Speed-Talk is running on www.Speed-Talk.com

IMPORTANT: Update your bookmarks to https://www.speed-talk.com/forum/
(Right-click the URL and select "Bookmark this link")

Holley sniper on engine dyno

General engine tech -- Drag Racing to Circle Track

Moderator: Team

Post Reply
apm
Member
Member
Posts: 81
Joined: Sun Aug 04, 2013 11:21 pm
Location:

Holley sniper on engine dyno

Post by apm »

How many guys out there have experience using a Holley sniper or sniper stealth on an engine dyno?
I've been running my dyno for around 6 years now and average about 125 engines per year . I believe the dyno is very repeatable , but I'm finding when running engines with holley sniper kits the the engines are very eratic ,the air fuel numbers are always changing drastically from one pull to another, even when making no changes to the settings and it just won't repeat very well at all , it makes it very hard to test spacers or timing changes or any change for that matter as the ecu does not seem to repeat at all.
I'm not bagging the system what so ever , I sell loads of them and all my customers are happy but I'm just struggling on the engine dyno a bit .
I usually stick with most of the std system settings but lately I've been playing with all sorts of things but nothing seems to help this issue ?
Any help or input is appreciated
lewy-d
Member
Member
Posts: 103
Joined: Wed Sep 02, 2009 9:26 am
Location:

Re: Holley sniper on engine dyno

Post by lewy-d »

I've seen problems with any of the 4bbl style efi (non-port injection) when used on a dual plane intake. they do the very thing you describe, erratic AFR. Especially when viewed bank to bank and watching fuel trims/corrections. We've tried open a 4 hole spacers and all combinations of both. We even milled the divider out of a SBC intake. It helped, but was still not good. In our instance the solution was to use a single plane.
Good luck. Those issues can be super frustrating.

Lewy
PRH
Expert
Expert
Posts: 959
Joined: Fri Sep 08, 2017 4:16 pm
Location: S. Burlington, Vt.

Re: Holley sniper on engine dyno

Post by PRH »

That would be a simple enough test to try on the dyno.
Swap from a dual plane to a single plane and see if the repeatability improves.
Somewhat handy with a die grinder.
RevTheory
HotPass
HotPass
Posts: 5391
Joined: Thu Sep 04, 2014 6:45 am
Location:

Re: Holley sniper on engine dyno

Post by RevTheory »

Vizard had a thread on here a few years back where they were dealing with finicky, erratic performance on the dyno. They swapped out the Sniper for a known-good dyno room carb, got it dialed in, went back into the Sniper program with the timing and a/f ratios and it was finally at least as good as the carb was.

I think it was just still stuck in learn mode.
User avatar
mt-engines
Pro
Pro
Posts: 295
Joined: Fri Sep 27, 2019 12:35 pm
Location: MN

Re: Holley sniper on engine dyno

Post by mt-engines »

Tuning must be done in open loop.
induction apprentice
Expert
Expert
Posts: 774
Joined: Sat Jun 30, 2012 3:12 am
Location: Canada

Re: Holley sniper on engine dyno

Post by induction apprentice »

I have no idea what is causing your non repeatabillity. But one other thought aside from intake signal stuff.
Is the O2 sensor on the dyno must have a very long pipe extending past where it is positioned or backwash from the room air will violate the readings as well as any header leaks. So minimum 15 inches after O2.
With that said I believe even when not in learn mode the target air fuel and O2 can influence the ECU. So if exhaust sample is eratic. So will be the tune. So open loop is imparative if O2 signal is not stable.

Good luck.
rebelrouser
Guru
Guru
Posts: 1288
Joined: Tue Sep 15, 2015 2:25 pm
Location:

Re: Holley sniper on engine dyno

Post by rebelrouser »

apm wrote: Wed Jan 13, 2021 7:23 am How many guys out there have experience using a Holley sniper or sniper stealth on an engine dyno?
I've been running my dyno for around 6 years now and average about 125 engines per year . I believe the dyno is very repeatable , but I'm finding when running engines with holley sniper kits the the engines are very eratic ,the air fuel numbers are always changing drastically from one pull to another, even when making no changes to the settings and it just won't repeat very well at all , it makes it very hard to test spacers or timing changes or any change for that matter as the ecu does not seem to repeat at all.
I'm not bagging the system what so ever , I sell loads of them and all my customers are happy but I'm just struggling on the engine dyno a bit .
I usually stick with most of the std system settings but lately I've been playing with all sorts of things but nothing seems to help this issue ?
Any help or input is appreciated
Never used a sniper on the dyno, but did one with a Fitech, and a procharger. I was not chasing HP mainly just seeing if the engine was ready to install in the car. If I understand your post right, I think what is messing with you is the self learning capability of the injection system. A carb does not try to learn, it is what it is, we make it learn with jets and airbleeds.
If the sniper is the same way, you have a dialog box where you tell the computer what air fuel ratio, you want for different driving modes, and some timing tables for the ignition. Then while it is running you should see some fuel trim numbers on the computer that will tell you how much the computer is modifying the fuel tables you set to get to what you have asked for. On stock vehicles where this technology came from, you have short and long term fuel trim numbers, basically short term fuel trim is where the computer is jumping around on the fuel tables trying to decide if it needs to shift the fuel tables, the long term trim is telling you if it has made the move to shift the fuel tables. Until that computer has settled on what kind of fuel map it is going to use you are not going to get the same air fuel ratio on every run.
I used to mess a little with an old ACELL injection system on the dyno and it was much like a carb, but you had to set the fuel tables yourself, from looking at O2's and exhaust temps. It always tuned about like a carb, even though it had an injector for each port. It did not have any self tuning capability.
Now in driving my fitech vehicle for a few miles, when I check it and I find that for example the trim numbers are excessive lean or rich, then I go back into the program and change the pulse width of the injectors. It runs the best when in all modes of driving the fuel trim numbers are close to zero, or what ever number they use to indicate center on the fuel tables. That way if you have a big change in temp, or weather, the computer has plenty of room to move the tables to get it to run right, if you are heavy on the trim it might not have enough left to get a good A/F.
If the Sniper will let you cancel the self learn, that might be the way to go, get your tables set manually, and then activate the self learn and then the computer will keep it right where you set it.
racear2865
Guru
Guru
Posts: 1521
Joined: Mon Sep 21, 2009 11:58 pm
Location: tenn

Re: Holley sniper on engine dyno

Post by racear2865 »

We fire a lot of EFI engines on our dyno. On any learning system, we let it run on dyno for at least 45 minutes, but for any power run , we go to open loop and watch the plugs .
reed
Bill Chase
HotPass
HotPass
Posts: 141
Joined: Tue Aug 27, 2019 1:11 pm
Location: Michigan

Re: Holley sniper on engine dyno

Post by Bill Chase »

Fast man efi will do one on one training with the holley systems and can cater it to your skill level with the system. That and all of the Holley training stuff. If you'll be using the systems more.. learn all the advanced things it's capable of.

There are several posts about the sniper and terminator efi tbi setups and dual plane intake issues on the holley forums, also some extremely knowledgeable guys there. Doug F. Of Holley occasionally pops in, and he had a hand in development of the current systems. Register over there and do some reading, forum has been up and running for about a decade now. It isn't as focused as speedtalk, and you have to read 20 posts about people making wiring mistakes to find 3 good posts with technical explanation and support.. but the info is there, and you'll quickly zero in on the guys that know wtf they are doing. Makes searches for specific info a lot easier.
User avatar
Rick!
HotPass
HotPass
Posts: 202
Joined: Fri Jan 01, 2016 4:13 pm
Location:
Contact:

Re: Holley sniper on engine dyno

Post by Rick! »

What other EFI systems do you run on your dyno? Dominator, HP? Other?
Do your O2's read fine on carbed or other EFI setups?
What do the plugs "say" for the Sniper engines?
You've run a bunch of Holley EFI stuff so you're familiar with enabling and disabling closed loop, yes?
Since Snipers only read one O2, do you switch it side to side on the dyno headers to evaluate both banks?
Fuel pressure and flow are fine? Rock solid 58psi feeding the throttle body? Proper return line from the regulator? Running a proper sized pump or the dyno pump?
Other than the single plane/dual plane thing, have you tried any RFI remedies? Any prevention of ground loop feedback?
Where is the ECU located in relation to the coil?
Any data logs/dyno sheets you can share of power runs?
Post Reply