Ollies in Santa Anna, CA will twin plug heads for 250.00 I think thats what I paid about 2 years ago.

Is that just the machine? On heads that are removed? I thought I knew what it involved but now feel like I just unlearned some stuff. What is the cheepest twin plug distributor to use?

Heads HAVE to be removed to machine them for twin plugging. There's no way around that. Whilst it's off, refresh it with new valve guides, titanium retainers, racing valve springs & GT2 CAMs :D

"Cheapest solution" is to go with a 964/993 Twin Distributor (~$300 second hand) and get your hands on an Andial Signal Splitter (~$600) and a new set of aftermarket Magnecor leads (~$400) and you're done :D :cool:

OR if you have deep pockets, go with a complete aftermarket EFI system, with DFI coil packs :cool:

O-crap!

"How much boost can a 3.3 handle" is a question that has no answer unless you qualify it with at least one other variable - time.

When properly built and driven they can handle 1.0 bar for years.
When properly built and driven they can handle 2.0 bar for minutes.

How do you plan too use the engine?
What are your power goals?
What is your (ongoing) budget?
What fuel system and other constraints do you have?

All these questions must be answered first.

I've heard from a few sources that once you get to 98mm pistons, it's a good idea to go twin plug even on a low compression turbo motor. That's why I did it.

$250 sounds too cheap for twin plug machining. I would expect more like $500 for twin plug and about $500 for a valve job plus parts. If I had it to over again I would get the original plug hole welded up and have both spark plugs be the small plugs to increase compression.

Twin plug isn't REALLY necessary for big HP output.

Juan Ruiz's 10 second turbo Carrera was a single plug, 3.3L turbo (based on the Carrera motor).

If you have your engine management sorted properly, you really don't need to twin plug. Just run an aftermarket ignition system,, like a MSD or Crane system and you'll be right. You won't be blowing out the flame at high boost levels with those high output systems.

I think your flame front is better with twin plug, and combustion is a little more thorough, and you can run a little more timing. That's why most people who are otherwise hip-deep in their engines tend to do it--because it's better than not doing it. But maybe it's not something you'd do if you weren't already "in there", I suppose.

But if the heads are off and you're mucking around in there with Ps&Cs, valves, retainers, etc., it's no big deal to do it.

Bruce Anderson has a good explanation of twin-plugging's benefits in his book, as I recall.

Yeh I agree, Bruce. It's no big deal to have the heads machined once they're off. It's all the extra hardware (and associated cost) needed to hook up the extra plugs. For someone on a budget build, it's not really necessary ;)

Having said that, I got mine twin plug prep'd, but am still running single plug at the moment until I can save a bit more cash to finish the twin ignition system. Already have the 964 distributor. Just need the extra leads and an extra Crane ignition system to finish it off :confused:

Merv--

How much cheaper is that approach over, say, an Autronic system? I got my Motec because I have more dollars than sense when it comes to this car, but I understand that Autronic is 90% + of Motec for a good deal less money, and it's based in your neck of the woods as well...

I'm sure you've looked into it, but I'm curious.

Well, I'd say significantly cheaper than an Autronic setup.

I got a rebuilt 964 distributor for $300 and a 2nd Crane HI-6 ignition system will set me back another $400, plus the cost of a bottom set of ignition leads.

If I were to scrap the Motronic and go full Autronic, it'd set me back approx $5k installed & tuned :eek: Motec probably another $1k on top of that!!!

Suffice to say, NOTHING beats a fully programmable aftermarket system like Autronic/Motec. I'd say I'm probably down 10-15% of power running with the OEM Motronics, Air Flow Meter & Protomotive CHIP.

When I eventually go pressure sensing, it'll transform the drivability significantly. Just can't afford that right now :(

Having said the above though, Protomotive have a full pressure sensing/MAP based conversion for the OEM Motronics which runs at about $2.2k and they even provide you with a complete base map for a 3.3L Turbo, GT2 CAMs (map created on engine dyno). That map is supplied with the new ECU free of charge, so it doesn't cost much to get you up and running. I'd say some minor fine tuning would be required, but they do a complete re-tune for $110 ;)

OK, here is the stupid question. Why am I always the one to post it? Stupid? Whatever, here goes. Can't you "T" the ignition wires to twin plug if you have a powerfull ignition syst? I mean, the system at high rpm is basicly lit all the time anyway right? I have no idea the technicals of these ignition systems but it seems good to me. Please let me know how wrong I am. Thanks, BA And yeah, my thought process revolves around saving $'s

Wow, the delta between your set-up and the Autronic is bigger than I thought.

That said, I only wish it would have cost me 5 grand to get my Motec bought and dialed in right (especially cold start)!

If I were to have done one thing differently when my case was split and everything was being re-done, it would have been to tap in a cylinder head temperature sensor....

That Protomotive guy really likes the GT2 Evos. Talked me into 'em, in fact.

quattrorunner, no, you can't T the ignition wires to drive the two plugs per cylinder. The spark won't be hot enough. You need a 2nd ignition coil and 2nd distributor to drive the secondary plugs - thus the need for a 964/993 twin distributor. Or, as I said earlier, a pair of direct fire igntion packs from a Holden V6 or something similar, driven by an aftermarket engine management system.

Bruce, it was a no brainer for me to stick with my Carrera's Motronic system, for now anyway. OK, so it's not the most refined solution, but it's significantly better than a CIS setup ;)

What are you using to feed the temp input of the Motec, if no head temp sensor?

How do you like the GT2 EVO CAMs? I love them! When the revs hit ~4Krpm's, it really wakes up the beast :cool:

Merv--

Running off oil temp, which is , uh, inexact...Lots of trial, lots of error. But right now I've got it to where if I give it a little throttle for 10 seconds on dead cold start, it will hold fine. But it was bad for awhile there. Maybe 3-4 minutes of throttle just to get it not to die on lift-off.

Cams are great. But the combination of the engine coming on cam and the turbo really kicking in is pretty hairy. My torque doubles in 1000 rpm. Total slingshot. Fun, but tricky in spots around a track.

:eek: Torque DOUBLES in 1Krpm? Must be a blast to drive, Bruce :cool:

My car feels pretty tame as the boost builds up, but once it hits the 4K mark and the CAMs come on at the same time, it feels like you've been punched in the chest. A bit scarey for unsuspecting passengers, but I love the look on their face afterwards... LOL!

I have a Protomotive Twin Turbo system waiting to be installed on my engine. Just waiting to get the wife's car back on the road before I can go to a twin setup ;)

How much boost are you running on the street and on the track, Bruce?

I was running at 1.25bar daily, for a short while, but found it to be too aggressive and eventually, my poor clutch just couldn't take it anymore and started slipping :(

I'm more conservative than that. I stay at .8 to 1.0 almost all the time. Maybe 1.1 on track day, with 110 in the tank.

For street driving, that's enough to handle pretty much anything that comes along, and it keeps my engine fresh and happy. I've put way too much into this car to screw it up by cowboy-ing on the street, anyway.

For track driving, I struggle as it is to drive up to the capabilities of my car at lower boost levels. More boost wouldn't help ;)

For me, a street/track mix is ideal. The track work makes me a much calmer street driver. No need to get macho on Neeighborhood Way when I've just drained my adrenaline stores pretty good at the local course...

Hi Bruce. I'm sure with the Motec, 1.0bar is plenty of power anyway :)

I'm running 1.0bar daily now and the engine is happy there. I can't wait to have the twin plugs running though. I seem to be going through a ***** load of fuel and I suspect it's b/c of the lack of an O2 sensor and not very good flame travel. Twin plugging should make it burn much cleaner and accelerate more crisply ;)