964 Engine rebuild questions

[ALEX P]

Thanks Magnus, the car isn't fitted with a lamda other than the one that is there for the AFR gauge so I don't know if it would throw the ECU off.

Yes the car was mapped on the rollers (see post #73) and agreed it would need remapping if the injectors were changed but that's a good point that if they were limiting the performance it would have showed up.

Maybe the 300bhp max limit for 964 injectors is a red herring.

[ALEX P]

I'm having a bit of an exhaust re-think at the moment for a number of reasons one of them being the headers are sitting really low on one side and the car has some ground clearance issues. I am going to raise the rear ride height slightly but it still hangs pretty low.

I might also have a go at a new silencer to give me a few more options.

Final reason is that it's a pretty chilly place to be this time of year and I don't want a bit of cold to stop me using the car so may add a bit of simple heat back to the car. I must be getting soft in my old age!

The obvious headers / heat exchangers option is to use 993 ones with the flanges flipped and they have been proven to give very good power figures on some cars. I've borrowed a set to use as a template (cheers Jev) but having a measure the primary pipe internal dia is approx 1.5" and the outside diameter is approx 1.6".



My current headers while being cheap and cheerful with poor merge collectors (of a sort) have 1.75" internal dia and approx 2" outside diameter. Headers shown below and Magnaflow silencer shown in link.

964 Engine rebuild questions

This is quite a size step down which bothers me a bit and if it won't allow the engine to breath properly then maybe it's not the way forward. I always thought as a rule of thumb that 1.625" was the 'norm' for a 964 and maybe 1.75" for 3.8 or tuned cars which is why I'm a little surprised that 993's have 1.5" bores.

I realise that changing the exhaust will require a remap but am clearly reluctant to do the work and make the change if I end up losing power/torque.

Can anyone who knows anything about exhausts offer any advice?

[Spenny_b]

Hi Alex, wow, blast from the past! You well?

What with you, RobT (on Rennlist), me and a couple of other 964 rebuilds going on, there's a few of us in the SE with interesting projects underway (albeit yours is now a runner. Git!)

Re your headers, yes, the diameters you mention sound curious - wonder what the 993RS ran?

If you're feeling flush, then Joe @ BTB Exhausts makes absolutely top notch systems - my pal who's doing all the mapping work on my build swears by him as the only person of the many he's tried over the last 20yrs, that acknowledges and actually builds the primary and secondary lengths that Steve wants, to the tolerances he specifies. Not cheap, but....

He's a motorsport guy rather than a Porsche specialist, but I see he now also advertises in the Porsche press, so guessing he's now done done a number of systems.

Cheers
Spencer

[ALEX P]

Haha, yes all good thanks, hope life is treating you well too.

I've got a pic of a 993 cup set up (below) which is a similar setup as stock 993 but no heat required. I don't know what dia the pipes are and I find it quite interesting that people make quite a big deal about equal length headers when the 993 aren't even close.

I love the headers offered by s-car-go, washburn etc etc but my pockets really aren't that deep and although a lot of work has gone into them I do find them unnecessarily expensive, quality costs hey!

I guess one option is to hack mine up to try to reduce the depth they hang and add some burns collectors or buy some OBX or similar and chop them up.

The 993 heat exchangers seem a nice easy solution but I don't know if it will stifle the engine?

[safe]

993 and 993RS has the same exhaust. The cup is also the same, but without the heater box around it.

I emailed 9 Meister about upgrading my 964 3.6 engine. Exhaust was waaay down on the priority list if it has a race cat or a cat bypass, that surprised me. On the other hand i have seen engines perform very well with stockish exhaust.

[martensson]

So Magnus, this it where i find you hanging around

As someone mentioned earlier, the stock exhaust on a 3.6 measures ID=1.5"
Just swapping to a 1 5/8" has to make a difference. Going even larger....i don't know?

Are there any tests that show performance differences between stock, 1 5/8" & 1 7/8"?
Keeping the car as a daily driver & track-day car & slamming on a 1 7/8", i think might do more damage to the power band rather than good? Any thoughts on this?
Together with a light weight bottom end you will gain top end power, but lose torque.

So can we agree on a suitable size so i can start fabricating my headers



About issues with fuel, I agree with Magnus regarding swapping/not swapping the injectors. The ECU can only compensate for minor changes & in cases where you don't remap the ECU, you can just tweak the fuel pressure & install a wide band lambda / AFR-gauge as a very cheap safety device to keep track of your mixture.

Injectors 964 part # 911 606 120 01 have the following BOSCH # Bosch 0280150731 giving the following specs:

18.4/lb injectors and flow 194cc @ 3.0 bar, with a 21° spray angle for the cone characteristics. The connectors are EV1 type.

@3.8 bar (55.1 psi) = 300-320 hp



Also found this thread stating good info regarding the 964 injectors & fuel pressure, where Bill Verburg has a good answer with interesting facts

964 Injector Flow Rates ?

hope this helps

[ALEX P]

Thanks for the comments Magnus and Martensson - interesting read on the injectors. One thing that confuses me slightly is why run with stock 964 injectors that are near the edge of their performance envelope if you can run with injectors with a higher potential flow rate such as the 951 ones from a 944 turbo and run them at 80%?

I've done a lot of reading on the exhaust front. There are two good threads below that are well worth a read. It all seems to boil down to how deep your pockets are so if you are handy with a welder and have some time then fabricating your own is a really good option. I may have a go at drawing some up and see where it takes me........

Some of the fairly highly rated headers for middle money such as the George headers seem to only be available in mild steel which surprises me, as a minimum I would want stainless and for the sort of money the top end headers I would want titanium!

George's headers vs. Bursch

What Headers for my 3.8 RSR build??

[johnsjmc]

I used 993 HE,s with a double 2.5 in/ out muffler. then added small resonators in the outlets. I think made by magnaflow It used an internal x design which allowed easy inlet outlet position choices helpful when fitting to the body.
Homebuilt copy of Steve Timmons "happy crab" . Really modest cost perhaps $500 plus the used HEs I found on ebay at the time for maybe $300 . No idea of parts prices today but
Stock 3.6 from a 91 in a 1980 SC. In a car I did in about 1997

Seemed to work extremely well and fit the early 911 chassis. Noise wasn,t bad at all, ,no unusual resonance or complaints from sensitive passengers but no cats if it had to be smogged. Not required here in one that old
Heat was great with the 993 HEs .
I personally feel the biggest improvement over stock is achieved by muffler choice before it would be by header tube dia. increases /mods.
If you need cats then the stock cats work but muffler space in the early chassis then becomes hard to find. Without mufflers the stock cats are very load.
I think small tube 1 1/2" will support 100hp per L.
Note : When flipping the flanges on the pass side . There is one cyl .head stud which becomes difficult to get a nut / wrench on . I had a small exhaust leak at the port which was difficult to seal because the one bolt.

[ALEX P]

Hey John, mine was a 14" Magnaflow with 2.5" in/out too (see post #64). They work really well and cost peanuts as you say. Only difference with mine is instead of 993 h/e I went for a cheap set of 1/75" dia headers.

They are noisy but I made a pair of perforated inserts that fit in the tail pipe to quiet things down when needed.

I had a bit of spare time so was playing around with drawing some headers. They are reasonably equal length and made only using off the shelf bends. Bit rough and the 'S' bend on the middle pipes probably isn't ideal but wanted to keep it simple and stick to the 'off the shelf' philosophy. All of the bend rads are the same with 1.75" dia pipe and a 63.5mm centreline radius.

Don't really know where I'm going with this but maybe if they were tweaked to the right length with a pair of slip on merge collectors then maybe I could use the 993 h/e I have a s a jig to knock something up.

[johnsjmc]

I would just use the 993 HEs as is and you have good heat and good power.. I don,t worry too much about equal length on a street car. I somehow feel the 2 long pipes optimize two cylinders at low RPM and the two short ones optimize at the top end with the med pipes being optimum for mid rpms.
The averages end up being good over all rpms.
I used a 2.25 in out muffler as that was available off the shelf when I was looking.

[ALEX P]

Problem is the 993 h/e I have got with the flipped flanges are borrowed so I've been looking for a used set for a while but they're all silly money and would need modifying / flange flipping anyway. I've seen a couple of sets in the U.S. but shipping costs and import taxes make them pointless.

Heat is easy enough to add to most headers, just weld a box round them.

Thinking completely outside the box, can 996/997 headers be adapted to run on 964 engines?
I know the port is a different shape but could always cut off the flanges and weld on 964 flanges on something like this?

I only ask as when I was searching for h/e, this style of 997 GT3 Cup header popped up at sensible money!!!

[safe]

For heat you can always get a cheep petrol heater from China....

2KW Air Gasoline Heater 12V similar with Webasto park heater-in Mounts & Holder from Automobiles & Motorcycles on Aliexpress.com

[johnsjmc]

I had no idea the 993 hes were bringing such money today I paid about $275 for the last pair I bought about 2006. I see them on ebay now for $800 plus. Steve Timmons shows them on his site at $650pr with modified flanges. Or I think $450 pr unmodified. Shipping to the UK can,t be that awful can it?

[Spenny_b]

Originally Posted by ALEX P

Problem is the 993 h/e I have got with the flipped flanges are borrowed so I've been looking for a used set for a while but they're all silly money and would need modifying / flange flipping anyway.

Alex, give my pal Brian Stageman ("911 Spares") a call on 07956 911999 (love that number...2 x references to Porsches and the Emergency tel number, haha)...by all means say I pointed you in his direction.

He strips 911's for parts down here in Kent, he's a great bloke with tonnes of parts from various vintages - I'm sure that if he doesn't already have various sets now, he probably will shortly (or may be able to source some for you)...doesn't remove the need to flip the flanges, but hey, another option for you.

Cheers
Spencer.

[ALEX P]

Originally Posted by safe

For heat you can always get a cheep petrol heater from China....

2KW Air Gasoline Heater 12V similar with Webasto park heater-in Mounts & Holder from Automobiles & Motorcycles on Aliexpress.com

I have seen those and the Webasto heaters but never really felt comfortable with them in the frunk in a closed compartment with the fuel tank. Silly really but I'd be happier with a bean can welded round the exhaust. I also looked into electric heaters but they can't muster enough power and need more amps to be any real use.

Originally Posted by johnsjmc

I had no idea the 993 hes were bringing such money today I paid about $275 for the last pair I bought about 2006. I see them on ebay now for $800 plus. Steve Timmons shows them on his site at $650pr with modified flanges. Or I think $450 pr unmodified. Shipping to the UK can,t be that awful can it?

Yep, a lot of parts like this are silly money now. Shipping to the UK is around $150 - 200 then add 25% for import tax + handling fee for the UK courier company (seriously) and before you know it you are easily over $1000 and for that much I'd rather make my own!!

Originally Posted by Spenny_b

Alex, give my pal Brian Stageman ("911 Spares") a call on 07956 911999 (love that number...2 x references to Porsches and the Emergency tel number, haha)...by all means say I pointed you in his direction.

He strips 911's for parts down here in Kent, he's a great bloke with tonnes of parts from various vintages - I'm sure that if he doesn't already have various sets now, he probably will shortly (or may be able to source some for you)...doesn't remove the need to flip the flanges, but hey, another option for you.

Cheers
Spencer.

Cheers Spencer, I bought a used 3.2 drive shaft/CV joint from him a few months ago. Maybe I'll give him a call. I have found a single RH 993 h/e in the UK but didn't want to press the button unless there was a LH around.

[safe]

Originally Posted by ALEX P

I have seen those and the Webasto heaters but never really felt comfortable with them in the frunk in a closed compartment with the fuel tank. Silly really but I'd be happier with a bean can welded round the exhaust. I also looked into electric heaters but they can't muster enough power and need more amps to be any real use.

I understand, but almost every new diesel car (they take for ever to get warm) sold has them factory mounted now, at least in cold weather climates.

I have a small HE welded to my secondary pipes, the resulting heat is slightly warmer than ambient...
Electric suck even more.

[ALEX P]

The thing I can't get over is that diesel doesn't ignite like petrol and the tank isn't in the same compartment as the heater. The exhaust is 'free' heat however convoluted the path to make it usable is.

I made an electric heater using the elements from two 12v travel hairdriers. The result was luke warm air but not good enough to provide any useful heat.

[safe]

Originally Posted by ALEX P

The thing I can't get over is that diesel doesn't ignite like petrol and the tank isn't in the same compartment as the heater. The exhaust is 'free' heat however convoluted the path to make it usable is.

I made an electric heater using the elements from two 12v travel hairdriers. The result was luke warm air but not good enough to provide any useful heat.

You can get a diesel powered one and have small separate fuel tank. These things were common on old VWs, I have asked around with old mechanics and they say the same thing: unreliable, but safe.


But I think you only have one good option that suits you, the 993 HE. I have a pair waiting for me to get the time to install them on my 3.2. I think I paid €500 for them, flipped and ready.
For my 964 3.6 I might keep the stock exhaust, they seen good for at least 320hp anyway and there is better ways to spend the money, head work for example.

[Costa P]

The modern heaters are widely used to safely and reliably heat commercial vehicles, ambulances etc as well as for marine applications. They have very fancy control systems to comply with all the safety regulations.

My 0.02, stick with the reputable brands.
Example the Eberspächer Airtronic M is compatible with gasoline....which means no need to install a separate diesel fuel tank!

[Trophy]

I have a set of 993 Headers at home gathering dust if anyone is interested.