So is twin plugging just insurance?

[Weaver]

Hey Steve!

I first have to say, I applaud you for starting a forum for nuts like me, thank you. I've read your posts on Pelican for the last 13 years, I've always appreciated your insight. I never post, I'm more of a listener than a talker.

I'm starting to gather info, parts, and tools for the inevitable 3.2 litre engine rebuild. I'm probably 2 or 3 years out, but I'd rather be ready than scrambling. My specs now:

'88 3.2 litre US spec, G50
K&N cone (PO broke the backside of the airbox)
Steve Wong chip for 93 & SSIs
SSIs with a M&K 2 in 1 out
Magnacor KV85 wires

Obviously, if it's torn apart, let's try and get more punch out of it. My plan started out wanting 3.4 P&Cs since I read it was a plug and play. But then I read the over 9.8 to 10.0:1 CR needed twin plugging. I wanted to avoid that, even if I had to ignore your comments about it. Plan B was 3.2 Euro set up, thinking it's the same P&Cs as the Euro engines that are single plugged. But then I realized that those too would benefit from twin plugging. And is the gain from the Euro P&Cs that much of a difference? I am starting to wonder what to do. I just want the typical Porsche reliablity but with much more punch. I have $10k budgeted, doing the work myself (retired Indycar mechanic and g-box guy), and would send the head to you for drilling and valve&guide work.

So after reading just about everything availible and talking to some good friends, it sounds like twin plugging is just good insurance against bad gas. We have 93 in Indiana, but it does have 10% to 13% ethanol. And if I drive to Illinois or Kentucky, well you never know what you get.

Questions:

You recommend the 964 dizzy over a 12 plug Marelli style, why?
Is it possible to find Andial splitters anymore? I really don't want a bunch of extra boxes or stuff that doesn't look factory (MSD, etc.)
Is the 964 cam the most sensible, or 993ss? DC cams or WebCams or what?
Keeping the SSIs, need the heat.
I have a re manufactured AFM on the shelf, should I consider a MAF and if so who's?
When you say, "a 3.4 twin plug with 964 cams runs Very very well" how well is Very very?
Can this be done "Very very well" with SSIs?

I hope this is not too long, I just love talking about Porsches!

Thanks for your time

Ron Weaver
Indy, IN

[Steve]

Hi Ron,

Thank you for your kind words about our forums and my PP postings. I started this one to be able to offer technical assistance without all the BS and personal constraints one has from participating on other's playgrounds. It will be successful with participation by people such as yourself so spread the word.

Your project sounds interesting and has lots of potential if you choose your components carefully.

Mahle makes a special 98mm piston made specifically for single-ignition at 9.7:1. These are a wedge dome design made to push the fuel-air mixture toward the upper plugs and help prevent the pockets of gas at the outer edges that trigger detonation. I've used them quite successfully for many years in a variety of 3.4 litre engines that run very nicely on pump premium, provided the ignition mapping is suitable for local fuels and climate.

Certainly, you can use twin-ignition, however you will need the RSR-type pistons and Motronic engines will require building a signal splitter (like the old Andial ones) to operate both coils. The 964 dizzy is a little cheaper than the 12-plug RSR style ones.

Andial is all gone and so are the splitters. The person who made them for Andial won't do any more; I asked him.

964 cam is the best choice for a Motronic 3.2 or 3.4.

SSI's are OK. but they do kill the upper RPM power. Lose the M&K as they make noise, not more power. There are better choices.

MAF systems are only as good as the software and I've never found any that ran well. Talk to Steve Wong about this as he may have one by now.

Engine assembly techniques vary widely so this is why I rarely quote numbers since a DIY'er may not see the same things we do here on our engine dyno. There are a LOT of variables at work here.

[Weaver]

Hey Steve!

Thanks for the reply. I will spread the word, I promise, I just need to make sure I don't step on toes in the process! With that being said, now I can say this:

AWWW COME ON STEVE!!!! You are now screwing with my head!!!!! I've read every post of yours on two sites dating back to about '01, all of them are warning people to twin plug over 9.7:1 CR. I've been trying to find an example of a successful single plug over 10.0:1 engine, only finding one with 993ss cams and never driven hard in hot Florida summer weather. I have finally accepted the idea of twin plugging, actually excited about it, and you throw this curve ball at me?!? When did Mahle come out with a Motronic 3.4 piston? It had to be after '10, I can't find any conversations about it!

Quick story. I have made a few friends at the Porsche Museum in the past few years, two of the "Guest Guides" and one in the archive room. When I was there last month for the Le Mans exhibit one of them took me into the Classic workshop on the ground floor, behind the coffee bar. He introduced me to the mechanic who had just finished restoring the '73 Targa Florio 3rd place RSR #9. (I'll post pics when I learn how to resize on here) Older gentleman that had been in the Motorsports dept. most of his career. When I told him I was going to twin plug a 3.4 Motronic engine, he looked at me like I was crazy and said I was wasting my time, in a typical German way. He then told me that he had built many high compression 2.8s, 3.0, & 3.2s for the street and track with only single plug. But I failed to translate to him how bad out gas has gotten here in the states. Thats when I thought of the "insurance" point of view. Its not a horsepower gain, but a long term insurance policy against detonation. Basically protecting your P&C investment.

I'm going to very carefully choose my components for this project. I have all of the time in the world, my 3.2 litre is only using a quart every 600 to 700 miles, with only smoke during start up after sitting for a few days. I don't think I'm going to do this for a few years. I'm just considering purchasing the P&Cs now before the supply goes down and the prices go up.

A few points and questions:

1) I was always going to use Mahle P&Cs only. This is not up for debate. So there are two Mahle 3.4 solutions; one is 9.7:1 for Motronic and the other is 10.3:1 for twin plug, correct?

2) The 3.4 pistons for Motronic, do these need to be relieved or pocketed in anyway for clearance?

3) 964 cams will be used, should I regrind my 3.2 cams or do you recommend a supplier?

4) I can't believe Steve W or someone else has not copied the Andial splitter. I wish I could but I'm not an EE. I'm not afraid of electronics, but this might be beyond my ability. There can't be more that $125 of parts in one, including the Bosch ignitors. I would pay someone to copy theirs. I have a buddy who works at PMNA in Santa Ana, maybe I ask him to see if the parts guys have seen any laying around .

Have you twin plugged a Motronic car since the disappearance of the splitters, and if so what did you use?

4a) I've done a hundred searches for something similar to the Andial splitter, and one of them is actually for a 2 rotor Mazda 13b. Its the M&W Pro14r. have you ever seen one of these in action?

5) I totally understand why you would never quote numbers for an theoretical engine that a DIYer was building. But if you were building a 9.7:1 CR 3.4 engine, how much would you be leaving on the table compared to a 10.3:1 engine?

Is that the difference between "very good" and Very very good"?

6) I'm ok with losing a little top end RPM if I can gain some low end torque, I need to keep the SSIs for the Indiana fall weather. Are Monty's still as good as they used to be?

Thanks for your time! Hope to talk to you soon….

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[Steve]