Jenvey Heritage pinging issue .

[DuffyMahoney]

So it has to be some sort of injector issue, since thats really the only difference.  Glad you are up and running

 

[Tony D]

He's diagnosed it properly, and this is a known issue. The angle the injectors enter the bodies will impact the wall of the curved runners and make one hell of a Tau Layer causing those cylinder to run richer.

The issue isn't really 3/4 running rich, its that the other four are running lean and the spark knock is coming from the hottest cylinders. Cool off 5/6 at a minimum to resist hotter conditions that promote the knock, as well as dropping the thermostat value to 160/72C. 

Jet/Tune for 1-2-5-6 best lean torque or best rich torque depending on your tuner's preference and learn to live with that compromise....

 

Or switch to a Sequential Unit like MOTEC and then cut cylinder fuelling on 3 & 4, (and maybe ignition if necessary) on those two cylinders. This is common in high end turbo builds where you have to pull timing per cylinder based on the results from the dyno pulls. Make sure you have EGT and/or WBO2 on EACH cylinder and data log it during the pulls and you can dial it out with a MOTEC (maybe others, I've only been around MOTECs doing this type of tuning.)

For the $5000 the MOTEC will cost to fix it... likely just instrumenting up properly, fixing the cooling on the rear cylinders, and tuning for them and not off 3 & 4 and leaving them run rich will be the chosen approach.

NOW ALL THAT SAID...

For all those who poo-poo the Shorty Mikuni Manifold, these issues DO NOT exist with it, because almost every injector angle will impinge on it's back wall and make a big Tau Layer of fuel on which to draw... it's make for hell tuning for transitional emissions, but for quick and dirty tuning where you are not very strictly emissions controlled that is a way you get homogenized fuel mix in each cylinder because all the cylinders make the same "sharp turn down" before making any other adjustments for the head entry.

If you can find one, that is a cheaper option than going fully sequential and all that it entails.

[DuffyMahoney]

11 hours ago, Tony D said:

He's diagnosed it properly, and this is a known issue. The angle the injectors enter the bodies will impact the wall of the curved runners and make one hell of a Tau Layer causing those cylinder to run richer.

The issue isn't really 3/4 running rich, its that the other four are running lean and the spark knock is coming from the hottest cylinders. Cool off 5/6 at a minimum to resist hotter conditions that promote the knock, as well as dropping the thermostat value to 160/72C. 

Jet/Tune for 1-2-5-6 best lean torque or best rich torque depending on your tuner's preference and learn to live with that compromise....

 

Or switch to a Sequential Unit like MOTEC and then cut cylinder fuelling on 3 & 4, (and maybe ignition if necessary) on those two cylinders. This is common in high end turbo builds where you have to pull timing per cylinder based on the results from the dyno pulls. Make sure you have EGT and/or WBO2 on EACH cylinder and data log it during the pulls and you can dial it out with a MOTEC (maybe others, I've only been around MOTECs doing this type of tuning.)

For the $5000 the MOTEC will cost to fix it... likely just instrumenting up properly, fixing the cooling on the rear cylinders, and tuning for them and not off 3 & 4 and leaving them run rich will be the chosen approach.

NOW ALL THAT SAID...

For all those who poo-poo the Shorty Mikuni Manifold, these issues DO NOT exist with it, because almost every injector angle will impinge on it's back wall and make a big Tau Layer of fuel on which to draw... it's make for hell tuning for transitional emissions, but for quick and dirty tuning where you are not very strictly emissions controlled that is a way you get homogenized fuel mix in each cylinder because all the cylinders make the same "sharp turn down" before making any other adjustments for the head entry.

If you can find one, that is a cheaper option than going fully sequential and all that it entails.

This is one of the reasons I am trying to move my ITB to a fuel rail/ injectors at the head.  I plan to use my sk throttes, or go EFI hardware.  Then a balance tube at my throttle bodies with hollow injector bungs. This intake out of Japan.