M96 big bore engine modifications, what works, what doesn't?

I'm setting up this thread to allow M96 big bore owners compare modifications to their engines as some seem to fit M97 engine parts, aftermarket exhausts or 997S parts but there are still big gains with a standard engine apart from the bigger bore so it would be interesting to see? Please post up what you have done and your BHP and torque figures, most people are having their cars mapped on the same rolling road at Chipwizards so there is a good base for comparison. Currently mine needs to go back for a remap as my first session wasn't a success due to an under delivering fuel pump and a cam actuator not working, but it is booked back in for the 3rd of September and I will update my power figure after that session. My current mods include a mildly ported head, a standard exhaust manifold but with the inner welds for the flange that meets the engine smoothed flat. I also have the 997 injectors fitted but that is all at the moment. It still pulled 326bhp even with the faults mentioned above.

Great idea. My engine is a standard 3.9. The only change from the standard setup is a set of Fabspeed Maxflo silencers/mufflers. Holy crap - I just checked the Fabspeed website - $,1895 for the pair! One of the POs must have been minted...Apparently, they add 12whp and 10flbs of torque... The manifolds and CATs are OEM. I have 2 Hartech 3.9 stickers on the side windows... I think that gives about 5whp... 351bhp @ 6846 rpm 332.4 lbft @ 4029 rpm

:thumbs: I can't remember if you have said before that you've got larger injectors or not?

I think each sticker is 5whp?

Hartech 3.9 - 997 airbox with BMC filter in it and silicon pipe (resonator delete), TopGear exhaust manifolds and Dansk (quiet version) silencers. That was how it was chipped by Wayne at ChipWizard right after the rebuild in March 2020. 366bhp at 6572rpm and 324 lb ft at 4535rpm

996 injectors

the difference in profile is interesting - you have more Bhp and I have more torque

Peak readings only show a snap shot. (The torque peak might arrive at a different point in the rev range depending on exhaust design (pulse / scavenging effects) or cylinder head efficiency etc.) Area under the entire torque or power curve would be a better comparison, but you'd need to overlay the graphs with each other. Obviously a bit difficult.... Great idea to see what works from existing models (manufacturer designed and tested) rather than expensive aftermarket stuff. Each new part would maybe need another remap to extract the optimum though?

That compares very well to the 997 3.8 engine in 'standard tune'.... Impressive.

thats me! 997 3.8 injectors, I also have a evo ms intake and sports exhausts of some make. mine is 377bhp and 332lbft MisterCorn is working on tappet jackets to alter them and get some cams and he is hoping to see about 400hp

What is the advantage of the 3.8 injectors? Do they displace a greater volume than the standard 996?

on some cars the standard ones can't supply enough fuel, mine were about maxed out and possibly dangerous towards detonating the new engine

The spec for flow on the injectors is for both 996 and 997 at 3 bar, flowing 187 for the 996 ones and 237 for the 997's, the 3.9 may run a little lean on the 996 injectors but without mapping the 997 injectors may run too rich. In advance of fitting the 997 injectors to my engine Chipwizards set my ECU to where they should be before I ran the engine in as it may have washed the bores of oil and put fuel in the oil?

So this is what my trip to Surrey Rolling Road revealled on Saturday.... This was with the exhaust (designtek switchable) on loud. On quiet it was 20bhp down on that figure so less than a standard 3.6! Noticeable dip in the curve towards the top end also. I am pretty disappointed and have emailed Hartech this morning to see if they might be able to shed some light on why the car is so down on power compared to what it should be. A potential source of the issue could be the exhaust so I contacted about 6 of the popular exhaust makers to see if they could provide me with dyno charts for proof of their claimed power gains. Only Cargraphic came back to me, all the others couldn't or wouldn't provide any proof.

Hi Mark, yes those figures are not what we would expect. Although all dyno tests should be comparisons on the same dyno - we have found most add-ons reduce performance (although might be louder) and this has been verified on posts on here but - having said that - I suspect there is something wrong with the car generally (fuel pump perhaps etc) or the exhaust (that was not designed for that capacity) is not working properly with it. It may also have developed cam timing errors etc. It looks as if it is possibly winding back the ignition timing to compensate for knock or picking up knock detection when it is not there?. The torque curve should be very different. Grant will be contacting you to suggest you bring the car back to us for further investigation. I would also like to look into the specification from some time ago now when we return to work tomorrow. Hopefully we can sort it out. Baz