I would question the engineering if there were no opportunities for improvement on a new product after 8 years of a production run with thousands of operating units out there. Obviously there is a marketing side to improving a product, but that is a pretty normal design cycle. Look, I understand what you are saying, but going back to a carburetor isn't going to be an option for most people that make the switch. I would advise people to NOT make the switch to EFI on a older vehicle if you are going to run back to the carburetor when you have to work through some issues. Carbs, due to their relative simplicity and almost a century worth of refinements are more reliable than an aftermarket EFI system (not OEM EFI systems though). No one is going to argue that. A slide rule is far more reliable than my personal computer. However, I am not going to get rid of my computer because it has to be upgraded every so many years or when hard drive inevitably fails... The capability of my computer keeps me from going back... Not a great analogy, I realize, but that is effectively what you are advising. Like I mentioned before, my car was carbureted for over 40 years of its existence, 25 years of my ownership.

The purpose of this thread is to help folks realize that you can't go out and slap an EFI unit on their cars - and then treat it like a carburetor. If you aren't going to engage the technology side and the advantages of the EFI, then don't make the switch. It's not worth it. However, if you are going to engage the technology, tweak things, improve running conditions, startup efficiency, timing controls, cold start fueling, acceleration enrichment, use data logs, then EFI is vastly superior to a carburetor. I personally enjoy that level of control, but it didn't come without a steep learning curve. Now, instead of taking my carburetor off, opening up the metering blocks, switching out the jets to change my fueling, I change a few cells in some software, hit save, and the change is made. Same with timing controls. I don't have to open up my distributor, alter weights and springs, then test it by trial and error. Now it's - click, click, click, done...

KT

 

I always keep a spare 02 sensor in my car just for that reason .

 

It has been very interesting following experiences and comments relating to not just what could be easily as first been dismissed as being a 'simple' injection system (Sniper set-up). Even though arguably not as comprehensive as perhaps Edelbrocks ProFlo, whilst considered maybe a 'plug 'n' play' inject system the Sniper system is certainly far more than just that. Myself, being UK based it has made me realise how vitally important that manufacturer and supplier support is - especially if you are experiencing difficulties. Going back a few years ago I had dreams of going with a 'stack' injection system using an Enderle set-up with a proprietory Holley or other software and hardware set-up. Apart from the extreme costs of all the equipment needed, plus the additional set-up, dyno and mapping time (and cost) the minimal performance/economy benefits and perhaps more importantly the reliance of a third party specialist very time the set-up goes out of tune or I make mechanical changes to the engine set-up that requires further 'mapping' time. After making a few visits to the Edelbrocks ProFlo forum and seeing some of the simple issues that installers were experiencing and now reading about the technicalities of even the Sniper system it has made me realise that for my car my minimal use and mileage means it's just not worth the expense and potential issues I may experience. Old school nuts, bolts, screwdrivers and a good eye/ear don't seem so bad after all. Appreciate all the individual inputs so far.

 

So do I. However, the only sensor that failed me was the one that came with the Sniper. I bought two from another source, and the first one is still in service after a couple of years and several thousand miles.

 

This is a "Tour de Force" assemblage of your experience and reference information that will help people for years to come. Well done. Thanks, Atlanta

 

Thanks for the comment. The goal was to help others. I spent a lot of time gathering the information, and more time compiling it. If I can save someone some time, it would be worth it.

 

I added some more detail to the idle tuning notes in post #1. Included are two data logs that compare a not so smooth transition to idle vs a smoother transition to idle. Values aren't super important because every engine is slightly different. However, most engines fall into a RANGE of values that are common.

Not so smooth transition to idle:



Smoother transition to idle:

 

I just added a "chapter 15" to post #1.
SPARE PARTS and their equivalent part number references (for non Holley parts).

 

Fantastic treatise on the Sniper.

Simple question. What sort of gas mileage can be had with a Sniper vs. a carburetor? Does it have features like deceleration fuel-cut?

Assume a nominal 350, nothing special, NA.

 

Yeah, I've installed several, and they ALL had issues. They currently work.....but not quite as Holley intended. Holley is a great company and they do what they can to help but I wouldn't recommend the sniper. Either it's going to drive a DIY person nuts and waste lots of time/money with plenty of disappointment, or you'll pay a professional to install it and by the time it's somewhat straightened out you could have gone with the much better port injection versions.
I big trick to the Sniper system is to tune everything in open loop, and possibly keep it in open loop, but if you want to make the feedback feature operational, only allow it to make changes in a small window Like +/- 5% that way if something like the ultra common oxygen sensor issue rears it's ugly head, it can only sway things so far. Also the moment fuel pressure issues arise, running an external regulator can alleviate that.

 

I'll answer the fuel decel cut-off question first: To my knowledge - no.

Gas mileage wise, it depends on the tune. If you tell the Sniper to run a rich AFR in areas of the fuel curve where your engine doesn't need extra fuel, it'll be less efficient. If you tune your Sniper's target AFR ration table "lean" you'll get better gas mileage. Where any EFI system will be more gas friendly is it will adjust to conditions to make a desired AFR, where a carburetor will not. So those of us who try to gain gas mileage with a Sniper, generally you customize the AFR table and bias it lean-ish...

There are some who have done some basic mileage data gathering, but I don't have anything at this time. Perhaps someone who has a mild 350 build and a TB EFI unit can add some information here.

 

I tried to address some of the statements above in the text in RED.
Most of the "issues" I've experienced or heard of:

1. Exhaust or vacuum leaks (including PCV issues)
2. O2 sensor failure - which will cause any EFI system to have issues.
3. EMI issues
4. CTS failures
5. IAC controller failure
6. TPS failure
7. Throttle bladed issue (rare)
8. ECU failure (rare for the number of units out there - but it does happen)
9. Old car issue outside of the Sniper platform

Good discussion. There are some good concerns mentioned above. The common theme I believe is O2 sensors wreaking havoc on the EFI units ability to deliver the correct fuel mixture. If it tells you something, the only O2 sensor that failed me - was the one that came with the unit brand new. I did two things to correct this: I replaced the O2 sensor with a non Holley supplied Bosch 4.9 LSU equivalent sensor, AND installed a HBX1 O2 sensor heat sink bung in the O2 sensor port. I have had NO further issues in 4.5 years and thousands of miles of driving since then. I even have the O2 sensor installed at a negative angle to clear my frame with side pipes!

There seems to be an uncommonly high failure rate in Sniper O2 sensors, especially in the beginning of installation and tuning process. I don't have any data to support this, but I hear about it a lot. I also believe that a lot of the wizard tunes are inherently rich when starting a new tune. One way to kill an O2 sensor faster is with consistent over fueling. Just a theory, no facts or data...

I would add that many of the peripheral items on / in the sniper - such as the fuel regulator, IAC unit, CTS, O2 sensor, TPS, etc... are not manufactured by Holley. Holley outsources them, and I know they don't put "top of the line" components on the Sniper units. I generally don't buy these parts from Holley - since they generally get them from the same sources you can - without the markup.

I think I've beaten the horse dead many times over, but if you are going to install ANY EFI unit and tune out the closed loop feature, keep the carburetor. You don't need to spend thousands of dollars to turn your EFI system back into a carburetor.

KT

 

In the cases I dealt with (it's been a few years so no fresh in memory) I believe the O2 sensor issues were not the actual sensor but rather the circuity on the Sniper unit end.
Just as an aside, I certainly don't want to tie this specifically to Holley as once again....this was years ago but I was told by my tuner that he had a friend in the know......and one of the EFI manufacturers were having things produced in China and were spec'd with certain hardware.......and the Chinese manufacturer was fraudulently installing knock-off versions of the parts. I don't know if it was micro chip related or something like that. Pretty crazy, but simultaneously not surprising.

 

I agree that Holley generally makes good products. The Sniper is a relatively budget friendly entry to mid level EFI option. If the ECU has issues, that's all on Holley. The peripheral Sniper components are on Holley as well, but if you do replace them your unit will probably be more reliable. I've pretty much replaced all of the peripheral components over time on my Sniper unit - IAC, TPS, CTS, O2 sensor, removed internal regulator, and injectors (upgraded). I've added a pulse dampener as well. So, it's not been all rosy on my end either. They aren't expensive parts to replace, but still. My Sniper unit throttle body and ECU is original - everything else has been replaced - and now it runs like a champ - once I got rid of most of the Holley peripherals!

This thread is here to talk about this stuff, so thanks for your input.

KT

 

Just wanted to say this is the best breakdown of tuning a Holley EFI system that I've seen. So much better laid out than many of those YouTube experts I've seen.

I hope your AFR section gets a bit built out as that's an area I don't have clarity in yet and seems to be an important table to nail down early.

 

The AFR table is very important, in fact probably the most important. The problem is, it can be subjective unless you have access to precise testing / quantitative data for your engine build. Most of us DIYs working in our garages, don't have reasonable access to dyno's for max power tuning. Idle areas can be tuned for best vacuum given a handful of conditions.

I can expand on the AFR table generation, in general terms and concepts. When I get a chance, I'll do that, and add some pictures and such.

KT

 

I'm working on a couple of Sniper related things:

1. A unique troubleshooting problem / symptoms that I had never before seen / read about... (more to come on this)
2. Experimenting with different injectors and pressures on the Sniper platform.

When I get some time, I'll expand on item #1. I've just started delving into item #2. There's not a lot of information out there about folks playing with different pressures / injector ratings. I may start experimenting. Anyone out there run different injectors with 43 psi? I don't see why you couldn't run different combinations out there - as long as you enter your injector data and operating pressures correctly. That is also assuming you have a reasonable injector sized...

 

I just created a "Tuning Tips - AFR Table" section in post #1. It falls under number '4' or somewhere around there... So, basically I've updated that again - for those who have "copied and pasted" that document...

KT

 

Halfnium, no intention of mucking up the thread but I also wanted to offer sincere appreciation for this compendium. The amount of time and effort you've spent on this is truly praiseworthy. This is stellar work and I have no doubt that it has been helpful to many, to include me.

For reference, my Sniper EFI 550-871 system (Ver 1.0) has been rock solid. However, as you mentioned, the notion that something of this level of sophistication can truly be relegated to an unbox-weekend install-start-done is a tall order. It's not impossible, but it's highly improbable. While this system will easily rival the best possible carbureted+standalone ignition setup, it still requires dirt under the fingernails. The issues I experienced were electrical in nature, and were of my own doing/misunderstanding coupled with less-than-desirable information in the otherwise well-conceived documentation from Holley. Once I provided clean power to the unit, quite literally all of my "issues" were resolved.

I digess... thank you again for this information... It's definitely a keeper!

 

In the spirit of continuous learning, I've run across a couple of instances of Holley Injector mechanical failures. For example: the injector checks out electrically, but the pintle valve sticks either partially open or shut. There are some examples of the injectors electrically failing, and some examples of the injector drivers failing in the Sniper ECU. However, I wanted to focus on the injectors themselves.

An electrically failed injector is relatively easy to prove. Generally, it will be a 'dead' injector meaning it won't actuate electrically. You can prove this electrically or by looking down the Sniper throttle bores. It will be pretty obvious the "dry" bore is your problem injector. You can also check the resistance / impedance of the coil by measuring the resistance across the two pin terminals on the injector. Generally, a high impedance injector should be in the 9-15 ohm range, and Holley injectors are around 12 ohms or so. You can also use a 12 VDC source and actuate the injector by applying the ground and 12 VDC to the pins. You'll feel and hear the injector click.

A mechanical failure is harder to prove unless you have the right test equipment. It will also be more subtle to troubleshoot in the car. You'll know something is wrong, but the data logs and visuals may not be obvious enough to determine the injector failure. For example: if an injector fails partially open or intermittently open on the bank where the O2 sensor resides, the CLC may inexplicably start pulling fuel out of the idle area even if it's well tuned. One bank will be getting too much fuel, and the other bank will be lean (but unmeasured). The idle will be rougher, and the car might run, but it won't run healthy. The ECU will try and compensate and match your desired AFR with the read AFR, but it will be doing so with some measure of fuel it can't control in a mechanically faulty injector.

If the fault is on the non O2 sensor side, then you'll still have the poor running conditions - without the CLC doing as much or compensating less. Reason for mechanical failure probably can be attributed to small pieces of debris in the fuel system, poor injector quality or materials used, corrosion byproducts, etc...

Just some more observations...