In­stalling Hol­ley’s Sniper TBI Fuel In­jec­tion

Chevy High Performance - - Contents - TEXT & PHO­TOS: Jeff Smith

In­stalling Hol­ley’s Sniper TBI Fuel In­jec­tion

Ahuge com­po­nent of per­for­mance is con­trol. If we can more ac­cu­rately con­trol the tim­ing of fuel and spark to the en­gine we will achieve a hap­pier, more pow­er­ful en­gine. For older mus­cle cars, this kind of con­trol used to re­quire a huge in­vest­ment in elec­tronic fuel in­jec­tion; a large, sep­a­rate ECU; an ana­conda-sized wiring har­ness; and plenty of es­o­teric elec­tronic skills. But not any­more.

Hol­ley’s en­try into the self-learn­ing, TBI-style fuel-in­jec­tion cat­e­gory is the Sniper. The ECU is built right into the body, which elim­i­nates much of the wiring har­ness has­sles. In fact, con­nect­ing the free­stand­ing wires re­quired a mere seven con­nec­tions. It doesn’t get much sim­pler than that. There were other con­nec­tions for the wa­ter tem­per­a­ture sen­sor, the oxy­gen sen­sor, and the con­nec­tor for the 3.5-inch dis­play, but those were sim­ple plug-ins. The Sniper TBI unit comes with an in­te­grated fuel pressure reg­u­la­tor. The Sniper uses four 100-lb/hr in­jec­tors and will feed up to a 650hp nat­u­rally as­pi­rated en­gine. The mount­ing flange of­fers a dual bolt pat­tern, and with an adapter can even be used on a spread­borestyle man­i­fold.

We de­cided to in­stall the Sniper on our friend Eric Rosendahl’s 468ci big-block El Camino, fig­ur­ing that a stout 525hp Rat would put the Sniper to the test. But be­fore we started the EFI in­stall, we first had to en­sure we had an ex­cel­lent fuel de­liv­ery sys­tem. We can’t overem­pha­size the point that good per­for­mance from any EFI sys­tem starts with a pro­fes­sional fuel de­liv­ery sys­tem. We opted for Hol­ley’s Retro­Fit fuel pump assem­bly. Our assem­bly came with a 255-lph

pump, bil­let alu­minum mount­ing flange, and Hol­ley’s unique Hy­dra­mat fil­ter/pickup that will pull fuel from any point of con­tact in the tank. This means if there’s even just a gal­lon of fuel in the tank, the Hy­dra­mat will pick it up.

We in­stalled that pump assem­bly in a new fuel tank and also retro­fit­ted the car with a com­plete new Ul­traPro con­vo­luted PTFE -6 fuel line. In the past, rub­ber-lined fuel hose has had dif­fi­culty main­tain­ing its in­tegrity over a long pe­riod of time. The rub­ber hose even­tu­ally be­comes brit­tle and be­gins to leak. Earl’s re­cently re­leased a new fuel hose ma­te­rial made from poly­te­traflu­o­roethy­lene (PTFE) that is im­per­vi­ous to methanol, ethanol, all those nasty ad­di­tives like ben­zene and toluene in gaso­line, and even to nitro­meth­ane. The hose is con­vo­luted (ribbed), which of­fers an ex­cel­lent bend ra­dius and makes it very flex­i­ble and easy to route.

The trade-off for this dura­bil­ity is the Ul­traPro hose is a lit­tle more dif­fi­cult to as­sem­ble than nor­mal cloth-cov­ered hose, re­quir­ing a spe­cific fer­rule and hose ends. But once you’ve as­sem­bled a cou­ple of the fit­tings, they go to­gether fairly eas­ily. The beauty of this hose is that once it is as­sem­bled, it should last the life of the ve­hi­cle.

We plumbed a brand-new Ul­traPro line for the high-pressure de­liv­ery side line and re-used the orig­i­nal 3/8inch fuel line in the car as the re­turn, re­plac­ing a sec­tion of the line that had been dam­aged af­ter 50 years in the car. We also in­cluded a Hol­ley 10-mi­cron fuel fil­ter lo­cated roughly half­way be­tween the tank and the en­gine so that it could be ac­cessed eas­ily for re­moval and clean­ing.

With the Sniper unit in­stalled

on the en­gine and the fuel lines plumbed, we took this time to wire the re­main­der of the elec­tri­cal side. As the Sniper in­struc­tions sug­gested, we elected to con­trol fuel only at this point. We will con­vert later to full elec­tronic con­trol over the ig­ni­tion. So the only wires we had to con­nect were the two large (12v+ and 12v) ded­i­cated power leads di­rectly to the bat­tery, switched power, and an rpm sen­sor to the ECU. Rosendahl had pre­vi­ously pur­chased a dual-ter­mi­nal bat­tery that pro­vided a place to con­nect the power leads di­rectly to the side ter­mi­nals.

The ECU also has a large blue wire that is the power lead (us­ing an in­ter­nal re­lay in the ECU) to drive the fuel pump. We de­cided to run a ded­i­cated ground wire from the elec­tric fuel pump all the way for­ward to the bat­tery to en­sure that the pump had full elec­tri­cal power. We also chose to build a two-wire Weather­pak con­nec­tor at the fuel pump to make ser­vic­ing eas­ier with a sim­ple plug-in con­nec­tor.

With all the elec­tri­cal con­nec­tions cre­ated, we were ready to start the ECU con­fig­u­ra­tion, but the heads-up dis­play in­formed us that our ECU was not prop­erly con­fig­ured. This re­quired re­mov­ing the small SD card from the heads-up dis­play and to plug it into a com­puter card reader to down­load the most cur­rent soft­ware from Hol­ley’s web­site.

This de­manded quite a bit of ef­fort on our part as the first two card read­ers we tried failed to make a con­nec­tion to the Sniper SD card. We tried a dif­fer­ent card and ul­ti­mately a third dif­fer­ent SD card reader in a third com­puter be­fore all the elec­tronic de­vices were talk­ing to each other. We’ve in­stalled

sev­eral other self-learn­ing throt­tle body sys­tems and this was the only one where we had to up­load new soft­ware in or­der to even to be­gin the process. This re­ally should have been ac­com­plished be­fore we ob­tained the sys­tem.

Af­ter even­tu­ally down­load­ing the soft­ware and jump­ing through the ap­pro­pri­ate elec­tronic hoops, the ap­pro­pri­ate icons ap­peared on the hand­held de­vice and we quickly in­put the nec­es­sary in­for­ma­tion.

Af­ter all that, we no­ticed we had no fuel pressure. A short in­ves­ti­ga­tion re­vealed the au­thor had wired the fuel pump back­ward de­spite check­ing to make sure the con­nec­tions were ac­cu­rate. A sim­ple switch of the ground and power leads solved that dilemma and the en­gine im­me­di­ately fired up and set­tled into a com­fort­able idle.

Af­ter set­ting the de­fault idle air/ fuel ra­tio at 13.7:1 and al­low­ing the en­gine to fully warm up, the only other adjustment was to fi­nal­ize the idle air con­trol (IAC) num­bers to bring them in line per the in­struc­tions. On the hand­held de­vice, we had com­manded the idle rpm at 850 yet the IAC was read­ing much higher at 30-35 counts rather than the

3-8 counts that the in­struc­tions men­tioned. The so­lu­tion might sound coun­ter­in­tu­itive, but in or­der to re­duce the IAC counts (which is ac­tu­ally a per­cent­age of the IAC open­ing), we needed to open the curb idle adjustment on the throt­tle body—much like on a nor­mal car­bu­re­tor.

By open­ing the throt­tle blades slightly, this al­lows more air into the en­gine and the com­puter then will com­mand the IAC mo­tor to close slightly, re­duc­ing the IAC count.

Af­ter a cou­ple of back-and-forth ad­just­ments, we man­aged to quickly achieve a sta­ble 850-rpm idle speed in Neu­tral (not in gear) that de­liv­ered an IAC count of 5-6.

We then went for a quick test drive and Rosendahl im­me­di­ately no­ticed that the throt­tle re­sponse was much crisper than with the

Hol­ley car­bu­re­tor—even with the same ig­ni­tion tim­ing. The Sniper throt­tle bores are the same size as the re­cently shelved 750 dou­blepumper car­bu­re­tor, so the only ex­pla­na­tion was that the Sniper of­fers slightly bet­ter off-idle con­trol over the fuel, which im­proved the en­gine’s re­sponse to throt­tle.

We had also fit­ted Rosendahl’s big-block with a new por­ta­ble,

five-gas ex­haust an­a­lyzer that we were us­ing as an eval­u­a­tor for both en­gine ef­fi­ciency and just how close the air/fuel ra­tio was to what was com­manded. The Sniper de­liv­ered nearly right on tar­get for al­most all the part throt­tle and idle com­manded air/fuel ra­tios. Us­ing this an­a­lyzer, we dis­cov­ered that the en­gine seemed to idle more ef­fi­ciently with a slightly richer air/fuel ra­tio at idle.

Ini­tially, we com­manded 13.7:1 but dis­cov­ered that by run­ning slightly richer at 13.2:1, the en­gine ac­tu­ally idled more ef­fi­ciently with higher CO2 read­ings. Our the­ory is that since the heads on this en­gine are older iron oval ports, the cham­bers are not the best in terms of ef­fi­ciency and need a lit­tle more fuel to com­mand a bet­ter idle ef­fi­ciency.

We also no­ticed that on de­cel­er­a­tion the en­gine seemed to run much richer than we an­tic­i­pated. We called Hol­ley and dis­cov­ered that the de­fault for the base Sniper sys­tem does not en­able the de­cel­er­a­tion fuel cut­off. This is a small thing, but should con­trib­ute to bet­ter fuel mileage—which is a mi­nor con­cern with this big 468ci Rat. This can be eas­ily en­abled by go­ing on Hol­ley’s web­site and down­load­ing the free Sniper soft­ware. This will then al­low us to con­fig­ure the Sniper to en­able de­cel fuel cut­off and then load that change onto the global con­fig­u­ra­tion file us­ing the SD card. The best thing to do is to read the Sniper in­struc­tions and fol­low the pub­lished pro­ce­dure. The next time we have ac­cess to Rosendahl’s car, we plan to make this change. This will be most no­tice­able dur­ing in-town driv­ing since that’s where de­cel fuel cut­off will likely have the most im­pact on fuel mileage.

Now that Rosendahl has put a few hun­dred miles on the com­bi­na­tion, the next step will be to con­fig­ure the ig­ni­tion sys­tem for dig­i­tal con­trol.

This will al­low us to make far more fi­nite changes to the ig­ni­tion in or­der to dial in the per­fect ig­ni­tion curve

for this en­gine. This does re­quire the dis­trib­u­tor ad­vance to be locked out. The Sniper will con­trol ei­ther a stan­dard in­duc­tive ig­ni­tion sys­tem or a CD, and both are easy to con­fig­ure.

The Sniper also of­fers dual elec­tric fan con­trols, a cou­ple of rev con­trol fea­tures, dig­i­tal wet ni­trous air/fuel ra­tio con­trol, data log­ging, as well as boost con­trol. These are ad­vanced fea­tures that can be in­di­vid­u­ally con­fig­ured but do re­quire some tun­ing ex­pe­ri­ence, so make these changes only if you are sure of the mod­i­fi­ca­tions you are in­putting.

Over­all, the Sniper in­stal­la­tion went smoothly and re­quired only a min­i­mum of tun­ing to dras­ti­cally im­prove the en­gine’s throt­tle re­sponse and drive­abil­ity. We took our time con­vert­ing over to the Sniper and it all went smoothly—es­pe­cially af­ter we fig­ured out we had wired the fuel pump back­ward.

Af­ter driv­ing the car, we do have one cri­tique. It ap­pears that Hol­ley has used a dif­fer­ent throt­tle link­age arm on the Sniper that short­ens the dis­tance from the throt­tle shaft to where the throt­tle pedal con­nects. This quick­ens the ra­tio and in­creases the ef­fort. This makes the car hard to drive in close traf­fic as pedal ef­fort is dra­mat­i­cally in­creased. This makes it easy to open the throt­tle too far. Hol­ley makes an adapter but we will prob­a­bly just make our own ex­ten­sion.

We still want to con­vert to full ig­ni­tion con­trol, and there are some mi­nor cold-start tun­ing items we’d like to ad­dress, but we’ll save those for an­other story. In a sin­gle high­way mileage test, the big-block did knock down 14.7 mpg. Not bad for a 525hp Rat. With a lit­tle bit of fine-tun­ing on the ig­ni­tion side, it might get a lit­tle bet­ter. CHP

01 | Eric Rosendahl’s 468ci big-block had been run­ning a mod­i­fied Hol­ley car­bu­re­tor with some suc­cess, but it was time for an up­grade. The Rat sports iron, oval port heads and a Comp hy­draulic roller cam mak­ing 525 hp and 560 lb-ft of torque.

02-03 | The Hol­ley Sniper throt­tle body comes in pol­ished, a slick gloss black, or the tra­di­tional dichro­mate look shown here. The bolt pat­tern is uni­ver­sal so it will bolt to nearly any four-bar­rel in­take man­i­fold. The stan­dard Sniper uses four 100-lb/hr in­jec­tors and will feed up to 650 nat­u­rally as­pi­rated horse­power.

04 | A cou­ple of weeks be­fore we be­gan the swap, Rosendahl pur­chased a new fuel tank from OPG to which we added a Hol­ley in-tank fuel pump kit. We don’t have the space to de­tail each step but the con­ver­sion took less than 2 hours. This kit uses a 255-lph pump that can feed 550 nat­u­rally as­pi­rated EFI horse­power. The kit in­cludes the Hol­ley Hy­dra­mat pickup/fil­ter that pre­vents loss of fuel pressure due to low fuel con­di­tions.

06 | Since the Sniper re­quires a re­turn-style fuel sys­tem, we elected to plumb the El Camino us­ing Earl’s new Ul­traPro con­vo­luted -6 fuel line. This PTFE fuel hose is im­per­vi­ous even to nitro­meth­ane and of­fers an out­stand­ing bend ra­dius so it won’t kink, but it does re­quire its own spe­cific fuel fit­tings.

05 | To fin­ish the fuel tank con­ver­sion, with the mod­ule in place we added a pair of 3/8 NPT to -6 male fit­tings for the pressure and re­turn con­nec­tions and also fit­ted the power and ground con­nec­tions with a two-pin Weather­pak con­nec­tor.

07 | The Ul­traPro fuel line re­quires spe­cific fit­tings us­ing this seal­ing fer­rule be­tween the fuel line and the fit­ting. The ta­pered end is threaded onto the con­vo­luted line, which seals be­tween the hose and the fit­ting.

All self-learn­ing EFI sys­tems like the Sniper re­quire a wide-band oxy­gen sen­sor. Prior to our in­stall, Rosendahl had his ex­haust shop weld in an oxy­gen sen­sor bung into the ex­haust. This bung is prefer­able but Hol­ley sup­plies a clamp-on sys­tem that does not re­quire weld­ing.

08 | The Sniper al­lows you to con­trol both fuel and spark but Hol­ley sug­gests you start with just the fuel us­ing your orig­i­nal ig­ni­tion sys­tem, which is what we did. So this re­quires only con­nect­ing the heavy red and black wires to the bat­tery, the yel­low to the neg­a­tive side of the coil, the pink wire to switched 12 volts, and the heavy blue wire di­rectly to the fuel pump. On the up­per con­nec­tor, the only one we used was the brown lead to trig­ger the tach.

09 |

10 | The only hic­cup in the in­stal­la­tion was af­ter first pow­er­ing up the sys­tem, an er­ror mes­sage re­quired down­load­ing up­dated soft­ware from hol­ley.com that had to be trans­ferred onto the SD card in the 3.5-inch dis­play. We had to try three dif­fer­ent SD card read­ers be­fore we even­tu­ally man­aged the trans­fer.

11 | The 3.5-inch touch­screen color dis­play is easy to use and al­lows you to quickly in­put the ba­sic in­for­ma­tion into the screen. Once we in­put the re­quired data, the en­gine started im­me­di­ately and set­tled into a de­cent idle. Here, the coolant is not up to tem­per­a­ture but with closed loop feed­back, Sniper is still re­mov­ing 20 per­cent fuel from the ini­tial tune at this en­gine tem­per­a­ture.

13 | We set our de­sired idle speed at 850 but no­ticed that the idle air con­trol (IAC) count was higher than the de­sired 3-8–per­cent set­ting. While this may seem coun­ter­in­tu­itive, turn­ing the idle speed screw clock­wise in­creases the amount of air past the throt­tle, which de­creases the IAC count.

12 | At first we used the de­fault idle air/fuel ra­tio at 13.7:1, then 13.5:1 (shown) and even­tu­ally to 13.2:1. Feed­back from our EMS five-gas ex­haust an­a­lyzer told us that this richer set­ting pro­duced a more ef­fi­cient idle qual­ity for this par­tic­u­lar en­gine.

14 | The Sniper works great, but we’ve still got some fi­nal touches to per­form with help from the free Sniper soft­ware we down­loaded. Small changes to cold start and af­ter-start en­rich­ment will dial in this sys­tem specif­i­cally for this par­tic­u­lar en­gine. This is the vol­u­met­ric ef­fi­ciency ta­ble. Un­less you have spe­cific tun­ing ex­pe­ri­ence, it’s best to leave ad­vanced tun­ing on these tables to a tuner with EFI ex­pe­ri­ence.

15 | Here’s the Sniper in­stalled and af­ter it had run for an hour or so. The only bit of fab­ri­ca­tion we had to do was to build a new throt­tle link­age arm out of 1/4-inch alu­minum rod and add a pair of fe­male spher­i­cal joints we found at the hard­ware store.

16 | Road test­ing the Sniper in­cluded eval­u­a­tion with the por­ta­ble EMS five-gas an­a­lyzer. We no­ticed that the Sniper de­fault set­tings do not en­able closed throt­tle fuel cut­off—as ev­i­denced by high HC read­ings on de­cel­er­a­tion. A Sniper en­gi­neer showed us how to ac­cess this and en­able the fuel cut­off us­ing the free, down­load­able Sniper EFI soft­ware.

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