Porsche 996 Fast Road / Track Car - Oversize Build

I'm currently running in my CSR Evo rebuild and waiting for the dyno sheet.
Will report if and when i have numbers.

From discussions with everyone on the subject (ok not everyone.. but Hartech, Autofarm and RPM Technik), my guess is more than peak BHP you will have gained a lot of torq lower in the rev range. I'm currently on the first 200 miles so keeping throttle input to very little but it certainly feels like there is a lot more at low RPM.

Dammit said:

What's interesting is that you've made an additional 50 bhp from 300cc in capacity, the X51 intake and the X51 exhaust manifold - plus some benefit from the light port and polish.

That's despite running the same cams as the 3.2 litre Boxster - with cams optimised for the additional half litre of displacement I suspect you'd make a lot more.

Do you mind if I ask where in the rev range you made the most power and torque?

Click to expand...

Not at all, given your knowledge on this feel free to comment.

Peak BHP @6700

Peak Torque @ 4900

I will post the curve

I looked at and wanted Cam's as this would elevate me to full X51 spec, but again, and this is common theme, little available with even less feedback.

Schrick do a set, which I was sorely tempted by, however the only feedback I found was negative from the perspective that a lot work is required to set them up.

https://www.bar-tek-tuning.com/porsche-sportnockenwellen-280-schrick

I also touched base with Flat Six Innovations, Jake Raby, in the US, they do Cams, but only as a part of their engine builds, he did however confirm that unless set up correctly they would take as oppose to add.

The X51 cams require matching longer valves, amongst a host of other stuff, all of which was expensive and in the end due to the lack of information, and the fact that everything was becoming trial and error, my enthusiasm dipped as I wanted the car back so as not to miss the trackday season.

Thanks - very interesting.

This is from the brochure for the 996, and is entertainingly vague:



It's showing peak power at 6,800 rpm and peak torque at 4,600, so your peak power comes earlier but your torque is later than the stock 3.4, although I'm sure you're making more torque by 4,600 than the stock engine does.

Sounds like a great set up. Something I would also like to do with mine at some point if I keep it for a long time.

It would be good to see the graphs and how they differed from before to after. Also good to hear about mods to the engine and how they do affect the car, it seems induction and exhaust is quite key on these engines.

Great thread.

From reading your various posts, I knew you were building something special so it's great to read about it.

Not sure if you've seen this already, but a chap on PH with a 3.4 had his dyno'd at SRR recently and it made 275bhp.

Graph on page 9:
https://www.pistonheads.com/gassing/topic.asp?h=0&f=47&t=1695879&i=160

RE weight, interesting to read that you have removed 105kg already but 'still' at 1290kg. There's a chap on PH with a 996.2 GT3 (air con, comfy seats, no cage) and had his weighted at Centre Gravity and it came in at 1380kg (with some fuel, unknown how much), so it matched Porsche's published figure. I have not weighed mine so I was quite pleased to learn that. Would love to remove 50kg from mine but there's not much to go on without spending £££.

Anyway, your car's specs sound superb; I would love to experience it, particularly the JRZ suspensions, first hand if there's an opportunity. :wink: 👍

Dammit: - It makes cira 285 ft/lbs at 4600, its at 250ft/lbs by 2500, and doesn't drop below this until 6750.


Demon: - Going by your signature we are indeed treading similar pathes. – When I actually think about the resonator, it makes sense, removing it does not increase airflow to the engine, but it does increase the noise, how does it do this, by upsetting the airflow. – You could also question why Porsche would add the resonator if it doesn't contribute anything.


Jcharalambides: - What is the spec on your engine build? 3.9?


Infra : - The 3.6 comes with less problematic heads out of the boxes and is probably a better place to start than the 3.4, however, and this is personal, I prefer the look of the 996.1 aero which I was set on when I started, being honest I didn't initially plan on the engine work!


Y2K : – Cheers for the dyno link, this further confirms to me that 275ish, are where the 3.4's are, interestingly the torque seems low, circa 225 ft/lb - Would be interesting to see what the 3.6 M96 is making.

I was surprised at the weight on mine, and was hoping to be closer to 1250kgs particularly based on the numbers that are banded around the internet, unfortunately not.

I know I can lose more, the standard wheels are heavy, I could save 20kg's there as an easy win, I have previously had a set of Oz alleggerita, actually had two, but I wanted to stick with the standard look so moved them both on.

I do however have a set of 996 Cup Magnesium E88's that I will eventually get around to fitting, the saving will be less than the Oz's, circa 15kg, but I can live with that as I think the wheels rock , out and out weight saving is not the ultimate goal.

Tyres are also a place to save that is often over looked, with most concentrating on the wheels. When the car was weighted it was running Yoko AD08R, which are a great tyre, but heavy, a 225 is heavier than a 245 Cup 2, the E88's will run with Cup2's, which are also a quicker tyre.

Lightweight battery, Odessey etc is an easy, cheap, big win on weight, however can be problematic if you dont keep it constantly on a ctech. - Li could be the perfect solution but I have no experience.

The JRZ's are superb, however, they are an out and out motorsport damper and as such are designed to run with high spring rates on race cars. - As the spring rates are high you also need to run lots of compression and rebound to ensure the damper is damping and your not just sat on the spring, I made this mistake at Thruxton when I had initially fitted them and it led to losing the rear coming out of Village!

All of this means a stiff ride, perfectly compliant on smooth surfaces, but rutted B roads, not so much!

Being transparent the whole suspension setup and geometry does not really lend itself particularly well to large swaths of British roads!

Spring rates for context.,

996 GT3 runs R: 370 F:200 - Revised on the 996.2 GT3 to R: 542lbs F:228

Cup Car: R:1484 F:1370

I run, R:950 F:800 (Main springs, both with 150 tenders)

My fronts are probably a little too stiff, noticeable on track when braking hard on bumpy surfaces, brings in the ABS when the tyres still have traction, most annoying, I can counter via the rebound damping, to an extent, however I think a little softer would dial out a little more understeer and help with the braking.

Your welcome to try it, do you track your car? trackday meet?

Pictures, may be of interest to some.,

Engine case being machined for the additional crank shaft bearing. – The crank has a long overhang the additional bearing provides the crank extra support.

To further aid the crank as oppose to the dual mass flywheel, circa 13kg's, being hung off it, a Lightweight flywheel was fitted, circa 6Kg's.

This should make for longevity and reliability. – This is the first engine, outside of a few race cars, that Hartech have fitted this to.

That said when the crank was removed the original bearings etc were in good shape and that was without the extra bearing and a dual mass flywheel, the car had covered 90k miles and several trackdays

Block

Thanks for the info RE suspensions. I'm a complete novice really so had mine set up by 9E. I had a play with bump and rebound and quite happy with it now, but second opinion always welcome so track meet sounds good.

I got Abingdon this Friday actually, then Oulton in September and Blyton Park in October. IIRC you're based at Surrey/Sussex? PM me if/when you're going to Thruxton / Castle Combe / Donington etc, I'll join you if my schedule allows.

Really interesting read, thanks Crash.

Honest data and feedback is very hard to come b on the internet, so all the more valuable when it's shared.

Nice one. Time to enjoy it now!

Fascinating thread, thanks for sharing.

I note you mentioned you'd found the 997s 3.8 plenum to be the optimum choice.
I'm curious to hear if you tried the 3.6 stock plenum & what the gains where with the 3.8 plenum, as this would be a relatively cheap mod for the rest of us.
Also would you happen to know the difference in dimensions between the 3.6 & 3.8 plenums? & can you share the part number you used?

For completeness I'll add the graph from the original Porsche hardback catalogue for the stock 3.6 as a comparison to the one Dammit shared for the stock 3.4.

I had all the details written out and for some reason I lost the screen. Typical
98 c2 3.4
Hh removal with piper x foam filter
Denso iridium plugs
Surefire coil packs
Unknown ss exhausts, manifolds and cats
97 Ron as in Northern Ireland.

@crash7 - my rebuild did not entail a displacement increase. Mods include different cams, ported and flowed heads and valve seats, new liners, pistons etc.

I am still waiting for the Dyno sheet for which the tuner is taking his sweet time to send over to RPM Technik... It will be interesting to see the numbers on this. Ultimately if they are good, you could combine these mods with an upgrade to 3.9 or something.

It's great that you got to try things on-and-off while on the dyno. For some reason there is very little actual science backing a lot of the tuning mods!

Schrick cams?

I appreciate it's not quite comparing apples with apples, but I have the original Cayman "RS" development car that Autofarm produced about 10 years ago.

It started life as a regular 987.1 S ie the M97 3.4L lump. Autofarm subjected this to one of their 3.7L Silsleeve engine conversions. In addition to many of the same bits and pieces that Hartech do as standard, Autofarm also fitted the Shrick cams, IPD plenum GT3 throttle body and a custom carbonfibre airbox. It also has stainless decat headers and Miltek back section (also decat).

The engine was dyno-mapped by the now departed Bob Watson and showed 367bhp, backed up by a dyno print from a different dyno a couple of years later showing a very similar number.

The power delivery is very linear with strong low-down torque. Getting the thing to cool properly has been the major challenge, but I think that is as much to do with the mid-engined lay out as the engine itself. I have now also gone down the line of fitting TTP Oilsafer pumps on both banks of heads together with an additional external oilcooler, deep baffled sump and larger 997 water/oil heat exchanger, low temp therm, lightweight clutch and flywheel and under drive pulley.

I think there is still more on the table with a bit more dyno time. Parr had it on their dyno relatively recently and commented that the map was fairly basic and could be improved.

Clearly comparisons with a Hartech M96 3.7 are not entirely fair, but what is interesting is that even with many of the bolt-on "performance" mods eg plenum, throttle body and airbox, which the OP found to be power-reducing, there is still a material improvement in power output over the Hartech M96, which presumably must come largely down to the cams and exhaust ???