What's the hottest 3.2 cam you would use?

[Tyson Schmidt]

Originally posted by asphaltgambler
I would interested in who has done a speed-density system on a 3.2. Does anyone make a kit? If so who does the software?

The SDS is speed density, and uses GM components. Real simple to use, but time consuming. It's pretty cheap, if you use all the existing 3.2 intake system.

[asphaltgambler]

So has someone here done an install?? Do they have a website?

[camgrinder]

What year GM speed density system are we talking about? I know the GM 1986 +/- years were horrible with even a mild camshaft.

I like the megasquirt idea better.

[KobaltBlau]

Tyson is talking about the SDS system http://www.sdsefi.com/ which is a fairly affordable fully-programmable engine management system, which has it's own programming box so doesn't require a laptop. Of course it doesn't have all the bells and whistles of a motec or autronic. It is designed to use GM sensors (such as the MAP sensor), but doesn't use any of the GM logic.

I'm talking about megasquirt http://www.megasquirt.info which is a not-for-profit project that a bunch of enthusiasts put together. It is very flexible and can use lots of different sensors with proper calibration, nearly any sensors you can come up with. It is normally set up as a speed-density. I think if you put megasquirt on a 3.2 you could use most of the sensors that are already there, but you could dump the flapper box.

edit: Sorry John, I guess you already knew what I meant with megasquirt, but perhaps the info is still helpful.

[Tyson Schmidt]

I can't believe how clean that looks with all the CIS crap gone.

[dd74]

Noah: 255-260 hp?

[Brother]

Originally posted by Tyson Schmidt
I can't believe how clean that looks with all the CIS crap gone.

[B]

Yes, CRAP is correct.

[KobaltBlau]

Well Noah, you've got all the right stuff. Next step (other than cams) would be to get higher compression pistons and go to twin plug, which I can't see being worth it for you.

I really would talk to John about if he thinks there's a step up for you from a 964 Cam. with programmable MAP based EFI, and the pistons and ignition, it seems you're a couple of steps above a stock Carrera 3.2 in terms of cam possibilities. In particular, the valve pockets give John more room to work with possibilities, I would think.

[Jeremy Cottrell]

Noah, two things are going to hold you back on realizing all the gains of the Mod-S cam.

1. your compression ratio is on the low side for this cam. Not a big deal though.

2. SSI's have an I.D of 35mm. Ideally youd have bigger exhaust ports and matching I.D. headers.

And then there's the big question of whether it will idle well enough to not annoy you, and not stall or sub-idle dip.



*This is Tyson on Jeremy's computer again.*

[KobaltBlau]

You're tricky, tyson (on jeremy's machine)! do you have any ideas for something in between 964 and Mod-S for noah?

[camgrinder]

The DC24 grind is my first choice, then the Super-Cup and the EVO cams are all catagorized in between the 964 and the Mod-S. (Mod-S 112 lobe centers)

[Steve W]

The idle falloff problem is more an issue for Motronic with it's feedback controlled electronic idle control valve. On CIS with its simple bypass valve which is basically a thermospring controlled valve, I would not expect to have such problems. In fact we have considered before replacing the Motronic ICV with the CIS valve for more stability with hot cams.

[KobaltBlau]

yeah, my calculations were $1770 "retail", link below. I see what you're saying, but then you'll have an unknown engine, but we've been though this before on this board... I guess there truly is "no replacement for displacement" but I think your power would be around that of a stock 3.6, maybe more, depending on cams. Torque of course is more closely tied to displacement.

http://forums.pelicanparts.com/porsche-911-technical-forum/177474-efi-injector-mounting-outside-box-post1461444.html?highlight=twm+3003#post1461444

[Tyson Schmidt]

Steve, I think you're right about that.

It would still be a problem with CIS due to it's sensitvity to vacuum changes at idle. But I wasn't taking into consideration the fact that Noah did away with all the CIS crap, and is a speed/density system. He probably won't have issues.



Noah, the problem isn't the SSI's. The problem is the port sizes you'd need to take full advantage of those cams. It wouldn't make any sense to open up the ports if you're still running the small diameter SSI's.

It'll run just fine with Mod-S cams and you're existing ports sizes and SSI's. But I'm just saying it would be ideal to open up the ports, and that would necessitate losing the SSI's in favor of headers.


Or you could do what I'm doing on the 3.2. I'm using 993 HE's into a Magnafow. The I.D. on the 993's is 38mm. Perfect for the 3.2 exaust ports which are also 38mm. And still keep heat!

[KobaltBlau]

Tyson, you think it makes any sense to run TWMs with 39mm intake ports on a 3.0?

[Tyson Schmidt]

Originally posted by KobaltBlau
Tyson, you think it makes any sense to run TWMs with 39mm intake ports on a 3.0?

Heck yeah!

I was just going to respond to Noah to let him know that he should open up the intakes to 39 or 40 mm to go along with the 38mm exhaust ports.


Individual throttle bodies would be ideal.

Noah, I was thinking it would be cool to find some cheap Zenith Solexes and gut them to make them esentially individual throttle bodies. You already have the injector rails and everything else.

[camgrinder]

I would go with 10.5-1 with the "DC40 on 112" cams.
Comparing the 964 cam with 9.5-1 compression gives an effective compression ratio of 7-1. The DC40-112 with 10.5-1 will have 7.37-1 effective compression. I aim for 7.5-1 or less with pump fuel. (91 octane)

To clarify what effective compression is:
Swept volume is measured from piston bottom dead center to piston top dead center. The clearance volume is the area left over between the piston and the combustion chamber. To calculate static compression you add swept volume to the clearance volume and divide by the clearance volume.
The effective compression is calculated based on intake valve closing. The engine will not make compression until the valve closes, on average 70 degrees after bottom dead center. In this case the 964 intake closes at 73 degrees and the DC40-112 closes at 78 degrees. The cylinder volume left after the valve closes is now the swept voulme and can be used in the compression ratio formula. The trend is, early valve closing = more effective compression and later valve closing = less effective compression.

By changing the camshaft lobe centers from 102 to 112 adds 5 degrees to the intake valve closing. The engine can now tolerate more static compression without having to twin plug the heads.

[camgrinder]

Andy,
You are correct. If the dome is too tall I would recommend the twin plugs.
My point was the cylinder pressure is not the reason for twin plugs.
I think Ted at German Precison does the twin plug mod reasonably priced.

[KobaltBlau]

Thank you for being very clear, John. I always look forward to your posts!