Dan:

Did you also relocate the ECU? If so, where did you end up deciding to house it?

Many many thanks

 

The only advantage COP offers is the lack of high-voltage spark wires running along the engine.
Waste spark still uses HV wires but no dizzy/rotor (which is what, an MX item every 10 years?).

Stock dizzy/coil/etc is more than capable into high boost turbo stuff so any NA build will get laughed at by the stock system. It just works.

You have sequential ignition already, that's just how a spark engine works.
Sequential injection seems to be, IMO, an emissions tool that maybe helps smooth out idle a little bit. But if you are already idling well...what's it get you?

 

Mine is located where the stock ecu is (under passenger foot well). The aftermarket box is slightly smaller than the stock box, so it fit fine. I reused the stock rubber wiring harness boot for the firewall hole to keep the weather out, newer boxes are waterproof so you could mount it anywhere I guess. It comes with like a 6ft USB cable that I ran under the carpet, so laptop rides shotgun when I'm logging.

I agree with Spencer, the stock ignition system is perfectly fine for NA motors. My motor is swapped into an 86 8v chassis, so I had those issues to contend with making CNP easier. Plus I'm of the mind that if I'm in there fixing something, why not modernize it too?

 

I'm running coil on plugs in wasted spark mode (due to suspect camsync sensor)

 

Spenser, Dan, Aussie: Thanks for the insight. I'm sure it's clear but I just want to reiterate my absolute lack of experience with all this. My plans for this, such as they are, are based primarily on what I read and can understand in the posts I've found on the issue. There seems to be vigorous debate, with some amount of data, but where I came down on the subject was that at higher RPM the distributor couldn't quite keep up with the timing demands. Again, I get fuzzy about this, but it may have also involved a good deal of influence from the coil and the dwell time. You can tell what my level of comfort and expertise is with all of this.

No matter what, I'll keep thinking about it. On my for sure list of things is a new ECU. I like the idea of taking the time to go through and replace the harness wiring as well, that makes a ton of sense and I happen to be sort of flush with 10 and 12 gauge, high strand count wire at the moment. I also know how slow I am about tackling these kinds of things and, I gotta say, I love driving this car so I don't want to take it out of the picture for too long.

I really appreciate you all sharing your thoughts and experiences.

Cheers!

 

how do the coils work with the distributor inline? Are they getting low voltage signal from the dizzy instead of high voltage? Also, your suspect cam sensor is unplugged :-)

 

If the system couldn't keep up with spark/rpm demands you'd get spark blowout and noticeable power dropoff on a dyno plot.
But we don't see that, even with 400hp 23psi turbo cars at 7000.

The dizzy rotor has a pretty wide contact patch so it can tolerate a lot of degrees of ign. advance from the ECU.
Maybe you want more for ???, but in my dyno testing years back there wasn't anything to gain past 32-34 degrees at high rpm at WOT on premium gas.

The stock coil is limited in its ability to "recharge" (detailed in that great Rogue_Ant thread from a few years ago) but it's still able to put out a strong enough spark to light the A/F.
That's all you can really ask for.

I'm not saying you *shouldn't* go waste spark or COP, I have considered doing it for assorted reasons, but none of those are weakness of stock parts.

 

The dizzy's contacts are removed and 4 signal + power and ground go in the primary side then connected to the 4 core wires to the COP, think of the dizzy as a connection enclosure
The sensor being unplugged is not the issue lol

 

Thanks Spencer, I really do appreciate the feedback. My tendency is just try to optimize things while I'm tearing things apart and rebuilding them. Your ??? is right on the money; I don't have anything particular in mind, I just don't want to leave relatively straightforward upgrades/improvements on the table. 30 years of engaged, intelligent people working on these cars has produced some cool and useful changes which can be made to the original systems.

To your point, 30 years has also shown which systems are robust and good enough for a standard engine. Interestingly, some things are still not quite so clear. I spent a good bit of my lunch hour going down the rabbit hole of the discussion on throttle bodies, as (I think it was you that pointed it out, from Peep's testing) there seems to be good reason to look into a larger throttle body for the 3L engine, when a new ECU is installed.

I'm still not sure where things stand on that (and I don't mean that to be an entree to derailing the VEMS/ECU discussion, I'm still in research mode on that bit).

Cheers

 

IIRC Peep was seeing 95 kpa in the manifold with 101 ambient.
so 6kpa being lost somewhere between the air filter and the plenum.
i mean, that's 6% of lost air pressure...so i would think you might be able to find ~6% more power just by eliminating that restriction.

the stock S2 air filter/box are huge so doubtful thats much of a problem. i think its the TB, since its the same size as a stock 140hp 2.5 8v NA.

 

curious, are the 944S2 and 968 throttle bodies the same size? i'd hope the 968 one was bigger and if so is it a straight swap to the S2?

 

don't know, but the flanges are different between the 2.
better to have the S2 bored out or get another unit (Ford 4.6 is popular) adapted.

 

I'm seeing worst of -3 MGP (Map-Amb) with 2.5in pipe straight tucked under the header panel with the largest cone filter I could fit. So 3%, or ~6hp loss from some intake restriction? ITB's would be a very expensive 6hp, but they'd probably sound amazing.

 

On the thread I referenced above (https://rennlist.com/forums/944-turb...ptions-10.html), it sort of petered out with Voith having sourced some Hayabusa throttle bodies. Looking around on eBay, there are examples for sale in the $100+ range. Totally out of my ability to do anything with but it sure sounds like there are folks on this thread that could go to town with something like that.

Cheers

 

Stock 140-163hp 2.5 8v NA throttle Body ID is 55mm.
Stock S2 TB is 60mm and stock 968 TB is 60mm as well. S2 and 968 TB are basically the same.

You can safely enlarge the 2.5 8V to around 59mm. See the difference below.

enlarged 944 8V TB

On a 944S2/968 TB you can enlarge from 60 to 63.5mm.


enlarged Porsche 968 TB

Fitting a large 70mm TB on a 968 won't help, since the opening of the intake manifold is only 64mm.