Rebuilding 3.2L for power - suggestions please

[tmsoko]

I am planning to rebuild my 3.2L engine and increase performance at the same time. I have several ideas, but have not settled on any one idea yet.

The engine I have suffered a spun rod bearing. A few months back, I got a good deal on a 3.6L C2 crank, so that will be mod #1. From there it gets less clear.

I have been thinking about larger cylinders with custom pistons from EBS. Last I remembered when I spoke with Don, he said I could trade in my P/C and get larger cylinders with custom pistons to any head / CR combination.

If I go custom pistons, I will go as high compression as possible with pump gas (10.5:1?). For this, I assume twin plug would be good idea.

I could run the twin plug with either 3.6L distributor or SDS or Electormotive management. Would my 3.2L heads be sufficient, or should I upgrade those as well?

Also, for the finer details, what case work would be recommended? Are Raceware / ARP bolts really necessary?

If anyone has taken on a similar project, let me know you combination and any recommendations you have. I would like to keep it in the $6-9K range, but will be doing all assembly and some block work myself.

Thanks!

[jyl]

I see where Andial sells Ps and Cs to give your 3.2 liter a 3.75 liter displacement. I know nothing about how well this works, but would be keen to have the only "Carrera 3.8" in the neighborhood.

[Wayne 962]

Hmmm, one thing that you want to be careful of if you're modifying a 3.2, is how high you run the compression, if you stick with the Motronic system. All other systems have a method to retard the timing if the engine begins to detonate - the Motronic system does not (short of programming and installing your own custom designed chip). So, if you raise the compression too much, you may be stuck with a detonating engine that will require you to:

- Run super-high octane gas (expensive)
- Replace the fuel injection with something with a programmable ignition (even more expensive).
- Tear down the engine to reduce compression (the most expensive).

Just some things to keep in mind while you're designing your engine...

-Wayne

[mm86911]

Wayne - any advice on maximum compression for Montronic ignition? Both with and without twin-plug?

[ttweed]

Doesn't the Euro Carrera have 10.3:1 compression with Motronics?

In regard to the original question, I have seen a killer engine built by Matt Lowrance of Sporthaus in Reno which started with a 3.2 base and used a 3.6 crank and P/Cs, Carillo rods, special cams and Haltech programmable fuel injection with MSD ignition, utilizing the 3.2 intake and heads w/ modifications (porting and polishing) and custom exhaust. This engine makes well over 300 very grunty HP. Don't know if it would fit your budget, though.

[89911]

We had engine work completed on my brothers 87 3.2. Aside from the durability improvements, what was done was: Upgraded valve springs, 964 crank, euro pistons, Extrudehone intakes, and numerous other items. Left the bottom half alone. Replaced all the valve guides (thats a given). Once we get it in, I'll try to get a dyno level.

[ChrisBennet]

Originally posted by ttweed
Doesn't the Euro Carrera have 10.3:1 compression with Motronics?

Take Porsche's compression ratios with a grain of salt.
The stated compression for the Euro 3.2 is 10.3:1. The stated compression for the US motor is 9.5:1. The "9.5:1" motor has a true (measured) compression ratio of 9.2:1. The 3.6 stated compression is 11.3:1 but it's true compression is only 10.4.
-Chris

[Wayne 962]

What compression you run really depends upon where you run it (gas availability), and what type of fuel you put into it. Twin-plugging will certainly help, but twin-plugging a stock 3.2 again, won't get you as much gains (hardly any) versus twin-plugging a motor with a custom engine management system. This is because with the twin plugging, you don't have to advance the timing as much. But the 3.2 won't know this, and will time the car like it's single plugged.

In general, I don't recommend hot-rodding anything on the 3.2 Motronic system unless you replace the system with a Tec-3 or Motec. There's just not much you can do.

Compression, you can probably safely go up to 9.8:1. You might get some pinging/detonation on bad California gas though...

-Wayne

[tmsoko]

I would be using 93 Octane and live in Michigan. I haven't heard too many problems with the fuel quality.

With the engine management, I did not realize the motronics did not have a knock sensor/correction system. I am somehwat familiar with the Electromotive systems, but am not familiar with the Motec systems. I know I looked into them about 5-6 years ago and the basic system was ~$5K by itself. What does a Motec system setup for a 911 cost these days?

Could I possibly convert to a 3.6 or 993 system, or would that be the same in terms of limitations?

Thanks for the input guys!

[Wayne 962]

You can't use a 3.6 system on a 3.2 engine - too many differences. The 3.6 engine indeed is equipped with a knock sensor, so it doesn't suffer from the same potential detonation problems...

The 3.2 Motronic system is an early, somewhat primative version of the Motronic system that doesn't have all the bells and whistles that the later versions have...

-Wayne

[ChrisBennet]

Originally posted by Wayne at Pelican Parts
What compression you run really depends upon where you run it (gas availability), and what type of fuel you put into it. Twin-plugging will certainly help, but twin-plugging a stock 3.2 again, won't get you as much gains (hardly any) versus twin-plugging a motor with a custom engine management system. This is because with the twin plugging, you don't have to advance the timing as much. But the 3.2 won't know this, and will time the car like it's single plugged.

In general, I don't recommend hot-rodding anything on the 3.2 Motronic system unless you replace the system with a Tec-3 or Motec. There's just not much you can do.

Compression, you can probably safely go up to 9.8:1. You might get some pinging/detonation on bad California gas though...

-Wayne

When you twin plug a 3.2 you have a custom chip made for it that changes the advance and fuel maps. Just running the stock advance is asking for trouble.
Whatever you do, the power gains will not be as impressive as the money spent IMO.
If you track the car I would change the rod bolts to ARP or Raceware. change the valve springs to some competition ones and replace the retainers and keepers. Doing these things will make the occasional missed shift an "oops" instead of a lot of bent valves.
-Chris
('86 911 w/3.4 twin plug 10.5:1CR JE pistons, 964 cams, AASCO valve springs, etc)

[cstreit]

Just my 2 cents here...

If you bump the compression, twin plugging is more important to help the proper burn on the higher octane fuel required and for the flame front to travel properly within the cylinder (as higher compression pistons often have a taller dome, not allowing the flame front to reach the edges of the cylinder opposite a single plug)

Personally I would not run a 10.5:1 engine on regular pump gas. It MAY work with one formulation, but a cheaper gas or oxygenized winter blend might induce detonation. 9.8:1 maybe... Plus, with ANY new combo I would check the compression ratio manually during the build to know exactly what you end up with...

Detonation is commonly caused by the fuel mixture pre-igniting due to the pressure of the higher compression, not because you don't have twin plug.

See http://www.rennsportsystems.com/2a.html

[mm86911]

Chris - very interested in your engine mods. Have made any dyno pulls for numbers yet?

[ChrisBennet]

Originally posted by cstreit
Just my 2 cents here...
Detonation is commonly caused by the fuel mixture pre-igniting due to the pressure of the higher compression, not because you don't have twin plug.

See http://www.rennsportsystems.com/2a.html

Chris,
That's not how I understand it. This is from Rennsport's web site:

The main problem in the 911 air-cooled engine is the spark plug position. Since the plug is offset to one side, there is a propensity for the piston dome to block the opposite side of the chamber at Top Dead Center. This creates that pocket of fuel and air that is shielded from the main flame front created by the spark plug. Detonation is the uncontrolled ignition of that pocket of fuel.

The 2nd plug produces a controlled ignition and allows or ameliorates the effects of higher compression or poor gas.
-Chris (the other Chris)

[A Quiet Boom]

Will someone here please tell my brother (tmsoko) that he NEEDs 3.6 heads so I can buy his 3.2 heads for my SC engine for cheap! Please! Please! Please!

Seriously though, unless you're going to run a big cam (you're not), race the car (you're not) or need that last ounce of HP (you don't) I would recommend against higher compression. The benefits just don't offset the startup or long term cost. That 3.6 will provide plenty of HP and torque to keep you happy until the Cobra project is done or you get a blower on that 5.0 Ranger.

[cstreit]

Chris,

You are right about twin plug helping THAT sort of detonation... I wasn't entirely correct.

So in addition to the above, the higher octane is less prone to detonation at higher compression ratio's (aka "dieseling").

I always forget about that one...

[ChrisBennet]

Originally posted by mm86911
Chris - very interested in your engine mods. Have made any dyno pulls for numbers yet?

No dyno pulls before blowing it up. It should be ready (again) this spring. See 3.2 to 3.4L twin plug conversion on my web site for more info.
-Chris

[jyl]

Here's the text from the Andial site about the 3.75L conversion I mentioned earlier. Drool, drool.

[pasted text follows]

ANDIAL ROAD AND RACING
SPECIAL ENGINE PROJECT – 3.7L FROM 3.2L CARRERA (1984-1989)

This conversion is based on the 3.8L RSR technology. The RSR has a 76.4mm stroke crankshaft and 102.0mm bore cylinders resulting in a displacement of exactly 3,743.8mm. The cylinder base sealing is done by the use of an O-ring imbedded in the crankcase bore. No copper gasket is used between cylinder and crankcase.

The 3.7L engine conversion for the 3.2L differs notably from the 3.8 RSR as follows:

The crank has a 74.4mm stroke instead of 76.4mm
The housing studs are closer spaced
The cylinder heads to cylinders use a different mating pattern
For cost reasons, ANDIAL decided to utilize the 74.4mm crankshaft. We are using the original RSR 102.0mm pistons with reduced compression. The shorter 74.4 mm stroke puts the piston 1.0mm below the desired T.D.C. (i.e. 76.4 – 74.4 = 2.0mm total difference or 1.0 mm per side). To compensate for this difference ANDIAL had Carrillo make an RSR connecting rod that is 1.0mm longer, placing the piston in the correct position.

A special cylinder was manufactured by Mahle. It has the correct cylinder stud spacing, the proper match for the cylinder heads and is 4.0 mm longer than standard. The cylinder is longer because the case is machined down 4.0mm to provide a solid footing for the larger cylinders. The case is also bored out to 107.0mm to accept the cylinders and an O-ring grove installed. ANDIAL provides this case machining service, or as an alternative, a good machine shop can do the modifications following our instructions.

The following is a list of the parts needed for the basic conversion with our recommended options:

BASIC CONVERSION

AND 103 981 16 102.
Piston and cylinders, complete
AND 103 020 37
Carrillo rods, special length
Crankcase machining to specs.
OPTION I – SPORT KIT

And 111 031 00 ,
Sport Muffler, DME-chip update
Extrudhone intake manifolds
OPTION II – TWIN PLUG IGNITION (strongly recommended)

AND 903 950 02
Signal Splitter
930 602 015 01
Dual distributor
AND 602 031 33
Complete 2nd Ignition wire kit
944 602 115 00
2nd Ignition coil
Machine 2nd plug hole in heads and valve covers
OPTION III – C2 CAMSHAFTS
AND 105 246 09/247 07 C2 camshafts (pair)

SUMMARY – THIS CONVERSION HAS PROVEN TO CREATE A VERY EXCITING, DRIVEABLE MOTOR, WITH TORQUE CHARACTERISTICS CLOSE TO THE NEW 993.

COMPARABLE STATS:

Model Vehicle Weight Horsepower Lbs./HP
1984 Carrera 3.7L Twin Plug 2,700 lbs. 260-265 10.2-10.4
1990 Carrera 2 3.6L Twin Plug 11.3:1 3,025 lbs. 250 12.1
1995 993 3.6L Twin Plug 11.3:1 3,015 lbs. 272 11.1
1996 993 3.6L Twin Plug 11.3:1 3,015 lbs. 285 10.6

[pasted text ends]

[RSupdate]

Wow...Drool-Drool is absolutely correct !!!!

That info is very well recieved by this reader I like the fact that Andial is about 15 minutes away..... This the way I'll most likely be going when the 'ol trusty 3.2 finally gives out.....

Thanks for that info John.

[tmsoko]

How much does this Andial stuff cost? I checked out the website, but no prices. I guess if you have to ask...