SC Heat Exchangers v 3.2 HE's, cheep upgrade?

[911st]

I was looking through my old dog eared copy of Bruce Anderson's book on modifying Porsches it it seem the tubes were enlarged with the 3.2 Carrera.

Can anyone confirm this?

3.2 HE's seem to be so cheap. I wonder if they could be considered a low cost way to make more HP on an SC w a cat bypass and 1/1 sport muffler???

For less than the price of oil lines for an SSI conversion one could probably buy a set of 3.2 HE's. Might add to peak HP but not low end response as much as the SSI's.

Just a thought.

[SCWDP911]

no one ever commented on this... any validity to the proposition?

[911st]

We probably just need someone to measure the ID of a set of SC HE's and 3.2 HE's.

If there is a difference, I wonder which one the 930 got?


Probably the best is to just add a cat bypass and 1/1 sport muffler. One a 3.2 SSI's do not add much except a little bump around 2500rpm over stock HE's. Not sure about SC's.

[Tyson Schmidt]

There is definitely a difference.

Problem is, the SC has 35mm exhaust ports and the 3.2 had 38mm ports.

So to fully realize the benefit you need to open up the exhaust ports on the SC heads. You probably will lose some street driveability doing this.

[mb911]

from what we have measured only the flanges are larger everything else is the same just like ssi's

[911st]

Ben,

On a turbo thread someone just said the SC and turbo had a 35mm ID tube and the Carrera 3.2 a 38mm ID tube.

I thought the stock 3.2 HE had larger ID primary tubes than the SSI's.

Are you sure or how can we confirm.

Thanks.

[Flat6pac]

The Carrera exhaust is about 4mm larger so it flows better. On a US 80 to 83 if you knock off the head insert of the Carrera exhaust (3 small spot welds, air chisel does the trick) and it bolts right up. Take the carrera cat knock it out inside and a Carrera muffler gives a warm sound, or you buy a stainless from me.
You need to richen the mixture
On a 78/79 you need to grind the flange thickness so you dont have to change out the studs, knock out the insert and youre good to go

Bruce

[James Brown]

wow wonder if anyone has done dyno reserch on this (I doubt it) but it does sound good. I have the euro pre muffler and a dansk sport. runs good like this but for $100 bucks or so, it might be worth the swap for the 3.2 HE's

[mb911]

Originally Posted by 911st

Ben,

On a turbo thread someone just said the SC and turbo had a 35mm ID tube and the Carrera 3.2 a 38mm ID tube.

I thought the stock 3.2 HE had larger ID primary tubes than the SSI's.

Are you sure or how can we confirm.

Thanks.

I have measured countless ones they are the same after the flange. But You can only take my word on that for what its worth.

and yes they will bolt right up if the gasket protector is removed

[RarlyL8]

Keith,
I've got a wall FULL of exhaust systems. The SC and Carrera have different flange size and the "primary" stubby tubes are of course larger to accommodate the flange. After that they are all the same - SC, Carrera and yes 930.

One indication that this is the case is the complete LACK of anyone "upgrading" an SC or 930 to Carrera exchangers when opening the exhaust ports.

[911st]

Brian,

Solid info, thanks.

Are they all 1.5" tubes like the SSI's?

K

[Flat6pac]

Then if all is the same why not be buying SSI for the C-2 which is specific for C2 but will fit for all or are they the same size tubes as the 2.2 SSI? For the money SSI gets why wouldnt he be building specific to the need of the customer?
Bruce

[911st]

My understanding is all SSI have the same size tube. Just different tops to fit the motor specific ports.

Running them on a 3.6 is a shame. I know some respected tuners do so but it has to leave well in excess of 10hp on the table.

I guess in my opinion the same applies to running them on a 3.2 but to a lesser degree. They are equal length, good for low end, sound great, and are a piece of art.

[RarlyL8]

All SSI tubes are the same size. Much more cost effective no?
The OEM H/E's and SSI are ~35mmID.

[emcon5]

Originally Posted by RarlyL8

Keith,
I've got a wall FULL of exhaust systems. The SC and Carrera have different flange size and the "primary" stubby tubes are of course larger to accommodate the flange. After that they are all the same - SC, Carrera and yes 930.

You sure about that?

hp difference between headers and ssi

Originally Posted by Steve@Rennsport

The SC & Carrera HE's LOOK the same but the tubing diameters are different,...

SC's have 38mm primaries (1.5") and Carrera's have 41mm (1 5/8") ones. Needless to say, thats a substantial difference and helps explain why SSI's do not make the same gains on the 3.2.

I also seem to recall something on the InstantG Page mentioning that SC exchangers were not suitable for 3.6 swaps because the primaries were too small, although I can't find it now.

[RarlyL8]

Yes I am sure about that.
The "primaries" are those short tubes that connect the flanges to the rest of the system. Remove the heat exchangers and cut one of the tubes in half. Measure the ID not the OD. It's less than 1.5".
SSI's don't perform as well on the 3.2 because they are better matched in size to the SC. The HP bump for the stock Carrera vs the stock SC comes from 0.2L extra displacement and EFI.

[Harlan Chinn]

I'd do the SSI's. They look great (stainless) and depending on muffler configuration you'll get a bit better performance or at least it'll sound like it. I went the conservative route and did the 2 into 1 stainless exhaust, but you might get slightly better performance going 2 in and 2 out. Louder than stock, the car will sound like it has purpose.

[911st]

It is very interesting that the 3.2 and SSI primaries are basically the same ID.

If the bump in power we see is at about 3000rpm with SSI's on a 3.2, a properly designed set of headers should be able to move said increase to a more point that might show more benefit like somewhere between TQ and HP peak.

Said bump seems to be about a 5% increase in VE at a given point.

On a 3.2 at 3000rpm that is about 5hp.

At 6000 rpm that would be about 10hp. This is what long tube 1 5/8's seem to do on a 3.2.

[emcon5]

Originally Posted by RarlyL8

Yes I am sure about that.
The "primaries" are those short tubes that connect the flanges to the rest of the system. Remove the heat exchangers and cut one of the tubes in half. Measure the ID not the OD. It's less than 1.5".
SSI's don't perform as well on the 3.2 because they are better matched in size to the SC. The HP bump for the stock Carrera vs the stock SC comes from 0.2L extra displacement and EFI.

Just a follow up on this, had some 3.0 and 3.2 HEs side by side last week, and they are definately NOT the same size. The primary is larger on the 3.2.

By "Primary" I am talking about the pipe from the flange at the exhaust port to the collector where the 3 pipes merge in to one pipe, either just before the crossover pipe on the passenger side, or the cat on the drivers side.

The crossover pipe and cat are the same, but the HEs themselves are not.

At the port end, the ID was ~35mm vs ~38MM. I didn't have something that could accurately measure inside the collector, but I found the largest wrench that would fit in the port end of the 3.2 exchanger, and it would also fit in each of the 3 pipes on the collector end. In the 3.0 exchanger, it wouldn't fit in either end, in any of the three pipes.

[911st]

HD,

Thanks for the info. Good work.

I am now confused again.