Henry in regards to detonation issues with cis you mention the 80 to 83 models. What about the earlier model 78 and 79 cis without the lamba and the larger runners? Do you still need the euro fuel distributor? Will the 9.8 to 1 work with that or is detonation still an issue. I live in south florida so heat is always a problem here. Waynes book recommends either the 9.8 or 9.3 to 1 on a 3.0 with cis. Does going to a 3.2 make that much of a difference? This is my first Porsche and I love it but I would like to make more horsepower than in my Ford Ranger. But I want reasonably reliability with my horsepower. Also as you can see my 2nd car is a Ford Ranger so I am on a budget.

It is true that larger cylinder diameters create an engine more susceptible to pre ignition or detonation. Having no or eliminating the lambda control will allow you to adjust the mixture with increased ease.
Mixture is important when it comes to controlling detonation.
The problem is that CIS injections are inherently lean running at cruise.
The way the system works is that as you open the throttle valve you increase air over the air flow meter.
During acceleration the air lifting the plate is turbulent and lifts the plate sufficiently to move the fuel distributor to a rich running position.
As the engine rpm stabilizes the air flow across the plate becomes laminar (smooth) and the plate settles. When the plate settles the mixture goes lean.
If the engine is subjected to an increased load (corner, hill, wind etc.) during cruise the engine may suffer detonation. Cruising the engine at or near max torque (max cylinder pressure) will increase this possibility.
This is the condition that the Andial fuel enrichment devise is attempting to overcome in turbo charged applications.
We have tried modifying the plate with a Gurney lip with some success.
To answer your question as completely as possible, all the issues I listed in the previous post should be addressed to be perfectly safe.
Real safety comes from lower compression.

Euro fuel distributors offer higher fuel delivery at all rpm ranges. 78-79 US fuel distributors are not the same as the euro fuel distributors. The US started using lean burn technologies as well as after burn systems to control smog in 1978. In 1980 they went to cat. converters and closed loop lambda/frequency valve systems to nearly eliminate hydrocarbon emissions.

Playing with system and control pressures can assist in overcoming a fuel delivery issue.

Detonation is the condition where the fuel mixtures ignites prior to when the ignition system would correctly ignite it.
Detonation is also caused by an overly accelerated burn after ignition at is the result of hyper fuel volatility. Higher octane means controlled volatility.

When compression ratios increase ignition timing becomes hyper sensitive. With modern day computerized engine
management systems this hyper control is easily obtainable. With mechanical distributors the problem become far more difficult.
The key is to retard the timing as the engine passes through max cylinder pressure (max torque) and then adding timing as necessary to achieve power at higher RPMs.

Alright then the cis runs lean at cruise and thats how it gets the decent mileage. So the options are go with the 9.8 or 9.3 with cis and gamble on no detonation. Stick with the 8.5 to 1 I already have. Go duel plug and or switch to carbs with a hotter cam. I can see now that I will need a plan set in stone before I start as one decision will effect different component choices in the build.

Thanks, Henry.
Some observations, please:
US '78 CIS,
'78 Distributor,
Timing set to max (33 deg at 4-5000) vac advance disconnected,
(When vac is re-connected, the timing moves from 5 deg to ~8-9 deg at 900 RPM)
This ss 3.2 loves to run with these settings; very responsive, no pinging.
Revs very easy, really wants to run.
Mixture on the rich side, 91 octane.
(SSI's, 2in/2out, Exhaust tips show darkish residue after cruising at 3300-3500 RPM)
I am not into high RPM's, seldom going past 5000.
Any thoughts on the above?
Like: timing set to max advance instead of 5 deg BTDC?

My Kremer engine is from Europe, 98 mm P/C's, 9.8 compression, stock 930/03 (CIS) cams. Mild polish, SSI's and factory muffler and distributor (no vacuum advance).

Specs from Kremer are:

Idle set to 960-980 RPM
Ignition 5 degrees BTDC at 900 rpm
CO set to 3.5% - 4.0%

I am just changing plugs from W3CS to W4CS as the W3's are a pretty cold plug and likely spec'd by Kremer due to the high speed autobahn runs they envisioned for the engine.

Car runs like a clock, strong in power and driveability....no problems.

I am curious whether the higher flow Euro fuel distributor makes any difference in power...more gas, more bang...right?

Oh yeah, I always run 91 octane (Shell). I rev the crap out of it, I see 6500 rpm regularly...

I have never heard anything that even faintly sounds like detonation....wouldn't recognize it I am afraid as I have never heard anything ever..

Dennis

sounds like a great set up Dennis. Do you have any rwhp or dyno run #'s? If not, any comparison comments to, say, a stk 3.oL cis car??
Thanks, Bob

No I do not, but next time there is a local dyno night, I am planning on doing so. I have only driven a 3.0 for a few minutes.....so can't compare bum dyno.

On the track, whenever I am behind an SC, my car seems a fair bit quicker, but there are differences in driver and gearing (i have the 7:31 R/P, plus Quaife)....so also hard to confirm.

Dennis

Dennis:
You mention no vac advance.
What type of distributor do you have?

Why stock cams? Why not 964?

Plugs: JW recommended to stay with W5DC for my ss 3.2 and just check them after a hot run.
I have the 964 cams, CIS, SSI's.

Distributor is the one that Kremer provided with the engine...it has no vacuum advance is all I really know.

At the time the engine was built ('89), the 964 cams were not really around yet....

Your recommendation for W5's makes sense....I am gradually moving that way, W3's being a lot colder than the W5's...

W4 is sort of a midway step for me.....oh yeah, the C/D designation is a bit uncertain for me. Near as I can tell from Bosch's web technical info, the only difference is the extended ceramic nose for the centre electrode. But Kremer recommended W3CC originally, I couldn't find those so used W3CS (silver) and have had no problems.

Dennis

O.K.
Still hoping that Henry will reply to my questions above.
He obviously has a lot of experience.
What puzzles me is that, after more than 2 years researching before I did the ss 3.2, I didn't come across the issues Henry mentioned.

I found that the conversion to ss 3.2 was done by many without serious problems like detonation etc.

I'm sorry to hear that you are puzzled.
The truth is that many experts on this forum refer to the detonation issues associated with single plug, big bore Porsches. The inherent lean running condition of the CIS injection only tent to exacerbate the problem.

That said I see two issues with what you post.
One glaring issue is that the vacuum advance should not be advancing at idle. I believe you have the vacuum line hooked up incorrectly.
It sounds like you have the distributor advance connected to a port below the butterfly so that at idle you are advanced. It should be hooked up to a port directly above the butterfly.
What you want is 3-5 degrees static and no vacuum advance at idle, then 3-5 degrees vacuum additional immediately after the throttle opens and it should be there all the way to full throttle.
Taking into account your increased bore and compression I would set my engine at 30-32 degrees full advance with the vacuum line connected.
I would hope for 5-7 degrees at idle. +5 directly off idle, then a steady advance to 4800 rpm where I would hope for around 26-28 degrees then an additional 2-4 degrees (30-32 degrees total) in the remaining 1600 RPM to 6400.

Many thanks Henry; I'll pay attention to higher octane and timing.

I double-checked the location of the advance and found the problem: The connection-nipple on the front of the TB looks well above the butterfly but, when looking inside, it's routed below the butterfly.

The correct connection for the advance is in the rear of the TB.
Now the timing is as you describe: 5 deg idle, then steadily advancing to 33 deg vac connected.

I have 3 distributors to play with: '78, '80 and '82.
They appear to perform the same: max 33 deg.
If someone wants 35 deg, it seems that one ends up with 7-8 deg in idle.

Many thanks for your help on this issue, Henry. SmileWavy

fuel control
 

Hey, using aftermarket efi "brains", like Megasquirt, really gives one so much flexibility/ safety. Using a WB O2 sensor (fuel control) and programmable crankfire can really help these big bore cis single plug engines (controllable advance). With Msquirt there is basically no reason ever to go lean ( oh yeah except when your fuel filter fills with crap!).

I am using some pretty overlappy cams too (you are not limited to supersports, as is sometimes suggested). Well Ok probably couldn't use cis pistons with my particular cams, but you can use a single intake manifold as i am doing,

So come on guys, lets get rid of those cis air flow meters...

easy
PS Henry, i need one of your nice finned sump plates- they look perfect.

I've seen those sump covers on ebay.
http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&ih=015&sspagename=STRK%3AME SE%3AIT&viewitem=&item=250022544285&rd=1,1