427 sbc with Sniper EFi headaches - Team Camaro Tech
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post #1 of 25 (permalink) Old Dec 27th, 18, 10:46 PM Thread Starter
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427 sbc with Sniper EFi headaches

Hi Guys,

I am relatively new here...

Car is a Camaro 1969 conv. Auto RHD (I am in Australia).

With the original 350 SBC (300hp) it was smooth but slow

The new SBC Dart SHP 427/AFR 210 heads/ CompCams XR294HR/ Sniper EFI, and all the rest of the good stuff.
On the Dyno it was great around 550Hp and 580lb all under 5700rpm, perfect for the street. Between the engine
Dyno and completing the installations, my engine builder and I had a "disagreement" about the responsibility of leaks...

Anyway, to my problem...

After a few hundred miles I decided to put it on the chassis Dyno, well that went bad besides only hitting around 350rwhp,
with only I pull I smoked out the whole workshop...

My tune is no good...

Here are my stats:

AFR
Idle 14.7
Cruise 14.7
WOT 12.8

Ignition
Idle 25
Cruise 36
WOT 36

IDLE jumps between 800-950, set to 900rpm

Is there a way to reset the the Sniper so it re-starts learning from scratch?

and are my starting points (AFR and Ing) ok?

thanks

Greg

Last edited by 69-Pace; May 25th, 19 at 10:48 AM. Reason: fixed type reset.
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post #2 of 25 (permalink) Old Dec 28th, 18, 04:36 AM
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Re: 427 sbc with Sniper EFi headaches

Here's a link to Holley's tech support (sniper product) site: https://www.holley.com/support/

They also have a phone number for talking to a tech support person: 1-866-464-6553. I realize you are in Australia, so you may need to add the USA country code in front of that number. If you go to the link above, you can email a tech and explain or provide your question(s) which would be cheaper than the phone call perhaps.

Would like to see a pic of a RHD 69 Camaro conv! Was this sent out from the factory this way?

Never argue with an idiot; they'll only drag you down to their level, then beat you with experience.

Last edited by 69-Pace; May 25th, 19 at 10:50 AM.
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post #3 of 25 (permalink) Old Dec 28th, 18, 04:43 AM
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Re: 427 sbc with Sniper EFi headaches

I assume you are using the Holley Sniper EFI. I would give Holley a call. Their tech support is good and they should be able to guide you on a better tune for your engine.
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post #4 of 25 (permalink) Old Dec 28th, 18, 05:16 AM
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Re: 427 sbc with Sniper EFi headaches

Are the stats you posted programmed target settings or readings with engine running data log?

My guess is possibly bad O2 sensor.

You can run the set up wizard to reset

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Last edited by Vega$69; Dec 28th, 18 at 05:29 AM.
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post #5 of 25 (permalink) Old Dec 28th, 18, 02:03 PM
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The Holley support forums are helpful and Danny is always there to help you solve your problems.

Steve
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post #6 of 25 (permalink) Old Dec 29th, 18, 10:09 PM Thread Starter
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Re: 427 sbc with Sniper EFi headaches

Hi Guys, and thanks for your quick replies,

the RHD conversion is a cut and flip job, so a mirror image of the LHD

The O2 sensor is correct as it matched the dyno reading...

The settings and reading on the hand controller as very close...

I guess its tech support time

wish me luck

thanks

G.
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post #7 of 25 (permalink) Old Dec 31st, 18, 03:48 AM
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Re: 427 sbc with Sniper EFi headaches

Good luck! Let us know the out come.

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post #8 of 25 (permalink) Old Dec 31st, 18, 04:33 AM
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Re: 427 sbc with Sniper EFi headaches

Self tuning algorithms generally donít work well with big cams. If itís running rich but giving good AFR readings check for exhaust leaks before the O2 sensor.

Don

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post #9 of 25 (permalink) Old May 23rd, 19, 08:34 PM
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Hello i am new to forum. I actually only register to reply to this post. I have sniper efi as well on my 437 started as a 427 but ate some vitamins and grew big and strong. You never mention trans or convertor. I never dynoed the motor but when I put it on a chassis dyno i too was disappointed. I only made 350hp 380tq to tire. For street caprice this is great but i was hoping for more. I have you tube channel my name is cfmechanic. Been driving over a year. To see someone else making similar numbers was shocking to say the least. I am in ventura california have th350 trans shift kit 3000rpm stall convertor and 3.42 rear gears car does 0-60 in 4 sec and weighs over 4000lbs. It could be faster but im satisfied. You making 550 580 at crank ans 350 to tire i feel much better. Old school automatics really seem to eat hp and not programming torque convertor also will cause low readings. I have since swapped intakes from dual plane to single and can feel the difference. Been tuning it with my laptop over a year now. Still learning everyday.
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post #10 of 25 (permalink) Old May 23rd, 19, 08:46 PM
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More info i have a cam that is 240/[email protected] .608/.614 lift 112 lsa run 160 thermostat Afr 195 race port heads dss gsx pistons flat tops 10.5:1 compression motown single plane intake 1inch spacer. With my cam i have to manually tune. If i transfer the learning to base i have to hook up laptop to lower the idle area back. When learning is added and smoothed idle gets too rich so i have to manually take fuel away at idle circuit. My map idle is anywhere from 70-50kpa i am at sea level. Cruise is 30-40 and wot is 80 and up. My afr targets are 14.1ish for idle 14.8 is for cruise and 12.8 for wot. I also have videos of car on dyno no smoke until you lift then I get some blow by. My machinist blames my 4inch stroke causing turbulence. I attribute it to wide ring gaps for nitrous. I plan on adding some power adder someday. I figure if your making 550 at crank I must be as well at first i was using the 15% rule and couldnt figure out where the horses went
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post #11 of 25 (permalink) Old May 24th, 19, 05:07 AM
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Re: 427 sbc with Sniper EFi headaches

Holley Tech Support should be able to help you. I've had to call them and they help me out and got my Vette running good.
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post #12 of 25 (permalink) Old May 24th, 19, 05:30 AM
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Re: 427 sbc with Sniper EFi headaches

350 rwhp does not translate anything close to 550-580 at the crank. Drive train loss, even with a TH350 is not almost 40%. Ballpark loss is 18% - 20% with the old school autos.

Have these engines been run on engine dynos to determine actual power #s?
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post #13 of 25 (permalink) Old May 25th, 19, 06:44 AM
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Re: 427 sbc with Sniper EFi headaches

Quote:
Originally Posted by Greg Katsap View Post
Hi Guys,

I am relatively new here...

Car is a Camaro 1969 conv. Auto RHD (I am in Australia).

With the original 350 SBC (300hp) it was smooth but slow

The new SBC Dart SHP 427/AFR 210 heads/ CompCams XR294HR/ Sniper EFI, and all the rest of the good stuff.
On the Dyno it was great around 550Hp and 580lb all under 5700rpm, perfect for the street. Between the engine
Dyno and completing the installations, my engine builder and I had a "disagreement" about the responsibility of leaks...

Anyway, to my problem...

After a few hundred miles I decided to put it on the chassis Dyno, well that went bad besides only hitting around 350rwhp,
with only I pull I smoked out the whole workshop...

My tune is no good...

Here are my stats:

AFR
Idle 14.7
Cruise 14.7
WOT 12.8

Ignition
Idle 25
Cruise 36
WOT 36

IDLE jumps between 800-950, set to 900rpm

Is there a way to rest the the Sniper so it re-starts learning from scratch?

and are my starting points (AFR and Ing) ok?

thanks

Greg
Quote:
Originally Posted by Vega$69 View Post
350 rwhp does not translate anything close to 550-580 at the crank. Drive train loss, even with a TH350 is not almost 40%. Ballpark loss is 18% - 20% with the old school autos.

Have these engines been run on engine dynos to determine actual power #s?
Lost in the middle of the OP are his engine dyno numbers. I'm no guru on this stuff but 40% does seem outrageous.

Jeff
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post #14 of 25 (permalink) Old May 25th, 19, 09:58 AM
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Re: 427 sbc with Sniper EFi headaches

A properly tuned engine making 500 RWHP is probably making low 400's HP (415-435) at the crank on an engine stand dyno. My only personal experience is with a Dyno-Jet chassis dyno, from what I've heard... Mustang Dynos will show slightly less HP on the same car.

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post #15 of 25 (permalink) Old May 25th, 19, 05:57 PM
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Re: 427 sbc with Sniper EFi headaches

Quote:
Originally Posted by 57vette View Post
A properly tuned engine making 500 RWHP is probably making low 400's HP (415-435) at the crank on an engine stand dyno. My only personal experience is with a Dyno-Jet chassis dyno, from what I've heard... Mustang Dynos will show slightly less HP on the same car.
You have it backward. Crank HP is always more than RWHP.

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