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Intake Modification Concept for Ideola's Ultra Wide Body 931
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ideola  



Joined: 01 Oct 2004
Posts: 15451
Location: Woodstock IL

PostPosted: Tue Aug 28, 2007 6:41 am    Post subject: Intake Modification Concept for Ideola's Ultra Wide Body 931 Reply with quote

Here is my concept for a modified intake manifold, as discussed in Ideola's Ultra Wide Body 931 Build. Here is a textual repeat of the concept from that thread:

Quote:
First, I am going to modify a stock series I intake manifold. I am going to cut a hole directly opposite the current TB location. At this new opening, I am going to weld a short runner at about a 35 to 45 degree angle to the plenum; at the end of this runner I will attach a square plate to which the throttle body will be mounted, resulting in it being oriented 90 degrees from the direction it currently faces, toward the front of the car, and more importantly, in precisely the correct location to receive the output from the FMIC. The TB mounting plate will be square, and will be designed with a bolt pattern to accomodate a series II TB, and will later be able to receive an adpater in order to accept an EFI-capable TB, possibly a 65mm Ford 5.0 TB like the one that Nick is using.

Measurements will need to be precise, and the brake master will need to be rid of its sensors, but there is just enough physical space for this approach to work, and the brake sensors can be relocated (see Nick's thread on EFI). Furthermore, from what I understand, the TB location and position relative to the intake runners is not terribly critical, especially in a high-boost, high-flow situation. If anything, from what I've gleaned on intake designs, I believe the additional plenum volume that this runner will add to the intake could be beneficial for my high boost plans.

The original, rectangular TB opening will be blocked off with an aluminum plate [and will possibly be used as a mounting point for additional injectors for fuel enrichment]. The principle reason I came up with this design is to accommodate a FMIC setup without having to come up with a completely custom intake manifold [in order to avoid sharp bends in the IC-to-TB plumbing]. I wanted to avoid having to reinvent the plenum chamber, since as Nick notes in his design, it might have benefited from venturis or other engineering measures that I frankly am not confident I would ever master. Retaining the stock plenum design with an additional short runner seemed the lesser of evils to me. The resulting location of the front-facing TB will allow for short easy charge tube runs, as direct as possible without radically changing the turbo location. Also, my modified intake approach will "future-proof" the overall design so that I can add EFI later.


Here are photos of a five minute mock-up using an improvised 3" cardboard tube, a piece of packing foam, and some scotch tape:






Looking at the mock up, the immediate concern I have is that the size of the runner seems to add a lot more volume to the plenum than I was originally envisioning. Of course, it could be shortened, the angle tweaked, and a smaller diameter tube could be used. This is based on 3" pipe; it could be as small as ~2.5" and still not restrict flow coming from the TB bore.

Note that the new TB flange ends up in precisely the right location for not only the FMIC outlet, but also to take advantage of the forward-most mounting point on the bottom of the stock intake, so that the flange and TB can be supported by an add'l bracket if necessary. If I go this route, the plan will be to send the intake-head-exhaust and possibly the turbo housings to be extrude honed.

Even though I'm planning to relocate the coolant reservoir to the battery tray (for other reasons), it is not required. There is enough room for everything to fit as mocked up without requiring any other changes, other than removing the one sensor on the back of the brake booster. Everything else can stay stock. Which has me thinking, if this works for the race car, I might use the concept on the 941 as well when it's time to add an intercooler to it. The location of the TB ends up almost exactly in the perfect location to accommodate the outlet from a 944 style IC (I have one that I used to help verify the mock up location). I may end up going with a completely custom IC and saving the 944 IC for the 941, but the TB location ends up being just about perfect for any FMIC.

This mod is motivated almost solely by a desire to install a FMIC. In the case of the wide body project, I have a variety of options available to me in terms of IC placement (top mount, side mount [holbert style], liquid-to-air in the batter tray, etc.). But based on my research re: IC design and efficiency, I believe a front mount air-to-air intercooler is the best possible alternative for my particular goals; therefore this intake mod presents the best location of the TB to minimize angles and charge tube length.

OK people, have at it
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88 924S SE | 82 931 Holbert | 81 Euro 931 | 81 Weissach | 80 US 928 | 80 US 931 '941' | 78 D-Prod Replica | 78 w/D-Prod kit | 78 Poli-Form | 78 Limited Edition


Last edited by ideola on Sat Jul 18, 2009 12:22 am; edited 5 times in total
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bass gt  



Joined: 02 Dec 2004
Posts: 971
Location: Johannesburg for now!!

PostPosted: Tue Aug 28, 2007 7:15 am    Post subject: Reply with quote

Dan,

Good line of thinking, but i have a point. The flow with the pipe work seems to concentrate the air flow to the rear most runners. The runner for cylinders 1 and 2 will reqire the air to reverse direction, which i don't think will be too good. Why not look at cutting open the plenum at the most forward end, and welding the TB mount there. Firstly, it will give an equal flow across all the runners, and secondly, it will reduce the plenum volume. As you are using a single TB, i don't think the flow charachteristics will be too good with the angled pipe. Or alternatively, why not put a mandrel bend 90 degree elbow into the plenum, opposite from the stock TB location. This will again equalise the flow across the 4 runners and link up to the FMIC you are planning.

regards,

Steve
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ideola  



Joined: 01 Oct 2004
Posts: 15451
Location: Woodstock IL

PostPosted: Tue Aug 28, 2007 7:32 am    Post subject: Reply with quote

bass gt wrote:
why not put a mandrel bend 90 degree elbow into the plenum, opposite from the stock TB location
Because there's not enough room to do it with the brake booster and master cylinder. That was actually my first thought, but I just don't see a way of doing that without moving the booster, something I am really loathe to do.

Quote:
Why not look at cutting open the plenum at the most forward end, and welding the TB mount there
Because it would interfere with the stock alternator location, again, something I'm hoping to avoid having to re-engineer. HOWEVER...slight variation on that theme...if I cut off the end and put a real short runner, say 2-3 inches at most, the TB could mount there, it would be at a ~45 degree angle, and a very modest bend coming from the IC would still work. This arrangement would definitely require moving the stock coolant reservoir, but that's no problem because I'm planning to do it anyway.

In terms of the original design, it was a bit tough to mock up in 5 minutes with cardboard and scotch tape, but my thought was to have the actual opening pretty much directly across from the original TB location, and just about the same size (not as large as it appears in the mockup). I take your point about the air flow direction, but do you think that's something that could be corrected with a strategically placed baffle or two? Also, if we did something on the end of the manifold at about a 45 degree angle, would we have the same problem with the first runner, and would baffling help there?
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88 924S SE | 82 931 Holbert | 81 Euro 931 | 81 Weissach | 80 US 928 | 80 US 931 '941' | 78 D-Prod Replica | 78 w/D-Prod kit | 78 Poli-Form | 78 Limited Edition
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-nick  



Joined: 16 Nov 2002
Posts: 2699
Location: Cambridge, MA

PostPosted: Tue Aug 28, 2007 7:40 am    Post subject: Reply with quote

If I had to do mine over again, I would just copy Steve's individual throttle body setup. It takes up less room and gives you the advantage of a venturi intake. Plus you get the HP benefit. The only welding involved will be making up a "plenum" that feeds the ITB's.
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1980 931S
15psi boost, MS-II, EDIS, 951 IC, custom intake, Ford 5.0L throttle body, Forge BOV, WB o2, G31 w/LSD, 964 wheels, 968 rear sway, Bilsteins, 200# Welt. springs. A laptop, and a partridge in a pear tree.
1991 964 C4 Cabriolet
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Lizard  



Joined: 03 Nov 2002
Posts: 9364
Location: Abbotsford BC. Canada

PostPosted: Tue Aug 28, 2007 8:08 am    Post subject: Reply with quote

nick agreed on the ITBs however they are pricey buggers, Dan would be looking at around $1200-$1500 to get what he needed.
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ideola  



Joined: 01 Oct 2004
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Location: Woodstock IL

PostPosted: Tue Aug 28, 2007 8:12 am    Post subject: Reply with quote

Lizard, you read my mind! I'd love to do ITB's but man, I'm not sure I can tackle that right now, both in terms of $$$ and brain power to figure it out

Taking yet another look, I might just be able to do the 90 degree mandrell bend...but it will have to be an awfully tight bend to fit. There's no more than 3.5" of clearance, allowing about .5" of room to allow for some vibration and flex. There is also a brake line that is inconveniently located...not sure if it could be moved to the lower port, or if it could be bent in such a way as to clear the 90 degree elbow.

Another advantage of having the original TB opening with a removable plate is that you could play around with different baffling setups...I'm just wondering if a version of my original design with a strategically placed baffle or two might still be the best route...
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88 924S SE | 82 931 Holbert | 81 Euro 931 | 81 Weissach | 80 US 928 | 80 US 931 '941' | 78 D-Prod Replica | 78 w/D-Prod kit | 78 Poli-Form | 78 Limited Edition
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-nick  



Joined: 16 Nov 2002
Posts: 2699
Location: Cambridge, MA

PostPosted: Tue Aug 28, 2007 8:29 am    Post subject: Reply with quote

Wow, that much? I'll admit that I haven't looked into it too much but I figured bike throttle bodies couldn't be that expensive? It's really just a tube and valve. Not much brain power required to set them. A carb sync / vacuum gauge would work just fine to adjust the butterflies right?
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1980 931S
15psi boost, MS-II, EDIS, 951 IC, custom intake, Ford 5.0L throttle body, Forge BOV, WB o2, G31 w/LSD, 964 wheels, 968 rear sway, Bilsteins, 200# Welt. springs. A laptop, and a partridge in a pear tree.
1991 964 C4 Cabriolet
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ideola  



Joined: 01 Oct 2004
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Location: Woodstock IL

PostPosted: Tue Aug 28, 2007 8:34 am    Post subject: Reply with quote

Hmmm...could they be mounted to a weber carb manifold??? I have two of those sitting around...
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88 924S SE | 82 931 Holbert | 81 Euro 931 | 81 Weissach | 80 US 928 | 80 US 931 '941' | 78 D-Prod Replica | 78 w/D-Prod kit | 78 Poli-Form | 78 Limited Edition
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bass gt  



Joined: 02 Dec 2004
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Location: Johannesburg for now!!

PostPosted: Tue Aug 28, 2007 8:39 am    Post subject: Reply with quote

Guy's,

Not wanting to hijack this thread, but i have a revised ITB arrangement in the pipeline
This will be an 8 injector set up, with the 4 upstream injectors being beyond the throttle butterflies, facing backwards into the air flow. These will be switched into play once the airflow reaches a set level.
But the most interesting thing is that if it all works out, it will allow the inclusion of ITB's, whilst retaining the stock brake booster and alternator locations. Something that may be of interest to you. I am also lowering the runner diameters from 45mm to 37mm at the head to 45mm at the plenum, giving a better airflow acceleration. Watch this space.
Dan, on my latest plenum, i have the air feeding in too close to runners 2 & 3 and have found that it is adversly affecting the airflow to cylinders 1&4.
My advice would be to either enter the air at 90degrees to the runners, such as the stock intake, or at one end, allowing the air to flow across all 4 cylinders.
Or what about using the stock TB, and direct the pipe work around the alternator to reach the IC?
All food for thought i guess

Keep up the good work,

Steve
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PwrGTOGuy  



Joined: 23 Jun 2007
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PostPosted: Tue Aug 28, 2007 9:10 am    Post subject: Reply with quote

bass gt wrote:
Guy's,

Not wanting to hijack this thread, but i have a revised ITB arrangement in the pipeline


You and me both
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RC  



Joined: 25 Mar 2007
Posts: 2634
Location: Australia

PostPosted: Tue Aug 28, 2007 9:26 am    Post subject: Reply with quote

A quick visit downstairs to the garage with a measuring tape confirms that there is 5 3/8" between the edge of the manifold and the master cylinder reservoir, sufficient room IMO for a 3" mandrel bend. Must agree with Bass gt`s comment regarding placement for equal flow to all runners.

Using a minimum radius bend, slightly compressed at the manifold end, say 2 1/2 hi X 3 3/8 wide (or whatever), and also scalloped to fit the manifold shape, it should only be necessary to relocate the front brake line to the bottom master cylinder hole. Looks like sufficient length in this line for a simple hand twist. Allowing the 3/8" of clearance to the fluid tank should be fine as the engine mounts don`t allow for much sideways movement and the aluminium bend, HOPEFULLY wont get anywhere near hot enough to deform the plastic or boil your fluid.

I am interested in reading any references you previously mentioned, or anyone else has, concerning the non-critical placement of the TB in relation to the symmetry and even flow through the runners especially in boosted applications. Personally, I think that equal flow is a primary design objective, but am open to documented research stating otherwise.

Roger
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macBdog  



Joined: 16 Aug 2004
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Location: Brisbane, Australia

PostPosted: Tue Aug 28, 2007 10:23 am    Post subject: Reply with quote

That looks really good but wont the foam and sticky tape arrangement leak under boost?
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ideola  



Joined: 01 Oct 2004
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Location: Woodstock IL

PostPosted: Tue Aug 28, 2007 10:25 am    Post subject: Reply with quote

Roger, I think you are right...it's tight, but I think it can be done with a 90 degree bend without causing too much difficulty with the brake booster/cylinder. The key issue is what radius is required on the bend...

What about this...(variation on a theme)...what about welding a 1/2"-3/4" circular flange (2.5" OD) onto the intake, and then using a silicone elbow to make the turn? Then make up another flange that the TB could mount to, which would be attached to the intake / engine via the aforementioned bracket? Would a silicone elbow be acceptable? I know hard pipes are preferred where possible, but maybe this is a situation where a silicone elbow would be just right for the job. The silicone elbows I've seen have much smaller radii than mandrel bent aluminum, at least the ones I've seen available online. I'm wondering how tight the radius would need to be...not exactly sure how to go about measuring for that...

Regarding the placement of the TB, I'll see if I can dig up the source I was reading...not sure if I bookmarked it or not...but from what I recall, the concept was that it didn't matter so much how far the TB was from the plenum, but I'm sure that the placement relative to the runners is critical. In other words, if I retained the stock intake, the TB could be moved forward or backward in its current orientation, provided that the plenum volume remained correct for the amount of airflow required. But I'm probably munging it all up...better for me to see if I can go find the source...

Steve, et al,
While I would love ITB's, sadly I'm afraid that approach is beyond my means right now. I could do it if I were willing to delay the project another 6 months, but at some point, I want to drive this beast, not just wrench on it and write about it

In any event, if this intake mod turns out to be a bust, regarding your post about retaining the stock TB location and adjusting the plumbing: my fall back position is to replace the Series I intake & TB with the Series II setup I have, and then just revert back to the Holbert IC that came with the car. If I can't get a FMIC with direct runs, that is the next best alternative. I'd rather do that than have crazy bends to get into the stock TB location.

In fact, the Holbert location ends up using shorter runs...the only thing shorter would be the GT style top mount, but I ruled that out long ago due to heat sink concerns by having it sit in the engine bay, and worse, right over the exhaust manifold. The Holbert IC core is HUGE, but would have to be reworked wrt its end tanks and bracketry. It's also HEAVY, and I think the side mount location is less than optimal in terms of airflow and weight distribution. Besides, if I go with it, I won't have a good reason to implement the "Bass GT Hood Duct" (I suppose it could always help airflow thru my radiator...).

I either have to spend money on the intake or I have to spend money on the Holbert IC. We'll see.
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88 924S SE | 82 931 Holbert | 81 Euro 931 | 81 Weissach | 80 US 928 | 80 US 931 '941' | 78 D-Prod Replica | 78 w/D-Prod kit | 78 Poli-Form | 78 Limited Edition
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RC  



Joined: 25 Mar 2007
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Location: Australia

PostPosted: Tue Aug 28, 2007 11:11 am    Post subject: Reply with quote

Dan, now that i`ve got a few more coffee beans in my gut and some caffeine in my brain I realize that your 931 manifold is probably wider than the NA one I measured. I see you measured 3 1/2'', DOH! That is tighter. Think most mandrel bends are 5'' radius on the centreline. You possibly can get tighter elbows (I think schedule 6 for steel) through a boilermakers supply agent. Another google search there.

Silicone bends have pretty well no (well maybe 1/2") radius. I have a 2 1/2" - 3" reducing one here that is very tight. Was looking at using it on the other side at the TB in the stock location on my setup. I actually want to feed from the SC on the intake side, through a FMIC, and out on the exhaust side into my TB, more or less in modified stock position or at 90 deg. Either way, to fit a 62mm TB (GM with IACV) it involves cutting and welding the manifold, so am interested in your setup, only probably reversed. A silicone bend to a plate welded at 90 deg out from the manifold with the TB hole in it and a spigot. Would look stupid but should work.

Now these beans are coming on! Have you considered a NA manifold that does give 5" clearance, and more symmetrical runners. I understand the ports are a match only some stud holes are 5mm off and have to be drilled or slotted. I looked into this as I originally wanted to use a 931 S2 intake before Nemesis ripped me off. That would have given more clearance on the TB side. For your purpose a NA will give you more on the brake cylinder side. More to think about maybe.

Roger
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ideola  



Joined: 01 Oct 2004
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Location: Woodstock IL

PostPosted: Tue Aug 28, 2007 11:58 am    Post subject: Reply with quote

RC, Wow! You are right, the NA intake provides quite a bit more room...now that is definitely worth looking into! Gotta see if I can pick one up somewhere for next to nothing. I'm just wondering if the differences in the runner lengths would matter...tomorrow I'm going to have a really close look at the Series I and the NA manifolds...just make sure there's no other real glaring problems. Slotting a few stud holds shouldn't be a big deal...
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88 924S SE | 82 931 Holbert | 81 Euro 931 | 81 Weissach | 80 US 928 | 80 US 931 '941' | 78 D-Prod Replica | 78 w/D-Prod kit | 78 Poli-Form | 78 Limited Edition
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