Staring down the EFI rabbit hole again, /6 intake design, Which way around for the 964 plenums in a 914? Options

[ClayPerrine]

Probably don't have to tell an experienced engine guy like you about this but for others that may not be aware, cam shaft lift and duration are key with EFI. At least with CIS as too much pulse in the intake makes for wacky reactions to drivability. Maybe you can expand on how it effects more modern EFI stuff.

There are 3 types of fuel injection.

1. Mass Airflow. This is CIS, L-Jet and it's descendant, DME. It uses an air flow meter or mass air meter to measure the incoming air volume and meter fuel to match. The Vane air meter on L-Jet and CIS is terrible for high performance camshafts. The reversion of the cam overlap makes the air meter flap oscillate back and forth, affecting mixture and eventually breaking the vane air meter. Also, vane air meters are a restriction in the intake tract that reduces horsepower. A Mass airflow meter is better because it doesn't have a flap, but it still is affected by reversion. But careful software programming can tune out the effects of reversion.

2. Speed Density. This is D-Jet and a lot of modern injection systems like GM fuel systems. It measures manifold vacuum to determine the air flow requirements of the engine. It is also affected by reversion, as the cam overlap lowers available manifold vacuum at idle to the point where the ECU is unable to control the mixture effectively.

3. Alpha-N. This is the Bosch MFI system used on early 70s 911s and cars like the BMW 2002Tii and the Porsche 917 that ran at LeMans. It doesn't measure airflow at all, so reversion cannot affect it. It just looks at the position of the throttle and the RPM and uses that to determine the required fuel amount to inject. It will work with any camshaft. But it is horribly inefficient, and it gets lousy fuel mileage. But it has extremely good throttle response and performance. And it has that incredible scream when it is up on the cams and producing horsepower. :shiver:

Modern aftermarket EFI setups like Megasquirt and it's derivatives, can be setup in a hybrid mode, where it will use Alpha-N at low speeds due to reversion, and at higher speeds it will switch to Speed Density or Mass airflow. This allows the engine builder to us radical cams, and still get much better fuel efficiency and performance. The modern EFI can also make a radically cammed engine Idle like a mildly cammed one.

Frankly, the computer chip was the best thing to ever happen to gasoline engines. You can get more HP out of a 2.0L engine that was ever thought possible in the 1960s from a 7.0L monster Chrysler Hemi Elephant motor. As I see it, learning and using modern EFI is the only way to go for performance, drivability and reliability.

My future plans are to megasquirt the 4.0 motor, using the current harness and parts. I will change out the throttle body for a larger one, and to support an integrated idle air motor and throttle position sensor. I will also add wheel speed sensors to the rear wheels so I can use the traction control module. I have considered the idea of ITBs, but I think just a bigger throttle body will be better for street use.

Clay

Clay

[Mark Henry]

Probably don't have to tell an experienced engine guy like you about this but for others that may not be aware, cam shaft lift and duration are key with EFI. At least with CIS as too much pulse in the intake makes for wacky reactions to drivability. Maybe you can expand on how it effects more modern EFI stuff.

Yes Big cams with big duration equals a poor vacuum signal for the MPS (Manifold Pressure Sensor) adding ITB's (individual throttle bodies) makes the situation even worse. Aftermarket EFI can cope better with this poor vacuum signal but you can push things too far.
My hope is the plenum with a single TB and a vacuum can will give me a more usable signal for the MAP. I also won't have to worry about sync issues with the single TB.

You can get around this by running TPS only, also known as AlphaN, to bypass the MAP but you lose things like altitude correction and the system is more sensitive to pedal inputs, which can be a pain on long trips. But EFI of course wins on fuel mileage. Between having to run in AlphaN or carbs, I think carbs wins on drivability as they're not as touchy to pedal inputs as the EFI in AlphaN.

[Mark Henry]

Well it looks like Clay can't find his old intake, so I'm on the hunt for a 964 intake. (IMG:style_emoticons/default/sad.gif)

Thank you for trying to find the intake Clay, especially with the sheet show you guys have been having with the weather.

I sent out the ECU to SDS for the data logging daughter board install, drill case for connector and the adapter cable all for $125.
More importantly than this will allow me to download the current software, before I would have to chip the board to do an upgrade. Basically this turns my used 2012 system into a 2021 ECU.

[Chris914n6]

There is a bunch of math involved in a good intake, like the chamber should be the same displacement as the cylinders it feeds. Short runners are good for low and high RPM but long runners do better midrange, thus the split chamber/flap design on most modern cars.

That fab'd one in the pics is horrible.

Making a factory intake fit makes a ton of sense.

[Mark Henry]

There is a bunch of math involved in a good intake, like the chamber should be the same displacement as the cylinders it feeds. Short runners are good for low and high RPM but long runners do better midrange, thus the split chamber/flap design on most modern cars.

That fab'd one in the pics is horrible.

Making a factory intake fit makes a ton of sense.

The one in pic's are from an aircraft, I doubt it ever sees over 5krpm even with a reduction drive. The flapper on 911 comes into play at about 5500rpm. I know the math somewhat, I researched this 10 years ago with my big T4 build, but I ended up putting that engine in my VW bug and had to use ITB's.

But the factory intake would save me a ton of work.

[JamesM]

You can get around this by running TPS only, also known as AlphaN, to bypass the MAP but you lose things like altitude correction and the system is more sensitive to pedal inputs, which can be a pain on long trips. But EFI of course wins on fuel mileage. Between having to run in AlphaN or carbs, I think carbs wins on drivability as they're not as touchy to pedal inputs as the EFI in AlphaN.

Look into the feature set of Megasquirts hybrid alpha-N mode, should take care of most if not all of these issues depending on the motor.

Ive run it on an ITBd 2270 and while it is a good deal more complex to initially tune the results are pretty amazing.

[Carbon-14]

https://www.youtube.com/watch?v=f5MiS8iLN1I

https://www.youtube.com/watch?v=D-vOstYFhTQ
https://www.youtube.com/c/ThrottleStopGarage/videos
CF Intake Manifold, the road less travelled.
' When you get to a fork in the road, take it '
~ Yogi Berra
(IMG:style_emoticons/default/happy11.gif)
(IMG:style_emoticons/default/idea.gif)

[Mark Henry]

This is not a discussion on which Aftermarket EFI system is better, etc but rather on plenum based intake design.

Gee....that's right in the very first post. But I guess there's always that guy.

You can get around this by running TPS only, also known as AlphaN, to bypass the MAP but you lose things like altitude correction and the system is more sensitive to pedal inputs, which can be a pain on long trips. But EFI of course wins on fuel mileage. Between having to run in AlphaN or carbs, I think carbs wins on drivability as they're not as touchy to pedal inputs as the EFI in AlphaN.

Look into the feature set of Megasquirts hybrid alpha-N mode, should take care of most if not all of these issues depending on the motor.

Ive run it on an ITBd 2270 and while it is a good deal more complex to initially tune the results are pretty amazing.

I already have the SDS EM5-F6 system, not interested in anything else.
I'm not saying SDS is the best, but then MS is isn't as well, honestly I don't give a **** *** what is the best system, that's not the topic.
(IMG:style_emoticons/default/rolleyes.gif)

[Mark Henry]

Woo Hoo!

I've got two 964 plenum halves on the way, not too far away so I should have them by Friday.
No center section so I might have to do some fabrication. (IMG:style_emoticons/default/smash.gif) (IMG:style_emoticons/default/welder.gif) (IMG:style_emoticons/default/stirthepot.gif) (IMG:style_emoticons/default/popcorn[1].gif) (IMG:style_emoticons/default/smash.gif) (IMG:style_emoticons/default/welder.gif)

Something like this ...but I want the reversion flapper (IMG:style_emoticons/default/idea.gif)

(IMG:http://www.914world.com/bbs2/uploads_offsite/forums.pelicanparts.com-26-1614451322.1.jpg)

[Chris914n6]

Nissan 3.5 (fwd) and 4.0 (trucks) are easy to find. I'm sure others have similar but I know Nissans....

I'd think about 3d printing the tube to fit one in.

Or 996/box should be cheap and easy.

(IMG:http://www.914world.com/bbs2/uploads_offsite/i.ytimg.com-431-1614480547.1.jpg)

[Mark Henry]

Thanks for the tip Chris, I wouldn't have thought of looking at a Nissan for that.

[jd74914]

I've got two 964 plenum halves on the way, not too far away so I should have them by Friday.
No center section so I might have to do some fabrication. (IMG:style_emoticons/default/smash.gif) (IMG:style_emoticons/default/welder.gif) (IMG:style_emoticons/default/stirthepot.gif) (IMG:style_emoticons/default/popcorn[1].gif) (IMG:style_emoticons/default/smash.gif) (IMG:style_emoticons/default/welder.gif)

Nice!!

Pardon my ignorance, but are the 964 ports same spacing as 2.0+?

[Mark Henry]

I've got two 964 plenum halves on the way, not too far away so I should have them by Friday.
No center section so I might have to do some fabrication. (IMG:style_emoticons/default/smash.gif) (IMG:style_emoticons/default/welder.gif) (IMG:style_emoticons/default/stirthepot.gif) (IMG:style_emoticons/default/popcorn[1].gif) (IMG:style_emoticons/default/smash.gif) (IMG:style_emoticons/default/welder.gif)

Nice!!

Pardon my ignorance, but are the 964 ports same spacing as 2.0+?

I hope so (IMG:style_emoticons/default/biggrin.gif)

This mod has been done before, but mostly for turbos. You have to make new head stubs, in my case a whole new center section.
I'll know more when the two intake halves arrive later this week...I hope.

BTW If anyone wants to do this I think I know where there's another SDS EM5-F6 twinplug (or single plug) system is for sale. Basically a $3000+ EFI and ignition system, plus it includes a wideband gauge, knock sensing and Clewwitt plug wires all for under a $1000.

[JamesM]

This is not a discussion on which Aftermarket EFI system is better, etc but rather on plenum based intake design.

Gee....that's right in the very first post. But I guess there's always that guy.

You can get around this by running TPS only, also known as AlphaN, to bypass the MAP but you lose things like altitude correction and the system is more sensitive to pedal inputs, which can be a pain on long trips. But EFI of course wins on fuel mileage. Between having to run in AlphaN or carbs, I think carbs wins on drivability as they're not as touchy to pedal inputs as the EFI in AlphaN.

Look into the feature set of Megasquirts hybrid alpha-N mode, should take care of most if not all of these issues depending on the motor.

Ive run it on an ITBd 2270 and while it is a good deal more complex to initially tune the results are pretty amazing.

I already have the SDS EM5-F6 system, not interested in anything else.
I'm not saying SDS is the best, but then MS is isn't as well, honestly I don't give a **** *** what is the best system, that's not the topic.
(IMG:style_emoticons/default/rolleyes.gif)

Just throwing it out there as an interesting thing to read up on from a solution standpoint (and possibly a backup plan for anyone with unsolvable drivability issues.) I have zero opinion as to any system being the "best" they are all just different in their feature sets. As long as they get the fuel into the engine in the way you want it... who cares.

I cant offer anything more than theoretical on 6 plenum design as all my first hand experience with that is on the 4s, but that 964 setup looks like the hot ticket. The SDS intake setup looks really nice though i suspect the plenum volume of the one pictured might be less than ideal on a larger engine.

[Mark Henry]

This is not a discussion on which Aftermarket EFI system is better, etc but rather on plenum based intake design.

Gee....that's right in the very first post. But I guess there's always that guy.

You can get around this by running TPS only, also known as AlphaN, to bypass the MAP but you lose things like altitude correction and the system is more sensitive to pedal inputs, which can be a pain on long trips. But EFI of course wins on fuel mileage. Between having to run in AlphaN or carbs, I think carbs wins on drivability as they're not as touchy to pedal inputs as the EFI in AlphaN.

Look into the feature set of Megasquirts hybrid alpha-N mode, should take care of most if not all of these issues depending on the motor.

Ive run it on an ITBd 2270 and while it is a good deal more complex to initially tune the results are pretty amazing.

I already have the SDS EM5-F6 system, not interested in anything else.
I'm not saying SDS is the best, but then MS is isn't as well, honestly I don't give a **** *** what is the best system, that's not the topic.
(IMG:style_emoticons/default/rolleyes.gif)

Just throwing it out there as an interesting thing to read up on from a solution standpoint (and possibly a backup plan for anyone with unsolvable drivability issues.) I have zero opinion as to any system being the "best" they are all just different in their feature sets. As long as they get the fuel into the engine in the way you want it... who cares.

I cant offer anything more than theoretical on 6 plenum design as all my first hand experience with that is on the 4s, but that 964 setup looks like the hot ticket. The SDS intake setup looks really nice though i suspect the plenum volume of the one pictured might be less than ideal on a larger engine.

I believe the plenum formula is used within limitations, a fudge factor, reason #1 is going to be "will it fit" in the engine bay. In this case I imagine the center tubes are counted as part of the plenum volume.

Also I know the EFI system, I have about 18 years experience with an SDS EM4-F4 that I've had on 4 engines. I sold the previous 3 engines, a stock 1.8, 2.0 and a 2.0 with a C25 mild carb cam. This system is currently on my 2600cc Nickies engine, in my '67 bug, that I daily drove till I got my /6 on the road.
I've chipped the EM4 twice so far, I'm debating whether I should chip it again (just over $100) or up grade it to EM5 which is IIRC $500.

The EM5 ECU I'm using for this project I sent in for an data cable upgrade ($125), no more chip, I can download the upgrades.

[Mark Henry]

So 1 day turn around on my SDS ECU,
Daughter board installed, aluminum case drilled and new connector installed. Kit includes a download cable.
They didn't update my software but they did send me the how to and links. They did save all the map settings that I'll likely change anyways.

I now have full data logging, I'm able to download updates, use different triggers and O2 sensors and a bunch of other small features most l'll likely not use. Ross said it's basically a new ECU.

Now need my 964 intake halves and I can figure out what TB I'm going to use. I have a ford 60mm TB but I've also been looking at Honda TB's.
I want to pick a TB family with the same bolt pattern the has a couple 65mm thru 75mm sizes so I can experiment.

Just measured a 3.6 996 TB and it's 73mm. 3.2 Carrera is 63mm and the 964 3.6 is 68mm.

[GregAmy]

Mark, what tuning software is used with SDS?

[Chris914n6]

They sell generic TBs on ebay. More likely to have the same bolt pattern than different displacement OEMs.

The TB is rarely the limiting factor anyways. I'd just pick one that maths out.

[Mark Henry]

Mark, what tuning software is used with SDS?

SDS ??? do you mean the software?

Propitiatory, I'm not sure what they call it, I only see version codes but isn't that the OS? One old chip I have says 4F ver VII, I believe I have a 4F ver XIV (V14) in my old EM4-F4 4cylinder system which you have to chip to upgrade the software.
This 6 cylinder EM5-F6 has a 5F ver 25 chip set, but with the mod I can download the updates, not sure on the newest version code till I download it.

Tuning software like tuner studio?
SDS dosen't need it, you could mess up my fuel and ignition maps and I'll have it started in less than 5 minutes, be driving down the road and have the tuning good enough in 10-15 minutes to go racing , fully tuned in say 20-40 minutes. ( Note I know how to quickly scroll, it may take 3X as long for a beginner. Also doesn't count for finger problems, for storage security I once set a fuel cut at 1000rpm, next spring I forgot that I did this and that was a week of head scratching. doh!)
I ran the SDS on my 1.8 stock engine and for 4 years and except for the initial tune I never once had the programmer on the engine. My first 3 T4 engines I sold as proven running long blocks.

I've been running SDS for 18 years, this will be my 5th personal engine plus I've sold and installed a few systems and I've never had a car on a dyno. I've never seen the need for dyno time.

[Mark Henry]

My 964 intake halves arrived last night.

I have to figure out the the stubs and center section details, might take a while as I'm super busy restoring 2.0 Djet engines plus other projects this spring/summer. We'll see how much energy I have left over on the weekends.

The SDS EFI install itself only takes a weekend, it's the crank trigger and intake fabrication that sucks up the time.
I could buy off the shelf... but where's the fun in that? (IMG:style_emoticons/default/biggrin.gif)