3.6 C2T Questions

Two questions for you turbo fans out there

1. Was the 1994 C2T 3.6 engine twin-plugged?

2. What are the advantages and disadvantages of Motronics versus CIS and why did Porsche not use Motronic in its production turbos until the 993TT?

The 94 Turbo 3.6 did not have a twin plug setup.

from Origional Porsche 911 by Peter Morgan; "It used the crankshaft, rods, crankcase, camshaft asemblies and barrels from the 964, but the pistons and camshafts themselves (with increased lift and greater overlap) were new. Unlike the 964 engine, only a single spark plug per cylinder was used, for space reasons. The previous model's early Motronic injection/ignition system was retained. Compared with the 3.3-litre engine, the compression ratio was increased from 7.0:1 to 7.5:1, and maximum boost went up to 0.85 bar."

Here is a post from Steve Weiner at Rennsport Systems on this same topic. I am contemplating this mod for my 3.3.

David

"I am considering converting a modidifed 86 930 from cis to motronic, need advise on hp gains, cost, or any recommendations or pitfalls on conversion. thanks

Re: converting cis to motronic system
Steve Weiner-Rennsport Systems -- Monday, 16 October 2000, at 8:45 p.m.

Hi Tim:

Great question,....We have undertaken several conversions on 930's from CIS to MoTec, its pretty close in principle.

Give the immensity of such a project and the need for an engine dyno for proper fuel and timing mapping, I might ask the question,....Why?

Although the stock CIS system will not flow any more airflow to support power levels beyond about 450 HP, the real limitations for turbocharged street engines are octane related. Simply put, Motronic will not, in and of itself, truly do anything for you unless you are going to enter your 930 in competition and use racing gasoline.

The K-Jetronic system used on the 930 is well suited for that particular mission. Further, it can be modified to make a suitably equipped 930 engine make a true 440-450 HP which, by anyone's standards, will perform very very well.

Unless you have the ability to create Motronic chips and create your own mapping as well as access to an engine dyno to prevent the inevitable piston failures that result from trial and error in developing software for boosted engines, I might suggest some other things that would be far more cost effective and less expensive to develop.

I love technology more than most folks, but having BTDT on this subject on more than one occasion, even having ALL of the requisite tools at hand, its a damned expensive proposition for little gain on any 930 to be used on street gasoline.

Several Turbo engines that we have built have made 440--455 HP and configured like this:

3.4 to 3.5 litres, Twin ignition, B&B headers/muffler, K27/200 turbocharger, C2 Intercooler, Extensive in-house headwork with custom injector blocks, Extensive intake manifold mods, Modified airflow meter and fuel distributor,

No more than .8 bar!

Its all about airflow management. All of these engines were making 300 HP by 3000 RPM, so they displayed great manners.

I hope this helps,......LOL.

--

Steve Weiner

Rennsport Systems

Portland Oregon

503.244.0990 "

David,

Thanks for the very informative response! Steve Weiner upgraded my entire suspension about 15 months ago when I lived in Portland, OR. From what I've heard and seen, he definitely knows what he's talking about.

I'm struggling to decide which turbo to buy. Although torque/hp from 3k - 6k is important to me (I'm afraid more than 450 might create rear traction issues), the critical consideration is track handling for DE/autocross (street comfort is NOT an issue, the stiffer the better and who needs those back seats anyway). Budget $60k, including cost of modifications. So with that in mind, is the A-arm setup on the 993TT much better than the coilovers in the 965?

Do the 964 turbo models share the same dual mass flywheels as the 964 and have there been any problems like in the 964. What are the differences between the 930 and 964t ignition systems. Is the 964t system easy to reprogram or is it chip based?

Here is a link for CIS to Motronic conversion if anyone is interested:
http://www.milford.ndirect.co.uk/kstar.html

The K Star system looks very interesting. Any word on effectiveness of this unit and also its ability to control fuel, etc. beyond the CIS limit that I've heard of ~450hp?

Pick up the February 2001 issue of 911 & Porsche World. It has a great article about a guy with a 965 which had been warmed over to produce around 460 hp...after the mods, they realized "that there was just too much power for the car to cope with. To start with, we were hitting the rev-limiter, so we decided a six speed gearbox was required. More seriously, though, we simply couldn't get any traction. Even in the dry the rear wheels were losing it as soon as the hot cams came on." Here's where this gets cool...they adapted the 6 speed gearbox, front drive shaft yokes, flanges, brake discs, calipers, differential, drive axle (bolted straight to the 965 subframe) from a 993 Twin Turbo. The rear retained the 965 suspension since the 993 TT body shell was so different, the 993 TT subframe simply would not fit.

Since the 993 TT four wheel drive system doesn't involve electronics (self-contained viscous couplings), once they were bolted into the car, no further setting up was required!

I had the same concerns, thus I started mine based on a 90 C4. Had I thought of it, I probably would have went this route. I am currently looking for the 993 TT parts and will change to this setup in the future. The 993 TT 4 wheel drive configuration is much simpler than that of the 964 cars. I think that a 450+ hp 965 4 wheel drive car would be amazing...About another month before mine is on the road...Check out my latest project http://www.fototime.com/ftweb/bin/ft.dll/pictures?userid={D9C5473F-C312-4668-9D00-AE08CFF7B093}&AlbumId={48A93CC8-135B-11D5-AEBD-0050045DED94}&GroupId={48A93CC9-135B-11D5-AEBD -0050045DED94}

The 965 used the same dual-mass ZMS flywheel that was on the 964. It used the same limited slip differential as the Carrera 2 RS.

Since the 965 is still CIS (like the 930), it is not chip upgradebale. The 965 does have a digital electronic ignition system which is crank-fired and gets its pulse from the flywheel.

David

[This message has been edited by David Griswold (edited 03-22-2001).]

Nice project! Funny, one of my considerations was to take a 993 with varioram and have the following done: Protomotive's new bolt on 4.5 psi twin turbo (including intercooler, aux oil cooler, clutch/flywheel, etc.), headers/exhaust, track (but streetable) suspension, maybe big reds, and lighten the car as much as possible (within budgetary reason). For some reason I find this whole build-up process appealing. My only concern is that, when all is said and done, will I have spent the same amount as a stock 993TT of the same year that would probably be a more competent street/track performer AND that would still be upgradeable, funds permitting? Any thoughts based on your experience?

David,

Does this mean that the early 965s have the mk1 dual mass flywheels and the 1992.5 model onwards have the more reliable mk2 dual mass units or do all 965s have problem free flywheels? Do they share the power steering problems with early 964s too? And about the digital ignition, can it be upgraded to twin plug easily or do you need a complete new system and can the existing system be reprogrammed easily?

tcampbell, for 30k spent on any 3.6 engine, you can have well over 600bhp so if your base car is an 89 C4 then you can have a hell of a car for around 65k. To upgrade a 993tt to that level costs the same too as you'll have to upgrade turbos and intercoolers which are big bucks. Maybe the best base car would be the 965 3.3 in terms of performance to dollar as it already comes with the widebody running gear as standard. I know that will be my next upgrade.

Have a look at http://www.iqthost.com/orpcax/

Btw, I think the 993 rear suspension can fit into the early cars. IIRC, there was a feature in Excellence last year about an early 70's 911 with a complete 993 suspension transplanted into it.

930fan,

Thanks for the info. And the confirmation that n/a to turbo conversion might be the way to go for me given a rigid budget. By the way, the link to Rick's car is nice. I lived in Portland, OR until about a year ago and saw him run his C4S at PIR a few times. He pushed that thing to the limits. Even lost an a-arm through one of the turns. No noticeable damage despite spinning out. Good thing it wasn't turn 9.