Thanks I'll check that out, I hope to have the intake halves by the end of the week then I can see what I have to work with.

Should I get the stubs and fuel rails? Could the stubs be modified to fit a SC head?

I'm asking because I've been offered these parts for free/cost of shipping. If I can cut off the old flange and weld on a new one it would save time. Oddly enough Ihave limited experiance with the 3.6 engine.

Get them both. You'll need fuel rails. Even if you don't use the bases, you might want them to fab something up.

Do you even need the flap? Why not just run a straight pipe and keep it open all the time?

https://rennlist.com/forums/993-forum/608345-resonance-flap-effect.html

This is of course with non-stock cams, but still interesting.

I would say it depends on the build. I had a 3.6L race engine that, due to class rules. had to run a 1995 993 intake and 1 5/8" headers. The flap being open or closed made a difference there.

Soon I will be putting a a 996 GT3 setup on my 369 RWHP 3.6L race engine with AT Power ITBs and 1 3/4" headers. We will do dyno runs with the resonance flap open and closed at 100% throttle to see the differences. We will also do some partial throttle tuning to see what happens with the resonance flap open and closed to how that works out.

I am told that on engines like mine that the flap makes a difference and that difference is not small.

interesting - be sure to post it here please.

where did it make a difference on your current build? The flap is mostly open on a racecar I guess? Do you gain more torque in low revs (<5000)?

I would really like to find a good solution to our JSR ITBs as well.

I'm going to use some kind of flap but I will remove it if it doesn't do anything.
I won't really be able to make plans till my intake halves get here.

Remember too that cup cars from 964 to now (though I do not know about the 992), all had at least one operable resonance flap.

I had 993 plastic intake with single throttle on 3.8 rsr enduro pistons and factory rsr cams 1.75” headers and res flap makes a difference. Though that intake was too small for the motor...

I see some like the plastic intakes, why is that? Thinner? Lighter? more volume? better design?

I want the aluminum, #1 reason is I can weld it, but I was just wondering why some like the plastic.

Smooth.....and also light.

I have also heard someplace that there is less heat accumulation in the plastic version (makes sense; less mass) lowering charge air temperature some. Every little bit helps.

http://forums.pelicanparts.com/porsche-911-technical-forum/914607-964-resonant-intake.html

Post #8

Torque is better from 3500 - 5000 with valve closed. Both torque and hp improves with valve open at +5000rpm

Why would you need to run TPS only with EFI+ITB's??

Any decent engine management system has at least Alpha-N/MAP hybrid load strategy where you also have MAP as input for fueling thus having much improved driveability and mixture consistency against various air temps+humidity.
Absolutely no reason to ruin nice and clean look of ITB's and hinder their performance (and yes, I recently saw on the dyno with 3.8liter 964 engine that Singer-like intake plenum (looks fancy) held the engine back, after removing the plenum engine picked up nearly 20 hp.

Well...I could make the argument "WHY EFI?" when carbs make more power at WOT.

I've been doing the EFI thing for near 20 years, if I dont like the result I'll do ITB's, no big deal. As far as looks go in a 914 you can't really see much in the engine bay except direct overhead.

It seems a lot of peeps have troubles discerning the difference between a street car and a race car. I daily drive (summer) my 914, it's not a race car.

The 964 plastic intakes are reported to flow better and more even than the earlier cast aluminum. The early aluminum 964 intakes also had a dual stage throttle body and the later plastic have a single throttle body. Plastic is considered a upgrade on 964 with aluminum intake.

john

Why do you think carbs make more power than EFI at WOT?

I don't have time for a debate, I have a dozen or so engine builds to be working on.

Carbs can make more power at WOT due to the intake charge cooling effect. There have been several tests on V8s over the years by various magazines and most support that a well tuned carb can make a tiny bit more power. Cold fuel has also been shown to make more power then hot fuel.

There is no question that EFI is better for drivability, gas mileage, and altitude and weather compensation but for a drag car if you tune it for the conditions a carb might make a bit more power.

Evan,

When we used to build engines for my race bikes, around 1998 we started to make as much peak power with EFI as we did with carbs. Of course, we used manifolding that was different and some advances were made in fuel injector design.

With the advances made in ITBs, intake design, and fuel injectors along with much more powerful ECUs and comprehensive sensors than we saw 20 years ago, I don't see any disadvantage to EFI with regards to WOT.

https://youtu.be/CHLB-mkM5qs

I know that a lot more drag racing cars are using EFI these days too.

It's true, given the two scenarios, the carb will make more power at wide open throttle. Nascar LOST hp by going to EFI. Pro Stock drag racers LOST hp by going to EFI. And I'm by no means a carb fan at all. To this day I hate working on that god forsaken stuff, but they will make the most power. Driveability will be better with EFI, mileage will be better with EFI, tuning will be easier with EFI, and it will likely make more power everywhere else in the rpm range, but in that one area, at wide open throttle, the carb will out power the EFI.

There's a solid reason for it. Because the higher up in the intake runners you can start the fuel mixing process, the more homogenized the mixture will be, and the fuel has a cooling effect as it goes through the intake, too. Like I said earlier in this thread, put the injectors as high up in the intake tract as possible and it'll make the most power. Without a doubt. Might run like stink everywhere else in the rpm range, might be a bear to start when cold, but it'll make more power at WOT. Look at any of the current nascar or pro stock intakes and compare injector location to those on your street car. They will always be as high up as possible or allowed by rule. This isn't by accident.

Now, with all of that said, if you could stick the EFI injectors at the very top of the intake tract (much like the mechanical fuel injection that Porsche used in the race cars), you'd negate the carb's advantage, but not with the injectors spraying just an inch or two from the intake valve. There simply isn't enough time for the fuel to thoroughly mix with the air.

Nux -- I just happened to take a look at that post that you pulled off the 993 forum and that was actually my post from a long time ago. What I found interesting is that dyno graph is not what I saw on future dyno's. I had my ref flap actuator fail and went to the dyno (as I noted in post). Saw that the top end HP was down so tie wrapped the flap open. It was a few years later that I noticed that on that dyno that I did with res flap failed closed, my torque was higher in the mid RPM range (no idea how I happened to notice it, but I did). So I got a new actuator and headed back to dyno the next spring...

Bottom line there were mid range gains there. Pic below are the torque differences with res flap open <5.7k (orange), and closed <5.7k (blue). Had to pull off multiple dyno's so put into excel.

I am still puzzled by that original dyno. Only thing I can attribute is Hi/Lo settings of the actuator were mixed up when we were testing.

http://forums.pelicanparts.com/uploa...1614730734.jpg

Cool.
I should be ok seeing as my engine is a smaller 3.0

As for the TB ...I don't have one! I don't have the center sections.
That will be my next question!

I have a 60mm Ford TB, but I'm sure it will need bigger than that. I'm removing and tearing down a 996 engine tomorrow, I'll see what size it has. Again I won't really know what I'm looking at till my 964 intake arrives.
What size TB does the plastic intake have?

SDS is just called and is shipping my ECU back. :D
Brand new spec once I download the latest software and full data logging.

Ross and Barry at SDS turned it around in less than 2 days. :cool:

FYI,
for comparison the stock throttle body on 3.2 Carrera was 63mm the 964 3.6 is 68mm.

john

That's smaller than I thought.

It would be cool to be able to experiment with a couple different sizes of TB. I still think the 60mm Ford (4.2 F150) I have will be a bit small but they may have a few Ford sizes I can try that's the same mount pattern as this TB.
So far no luck finding an interchange guide to see if the bolt patterns are the same as others. I may have to take a trip to the local scrap yards.

Just measured a 996 3.6 TB and it looks like 73mm.
The Honda's have some different TB sizes in my range, might be a better option than a Ford TB.

I would like to find different sizes 65-75mm, but the same bolt pattern, so I can test them. Also some TB's you can buy aluminum spacers, which will be perfect as a TB base plate for welding to a new center section.

You could just use restrictors.....

Since you are looking at making your own cross over tube to mount the throttle body maybe you could make it so it directs the intake flow like the IPD plenums.

https://www.ipdplenums.com/

john

Get out of my mind!

I have a IPD plenum here that I'm going to be looking at. ;)

My 964 intake halves arrived last night.

I have to figure out the the stubs and center section details, might take a while as I'm super busy restoring several 914 2.0 Djet engines plus other projects this spring/summer. We'll see how much energy I have left over on the weekends.
A 914world buddy is sending me the stubs and fuel rails, not sure if I will use them but anything to help the design or build is a good thing. :)


The EFI install itself only takes a weekend, it's the crank trigger and intake fabrication that sucks up the time.
I could buy off the shelf... but where's the fun in that?

http://www.914world.com/bbs2/uploads...8729_thumb.jpg

BTW I can weigh these if anyone wants, one of the arguments is that plastic is lighter. This likely is true but these manifold halves are pretty light, I'm not worried about the weight for my build.

Intakes look good. Definitely watching and stealing all your good ideas. Ha ha.

Is this why you have an intake WTB in the Canada section? SmileWavy

Post or PM me your build details, happy to help.

Yes it is. Taking a 3 liter Weber carb and going with EFI. Likely with coil on plug. Also planning on fabbing a junkyard supercharger set up. Still humming and hawing over intakes and ECU’s. Did look at SDS. They are a consideration.

Steve Mc.

Sent you a PM

Things will progress very slow, as I've taken on several 914 2.0 engine builds, so likely this will be this coming fall/winters project.

But....My cheap $66 (Canadian with shipping) Ali-express 70MM TB arrived from China today and it looks good enough. This is a universal TB so it doesn't have extra holes and crap. I'll have to figure out how to do the throttle cable as it looks like the wheel take standard bicycle cable ends.

http://www.914world.com/bbs2/uploads...1619276176.jpg

http://www.914world.com/bbs2/uploads...1619276190.jpg

TPS mount doesn't line up with this bosch 3 wire TPS I have, but it fits the D shaft end. It will be easy to make a new mount plate and it will just be a bolt on mod to change the existing mount.
I'll also try a Honda TPS to see if it fits better.

http://www.914world.com/bbs2/uploads...1619276549.jpg

The huge bonus is it came with this 9/16" (1.5cm) thick mounting flange (with bolts) that I can weld to the custom center section I will making.

It has an idle stop, but no idle air bypass screw, so I'll have to crack the plate open a bit for idle or another option is to drill a hole in the throttle plate.

http://www.914world.com/bbs2/uploads...1619276734.jpg

http://www.914world.com/bbs2/uploads...1619276893.jpg

I wish I had 240 in my garage - then I might learn how to TIG (my attempts with a friend's set were what one might expect, though functional for their purpose). Does the manufacturer make smaller ones? Maybe ITB material?

It took me hours of searching ebay. amazon, aliBaba, wish, etc to stumble across this one. I found a bunch of TB's for Hondas, Acuras, Mustangs, etc, but they all had extra crap I didn't need.
This one is a universal TB that's not made for a particular car, I liked it because it didn't have stuff I didn't need.

Basically you'll have to spend the time going through AliBaba searching for "40mm throttle body" then "41mm throttle body" then "42mm throttle body" and so on and so on.

Good luck!