[grivera]

The base level Sniper has four 100 PPH injectors and advertised at 800 cfm/up to 650 hp. The XFlow has four 120 PPH injectors and advertised at 900 cfm/800+ hp. The XFlow costs $1392.

I currently have the entry level Sniper on my 461 which made 521 hp on an engine dyno using a 950 hp carb and 1.75" headers. It runs great with the base level Sniper but I am always looking for more. My tuner with a similar horse power engine said he gained 20 rear wheel horsepower by upgrading from regular Sniper to the XFlow 4 injector system. He attributed the horsepower gain to the additional cfm. Does it make sense to see a horsepower increase going to an XFlow on an engine of my horse power level?

I can sell the current Sniper to recoup more than half the cost of the upgrade and already have an external regulator as the XFlow requires one vs the base Sniper which has an internal. The XFlow also monitors fuel pressure and ability for two other inputs like oil or trans temperature.

[Scott65]

It would appear by looking at your signature, that you'd have much more to gain on the exhaust side. I have no direct experience with the Holley TBI stuff, but for that money, I'd be looking on into mpfi territory, or at least something that used the Terminator ecu for future growth.

[grivera]

I’ve been exploring 3” head pipes to x pipe and 3” mufflers. Didn’t see the 3” head pipes for the LB manifolds which I want to keep and need a 100% leak free connection at collector due to O2 sensor. The LB manifolds have 2.5” collectors.

[Formulajones]

I don't see the gains myself just switching throttle bodies.

The real limiting factor with these throttle bodies is fuel supply, not CFM. I don't really believe Holley's CFM rating on these throttle bodies, the Sniper Stealth rating is extremely conservative in my opinion.

Speaking of fuel supply.....
That's why we run the Super Sniper Stealths with 8 injectors. Still a 4150 style throttle body but I can tell you they are still much larger and flow more CFM than the 950HP that we dyno'd these engines with.

Dad's made 724hp with a 950HP carb that only flows 870 CFM. Compare the carb to the Sniper Stealth. The carb has boosters in the way that hurt airflow. Sniper Stealth does not. Also when I mic'd the bores and throttle blades of the carb vs Stealth, the Sniper Stealth was larger in every aspect, by a lot. So I don't believe Holley's conservative CFM ratings on these things.

Because of this, I don't believe the Sniper Stealth will hurt power, only help, as far as air flow is concerned when looking at the 950hp carbs.

What I look at is only having 4 100 lbs. injectors. Still not horrible. If you want to keep them around 90% duty cycle and 60 psi of fuel pressure, having 4 100 lbs. injectors will still support about 720hp N/A on gas. And I've seen these on the chassis dyno support nearly that much at the tire and not have a fuel issue, so they'll support much more than Holley states. If you want to keep duty cycle around 80% which is very conservative, they'll still support about 650hp.

With that said, knowing dad's engine would be pushing the limits at 90% duty cycle, we opted for the 8 100 lbs. injector setup. Plenty of fuel and more airflow than the engine had with the previous carb. I also run the Super Sniper Stealth 8 injector unit on my 600hp 454 Chevelle. This same unit will be going on the larger engine I have plans for so I opted for the 8 injector unit now in preparation. I saw no need at all to go with an X-flow throttle body for our situations. Besides the fact that I want the holley carb appearance which the X-flow doesn't provide. When I talked to Holley and they didn't want to replace the 4 100 lbs. injectors in the Stealth with the 120 pounders that the X-flow has, I quickly saw this as a gimmick to try and upsell a different unit that didn't look anything like I wanted.
So that's another reason why we did the Super Sniper Stealths with 8 injectors. Now we have overkill fuel supply that will support well over 1000 HP and even support a power adder (yet the throttle body is still the same size, go figure ). Better yet, it looks like a Holley carb and everything on the car bolts on as it should, IE: air cleaners, throttle linkage, fuel lines, etc...

To add, the Super Sniper Stealth also has 3 extra inputs to monitor other vitals if you so choose. So you get some added electronic goodies when going to the Super setup over the base model.

[grivera]

Thanks for the detailed response. This is a snapshot of my 1/4 mile run.

[Scott65]

Whats the duty cycle at WOT top of high gear?

[i82much]

what if you borrowed a good 850 double pumper and made a few runs with it? not sure how difficult that would be but it would probably give you some good insight into how your car would react to the upgraded EFI.

[grivera]

Based on that snapshot I believe around 48.9%? I have the related datalog from that run but the file type isn’t supported on this thread.

[grivera]

Originally Posted by i82much

what if you borrowed a good 850 double pumper and made a few runs with it? not sure how difficult that would be but it would probably give you some good insight into how your car would react to the upgraded EFI.

I have a Cliff QJet built for the combo I can use but would require swapping distributor. A bit of a PITA but could try at some point.

[Formulajones]

Those datalogs are awesome and a wealth for tuning and troubleshooting.

Looks like a nice AFR throughout the run, I can see where you modulated the throttle a bit at the start, probably wheel spin.

I was curious about the duty cycle too. I might be wrong but appears that isn't check marked to datalog? I think the 48% shown in the box might just be the duty cycle at the time the snap shot of the datalog was taken, not the entire run?

I could be wrong on that but either way, with a nice steady AFR, and CL Comp looks really good at either -1 or -4%, hard to tell, but from what I see I wouldn't suspect there is a duty cycle or fuel supply issue. Looks like it's pretty well dialed in on the fuel side.

[grivera]

Excellent post FJ - thank you

[JLMounce]

Best way to tell if the throttle body’s flow rate is a problem is to look at the vacuum reading during a WOT run. If you’re pulling measurable vacuum, you’re flow limited.

The Basic Sniper/FiTech throttle bodies have been flow tested around 830 cfm. Just like a carburetor they can also benefit from simple modifications to increase flow rates where necessary.

Radius the lower throttle bore exit, knife edge the butterflies and cross shafts, use countersunk screws to connect the throttle blades to the cross shafts. Those simple mods will typically improve throttle body flow fairly close to 900 cfm.

If you think you need a good bit more flow I’d be looking at a dual throttle body system to achieve that, not a marginal upgrade over what your currently have.

[i82much]

Originally Posted by grivera

I have a Cliff QJet built for the combo I can use but would require swapping distributor. A bit of a PITA but could try at some point.

sounds too hard, but i bet you could start a fun discussion if you posted up your results comparing a Q jet to EFI ...

[grivera]

Originally Posted by i82much

sounds too hard, but i bet you could start a fun discussion if you posted up your results comparing a Q jet to EFI ...

Haha! Not sure how much fun that would be…��

[Formulajones]

Originally Posted by JLMounce

Best way to tell if the throttle body’s flow rate is a problem is to look at the vacuum reading during a WOT run. If you’re pulling measurable vacuum, you’re flow limited.

I guess one way to do that Jason would be to watch MAP at WOT, since MAP is basically vacuum, just in a difference format. As long as you see the MAP hit 100kpa at full throttle I'd say it's not pulling any vacuum. That's how I look at it anyway.

For example, the Sniper Stealth on dad's 571ci Pontiac will go straight up and over 100kpa at full throttle and hold steady there throughout a run, telling me even the Stealth flows enough air to support his engine and doesn't need a bigger throttle body, which coincides with what I was saying with the dyno session and the smaller 950HP carb.

Looking at the datalog that Will provided, he's showing 104 KPA. If I'm thinking correctly that tells me he has more than enough airflow for his engine.

[motowntuner]

If you are interested in selling your current Sniper system let me know. I have an old Holley commander 950 system and would love the upgrade. The autotune feature is desirable over doing the air/fuel mapping especially with a 12:1 compression motor.
Thanks for considering the sell.

Originally Posted by grivera

I can sell the current Sniper to recoup more than half the cost of the upgrade and already have an external regulator as the XFlow requires one vs the base Sniper which has an internal. The XFlow also monitors fuel pressure and ability for two other inputs like oil or trans temperature.

[grivera]

At this point I’m keeping it but if that changes I’ll advise

[RocktimusPryme]

Originally Posted by i82much

sounds too hard, but i bet you could start a fun discussion if you posted up your results comparing a Q jet to EFI ...

I switched from QJet to a Terminator. I didn’t make it to the track this year but I did once right after I swapped it. I had a a much harder time with traction so either the track prep was off or I was making more power.

As soon as spring hits I want to get out and get some runs with data.

[Formulajones]

We just recently had dad's on the chassis dyno with the Super Sniper Stealth and my theory of not limiting air flow was correct. In fact according to the dyno operator and doing the math, the engine is spot on and maybe a pinch better than the dyno runs with the 950hp carb. Part of that is because it also seemed to hold onto power about 200 rpm longer than previously.

[76TA462]

Hmm, I had a similar observation as RocktimusPryme when I switched to a Sniper EFI. Although it is stated that theoretically there are no power gains, my seat of the pants dyno readily noticed a sharp difference, very increased throttle response, and better tire shred ability. Maybe it is because the afr is more consistent? Disclaimer though, I also switched to a MSD billet from my OEM distributer at the time? Just observations, I don't know enough of the real workings to comment that way.