Finally drove MFI

[winders]

Originally Posted by cmcfaul

MFI is a supercharger for fuel injection.

Huh? MFI is archaic and not better than EFI. Sorry.....

[winders]

Originally Posted by WP0ZZZ

What causes the extra latency....

There is none......

[Jeff Higgins]

Originally Posted by winders

Huh? MFI is archaic and not better than EFI. Sorry.....

Agreed. We have now, however, finished the first lap. Gone full circle. This was covered earlier in this very thread. We are now getting down to the most sacred of Pelican traditions - "last wordism".

Originally Posted by winders

There is none......

Yes, there is. Again, already discussed right here, in this very thread. I'll simply agree to disagree, and sign out.

For those still wondering, all I can say is "drive one". Like Superman did. Don't listen to us, make your own decision. It took Superman very little time to do that. It probably won't take any of you all that long either. It really is that noticeable. But don't take my word for it. Just drive one...

See ya...

[winders]

Originally Posted by Jeff Higgins

For those still wondering, all I can say is "drive one".

I have. If you compare MFI to CIS or any other single throttle body setup, yes, the throttle response difference is huge. Compare MFI to a well setup EFI setup with ITBs and I would hate to have to live off the difference because there isn't any.

The higher fuel pressure of MFI atomizing fuel better is negated by modern injector technology.

MFI does nothing better than EFI with ITBs except rigidly not adapt to anything. Oh, MFI will give you more headaches too....

Look, if you want or need MFI, go for it. But let's not spread fairy tails about how MFI has better throttle response than a well setup EFI system with ITBs.

[acme911]

Originally Posted by winders

I have. If you compare MFI to CIS or any other single throttle body setup, yes, the throttle response difference is huge. Compare MFI to a well setup EFI setup with ITBs and I would hate to have to live off the difference because there isn't any.

The higher fuel pressure of MFI atomizing fuel better is negated by modern injector technology.

MFI does nothing better than EFI with ITBs except rigidly not adapt to anything. Oh, MFI will give you more headaches too....

Look, if you want or need MFI, go for it. But let's not spread fairly tails about how MFI has better throttle response than a well setup EFI system with ITBs.

I agree with everything Winder said. Why don’t we have a shoot out. Get some MFI and some EFI/ITBs together and pick a back road. Have some fun and a great excuse to drive our cars.

MFI for historic reasons yes. For cool factor sure.
EFI/ITBs for driveabilty and flexibility.

[Coastr]

Originally Posted by WP0ZZZ

What causes the extra latency that makes the throttle response of an EFI/ITB engine to be worse than that of an MFI engine?

There is none. Butt dyno stuff. You could overfuel on throttle opening to get the same smell and feel. It’s neat to think that a cable and pump system can react faster than a microprocessor but it’s just not true. Modern Efi can do millions of calculations per second. Modern injectors are very precise.

[Shaun @ Tru6]

Originally Posted by Jeff Higgins

Yeah, imagine being lucky enough to somewhat, kinda sorta, combine all of that. Things just kind of fell into place for me. Guys were giving me take-off MFI systems when neither they, nor their mechanics, could figure out how to make them work. I have several fully functional systems, of various specifications (T, E, and S of different displacements) sitting on shelves in my garage. Free. All of it. It only made sense to try to make it work on whatever hot rod I was going to build. Which, in the end, turned out to be a 3.0 liter, 11:1 compression, custom cammed (to my specifications, via a custom grind from John Dougherty), twin plugged beast. 2,200 pounds with its 100 liter tank full:

your MFI work is the stuff of legends Jeff.

[cmcfaul]

[Jonny042]

Originally Posted by WP0ZZZ

What causes the extra latency that makes the throttle response of an EFI/ITB engine to be worse than that of an MFI engine?

Theoretically the scan times of a modern processor should be fast enough to work faster than you can move your foot, but in practice there are always built-in delays to smooth input signals. On top of that, even as memory becomes cheaper and processors become more capable and faster the temptation is to load them down with data-logging every signal channel so the advantage of more modern processors might be lost.

On an MFI system, if you move your foot to introduce more air into the system, the amount of fuel will increase on the very next intake stroke with NO delay. At 5000RPM you are never more than 4 milliseconds from this happening - which is pretty quick even by modern standards.

[jac1976]

Why is it some people on this forum are always trying to pick a fight? It’s tiresome.

[wjdunham]

I still play tube guitar amplifiers, when for 1/10th the cost I can buy a software modeling amp for my laptop...

[acme911]

I'm not saying one is better than another. I really would like to get some guys together and have some fun. Feel the difference back to back. For that matter lets get some Turbos, CIS and Carbed cars out too.

Heck, I'm in my sixties, still listen to Vinyl played back on stereo's from the 70's. But, like the ease of streaming media. Majority of my carpenter and mechanics tools are cordless. Even moving away from pneumatics. Worked on all my cars and bikes. Owned around 90 vehicles, 4 and 2 wheeled. I'd like to think we're all on this forum to share ideas, learn and have some fun.

I have great respect for guys who maintain their cars to original factory. Also respect guys who push the limits of todays innovations. We have a smorgasbord of exiting cars both past and present.

As far as my car. Just wanted to have the convenience of EFI and be able to jump in and drive. Simplicity and easier to maintain. I haven't had to do a thing to the motor since finishing it 3 years ago. Just change the oil and filters. Changed the plugs before final tune and then checked the plugs after the break in. No fouling. I had a '76 and couldn't do anything with it out here in Calif.

[winders]

Modern EFI with ITBs is better than MFI. That doesn't mean I am saying you should not use MFI. All I am saying is this idea that MFI has magical throttle response that no other system has is not true.

I use a tube pre-amp and a tube amp in my 2 channel stereo system. I did give up on vinyl though as I can't deal with the required rituals anymore....

[kltarga72]

Originally Posted by Jeff Higgins

Absolutely!! Now you are starting to understand. :



I've always wondered why so many guys who are ostensibly seeking some kind of a "vintage sports car experience" spend so much money, time, and effort to modernize them. Not just induction systems, but but modern brakes (Boxster caliper kits), modern suspension (coil overs, pick up point relocation, etc.), massive power increases (3.6's in early cars, etc.), modern A/C, and on and on. More power to 'em, just not for me. We all enjoy this hobby in our own way. That's what is important. Of course this "bench racing" is a large part of it as well. Fun stuff...

Agree 100%

[manbridge 74]

Below is from someone else but I’m in agreement...

I consider myself a hard-core hard-a$$ about running old cars --- especially old Porsches. I'm not really interested in performance or usability or comfort in any absolute sense. If I was . . . I have lots of other choices. But I chose an old Porsche, and I specifically sought mine out for, among other things, its MFI. I'm interested in driving and living with and understanding something that I view, not just as a car, or a possession, but as an artifact --- something from another time.

So I don't really care if the car is difficult or flawed . . . as long as it's still what it started out as, still authentic . . . still the car that Porsche built.

[manbridge 74]

Above is a spark plug from my 2.7RS with 1600 miles of 95F degree highway driving this last weekend. 22 mpg at 3500-4000rpm, 80-90 mph. Dialed in right from the factory manual....

[manbridge 74]

Possibly a better pic.....

[winders]

Hey, if you want to run MFI for any or all of these reasons, go for it:

1. It came with your 911
2. You think it is cool
3. You had the parts lying around
4. You want or have to be period correct with fuel injection
5. You want the best throttle response while being period correct
6. You just want to run MFI

I think everyone here agrees….

[Bill Douglas]

You guys think MFI and EFI are good, you should try CIS.





And if you don't like CIS how about KFC.





.

[andoni510]

Originally Posted by Bill Douglas

You guys think MFI and EFI are good, you should try CIS.





And if you don't like CIS how about KFC.





.

Winner winner Chicken dinner