TLV996c4s

Hi all, I have a 2004 996c4s with x51. At the moment I've been doing little things such as building a set of custom RSR headers/exhaust and GIAC tune. Since I got the car I had this idea that I wanted to keep it n/a but make between 500-600hp (reliably) which I think might be doable since my car sits above 400 as it is with the current mods. want to do something a little different with it than just super charging it or turboing it (maybe I might get the itch down the road who knows) but the sound of an n/a Porsche motor is one of the best sounding cars IMO. Now here is the dilemma, I know there are a few options for going bigger in cylinder size and I'm aware of my options with LN and what not but can it still be done for the same-ish cost as a normal 3.6 motor bump and if so any recommendations would be greatly appreciated.

zbomb

You’re 5-600WHP NA reliably is the most ludicrous statement I have read in a long time.

Congrats.

Quadcammer

I'd sure be interested to hear how you gained 55bhp out of an x51 996.

As to making 500bhp or roughly 420rwhp, you're gonna need the gnarliest 4.0 out there to get close. 600bhp....forget it, not happening.

hatchetf15

OP - Is your hp figure from a real dyno? Never heard of a 3.6 M96 with X51 runners, tune and 93 octane get more than 360 crank hp. Best M96/M97 builders on the planet only get 3.6L numbers reliably to 370 crank hp; and above 400 (to max of 460ish) at the flywheel with 4.0-4.3 liter bores, massive replacement of internals, porting and exhaust pulse tuning, so I would like to know how you’re getting the ponies.

You want to do an LS swap to get your desired hp/tq.

TLV996c4s

600 isn't realistic but it would be fun to see how high i can get it so that is just a range not an exact, but where i sit now which is in fact above 400, which i am mildly shocked at as well, but where i stand now seeing where im at with what minimal i have done i don't think touching 500 would be unreasonable. its pretty amazing where it is not going to lie, when the vales open up it almost feels like a low boost turbo set up as it stands. it cost money to get something that strong but i know people/have friends that work with this kind of stuff all time time so i can get it done it's just a matter of what everyone else though. bigger radiators is a 100% must and should be happening soon once i put the gt3 throttle body and ipd plenum in as well. if a 3.6L rsr can make 400 as is, a 4.0L with built internals and proper cooling should do the job so i should rephrase, and good suggestions anyone might have would be great and i appreciate the responses so far!

hatchetf15

OP - Where’s the data? For a 3.6 liter M96 w/ X51? Not a Mezger 3.6, an M96. Different beast, that Mezger 3.6.

TLV996c4s

don't we all want a Mezger lol, but the est is from the shop i use which i also cross referenced with fabspeed, it make's either 398-401 depending on perfect temperature outside when it gets cold up here which it is a good bit of the time, in the next 2 weeks i want to do a solid few dyno runs once i put the rest of the stuff i have on and after i get my ims fixed because i got a garage princess before i bought it about a year and change ago. on the x51 note though there is a ton of tuning potential with the variance since a good bit is electronic and if my exhaust scavenging calculations are about right then that should be a very healthy 3.6L
GIAC tune- with no modifications besides ECU flash its 10hp which i have a very free flowing exhaust so logically it would be more, lets go on the low side and say it gave me 15 and its GIAC so i dont really need to justify that lol
IPD+GT3 throttle body- that's 28hp right there and that's fabspeed certified as well with their testing/dyno gatherings
RSR headers/exhaust- 12-13hp which brings me up to that number
and no cats as well, i found an emissions place to get me though so i can put all competition pieces and just put some 90 degree cats/spacers

TLV996c4s

Back to my main question besides the hp figures: is it feasible to have a car with x51 and make it a 4.0L? will that interfere at all or would it be done the same as a non-x51 car?

AnthonyGS

100 hp/liter is a very efficient internal combustion engine. Beating that significantly requires forced induction or all out racing engines. All out racing engines make crappy street engines.

If you think 500 hp from 4.0L naturally aspirated will cost anything reasonable or be fun to drive, you will be very disappointed.

TLV996c4s

okay so you think it's not worth it to try and get the most out of it and whatever the 4.0 get me leave it as is?

Quadcammer

yes thats feasible.

no your car doesn't make over 400bhp. Just added up quoted gains on parts is not how it works. Bet your car dynos at max 300whp

TLV996c4s

thank you for the clarification but I'm genuinely curious how you came to that number if stock x51 makes 345? keeping in mind that Porsche rates their cars conservatively

Quadcammer

from what i've seen, porsche did not rate m96 cars conservatively...at least those in the 996.

I'd say your car probably makes, generously, 370 crank hp (which is what porsche rates it at). When you consider your drive train losses, on a an AWD car, you'd be looking at 20% ish. So, if you do the matter, you end up around 296rwhp. I rounded to 300.

TLV996c4s

whenever it get to the dyno ill see whatever it makes and ill let everyone know but i probably have just been putting the numbers together wrong the whole time in which case thank you for correcting me, didn't mean to start a hp uproar/sorry for the ignorance per se. Pretty new actually being in the car scene so trial by fire i guess lol.

just happy to have an answer about whether or not x51 is conducive to adding a 4.0L

Bash Hat

That’s not how it works. That’s not how any of this works.