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That's good question. Do they mean mid '88 MY piston style change is same as GT piston or is there separate high CR piston style for them. Nowdays PET lists just one style pistons for all engines but '89 GT document says there is difference between S4 and GT.
I've got an 87 and an 89 S4 - I'll order a new USB endoscope thingy and see if I can take some pics of the pistons in each. My old USB camera died - possibly from being cooked in hot Audi engine
I've made an 'overlay' mask of my GT m/fold runner exits, with the intention of overlaying it on the image of S4 runner exits, the idea being to show the dimensional differences between the two.
Was a bit of a fiddle between two image editors and a couple of curves look a bit scruffy but not enough to affect the idea (Too much coffee while using mouse). Also found a better S4 manifold underside image to work from.
They're posted below (large); I've had trouble scaling them without incurring just enough jpg conversion distortion to make comparisons difficult. Perhaps someone with better s/ware will have more sucess.
Upfix -- I can't see from the photos any differences in the trumpet ends.
If someone has unported 4R, unported 2R, and factory ported GT 2R at hand, I'd love to see or read what the differences are at the trumpet end.
Got back home. I am looking (rather, feeling) the intake runners, the intake port end. This is a 2R manifold. They leave a fair bit to be desired from the air flow perspective. I can see why they hand ported those for the early GT's.
Forgot about the balancer, good point. From 90 GT #278:
Interesting, there is a number but different. Ours is '90 #475. There is no Porsche part# anywhere. Current PET crosses it to the generic orange damper.
The intake differences are interesting. I remember a few years ago people were just buying 87+ intakes from ebay or were swapping them with others that were already powder coated to reduce down time of their car during the intake refresh. So some GTS end up with S4 intake and I guess some S4 end up with GTS intake. Don't know how much of a difference it makes but hopefully the owners were aware of the differences...
I have a set of 3R heads that came from an 89 S4. I'm assuming S4s in 89 also came with 3R heads. The intake ports are slightly ported in the beginning as if to match them with the intake. I have pictures in the thread below. You can see the slight port work on pictures 1,2,7, and 14.
since there are some recent post about interest in GT models, wonder if someone can interpret what this means?
found this under additional features from this GT engine specs post: https://rennlist.com/how-tos/a/porsc...e-specs-376864
thinking this was a mistake?
"Another interesting feature that was added for the 1994 GTS was a dynamic kick-down attachment to the engine loom. It can be activated whenever the car is traveling faster than 34 MPH and the throttle valve is more than 24 inches open by rapidly pressing down on the accelerator. It makes the car become much more responsive in its shifting. It can also easily be deactivated by releasing the accelerator or slowing down to where the conditions aren't met."
since there are some recent post about interest in GT models, wonder if someone can interpret what this means?
found this under additional features from this GT engine specs post: https://rennlist.com/how-tos/a/porsc...e-specs-376864
thinking this was a mistake?
"Another interesting feature that was added for the 1994 GTS was a dynamic kick-down attachment to the engine loom. It can be activated whenever the car is traveling faster than 34 MPH and the throttle valve is more than 24 inches open by rapidly pressing down on the accelerator. It makes the car become much more responsive in its shifting. It can also easily be deactivated by releasing the accelerator or slowing down to where the conditions aren't met."
It was obviously placed there in error. It refers to ECU programming for the 94-95 GTS with an automatic transmission. And, I am not too sure about the throttle valve ever being able to open more than 24 inches...
It was obviously placed there in error. It refers to ECU programming for the 94-95 GTS with an automatic transmission. And, I am not too sure about the throttle valve ever being able to open more than 24 inches...
AFAIK ECU is same in '94-95 GTS as in '92-93 MY cars. Difference which makes dynamic kickdown work is kickdown relay. It gets extra signal wire from throttle body sensor and uses it to determine how quickly throttle was pressed. If speed is fast enough relay will send kickdown signal to gearbox even if kickdown switch is not yet activated meaning throttle isn't fully pressed in.
Here are the parts you need to modify a 92/93 auto to dynamic kick down.
I have Dynamic Kick down on my 93 and makes the awesome Rogerbox even better if that is possible.
Kick Down Relay 87 to 95 was 928 618 108 00 but SS to 928 618 108 01
TPS Throttle Position Sensor 94 to 95 - 928 606 157 01
Amp Bosch Connector - 6 Way MAF Connector
Contact Spring 0.75 to 1.5 - 999 652 456 22
Fitting Piece 6.3/0.5 - 1.0 - 999 652 451 22
Flat Receptacle 6.3 x 1.5 w/o Clip - 999 652 106 02
The TPS has become very expensive to change. Owners have made the mod to earlier 87+ cars.
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Does it have the "Do It Yourself" manual transmission, or the superior "Fully Equipped by Porsche" Automatic Transmission? George Layton March 2014
928 Owners are ".....a secret sect of quietly assured Porsche pragmatists who in near anonymity appreciate the prodigious, easy going prowess of the 928."
GT engine number K00147 has 2R heads and 2R intake
GT engine number K00215 has 3R heads and 2R intake (cast week 48/88)
The heads and intake on both engines have very visible signs of machining by hand.
And, I can add that both K00147 and K00215 have orange vibration dampers.
02-01-2015, 04:10 AM
George Layton March 2014