost (in PSI,Bar whatever you want) and the cylinder wall presures would be lower for an ideally set up supercharged V8 with 650 hp. the supercharged motor would run slightly higher boost to over come the parsitic action of having to turn the supercharger itself, and correspondingly the cylinder pressures would be higher.
but they both will run into problems, I feel that current technology can make both effective, but the turbo ultimately would be a safer engine., you see as the rules at LeMans are the comparabley equipped Merceds may have 600 hp and 600lb/ft. of torque or whatever but it is also a huge block-what isit 5.9litres? too big for forced induction. it would have to be scaled back to 4.0 or under.
does this sound correct?

[pitviper]

do the rules say "forced induction" to mean any method? or is only turbocharging allowed? i can't remember...keeping in mind i'm looking specifically to GTS

pit

[Tim Northcutt]

To Gttouring & Dauntless:

You make many of the same points that IanGrohse made when this issue came up about 5 months ago....and I agree with you that a turbo is the better route in this particular application...by far the better choice....

BTW...this came up in a thread about creating an LMP 1000 class for privateers instead of the 750 or 675 classes and adopting basic CAN-Am specs, but looking at a 4 L to 6 L "forced induction" engine formula that would not allow turbos (an unfair advantage for the 200 lbs. of added weight over a 900 car)but only superchargers.

However, just to play "Devil's Advocate," let's take a hypothetical team that wants to compete next year in ALMS with a goal of getting one of the automatic bids to Le Mans by scoring in the top three in their class in season points....

There are certain circuits that have been, or are currently on the ALMS calendar that just might lend themselves to running a twin-screw supercharger on a 3.5 L engine like the IRL 3.5 L....especially since they are shorter races....follow me on this one:

I'd look at trying it by "Cherry-Picking" the circuits that do not have the long straights, but you need the power in the lower and medium rpm ranges to get out of corners quickly and to the next set of curves...courses that don't necessarily give the turbos an advantage, and in some cases can negate their power advantage, unlike the obvious advantage they seem to have at places like at Road America, Sebring, etc.

Specifically, I would think about the twin-screw supercharged engine at:

Trois Rivieres

The Washington D.C venue where they raced last year (if it ever comes back)

Any new Street Circuits that would be added in future years...

Laguna Seca

Sears Point

Possibly Miami, but that would be a stretch -- it is a street course, but it does have that fairly long main straghtaway......

Also possibly Mid-Ohio (if they ever go back)..

My thought: The twin-screw supercharger wouldn't have the lag of the turbo, yet would crank good lower end power like the normally-aspirated V-8s (Elan comes immediately to mind with their wins at DC and Sears Point last year...the low end torque offset Audi's superior power and speed from the turbos)...

The biggest "If" on this would be gttouring's point on belt slippage...a huge concern....especially with all of the slowing and accelerating and the range of rpms that the blower (and its belt) would have to endure in circuits of this type...

Now...your thoughts?????

[noise boy 2]

I believe that the belt slippage issue would be able to be overcome, and we are only talking about 7 or 8 psi max boost (which is the boost range of the average street supercharger kit here in the states)per the sliding scale at the ACO website. The top fuel cars run more on the order of 18-20psi and a much more violent fuel (nitromethane), as well as dual injectors (a complete set of injectors on top of the supercharger, and a second set at the port). Here is an interesting article on a whipple charger, and there is a discussion of belt slippage in the sidebar article:
http://www.hotrod.com/techarticles/52182/index.html
Robert

[gttouring]

how ever NoiseBoy2 we are not using the average supercharger kit-and a pulley for the s2000 kit can be had to create 12 psi, so this is easily and safely attainable. so if we are running equal boost as the Audi's ...and from your link and talk of belt slippage- ok possibly dealable, but
"Whipple also offers a twin-2100R blower system that uses a stock 6-71 supercharger intake manifold. With twin Whipple Chargers on a twin-carbureted 454 with aluminum Dart heads, this engine made 880 horsepower at 12 psi. Whipple’s goal is to make 1000 at 18 psi"!!!!!!
12 and 18 psi very huge i'd think and of course the engine is 7.4 litres but we needn't use that we don't even need 880 horspower, so a 4.0litre motor at 18 psi with fuel injectors and not carbs, could very well run 650 or 700+ horsepower, at lower RPM so a less stressed motor, and stinkingly high horspower- this may be more fuel to the fire in the Turbo/Supercharer fight.
As mentioned in SpeedGT the Realtime Acura NSX used a supercharger, and made comprable HP to the Porsches, in fact they turned the boost down to keep it from winning, although this may be due to Cunninghams skill, and the nimble NSX chassis more than the supercharger, but it must have been outrageously strong- any one have the ACO rules on Boost levels ? links?

[noise boy 2]

http://www.lemans.org/sport/ressourc...XE_A_GF_GB.pdf

Here are the boost regs for the ACO, interestingly there are higher boost specs and larger restrictor openings for 2 valve per cylinder engines. Remember that atmospheric pressure is included in the boost reading which is approximately 1013mmbars. Robert

Also here is the page for the complete rules and regs in english.
http://www.lemans.org/sport/pages/re..._2003_gb.shtml

[gttouring]

thanks interesting- of course it does not differentiate in LMP/LM900 whether or not it is turbo or supersharged boost, i am presumming it is going to be the same, now why is 675 relegated to only NA and turbo? whay do they not make the distinction in Lm900 about turbo-super-NA?
and i would say those tables are just wacky in the set up
simply placed in columns and rows you could work this out, does the ACO ever thunk of Using Excel? waht a bodged up chart...should be one for NA one for Turbo and One for supercharging and then the variations of each on valve number, i digress...

[Tim Northcutt]

You make excellent points...gttouring and noiseboy2...

There should be some sort of differentiation on the p.s.i's...

Now, have nay of you given thought to the "Cherry Picking" idea for certain circuits????

Obviously, you would have to run a similar powerplant with this plan...that's why I thought about the IRL specs engine...otherwise you would be changing out gearboxes and all kinds of things to make it work, plus it would affect the balance of the car...

Another question...has GM ever put a supercharger on the V-8 that the Cadillac team put the turbos on when they ran the LMP program over the past few years???

If yes, that might be the engine package to go with to do my "Cherry Picking" with the twin-screw blower....

Would this make sense to think about doing it???

[gttouring]

i like the IRL engine idea as the 3.5 and the 4.0 litres are lying around somewhere, even though many4.0 where converted to 3.5 via new cranks...
sure cherry picking the motor and all would be great for differnt circuit but then why not have different motor altogether- i.e. use a twinturbo, single turbo, supercharger and natural aspirated motor whenever it suits you.
and on a side note- some blokes down fro the BAJA 1000 were doing this very same thing-i mean they were all running big trucks with varying motor configurations-one team ran a 7.litre turbo diesel ford with like 600 hp and 750lb.ft of torque, another guy used a big Motown pushrod crate 8. X litres at 8.5 copmression and had 750 hp and 600+ lb'feet of torque (at a meager 6700 rpm) and they had fuel mileage issues but stopped to fill up on 'pemex' the Mexican Petrol standard consumer pumpstations. and another guy was running a Toyota DOHC 4.5 litre motor (i assuma a stroked 4.3 litre aluminium lexus motor) and had a twin turbo set up on the 600/500 ranges.
the Diesel was too heavy but it was a motor tester refueled once. and the Motown block was a guzzler but ran very fast, the toyota broke, the turbo manifolds cracked and they had no boost pressure - ahh good old custom fab...
the point is any motor combo can be had to produce great power (no supercharger sadly in my examples) and they all run into issues, so our privateer team better do the homework- the IRL engine have too much compression to run boost safely, so if we get a 3.5 litre and stroke it to 4.0 we may alleviate some boost (or 3.9 to be safe) and run a supercharger to make up for lost torque on this higher spinning mill, it could be the turbo killer.
no to twin turbo it we would deal with the same trouble with the compression but, we run the risk of bad manifolds, or turbo plumbing connections-oil lines etc.
so if we were going to build one, i would opt for the supercharger as the crate motor at 6.0 litres max might not get us as high power as we want.

[Tim Northcutt]

Thanks, gttouring.....

As long as you were working off of a similar make or configuration, I like the idea of Cherry Picking in that way...otherwise you would be changing out various parts and you would have to rebalance your chassis package for handling, weight distribution, etc...

To take the Cadillac idea one step further, just buy the LMP chassis and engines that team Cadillac ran last year so that the chassis & engine mating issues would not be a factor, hire the engine man and the chief engineer from that team, then work on the supercharger side of the equation for the street courses , Trois Rivieres, etc....

It would save you from reinventing the wheel...and that package that was dumped by Cadillac was just beginning to pay some dividends...you'd be in the ballpark from the very start, and by the end of the 2004 season, you'd probably be making your reservations for May and June 2005 for Le Mans...

On the IRL engine...I'm sure that with different rings as a start, and other minor changes, you could lower the compression in those engines enough to mount a blower or a turbo to them....but I'm also sure that you'd grenade a few of them on the dyno while you were finding out exactly what works and what doesn't....

The Cadillac/Northstar approach would at least give you a baseline to work from, and would let you focus on the supercharger issue for the "Cherry Picking" races that you'd race the blower motor in...

Overall, it would be the most cost-effective way to try this plan...

[gttouring]

so who has the money, i can drive and do primary testing...lol

[gttouring]

although-i would think that superchargers havea great potential, in essence it is a naturally aspirated motor, so the parasitic drag of pulleys is nagated when final out put is rated at say 700hp and 650lb/ft torque, corect. no matter what the supercharger is sapping from the engine to run itself the end result is what counts. now a turbo may run similar numbers with the slight lag fro these motors i would think it is about the first 1000rpm. and if it make s the same numbers the only real difference is packaging, and power curves, and at top RPM for the turbo say it was 9.5K and the super charger was 8K-does it matter?
at 200MPH if you are spinning 8 or 9 K it doesn't make a difference, Perhaps this Northstar, or SuperCharged Elan ((the Zytek maybe for the PAnozLMP07) as the Zytek was 4.0litres... of course the Northstar caddillac is currently the better more fully developed chassis.

[Tim Northcutt]

As noted in my ramblings earlier, the twin screw will give you boost throughout the rpm range...the Lysholm type blower literally was a pure industrial-application air compressor -- probably the most effieient one ever built...that was applied to the automotive industry as a supercharger later...

I don't know when the turbo lag goes away, but on a centrifugal supercharger, probably because of the parasitic drag, takes higher rpm than 1000 to kick in...

I do know that the pinwheels in a turbo have to spin at least a certain rpm before they build enough pressure to pop hard and really work properly...

My whole premise is that the turbo's top end would be better, but the low end power of the blower would be better than the turbo until it kicked in....

Thus the twin screw blower for the street circuits and/or the ones without long straights that would let the turbo really wind out and crank it up...

If nothing else, it would deserve a serious look....

[gttouring]

I understood the premise of the two power adders- I was curious as to the overall effect. under the power curve at lower RPM's the Super has the advantage as torque is huge and immediate, now the turbo gains power through speed and High revs=more exhaust gas pushing through and more spinning and stuffing air, at what speed would the Supercharger drop off? adn if the motor is built or the fuel managemnet i stuned to make the power band of the supercharger work eenly throughout the rev range, it mat be superior. as Low end is a given, the top end need tuning- we can't have theSuper charger vanes, or screws spin too high rpm (33,000 is a very normal figure i believe check Paxton) any faster may be into the sound barrier causing harmonic trouble in the motor (same with turbos) so there s a physical limit, which i believe is reached quicker in the supercharger, but is a vette can run in the 7K range through leman I believe a supercharger can work, very well rivalling the turbos, trouble is a screwtype charger is very tall, and packaging is tough, now in the Caddy where we are working on a street battler, the benefits can carryover to a longer course like RoadAmerica, road Atlanta, and lemans, simply because the low end torque (provided we don't over pwoer the rear wheels and chassis) will be signifigantly higher to worry about simply mapping and perfecting the upper ends of the power band-making the top speed work out very well- after all the Mecedes SLR is electronically limited to 155MPH so we imagine it can go much faster