maybe its all in my head that Rennsport's chip remap made my car more "perky" but I don't think so. I am not an engineer and am pretty clueless about the math/physics of how our cars run. What I do know is that after I got my chip back and put it into my car, it ran more powerfully between 3500 and 6000 rpm. How much more I am not sure as I didn't time it but it there was certainly a "seat of the pants" difference that I could discern.

 

The examples below are purely hypothetical.

Tom, let's look at the following. You have a car with 27" monster wheels with very tall tires. You push the throttle, you get certain responce. Now you put the same car on 13" wheels with 45 ratio tires. You push the throttle, you get different responce. What happen? Did the power change? Of course not.

So, it is possible to change the throttle responce (let's be frank and call it acceleration, because that's exactly what you're describing, although throttle responce is a slightly different thing) with having idential power output.

Now, if we look at a toque curve and it has a single huge peak at 5700 rpm, what happens at 3K rpm? We have no idea. By reprogramming the chip we can, however, make it have a flat curve from 2K to 6K (again, hypothetically). We can loose 100 lb-ft of torque at 5700 rpm, but gain an ability to actually drive the car on teh street and have a better "throttle responce" (there's that term again).

At least that's the way I see things from here.

 

I see that I've used almost the same analogy as Jean

 

"Now, if we look at a toque curve and it has a single huge peak at 5700 rpm, what happens at 3K rpm? We have no idea. By reprogramming the chip we can, however, make it have a flat curve from 2K to 6K (again, hypothetically). We can loose 100 lb-ft of torque at 5700 rpm, but gain an ability to actually drive the car on teh street and have a better "throttle responce" (there's that term again)." - nile13 -

And Porsche didn't think of this, but some "super tuner" did? Please!

 

One more time from the top. Porsche made _the same bloody chip_ for about 30,000 993s worldwide. For conuntries with different emissions, different octane gas availability, different driving conditions, different speed limits, different fuel price, different average fuel consumption laws. If you do not understand the word "custom", I can, as a public service, point you to its definition in a dictionary.

Porsche made a number of other things. One of them is an engine for 1984 Seat Ibiza. If they are all brilliant engineers and everything they do is perfect, why do you think the '84 Carrera did not use the same engine? I am certain that you've heard of "different horses for different courses".

You still have not answered my simple question for some reson either.

 

Kinda related. MY95 993's I recently learned have three different ECU iterations or rev levels. What is the difference amongst these? Just curious..

 

Hi Chris:

Some have Drive-Block and some do not; it was an option in '95.

 

"Kinda related. MY95 993's I recently learned have three different ECU iterations or rev levels. What is the difference amongst these? Just curious.." - chris walrod -

As was the case with the 964 ECMs, the variation in the '95 993s' ECMs' is just a function
of different EPROM chips. The basic '95 993 ECMs are all the same.

 

And why are there different EPROM chips?

 

Since it seems somewhat unaddressed, I'll put my $.02 in (but I'd like some change back ) about throttle response.

Imagine an engine that at 25% throttle and 2000 rpm produces 100ft-lbs of torque and at 35% throttle and 2000 rpm produces 105 ft-lbs of torque. When you are in the car and go from 25% throttle at 2000 rpm to 35% throttle (before the rpm has changed) you would feel the extra 5 ft-lbs of torque (or maybe you wouldn’t) as an extra push into the seat. Now imagine the same engine (with a chip, say) that at 25% throttle and 2000 rpm produces 100ft-lbs of torque and at 35% throttle and 2000 rpm produces 110 ft-lbs of torque. The difference in torque output (between stock and chipped) will be felt as better throttle response (the reversed situation applies to lifting off of the throttle). Now imagine that for every throttle setting and rpm, the chipped engine produces a “bit” more torque that the stock setup and that any dips in the torque over the rpm range can be made less severe and perhaps the peaks can be boosted a bit as well. Again, this will be felt as better throttle response. Only two methods are available to the chip maker to achieve these effects, ignition timing (and fuel used) and air/fuel ratio, and the optimum settings (for given conditions) can only be found through testing. As with most activities, some people are better at testing than others and results certainly do vary, but the point is that differences are achievable.

Discussions of max torque were not addressed here because such subtle tuning changes (for those that could provide the above results) are not the dominant factors in max torque at wide open throttle (using ignition timing and air/fuel ratio to avoid detonation is). This should be obvious since the above discussion focused on throttle response, and at wide open throttle the, throttle setting is not changing (except for the intial transition).

 

I've had a chip in my 95 '91 octane 993 for the past 5yrs (tried two different GIAC versions from two suppliers) and never felt any difference. Sorry, but that's the truth. Funny thing is, I'm glad I have the chip, but never could tell the difference...maybe 15hp (??) is unoticable to the untrained gluteous...

 

Try running some 100 octane fuel and see if there is a difference. It could be that the chips are trying to advance the timing, but the knock sensors are killing the party.