Seth W

Bill:

Sharing our discussions, I researched this issue in depth, and could find no good reason to go with an Autorotor over a Roots where boost was less than 10-12 psi. Seeing as how I'm running 1/2 this amount, I chose to save the $ and go with the Eaton. Better bang for buck, easily rebuilt, purchased, serviced etc.

Shmurzik

Seth,

Have you had your car dynoed [?]? Because to me it seems that most low boost kits offer somewhat low pay off in horse power and torque relative to the cost. And for the higher boost set-ups there could be longevity issues (I don't know if there are enough of them out there to make any kind of a judgment, so it’s just a bit of conjecture here).

blau928

Bill,

You would have to look at the compressor maps you want to compare to find out. In similar sized compressor maps I have examined inpast, there have been differences in output charge temperature, and also in shaft power required to spin the compressor...

I am sure Andy may have some comparable maps for you to look at. I can say with full knowledge that the Autorotor 2.2 Compressor is more efficient than the Whipple 2.3... I explained this to Andy 1-2 years ago...

Again, compare the complete set of parameters by looking at the maps.. Another extremely important point that so many miss, is that HIGHER BOOST IS NOT EQUIVALENT TO MORE AIRFLOW.
Boost, PSI is measured as resistance to flow.. You should be looking at the CFM or KG/min or #/min of airflow. You can have a system moving more air at less pressure than a comparable system.

I have stressed this uncountable times, and so many still use PSI as a measurement...

It sounds like a lot of work to figure this out, but it's not... The maps let you know a lot more than the blah blah blah of many who can't even tell you what adiabatic efficiency is..

My $.02

Bill Ball

Seth:

Yes, that's my understanding. Just wanted to see what other had to say on that. Richard, to that end, I'll have to look over what you are saying and try to digest it. Thanks for the input.

Anyway, let's have fun with these kits. I fully agree that Tim, Andy and Carl offer great service with their kits. We are very fortunate to have them as 928ers. You can't go wrong with their products.

I'm really anxious to see your cosmetic enhancements. I'm sure they will dynamite. Since my engine compartment is clean but not polished in places like yours, I'm banking on the raw metal look being best for me.

Looking forward to an install party!

Seth W

Seth,

Have you had your car dynoed [?]? Because to me it seems that most low boost kits offer somewhat low pay off in horse power and torque relative to the cost. And for the higher boost set-ups there could be longevity issues (I don't know if there are enough of them out there to make any kind of a judgment, so it’s just a bit of conjecture here).

Shmurzik: Nope. But if you can show me a better HP mod for the price, I'd do it. I'm planning on getting at least 75-80 RWHP out of this. That is very conservative and will easily put my car over 400hp at the crank. I'll be doing a before and after dyno so we can see exactly what the effect is on a well maintained car.

GoRideSno

Seth,
Thanks for the kind words! It has been a pleasure working with you. I am looking forward to the install and the results of our efforts.

Bill,
It is very commonly held that in normal applications that below 13psi that the twin-screw has very little adv over the eaton improved roots type SC. For our application where boost is generally lower for the same SC rpm the advantage comes into play at (my best guess) around 9psi.
It's also a ~$1300 price difference.
Let's not forget, I have made more power with the Jag/Eaton M112 than I have with the Autorotor. Though I will be making much more with the autorotor soon.

Andy K

Bill Ball

Thanks, Andy. I thought the M112 was doing very well in this application and that the Autorotor advantages were not realized at this level. They may provide cooler charge and a few more HP, but nothing significant enough to be noticeable.

Soon it will be time to party!

mspiegle

Lets not forget the fact that the eaton roots blower is in OEM use with alot of car manufacturers. You can't beat the reliability... these things have been around forever.

GoRideSno

There is hardly any difference in efficency at all between the Autorotor 2.2 and the Lysholm 2.3. Engine HP would differ by less than 7/10ths of a percent between the use of these units. Once again marketing wins over technology if aynone believes that the Autorotor is that much more effiecient than the Whipple. The main reason I went with the Autorotor over the Whipple is: Autorotor = direct from source = $1900.00. Lysholm = only available in US through Whipple (third party middle man) = $2400.00. $500.00 difference same performance and possible more durable, more information available. I've run both, I would run either. I do make some small markup off the Autorotor though, so keep up the marketing effort.

The Jag/Eaton M112 setup is the best (large) bang for the (large) bucks for the 928. Depending on the fuel octane in your area you can get up to 120+ or more CPH for $3745.00 or $4045.00 and a day to a day and a half of installing. There are well over 20k mi on the Stage 1 and 2 Jag/Eaton M112 system between Mike's 86.5 and my S4. Both cars have same compression as before SCing.

There is a '87 S4 that has nearly 230K mi on the original engine and has had one of my intercooled twin-screw kits on it at 8.5psi for the last 16k mi. I abused this car to test it then drove it from LA to ATL in 36hrs. It is now daily driven by someone that knows almost nothing about cars. It also passed GA smog on a rolling chassis dyno with #s that excede the CA emissions test standards. It has not had one problem. Now please expalin the longevity issues to me.


Andy K

Shane

Oh, so that is why I got the Whipple 2.3 so cheap. Damn i wanna upgrade!!

Joking, I'm happy as a clam to have the only Whipple running on a 928. When you are on boost and accelerating rapidly down the road you don't have time to think, "Gee I could of had a more efficient Autorotor".

GoRideSno

Yuuup, Just think Shane, you could have had almost 2.8 RWHP more than you do now if you have gone witht the Autorotor. That 2.8HP would have only cost $600 more in your case. .
Andy K

goliver

Seth congrats. That thing is gonna be a monster. BTW, you have a PM.

Regards,

blau928

Andy,

On a pure technical level, you are saying that a Lysholm compressor with 5% greater capacity that is less efficient than an Autorotor with a smaller capacity only equates to a .007 hp advantage on your system. Granted this may not be a nominal amount, but nevertheless it does prove that the smaller compressor is more efficient assuming your tests are carried out in the same environment.

As far as marketing over cost, I am not in the business of making and selling SC parts, or kits for the 928.. You Are. Whatever the reason you chose to use the Autorotor Compressor, is of course your decision.

What I mean and say when I point out that a smaller compressor is more efficient than a larger one is exactly that. On a technical level it is, pure and simple fact. No subjective arguments based on this car vs that car vs this system vs that system.

POST THE COMPRESSOR MAPS, and we shall see the same differences as last year on tests in a similar environment for both compressors. No marketing there, just fact and data to support it. I am sure you have access to the charts.

As far as me marketing these compressors, I do not believe that my writing about compressor efficiencies would have any effect on your business. If it does, then great for you... I am surely not being paid to do this, and will not ask for compensation even if the few paltry words of fact help your business

One more thing.... Your system at 5 PSI may not be moving the same amount of air as another system with the same compressor, or in fact a different compressor..... You can explain that confusing one if anyone wants to know. I will stick to it, and say that this is also proveable....(another system design can in fact move more air and make more power....) Not knocking your system, just stating scientific fact.


MS,

This does not mean that the compressors are more efficient than the Autorotor Compressor. I already stated that it is due to cost... NOT Efficiency.. Efficiency can be found in the compressor map..

Andy has just disclosed this even on his Autorotor vs Whipple... The Eaton issue is also a cost issue, and being that you can get a practically new one on Ebay for $500 has the same cost issue effect. Cheaper, YES, but not more efficient as a compressor.

A properly engineered system costs a bit of $$$... Due to the volume of sales needed to recoup the costs, and the size of the 928 market for these products, it is an issue of cost vs power increase in this market segment. That the result in a better engineered or more efficient system is not always the case when cost is factored into the equation.

Does this cost issue mean that a better more efficient system cannot exist..?

It again sounds like I am repeating myself... Anyway, good luck to all in SC land whichever system you have or decide to get.

Cheers,

GoRideSno

Richard,
You didn't say anything about the efficency v/s size of compressor. You said efficency period. Sure, the efficency margnis widen over 7/10ths of a HP if you consider displacement. Shearly a technical argument that has no bearing on performance though. Displacement is irrelevant to actual performance. Size and weight have more bearing on performance than displacement. When I said marketing, I meant marketing for me. As I mentioned, I actually make a margin off the Autorotor.
http://www.kennebell.net/techinfo/fo...RvsLYSHOLM.pdf

Very candidly I have to tell you that you just don't seem to think practically when it comes to this stuff. Sure you know a lot of technical stuff and clearly enjoy sharing it but you seem to have very little sense of what is practical. Anything can be done, BUT....someone has to actually do it for the statement to be valid.

BTW how is your SC system coming along?

Andy K

bcdavis

Exactly!

Most of us could care less about all the scientific arguments about aerodynamics, horsepower, efficiency, etc...

If you think your methods will yeild amazing results, then do it, and prove it!

And most likely, the people with the really amazing scientific methods, will end up with *very* fast cars.
But the "can-do" people like Andy, will already be driving fast cars, and for a hell of a lot less money.
I am sure that if I could pay a formula one design team to build my car, I could get all the best technology.
But it would cost a fortune. Technology and efficiency costs money...

All most of us want, is rubber-burning power, and Andy's kit delivers that for a reasonable price...

I could care less if his air pump is more or less efficient than a turbo, or a CS.
As long as it gets me power to the wheels, and it makes my car fun to drive, I am happy...