Tuning Sniper Progressive Link

Posted by Chris Myer 10/14/20 12 Comment(s) Sniper and Terminator X,

Sniper Progressive Secondary Link--A Great Solution for Abrupt Throttle!

When folks install their new Sniper 4150, Super Sniper 4150, or Sniper XFlow on their high-horsepower engine, usually there are two reactions.  First, “Wow, does this deliver some amazing power!”  Then, about the time they get in to a situation where a deft touch of throttle is required, “Wow, I need a way to manage that power!”

At 800 and 900 CFM for the Sniper / Super Sniper and XFlow (respectively), these throttle bodies can really be a handful at throttle tip-in, particularly when the situation calls for one to behave themselves.  If the car has a naturally stiff throttle pedal that just makes the situation that much more challenging.  That’s why folks who install the progressive link that we offer almost universally have the same response:  “Why in the world didn’t Holley deliver the Sniper with that in the first place?”

In a few cases, however, progressive link users find they get a little rich bog when they tip into the throttle with the progressive link installed.  Fixing that is easy and I’m going to show you how.

Configuration Adjustments for Progressive Link Use

When you learn how the Sniper manages acceleration enrichment it is not surprising that you might get a little rich bog when you add the progressive link.  The acceleration enrichment that is calculated based on the throttle position is expecting four barrels of air to be dumped into the manifold.  But with your progressive link installed it is only going to dump two barrels of air in until such point that the secondaries are added. 

Have a look at the default AE vs TPS table for the Sniper, shown below.  You can find this only by using the Sniper Software.  AE vs TPS is not tunable using the handheld.  If you download your configuration from your ECU either to the SD card or directly to the software (if you are using a CAN-to-USB adapter cable) then  click on the fuel injector icon (at the top nav bar), then Acceleration Enrichment (on the left window), then AE Correction vs TPS (at the top-right of the main window) you’ll see this:

Default AE versus TPS Configuration
Default Acceleration Enrichment versus TPS Configuration

As you see above, the Sniper is going to dump in a maximum amount of fuel  at zero TPS, begins to remove acceleration enrichment at 60 percent TPS, and then removes all acceleration enrichment correction at 100% TPS.  Perfect—if you have the original synchronous linkage.

Now that you are bringing the secondaries in later you will need the same amount of acceleration enrichment but you need it applied at a different rate.  Instead of bringing in all the fuel at zero TPS, you will initially bring in half the fuel, and taper it off at the same rate as the original graph above.  Now you’re going to bring the other half of the fuel in at the secondary tip-in point, but you need to taper it off more rapidly so that you’re still at zero percent correction at 100% TPS.

AE versus TPS Configuration for Progressive Link
AE versus TPS Configuration for Progressive Link

The example above is a good starting point if you have the fixed progressive linkage.  Depending on your specific installation, those usually come in between 45% and 50%.  If you have the adjustable progressive linkage, you’ll need to change the chart above to match your particular secondary tip-in point.  Save the configuration file with a new name, upload it to your Sniper ECU, and enjoy the improved throttle response.

In my experience, you don’t have to worry about getting this too dead-on.  For 90% of the users if you’re within a few degrees TPS and a few percent AE correction either way it’s going to be fine.  Of course, a geek like me creates a spreadsheet that lets me calculate this for customers based on their specific tip-in point.  And if you’re that into it you’ll also want to datalog the tip-in event just above and below the tip-in and try to fine tune this.

 (Note:  The Sniper progressive link does not work on the Sniper Stealth throttle bodies or any of the two-barrel Sniper variants.  If that’s you then we recommend that you try the throttle lever extension instead.)

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12 Comment(s)

Bret C:
10/15/20, 05:31:41 PM
Reply

My experience was actually a little opposite. My motor wanted more gas when it was on the 2 barrels and the fixed link that came in at 48%. Your progressive link would help change it to 20% as a guess. I went back to the way they sent it. With 4:11 gears and a 4 speed munci it is easy to drive.

Chris Myer:
10/23/20, 01:11:24 PM

And I would be quick to point out that there are TONS of folks out there running this without modifying the AE vs TPS with great results. This definitely falls into the "If it ain't broke, don't fix it" category!

Gary Patrick:
10/15/20, 05:52:31 PM
Reply

I have heard that some people have had problems with the progressive linkage due to the location of the IAC port. Since the IAC is on the back of the throttle body there may be some dual plane manifold setups using a 4 hole gasket or spacer where the front two barrels are not instantly seeing/sensing the opening of IAC when the front throttle blades are moved. Are there any problems setting up the progressive linkage with this configuration or should an open spacer be used?

Chris Myer:
10/23/20, 01:13:15 PM

I run my progressive-equipped Sniper with a 4-hole 1/4-inch phenolic spacer. Works absolutely flawlessly.

Bob Slomba:
10/15/20, 06:26:07 PM
Reply

Since I bought the progressive linkage car is more drivable and wife not complaining about backlash.

Chris Myer:
10/23/20, 01:14:39 PM

Thanks for the report Bob! That's exactly the driveability improvement the vast majority of folks are experiencing. And as I say, "Happy wife, happy life!"

Louis Belloisy:
10/18/20, 02:48:09 PM
Reply

Hi Chris, I have had this problem from day one on the install of the linkage. I followed your instructions and I can't believe the difference. Its a perfect acceleration.Lou Belloisy

Chris Myer:
10/23/20, 01:15:44 PM

You're becoming a tuner, Lou--Great Job!

Ken Lang:
10/28/20, 02:46:48 PM
Reply

Hi Chris. Just an update. I installed my fixed progressive linkage today and made the change to the AE table. Big improvement and I'm excited to drive the truck more. The engine runs great and is seamless going into the secondaries.

As a side note, my transmission shifts much better now too! Not better but more appropriately. I'm running a 4L60E and using the stock CPU to operate the transmission. I have a second TPS on my Sniper to provide the signal for the transmission. It never seemed to downshift quite right and now it's spot on.

My reasoning is this: The original TBI on the truck was around 400 CFM I believe. With the progressive linkage opening at 50% on the TPS most of your casual driving is on the primaries only. The engine sees this as the original 400 CFM TBI and likewise the accelerator travels further during normal driving than it did when it was 1:1. That said, the TPS is then also moving more and I think more in line with what the transmission CPU is expecting so it downshifts more appropriately now. Love it.!! Thanks for the new article on modifying the AE table. Big help!

Chris Myer:
11/11/20, 04:18:25 PM

Your logic seems sound to me and the proof is in the results. Great work--thanks for the insight!

Wayne Steele:
11/14/20, 07:44:40 AM
Reply

I have a new sniper not yet run. Should I do the initial set up before I add the progressive linkage? Or can I go straight to the progressive linkage for the first start up?

Mike Parsons:
02/1/21, 05:34:59 PM

Couldnt agree more here.

Chris Myer:
11/16/20, 05:30:49 PM

I am a huge fan of "keep it simple". My motto is don't add any complexity to the initial installation that is not absolutely necessary. Certainly progressive links are in the category. Do a basic installation, run the setup wizard,and get everything working. Then, when you are confident you don't have any issues, add in the progressive link. Otherwise you have complicated the initial installation process and will likely end up taking the progressive link off if you have any problems--whether that is the problem or not.

John:
11/25/20, 08:31:27 AM
Reply

My understanding is, if you have or are using vacuum advance the progressive link is a no go unless you get rid of the vacuum advance. Doesn't the vacuum advance need the back two barrels to work properly?

Chris Myer:
12/1/20, 04:21:45 PM

Certainly one would come to your conclusion by reading the Sniper installation instructions. There it provides a diagram of the throttle body with three vacuum ports. The ported vacuum is labeled as follows:

3/16" Ported Manifold Vacuum (Vacuum Advanced Distributor)

And while that is "a" a source for distributor vacuum advance it is not the only one. In fact, unless your engine was designed to use ported vacuum with its distributor you should NOT use that vacuum port. And, in my opinion, even if the original did use ported vacuum you may be better off not using it. Check out this article from Super Chevy and any of a dozen threads on the topic on The HAMB. They will tell you the same thing: Don't use ported vacuum for your vacuum advance. Now the problem with the progressive link disappears (along with a host of other issues associated with ported vacuum advance.) :-)

Scott Waddell:
01/3/21, 08:38:56 AM
Reply

I have fixed progressive link and it is much more drivable with a manual shift. This appears (to a novice) that it could have an impact on MPG. I'm still only getting 11mpg no matter how easy I am on the throttle..I don't drive it much...Sniper still learning...please comment. thx

Chris Myer:
01/5/21, 04:06:26 PM

It turns out that changing to a progressive link will not have any measurable impact on your fuel economy. Having a light touch on the throttle will help, of course, but the EFI system calculates the amount of fuel to be injected completely independently of the number of bores through which it is sprayed. If sprayed through four barrels, 25% is sprayed into each barrel. If sprayed through two, then 50%. In either case, 100% of the calculated amount is injected.

The key to getting better fuel economy from a basic Setup Wizard tune is to lean out the target AFR numbers in idle and cruise areas. Better yet, switch from the "simple" target AFR to 2-Dimensions (requires using the software rather than the handheld.) I don't have an article on how to do that at the time of this writing but I do have an article on how to do that for timing advance and the concept is similar. BTW, this "configuration enhacment" is a service that we offer at no cost for customers who buy their EFI systems from us or as an add-on service for those who purchased elsewhere before hearing about us. (Click here and select "Level 2 Configuration Enhancement".)

Wesley L. Holt:
02/2/21, 11:04:28 AM
Reply

Got my progressive linkage in today going to install reset in hand held and see what happens. I have my vacuum hooked up to intake. After hook up should I go through the steps to reset idle or should it still be fine. Thanks

Chris Myer:
02/2/21, 06:06:52 PM

By all means do check that IAC at warm idle and ensure that it is still in the low single digit range. But in most cases I have not found that installing the progressive link changed anything on this.

Henry Oldach:
09/26/21, 10:55:43 AM
Reply

I installed my progressive link yesterday and It seems like it is going to really help in my application. Just a question though, should I reset my setup and allow the computer to relearn my car with the progressive link on, or should it not make a difference? The car is a 65 mustang with a 347 and a T5. It is 450hp and 451ftlb of torque. In certain scenarios I really struggled with the aggressive tip in.

Chris Myer:
09/26/21, 05:36:33 PM

It may benefit from some learning but that is going to happen regardless. Since you don't want to discard all of your learning it is best to leave what you have in place and let it learn from there. As long as you have followed the instructions for adjusting the AE vs TPS above then you should be close enough that it will do great.

Henry Oldach:
09/27/21, 07:25:28 AM

Thanks Chris, I did not adjust my AE vs. TPS as you noted above as I thought that was an optional step unless you notice you are having issues. I can do that this week. On my first test drive the car actually drove great. For my setup the progressive link is an absolute must.Thanks!

JC Petermeier:
11/23/21, 09:26:24 AM
Reply

Would this work on the throttle lever extension too?

Chris Myer:
11/26/21, 09:36:45 AM

These are two entirely different solutions to the same problem but yes, sometimes folks end up using both.

Jack Crognale:
05/23/22, 08:13:30 PM
Reply

Installed the progressive linkange on my Sniper EFI that is installed on a 454HO. Runs really nice with a very smooth and predictable tip in. I didn't have to make any tuning adjustments at all. Cheers

Chris Myer:
05/28/22, 03:01:42 PM

I'm glad this worked so well for you. Indeed, this is the case the majority of the time. But in those instances where the progressive link creates a little off-idle stumble, the information above provides a relatively easy solution.

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