3.2 intake manifold rework?

[dw1]

First, I'm new to the 911, having my '87 3.2 for only a few months. I am, however, an experienced tuner so I'm already seriously considering performance enhancements.

Knowing that on most older naturally aspirated cars the manifolds can be a weak point for good & balanced flow, is a good idea or even possible to rework/replace the intake manifold on a 3.2?

Or is the better just to focus on a performance mass airflow sensor & bigger throttle body?

BTW, a chip by Mr. Wong and better exhaust should be assumed as near-term mods. Overall, my target hp is in the 280 - 320 range.

Speaking of exhaust: Any special concerns/precautions regarding cutting into the rear panel for the second exhaust outlet because it is galvanized metal? Any special rust preventative that should be used after cutting?

------------------------------------------------------------------------------
One final question at the risk of rousing the ire of some: Is it a really bad idea to modify a very clean 3.2 coupe with less than 70k miles? My thought was that these are not rare cars and will never be all that valuable as collector cars until a long, long time from now. Besides, most modifications are reversible.

But I came across a car VERY similar to mine on the web for a LOT more than I paid and it got me thinking.... Well, my 911's headliner isn't as clean, my car's dash has a crack, and I still have the OEM Blaupunkt am/fm/casette, but besides that it looks the same. Am I right or wrong in thinking the price for this car is nuts?

details: '88 911, 46k miles, 32k$, Westtown Imported Cars (www.westtownimportedcars.com)
---------------------------------------------------------------------------------

As a newbie, I realize I'm obligate to post some pics - ok soon, but after the wash & wax, and after I finish cleaning up the engine compartment.

[stlrj]

Better to put your focus on your ignition and existing air flow meter before moving to more time consuming and expensive mods of little more than placebo value.

[dw1]

Sorry - under the assumed near-term mods I should have listed an MSD unit, type 6AL or 6A.

[don911]

Your expectation of HP increase is not realistic for a NA 3.2L. If you maximize your intake, exhaust and chip, 250ish FWHP is about the most you can expect.

I think my 3.2L is pretty much maximized (MAF, custom SW chip, cat bypass) and my best dyno was 213hp at the wheels, 250ish FWHP.

[Rot 911]

Building on what Don said extrude honing the intake should be the last of a long line of mods. Air intake is not the weak link on the 3.2. Exhaust is. Even then you can plan on spending $100-$200 per horsepower gained.

You are correct in thinking the Carreras will never be desireable collector's cars. Make your mods and have fun driving the car.

[Wavey]

98mm (3.4 litre) pistons & cylinders, 964 cams, extrude-honed intake manifolds, SSI's and a sport muffler, and a good performance chip (ie Steve Wong), can give you +/- 270 HP and lots of torque. (Source: Steve Wiener).

[Bobboloo]

To re-iterate what others are saying. Porsche didn't leave much on the table with either the intake plenum or the ports.

Areas to look for gains are first off the exhaust. Bare minimum would be a cat by-pass but if you can go with headers with larger pipes you'll get more from intake mods in the form of either 20/21 cams or 964 sport cams and throttle body enlargement. Some people go for a MAP sensor to replace the MAF sensor to get some extra HP as well.

Then there is always displacement increases which can be anywhere from 3.4 up to 3.7 just by increasing the bore.

I think it's pretty well accepted that extrude honing is the least fiscally responsible mods out there. Small gains for large cash.

It's a good idea however when you have the intake off to check for any inconsistencies from the molding process. I had one runner on my Carrera intake that had a little lump inside of it near the port. I just ground it to look like the others.

[Carrera3.5L]

Originally Posted by dw1

Overall, my target hp is in the 280 - 320 range.

Your horsepower goal (the low side) is realistic retaining Motronic and on pump gas for somewhere between $10K-$12K depending on the choice of and quality of products being used and if you are performing your own labor.

3.2L before with minor bolt-on mods and 3.2L to 3.5L twin-plug (still w/ Motronic) after:



In order to get near your goal, you will need the following at a minimum assuming you will retain the original Motronic:

98mm (3.4L) or 100mm (3.5L SS) Pistons/Cylinders (retain stock 74.4 stroke) or
98mm (3.5L LS) or 100mm (3.6L) Pistons/Cylinders w/ 76.4mm stroke

Twin-Ignition (easiest using Andial splitter w/ 964 or 993 distributor)
Twin-Plug Heads (use either 12mm or 14mm lower plug depending on CR requirements). Minor porting/polishing if head machinist/builder skillful

964, 20/21 or 993SS camshaft profile (depending on smog requirements)

Extrude Hone or Cut/Polish/Weld stock plenums or use late 964 plastic plenums

Overbore stock throttle body (about 3mm max with stock unit)

Modify stock airbox by cutting lid or using cone filter or replacing with MAF unit

Remove stock exhaust in favor of larger headers (1 5/8" OD for street use under 7,000 rpm) or like headers with heat capability (mild steel or stainless construction radically alters price)

Good final muffler (I like the Monty or Dansk sport units personally but a plethora of options to choose from. Some increase power, some don't)

Custom Steve Wong chip for modifications performed (ideally a live remap)

The rest is up to the talents of the builder to make it all work. There are engine builders and there are engine assemblers, they are not the same and the results can be significantly different both in power extracted and long-term reliability.



If you want to go into greater detail on some of the options, feel free to send me an email to ralph@porschemotorsport.com. Don't worry, not looking to build your motor (the only air-cooled motors we do are the odd 917, 935/962 or 993 RSR) but can give you some objective advice if interested. BTDT.

Ralph

[JeremyD]

what ralph says - even if you do your own work, open your wallet and say ahhh

[dw1]

Ralph,

Thanks a LOT for the list.

Thanks also for the dyno chart & the photo. I've seen that photo on the 911chips.com site - A VERY nice clean install.

To modify the old saying, it seems that there is no substitute for cubic centimeters.

Very good point about the mapping. I've seen proper ecu mapping make a measurable difference on the dyno.

Yes, I am trying to stay NA, as I've had my fill of repairing poorly installed aftermarket turbos, blowers, & nos - and the fragmented piston crowns, blown heads, block-piercing rods, etc., etc. that often go with them.

Protomotive and others are out there if I change my mind and I'm sure the experts here can make a reliable, streetable 3.2 stage I+ with an add-on intercooled turbo. But I think the $$$ to do that properly on a 911 motor would start to make it attractive to carefully evaluate other options like a larger-displacement engine.

So maybe a reliable, bulletproof 250 - 275 is a better target than a high-$ turbo retrofit or a budget-limited turbo hand grenade.

But I am still researching and keeping an open mind...

BTW, I'm a pretty good wrench with a well-equipped shop and some background as a machinist, but I've worked with some very good engine builders, and I'm definitely more in the '"engine assembler" class.

p.s.
I know "how fast do you want to go = how much you want to spend". IMHO it's a lot better to build hp than spending it on new golf clubs, membership fees & green fees. It's a Porsche, so I know the $$ can be significant. But it's a Porsche and worth it.

[Eagledriver]

The intake is the major problem with getting more power out of a 3.2. That is why our rules require use of a stock intake to keep the power in line with our 2.7 and 3.0 engines. The stock air flow meter is the choke point.

-Andy

[JeremyD]

How much power do you want to get?

ITB's or carbs will allow you more cam flexability - and more power - no matter what the displacement