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914World.com _ 914World Garage _ Type IV plenum intake manifold questions...
Posted by: Mueller Mar 14 2015, 10:28 AM
Has anyone made a dual plenum like used on the 911 engines for a Type IV?
Posted by: Bob L. Mar 14 2015, 10:44 AM
Someone here has played around with it. I forget who. IIRC they got a few extra HP but didn't think it was worth pursuing.
Posted by: Mike Bellis Mar 14 2015, 11:03 AM
Maybe it's because the 911 unit is engineered for flow, reverb, resonant frequency, power and emissions.
When the 914 was built the technology was limited. To build one without the R&D mentioned above could be a waste of time and loss of power.
Posted by: Mark Henry Mar 14 2015, 05:01 PM
I played with the design, it would work but only at higher power levels.
But then at higher power levels it would be a down grade from ITB's, but it may have better tunability.
Of course we are also talking aftermarket FI.
Posted by: r_towle Mar 14 2015, 05:04 PM
I recall seeing a race car running two full Djet setups with two plenum a and two throttle bodies etc, the plenums are welded together
Posted by: Mark Henry Mar 14 2015, 05:11 PM
I recall seeing a race car running two full Djet setups with two plenum a and two throttle bodies etc, the plenums are welded together
Maybe oldschool with D-jets, but why would you do this with modern programmable FI?
The only reason to do this over ITB's is for a more stable MAP sensor signal with the single TB intake.
It's why Porsche did it.
Posted by: Mark Henry Mar 14 2015, 05:22 PM
Here.... I'll save you a shitload of research 
http://shoptalkforums.com/viewtopic.php?f=23&t=126654
Posted by: type47 Mar 14 2015, 09:20 PM
Tangerine Racing system as seen at Hershey
Posted by: Jake Raby Mar 14 2015, 10:28 PM
When I've gone this way the result was an even more difficult to tune engine that was much more picky about cam specs than any other way. I've always had better luck with twin ITBs over a central plenum or a pair of localized plenums.
Only once has this made more power here and that was a 2.6L engine for a square back where I was able to get 80% of the engine's displacement into a pair of plenums. It wasn't worth the 6Hp that it made.
Posted by: toon1 Mar 14 2015, 10:28 PM
Mike, look up Hemholtz resinator and supercar intakes.
It's easily do able....I plan on doing one. My plan is to do dual TB,s. If I don't do 2 I still think you can make a better system for 1 TB.
Posted by: Mark Henry Mar 15 2015, 07:05 AM
When I've gone this way the result was an even more difficult to tune engine that was much more picky about cam specs than any other way. I've always had better luck with twin ITBs over a central plenum or a pair of localized plenums.
Only once has this made more power here and that was a 2.6L engine for a square back where I was able to get 80% of the engine's displacement into a pair of plenums. It wasn't worth the 6Hp that it made.
Your statement doesn't explain much....
As far as the plenums being 80% that would be about the size of a connecting tube and two 1-quart (1 litre) oil bottles (or for a single plenum one 2-litre bottle).
Here's what it takes to fab a single plenum intake
http://www.sdsefi.com/air12.html
Simple search may give you some ideas
https://www.google.ca/search?q=EG33+intake+manifold+project&es_sm=93&tbm=isch&tbo=u&source=univ&sa=X&ei=ZnwFVeW7Cqq_sQScqoGYAg&ved=0CD0QsAQ&biw=1745&bih=926#tbm=isch&q=VW+type+4+intake+manifold+project
Posted by: toon1 Mar 15 2015, 09:24 AM
When I've gone this way the result was an even more difficult to tune engine that was much more picky about cam specs than any other way. I've always had better luck with twin ITBs over a central plenum or a pair of localized plenums.
Only once has this made more power here and that was a 2.6L engine for a square back where I was able to get 80% of the engine's displacement into a pair of plenums. It wasn't worth the 6Hp that it made.
My plan was to do ITB's with two plenums and longer runners for better low end performance. The trick would be to get the optimum runner length. That would be a lot of dyno time. I would suspect that the engineers designed the length of the stock runners close to optimal for a daily driver.
I don't see much benefit to dual TB,s on a single plenum (for a daily driver). Tip in tuning would be hard to get correct. Progressive, dual TB,s would be kinda neat to try. Have the second TB start opening at say 3K rpm.
Even if you were to stay with a single TB and single plenum. I think there is a lot of room for improvement on the stock system.
Posted by: Mueller Mar 15 2015, 09:41 AM
If you notice on the 911 engine, they are using individual throttle plates for each cylinder, that is from a Singer 911, and I'm guessing not a stock or factory setup.(?)
Looking at the Subaru stuff, I found some interesting things:
Posted by: toon1 Mar 15 2015, 09:45 AM
There is some cool stuff out there. I just seen a single plenum , short runner LS intake that had a angles TB so the air flow doesn't favor the front cylinders. Thought that was interesting
Posted by: Mueller Mar 15 2015, 11:33 AM
There is some cool stuff out there. I just seen a single plenum , short runner LS intake that had a angles TB so the air flow doesn't favor the front cylinders. Thought that was interesting
I've seen one company selling parts for the newer watercooled Porsches that have dimples cast into the plenum center section, will have to try and find a picture.
Posted by: r_towle Mar 15 2015, 12:57 PM
I recall seeing a race car running two full Djet setups with two plenum a and two throttle bodies etc, the plenums are welded together
Maybe oldschool with D-jets, but why would you do this with modern programmable FI?
The only reason to do this over ITB's is for a more stable MAP sensor signal with the single TB intake.
It's why Porsche did it.
The one I saw, I think DD know about it, but it was a long time ago, and posted here, was two full DJet setups to make a larger motor work.
Personally I think it was a cool thing to try, but doing it today I would just go with a single larger throttle body, and modern EFI
Posted by: r_towle Mar 15 2015, 01:04 PM
A bit confused on the pictures Mike.
My 911 (3.2 stock) uses one large throttle plate with the dual plenum shape, but it does not use individual throttle plates for each cylinder, and not sure what that might buy you honestly.
In my opinion, there are enough other parameters to deal with that adding in individual cylinder tuning just makes it harder....
I think there is a better way to make the motor deliver everything it can, and that would be good head design, proper valve train setup and lots of testing to make sure all cylinders are performing at the same level.
Tuning to match might creat some bad stress on the crank and make the motor run poorly due to mis matched power from each cylinder. I would rather sacrifice some power and tune down to the weakest cylinder instead of maxing out each cylinder, just seems like a bad recipe for longevity.
Rich
Posted by: toon1 Mar 15 2015, 02:43 PM
A bit confused on the pictures Mike.
My 911 (3.2 stock) uses one large throttle plate with the dual plenum shape, but it does not use individual throttle plates for each cylinder, and not sure what that might buy you honestly.
In my opinion, there are enough other parameters to deal with that adding in individual cylinder tuning just makes it harder....
I think there is a better way to make the motor deliver everything it can, and that would be good head design, proper valve train setup and lots of testing to make sure all cylinders are performing at the same level.
Tuning to match might creat some bad stress on the crank and make the motor run poorly due to mis matched power from each cylinder. I would rather sacrifice some power and tune down to the weakest cylinder instead of maxing out each cylinder, just seems like a bad recipe for longevity.
Rich
The last part of your statement is confusing.
What your describing(the way I'm understanding it) is blue printing, which is a good .
How would improving intake air flow un balance the cylinders and be hard on the crank?
Posted by: McMark Mar 15 2015, 05:26 PM
I suspect the 911 intake developed two 'plenums' mostly due to space constraints. I seriously doubt there is a payoff to the development for a dual plenum for the T4.
Also, IMHO, if you're going to modern fuel injection in a street car, one of the huge benefits is being able to use a single throttle body. Remember that any number of throttle bodies (more than 1) must still be accessible and adjustable for syncing, just like carbs. PITA.
Aside from variable intake length (VarioRam) and variable valve timing (VarioCam) most engine engineering developments are going to be of more benefit in the fuel economy and emissions department. If you're looking to increase engine output, as in horsepower or torque, stick to the basics. Displacement and forced induction. There isn't a fancy 2.0 that will compete with a 2270.
Posted by: toon1 Mar 15 2015, 05:55 PM
I suspect the 911 intake developed two 'plenums' mostly due to space constraints. I seriously doubt there is a payoff to the development for a dual plenum for the T4.
Also, IMHO, if you're going to modern fuel injection in a street car, one of the huge benefits is being able to use a single throttle body. Remember that any number of throttle bodies (more than 1) must still be accessible and adjustable for syncing, just like carbs. PITA.
Aside from variable intake length (VarioRam) and variable valve timing (VarioCam) most engine engineering developments are going to be of more benefit in the fuel economy and emissions department. If you're looking to increase engine output, as in horsepower or torque, stick to the basics. Displacement and forced induction. There isn't a fancy 2.0 that will compete with a 2270.
My Idea is more for efficiency, not to increase HP. I just want the motor to breathe easier.
The 1.7 is severely under aspirated.....IMHO. All the corners it turns to get into the plenum and transitions into the runners can be easily improved on.
Posted by: McMark Mar 15 2015, 06:39 PM
To what end? Why spend the time engineering? And how will you know if you actually made an improvement?
Posted by: r_towle Mar 15 2015, 08:35 PM
I suspect the 911 intake developed two 'plenums' mostly due to space constraints. I seriously doubt there is a payoff to the development for a dual plenum for the T4.
Also, IMHO, if you're going to modern fuel injection in a street car, one of the huge benefits is being able to use a single throttle body. Remember that any number of throttle bodies (more than 1) must still be accessible and adjustable for syncing, just like carbs. PITA.
Aside from variable intake length (VarioRam) and variable valve timing (VarioCam) most engine engineering developments are going to be of more benefit in the fuel economy and emissions department. If you're looking to increase engine output, as in horsepower or torque, stick to the basics. Displacement and forced induction. There isn't a fancy 2.0 that will compete with a 2270.
My Idea is more for efficiency, not to increase HP. I just want the motor to breathe easier.
The 1.7 is severely under aspirated.....IMHO. All the corners it turns to get into the plenum and transitions into the runners can be easily improved on.
Spend your money on new 1.8 liter AMC heads.
It won't breath any better until you fix the heads.
1.7 heads have way to much restriction to bother doing any supposed improvement on the intake.....
The exhaust port is the issue.
Posted by: larss Mar 16 2015, 02:18 AM
Not that it adds wery much but this is my expetiment:
http://www.914world.com/bbs2/index.php?act=ST&f=2&t=228412
Lars S
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