Louie928

Earnest,
I'm not sure of the total cause for different tires giving different results, but I'd say your assessment is likely true. The Hoosiers aren't made to compromise for ride quality or tread noise so have different sidewall stiffness and no doubt tread compound. The tires don't heat to more than "warm to the touch" on the dyno even after 3 repeated runs. They are absorbing power though. It's a condition of dumping power into them for a few seconds and then nothing for a while. The tire difference was noticable on my car in 5th and above 150 mph. Likely not a big difference if speeds were kept below 140 mph.

Ken was here doing some dyno checks and he brought a set of wheels/tires that was different weight. The different weight of wheels/tires didn't make a power difference.

ew928

I'd thought a lighter wheel/tire combo would help the car spin up the Dyno roller a little easier and net a slightly higher reading.
Another myth shot down.

cobalt

Not sure what other GTS's run but dynos can vary and others had mentioned how it is strapped down could make a difference. That is why I like dynapacs myself.

My Stock GTS a few weeks back did 295.39 rwhp and 320.31 torque with a high smoothing of 5 so we may have missed the peaks. This was at 95 degrees in a poorly ventilated room and my car is due for its 60k tune up. I would expect to see a bit more power with fresh plugs, cables, rotor distributor cap etc etc.

Just reread what you said. How could you hit 180 mph if your doing a 4th gear pull? The test needs to be closest to 1:1 and that would be 4th not 5th gear correct?

heinrich

Keith's starting number is MASSIVE, a GTS is supposed to pull 300 or so to the rear wheels. So to START with 313 ... that is significant.

cobalt

Not so sure I agree. Based on factory numbers should be 293.25 average +/- a little for stock for a 5 speed and 276 for an auto. these cars run 18 and 20% drivetrain loss for manual and auto. I got that info from a 20 year factory trained mechanic who specialized in 928's and 944's

heinrich

That means Keith STARTED with 20hp to the ground higher than stock, Anthony ...

AO

Maybe Keith found the magnets under his gas pedal?

cobalt

That is what he is claiming although what were the conditions and type of dyno used? Were all corrections correct? Basically the most important thing is to use the same dyno and corrections and see what gains are achieved. It would appear the X pipe does perform although I am not so sure how much you would feel the gains. I have nearly 450 hp in my turbo and it doesn't feel that much faster than it did at 360 although it is faster. Although my friends turbo with over 600 hp is noticeably faster feeling.

I think you might find the biggest improvement with the X pipe is throttle response.

928ntslow

Anthony, the results recorded were a 4th gear run at baseline, though the one with the X was a 5th gear run.. I did say we ran a few 5th gear runs that were just about the same but better numbers...not by much. Not sure why Louie plugged in the 4th gear run.

The test was done on Louie's dyno both times...within 2 weeks of each other.

Since there is no wind resistance or similar weight issues when running in real time, a 5th gear run will reach 180+ at 6800 rpms or there abouts. I try pull off the throttle at 6500, but as it sweeps, I am sure I have seen the needle at 6800.

Not attempting to pull the wool over anyones eyes here. Louie pretty much confirmed his dyno is comparable to others out there. The numbers speak for themselves whether you would like to believe it or not.

I feel the difference with the X in the lower mid range, though the graph shows the increase in power from 3K on up.

I have no answers as to why some GTS's perform better than others. I would expect it is a combination of things. One thing that I have been screaming about for a long time is the single prong cold copper plugs, but most think the multi prong plugs are the way to go. I have always disagreed and never had pinging either....which is a whole 'nother issue for many out there. Maybe the rich mixture is helping...or not. It's just a good running motor I guess.

drnick

cobalt, i managed 333.5 rwhp with headers, custom exhaust and elgin cams. the dyno machine ajusted and called it 410 at the crank, the car screams like a demon and goes properly quick. i think that as long as youve got the LH and EZK doing what they should a GTS engine, is a GTS engine, from porsche.

cobalt

I agree the GTS is not a slow car. Nicely set up from the factory. Although I don't think thy made a slow 928 they all seem to move along. I agree you can tell by the charts they are very accurate systems when working properly. Unlike my turbo that can get different readings depending on how you approach it. Although the turbo just kicks the butt of the GTS like nothing. With nearly 460 #ft of torque it can slam you into the seat harder than most cars and gains ground as fast as most new high performance cars today with more power.

Not so sure what they were using but 410 at the crank from 333.5 at the wheels seams wrong. I would think the number should be closer to 392 BHP, Doesn't matter it is still more than enough power and IMO reducing weight is more critical to these cars than adding power.

ew928

The Magnets were on the fuel lines and the air tubes.





More power and fuel efficiency with the Fuel Magnetizer.
Guess one can sell anything without any basis on science.


Keith has a big motor.

Louie928

928 transmissions whether 5 spd or auto have the top gear straight through 1:1 ratio).

cobalt

Not saying anyone was pulling the wool LOL. Nor am I contesting your findings Just that this can be somewhat subjective and the important thing is as you say that the unit does gain power over stock.

I am using the stock multi electode plug. No pinging IMO near perfect charts. I also said my car was past due for a tune up so after it is properly tuned it may show more HP. Porsche always had a min number they would set, some cars do run better than others especially from that era.

I am definitely interested in your results, I am one that can never have too much power so long as it doesn't destroy the driveability of the car. I appreciate your opinion on the mid range increase and feel.

Really? I will need to look that up. Not what I was told and rare for a Porsche. So if my numbers are in 4th when they should have been taken in 5th I need to go back and try again but we tested several cars that day and everyone agreed 4th was the correct gear for manual box.

Louie928

Keith,
I'm sure both of the runs on the chart you have were 5th gear runs. I'll check the records to be sure. I probably shouldn't have brought up the 4th gear example, or should have explained it better. I wanted to illustrate that there are many variables, and which gear you use makes a difference. There can be no set value to try to equate rear wheel hp to crankshaft hp. The driveline/tire loss % changes with speed, and it is different depending on the transmission gear used. Dynos like the Dynapak can come closer because they bolt directly to the rear wheel hub and don't use the tire. That's one variable those dynos get around. However, they are limited in rotational speed and you can't use 5th gear. You'll have more loss due to using 4th so will typically show less rwhp. Back to comparing apples and Amsoil.