what FI for my engine?

[61ragtop]

I was wondering what is a good efi system to use? I am thinking of switching to help emissions and MPG on m motor.

I am not familiar with it at all but was thinking a system with fuel rails and individual injectors for each cylinder would be more efficient than a throttle body injection?

I would also in the future like to possibly step up to a super charger if $$$$ ever allows it too, if that changes any choices.

Here is what I am working with currently.......

ENGINE
-383 stroker 442hp/470ft lbs of torque )
-Chevy 350 bored 30 over and stroked to 383ci
-Scat crank 3.75 Stroke Cast 9000 series
-Scat 5.7 forged I beam rods with 7/16 arp cap screws
-Forged Flat top Probe Sportsman Race Series Pistons
-Comp Cams Roller Cam Duration-Intake 230deg Exhaust 236deg @ .050 / Lift Int .510 Exh .520 and 110 lobe separation
-Air Flow Research 195cc Heads 74cc chambers
-9.7:1 compression
-Headman Block Hugger Headers
-Holley fuel pump
-Speed Demon 750cfm Carb Vacuum secondaries
-Polished Air gap Intake
-Edelbrock aluminum water pump
-MSD Plug Wires
-All Bolts Are ARP
-Mini Starter
-Edelbrock double roller timing set
-Comp cams roller lifters
-Crane cams roller rockers
-Full Mandrel bent Flowmaster American Thunder exhaust With 50 series deltaflow mufflers


CHASSIS
-700r4 tranny
-B+M super cooler tranny cooler
-9 inch ford rear end
-Center Section With Motive 3.89 Gears And Auburn Pro series limited slip
-Air lift easy street air ride kit
-4 wheel disc brakes
-18x7 in front and 20x8.5 rear Intro Twisted Vista Wheels -Boxed trailing arms in rear by spirit engineering

And the dyno specs....

Intake center line 105 1/2
jets 76 front 85 rear
vac sec spring short yellow
timing 35 deg
RPM----HP----TQ----A/F--- Vol Eff%

3900 - 328 - 442 - 13.3 - 97
4000 - 340 - 447 - 14.0 - 97
4100 - 356 - 456 - 14.2 - 97.3
4200 - 370 - 462 - 14.0 - 97.5
4300 - 381 - 465 - 13.9 - 97.5
4400 - 390 - 465 - 13.9 - 97.4
4500 - 397 - 463 - 13.8 - 97.4
4600 - 404 - 461 - 13.7 - 97.2
4700 - 410 - 458 - 13.8 - 97.1
4800 - 416 - 465 - 13.8 - 96.9
4900 - 422 - 452 - 13.8 - 96.7
5000 - 427 - 448 - 13.8 - 96.3
5100 - 430 - 443 - 13.8 - 95.8
5200 - 433 - 437 - 13.9 - 95.2
5300 - 435 - 431 - 13.9 - 94.9
5400 - 436 - 424 - 13.8 - 94.6
5500 - 437 - 418 - 13.9 - 94.3
5600 - 439 - 411 - 14.0 - 94.0
5700 - 440 - 406 - 13.9 - 93.5
5800 - 442 - 400 - 13.9 - 92.8
5900 - 442 - 393 - 14.0 - 92.1

Thanks.......
6000 - 440 - 385 - 14.0 - 91.5

[86Cutlass383SR]

You have many options to fuel inject your Impala. I'll give an overview of some of the systems. Others more knowlegible can fill in the gaps.

OEM injection:

You can convert to factory injection using either a factory harness or an aftermarket harness.

TPI injection was offered from 1985 - 1992 on Camaro's, Firebird's, and Corvettes. From 85 - 89 was Mass Air Flow Systems. 90 - 92 was Speed Density. Both have their pros/cons.

You can also buy aftermarket parts to compliment and/or completely replace the factory parts. The factory TPI consists of a base manifold, a pair of runners, and a plenum. A throttle body bolts to the front of the plenum. A factory style system only flows well to 4500 - 5000 prm due to the long runners. Porting the plenum and buying larger diameter runner tubes will help but they have their limits. Supercharging can overcome this as it forces the airflow thru. Larger injectors and throttle bodies can also be bought for more fuel flow and airflow.

The TPIS MiniRam is simular to the Chevy LT1 intake. The Holley StealthRam is simular to a Tunnel Ram intake. Both are complete in the fact they replace the intake, runners, and plenum all in one peice. They still use the Chevy wiring and sensors. The throttle body still bolts to the front. Both are good systems and can be bought with just the manifold or a complete EFI swap kit with all sensors and wiring. Both these systems have shorter runner built into the intake and can result in higher rpm capability.

All of these are the Multi-Port type with an injector for each cylinder. These Chevy injections use a chip contained in the ECM (Electronic Control Module). You can have aftermarket companies tune these by mail order or you can buy the equipment to tune these yourself cheaper than 1 aftermarket chip. If you are good at tuning or catch on to tuning basics easily, this is the best option.

Aftermarket Injection:

Many companies markets fuel injection that can be either adapted to a stock style single plane intake or bought with one already converted. They too, have an injector for each cylinder. They come with the harness needed to run the system and contain an aftermarket ECM that can be tuned with a laptop. The throttle body on these sit on top and resemble a carb but only flow and meter in air. All injection systems that have the injectors near the head flow air only thru the intake and are called *dry flow* as the intake only flows air. The fuel is added near the head.

There is also the injection system that have the injectors near where the carb would sit. This is the throttle body injection you said you wanted to avoid, and for good reason. They are just basically an intelligent carb. But still just basically a carb. They have the same airflow problems a carb has such as flow and fuel dropout with low velocity. They typically have either 2 or 4 injectors located where the carb sits. Good for a stock replacement but for performance, steer away from these. Not to be confused with the throttle body used on a multi-port system.

I hope all this ins't too overwhelming. It is just a small overview on EFI. A good injection system will make you forget all about carbs. When I swapped a TPI into my car (also AFR 383 powered BTW) it wasn't even tuned correctly but it was still better than any new carb I ever had. I can only imagine how good it would have been if it was. I'm getting ready to drop my rebuilt 383 back in my car with a few additions added so my tuning will start all over again. I plan on getting PCMforless.com to burn me an initial tune for a safe startup.

[61ragtop]

Thanks for the info Doug, it was a good read. I am glad my common sense was right about the throttle body injection.

[86Cutlass383SR]

Not a problem Kevin. If you already have a throttle body setup from a donor car then it may be worth considering. If you have to buy everything for the swap, myself, I'd just stay carbed. The multi-port is DEFINATELY worth swapping to!

[Later-A-body]

I am running the Retrotek Speed multiport EFI on my 560 hp 464 inch Pontiac. I am very happy with the system. It is very user friendly, self learning and can be tuned with a laptop. I was new to EFI last year when I did the conversion, but have learned quite a lot so far. I wanted a system that could be completely tuned to my set up. Some systems available are not as tuneable as the Retrotek system, and others that can, are far more expensive. I run a large roller cam, and have been able to see much better driveability and increase in mileage. A friend of mine has the Retrotek Speed TBI set up on his 455 Pontiac, and his car runs fantastic. His system is identical to mine as far as the ECU and tuning, but is a TBI system. The previous responder seemed to put down the TBI system, but from my perspective seeing success on my friends set up shows that the TBI system is also very good. As for the TBI being an "intelligent carburetor"....I would say that the carburetor would need to be a genius due to the fact that it does not have an ECU controlling the AFR to whatever you want it to be. I have my AFR tuned to 14.6 when cruising, and it progressively drops to 12.5 at WOT. I also have full timing control with the laptop, and that allows big gains in power and driveability. If your going to EFI, dont get a system that wont control timing. At that point you may as well just keep the carb. Take full advantage of the technology available.

[86Cutlass383SR]

In comparing carbs vs TBI vs Multi Port there are certain things to look at. Not being an engineer, I'll see if I can clearify.

All systems deliver both air and fuel to the chamber to burn. Lets see how they differ.

Carbs - Carbs have worked great for several decades. Air in, mixed with gas, and then thru the intake runners to the awaiting combustion chambers. At lower engine speeds and thru the curves in the intake tract, fuel has a problem staying suspended in the airflow, aka fuel drop-out. At higher rpms, the fuel also has problems in the fact that it's traveling so fast, it can't make those same turns as fast as the air can. So, the fuel ends up hitting and collecting on the walls of the intake.

TBI - Air still flows into the throttle body and the TBI uses a computer to tell the injectors how much fuel to add or subtract. Much easier to keep an optimized a/f ratio at all rpm ranges where the carb has to run rich at some points and slightly lean at others. Yeah it can be fine tuned better in the fact you can have multiple ranges for the ecm to read which means it can run optimized at many differant loading conditions, unlike a carb which has to be tuned to give the best overall conditions. But, just like a carb, it still runs an air/fuel mixture thru the same intake tract. Same problems with fuel drop-out and such. Also, just like a carb, most runners aren't exactly the same shape and distance, one cylinder might run slightly leaner/richer than the other cylinders.

MPFI - multi port fuel injection. Air is introduced thru the throttle body which meters only the air. The air, being lighter than an air/fuel mixture, can flow better thru the same runners. No fuel drop-out problems because you haven't introduced the fuel yet. You have an injector at each cylinder inlet to deliver the fuel to the faster flowing airflow. Since the distance is now shorter from the fuel delivery to the chamber and the air is flowing faster, the fuel is atomized better for a better burn in the chamber. You also have a more precise a/f ratio introduced at each cylinder. It's still not perfect, but closer. Depending on the system you use, some even let you adjust the injectors at each cylinder for an even closer ratio.

It's not that I'm "down" on TBI, the MPFI is just so much better. The TBI still uses basically the same type of sensors as MPI but it basically all controls that "smart carb".

If TBI is as good as the MPI, would all the factories have spent the $$$$ for the MPI setup? Is TBI better than a carb? If tuned properly. Is a finely tuned carb better than a poorly tuned TBI? Yes it is. Since the MPI uses the same basic setup as a TBI, doesn't it make sense to get the more advanced MPI?

I guess I've explained it about as good as I can. I'm no efi expert but I have researched it for several years. The benefits have been proven many times over.

[Later-A-body]

It is safe to say that the OEM's fazed out TBI in favor of MPFI for a few reasons. The most important one being for emission purposes. It is better able to be tuned for tighter emission standards. Same situation we are now seeing with direct injection. More power, lower emissions. I agree MPFI is a better system than TBI if power is going over say 500. Whatever system you choose, ask a lot of questions about how much control you have over the tuneability. Dont waste time with anything that does not offer timing control.

[windsor]

MPFI is not 'so much better'. It's used by OEM manufacturers to get the highest possible MPG and idle characteristics out of OEM type applications, and emissions standards had much to do with this. Carbs and 'good' TB type systems will generally make more power due to their ability to atomize fuel better (among other reason), and that's pretty well known in the engine builder world.

Try as you may, timing a fuel injector in an MPFI set up to open at exactly the time its respective intake valve will open is nearly impossible.

That all being said, if you want to be able to to have better street manners I say go with efi, whichever system it may be. I'd love to try the TBI setups from Retrotek or EZ-EFI and I think they'd be perfect for your combo. I also prefer how much wiring they do away with for a cleaner looking install. Regrettably, they won't support the HP levels I'll be going with (over 700).

*For the record, I will be using the TBI Wilson V-Force throttle body with 8 injectors provisions in the TB itself and an appropriate ECU that can control spark and fuel. Thinking about the Retrotek Stage 4 EMS*

[61ragtop]

Great info guys thanks.

[64duece]

Here's another option you can look through the material for an in-depth overview of the features.

http://www.holley.com/Index.asp?division=Holleyefi

The Avenger systems (both TBI and MPFI) are designed with a beginner in mind and include a handheld programmer where the customer answers some basic questions. The system selects the best pre-canned map based on the answers to load and self tune from there. Can be tuned with laptop s/w aswell.

The HP systems (both TBI and MPFI) are designed with a more advanced user in mind and work with laptop s/w for the end user to have more control over tuning. This system self tunes from a user selected map.

[GregWeld]

If the EZ EFI I have and plan to switch to works as advertised -- I'm going to have a Accel Gen 7 and harness with wide band O2 -- and a intake with Kinsler throttle body etc on it.... with all the sensors etc if you're interested. It will be a month or so.