For what is worth heres my .02 cents.

Since you mention 3 choices I go one by one and I will add 1 More,

I assume we are talking of a 911 engine.

Supercharger

Very nice picture and indeed a piece of art,when it comes to super a 911,
I dare anyone to find me Minimum 10 500hp + superchargers 911 anywhere in the planet,then find me 10 reliable supercharger tuners,then I will LOVE to see 5 I even settle for 1! 500hp + dyno sheet and to top it up find me technical support,I spend almost 2 years doing research of super vs turbo,the super was my original plan,and 4 years later I have no regrets I do feel sorry for the ones that go this way because at the end of the day they will go turbo,trust me.

NOS
Nice add on but as we are aware must 911 owners don't have the guts to install it in a 911,NOS don't blow the engines is all the tuner and the mentality of the 911 purists owners.I have seen many 911 with NOS and not only they dare to do it they are happy too and no regrets I do feel that is not for everyone do.

Turbos
Oh boy! Well about 4 years ago I wanted to turbo my 3.2 just bolt a turbo to it ! (after giving up the idea of the super) 98% of the so called "Tuners" told me that it was impossible and some of this guys have been in bussines for a long long time,well to make the story short I did find a "tuner" and I went for, a 911 engine with the ****ty KS pistons and cylinders,66,000 miles,valve guides shoot,no internal modifications,non adjustable boost,no intercooler and we got 277Rwhp ok nothing to talk about not even that we start at 217hp from factory,I got 5,000 hard miles (since we Drag Race my 911) and never a problem so back then I was sold turbo rules! of course all this "tuners" never give us any credit and even up to this date we continue to struggle to find help INCLUDING HERE,so we have learn to do it our way and just move on,so we have triple the hp and we are running 541rwhp single turbo,single plug,with factory motronics something that I don't think a super could do ,by this week end as we are doing some test we expect to go to 650rwhp,so In my eyes turbo is the way to go,and maybe a Little aid of NOS.


Other choice ?

Methanol, as I am doing some extensive research on it, will see so maybe thats the way of the future.

Sorry 4 the long post.......

 

i guess rickc never reads posts properly. It says above that the top 928's use Vortech. WTF - are you blind?

 

If both a turbocharger and a supercharger can boost the intake pressure to the same maximum safe limit for an engine, then the engine must develop the same power in both setups (ignoring parasitic losses). Laws of physics.

The only difference should be 20hp or so due to the parasitic drag of the supercharger.

However, the supercharger tends to have greater low and mid range power, not to mention instant throttle response. Remember, the faster car needs the highest average power over the usable rev range, not just a high peak over a narrow range.

If you're mostly on straights, revving to the limit and always on boost, the turbo should be faster. If you are negotiating a lot of corners and spending more time below 4000rpm, my money is on the supercharger.

Just my $0.02...

 

So Christer..my mistake. What's it like to be perfect? Next thing you know we will be criticizing the use of our grammar and starting sentences with capitals. Got anything positive to say.
Rick
'78 930

 

Excuse my previous rant...I am not really blind, I was just excited. The real issue has to do with available space in the engine bay. If you are doing a conversion and have lots of room in front of the crank or on top of the engine , then the supercharger makes more sense... that is if you can work out the topside plumbing and don't mind a blower sticking through your hood. Power take off at the crank is a real issue that the turbos don't have to deal with. It's physically easier at least in a 911 or 930 to work with the turbos in application that exceed 500hp, while maintaining the stock pulley setup. It's not an apples to apples comparison in this post ...so we are obviously just stating personal vehicle preferences here.
Rick
'78 930

 

In 1992/3 a guy called Mike Tilson working with Exclusively Nine (now defunct) built a 964RS engine with twin superchargers-they were the flat Eaton type (from memory) - I am pretty certain that made around 400hp and had a super flat torque curve. To get 500hp with a supercharger on a 911 will be difficult since you are working with small (relative) capacity engines and lowish boost levels together with the power sapped by the S/C. To get a genuine 500hp with turbocharging requires a big single charger with the associated lag issues and usually aftermarket fuel/ingnition control (Protomotive systems excluded) .With twin turbos, it needs the right mix of bolt on's and about 1 bar boost.

 

Tito 911,
Here are a couple of links of a Z3 that uses methanol. He puts 537 rwhp and that's out of a 3.2L. You might have already seen this, but here it is anyways.

Magazine Article: http://www.cardomain.com/id/turboz3
Thread from Bimmerforums: http://www.bimmerforums.com/forum/sh...hreadid=121013


Another type of injection that is starting to pick-up is using propane injection. (Yes, the stuff you get from the hardware store and cook your hamburgers on.) People with Supras and Turbo Stealths have been running it. With the propane, it's pretty much like methanol except it's cheap, easily available, and a bottle will last you a long time. People have been using the 2 gallon tanks you get from Lowes, and as another bonus you can grill-out on the front of the Porsche if you want to. Just something else you can think about. Good luck.

~Matt

 

Thanks for the inf!
so far I been told that if we go the methanol way we need steel sleeves,but alcohol is in the horizon too,I too have check all others that you have mention and since we DO USE OUR 911 FOR DRAG RACE we try to keep up with the latests on the street,and since we are here I may as well inform that we had reached 623.9RWHP single plug single turbo with the Factory Motronics, this weekend she ran 11.98 at 133mph with a very bad driver.

 

The horsepower you are pulling out of that thing is nuts. With trap speeds like that, you should be WELL into the 10s perhaps lower. How's it trying to put all of that power to the ground? What was your 60-ft times for that run? I'm sure traction is a huge problem, but it can be over-come with slicks or DRs. Is it a street car or a race car? Screw everyone else, I love drag-racing.

~Matt

 

Wow! Would it be possible to post or email me your dyno results? Very impressive...

 

Lagavulin:

My statement of the turbo still being king of the hill holds true. It is a well proven fact that the turbo requires less power to drive than a supercharger.

Comparing your car to mine really isn't fair....you have 4 valve heads, 5 liters of displacement and 2 points higher on compression....of course it will make more power. I'm on 2 valve heads, 4.5 liters and 8:1 compression. That 500 ccs is worth nearly 100 HP on the normally aspirated cars alone....230 HP vs 318 HP.

Let's wait and see, then we can compare specific horsepower output...i.e. HP per liter...that is the only real number you can compare...and even that is skewed because of the 4 valve heads and higher compression.

You have to compare apples to apples. Guaranteed you bolt on a twin turbo setup, charge cooler(s) and the necessary hardware you will make more power on the same boost than with the mechanically driven blower.

Starting from scratch I would also do the centrifugal blower....but it is a proven fact that the turbo requires less power to drive than the blower....it is a pre vs. post sort of thing...

 

Guys without goind into specific details...........When I was doing my research I found that a lot of information that is pass in the web is "very conservative" from boost settings to how much hp can be obtain and the list is endless, it takes a great deal of desired to go the extra mile and find what must people think is impossible.

I may tell you that contrary to what everyones thinks I have ZERO traction problems and now Im running D.O.T. Drag Radials so what it was a ZERO Traction problem is now - big Zero problem,so traction for me is just heaven.

Contrary to what everyones thinks I still have a/c,radio,power everything so my car is 100% street legal and I do drive it in the street as long is not raining.

Contrary to what everyones thinks this cars are a awesome drag cars trust me,that people dont think so fine, I continue to walk in the Dark side and I like it.

I am very aware that we should be in the 10s but Im a bad driver period.

Never Mind that we just race the other nite a 650 bike from a 65mph roll and at 170mph we had 3 school buses in front of him.

By Dec we hope to have 750Rwhp then will see what happens.

Im happy that you guys enjoy it as the Porsche comunity has turn their back on me just because I drag race it,BUT I been bless with a group of people around me that are making all this posible and then some.

Can this power be made with a super ? Please let me know

 

I love to drag race myself and your car sounds like it can take care of business. I can see by the mph you are making power good luck with getting it hooked up.


George

 

I just wonder how ‘well proven’ it is as we are talking about HUGE pumping losses with respect to turbo chargers. From the exhaust valve and piston perspective, the turbo(s) look like a potato is stuffed into the exhaust.

I used the following analogy before, but it bears repeating.

Let’s suppose you are in a building and are in the process of making your way out to it’s single exit (..you are an exhaust ‘slug’). In a normally aspirated engine, that exit will look like a wide open door in which you freely pass through with no resistance. On the other hand however, the exit for a turbo charged engine looks like a revolving door in which you have to physically push and exert energy onto the door (..vane) to order exit. Now let’s look at this phenomenon a little closer in more detail.

The vane of that revolving door is connected to another revolving door on the second floor of this ‘building’, and the job of this vane on the second floor is to grab people from the outside, and cram as many of them as possible onto the second floor. So not only do you have to push on the door to get out, you are also pushing against the mass of all the people who are pushing on the door in the opposite direction on the second floor; that takes a lot of power.

Can you as one person (..exhaust slug) be able to do this on your own? No, it will take the assistance of the piston moving upward on it’s exhaust stroke to smash you against the door so that you are literally forced, thus enabled, to physically move it so that you can now exit the ‘building’.

Since this piston is on it’s exhaust stroke, it is not producing power. So it must get this enabling power from somewhere, and that ‘somewhere’ is another piston that’s on it’s power-stroke. Since that piston is on it’s power-stroke and is forced to do work by pumping spent gas out of another cylinder, that’s power being spent right off the top (..pumping losses), which means that that power cannot be used to drive the rear wheels.

On the other hand, a centrifugal supercharger does not impose an exhaust restriction nor incur such a large hit with pumping losses. But by the same token, it’s spent exhaust gases are not helping to power the blower unlike the turbo.

The question becomes, can the centrifugal and it’s free flowing exhaust overcome the advantage the turbo has which is harnessing the spent exhaust gases, but likewise incurs large pumping loses through exhaust restriction?

Let’s suppose for the moment the turbo is indeed more efficient. So I ask, how much more efficient is it over a centrifugal? I would guess-timate that the difference is small, and I say that because what a turbo gains by using exhaust gas to power the turbo is consumed by the corresponding pumping losses.

Since I do not have Corky’s Turbocharged book, what does he have to say regarding this matter? Does he provide any numbers? I would like to see these ‘proven facts’, versus people merely repeating what they’ve heard from other people, etc, without thinking it through for themselves.

I am definitely open for discussion here, as always.

Well, I didn’t mean it to be a comparison. Originally this thread was posted in the 928 forum where you said ‘..the turbo is king’. My point is that within the 928 community only, it’s the centrifugal superchargers at the top with the big horsepower numbers. I meant no disrespect towards you and turbos, and was merely stating a 928 specific ‘fact’. I guess I should have been more careful with my wording, and for that I’m sorry.

 

Lagavulin, what car do you have? Your signature just says '87.

I have always wondered about the 'hard to measure' losses of a turbo versus the easy to measure losses of a compressor. If air is being compressed to the same pressure in both cases, then the same amount of work is being done. And that energy must be coming from somewhere... I don't believe that energy from the exhaust is 'free' as so many turbo enthusiasts put it. Perhaps the supercharger has higher losses due to the higher weight of the moving parts? I'd like to see a supercharger with CF rotors

Finally, has anyone looked into the adiabatic engine? That looks like the best option, if only you can find someone who knows how to build one!