3.6 964 Project Engine - ideas wanted

[matty74]

Bill, any update on you project??

[billjam]

Originally Posted by matty74

Bill, any update on your project??

Picked up cleaned crankcase and heads with new guides today.



Triumph Daytona 675 throttle bodies arrived earlier in the week so I have been pondering mounting and linkage options.
Manifold is pretty straight forward. Actually there will be six separate "manifolds", as per rough setup in pic below. I made up 18mm insulating spacers and 8mm aluminium mounting flanges using an old plastic inlet injector body as a template on my trusty woodworking router bench. The spacers have O-ring grooves both sides.



The tube is 50mm OD, 3mm thick. This is 44ID which is exactly the same as the throttle bodies ID. I will port the inlet ports from 42 to 44mm to match.
For mounting the throttle bodies, the six OE rubber sleeves that connect the gigantic 964 inlet manifold to the injector mounts just happen to be the correct size to fit the underside of the throttle bodies and the 50mm tube. Too easy!



Injectors are next on list to sort out. I doubt that the Triumph injectors are going to flow enough, so I need to find larger capacity injectors of same physical size, or I need to go to something more commonly used on Porsches and build in some injector mounts on my inlet tubes (most likely). I don't have the original injectors for this engine, but I do have the fuel rails.

No progress yet on coil packs (pic above has Toyota Kluger coil packs fitted) but I am still undecided on which type to use.

I am not changing the head studs. Fromwhat I can gather, standard OE steel studs seem to be adequate for non-racing applications.

Now that my heads are cleaned up, I can see the ceramic inserts that Tyson referred to in my post 1-3/4" headers on 964 ? I don't see any way to do much with the exhaust ports except for a bit of cleanup just under the seats, around the guide and at the exhaust port.

[billjam]

Xmas sort of interrupted progress but I have made a little progress with the ITBs.
I have ported out the Triumph throttle bodies to 44mm on the bottom side to match butterfly diameter and diameter of the al tube I am using for the intake runners. They were oval shaped to suit the Triumph head ports I think.
Got some tube bent during the week so I could fabricate the outer runners with 35mm offset. Cut it up today and nearly ready to weld. Just have to figure out how long to make the runners. They are way over-length in the pics below.

[DW SD]

Looks nice! Do you have that much clearance above? Will this go in a 911 engine bay?

Doug

[Walt Fricke]

Bill

Porsche curved the end two tubes on its manifolds when it switched away from the Solex. The available Webers (and then Zeniths) had a different center to center spacing than the 911 ports, so the manifolds got changed.

A friend who had a flow bench and wand confirmed what one might expect - the center manifold flowed better. Not a huge difference, I think, but measureable. It is a shorter path, and a straighter shot.

One of the mysteries of Porsche design, to me, is why Porsche did not have Bosch make its MFI throttle bodies on a wider center spacing. Only thing I can think of is that they wanted to use the same air filters. I don't think there is a clearance issue with the #3 or #4. Weren't for the Solexes.

Am I right that these Triumphs could be spaced apart fairly easily? Mostly some modification to the connectors for the butterflies?

On a related aspect: Usually one sees throttle bodies whose bores are larger than the port sizes. So the runners are tapered. I have assumed this was intended to increase velocity at the port. Guys with flow benches and lots of engine modification experience are always cautioning us not to make the ports too large.

You have read all this too, I am sure. Could you share your reasoning for using straight tubes (beyond the fact that I don't suppose one can purchase or easily fabricate tapered ones) and believing they will work well?

A quick review of Smith and Morrison's text did not uncover discussion of the relationship between TB bore and port size. Length of induction seems to get the most examination. There is a short mention of a Jaguar slide valve system, where the manifold tubing looks to be equal to TB bore, but is not related to port size.

Walt

[billjam]

Originally Posted by Walt Fricke

A friend who had a flow bench and wand confirmed what one might expect - the center manifold flowed better. Not a huge difference, I think, but measureable. It is a shorter path, and a straighter shot.

One of the mysteries of Porsche design, to me, is why Porsche did not have Bosch make its MFI throttle bodies on a wider center spacing. Only thing I can think of is that they wanted to use the same air filters. I don't think there is a clearance issue with the #3 or #4. Weren't for the Solexes.

Am I right that these Triumphs could be spaced apart fairly easily? Mostly some modification to the connectors for the butterflies?

On a related aspect: Usually one sees throttle bodies whose bores are larger than the port sizes. So the runners are tapered. I have assumed this was intended to increase velocity at the port. Guys with flow benches and lots of engine modification experience are always cautioning us not to make the ports too large.

You have read all this too, I am sure. Could you share your reasoning for using straight tubes (beyond the fact that I don't suppose one can purchase or easily fabricate tapered ones) and believing they will work well?

Walt

Walt,
I have already had a rethink on this based on other comments here and in this thread.
I am now going to fit the injectors immediately above the head flange. This has the added cost advantage of allowing me to use the standard 964 fuel rails and hoses and standard size filters. I will also be keeping the runners as short as possible as there isn't any overwhelming advantage to making them longer. In fact, as I read it, I will be better off keeping them short for driveability and response.

The TBs I am using don't easily lend themselves to being spaced wider (by 35mm). It introduces other complications with linkages and filters, so I am prepared to live with the trade-off of bent outer runners.

You are right, tapered pipe is a bit hard to come by! As it happens, the TB diameter is 44mm which happens to match readily available aluminium pipe with 50mm OD and 3mm wall. This size also allows me to use the standard 964 rubber manifold connector sleeves between the botom of the TBs and the runner.
The 964 inlet ports are 42mm, so I will be opening them out slightly to match the incoming 44mm.

All in all, I think I am getting close to my aim which is to setup a set of practical ITBs for less than 1/4 the price of off-the-shelf kits without a significant difference in potential performance. I have yet to tackle tuning and Megasquirt, but I suspect that will be a whole new story in a month or two.

[billjam]

Originally Posted by DW SD

Looks nice! Do you have that much clearance above? Will this go in a 911 engine bay?

Doug

Doug, I presume you missed the bit about "Just have to figure out how long to make the runners. They are way over-length in the pics below."
I have since decided to make them as short as possible.

[psalt]

Walt wrote,

On a related aspect: Usually one sees throttle bodies whose bores are larger than the port sizes. So the runners are tapered. I have assumed this was intended to increase velocity at the port. A quick review of Smith and Morrison's text did not uncover discussion of the relationship between TB bore and port size. Length of induction seems to get the most examination. There is a short mention of a Jaguar slide valve system, where the manifold tubing looks to be equal to TB bore, but is not related to port size.

Walt,

This is a complex subject, and a compromise between low speed drivability and high speed output. The taper is there to boost low rpm gas velocity. There is a compromise between boosting low speed velocity and lowering the mach index (choking point). This is explained thoroughly in Lumley's book "Engines", and stroke, piston speed, and cylinder displacement are also involved. If the taper is too great on a short manifold, the turbulence can effectively reduce the section of the pipe more than 25%. The port size is usually matched to the valve head size, the throttle plate to air flow needs. One rule of thumb for port size is 0.81-0.83 of valve head. On the N/A 911 with 49mm valves, port size ranges from 34-40mm or 0.69-0.82 (911SCRS 43mm-0.88), the 917 was 0.86. Weber recommends venturi size based on cylinder displacement and rpm, a 600 cc cylinder would need 40 mm @ 6000 rpm and 52mm @ 8000 rpm. Injector placement is another separate issue. One surprising reason carb engines can produce more power than injected engines is better atomization at WOT. Moving the injector away from the head gives more time for the fuel droplets to be atomized by the high speed air stream, and pointing the injectors against the air flow was also used for the same reason. CIS injectors have an ingenious rattle pin that shears the drops for better atomization

[DW SD]

Originally Posted by billjam

Doug, I presume you missed the bit about "Just have to figure out how long to make the runners. They are way over-length in the pics below."
I have since decided to make them as short as possible.

Yes, sir!! I did, blushing.... I was blinded by the interesting pictures. Apologies for overlooking.

Doug

[psalt]

The limit for intake runner port taper appears to be 1.7-2.5 percent decrease in intake runner area per inch of runner (a 1-1.5 degree taper). Too much may be worse than none at all.

[matty74]

Bill when you get it running you must post a video on youtube, I can't wait to see the outcome. I am doing an ITB project on my 3.8 build and your thread is inspiring me greatly

[billjam]

I can't believe two months have drifted by - I figured I'd better put in a bit of an update.
Actually, work, holidays and other commitments have seen this engine sit around with not a lot of progress, however, one major step forward is that I will soon have a car for this engine. It will be a G50 Carrera. Now I can move forward with a clear(er) goal.

Camshafts
John's DC21 grind cams are sitting on the shelf now.

Heads
New exhaust guides fitted and ports smoothed out and blended with inlet runners (from 42mm out to 44mm).



Coil Pack Ingition
I have sourced 12 Toyota coil packs but haven't done anything with them yet.

Oil Cooler
I now have a standard 911 cooler and thermostat from another Pelican, so I have been looking at how to modify the crankcase and shroud. Looks straight forward but it will involve making up a special air duct to modify the 964 shroud so that it more resembles the 911 shroud in the area between the fan and cooler.

ITBs and Inlet Manifold
The intake runners are fabricated now and are away for final welding of injector ports and fuel rail brackets.
I have received two oval K&N filters, now I need to fab the filter base and top. I'm going to try doing that in carbon fibre - should look OK.



Clutch and Flywheel
I will be using either the standard G50 clutch and flywheel or an uprated unit.
I have to look into this soon so I would be interested to hear recommendations.

Engine Management
Still planning to use Megasquirt but haven't progressed on this yet.

Not much will happen for next few months, but I'll update here as things develop. I am madly shopping for goodies for the "new" Carrera which I will collect in the US in April for a month's driving holiday. When it gets shipped back to Perth, I want to make sure that all the heavy, bulky stuff is in the container (= free shipping ).

[billjam]

And another month or so has drifted by!
I need to retire then I might get a bit more real work done.

Not much progress, but I do have the intake runners completed now.
All runners are matched and aligned with the bakelite spacers and head ports.
Brackets are welded on for standard 964 fuel rails.

Cost of parts for ITBs and intake runners:
- 2 sets of Triumph Daytona 44mm throttle bodies $220
- aluminum tube and plate $40
- tube bending $120
- bakelite for spacers $15
- welding $120
Total: $515

Obviously this doesn't include my time, but that's half the fun of it
I still have to make air filter bases and rain hats in carbon fibre (cost = my time plus about $80 in materials) and linkages/cables.

Nothing more will happen for at least the next two months because I will be touring around the US of A collecting cars and parts, generally being a tourist, and catching up with a number of Pelicans for a beer or two.

[shbop]

signing-up.

[mamut]

My thoughts, you should tie together the runners so you have a stronger foundation, also why you did not shorten more the runners?, good luck, cheers.

[billjam]

Originally Posted by mamut

My thoughts, you should tie together the runners so you have a stronger foundation, also why you did not shorten more the runners?, good luck, cheers.

When the runners are bolted down (3 bolts) they don't need extra support. They are also easier to fabricate as single units.
I have about 10mm extra height at the top which I plan to cut off. The height is mainly determined by the minimum radius of the bends.

Thanks for your interest.

[billjam]

Holidays and working away from home have really slowed progress but I am now starting to get a few things done with this engine project.
Carbon fibre air cleaner bases and tops for the ITBs are nearly complete. They just need a final clear coat to bring out that nice carbon fibre look.





Mounting the oil cooler to the 964 engine required a bit of thought. Searching forums didn’t come up with any real details of how to do it, only a few references indicating that it had been done before, so I will document the details of how I did it here in a separate thread. I am sure it will help others wanting to follow the same path.

[matty74]

Bill do you still have your manifold flanges and injector rails to fit the 964 manifold?

I am in need of a set.

Matt

[billjam]

Matt,
I am re-using the injector rails, but I do have some manifold flanges on the shelf.
I think some of the flanges might be cracked. Tonight, I'll check them out and email you some pics.

[al lkosmal]

Bill,
That is a beautiful job. Great attention to detail and some pro fab work.

Regards,
Al