I was thinking about going with a Holley Pro-jection throttle body injection system to replace my double pumper holley. I have no problem with my carburator, except that it uses a lot of gas. Any good or bad expirences with Holley Pro-jection?

I don't but I have another angle for you.

I don't know your engine, but the big 2 barrel carbs do better in the gas mileage department and do better in the grunt end of your revs.

The Holley 2300 comes in 500 cfm. Master Tuner had some good results with his 2 barrel. I'm using the 350 cfm.

It might be worth a look.

Arn

im pretty certin that 500CFM is not big enough for a 400CI V8 i feel lousy only running a 650 Carter on my 355

A 400 with a 2bbl carb?? Yeah, that'll kill power, and the venturies of a 500 are still larger than most 4bbl primaries, so mileage gain is questionable. (Not to mention the fact those are racing, not economy carbs.) 2bbls are rated at 3" vacuum, while 4bbls are rated at 1.5", so the ratings are not directly comparable. Rated at 1.5" vacuum, the 500 would only be a 350. The 350 would be a 250 if rated at 1.5".

I have run a Pro-Jection unit, but it was the old analog one, and the car had a solid cam so I can't address fuel mileage issues. I can tell you it made the car start and run nicely for the type of motor it was. They've come a long way since that unit.

GL

[This message has been edited by Tugboat (edited 07-08-2004).]

I'm thinking more like the aftermarket 670cfm 2 barrel TBI....or better yet, the 900cfm 4 barrel TBI.

I like the Holley Pro-jection setups because they are a bolt in replacement for a carburator.

I have had two analog 670cfm units one on a stout 350 10 years ago and one currently on my 4.5 cadillac V8 - both 5 speed cars. The older analog units are much better for throttle response and MPG than high HP applications. The analog units are very, very basic and only good for around 300 hp. My main gripe with them is that they do not monitor engine load (at least the old units don't), so the fuel curve is strictly RPM and TPS based. The knobs help dial it in, but it is still less than ideal.

I think the newer units are much more precise and more expensive as well.

Fieroguru- what kind of gas mileage are you getting with your TBI 4.5? I am finishing up an 85 GT that we put a TBI 4.5/auto overdrive into and was wondering what to expect.

quote Originally posted by fieroguru: I have had two analog 670cfm units one on a stout 350 10 years ago and one currently on my 4.5 cadillac V8 - both 5 speed cars. The older analog units are much better for throttle response and MPG than high HP applications. The analog units are very, very basic and only good for around 300 hp. My main gripe with them is that they do not monitor engine load (at least the old units don't), so the fuel curve is strictly RPM and TPS based. The knobs help dial it in, but it is still less than ideal. I think the newer units are much more precise and more expensive as well.

Thanks for the input! Do you think that it was a big improvement over a carb? or was it about the same

I have never even checked the mileage on the 4.5 in the roadster. It is a topless car I bebop around in on nice days and I have never focused on the mileage. The 350 in my 86 IROC w/5 speed and 3.43 gears got 17ish mpg.

My 88 Fiero with Vortec headed 350 and ZZ4 roller cam gets over 20 mpg on the highway with a 600 edelbrock.

Swapping back and forth between the cars, the Projection on the roadster provides instant power the millisecond the pedal is pushed - there is no comparison between the off idle torque of the projected 4.5 and the carbed 350 - the projection wins hands down. This sensation was also the case in the IROC - once the projection was added - I started to go through tires like crazy - but on the 350 the projection pretty much gave up the ghost at 4700 rpm - where I exceeded the HP rating of the 670 unit. Where as the carb may be slower down low, it continues to scream as the revs climb.

The projection units are not intended for high RPM or high HP applications.

I would not use a projection unit on a SBC in a fiero unless it was just going to be cruiser, for a bruiser - go carb or EFI.

While I am open to admit the limitations of the projection units, I am a big fan of them and currently looking for another projection unit for the 460 in my carhauler. It will never see full throttle and the off idle power, response and increased MPG would be ideal for this application. The last two i have purchased were New In Box and I paid $350 both times... so the price can't be beat!

Back to the question at hand....
I had the Projection 4Di on a 454 in my 3/4 ton Suburban and when it worked, it was okay. I learned a lot about fuel injection with it. I also learned pushing a Suburban out of traffic because the ECM went spastic really stinks. There was no 'limp home mode' built into the ecm and if any sensor went out, you walk. It would eat an oxygen sensor every couple of weeks and if you unplugged the burnt sensor, it would putter enough to get out of the road. The sensors look like GM parts, but are different enough that an over the counter part will not fit so stopping at the local parts store to pick up a TPS is out of the question. The UPS guy and I were on a first name basis for a while because of all the deliveries from Summit. The Holley does not have any 'learning' like the GM systems do. It is always compensating for differences in the fuel map vs what the engine needs where the GM system 'learns' to fine tune the fuel.
If I had it to do over again, I would not spend the $$$$ for the Holley system when an OEM tbi system will work. On the wife's minivan with the Caddy 4.5, I used the tbi and ecm for a Chevy truck (a '747 ecm) and the van wiring harness. It has been in service for nearly a year and does a nice job of pushing the little van down the highway.
The 85 GT that I am finishing up also has a TBI 4.5 running the truck throttle body and ecm. I moved a handful of pins around in the ecm connectors and rearranged the engine wiring harness so it fit the v8. It was not too hard, just time consuming. The tbi system is fairly easy to tune and very forgiving. I am running the Fiero with a copy of the chip I made for the minivan and even though the Fiero has larger injectors from a 350 (instead of a 4.3 v6like the van), it ran pretty good from the start. If you find a TBI from a big block truck, it should be about right for your engine. The linkage is a little different, but workable. I used the v6 Fiero throttle cable and it fits the tbi like it was made for it. I have less than $150 invested in the fuel system and if anything goes wrong while out on the road, you can find the parts you need almost anywhere.

quote Originally posted by fieroguru: The projection units are not intended for high RPM or high HP applications.

Depends on which one you use. Mine's supposed to be good for 900 CFM and 600 HP. Not for less than 350 CID or 300HP. I haven't tested it to those limits, so I don't know for sure...

I had read somewhere that Holley used GM sensors for availability purposes, but magazines are often wrong. Mine only uses TPS and temp, along with a tach signal, and I never had to replace either, so I don't know for sure.

GL

I have the 670 pro-jection on my Scout with a 392. It replaced a Carter Thermoquad which always ran well, but like you I was looking for better fuel economy. The basic units (~$700) have no O2 sensor or MAP sensor. The O2 sensor can be added to the system for around $100 and I have one on my Scout, again looking for better mileage.

I put the unit on then drove the Scout pulling my car trailer and the Finale to Detroit last year. I noticed right away that it had a problem of slow starting (long crank time) when hot. This got progressively worse (thankfully after we came back from Detroit) until it simply wouldn't start hot. What was happening was when the engine was hot, and you shut it off, you lost the flow of cooling fuel through the injectors and they would stick open. When you turned the key on the next time to start it, you had a flooded condition, enough so that at one point I almost caught the entire thing on fire.

At first Holley denied any problems with the injectors (you're the only one having this problem, etc., etc., etc.) but after I had an engine compartment fire they then wanted pictures of the injectors and the p/n on them. After sending them those, the said they were "early" injectors and replaced them. I've had no problems since the new injectors went in.

Driving impressions are very good. The throttle response is excellent, so much so that someone driving my Scout for the first time generally chirps the tires when they take off, just trying to drive normally. The throttle response is so crisp it takes some getting used to.

I didn't gain much in the economy department. Remember the Scout is a very heavy vehicle (probably close to a Suburban) and has the aerodynamics of a brick. If I drive it 70 mph, I usually get about 13 mpg. If I slow down to 55-60, it goes up to about 15 mpg. These are only 1/2 to 1 mpg better than the Thermoquad was getting for me.

I never tried it without the O2 sensor so I don't know how much difference having that makes. Tuning of the analog ones is pretty simple. The only thing I ever have to adjust is I move my "choke" setting about 1/8 turn richer when winter gets here. It controls not just how much fuel is metered when cold, but also how long and when the fast idle kicks off, so leaning it a bit in summer makes it a little nicer to drive after initial start up.

All together, I spent about $1,000 on the system with fuel line, relays, system, O2, etc. That includes all the odds and ends. I think it was worth it for the throttle response and also the instant starting in the mornings.

One final negative, if you use the O2 sensor, you might have to pull your timing back a degree or so. At cruise, it leans the system out significantly, so much so that if you're pulling a heavy load up a hill, etc., it will ping some. I'm planning to put an MSD timing unit on it so I can pull back my timing from the cab to help with that at some point. Right now I'm just driving it and enjoying it.

John Stricker

quote Originally posted by v8fiero400: Thanks for the input! Do you think that it was a big improvement over a carb? or was it about the same