LS3 swap Holley EFI vs OEM computer

[CamaroJesse]

I just picked up a low mileage LS3 from a 2010 Camaro. Only mods i will be doing to the motor is a bigger cam and all the bolt ons. Trans will be a Magnum T56. I have used the Holley efi systems in the past and they are really great and easy to use. However when I went to go buy the Holley Terminator for a Drive by wire LS3 its almost $4000. Thats more then double what I paid for the Holley system on Gen 1 Ls motors. It looks like Wiringspecialties.com can get me running under $1500. I would still need a dyno tune ($550) but its still cheaper then the Holley. I am looking for opinions on what people think about this. I am also open to other efi systems that may be out there as well.

thanks!

[joeko23]

Psi has an engine control kit for $1399, they use an OEM PCM and pedal. You will still need a tune.
https://www.psiconversion.com/products/engine-controller-kits/geniv/T56/

If you want to save yourself money. Buy a standalone harness from PSI it’s $569. You’ll still need a tune obviously and you’ll need to buy a pedal and a PCM from a junkyard or eBay. OEM PCM is like $100 and pedal is $50-60.
https://www.psiconversion.com/products/standalone-wiring-harnesses/ls-58x/ls-t56-th350-700r4/DBW/HAR-1037.html

[andrewb70]

I just picked up a low mileage LS3 from a 2010 Camaro. Only mods i will be doing to the motor is a bigger cam and all the bolt ons. Trans will be a Magnum T56. I have used the Holley efi systems in the past and they are really great and easy to use. However when I went to go buy the Holley Terminator for a Drive by wire LS3 its almost $4000. Thats more then double what I paid for the Holley system on Gen 1 Ls motors. It looks like Wiringspecialties.com can get me running under $1500. I would still need a dyno tune ($550) but its still cheaper then the Holley. I am looking for opinions on what people think about this. I am also open to other efi systems that may be out there as well.

thanks!

Since I do Holley EFI remote tuning, I have a biased opinion. I would do the Terminator X Max:

https://www.holley.com/products/fuel_systems/fuel_injection/terminator_x/terminator_x_and_x_max_ls_kits/terminator_x_max_ls_kits/parts/550-931

Let me know if I can help with the tuning or answer any questions.

Andrew

[CSG]

Andrew,

Would you mind sharing why you prefer the Holley over the modified OEM setup? My issue with the Holley is the lack of self diagnostic ability. Other than that I don’t know much and will soon be looking at the same scenario as OP.

[andrewb70]

Andrew,

Would you mind sharing why you prefer the Holley over the modified OEM setup? My issue with the Holley is the lack of self diagnostic ability. Other than that I don’t know much and will soon be looking at the same scenario as OP.

The Holley has an incredible data stream that once you learn how to use, offers a lot more diagnostics than the OEM ever could. It also has a built in wideband O2 sensor that allows for closed loop operation under wide open throttle. The other big benefit is being able to tune it when parts are changed. The speed density tuning is a lot better when bigger than stock cams are used.

Andrew

[ORBandit]

Your system isn't wild, I'd use OEM. Having tuned with HPT for 15 yrs, and Holley on my 79TA for several now, the lack of diagnostic codes (misfires) is infuriating. I will get the Holley guys saying there are "ways" and "methods", which there are, but they aren't anywhere near as good as OEM. If Holley did one thing moving forward, find a way of monitoring misfires without reading plugs, checking wire resistance, etc.

[ryeguy2006a]

My opinion is that it really depends on what your plans are for the car. If you plan to get the car up and running with the bigger cam and never do anything else to the car, it would be a good option to run an OEM ECU. However, if you plan to maybe do a cam and headers this year, do ported heads next year, and then maybe a supercharger the following year definitely go with the Holley ECU. I've run both, and I will say that the OEM computer is nice for the diagnostics, but really once it was tuned I never had to really check it. And like Andrew said, if you had say a bad coil, you'll know it by the readings being off once you get used to seeing the data from the engine.

What I really liked about using the Holley ECU is that it is so much more adaptable and user friendly than using HP tuners. The community support that you get from the Holley platform is really amazing. Guys are really willing to help you get up and going. The canned tunes are great for getting the car up and running quickly, which is awesome to do yourself. Prime example was when I got my Camaro up and running with the LS1/6 speed. I used the Terminator X platform and it fired right up using a canned tune. I was able to tweak it and it ran fantastic. Then over the winter I decided that I wanted to swap to a supercharged 6.2. Just changed a wiring harness and some settings to go from gen3 to a gen4 motor on the tune and it was up and running really well again. There isn't any stock ECU that will allow you to do that with the same ECU. Additionally, you can do just about anything you want with the inputs and outputs in the Holley ECU. You can literally use them as a BCM if you wanted to.

[CamaroJesse]

A lot of good info in here i appreciate it! One other system Im looking into is Haltech Elite 2500. I really like the look of the digital dash they offer as well.

[slazisme]

Back in 2017 before the Holley Terminator stuff was available to the market I started collecting parts for my eventual LS swap that included Fitech ultimate LS ECU & harness standalone kit- speed density. I thought for 700.00 bucks it seemed rather inexpensive when just harnesses were going for 5-600.00 plus the handheld allowed me to tune things without me paying for a re-flash of the GM stuff.
I put it in last year and have been pleasantly surprised to date. Other than having an issue with the number 1 cylinder not firing fully because of a bad coil harness and the drivers cylinder head not being grounded it runs great! The dual wideband's allowed me to diagnose the problem coming from the drivers side bank with the imbalance
My tuner buddy who's good with FAST and Holley stuff came over one afternoon and helped fine tune things on his laptop while I was driving the car.
Here's a example of the fuel log that has about 30 headings, ECU has 4 loaded cam profile tunes based on vacuum load +-15Hg.
I posted this not to dissuade you on your selection but to show some other systems that are out there.
203103
203104

[Lonnies Performance]

After working with both aftermarket systems & the factory types, I can give an unbiased opinion.

The factory ECM has features you cannot get with the aftermarket, but you need to learn how to use it to your advantage.
The factory setup is equipped to account for numerous environmental conditions, emissions etc., plus drivability variables not in aftermarket systems.
It seems you can do nearly anything, but it is not self-explanatory or user friendly.
Your needs may also exceed the preprogrammed limits with certain high HP engine builds where the rpm, airflow or injector sizes exceed preprogrammed range limits.

You also have to buy the tuning software & VIN license for the car & possibly another for the trans if applicable.
If you are paying for tuning or at minimum the base tune, it adds up pretty fast.

If you are familiar with tuning & are willing to learn there is nothing wrong with OE setups except for 1 thing...
Their biggest drawback is the lack of real time modifications... you pull over, reflash & try again.
This is more time consuming than making a change while driving & seeing the immediate result.

The aftermarket is great when you have drivability issues such as a hesitation or a flat spot where you immediately bump a degree of timing & see the result.
Also, the self-learning feature is unbeatable when starting with a new combination. You can be ready to drive in a matter of minutes.

My only reason to use the OE type computer is if retaining the factory functionality of the vehicle. ie. gauges, cruise control, ABS etc.
On older cars, mid 90's or older, or when the engine brand does not match the car, this is not a consideration, aftermarket is the way to go.

I just went through this with my S10.
I reprogrammed the factory computer to run my slightly built LS3. It retained all the creature comforts & after a lot of tweaking, it drove like a factory vehicle.
I bet I flashed it 50 separate times.

The next iteration with adding a supercharger changed things drastically.
I added 1000cc injectors, which require additional computer tweaking (exceeded factory limits) to allow the idle pulse width low enough for a lean idle.
the next item was the limits of the MAF were exceeded necessitating the switch to speed density.
Now I want to use flex fuel & cannot do it due to ECM limitations.

Another advantage of the aftermarket is the ability to cross the late model engine with a drive by cable throttle for easy adaptability to older cars.
This is what I'm going to do with the built LS9 swap in my 91 Firebird as I despise fly by wire throttles.
It will definitely have a Holley system.

[andrewb70]

I personally always recommend DBW throttle with anyone that is installing Holley EFI. People have bad experience with OEM DBW because the stock tunes tend to have all kinds of limiters on the throttle movement. Holley EFI has no such features.

Andrew

[Lonnies Performance]

If your engine already comes with the DBW throttle body, it is a cost savings that I can accept.
Yes, the Holley is much better than stock, but I'm still jaded.

When you need to purchase a large diameter throttle body, the DBW ones get very expensive (almost 2x the cost) & some are known to be troublesome with forced induction.

Four things I prefer to remain mechanical... my steering, brakes, transmission operation (I don't want a knob & electronics preventing me from selecting park, neutral or reverse) & throttle control.

Make that 5... I was really annoyed with a new Challenger when I could not shut the ignition off with the car in neutral when it was on my rack.

[andrewb70]

Very few people actually need anything bigger than a stock 90mm DBW throttle body. On a 750hp engine going to a bigger throttle body adds about 10hp at the peak. If that throttle body is cable driven, the gain comes at the experience of low speed drivability, which can be tuned for if it is DBW. This is especially true with manual transmission cars and to some extent with automatics.

I recently tuned a very nice Camaro with a Don Hardy 427 with a FAST intake and a Nick Williams 102mm DBW throttle body. I had to slow the opening rate way down to prevent the car from jumping during transient conditions. If it had a cable TB, it would be super annoying to drive.

Andrew

[scottymonte]

This is a great thread. I am struggling trying to decide between OEM, Holley or Fitech for my Ls1/t56 (out of 04 gto) into my 76 Monte Carlo. Keep the info coming!

[andrewb70]

One of my local customer swapped out his Fitech for a TerminatorX Max and was thrilled.

Andrew

[Jolley_Man]

I currently have one vehicle running the GM computer and another with a Termi X Max, both DBW and prefer the Holley. The Holley seems easier to tune and it seems to be harder to diagnose issues with the GM system when it goes into REP due to the DBW. I battled this issue for a while, and it ended up being a loose ground on the back of the cylinder head that was causing the issue.

[streetk14]

I haven’t used the Terminator X, but had some not so great experiences with Holley EFI. I’ve seen others with higher end systems like the Dominator have similar issues. Tune files mysteriously disappearing from the ECU is one in particular. My Sniper system was plagued with EMI/RFI interference issues, but it’s probably not fair comparing that to the Terminator X.

My argument for going OEM is that they are incredibly reliable. There’s also much more in depth tuning possible, which could be good or bad depending on your skills or your tuner’s skills. I also prefer OEM type diagnostics, but I guess that’s a preference. I like the integrated wideband and self learning fuel map function with Holley, but it wasn’t enough for me to take the plunge this time.

[streetk14]

I’ll also add that dealing with Holley’s tech support really sucks. You’re either stuck on the phone for 45 minutes waiting to talk to someone, or you fill out one of those online forms and hope someone responds. That part was pretty frustrating.