yet another carb vs. FI question

[oredith]

well, my current motor is coming close to needing a rebuild. Compression is around the 110-120 range, blowing smoke both on and off throttle. I think i'm running at the efficiency of a 1.7, maybe pushing 1.8 since it's hard to chirp the tires from 4500rpm even with rock hard street tires that are 195/50R15.
that aside, i've got a spare setup for a stock 2.0 that has been cleaned, inspected, along with new, stock spec, heads. almost everything to build a *new* stock 2.0 motor

now the questions:

1. what's the displacement threshhold where the stock FI becomes in-effective (un-tweakable to meet the higher volume) i'd like to use 96mm p&c rather than the stock 2.0 p&C
2. can more power be had with a 2.0 setup using carbs rather than FI? would a more aggressive cam be appropriate for a 2.0? or only for higher displacement?
3. how much does gas milage suffer with carbs (something like weber 40's)

i like FI, but i'd also like to squeeze the most out of a street motor. since both (FI and weber 40) are in my garage, i'm open to either options.

so.. let the flood begin..

TIA,

Jeff

[Joe Bob]

Your best bet is to determine your needs...are you gonna race? Look at the rules first, then the competition...C/S-s C/S, C/P and AI in Zone 8 are all very competitive. They have various points for different mods. At the very least, a cam and carbs will put you in C/P and big bore will get you A/I...the A/I guys have TTOD very often.

As to carbs vs FI, FI is the most efficient...you will notice I did not say D-Jet FI....a wild cam and big bore will not be compatible with D-Jet without a LOT of trial and error. After market FI is big bucks....the more bang for the buck is carbs and a bad boy cam....

[thaag]

I'm also looking to buy a rebuilt 2.0 (or larger) motor and am curious as to what is available as far as an aggressive cam and increased displacement goes. I am definitly only interested in keeping FI and not carbs. How you guys feel about the CB Performance FI set up linked below?
http://216.111.121.85/cb/catalog.asp?ProductID=280

Cheers,

TH

[Dave at Pelican Parts]

I know one 2.2 liter 914 that is running 2.0 D-jet, with some "tweaks". I have heard rumors of a 2.4 that also ran a tweaked D-jet, but those are still so far just rumors.

I know at least one more 2055cc (the 96mm P&Cs) that runs D-jet *and* passes smog.

I also know at least one stock 2.0 with a "mild FI cam" (either Webcam or the FAT HP440, not sure which) that runs D-jet and passes smog.

You can't go very far on the cam, or you wind up with not enough vaccuum at idle. The mixture goes REALLY rich and there's nothing you can do about it. But I would guess that you could put together a 2055 with the mild cam and have it work pretty well with some tinkering.

YES you can get more power with carbs, even out of a stock-displacement motor. If you put a great lumpy cam in there, carbs or the CB Performance type EFI are the only way to get it to work reasonably. And you *will* get more power (particularly at the top end) with the big lumpy cam.

You might even be able to get a bit more power out of a stock motor with carbs. Again, this would be up at the top end, and what you get there you will most likely lose in the low- or mid-range.

Economy varies, depending on how you set up the carbs, how you drive, etc. Some folks claim 30 MPG out of carbs, which is what you can expect from the FI on a stock motor. If they're getting that much, they are probably not jetted/venturi'd/whatevered for big power.

--DD

[paulhagedorn]

Here is what I am planning on doing...
get displacement up to a 2.2L...and put a mild cam on the car. All this while staying with the stock FI

Most likely, I will have to raise the fuel pressure to something like 35 psi, and maybe think about getting the throttle body bored out a little....but I don't think that would do much. Also, I am going to probably have to get some head work done to get as much power out of the car with stock FI. I want to stay with the FI because it is along the order of set it and forget it...with some little maintenance. But, I do have a set of carbs for backup along with the fuel pump...so I can use that if necessary. I have a Bursch exhaust which seems to be a little more free flowing than stock, along with stainless steal heat exchangers.

Paul

[Germain]

You could always go with the k-jet system...
You get all the advantages of the F.I., and it can handle anything you can throw at it.

(wonders what replys this will bring)

[Bleyseng]

What cars could you get a useable K-jet system off of, that would fit without the Frankenstein/Rubegoldberg look? I have seen that page with the Type 4 motor with the volvo FI on it...looks like a nightmare!

[Germain]

Well, I think early to mid 80's Porsches had them, and VW used them on their Jettas such. I would say installing it would be "challangeing", but once it is running you should never have to worry about it again.

[Neal Colingham]

I have a 76 2.0 with 160K on it, 90PSI
compression and 40 webers. With the FI my
Dad got 30+ I get 22/23 MPH. I wish I still
had the FI. I will live with the carbs.The guy who bought all the used parts from Pelican told me that putting the FI back on is easy it's the old wiring harness that causes all the problems. He says it take alot of time chasing down all the wiring problems and most local shops will install the FI but balk at fixing all the intermittent problems after the install. Has anyone reinstalled FI after converting to carbs ?


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[Joe Bob]

Yeah, I've done it....a real pain in the toukas....best bet is to find a running 2.0 with FI and slam that in....buying a FI setup and paying for the install is sometimes more expensive than buying the whole engine with it on it.

I mostly had problems with sensors and such.

Your post mentioned 90 psi? Is that your cylinder compression? Way low if it is....should be minimum 130ish....

[tmk]

Check out this http://www.millerfi.com/


TMK
73 914S 2.1L

[JP Noonan]

Big thing about returning to FI is finding out why a carb was out on to begin with. If the PO did it right and used a Carb specific cam then you need to split the case and replace the FI compatable cam. If (like in my case) the PO had an engine fire the cam is O.K. but all the wiring needs to be replaced.

First find out what isn't OEM, see if the PO soldered in solid core house wiring (like mine) or used the stock wiring with some sort of adaptors. If the stock wiring is intack up to the relay board then it isn't too bad. In my case I had to rewire the 14 pin plug, the ignition: battery to switch to coil, the starter circut, fuel pump, and most of the wires under the dash (PO used masking tape to cover up some radio wire splices). So in my case it took a LONG time to track everything down.

BTW don't even think about it if you have trouble reading wiring diagrams like I did when I started.

Physically putting it all together is easy, there are plenty of wiring diagrams, vac hose diagrams (thanks DD), and troubleshooting articles on the net. You just need a good base to start from, if a PO starting hacking wires you are pretty much on your own.

[mike mueller]

That CB perfomance setup is nice, but damn,
$1800 is a lot of money. I know that at least one 914'er (914 Lite) is running these and he seems to like them.
Jeff, do you plan on running the headers with the new motor as well ? I would think that those could alter the differance between running the FI and carbs as well.

TMK, are you located up here in Northern California ? Your signature reminds me of an instructor I had for a PCA auto-x school.


------------------
Mike Mueller
Antioch, CA
1970 1.8
http://www.pelicanparts.com/MotorCity/mmueller/personal.html

[tmk]

Mike: Yes I am in Santa Clara. No I am not a PCA instructor but I will try to be at the auto-X in Dublin on 04/29/00. I have a marathon blue 73.

TMK
73 914S 2.1L