EFI twin plug gap and type

IMR-Merlin · 05-18-2015, 03:34 PM

Anyone know if I should use factory 930 plugs (and gap) for my EFI twin plug car?

Just getting the valve adjustment back in and when I pulled the plugs there were autolite plugs in there and they look pretty black from running rich.

Thanks

xbmwguy · xbmwguy's Garage

ive been running bkr8eix for some time now with a gap of 22 and cop with no blown out spark in the 20psi range.

xbmwguy · xbmwguy's Garage

what coils?

IMR-Merlin · 05-18-2015, 04:19 PM

Electromotive Tec3

GJF · 05-18-2015, 04:20 PM

NGK 8's are pretty much the plug to run. Bosch silvers in heat range 3 are eccentially the same spec plug. .022 is the ticket as well, exactly what Frank stated. If you try over .024 then they start to blow out. At over 1k I tried going to 9's. But they were too cold. I went back to 8's. Been well past 20psi with no issues. The BKE8EIX are nice because they have a 5/8 hex instead of 13/16, which make it easier to deal with when installing or removing.

IMR-Merlin · 05-18-2015, 05:10 PM

Great, thanks guys.

The car had Autolite 4062's in there, gap was .020 +/- I like the BKE8EIX idea.

This engine had a 9% leakdown on one cylinder and I had zero valve lash on one intake valve, so i am hoping that was it...

smurfbus · 05-18-2015, 09:02 PM

All the talk about non resistor plugs with EFI being very BAD idea what is the situation with 930 EFI setups? I would first like to run fuel injection with my current 'MSD/blaster/superconductor_wires/resistor_less spark plugs' setup by adding a VR/pulley and a cam sync HALL sensor on the air pump housing. Possibly MS3-PRO for ECU. The VR sensor installs pretty close to the distributor!

I have unused org Bosch w3pdo platinium plugs (expencive) to use but are they going to give me too much trouble with MS3-pro and VR+HALL? I could try to sell my plugs unused if the EMI is a big problem even with only the fuel injection.

IMR-Merlin · 05-19-2015, 02:50 AM

I am also running the Taylor Spiro-Pro wire. So does that change the plug to a non-resistor?

Just curious

Tippy · 05-19-2015, 05:39 AM

Quote:

Originally Posted by smurfbus

All the talk about non resistor plugs with EFI being very BAD idea what is the situation with 930 EFI setups? I would first like to run fuel injection with my current 'MSD/blaster/superconductor_wires/resistor_less spark plugs' setup by adding a VR/pulley and a cam sync HALL sensor on the air pump housing. Possibly MS3-PRO for ECU. The VR sensor installs pretty close to the distributor!

I have unused org Bosch w3pdo platinium plugs (expencive) to use but are they going to give me too much trouble with MS3-pro and VR+HALL? I could try to sell my plugs unused if the EMI is a big problem even with only the fuel injection.

Use resistor plugs. Lesson learned here.

Speedy Squirrel · Speedy Squirrel's Garage

EFI with no noise suppression would be bad. If you can hear static on the AM radio band, it is not good.

The W3DPO spark plugs are designed to go with the original braided/shielded wires, which have the resistor built into the connector. That is why they are non-resistor.

smurfbus · 05-19-2015, 07:34 AM

No radio on my car but I could test some portable radio later or should the power come from the battery for diagnosing. Maybe this is irrelevant as its a bad idea anyway to try and run resistorless plugs with efi. They have improved the EMI resistivity with ms3-pro though.

Tippy · 05-19-2015, 08:05 AM

Quote:

Originally Posted by smurfbus

No radio on my car but I could test some portable radio later or should the power come from the battery for diagnosing. Maybe this is irrelevant as its a bad idea anyway to try and run resistorless plugs with efi. They have improved the EMI resistivity with ms3-pro though.

To me its a no brainer. Noise is THE worst thing IMO you can have with EFI. You cannot tune it properly ever unless it's dialed out.

Speedy Squirrel · Speedy Squirrel's Garage

I think it is a good idea if you are using a capacitive discharge ignition that does multiple spark. They work best withe the lowest possible secondary resistance.

smurfbus · 11:11 AM

Optimally I would like to first just do fueling and possibly later ignition. My current ignition is very strong (plus I have two simple maps behind a switch) so I feel like it would be downgrade to change to cops or alike? Ls2 has had good reviews but changing all at once has more possibilities to something go wrong compared to doing it in stages if at all butthe EMI issue still remains. My plug wires are rfi resistant though.

Speedy Squirrel · Speedy Squirrel's Garage

Quote:

Originally Posted by smurfbus

Optimally I would like to first just do fueling and possibly later ignition. My current ignition is very strong (plus I have two simple maps behind a switch) so I feel like it would be downgrade to change to cops or alike? Ls2 has had good reviews but changing all at once has more possibilities to something go wrong compared to doing it in stages if at all butthe EMI issue still remains. My plug wires are rfi resistant though.

I also started with fuel only. Same logic as you stated.

xbmwguy · xbmwguy's Garage

I have seen guys working frantically for hours even days trying to figure rough running/ no start issues only to switch plugs to resister and all problems gone. Save yourself the hassle. And yes use the air pump pulley for your cam signal for full sequential ms3.. It works great

IMR-Merlin · 05-19-2015, 04:02 PM

so, bottom plugs are much smaller than top plugs, including thread size. I am new to twin plugs, so it's a learning curve.

ficke · ficke's Garage

Quote:

Originally Posted by IMR-Merlin

so, bottom plugs are much smaller than top plugs, including thread size. I am new to twin plugs, so it's a learning curve.

On some engines. that is the easier way to do it. I have seen in the old days motorcycle plugs ran at the bottom. Also if people run same size plugs there is a clearance issue with the head bolts that can be overcome, but what a hassle.
Twin plugging an engine has no real bearing on plug style, gap. Timing is what is really changed with twin plugging, you can run much less advance and actually you need to run less advance.
Anybody running single plug timing on a twin plug engine is leaving hp. on the table.

IMR-Merlin · 05-19-2015, 04:16 PM

Quote:

Originally Posted by ficke

On some engines. that is the easier way to do it. I have seen in the old days motorcycle plugs ran at the bottom. Also if people run same size plugs there is a clearance issue with the head bolts that can be overcome, but what a hassle.
Twin plugging an engine has no real bearing on plug style, gap. Timing is what is really changed with twin plugging, you can run much less advance and actually you need to run less advance.
Anybody running single plug timing on a twin plug engine is leaving hp. on the table.

They are tiny plugs for sure. Anyone have a baseline for timing to get started?

xbmwguy · xbmwguy's Garage

Merlin just as gjf stated above its much easier with the smaller hex size especially on the bottom as all machine shops vary in size and even angle ( that's why I had bill at Xtreme do mine) but you want to use same plugs on top and bottom I think, even though there has been discussion of diff heat range on bottom vs top. With any Efi system noise is the killer. CORRECT GROUNDING to a common spot on the block to even include your wideband ground is as essential as resister plugs. There I ranted. I'm done