Newbie to FI - Fast XFI or Something Else....

[The WidowMaker]

well ive done some searching, and ive developed a few questions that i cant find answers for.

first, the plan is to run an lsx block, l92 or ls7 heads and shoot for 454ci and 600hp+ with a decent size cam. thats about as far as i have gotten. nothing has been purchased, so im looking for a complete system (coils, rails, ecu, etc...). like i said i need everything.

before today, i didnt know anything about efi setups. everything ive run in the past has had a carb. so heres what i think i know.

the efi systems use an ecu to "pick" the correct duty cycle for the injectors along with the correct timing for the dis and coils. this is done by receiving info from the many sensors and inputing them into a table. the value that falls within the box that correlates to the sensors inputs is then transmitted to the ignition and injectors.

the aftermarket systems mostly use a closed loop system that employs an o2 sensor to make sure its doing its job correctly (does an open loop have an o2 sensor?). there are also two different types of o2 sensors; the narrow band and the wide band. the narrow tells you if your rich or lean, but it doesnt know by how much. a wide band lets you know the a/f/r, so you can tune it.

there are also two different methods to calculating the air input. the first is the maf, but this isnt used in the aftermarket. the second is the map which uses the speed density method. this is the preferred method in the aftermarket.

now for some questions. ive been looking at the fast system. from what i gather, i need their total install kit which includes the ecu, the xim, the harnesses and the sensors. but, since im starting from scratch, what is the difference btwn the ls1 and ls2 stuff? ive found about a $700 difference btwn the two. what makes the ls2 different, besides the 58x? is there something included in one that is not in the other? cant i just use the 24x crank and the ls1 coils and call it good?

besides the stuff listed above, plus the coils, fuel sys, fuel rails and injectors, what else is needed to make the swap and get it running?

also, with a sophisticated computer, why cant this thing tune itself? also, what makes one motor need a different a/f/r curve than another? now i know one engine may need more fuel, but that shouldnt change its needed a/f/r. i guess i just cant understand how if my motor was as efficent as say an ls7, both were at the same fluid temp, with the same heads, at the same rpm, at the same altitude, with the same ambient air temp, with the same humidity etc........ that they wouldnt be reeeeeeeaaaaaaaly close to needing the same afr.

one more thing, how does the tuning work? i know guys drive them with a labtop in the passenger seat, but what are you inputing? if you do a wot run and it tells you that at 6100 rpm you were at 13.2:1, do you then just change that figure to where you want it? does that value now just fulfill one category out of a possible million (meaning do you have to do the same thing at 6200rpm or even do it again at 6100 rpm when the air temp is a little cooler)?

way too many questions, but i appreciate the help.....

thanks in advance,
Tim

[EFI69Cam]

There are so many people who are familiar with the stock GM ECU and have gotten excellent power out of it that there really is no reason to buy another system for an LS engine. In fact in the latest (2008) GMPP catalog there is a ECM and harness setup for LSX engines that costs less than $1000 and comes with mass air sensor and complete harness. My advice: Buy one of those then talk to one of the many tuners to get a calibration.

[amx2334]

I recommend downloading and reading the holley commander 950 manual.Even if you don't use their system it will help explain alot of how the ecm works.

[The WidowMaker]

thanks guys. ill get that manual and start reading.

as far as the gm stuff, the only reason id want to stay away is the lack of me being able to tune it. dont you need to have someone burn a program for them? can you use a labtop hooked up to it?

is anyone close to having a self learning program? are we still 5 years out, or even more????

what are the constants in efi tuning of afr btwn engines? meaning, if engine "x" wants 13.1 and engine "y" wants 13.5:1 at the same set of parameters, which inputs can change to keep the afr proportionally the same btwn engines. its hard to type what i mean, but if both those engines were driving at 0ft elevation and then drove at 10,000ft above sea level, would the change in afr be proportional btwn the two motors?

i guess ill start reading now.... thanks again, Tim
Tim

[laguna4efi]

Well, let me say first that I work for FAST so I'm somewhat biased. I will give you my honest opinion though. The Holley manual will be a good read for you. We also produced and sell a 'how to install and tune XFI' dvd. It will be helpful not only for XFI, but EFI in general. The reason the LS2 kit is more than our LS1 kit is the LS2 kit includes a throttle body since the factory one on the LS2 is a fly-by-wire. Our throttle body is a mechanical cable drive. The XFI won't do fly-by-wire, as most aftermarket ecu's won't. Other than that, read, watch, and have fun with it.
PS - as for your question on afr's many things can affect it and yes they certainly can and will be different from engine to engine. Things like camshaft, combustion chamber shape and volume, spark plug location, bore, stroke, timing, etc. They all can affect afr dramatically. As with anything, there are many ways to get to the same end result.

[DeltaT]

I also highly recommend Jeff Hartman's excellent book "Tuning and Modifying Engine Management Systems". He takes you through it all, including an excellent 'EFI-101' chapter on bringing up a new tune from scratch, including detailed differences and tips for FI setups. I used his book along with my Holley 950 Commander Pro (with wideband) to bring my Vortech-blown 383 to 632rwhp safely and with no professional help.

Jim

[GetMore]

FWIW, a MAF makes a system much closer to self tuning, where a speed density system requires complete maps, but is cheaper and doesn't restrict the airflow.
Part of tuning the engine is getting the timing maps correct. That is something that the sensors can't give enough info on. (I think it may be possible to make a computer and program that can self tune an engine, but that will be very expensive and require more sensors.)

There are many variables that make any engine different from any other one. Intake runner length, cam timing, header design, even the exhaust after the headers can cause changes.

One of the reasons a system needs to be tuned for the engine it's on, even if you use an O2 sensor is because they can only modify the programmed fuel map so far on their own. What you usually want to do is see how far off the program is and then make the adjustments manually, so you are close to perfect. Then the O2 can be used to fine tune for atmospheric changes.

I'm just getting started in learning about all this myself, so I'm no expert. There's definitely a lot to learn to really know what you're doing, but you can get by without a complete understanding.

One other thing: if you know anyone that does programming you will probably want to go with the system they are familiar with, just in case you need help from them. Different systems use different terminology and the interface will be different. If someone is not familiar with the system they will have a difficult time working through it. It's kind of like the Mac/PC thing. Each has got advantages and disadvantages, one person will tell you Macs are the best, and another will tell you they are worthless.

[MastMotorsports]

This sounds like what you are looking for:

http://www.mastmotorsports.com/turnkeycrategas_main_flash.php

This LSX 454 HO made just over 620HP/615TQ on our dyno and comes already tuned.(Click on "dyno" to see the dyno data) There is a Calibration Software package that is available as an option, but is really not required unless you plan on changing somthing on the engine. We also have stand alone ECM/wiring harness packages. This crate engine comes with starter, water pump, and air filter as well. Click on "components" to see a parts list. Once you get the engine in the vehicle, it takes about 5 wires under the dash to get it running. Hope this helps!!!

Shaun
www.mastmotorsports.com (http://www.mastmotorsports.com)

[Turbo67camaro]

These people claim to have a kit that is self-tuning.

http://www.mass-floefi.com

It looks interesting to me. I'm considering buying it, but I'm by no means educated enough on this stuff to advise you in any way.

If it ends up as a system that has slightly less HP, but it runs on average better in a wide range of driving conditions (elevation, etc.), I'm all for it. My time is valuable, and I prefer to spend my time in other ways than doing dozens of tunes like some people do.

But, I'm undecided and may go with a must-tune system and pay a dyno-tuner to dial it in for me.

[camcojb]

These people claim to have a kit that is self-tuning.

http://www.mass-floefi.com

It looks interesting to me. I'm considering buying it, but I'm by no means educated enough on this stuff to advise you in any way.

If it ends up as a system that has slightly less HP, but it runs on average better in a wide range of driving conditions (elevation, etc.), I'm all for it. My time is valuable, and I prefer to spend my time in other ways than doing dozens of tunes like some people do.

But, I'm undecided and may go with a must-tune system and pay a dyno-tuner to dial it in for me.

do not run that system if you're username is an indication of what you're putting it on. I don't like it because it is not end-user programmable; you're giving up the biggest advantage to most factory and aftermarket efi, by not being able to tune it yourself.

It has a maf sensor so can compensate for different mods to a point. Beyond that, cam swaps and hardware changes will likely have you mailing the computer back and forth for changes to tweak the tune; if it isn't right, you'll send it back again.

Been there, done that, never do that again! :pat: I've run FAST, Accel Gen VII, BigStuff 3, factory ford and GM (gas and diesel) and the great thing about all of those is I could tune and tweak it myself, without wasting time and money sending the computer or tune back and forth to some tuner who does not even have my car/truck in front of him.

Jody

[Ollie8974]

Another good forum for EFI is.

www.thirdgen.org

[Turbo67camaro]

Camcojb -

Thanks for the help. I'll look harder at the speed density systems.

I'll call a highly recommended professional dyno tuner in my area tomorrow to get some advice.

Shooting thyself in the foot is probably quite easy in this area.

BTW, your projects are awesome !

[laguna4efi]

All the systems Camcojb has mentioned are good systems. I'm a little biased since I've been with FAST for quite a while but I'm not going to put the big sell on you. A very good tuner about an hour or so from you is Brian Macey at Horsepower Connection in Lacey, WA and he's good with many of the systems mentioned.

www.horsepowerconnection.com (http://www.horsepowerconnection.com)

[camcojb]

Camcojb -

Thanks for the help. I'll look harder at the speed density systems.

I'll call a highly recommended professional dyno tuner in my area tomorrow to get some advice.

Shooting thyself in the foot is probably quite easy in this area.

BTW, your projects are awesome !

thank you. Down to just the Chevelle as far as muscle car stuff, thrashing to make Power Tour.

Jody

[BB69]

People keep talking about self tuning computers, but you have to realize what they are doing. Several systems offer self tuning features, but they are simply making changes to the fuel map in an effort to reduce the error between a requested AFR and a measured AFR. What does that mean? You still need to know what you need the AFR to be throughout the operating range. These systems monitor the O2 output and compare it to the AFR the computer was shooting for. Over a period of time the computer learns how much correction was needed to bring the requested and measured AFR's together. It then makes an adjustment to the fuel map. Many of the OEM computers put this in a short-term correction. That is why new cars may drive differently after you disconnect the battery.

The point to all this is that you still need to input required AFR's at different operating points. (Most likely a 12x12 or 16x16 table)

You also need to understand how a MAF meter works. For a given airflow across the sensor, they produce a voltage or frequency. However, they have an upper limit. If you take a MAF meter from a stock engine, and you ram a bunch more air through it, you may very well "peg" the meter. Basically, the meter is putting out it's max output and you are continuing to put more air through it. The computer then has no way to tell how much air you have, and the engine goes lean. It's a great way to blow holes in a piston.

Another point about O2 sensors. OEM ECU's can use a narrowband to pretty much figure out how rich or lean the engine is. It does this by changing the amount of fuel it adds/subtracts for the same situation. For instance, if the computer says fire the injector for 2.5ms, and O2 says it's lean, the computer will add let's say 0.1ms. The next time, when the injector fires for 2.6ms, and the O2 says it's still lean, the computer adds another 0.1ms. The computer figures out how much of a change it needs to make the O2 switch to rich. By constantly doing this, the computer figures out how rich or lean the engine was in that situation.

As for how to tune the engine, the best method is to use a load bearing dyno. Most fuel tables are a combination of engine speed and load. The dyno can hold the engine speed constant, and then you can vary the load. You work across the table, tuning each load point for a given engine speed. By comparing the requested AFR and the measured AFR, you can calculate how much to change the required fuel. This is normally done by changing the volumetric efficiency on a speed density system, or the MAF transfer on a MAF system.

As you can tell, it will extremely hard for you to tune the engine, if you don't understand how your specific system works. Whatever system you go with, you need to read up and find out how it calculates fuel and how it makes corrections.

Good luck.
Ken