Cable to E-Gas? Boosting my 3.8 M96? Crono is back for more! (Pic heavy)

[Crono0001]

Oh man... It's been a long time since I've been around here. I am so happy this forum is still alive. I finally have time (and funds) to revisit my old beloved Boxster, and I of course have so many questions again since I forgot all there was to know about these cars from back in the day.

A Brief Introduction: (Skip to TLDR if you don't care)
I don't know if the guys who were frequenting the board when I was frequenting the board are still around (Johnny Danger, Particlewave, Bruce Wayne?), but I bought my 2.5L base Boxster in 2013.

My first car during college. Loved it. Took it everywhere. Constantly broke down on me. AZ heat killed it so many times. Drove it many years without AC as a poor college student. Spent every day on these forums.



Graduated, started making money, started doing stupid things to it. Some aesthetic stuff here and there. Took a 3.2 out of a Boxster S, re-sleeved it to 3.8, and stuck it in my car around 2016.









The engine has been a blast to drive with. I've put about 80k miles on it since the swap back in 2016. I've since gone on to own some other fun cars and projects. Changed professions a few times. Bought a house. Got married.



Meanwhile the Boxster has kind of moved from home to home and was somewhat being neglected
it constantly found itself in the BACK of pictures of my other cars, despite it starting life as the first.



But no more! The Boxster is ready to make a comeback!!





TLDR:
I own a 99 Porsche Boxster that has an upgraded engine. The M96 motor has been re-sleeved to 3.8L, and is currently outputting 240 whp on 11:1 compression with a tune on the OEM ECU. The throttle body has not been modified, as it is the older cable throttle generation and not drive-by-wire.

I want more power, but am coming to terms that my little M96 is likely at its limit.

Ideally, I want to hit 600 whp, but I know that is very ambitious. In all honesty, I would be happy with 450 whp - enough to keep up with some of the newer 911s.

I figure boost is pretty much out of the question. I've asked all kinds of experts who have worked on cars much more expensive than what I could afford, and they all pretty much said the same thing - the M96 is not an engine built for forced induction. Even if I were to lower the compression, the heads evidently lift at even modest boost.

I understand this is an unusual path for such an outdated and not very popular platform (the 986), but this car has extreme sentimental value to me and is the only reason I am pursuing spending money on it. I understand that the money is likely better spent on a better car, but I am here because getting my beloved Boxster up to snuff is the goal.



Boxster S Upgrade, any merit?:
I know a big limitation of the 99 was the outdated cable throttle system, which 2000 Boxsters and newer did away with and replaced with the E-gas system. I am actually within reach of an IMS failed 2000 Boxster S, and was wondering if there was any merit in obtaining it? I already have the Boxster S front brakes (I could get the rear brakes and uprights to complete the set).

I guess the 6 speed would probably be an upgrade from my stock 5 speed.

But aside from that, is it worth transferring the whole chassis harness from the Boxster S to my Boxster just to get the new electronics (alternatively, take my modifications and block and put them in the blown Boxster S) - assuming I upgrade the ECU and get a tune. Would there be more support for me to upgrade my heads and throttle body?




If boost is out of the question for the M96, what about going really nuts.
I don't even know what's out there anymore. I know Renegade did an LS swap kit for the >2000 Boxster S's. I know someone somewhere did a Subaru EJ25 swap. 3.4 from 996 is really common, but I wanted something 450whp to 550whp range, if that's even possible.

Thoughts? Insults? Have at it! I miss you guys!

[Radman]

This would likely get more traffic in the main chat thread vs technical.

But, Flat6(Jake Raby) might be worth a call. My understanding is moving to the e-gas is not simple or cheap. You can upgrade a 3.4 from a 996 to at least a 3.8 and possibly a 4.0. There are people on the forums that have them. They are all apparently sworn to secrecy about how much power they put out but they seem very pleased with the results.

Like you I have a 99 Boxster. It happens to have been made the month and year my wife and I got married so now she won't let me upgrade from it lol! Admittedly, I also love the car too much to sell it. So I've been looking at the same options. Right now, my goal is a flat 6 innovations upgrade to a 996 3.4 motor. But I'm probably at least 5 years out. Buying son's truck some time in the next few months. Then saving for a Bronco. Then the engine for the Boxster. So, maybe only 3-4 years.

F6I isn't the only place doing rebuilds(Vision I think does?) and if you're comfortable doing the work you can likely do it yourself. LNEngineering sells rebuild kits for all different years including upping the displacement. If I retire early, maybe that's the route I'll go lol!

[The Radium King]

if you've brought it out to 3.8 and it is still making small power then it can't move enough air - exhaust or intake are restricting it. not sure what you re-sleeved, as i don' think you can take a 2.5 (which is what was around in 1999) out to 3.8? regardless, some chinese headers, drill and tap for an intake from a 996, and a tune, and you should make more power. perhaps not a lot as (noted above) jake from flat 6 says you get into diminishing returns with displacement increases on these engines. can't recall why; perhaps head design (combustion).

[Crono0001]

Hey guys, thanks for the reply!

So some updated info,

The block was from a 3.2S that has been re-sleeved to 3.8L
The heads are modified 3.4 996 heads
Compression is 11:1 with 5 cut angle pistons
The intake manifold and throttle body is unmodified from the 2.5L (!!)
The intake tube is an EVOMS aftermarket intake
The headers are from Fabspeed

Running a bench flash on the older DME.

Finding someone who will tune this has been a nightmare, but I think I may have a lead.
My first order of business is to upgrade the intake manifold and throttle body, probably from a 3.4 996, and then re-tune.

I'm still considering boost. I know M96 engines hate boost, but if I can make an extra 50 whp, I would be happy - even if I have to run e85.

[The Radium King]

full intake assembly from a 1999 3.4 and you can keep your cable throttle. may have some interference with the chassis due to intake height, but massaging and perhaps small spacers on the engine mount to lower the motor should set you up. can also get more clearance from a 987 engine cover.

since you have 3.4 heads already no need to drill/tap for the intake, but i think you'll need to run the 3.4 fuel rails as well (mounting is different) which will require tie-in to your existing fuel system.

think about maf and air filter as well, which will drive what you need for a tune. ditto injectors - later 996 runs larger units. a lots of threads here about 987 airbox, maf tube diameter, etc.

make sure your fabspeed headers are not for a 2.5, otherwise not doing yourself any favours.

you can boost these things, just don't get crazy unless you want to drop the compression. perhaps see what you think about your 3.8 once you fix the breathing issues before boosting. although 2.5 intake would actually be better in a boosted application ...

[Crono0001]

Originally Posted by The Radium King

you can boost these things, just don't get crazy unless you want to drop the compression. perhaps see what you think about your 3.8 once you fix the breathing issues before boosting. although 2.5 intake would actually be better in a boosted application ...

Can you explain your last point? Is it because there's only one crossflow tube?

[The Radium King]

because with boosting you put a lot of work into compressing the air. sending it into a high-flow intake just allows it to re-expand and undoes some of the work you did. also no need for a resonance tube in a boosted application as you are not trying to facilitate airflow at atmospheric pressure, just jam it in at 5 psi or so.

[Crono0001]

This is sounding positive. No 3.4 intake manifold means no need to modify the engine cover.

[The Radium King]

well, you should be able to fit a low-boost turbo or supercharger in there (lots have). check out aerocharger if they are still around - self-lubricating so no need to mess with oil lines and scavenge pumps, adjustable vane tech and adjustable boost.

the big packaging issue is fitting an intercooler - air/air or air/water?