[SJMule]

I sent these guys a link to this page.

http://www.tpis.com/

I'd like to see one of these " Mini Ram Intakes " on a Pontiac

Mule

1973 Grand Prix SJ455
1969 GTO 428

[455Turbo]

To Mark T,

My issues are with throttle body injection (TBI).

In my opinion the limiting factor with TBI is that it uses a wet flow manifold. Fuel will fall out of suspension and puddle in the manifold. Because of this TBI systems will always be inferior to multipoint fuel injection systems, which put the fuel injector as close to the intake valve as possible. To me TBI systems retain one of the major limitations of the carburetor in spite of their high cost.

In the late 1970's and early 1980's American automobile manufacturers were forced to deal with ever stricter emissions laws. One of their first responses was the feedback carburetor. This used a computer, an oxygen sensor, and a solenoid valve in the carb to control fuel mixture.

As emissions requirements got even more strict the feedback carb proved to be inadequate. The next, and logical step, was the throttle body injector. TBI replaced carbs and allowed for much better mixture control. Unfortunately they still relied on wet flow manifolds so the driveability wasn't great. Anyone who has compared side by side GM's 1984 Cross Fire Injected Corvette (throttle body) with the 1985 Tuned Port Injection (multi point injection) will understand the difference in performance.

In the mid 80's GM and Ford got multi port injection right. Throttle response was back and performance levels were increasing.

In my opinion TBI will never provide the driveability of multi point fuel injection. TBI is almost as expensive to implement as multipoint injection because it still requires a computer, sensors, fuel pump, filter and plumbing. For these reasons I feel that if someone is going to spend the money they should spend a little bit more and go for a multi point injection system. If not then save the money and stick with a carburetor.

[PonchoV8]

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by Robert Herndon:
I can't comment on Pontiacs with EFI, but I can on BMW and Porsche.

The shop I work for has taken a number of the BMW 'M' 4-Valve Six-Cylinders and converted them to Weber carburetors.

The difference in power output is unreal. The EFI doesn't even come close.

There is a reduction in smoothness at part throttle and the engine is obviously more tempermental when cold, but HP and TQ are higher than even the motors with upgraded throttle bodies, injectors and ECU upgrades.

Years ago, I also recall the Rochester Fuel Injected Corvette (375 HP) produced much less HP and TQ on the dyno than the carbureted (365 HP) version of the venerable 327.

Obviously, EFI is all-around the best choice for driveability and economy, but I see some serious limits to its airflow potential in most applications.

Additionally, when speaking of EFI on a Pontiac, most systems I have seen will not allow use of stock A/C.

Why not just adapt the Tune Port Assembly from a SBC for use on the Pontiac? The port arrangement is similar and I am sure the angularity of the cylinder deck could be compensated for with a properly fabricated intake manifold.

I personally, would like to see a 4V TBI Unit that would bolt on in place of the stock Q-Jet and allow use of stock A/C and Alternator Brackets.

Just curious...Robert

"If I had better junk in my garage, I know I could go faster."<HR></BLOCKQUOTE>

Robert, those Webbers will give excellent torque & hp, but fuel economy will be cut almost in half (big problem for a manufacturer). They're temperamental to get right as well. I have a little background on them from Nissan Z inline 6 (L6) usage. I don't know much about the BMW electronics, but often times the early efi systems were very limited and not able to reprogram until later systems. If it has the flapper door air-flow-meter(AFM), that's a restriction as well. For instance the 81-83 turbo Zs (limited to about 250hp) are modified by reprogramming a later year ECU, replacing the flapper-door (AFM) with an MAF from a Ford Cobra to get above 300-350 hp.

A/C can be adapted like anything else. If you use system with timing control via a crank trigger, A/C or electric fans can wack it out thru interference, but you just have to shield the trigger and you should be fine--unless I'm not thinking of something here.

The sbc system adapted to a 400+cid low rpm torque developing Pontiac? Don't know about that one. You'd have to upgrade several items, so you might as well have a custom built system.

Having bungs put in an aluminum intake isn't a big deal and would be worth the benefits. I would have no problem using salvaged injectors from another application as long as they were refreshed by a pro service like Marsh Injector Service (I think that's the name).

Doug

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[This message was edited by PonchoV8]



www.geocities.com/yqtnxnb

[This message was edited by PonchoV8 on December 14, 2003 at 01:14 PM.]

[PonchoV8]

As far as injectors, there a lot of guys with 4 and 6 cyl cars that upgrade to higher flowing ones and will almost give away the used, perfectly good, high flow injs. Since we have more cylinders, we don't have to have as high a cc flow per cyl as they do making them really good choices for us. You just have to find a couple sets (which is never a problem). I'd have them refreshed by Marsh Injector Service where they will give you a flow sheet for each injector before plugging them in.

Injs come in top feed or side feed applications and the fittings can be either barb or o-ring. A fuel rail is a minor issue as well. Arizona Speed and Marine sells it cheap.

Doug

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[This message was edited by PonchoV8]



www.geocities.com/yqtnxnb

[SJMule]

These guys do some custom stuff as well.

http://force-efi.com/

The intake pictured isn't a Pontiac, does make you wonder though.

A dual quad Edelbrock with EFI would be very trick

Mule

1973 Grand Prix SJ455
1969 GTO 428

[FirebirdDave]

I found a low cost alternative TBI. I met a guy at the junkyard today from Columbus GA. He has a website GM fuel injection
He claims one of the first cars he injected was a 68 lemans with a Pontiac 350. He sells a system for around 950. He also offers a book that tells how to do it yourself for $30. He told me it can be done with junkyard parts for around $350. Not port injection but well worth the cost.

69Firebird roundport/roller455
70Catalina 455
72Skylark Buick 455
89 Iroc 305 stock 192RWHP/263RWTQ
I cant leave anything alone.