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PostPosted: Tue Sep 25, 2007 10:10 am 
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Kind of branching things off from the bolt on EFI thread, since we had so much talk of a purpose-built manifold that isn't in production. If someone did design a purpose-built, top of the line slant six EFI intake that used a single throttle body and port injection, what features would it have? Here's my own thoughts on what it ought to have.

First, the market for this sort of thing can't be too huge, so it would probably have to be a sheet metal intake instead of a casting. Probably laser or plasma cut steel or aluminum if it's mass produced.

Second, it would probably use an off the shelf throttle body - 5.0 Mustang ones are pretty common, but there's a few other possibilities.

It ought to come with its own fuel rail and some brackets to fit Lokar linkages, as these seem to be the most common linkage for swap setups.

And it goes without saying that it'll need some development on a dyno to make sure everything works and it doesn't have air distribution issues or the like.

There's some other questions that I'm not as sure of. Would you want the throttle body pointing away from the engine block, or out over the valve cover to make turbo plumbing easier? Would the runners be long for low RPM torque, or short for high revving? How about provisions for air conditioning? Would it be worth the extra money if it could be CARB-approved with EGR fittings, or would you rather keep it as far away from the manifold as possible?

If something like this came out, would you consider buying one, and at what price?

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PostPosted: Tue Sep 25, 2007 10:38 am 
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Hi Matt,

I think that you are on the right track. The mustang TB's are dirt cheap, they will work with Megasquirt easily, and they have Idle Air Control built in. If someone wants to go big, there are all kinds of aftermarket large TB's available. All good things.

We would want a really good fuel rail and injector retention system as well. I don't want to mess with a gas fire. ( been there, lost the hair on my head when I was 17, working on a friend's Satellite.)

On to speculation: From the research I have done, we would want a plenum volume of around two liters. Individual runners of stock or longer length would be good, as they do help low end torque significantly. There might be some way of improving the mounting system, and keeping it dead flat against the head surface.

EGR-CARB approval--- I live in California, and I don't know how many newer slant cars are on the road, that would be subject to smog inspections. I suspect that most of the slanters here have old cars that would be exempt. However, I think putting in a few bungs would be useful, for running power brakes, vacuum signals, etc.

Air conditioning--- Similar problem. I don't know how many people here have cars with AC. There are some days when I would like it, but that is what my new-ish car is for.

Linkage: Sure, Lokar for those that have that need. However, I think that it would be pretty easy to make a throttle rod, early car work with a mustang TB. The kick down linkage for these cars should work as well. If the TB was to be moved off to the right or left, or up and down, there will be problems, and a cable throttle will be required.

Your last question: Yes, I would buy one. Cost:??? $250-$300, maybe more, maybe less, depends on what is offered.

EDITI am willing to spend more. I just don't know what something like this should cost. A small block chevy cheapo manifold is under $100.
I know this will cost more, but I am not sure what the level of engineering involved will work out to be.


Last edited by gmader on Tue Sep 25, 2007 10:48 am, edited 1 time in total.

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PostPosted: Tue Sep 25, 2007 10:39 am 
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What if that manifold was a Clifford with cast in bosses. (U-dril n tap)

What if the bolt in carb plate was replaced with a bolt in throttle body( TB and adapter)

Could this be done with a TB adapter( mebbe 5.0 to 4 barrel?)and a slant specific throttle cable adapter/kit? added to the Clifford manifold.

Can I buy the Clifford and adapters and fuel rail kit for less than $600?


I really like what you are doing . I am just really cheap.

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PostPosted: Tue Sep 25, 2007 10:43 am 
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CARB is only california stuff right? In california smog cutoff is at 1975, and I'm willing to bet a majority of our slant cars are older, so unless it will add next to nothing cost I don't think its worth it.

I would rather have the throttle body point towards the driver fender - no issue with hood clearance that way with cars - but may make it unusable in van applications?

The regulator will have to be decided on as well to figure out the mounting for that.

I paid 300 or so for the clifford manifold. With holdowns and rail and all? I would say ~400 would probably be fair.

May have to consider wether the throttle body has a ported vaccum port or not for the ones that don't want to do ECU controlled ignition as well.


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PostPosted: Tue Sep 25, 2007 10:44 am 
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Sandy, you are consistent:

http://www.slantsix.org/forum/viewtopic.php?t=13932&start=30

Quote:
Thrifty on paint....but not brakes.....and HEY!...it cost me $200 for the 5 speed.

I dont think of myself as thrifty....more like CHEAP.



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PostPosted: Tue Sep 25, 2007 10:49 am 
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throttle bodies could be mustang. think the sensors work for MS. the TB off of a jeep seems to be popular also, and the TB off of a 98-02 camaro is another option

don't worry about CARB or that crap, it will never be built if its designed for that. "offroad use only", especially with many of slants emissions exempt in much of the country(pre75)

for injectors, make it designed for the popular ones out right now like the ones in f-bodies, mustangs and the like. but have them included as an option, not standar because its so easy to find some used, and to match them to ur needs.

if its for turbo use, i would go mid length runners, get it away from the block, but don't worry about runner tuning.

i think the TB should be by the rad or towards the firewall, don't think it would work well for distribution being in the middle due to the length of a slant. look at the supra intake and basically create that for us. that might mean losing A/C tho cause the factory compressor is where the intake piping would be.

make it out of AL, would weight too much out of steel, and AL has better heat dissipation properties

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PostPosted: Tue Sep 25, 2007 11:14 am 
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Try to make runners equal length terminating in center plenum. Would be fine to "cross the runner over each other if you need to.

Do have some room to loop back if necessary, remember to have at least 2" straight at both ends to smooth out the air flow.

Otherwise, take a look at late 4.0L intake, it's a kinda log intake.

Cheers, Wizard


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PostPosted: Tue Sep 25, 2007 5:16 pm 
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I haven't done much work on estimating the cost of such a thing, just been thinking what it's likely to be comparable to.

Hmmm, there's three ways I could see doing this. My original idea was a fabricated sheet metal manifold. This wouldn't be as cheap as a casting if you were making a thousand of them, but it requires minimal tooling and I suspect it would be cheaper for a short run than castings. A good set of custom headers might be a good price comparison. I haven't priced one out yet, but I was expecting any result between $500 and $1,000. And I could be a bit off.

Then there's the possibility of a modified Clifford. I've seen the going rate for one-off machine work on Clifford intakes to be anywhere from $400 to $600, but it's likely to be cheaper if done in quantity. $500 might be a possible price on these, although it wouldn't take advantage of all the things one could do with an EFI design. Another note - these would be cheaper to build with a downdraft throttle body, but that might also make for the most hood clearance or intake restriction issues.

I'm not sure a short run casting could be done cheaply in a small run, although it does offer the most design freedom. Such a thing would be a great way to go in high volume, but I haven't priced out low volume castings. You could be looking at a price like this Greddy Supra manifold if somebody made such a thing.

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PostPosted: Tue Sep 25, 2007 5:51 pm 
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I've done quite a bit of thinking and calculation towards building an EFI intake manifold. My design would have tuned length tapered round tube runners that transition to the rectangular port shape at the head, two plenums and two throttle bodies.

The reason for two plenums is that two three cylinder intake manifolds will suffer much less vacuum and torque loss than a common plenum. The vacuum and torque loss of a common plenum comes from one cylinder having both valves open during overlap while another cylinder is on it's intake stroke. Valve overlap on one cylinder is a big vacuum leak to another cylinder. This issue is directly related to the overlap used. Divide the plenum and low end and mid range is improved. If the throttles flow enough then top end is not affected. My wife's 3.5 V6 Intrepid has an intake manifold built in just this manner and so does the Nissan VG30DE as used in Nissan Maximas and 300ZXs.

For a one-off or limited production manifold I'd use steel sheet and tube. It's not very heavy, easier to bend and weld and conducts less heat into the intake air than aluminum. A pair of throttle bodies from any 3.5L Chrysler LH car would work fine with a shortened connecting shaft. Here is an example of such a fabricated intake: http://www.sdsefi.com/techinta.htm

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PostPosted: Tue Sep 25, 2007 7:36 pm 
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Josh, I think you are right. I think something just like on the SDS site is the ticket. Simple shapes, and very easy to make. I have a good fabrication, weld guy here in Gaithersburg, and this would be just up his Alley. I think he would love to take on something like this. He does production hand work like this all the time. If someone were to supply a drawing, he would give us a quote on the price.

He has been making things like this for SBC's and BBC's for years. He is retired from the DAvid Taylor Naval Basin where he was the machinist/fabricator. He also has worked for years part time welding for the local Corvette shop. Does anyone want to venture enough to make up a drawing. It should be someone who will know how big each section of the devided plenum should be, and how big the runners should be. Tom will have some ideas on this too, so maybe basic dimensions, and a rough sketch are all we need to start with.

Sam

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PostPosted: Wed Sep 26, 2007 6:46 am 
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i, too, am considering building a custom intake for my slant when it comes time for injection. the dual plenum idea seems good, i'm just not sure about running two throttle bodies. not sure how to set that up. don't you need to balance/equalize the two plenums somehow?

BMW 6 cyl. intakes from the early to mid '80's are built similar to what you are talking about with the runners on top of one another. looks to have nearly equal runner length, too.

i had been considering moving the manifold up slightly to with access to the bolts, but it's all just thoughts and theory right now.

zedpapa

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PostPosted: Wed Sep 26, 2007 8:47 pm 
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If you put the TB pointing either to the side or front, you could raise the entire thing to allow easier access to the bolts. Are manifold flanges for the slant available from anyone, or would those have to be made? If so, then those could probably be either plasma cut, or cnc milled. Either way it would add to the cost if we had to make our own.

What would be the advantage of this design over the standard slant style manifold? Would it be RPM?, response?, balance? I am just wondering if the coolenss factor is the main draw here, or if there would be a performance benefit?

Sam

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PostPosted: Wed Sep 26, 2007 11:15 pm 
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Sam Powell wrote:

What would be the advantage of this design over the standard slant style manifold? Would it be RPM?, response?, balance? I am just wondering if the coolenss factor is the main draw here, or if there would be a performance benefit?

Sam


Reread my post. It's all about the torque.

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PostPosted: Thu Sep 27, 2007 4:55 am 
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I'm sorry Josh, I wasn't refering specifically to your design consideration. Did your answer seem a little harsh? It seemed to me like "Dumb dumb" was buried in that sentence,("re-read my post"). Translation:, "If you could read you woudn't be asking this question". When I did re-read it, the torque issue was mentioned, but it did not seem to me to be the big, overwhelming, over riding concern that your resonse indicated.

I just meant this entire concept of custom designing a new and perfected intake manifold is of interest, but needs to be explored on a benefits/cost basis. I was wondering if the manifold we have, and have had for 45 years is that bad. This is a question that is really worth exploring. Everyone knows that with a carb there are serious distribution issues with the slant manifold. And we know that there are warm up issues with the standard manifold, and a carb.

But with MP EFI what are the serious shrotcomings of what we have. Discussing this question will lead us towards design parameters if we are really serious about it.

I am also turned on by coolness stuff as well, so even if the answer was not conducive to persuing the project on a performance basis, I might still think it was worth while for other reasons. There might be other good reasons for doing this as well. It might be cheaper in the long run than buying premium priced, out of production cast units. It might, in the long run fit under the hood better than what we have.

The purpose of my questions is to clarify in our minds what kind of design issues to discuss with my local fabrication guy here. I still think I might go to him after I have a good idea what we want to do, but I can't just walk in and say "make me a manifold". So please don;t give responses that shut down questions. If there is no interest in further examination of this, I will just drop it. I have a manifold already that works.

Not knowing is the first step towards wisdom.

Sam

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PostPosted: Thu Sep 27, 2007 8:42 am 
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Im with you Sam.

If this is a discussion about custom fabbed one-off designs I will look and post elsewhere.

If this is about a universal EFI intake.....affordable and tuneable then Im in.

I have made aluminum tube intakes....costly and a crapshoot.

Pierres Clifford intake is a model for " available and affordable"

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