Advantage of 3.2 intake over 3.3 turbo intake?
 

I searched through this forum for carrera intake conversion trying to find out what the advantage is. The reason that I was looking is that I was thinking that there would not be a significant advantage of the 3.2 intake over a 3.3 intake with injector bosses under the iintake runners.

Is it for the longer intake runners?

Thanks,
Larry Ratcliff

The Carrera intake is popular for EFI conversions. The stock flat "pancake" 930 intake is not an optimal design when it comes to flow.
The intake port sizes are different on a Carrera vs 930 so you would need to address that issue.
Many have done EFI conversions using the Carrera manifold, someone will chime in with their personal experiences. Do a search using the 911 forum, a ton of info should come up for you.

I'm no expert but, the basics are that the 930 intake is designed for torque and the 3.2 intake is designed more for horsepower. Some obvious differences is the 3.2 Carrera intake has a significantly larger plenum area. The Carrera intake does appear to have longer runners but, hopefully someone that knows for sure can chime in to verify this. For forced induction applications, larger plenums are more desirable for creating horsepower as they are less of an intake airflow restriction. With the Carrera intake you will probably see a bit less peak mid range torque, and you will be able to maintain torque/hp higher in the rpm without quite as much of a drop off on the top-end. For forced induction, IMO it's worth it.

Based on what I am hearing. It sounds like the carrera intake would cause more of a lag than the stock intake. I would take low end torque over high end HP any day for drivability. It would be very interesting to see a comparison between the two intakes on the same engine ... both torque and HP curves.

The carrera will flow more than the 930. Iirc the 930 manifold is only good for 500bhp at the crank, after that it is losing you max power.

The thing is though, there won't be any significant or detrimental decrease in low-end torque. The Carrera intake isn't exactly a short runner manifold like you'd find aftermarket for a Honda or anything that would completely kill the low-end. It's just that the 930 manifold is so restrictive. Just remember, torque at higher rpm equals more hp, which gets more work done. Stump pulling torque at 2-3k rpm doesn't necessarily make your car faster if your hp/tq is practically plumetting off the face of the earth on the top-end. ;)

From what I recall in my younger days of tuning, a shorter intake runner lends to pulse tuning at high rpm, longer intake runner is required for low rpm. On the other hand exhaust headers are the opposite. I have a book on manifold and header design which I could reference.

The 930 intake manifold shape and size appears to be a space compromise as result of the amount of other "stuff" needed in the engine compartment: air plumbing to/from the turbo, intercooler, air metering box, priority valve, air filter housing, etc.

Jim

Yes that is correct due to the size and space occupation of the CIS assembly atop the manifold. Hence the reason the 3.2 manifold is a good excuse for an EFI conversion.

If I had kept my 965, this would have been my next mod as the Tec3 sitting next to me needed a home and was calling to my car. Still needs a home, but one is coming soon.....

The Turbo manifold absolutely sucks for even air distribution.
Uneven air distribution = uneven AFRs from cylinder to cylinder, etc etc

The world is waiting for a miracle manifold for CIS users.....

The only way you can accurately compare a Carrera intake to a stock 930 intake is by doing an EFI conversion using a stock 930 intake - both on the same engine. I have never seen that done on the same engine.

What you choose depends greatly on what your goals and budget are. Carrera manifolds go for around $250-500 depending upon condition and EFI equipment.
The 930 manifold will support 500HP so it isn't a horrific piece.
The Carrera manifold might better lend itself to a 400+HP application where head work is going to be done (you must do something to address the difference in port size from stock 930 heads and stock Carrera manifold).
The Carrera intake makes an EFI conversion easier if you plan to use the Motronic system of the 3.2L engine.

Good point. I have.

A local guy had a MOTEC EFI conversion done......with the stock manifold. He was disappointed in the results. 420 RWHP I believe was the max which is right about 500 FWHP. I don't recall the head work/porting etc that was done.

Realize that this by itself is not a damnation nor approval of a stock manifold, but rather a potential showing of the limitations that a stock manifold will produce - when this engine was compared to a nearly identical engine with a Carrera manifold.

I believe the Carrera manifolded engine had another 40hp.
YMMV, take this for what it is.

The longer runners bode well for more low end torque, you guys, think volumetric efficiency on a blown car. The Carrera intake will outflow the restrictive 930 intake.

I'm not trying to argue that 930 intake is superior, but Brian has a good point - Anyone who uses the Carrera intake needs to do something about the port size.

And I bet 99.999% of them ended up enlarging the port on the head. The engine becomes a much better air pump; hence more power (assuming everything else is the same).

But now its a much more costly route...

I was under the impression that shorter runners were better for low rpm torque and longer runners produced better high rpm HP hence the design of Varioram.

Waiting for experts to chime in, but I do believe that longer runners are good for torque, while shorter runners aid in high RPM HP. That is why most systems out there, varioram included, will effectively cut the length of the runners as the RPM's go up. I think that the main reason for using the Carrera intake is the simplicity of running the fuel rails (you can just buy existing, proven 3.2 rails and lines), coupled with the better flow characteristics and port sizes, and also, because it has become the norm. It's kinda like the engine equivalent of a ducktail spoiler for an early car! Plus, the basic runner/plenum design is very similar to later manifolds, like the 964/993 cars.

The design of the 3.3 manifold seems to have been compromised more for packaging issues than for sheer flow. It was the only way they could get the CIS hardwar, the IC, A/C, smog pump, etc under the lid. They probably figured that the positive manifold pressure would compensate for the intake's shortcommings.

An interesting test would be to run a non-turbo motor with an EFI/3.3 manifold, vs the 3.2 Carrera. You would really see the differences then.

On another note, it is intersting that the TPC 993 supercharger package uses the basic 3.3 pancake manifold design as well. Packagin needs, I suppose.

Actually Garen and SCHNELE I think you are right- I had it backwards.

It's two things:

Balance between runners
CFM capacity

Nope, Jim, you were right. Long runners shift the Volumetric Efficiency of the engine towards the higher end of the RPM range. Look at it from an inertia perspective; a column of air at rest, tends to stay at rest. A column of air in motion, tends to stay in motion. Longer runners increase the cylinder filling efficiency at high RPM's......kind of a ram effect. If you look at the Can-Am cars of an earlier era, you would find the normally aspirated engines were tuned to the track they were running. High speed tracks like Road America, the engines had high stacks. But on shorter tracks, where exit speed made all the difference, short runner tubes were used.

If anyone has any interest in the flow numbers from Carrera manifolds, here's a link to an old thread I started when I was building my engine:

http://www.turbo911.org/forum/forum/forum_posts.asp?TID=1126&KW

It doesn't compare 930 with Carrera manifolds, it only compares Carrera manifolds before and after Extrude Honing.

F1 car 19,000 rpm: 2.5" intake runners

Buick V6 FWD automatic 2500 rpm: 17" intake runners


Porsche V-ram and non V-ram have the same peak HP, but he V-ram has more mid range torque resulting from Porsche adding intake runner length as seen on the top of the intake manifold.


Overview: Exceeding 100% volumetric efficiency on a reciprocating internal combustion engine requires "pulse" tuning, among othere things. This "pulse" occurs when the moving column of intake charge is stopped by the intake valve upon it's closing, the moving charge column bounces off the back side of the intake valve and reverts the othere direction up the intake runner leaving a region of low pressure behind itself. At an optimal intake runner length the reversion wave goes right out the end of the velocity stack, at which point the differential pressure drives new charge back down the velocity stack. If the intake valve is open when the reversion wave arrives theree is an opportunity to impact the cylinder with charge exceeding atmospheric pressure. There is really lots of stuff going on, more than meets the eye. A 930 intake would be suited for an RPM well beyond the engines mechanical limit, except that there IS NO PLENUM eithere...

I'm another "local guy" and have a Motec EFI set up with the 3.2 manifold. 512 hp to the wheels at 1 bar. So it may be that the 3.2 is worth an extra 100 hp or so....Of course, I don't know what kind of cams, etc. the 930 manifold guy is running, so there may be other variables.

512 ?!

Sweet mother of God!
Tell us the details or send a PM with more information on your setup.
Dynamometer chart if you are willing to do so -

I used to have my build in a readily cut-and-pastable form on the old Turbo911 board that Clemson Chan ran, but when they switched over to the new set-up, apparently the old "registry" didn't come over with them. I was car # 138.

Basically, it's a 1978 930 with a 3.6 crank, 98mm Mahles (chamfered heads to fit), Factory GT2 Evo cams, hand-fabbed exhaust, fancy springs and retainers, Raceware studs, TS04 turbo, Motec 48 Pro, blah, blah, blah. Built by Bob Holcombe. Tuned most recently by Chris Powell, and dyno'd at Carb Connection. Also has Big Reds up front, a G-50 with Quaife, etc. Got the sheets at home, but Chris/Alex can tell you all you want to know. Took quite a few whacks to get that Motec tuned right, especially with cold start. My goal was 500 to the wheels at one bar, and we did it. Of course, by now, that's not close to leading the pack any more, but it will have to do. I think my next mod of any significance is going to be to that turbo. There are better ones out there now.

512 is huge. I'd call that pack leading ;-)
Hopefully you have a good amount under the curve so it isn't a peaky hell beast.

Well, it's a freakin' slingshot from 3-4000, which is great for scaring the crap out of a passenger and generally clearing out the synapses but can be a ***** to control at a track. I'm thinking a quicker spooling turbo might help that. I'd like more torque earlier, and more torque later. I'm greedy that way ;)

Bruce - 500+HP at 1.0bar is huge.
How do you qualify that the 3.2 manifold is worth 100HP?
Were you previously using a 930 intake on the same motor?
(I know several 930s using stock intakes that are going 430-440HP to the wheels.)

512HP to the wheels is a big number that would likely not be supported by the stock pancake manifold, but by how much? That is the $34,000 question. You've built a VERY fine engine that can get you those numbers at 1.0bar.

I think in order to accurately and directly answer the question posed we need to know what the expectations are for the engine used.
If the goal is 350HP there may not be a significant need for the Carrera intake. If the goal is "Bruce" power you definitely need all the advantages available.

I just figured that from Craig's post above:

"A local guy had a MOTEC EFI conversion done......with the stock manifold. He was disappointed in the results. 420 RWHP I believe was the max which is right about 500 FWHP. I don't recall the head work/porting etc that was done."

Since I was also a "local guy" to Craig, I thought I'd chime in.


Anyway, if that's what a Motec engine with a 930 manifold can do, I figured the manifold change is worth around 100. But, as I said, that doesn't account for possible variables (including boost--dunno what that 420 hp guy was running for boost...).

This is a project that got out of hand. Bought a 930 on the servicing shop's say so (last time I EVER do that). Crank had been turned twice, pistons installed upside down, rod bearings shot. Had to split the case, and all the rest is basically "while we're in there" stuff. Did try to use a TEC ecu, but never could get idle and cold start right, so went with Motec.

Then I got FM-10s, custom-valved Bilsteins, the right torsion bars, Charley bars, etc.

Runs nicely now, though. Still got some "rawness", but good, solid power. G-50 wakes it right up, as well, and the Wevo short shifter matches up with it nicely. I've never driven one, but I guess it might be similar to a '89 930, although maybe lighter and with more oomph. I've driven a '94 3.6, and that felt much more civilized and heavier.

The money and patience it took to get here, however, qualify me for instant membership in the Idiot Hall of Fame. So I don't talk about the process too much.

Wow, 512whp from a 3.5l is pretty good @ 1bar considering the TS04 turbo. That's only a ~58mm turbo, and I would tend to think it would have to be something like 67mm+ to come close to 500whp @ 1bar. How high are you revving that thing Bruce?! ;) Sounds like a fun car!

Not an extra-high redline, actually. I am interested in seeing what a more modern turbo could do, though.

Displacement with a 3.6 crank and 98mm pistons works out to a 3.45, I believe...

Now I'm now expert, but from the hands-on-a-dyno sheet/apples-to-apples-research I've done, the Carrera manifold can be solidly said to add about 40hp. There....I've made the commitment.

Of course it depends on several other things, but if you had to isolate, this is the increase. BUT.....more than that increase, you have increased CFM ("flow"), and above all - equal distribution to each cylinder.

512 is kick-a$$ power.

Edit:
Do you have a picture of your 930 to post, Bruce?
Since I've also had a ton of work done at Chris', I must have seen your car at some time...

:D Thanks for making my day:D

I have my application in for that same Hall of Fame due to a M48 conversion and a rebuild with many of the parts similar to yours.....The job is still a couple of weeks from being finished...but I've paid for it already so my prospects of being accepted to that Hall of Fame are pretty good...

The Ts04 is pretty ancient stuff, so I'm sure there is a decent improvement to be made in initial boost response and transient response with a similar sized and newer turbo. Oh well, whatever works is what I say, and it sounds like your setup certainly does! :D

Eventually, most 930 owners will be inducted :D

I received my letter the other day.

I became a member just a few months back.
It says here (in my hands, I hold the certificate):

"Special honors always go to those who did not get a PPI" :p

I am a member of that club for sure
I have owned my car for 7 years and have not even heard it run
It has eaten much time and all my money
Hope to make it all worthwhile by spring

I am not only a member but I am running for president.

Thanks for all of the great responses guys. I had already purchased a complete 3.3 turbo intake system for what I thought was a pretty reasonable price of 900 bucks. It included the complete intake, intercooler, turbo, etc... So based on my goals I think that a factory turbo intake will get the job done. My car only weighs 2300 pounds so making 500 HP at the rear wheels is not really necessary. Already with the 3.6 most people I know wont even ride in it any more. I would be thrilled to death with 400 HP.

I am going to use the factory manifold with a haltech efi conversion. I wont run more than 1 bar but I might run around 8.5 :1 compression. I will probably do all this on a 3.4.

If it hits around 400 hp I will be thrilled.

8.5:1 seems a bit much for an aircooled engine at 1 bar.

David has a legit concern. Do you plan to track it or just for street blasts? I think you'll want to keep boost down to .7-.8 if you bump up compression that far. Seems like 8:1 is the sweet spot for off boost response and reasonable boost. Remember that it is head temperature as our defining variable that has little solution. You might get better with some of the billet parts like Nickies for temperature transfer.

Has anyone tried the Rubbermaid solution on a 930? Its from some of the old timer racers (and I say that with respect nothing else) on the board.

Head work will get you 400RWHP using the stock 930 manifold with stock 7.0:1 compression at 1.0bar or less. If you bump the compression to 8.0 you can get your 400RWHP with less boost and a little better response.