Andial Splitter, simpler alternative solution.

[ischmitz]

Or one would work with Sal as he knows just as much if not more

[jjeffries]

I was going to say what Ingo said....Sal is known as a highly effective tuner of Motronic Carerras's and 964's. Not knocking SW.

[scarceller]

I do MAF conversion on these twin plug cars all the time. I have several solutions that are far superior to just a chip. PM me I'll try to help best I can to meet your engine needs.

[scarceller]

UPDATE: if you use my twin plug solution on a pre 84 tub please read!

I just did a twin plug module for an older (pre 84) car with a 3.2L transplant and my twin plug ignition module had engine run on issues. It simply kept running even after the key was was turned off. The issue was because the charging light did not have a diode in-line, we simply added a 1n4001 diode in-line with the charging light and issue was resolved. The 84-89 Carrera has this diode built into the harness but the older cars do not.

Without the diode the relay in my ignition module will not de-activate. It's also worth noting that neither will the DME relay! The only reason the engine stopped in it's single single plug configuration is because the coil lost it's power and the small trickle current through the charging light is not sufficient to allow the hi current needs of the coil to charge so the engine stops. But in my circuit I have a 40Amp relay the feeds the ignition modules and it takes very little current to keep that relay engaged. I mention this because others may see similar behaviors with other aftermarket ignition solutions.

[archnraft]

Hi Sal,

Very cool work here. I sent a PM... be happy to purchase your twin plug splitter for a 3.4 coming together this spring.

Best,
Anna

[ChrisBennet]

I've got Sal's twin plug setup and MAF conversion. (I've previously had the Andial twin plug setup.)
I'm very happy with both and I haven't even had a chance to tune it.

Lest you think I'm one of those, "I spent money on it, I've convinced myself it must be good." type of guys: I'm an engineer, I've hacked the DME tables on these cars a bit, I've built multiple 911 motors, etc. and I'm very skeptical of any performance claims. Every time I talk to Sal I'm impressed by the knowledge and thought he's brought to bear on these projects.

I got my twin plug running in the Fall and didn't have a chance to dyno tune it but I will let you know what I find out when I do.

[scarceller]

My advice with building the 3.2L single plug into a twin plug is to pay very close attention to cam selection and compression ratio. If you do not want to calculate these complex calculations you can simply copy the 964 motor recipe but as a 3.4L. Just use the 964 factory cam and get the compression ratio in the 10.8:1 to 11.2:1 range, this is the same target compression for the 964 motor and the factory already did the calcs for you! Very often I see twin plug motors with not enough static compression for the cam choice.

[archnraft]

Thanks Chris. Thanks Sal.

The pistons I have on the shelf are the 98mm Mahle 23mm pin 3.2 to 3.4 9.8:1 CR max morirz type, with these I'd NOT need twin plug, however, given all I'm putting in this engine it MAY make sense to sale these Mahles and buy a set of JEs at about 11.0:1 CR and go twin plug and your twin plug splitter would be needed.

For this build I'm starting with a relatively low mile 3.2 (50% leak down on no. 5 all other below 6% - may just be bad compression ring blow by). I already have a set of 130mm GT3 Pankl rods (we'll stack the cylinder base shims), 3.2 crank (rod journals are turned down by Marine, knife edged, cross drilled no 3&5 grooved/drilled, ion plasma hardened), 930 pump, etc. Considerring 993RS (113 LC), DC 993SS (114 LC) or DC 24 (113 LC) cams - overkill? I'm getting a set of custom anti-reversion headers built as well, DME chipped, etc. interested in your MAF solution.

My goal is to have a strong base engine built to be expandable down the road, meaning I could potentially ditch the motronic injection for ITB EFI with 3.6 plastic plenum setup, similar to Rothsport, that would then open up more cam selections - bolt on pieces to the strong base engine... I figure why not build for a lot more potential while we're in it...

Just throwing my thoughts out there for critique...

[scarceller]

The DC24 is a bit aggressive and won't work that well with the stock 3.2 intake. This intake is tuned for a sweet spot of 5800RPMs after 6200RPMs torque just drops quickly no matter what cam you chose. You need to pick a cam that works well at this 5800RPM sweet spot. The 964 factory cam is a good choice for this.

Also the amount of valve lift needed is directly designed from head flow numbers, do not ignore this. Spend the money and have the heads ported and flowed then pick your cam based on the results of that work. Also the lobe center line is very important but the stock air meter won't tolerate narrow LCA but my MAF system will. The 112-114 LCA you often see in a lot of these cams is a trade-off for idle quality and low rpm drive-ability, the 3.2L motor will actually deliver more overall torque on a tighter LCA of around 110LCA, the tighter the LCA the more the intake valve is open earlier in the stroke where flow really matters! But tight LCA also increases overlap and the AFM won't like that, so the factory had to make some trade-offs.

These off the shelf cams would work in a 3.4L twin plug at 11.0:1 to 11.3:1 comp:
964 factory, especially if heads are ported and flowed.
DC20
DC21
Elgin Super C2

All of those cams close the intake valve at about the same point and that dictates the dynamic compression ratio.

Feel free to email me to discuss your build further, I already sent you my contact info via the PM you sent me.

Originally Posted by archnraft

Thanks Chris. Thanks Sal.

The pistons I have on the shelf are the 98mm Mahle 23mm pin 3.2 to 3.4 9.8:1 CR max morirz type, with these I'd NOT need twin plug, however, given all I'm putting in this engine it MAY make sense to sale these Mahles and buy a set of JEs at about 11.0:1 CR and go twin plug and your twin plug splitter would be needed.

For this build I'm starting with a relatively low mile 3.2 (50% leak down on no. 5 all other below 6% - may just be bad compression ring blow by). I already have a set of 130mm GT3 Pankl rods (we'll stack the cylinder base shims), 3.2 crank (rod journals are turned down by Marine, knife edged, cross drilled no 3&5 grooved/drilled, ion plasma hardened), 930 pump, etc. Considerring 993RS (113 LC), DC 993SS (114 LC) or DC 24 (113 LC) cams - overkill? I'm getting a set of custom anti-reversion headers built as well, DME chipped, etc. interested in your MAF solution.

My goal is to have a strong base engine built to be expandable down the road, meaning I could potentially ditch the motronic injection for ITB EFI with 3.6 plastic plenum setup, similar to Rothsport, that would then open up more cam selections - bolt on pieces to the strong base engine... I figure why not build for a lot more potential while we're in it...

Just throwing my thoughts out there for critique...

[scarceller]

UPDATED design!

Altered my splitter design so it no longer uses a terminal strip, making the install and wiring far simpler.

Still just 4 wire hookup in the engine bay:
1 - Heavy Black ground wire goes to main ground bolt on intake runner #1
2 - Heavy Red 12v constant wires to rear fuse block.
3 - Small black wire is switched 12v and needs power in RUN and START this wires to the original stock coil's '+' post black wire.
4 - Small blue wire is the coil trigger signal this wires to the stock coil's '-' post green wire.

Few pics of the new setup.

[mysocal911]

Originally Posted by mysocal911

Well, I've seen a design using just two 964 modules and a few resistors, as I mentioned
on the other thread, installed on a twin plugged 911 3.2 at a well known SoCal race
shop and running reliably. Unfortunately the resistors were installed on the module
connectors under the connector rubber covers (very simple approach), so I wasn't able
to determine their values during the time the connector covers were pulled back.
But I'm sure there're many competent EEs who post on this forum who could easily
calculate what the required resistor values would be.

Now it's been reduced to one module, one transistor, 3 resistors, & one capacitor.
No need to do any mods to the DME ECM!