kc996

SUPERCHARGER!!!!

nycebo

Look guys, let me talk about something for which I have great experience...motorcycles. Back in 1994, I bought a new Honda CBR600F2. On the dyno, it ran 79 ponies at the rear wheel which wasn't too bad for back then (there wasn't ram air induction on the bike so no worry about fanning it). On the road, it pulled nicely. Given that modding bikes is a very practice, I replaced the air filter with a K&N, swapped the exhaust canister and headers, and rejetted the bike (I imagine similar to reprogramming a la GAIC). Same dyno and same conditions (it was just 1-2 hours later but still in the mid-afternoon...read, hot) revealed a new pony reading of 90. It's a 14% increase. And the torque curve was elevated across the entire rpm band. So pull and power. But forget about that: when I got the bike out on the road, it SCREAMED. I'm not kidding. I'm almost **** my pants at the difference. Perhaps it's because the new exhaust was 15 lbs lighter. Perhaps it's because it's carbuerated and the mods make a bigger difference. Perhaps it's because the moon was aligned with the planets. Who knows. All I can say is that I pulled away from everyone running stock bikes and kept close to my buddies Kawa ZX-7...which itself was kitted out. In terms of reliability, the bike is now 11 going on 12 years old and RUNS LIKE A CHAMP. I have NEVER had an engine problem (gotta love Honda). So clearly, the mods did not ruin the engine.

Now, back to Porsche. It's totally acceptable that emisisons requirements and noise restrictions in this country impact Porsche's ability to squeeze even more power from their engines than possible. It's totally acceptable that freer flow and a chip (or a rejetting in my bike's case) adjustment would make for at least more dynamic throttle reponse...combustion vehicles need air, right? So, I have NO DOUBT that mods increase performance to some degree. The question is what is that degree? On a 3.4L engine, going from 300 to say 325 is an 8% change. That's statistically significant at greater than 5% (or 2 standard deviations from mean). Is it worth the $5000? Who cares? It depends on your budget. But if stock was so terrific, then why do racers swap this stuff out on the track? One might ask, "What about real world driveability?" More horsepower doesn't always mean less torque. Driveability should be improved if mods are done properly. Again, is it noticeable? Perhaps to some. But definitely to me. Go and drag a NEUSPEED modded VW and tell me if mods don't work. Go and drag a Dinan Bimmer and tell me mods don't work. People who argue that they don't just had bad experiences, IMHO. Let's put it this way, a good freer flowing exhaust "ain't gonna" make your car slower. NO WAY. And besides, you get that AWESOME sound to distinguish yourself from a Camry.

And last, just ask yourself this in our free market economy: if mods didn't work, why is there the aftermarket at all? It's not inconceivable that private enterprise couldn't come up with a better part than Porsche? Hell, half of you guys drive SSKs from B&M or Schnell and Porsche started copying them as a result because they knew it was a GREAT product. This is how markets work. If mods didn't work, why the hell does Porsche keep updating their cars? You should all be driving 70s era Pcars.

Anyway, all of you stock lovers out there stick with stock. I'm going the mod route. You'll recognize my car from the back with the little red hand sticker waving good-bye.

Rant over.

peachboy

If just for the better sound just do it...in term of HP gains can't say I noticed anything. IT does seem like the car revs better.

TT Surgeon

Tim, there are many factors in calculating the VE, atm is one of them, as a ballpark range I like to look at the figure of 1hp/cubic inch displacement as a benchmark, or 100hp/L at sea level with a std ambient T of 68 degrees . At this level you are approaching 100% VE, however there are many other factors involved, that's not to say that a 3.4 will max out at 340hp. In fact it is possible that a NA 3.4 can make way more than 340HP, but difficult.The Porsche engineers quoted a figure of 80%VE for the 3.6, not 88% as one might infer from the 100hp/L benchmark. So, there are error and correction factors that need to be factored in as well( ambient T, ATM,etc). All I'm trying to point out, from an engineering perspective, is that the m96 is already cranking pretty good, and it's gonna take a lot of work to get significant hp gains, short of forced induction on the intake/exhaust cycle. Also two stroke and 4 stroke engines use different formulas in calculating VE.
What do you think, I spent all my premed time dissecting frogs?

Dale Gribble

just a follow up to this.. Civic B16 and B18 engines put out more than 100hp/L from the factory even (Type R versions)...does that mean they're running at 120% VE or whatver? how is this possible

TT Surgeon

Ed, I kinda agree with you, mods do work, they do increase hp/tq by increasing the engines VE. The point is, the Porsche motor is already cranking pretty good, and it's gonna take a lot to get that last 10%VE or 25hp. Unlike a SBC that's way behind the 8 ball already with a VE in the 40's, it's easy to crank it up with minimal mods, you have a lot more room to play... more room on the starling curve so to speak.
I think the main reason so many guys are selling aftermarket parts is the we buy them, based on overexpectations or past successes with other engines. I love mods, just realistic as to what to expect.
PSE is a great example, porsche quotes zero hp gain, and they are right. It is just a bypassed 5/8" pipe btwn the inlet/outlet, solely for the purpose of making noise. There is nothing free flowing or less restrictive about it, unlike aftermarket alternatives, which do increase hp( and decrease TQ) by decreasing backpressure and allowing free flow increasing the VE of the cylinders/compression chamber.

TT Surgeon

Not familiar with those motors, are they forced induction? But, yes it IS possible to make over 100%VE, remember 100%VE and 100hp/L are not the same thing, just a rough mathmatical approximation. Ambient T, temp of combustion, ATM, fuel , etc all play a role.

1999Porsche911

I have to disagree with you Surgeon. The PSE does reduce backpressure, especially in the 3.4 engine. All you have to do is watch your fuel trims adjust when you switch from quiet to open and the difference in flow is immediate and quite large.

Dale Gribble

B16 and B18 are naturally aspirated from the factory.

snaproll

Originally Posted by kc996
I think the "over 25 HP" refers to the hp at the engine and the 16.6 refers to what is put down at the wheel. I think it's something like you lose 12% to 15% going from the engine to what is put down at the wheel.

OK, but how do you reconcile the drop from "over 25 HP" to 16.6, which is about 33%?

snaproll

And last, just ask yourself this in our free market economy: if mods didn't work, why is there the aftermarket at all? It's not inconceivable that private enterprise couldn't come up with a better part than Porsche? Hell, half of you guys drive SSKs from B&M or Schnell and Porsche started copying them as a result because they knew it was a GREAT product. This is how markets work. If mods didn't work, why the hell does Porsche keep updating their cars? You should all be driving 70s era Pcars.


If Porsche could get 25 HP from an intake and a chip, how come they change out all the hardware with the Carrera Powerkit to get 25 HP?

TT Surgeon

Those stupid Germans, you mean all they had to do was slap on an air cleaner to get 25hp?
Seriously, porsche is working under the confines of a stock ecu and tough emissions standards, the aftermarket is not. I doubt the 25hp figure from evo, I'd believe 10.

nycebo

Surgeon, come on. I'm not just talking about the air filter but the whole air package (chip and exhaust too). Emissions standards are a hassle, and developing different motors for different regions with different specifications is probably not cost efficient. Freer flowing air, and potentially free flowing un-combusted fuel in the exhaust, are a concern. But again, if exhausts didn't work, then why do professional teams use them on the track?

As to 25bhp, maybe it is just 10 as you say...or even nothing...but I was just going with the average number that people seem to throw around here. The only reason I would really be modding anyhow is for improved throttle response and sound (oh that sound). But, to some people every little extra bit of HP helps, so all the power to them. And, there is just too much anecdotal evidence of people hitting much higher speeds at the track on the straights after the car was simply modded.

So, who knows? Maybe it is a charade...and frankly, do any of us really and regularly push these cars on the public roads to top end? But for some reason, mods keep a lot of people happy. I say stick with it if that's your schtick.

TT Surgeon

Ed, I'm not disagreeing with you at all. I think most mods work great, esp exhaust. I just don't buy any tuners dyno numbers, let a true independent /unbiased shop dyno cars before and after some of these mods, that would be more believable.

kc996

Snaproll, good question.

This is directly from the EVO website:
Stock Baseline: Peak Wheel Power: 248.8 RWHP (300 HP at the flywheel = 17% drivetrain loss)
EVO Stage 1: Peak Wheel Power: 272.4 RWHP (328 HP at the flywheel)
Max Wheel Power Gain: 26 HP @ 7000 RPM's

As you can see it doesn't exactly add up; 272.4-248.8= 23.6 not 26HP at the wheel and supposedly there is a 28HP difference at the flywheel which doesn't account for the 17% drivetrain loss from flywheel to rear wheel.

Anyway I don't think there is an agency that regulates this kind of stuff so as mentioned earlier maybe it's more like 10HP gains vs. 23-28HP.

FUN WITH MODS!!!
K