Lorenfb

The 993 engines have enough problems which occur because of many factors,
e.g. heat which leads to valve guide failures. So, I'm surprised many of you
would "force" the issue by adding a performance chip which basically just
advances the timing causing more heat and possible engine damage when
the knock sensors are disabled by the chip. Furthermore, you then have to
also deal with potential emission failures and CELs.

Stick with adding some carbon fiber accessories or a new shift ****.

Have Fun
Loren
'88 3.2

Steve Weiner-Rennsport Systems

Loren:

Couple of points:

1) A GOOD chip does NOT trigger knock sensors above background level. I've monitored this for years with the Bosch KTS-300 and PST-2 both on the engine dyno and in-car. Fuel is the variable and any properly made chip is mapped for the fuel in use.

2) Twin-plug engines run very well up to 26 deg total at WOT and operating within known ignition map values does NOT increase cylinder head temps. Once again, cylinder head thermocouples bear this out under testing and the engine dyno surely stresses an engine far more than any chassis dyno will.

3) A GOOD chip does not affect emissions compliance and doesn't trigger CEL's. I'll tell you Sir, OBD-II is tougher to comply with than most state's smog laws. That's why more and more local governments now simply look for logged faults and no more sniff test.

I would caution you not to make broad generalizations,.... Just like people, everything you see isn't all the same.

FlyYellow

Chris,

you really think the difference in a RS pulley is the same as having the A/C on or off. - that is a huge difference (IMHO).

I completely agree the reduced speed with the RS setup - that makes a lot of sense.

Cheers,
Boris

Lorenfb

The use of knock sensors allows the Porsche ignition advance to operate
at max without pinging. That's the purpose of utilizing knock sensors.
A performance chip which advances the timing only results in the knock sensors
"pulling" the timing back sooner.

With more HP comes more heat loss resulting in more engine stress. That's a basic
fact of thermodynamics. That's one of the reasons why Porsche has watering
cooling on the 996. There's just a limit to how far you can push an air cooled
engine.

Furthermore, to add more fuel just results in the OBDII DME system using the
TRA (short term AFR correction) & FRA (long term AFR correction) to re-adjust
for any additional fuel which modifies AFR=14.7. So remapping the DME has
little benefit, as can be seen by the many comparative dynos run which indicate
insignificant differences between stock and chipped engines, especially in the
typical driving ranges (3000 to 5000 RPMs).

I'll be more direct in this post; Performance Chips are real joke for late model
Porsches! If you want a real performance increase for a track use, install a
Motec or some other system and forget about street use.

Have Fun
Loren
'88 3.2

graham_mitchell

Lorenfb, isn't the same amount of fuel burned and therefore approximately the same amount of heat released, regardless of timing?

Speedraser

Boris,

Could you tell us what the difference between totally stock and "best" is?

FlyYellow

i can't because i didn't take the car back to stock (too much work). i couldn't delete things like the rs pulley & mufflers. but pure stock + rs pulley & mufflers was 251hp.

add the giac chip and it went to 253 hp.


please also note that i have a '95 car (no varioram). hope that helps.

Tech-Law

I'm assuming you're also losing voltage then?

DC from Cape Cod

You mentioned 4 items.

Airbox was stock - no change here.
GIAC chip - adds 2 HP.
Muffler - You didn;t get 15 HP from chopping baffles out - did you?
Pulleys - some one idnicated max HP gain of 1 HP.

I'd like to know where YOU think the 17 HP gain came from...because I can't tell from the data presented in this thread.

Lorenfb

Advancing the timing causes additional combustion pressures which results
in more heat being developed within the cylinders & heads. That's why the
ignition timing can affect how hot an engine with run. More power (HP) results
from more energy (heat) being released from the fuel.

Have Fun
Loren
'88 3.2

JohnM

Not quite. When fuel quality is adequate to ensure no knock the ECU uses the map value of ignition advance, which already has some margin for poor fuel quality. You do not want to be operating at the knock threshold in everyday running and for the sake of longevity factory mappings are conservative. If the fuel is really poor then the onset of knock triggers phased retard. There is margin in the factory ignition mapping to add some advance without knock occurring and this does increase power, it is not a lot but in the context of Porsche engine tuning it is cheap horsepower. There is also scope for modifying the ignition and fuelling maps lower down the rev range and at full and part throttle to even out the torque curve a little and improve transient response, but it seems few of the aftermarket remappers take the time to do this - I can certainly believe Steve is one of those few, but I have no personal experience of his products so can only speculate.

Speedraser

Sounds like some of the mods Boris tried resulted in lower power than stock. My impression is that he didn't gain 19 hp over stock, but rather from worst combination to best.

DC from Cape Cod

Good point.

I guess we just don't have enough data to draw any conclusions at all...at least as far as individual upgrades are concerned.

Lorenfb

Sounds like this thread will "converge" on the saying "There's no
free ride in life."

Have Fun
Loren
'88 3.2 No Chip

FlyYellow

todd, you are correct. some of the mods i did detracted from stock. i only tried testing a variety of mods that were questionable. this include three different air intake systems and three different chips. my conclusions from the testings is:

1. the factory air intake is very very good and nothing (that i tested) could improve upon it.

2. if you believe me above - you'll certainly agree that the air intake is critical and some variations make huge h.p. changes. so there is possible room for improvement here, but none of the systems i tried were able to improve upon the factory design. but it is possible that someone might be able to.

3. chip improvement is nominal at best. i do like the smoothened torque curve, but i'm not sure it is worth the expense - tough one in my mind.

Cheers,
boris