[HWYSTR455]

https://www.holley.com/products/fuel...ts/550-511-3XX

Improved RFI/EMI resistance is a biggie, as well as now supporting up to 650hp NA.


.

[JLMounce]

A couple nice features in there. Added RFI protection and rear exit harness are great.

Sniper still needs a built in coil-driver for timing control where a CDI isn't necessary. If you've got a basic setup that isn't boosted or ringing a ton of compression, this can save people a good bit of money. I wonder if that's part of FiTech's original patents?

[HWYSTR455]

I think the less on the throttle body the better, less to fail/go bad. But it does have the 'Coil Minus' wire built in. All it needs is an RPM signal for no timing control.


.

[JLMounce]

I'm talking about using timing control with a distributor and coil only. Thinking about stock or lightly modified engines where the use of a CDI box isn't really necessary.

Yes the sniper family of products integrates well, but if you want timing control, you end up having to buy the distributor, coil and CDI box at fairly significant expense. If the ECU had a built in coil-driver, many hobbyists could save a bit of money on the CDI box.

[HWYSTR455]

Oh I get it now...

Coil driver can't be that much, and the CD boxes are under $250.


....uhg, maybe they went up....

.

[JLMounce]

I was looking at them for my uncle who wants a sniper q-jet on his 68 bird. adding timing control is an extra 800-1000 depending on what you get.

These things have gotten expensive unfortunately.

[HWYSTR455]

A good prepped qjet can easily be 600-800+, and a prepped 4150/4500 can be 2-3k+. Then of course you have to wait a year or two for them to be done.

You can catch items on sale, even find some items used in good condition. I'm sure Holley/Mr. Gasket has teams of market research people pricing items. It's probably right in there, and honestly, it's better than 6-8k for EFI back in the day. Or more.

There's something to be said for an off the shelf carb replacement efi setup that can be easy to install, setup, and run. It's definitely the easiest way I can think of to break into the efi game.

.

[RocktimusPryme]

You know what got me. EFiSYSTEMSPROs told me that the RFI was much more of an issue with front distributor engines.

I would have thought it would be the other way because people run their wiring along the firewall. Why would front distributors cause increased RFI issues?

Agree on the coil driver. Especially with the Terminator systems that have a remote ECU. I haven't done spark control with mine yet just because I haven't spent the extra $800 on a Hyperspark setup.

[JLMounce]

Originally Posted by RocktimusPryme

You know what got me. EFiSYSTEMSPROs told me that the RFI was much more of an issue with front distributor engines.

I would have thought it would be the other way because people run their wiring along the firewall. Why would front distributors cause increased RFI issues?

Agree on the coil driver. Especially with the Terminator systems that have a remote ECU. I haven't done spark control with mine yet just because I haven't spent the extra $800 on a Hyperspark setup.

The distributor is one of the noisiest parts of the electrical system. It and the spark plugs are the two places where energy moves through the atmosphere, instead of a conductor like wiring. That's why resistor plugs are a must with EFI. Even then you've got a lot of aluminum and iron that is acting as an insulator. When it comes to the distributor, all you've got is the thin plastic cap.

The coil is also a noisy part of the electrical system. Most front distributor engines also retain their coil at the front of the engine. In this configuration, the ECU is closer to both of these noisy components.

[HWYSTR455]

Someone should come up with a shrink sleeve for dizzy caps that are RFI/EMI blockers. Or a coating.

Only thing you can do about the coils move them as far away as possible.

I find it interesting that Holley now offers a 'power distribution module' that conditions the power to Sniper components. This technically goes against the golden rule of connecting everything to the battery. But here it is:

https://www.holley.com/products/fuel.../parts/554-200

Not sure how it 'conditions', looks like a simple buss bar setup to me.


.

[Formulajones]

The first version would support way over 650hp. All you needed was to buy the 8 injector unit. We've had the 4150 8 injector units on the dyno at well over 700hp.

And the stealths already had a rear exit harness so don't know why that would be new.

I don't see where it says improved emi rfi protection. Did I miss that part? Wonder what they did to improve that. I've never had an issue there but I know many that have.

Edit: I see now they've changed something with the ECU to make it more resistant. Hmmm

[HWYSTR455]

There are several versions of the Sniper, and they are rated at different HP levels. The ones that support more than 650hp are the larger injectors, and the top HP support ones have 8 injectors, standard ones have 4.

Now, with the Sniper 2, the base version supports 650hp. I believe original base Snipers, it was 600hp, but I may have been mistaken. I think it used to say 600-650hp, but I know once you get over 600hp, you do want to step up to the larger model. It's due to injector duty cycle, like you want the duty cycle to not be over say 85%.

See the table attached, they are named differently.


.

[HWYSTR455]

The one with 8 injectors is the 'Super Sniper 1250'.

.

[HWYSTR455]

The bores on the throttle bodies are bigger for the higher HP models too. I think the standard one is 900cfm, and the larger ones 1250cfm, and 1375cfm for the largest ones, but would have to check to be sure on exact cfms.


.

[Formulajones]

Yes the big limiting factor of the 4150 style bodies were the 4 100 lbs. injectors. If you pushed duty cycle and fuel pressure up a bit the math would squeeze out a bit more HP but I don't really like doing that. They were limited around 600hp because of that.

However I've found those 1st design Stealth throttle bodies to measure out pretty big compared to the 950HP carbs they replaced on our stuff. Everything about them was larger. The bore, the blades, and the fact that there are no boosters or squirters in the way inhibiting flow, told me they will flow much more than the 900 cfm they were rated at. They just needed more injected for more HP. So I just went for the 8 injector unit with enough fuel flow for well over 1000 hp.

Turns out my assumptions and measurements worked out pretty well because these units work excellent on 700+ hp NA combos and in fact, after dyno testing it showed improvements over the 950HP carb it replaced so they definitely weren't hurting in the CFM department. Best part is injector duty cycle on the last datalog I looked at was only in the 40% range so it's hardly working as far as fuel flow goes.

[Formulajones]

Just to add to what I posted, and Ive said this before a few years ago when we bought our first sniper stealths.

Holley won't tell you what I posted above. They put a HP cap on those throttle bodies and then try to upsell you the other throttle body that has 4 120 lbs injectors, which doesn't come in the stealth design by the way. That hints at the other as being fuel limited, not air flow limited so why not do an 8 injector. They offer it, but they don't push it for N/A combos that need more fuel flow.

Wasn't till I talked to Chris at EFI System Pro who set me straight and told me Holley tech was just wrong. I could still do a stealth version, just get the 8 injector piece and it'll work just fine. Turns out Chris was right. Been running 2 of them a few years now and have worked flawless.
It's more of a marketing thing.

[HWYSTR455]

So the Sniper has 800 cfm throttle bodies. (4x 100lbs injectors)

The Sniper 2 has 825cfm (4x 100lbs injectors, note the tapered bore inlets)

The Super Sniper 650 & 1250 have 825cfm. (The 650 has 4x 100lbs injectors, and the 1250 model has 8 100lbs injectors, tapered bores)

(Super Sniper and Xflow info - https://www.holley.com/blog/post/whi..._application_/ )

"There are several flavors of these units, so we enlisted the help of Holley Fuel Injection Systems Engineer Matt Lunsford to detail the differences. Together we break down where an enthusiast might want to switch from one to the other and explain the valuable features each of the different units offers to help you choose the right system for your application. Each of the Super Sniper units is based around an 825 cfm Holley EFI throttle body."

Sniper XFlow is 900cfm (4x 120lbs injectors)

The Sniper Stealth 4150 is 870cfm

The Sniper Stealth 4500 is 1440cfm

It's not easy to find that info, especially since some of the spec listings are conflicting, probably from cut & paste used for the description boxes.

My guess is to limit the number of throttle bodies produced, they combined the base Sniper and the Super Snipers to use the same throttle body.


.

[JLMounce]

If you need more flow, these throttle bodies also benefit from the same modifications you would make the most carburetors.

Most of the throttle bodies rated at 825cfm flow more like 830-840. Knife edging the butterfly’s, going to countersunk cross shaft hardware and adding a light radius to the throttle bore exit generally gets them closer to 900 cfm.

[Formulajones]

I'd like for them to explain how a sniper throttle body with larger bores than a 950hp carb, as well as having no boosters or squirters in the way, actually flows less than the carb.

In reality the 950hp carbs we used flowed 870 on the bench and everything about them is smaller along with obstructions in the air flow.

So I don't really buy into Holley literature telling people they only flow 825. Especially since we put one on a 571 making 724 HP with the HP carb and then re dyno'd it with the sniper and it was identical and even slightly better in spots.

I honestly think it's more of a marketing scheme to upsell other product. They also told me the 8 injector wouldn't work on an N/A engine trying to upsell the x flow. I found that to not be true further confirming my thoughts.

[HWYSTR455]

I'm sure someone along the way will finally flow them, but it kind of doesn't matter. It might be more of a concern on larger displacement/higher perfomance apps, but if that's the intent, you don't use a TBi anyway.

The Snipers are 'entry level' units, try to keep that in mind. We are lucky to have them out, they set a baseline affordable standard, which is a blessing for the market.



.