For flat sixes: Webers v MFI v EFI, Ecologically speaking… Options

[mb911]

I plan to do 1 of 2 things on my car.. Use my webers as Throttle body's and use the MFI ports in the heads for injector ports or use my restored 3.2 intake and make adapters for the heads and likly use the Bitz racing setup with Megasquirt.. Pretty cheap EFI at that point.

[horizontally-opposed]

A problem with carbs and MFI is that a lot of unatomized fuel ends up in the crankcase over the miles. 3000 mile oil changes become a requirement.
Also, the cheapest decent throttle bodies are motorcycle... 1999 to 2000 GSX-R 750 or 1000 depending on the size you want. Triumph ITBs require a manifold. I did this on a 3.2 back in 2012 with megasquirt (which I'll never use again).

You've touched on a couple of the things that put carbs or MFI ahead of most options for a small flat six—development and support, both in the short term and the long term. Right now, of the aftermarket stuff, what is likely to still be around with parts and support in the long run? There are some very attractive custom ITB and EFI products for old Porsches out there, but it seems we have several developers vying for a slice of a fairly small pie and I wonder what living with the products in the long arc will be like. Thinking of race cars that require the upkeep of a 386 or 486 laptop to run in 2020. You hope for the best, but if it stops running 12-17 years from now?

Suzuki GSX-R750 ITBs are actually pretty interesting, as I suspect those will be supported for a very long time with new parts and still possible to look for used parts if you're in a pinch. Manifolds and other machined parts to adapt them are, so long as they're well made, unlikely to be problematic (and can be replicated down the road if need be). So a Suzuki setup might match or even beat PMOs in that regard.

Which gets back to the brain/software/etc. All of the EFI setups are going to offer superior performance over carbs (and MFI), I am just thinking about those "un-sexy" factors like reliability, fixability, support, etc. in the long term. Don't have a position on it yet, but very much appreciate the conversation going on here.

[sixnotfour]

https://www.x-faktory.com/store/p3/EFI_Kit_RHD-EFI-001_.html

and this one, I bought a set up for under 1k
https://www.ebay.com/itm/Triumph-ITB-Setup-...qAAAOSwQDhbXN0H

[jd74914]

I did this on a 3.2 back in 2012 with megasquirt (which I'll never use again).

Which gets back to the brain/software/etc. All of the EFI setups are going to offer superior performance over carbs (and MFI), I am just thinking about those "un-sexy" factors like reliability, fixability, support, etc. in the long term. Don't have a position on it yet, but very much appreciate the conversation going on here.

As much as DIY people online like to say, Megasquirt is not really a 20+ year kind of thing. It’s really just not hardened, and IMO many of the control strategies are rather lacking, as is some of the hardware signal processing. I think most people who are really pro MS haven’t use high end stuff (think Motec, Life, etc) which is constructed with much stouter hardware and will last for decades. I’d be shocked to hear about something like a Life F88 which has failed even over 20 years. The computer insolence part is certainly a real issue. MS is nice here because the under community forced it to be up to date. That said, in general the guys carrying around a 486 have hardware which is now 30+ years old. It’s surprising they’d really ever have to touch it after so many years of tuning. Chances are if you do with an established ECU company, you’ll have hardware support for a long time.

I’m not a high AEM fan, even with the Infinity (probably pick just about everyone else in the high end market over them), but the Rasant package looks really clean.

[roblav1]

I paid $300 for 8 low mileage Suzuki ITBs, with throttle cables and sensors. Then made adapters to attach them directly to the heads. They also needed spaced out more, so I also made spacers and lengthened the throttle mechanisms and fuel rails. Those ITBs are Keihin, so a ton of injector options. Honda S2000 injectors would work great for a 3 liter engine. The throttle cables are perfect length for both to attach to the lever bell crank on top of the engine.
Concur with lack of hardening on megasquirt.

[sixnotfour]

http://forums.pelicanparts.com/search.php?do=process

[mepstein]

I would give Al a call about his x-faktory kit and ask him what it would cost to get it on your car and tuned. It's not cheap but seems to be a well proven solution and you can sell your Webers for 2-3K to make back some of the cash.

[sixnotfour]

Als a great guy , would make a great article too.
Is was a member ..he sold his 914

[Mark Henry]

I plan to do 1 of 2 things on my car.. Use my webers as Throttle body's and use the MFI ports in the heads for injector ports or use my restored 3.2 intake and make adapters for the heads and likly use the Bitz racing setup with Megasquirt.. Pretty cheap EFI at that point.

(IMG:style_emoticons/default/agree.gif) that you would be better to sell the webers and use TB's from a Triumph bike. If you still want to use the carb bodies I'd get a pair of Zeinths.

With ITB's and big carb cams you will have to run MS in AlphaN (SDS "TPS only") because you won't have good enough vacuum to run the MAP sensor. AlphaN works but tends to make the throttle an on/off switch which is a PITA at lower RPM's such as stop and go traffic. It also disables altitude AFR correction because it works off the MAP sensor.

Big cams with large duration is where MFI and carbs shine, this is especially true for hot street engine that sees a fair bit of time at lower RPM. My bug and 914 I run real hot cams, the /4 has SDS EFI with a 163/86B cam and my six 120/104 web cams, The /4 cam with 46mm ITB's has to run in TPS only. The carbs have a much smoother on/off transition compared to the FI.

This is for a /4 but you can see how much work it took me to adapt Suzuki GSX-R TB's to carb manifolds in my motorcycle TB's thread.

[roblav1]

I've got the same cams as Mark in my Carrera 3.0 engine and decided to run 46 PMO. I've spent enough time on this car already and the PMOs, all new and properly jetted, will provide me a good induction solution at minimal effort. And why spend money and time on old 40IDA3C that will need rebuilt and rejetted when for a bit more money you can get the brand new PMO setup?

[Mark Henry]

I've got the same cams as Mark in my Carrera 3.0 engine and decided to run 46 PMO. I've spent enough time on this car already and the PMOs, all new and properly jetted, will provide me a good induction solution at minimal effort. And why spend money and time on old 40IDA3C that will need rebuilt and rejetted when for a bit more money you can get the brand new PMO setup?

Ben already has the weber carbs, as long as the throttle shafts are good and he doesn't care about the MPG they can be made to run just as smooth as FI.
My webers for a twin plug 3.0 have 34mm venturis, 155 main jets, F3 emulsion tubes, 180 air correction, 55 idle, tuned with a WB meter and runs a solid 12.7 AFR throughout the RPMs. Paul Abbott confirmed this was about perfect AFR. I'd suggest the same set-up but your main jets may be a bit smaller.

But this is where the bulk of the fuel mileage penalty happens, the FI can lean out the AFR at cruise, where as the carb is locked into the jet sizes.

[roblav1]

I've got the same cams as Mark in my Carrera 3.0 engine and decided to run 46 PMO. I've spent enough time on this car already and the PMOs, all new and properly jetted, will provide me a good induction solution at minimal effort. And why spend money and time on old 40IDA3C that will need rebuilt and rejetted when for a bit more money you can get the brand new PMO setup?

Ben already has the weber carbs, as long as the throttle shafts are good and he doesn't care about the MPG they can be made to run just as smooth as FI.
My webers for a twin plug 3.0 have 34mm venturis, 155 main jets, F3 emulsion tubes, 180 air correction, 55 idle, tuned with a WB meter and runs a solid 12.7 AFR throughout the RPMs. Paul Abbott confirmed this was about perfect AFR. I'd suggest the same set-up but your main jets may be a bit smaller.

But this is where the bulk of the fuel mileage penalty happens, the FI can lean out the AFR at cruise, where as the carb is locked into the jet sizes.

Here's the going in PMO 46 setup:
Vents 38
Mains 155
Air Correction 185
Idle 55
Idle airs 130
E tubes F16

We're not that far off. With my larger vents, looks like I may be a little leaner at higher rpm. Engine has the larger 3.0 intake ports, running 9.5 compression single plug. I timed the cams per spec, but given the cam sprocket pin placement, they are very slightly retarded.

I'd be real happy with your AFRs!

[horizontally-opposed]

I can see where PMO carbs are attractive to someone building an engine or a car for all the reasons listed, but they don't make sense for me.

I rolled the dice and bought a set of used Webers from Pelican Parts years ago for less than what cores cost now. Had them gone through by someone very familiar with Webers before they went on the car for seals, etc. Only suspect thing was a bit of wear on one shaft...but it wasn't enough to be worth dealing with. After the better part of a day on a chassis dyno and some subsequent fiddling, they're good. Car starts first try if it's been driven within the last few days, and will start in the first couple of tries if it's been sitting—and this is without the luxury of a 914-6 choke. Engine pulls nicely from idle to 6000+, and is pretty hard to catch out. Jump on the gas too quickly and you can sometimes get ahead of the carbs, but that's about the only niggle. I'm happy in all those regards.

New PMOs would need to be dialed in, and present most of the same problems. This thread has me moving the goalposts away from MFI (cost, emissions, etc) and towards EFI, possibly on PMO TBs to keep the factory 914-6 airbox—which I really like—and because I suspect parts & support will be available for a long time to come.

That leaves which engine management system. A lot of good inputs here to consider.

[echocanyons]

I have essentially the same setup as Steve in my 914 using the Rasant harness and the AEM infinity EMS.
As far as maximizing power and tune ability this is the only way to go.
Also, by far the cheapest option to go to twin plugs.

Definitely not cheap though.

[Chris914n6]

MS3pro is a completely different system than the MS 'kits'. It was designed and built to be higher end and competes with systems more than it's $1100 price tag.

[horizontally-opposed]

I have essentially the same setup as Steve in my 914 using the Rasant harness and the AEM infinity EMS.
As far as maximizing power and tune ability this is the only way to go.
Also, by far the cheapest option to go to twin plugs.

Definitely not cheap though.

Thanks for posting this—looks great, and your and Steve's positive experiences go a long way with me. Sounds like, for me anyway, EFI > carbs or MFI.

I tend to think of EFI as a "$10-15k" hurdle, but selling my running/setup Webers and Clewett/Electromotive crankfire ignition system may offset or even cover the 40mm PMO EFI setup—meaning the hurdle is more like $4850-$7200~ for AEM or Motec plus the time to do the swap and set it up. Don't need twin plugs or more power, but better drivability from a cleaner, crisper, more efficient engine certainly has its appeal.

Again, thanks for the input, everyone. This is turning out to be a very informative thread.