996 4s - diy 3.9 x51, reworked heads, schrick etc

[GMG]

...I think that 996s with the sill cover trims are most likely / almost inevitably going to show rust issues...the covers will trap moisture and debris that sit invisibly slowing oxidizing the sills !

 

[GMG]

...I think that 996s with the sill cover trims are most likely / almost inevitably going to show rust issues...the covers will trap moisture and debris that sit invisibly slowing oxidizing the sills !

 

[Tim_s]

Small update from me, I've mainly been tuning it. I've installed an lc2 wideband using a cheap voltmeter on the dash to monitor AFR. See pics. I hooked up the controller to the post cat o2 sensor relay on the shelf on the rear deck and ran the cable to the sensor down through the handily positioned grommet there. Unfortunately it's the second wideband I'm running now, the used AEM I installed originally was reading very lean which I only realised after wasting time incorrectly enriching my map. I also discovered through fitting the wideband sensors in the place of the post cat sensors that the x51 euro 3 software I'm running has the post cat o2 sensors disabled in the flash - it didn't throw a fault code so I investigated and that's when I found them switched off in the parameters. Probably not a bad thing if I leave the wideband in permanently.
Tuning is going well, have good AFRs on WOT, does go a bit leaner than I'd like between 3-4k rpm where it's got a massive hit of torque, I've tried a few things to bring it down but not there yet - lamfa had no impact, I'm not using BTS (it's set at factory 860C egr), tried giving a bit more maf load via KFKHFM, nothing's really got it. I've prepped a map with the VE tables lightly tweaked at 3k rpm and a FKKVS adjustment to add a few % to injector pw on high pws at 3-3,5k but not tried it yet, really I need to do a bit more logging to see what's going on, but it's not really a huge deal and might not be far from optimum AFR anyway, hard to say - but I'm running a slightly richer base fuelling than I'd like to compensate so it would be good to flatten the AFR on WOT a bit. And I'm sure it's good news as it's indicative of it being really strong there vs a standard engine. Part load under 2k I've not quite got sorted, I'm running tvub from a 997s map but I'm not 100%, but I expect if I stop messing about flashing/resetting it all the time and run it for a while and observe fuel trims I could probably dial part load in a bit more, that or it would probably sort itself out.
And I've been having fun with my flasher occasionally failing mid flash and leaving the DME in flash mode requiring a recovery - less scary after I knew I was able to recover it but it's a shame as I'd not want it to happen when on the rollers.
Short version of all of this is I might have to eat my words earlier in this thread around using the factory ecu - it's taking ages to get it mapped. I hoped I'd just adjust base fuelling for the injectors and it would basically be good to go.
It's nearly run in now in any case so will change the oil in a bit and be able to use all the revs and get it rolling roaded.
The new batch of dye also arrived so I finished the seats, not before I'd trashed a few bits of interior trim getting them in and out. I've had to order another door handle and redye one of the side panels on the centre tunnel. I also tried a slightly more matt top coat, I'm undecided on what looks better but its staying now regardless!

 

[IMI A]

For mapping you really would do well to reach out to Ken @ 9e and or Iain @ Litchfield.

For rolling road once you're happy with the mapping try Litchfield or RE Performance. Both have really good Maha dynos.

Actually you should try Rick at Unicorn Motor Developments too. He has a dyno too but it won't be accurate as the latest Maha. Rick will still give you a very accurate figure though and can custom tune your car himself - nice to deal with the tuner directly.

I'd only do this once you're sure all the hardware is working as it should be :wink:

 

[Tim_s]

Thanks for that, Litchfield and RE aren't too far from me and worth a chat to see what they can do when I'm ready.

 

[little fella]

Hi
Tim

Sent you a PM last week not sure if your inbox is full??

Carl

 

[Tim_s]

About time I updated this, been a bit busy with one thing or another but the 996 is ticking along nicely. This will probably be a bit of a mega update so will break it down into a few parts
Engine/tuning:
Had a few issues with obd flashing and bricking dmes, but have learnt both how to copy the data on to a new DME (so now have 2 working DMEs with my vehicle data) as well as how to bench flash them back into life.

I had the car rolling roaded today locally on dimsport rollers making 370bhp @ 7150rpm and a nice strong torque curve throughout, but the dyno wasn't really any good for porsches/rear engined cars. No fan over the back meant it was just heat soaking so I didn't do many runs, and the logging was bit limited despite me paying extra for it (no IAT, AFR was clearly not giving a reading until higher rpms) so I didn't want to tweak anything based on their readings. Having said all that, their wideband suggests that there's probably a bit more in there by richening up a smidge further and I'm running factory spark and cam timing, so there's probably a bit more in there through that. All in all a satisfactory result and I'm really happy that as expected there's a really strong torque curve and nice smooth delivery, but I feel there may be some more to come. The engine's only on 1k miles so am not going crazy. V happy that it was also running very clean on the dyno.

Besides this, I've made a bunch of other dme changes including:
-removing secondary air pump - I've never really liked how crammed in it is with x51 and the 997.2 airbox, so I decided it would make sense to remove it and clean up the engine bay. I just capped off the valve and disconnected the vacuum actuator so the valve always stays shut. By some careful tweaks of the dme, it now passes readiness (that's to say if you run the secondary injection short test in piwis, it passes), has no fault codes or anything – basically the dme expects airflow out of the pump is 0. It's a good amount quieter on cold start, not to mention removing 1.6kg over the rear of the car and getting rid of the pipe.

-removing the rear o2 sensor heating diagnosis so that there's no fault codes for the fact that they're currently removed to allow for the wideband lambda, but left them operational so I can plug them back in if I so choose.

-altering some of the temp variables so that stage 1 fan kicks in at 95.75c rather than 97c and stage 2 full speed fan at 99c rather than 102c, same for engine compartment fan, and I've reduced the hysteresis from 3 to 2 degrees. I'm not a fan of running a LTT for many reasons (so don't!) but the fans never come on anyway, nonetheless thought this was a good bit of extra protection against running hot.

-7,4k rev limit – 997 x51 runs 7,450 and I've ARP hardware on the crankcases and rod bolts etc, but I've kept it down a bit. The car is still making near peak power at 7,4k so ideally it could be set higher but I just don't need it and will never use it and would rather protect the engine.


The only other thing to report is I've had a bit of a play with a 9x7 dme to see whether I could get that to work as the 996 dme is still a bit grumpy on part load in places with 997 injectors (I'm working on it!), but it won't handshake with the M534 and I can't find how to or anyone who can immo off it, so without going down the rabbit hole of changing clocks and M534 I think it's a no go.

 

[Tim_s]

Suspension:
I've been trying a few things over the past months to bring the nose down a bit and give me some rake back after removing a good amount of weight from the front. I didn't want to go coilovers as this is a road car and I like the compliant factory suspension. I've been considering changing to c2/gt3 or similar front hubs to suit it being rwd along which would allow me to have koni special active shocks on the front to match the rears (koni don't make c4 fronts), but in the meantime I've also been tweaking to see how I can get it to perform on the original 4wd hubs.
I initially tried some 996.1 c4 m030 springs, but these sat more or less the same as the origs (drove similarly too, poss a touch softer). Dia of spring was 14mm vs 14.5mm for the 4s springs.
Following this, I bought some eibach c2 springs, expecting they'd be different due to different top mount/bearing etc but wanting to see for myself and whether there are any avenues to explore. They're longer and different dia at the top, so parked that idea for now and I've settled on vogtland springs with the rear raised 12mm with additional washers under the spring to get some rake back. My thinking was I didn't want to go too drastic and I'd read that the vogtlands handled similar to factory but were just a bit lower. It sits well now, but I wonder if changing to the smaller rubber perches front and rear just to drop a couple of mm would give a better look, and the jury's out on whether I need quite as much spacer on the back.
Some other notes on this
-the vogtlands are nearly 3kg heavier in total than factory due to the design which has extra coils close together which are not 'active' when the car is sat. This is the same as H&R and other brands do which I'm guessing in effect gives you a tender and an active spring on a single coil and basically allows for a shorter active spring.
-The front vogtland coil is 13.5mm rather than 14.5mm on the factory 4s spring which is interesting but there appear to be fewer 'active' coils on the vogtland (i.e. it's less tightly wound) so it probably all balances out and is a similar stiffness. It feels much the same, perhaps a touch stiffer but really is a good drive on the road and I'm pretty happy.
-the ride height is conservative, they're not much lower than factory

I've also got some 14mm spacers on the way to try. They're 'VA' hubcentric spacers, I bought them as they're 7075-T6 so stronger than most and a hollowed design so lighter. I'll report back on how this goes.

Brakes
I've been toying with something lighter as there's ~45kg of brake disk stuck on the car if you consider all 4 corners, but not really found much info on what might work. Girodiscs are of course nice, but are expensive and no lighter despite a slightly larger diameter. I don't really want to go any larger, if anything I'd like to get the car lighter to make it stop better.

Exhaust
I'm very happy with the 997.1 cans I got that are basically new. They don't sound much different to the gundo hacked ones I used to have and the car has it's awesome growl back after the switch to the topgears. The clamps on the tailpipes had seen better days and the 997 boxes have a slightly narrower exit so I welded a reducer sleeve on to them. The main nag I have is that's still just over 16kg of exhaust hanging over the back axle and I'd love something lighter.

Other general weight saving
I've been considering what else I can do in terms of weight saving, but there's not really any low hanging fruit any more given that I want the car to remain road friendly and keep safety devices etc. Battery is an obvious place and I reckon if I were to concede and ditch the side airbags and code them out as well as remove the 6" speakers I could save nearly 10kg from the doors. Sunroof off with a new gen panel (although is a bit severe and I quite like the sunroof), revisiting wheels and seats are other options as well as considering a LW FW (but again I'm not sure I want one).

In any case the car has spent most of winter tucked up in the garage so looking forward to some more use as the weather picks up!

 

[coullstar]

I run the Vogtland springs on my C2 and really like them.

I reckon you would save a fair bit of noticeable weight through wheels and brakes.

 

[crash7]

Great work! - Keep the updates coming.

Regarding Giro Discs, they are bigger and lighter than the standard items, granted only 1Kg a corner, but lighter never the less :thumb:

 

[Tim_s]

We're not the best of friends at the moment, me and this car. A week or so ago it decided to drop its PAS fluid out from a transfer pipe on the rack, not long before I'd planned a trip to cornwall in it. Once under it, I could see that the return line from the rack had also been bodged and JB welded in. I proceeded to replace the transfer pipes without disturbing the pressure/return lines, this was an right pain. Took me 4 hours on the day before we set off. Bad times. I've bought a 30k 997.2 rack to fit to it at some point to give me the quicker variable ratio and fix it properly, I intend to join the 997 lines (supplied with the rack) to the 996 lines at the left hand side somewhere saving me having to buy new 996 lines (as they're definitely not coming out of the current rack!).
Also having a few small issues with mapping. I'd not really explored the rev limit prior to it not appearing to consistently hit 7,4k on the dyno where I'd set it to. This is annoying as with the cams and intake it loves to rev. For some reason I haven't fathomed, it's not following the nmax parameter on the dme. I've tried a few things (relatively blindly without an FR for this dme) such as changing the gear dependent limiter codewort, changing the P/N speed limit to max speed and seeing if that would work (it revs to the rev limit stationary but seemingly not when moving). That's about as far as I got, I managed to upset the ABS with some of the messing about so have had to change it back. Getting the accel/decel enrichment right on the 997 injectors still continues to baffle me too, I'm going to revert to a different EV14 bosch injector that has a closer flowrate to the originals I think - the 997s are nearly 30% larger, I've found an EV14 that is ~15% larger and they're only £140 odd for the set new. At the moment I've decreased enrichment quite a lot as getting rich spikes in 1st/2nd under 2k and tried switching on the transient injection adaptation which is by default switched off on the 996 but switched on on other cars like VAGs using similar DMEs. Not driven it enough yet to decide whether this is working or not, but I'm thinking I'm making life harder for myself with the 997 injectors and I don't need to.

It wasn't that great on the cornwall trip, I found the exhaust too noisy with the 200 cell cats on the hills on the A30, it's been a while since I'd done a long motorway journey in a 996 4s and forgot how much road noise there is, had to have the stereo cranked right up to listen to podcasts etc. and the accel enrichment was annoying me. That and worrying about it pissing out all of its PAS fluid. It didn't however miss a beat, the tailpipes were nice and clean after the near 350 mile trip, and enjoyed crossing paths with a white 996TT and 718 in convoy. The cobra seats were pretty comfortable (if firm) too, this is a bit of a result. Now at nearly 1500 miles on the engine.
So there it is, all this has had me having thoughts of packing it in and getting something newer and a better GT like a 991 even if I'd have to throw in a bunch of cash.

 

[Desert Dragon]

Switch as much as possible back to stock intake, throttle body etc. It will make your life much easier. I'd also personally use a 996 steering rack. Steering in a 996 nicer and more precise than a 997

 

[Tim_s]

Switch as much as possible back to stock intake, throttle body etc. It will make your life much easier. I'd also personally use a 996 steering rack. Steering in a 996 nicer and more precise than a 997

I'd sooner go another route that would potentially resolve my slight accel enrich troubles (standalone, 997 dme), but all that feels like mega overkill just because the accel enrich is a bit dippy and I wouldn't want to remove all the bits for it. The intake probably wouldn't fix the accel enrich anyway - it's just tuning for the larger injectors and as annoying as it is, it's part of the process, and to be perfect needs doing.
Thankfully it's only at low load low rpm transients (particularly very slight throttle inputs), and I am getting there, I just think I don't need to go so large on the injectors and going closer to factory would mean less to tweak. I'm a big fan of the 997.2 airbox and x51 intake so wouldn't want to take them off, think they're some of the best bits (and I wanted the larger TB as the 997 x51 and the 997.2 runs it and I need it with the 997.2 airbox).

Steering rack I'll find out soon enough I guess, the racks are the same design other than the variable rack and the 997 is the same rate at the centre just gets quicker (it's 2.6 turns rather than 3). I prefer the 997 steering line arrangement too. I'll still have the 996 rack so can choose, but would be surprised if I prefer the 996 one.

 

[The return of Marty Wild]

This is an almighty thread. Still making my way through but it has chimed with me.

Do you mind me asking how you communicate with your DMEs, and where you got the X51 map from please?

Reason I ask is I have recently done the 987 Airbox/IPD Plenum/997 TB mod to my 986. I saw in the States talk of flashing off the peg Porsche maps in, say a 987 or 996 map to get things a little closer to the new hardware. I read with interest your point of mapping in the bigger MAF housing. This before getting Wayne or another top specialist to custom map everything in.

Appreciate IPD plenums are a source of contention. Yet to decide if we're keeping it. Any wise words greatly appreciated, thanks!

 

[diceman]

Really loving this thread. You seem a similar tinkerer as me and I suspect chaging to a 991 would probably reuslt in boredom or entering into a similar tweaking loop to get a powerkit setup to work on a standard car?

I haven't seen anyone else actually mapping their own stock ECU on this forum, qudos indeed.

I'll PM if ok as I'd like to know more about what is required to access and read the various maps.