Porsche 911UK Forum

Welcome to the @Porsche911UK website. Register a free account today to become a member! Sign up is quick and easy, then you can view, participate in topics and posts across the site that covers all things Porsche.

Already registered and looking to recovery your account, select 'login in' and then the 'forget your password' option.

DON'T BUY A Gen2 TURBO!

ACHTUNG said:
An interesting subject but a few other things to think about-

You are both assuming that a normally asperated engine runs at 1 bar induction pressure at the cylinders. Actually it runs at a vacuum. This will have a large effect on your calculations.

I wasn't:

Admittedly, this will be at slightly less than atmospheric pressure thanks to negative pressure. This is caused by restriction and non-laminar flow at the throttle body aperture. This equates to, say 95% efficiency.

The negative pressure I refered to is your "vacuum". The disputed 95% was a suggested partial pressure ratio.

If anything, Wattie was right and this reduction coefficient is lower and hence bodes worse for potential benefits of this kit.

As for the Laws you refer to, are simply the complementary partial equations constituting "The Combined Gas Laws" (not forgeting the Gay-Lussac equation forming the final rearrangement). In any case, any complicatication/refinement to the calculation further diminishes the possible benefits of the system.

You can consider the scenarios calculated to be best-case rules of thumb.

Same for Reynolds factors, any additional turbulence, pressure and flow density adversely affects possible benefits.

Finally, I did suggest that for genuine benefit the system would require mechanical lowering of intrinsic compression ratio (all FI installations should run at what would be a lower NA ratio)

technically in-cylinder compression ration should be mechanically reduced within the engine on the addition of any form of forced induction, but we'll ignore that finesse, as eCharger have

In addition, this would normally include, as you suggest, a redesigned piston faces and/or cylinder heads for optimised swirl
 
The problem is that to generate boost a boosting device always needs to be a step ahead ie it needs to pre-charge the intake system constantly through the rev range with enough pressure to make a difference. If it cannot do that across the entire power curve then it's a liability.

On a 250cc engine these things may generate more power(just) but on a 911 just forget it as they cannot charge enough sustained boost pressure.

Cheap and nasty products that should not be anywhere near a 911

http://reviews.ebay.ca/Electric-superchargers_W0QQugidZ10000000001006764
 
I think it is time to draw this thread to a close - it is getting rather silly...

The OP ridiculed this piece of kit by stating 'tongue in cheek' that it would match a turbo...

In actual fact even the manufacturers only claim a 5% increase in power:

At 5% Boyles, Charles', and Uncle Tom Cobbley and all's laws are, quite frankly completely irrelevant - as are lowering compression ratios and redesigning combustion chambers...

FWIW I am quite certain this product will achieve the manufacturer's claims, but then so would drilling a few big holes in your airbox, or fitting a K&N induction kit with a paper cone filter, or polishing the intake ports, or switching to BP102, etc...

Yes, it is a con... (it ain't worth $400)

But, it will do what it says...

And no, I won't be buying one...

It isn't the best way to spend $400 to get another 15 bhp from a bog-standard pre-996 911 (they only guarantee the power boost up to 300 bhp)

So, can we all stop Googling 'engine thermodynamics' now and stop showing off which laws we know the names of now? :thumb: :grin:
 
Wattie said:
Actually, I wouldn't mind betting you'd get the 15 bhp just from that width of intake tract and open paper filter alone... What does a K&N induction kit give you?

Thought you might like a partial answer to this question at least: a K&N paper filter on my 993 gave 2.6bhp no other changes to induction - just the filter change.
 
Wattie said:
I think it is time to draw this thread to a close - it is getting rather silly...

The OP ridiculed this piece of kit by stating 'tongue in cheek' that it would match a turbo...

In actual fact even the manufacturers only claim a 5% increase in power:

At 5% Boyles, Charles', and Uncle Tom Cobbley and all's laws are, quite frankly completely irrelevant - as are lowering compression ratios and redesigning combustion chambers...

FWIW I am quite certain this product will achieve the manufacturer's claims, but then so would drilling a few big holes in your airbox, or fitting a K&N induction kit with a paper cone filter, or polishing the intake ports, or switching to BP102, etc...

Yes, it is a con... (it ain't worth $400)

But, it will do what it says...

And no, I won't be buying one...

It isn't the best way to spend $400 to get another 15 bhp from a bog-standard pre-996 911 (they only guarantee the power boost up to 300 bhp)

So, can we all stop Googling 'engine thermodynamics' now and stop showing off which laws we know the names of now? :thumb: :grin:


But wattie...

You have not mentioned the chemistry of combustion and the effect of the level of Carbon Monoxide and Carbon Dioxide on complete combustion, incomplete combustion and how the stoichiometric air fuel ratio is unfortunately never quite achieveable even with forced induction. :)

Not to mention the benefits of using Zirconium cell closed loop oxygen level monitering to get as close as possible to the stoichiometric air- fuel ratio under changing engine loads as already mentioned. :)
 
Sort of inspired by the new BBC experimental series "Bang Goes The Theory" and, well, as they say, the proof is in the pudding.

To end all the idle speculation I have ordered one, and on condition it passes Customs without getting me incarcerated for 90 days on various "Super Gun" stylie terrorist charges, we can have a RR verification.

I have a 3.4 X51, so anyone with 3.4 std, 996/997 3.6 std, 3.6 X51, 3.8 std, 3.8 X51 or any watercooled 996/997 GT3 (to check effect on highly tuned NA) are welcome to join me.

Please add your name here, or PM me and I will try to organise an RR session so as many varients as possible can take part.

If you are overly worried about OPC warranty, don't bother. However, I do intend to return all participant vehicle to standard after the test (we need before and after anyway).

Of course, if anyone is completely besotted with the device on the day, you are more than welcome to make me an offer for it.

Thanks in advance.
 
I'll do a RR day with you, always wanted to... :thumb:
 
"Of course, if anyone is completely besotted with the device on the day, you are more than welcome to make me an offer for it.
"

The wife's hairdrier chucked it last night....so I will start an internet bid at 10p :puh:
 
One issue that has not been covered in this extensive dabate is the sound - imagine an electric fan / hair-dryer buzzing away every second that your car is switched on - plus all the street-cred minus points of the horrible noise - I bet the eager shav who invests in one of these things will soon decide to lose it -

LOJO
 
Stuart said:
I'll do a RR day with you, always wanted to... :thumb:

Stuart, what is your engine spec? 3.6 std?

Where are you in UK? (I am based in Herts)

I do need a full front and rear (quad rollers) rolling road though (C4) - anyone suggest my local?
 
GT4 said:
Stuart said:
I'll do a RR day with you, always wanted to... :thumb:

Stuart, what is your engine spec? 3.6 std?

Where are you in UK? (I am based in Herts)

I do need a full front and rear (quad rollers) rolling road though (C4) - anyone suggest my local?

3.6 and in West London, Herts area is easy to get to. I'd like to see how my modest engine mods have affected the over all graph without remap?
 
OK, so not strictly interested in the assisted hair dryer?
 

New Threads

Forum statistics

Threads
124,354
Messages
1,439,458
Members
48,711
Latest member
Silage
Back
Top