I know there are lots of threads on plugs/n20/ls engines. And ive read most of them.

Heres my situation
Stock 5.3
ARP 2000 Rod Bolts
243 heads (milled .030)
BTR Stage 4 NA cam
Edelbrock Victor Jr Intake
demon 850 carb (stock jetting/setup 85/88 6.5pv)
NOS Cheater system (brand spanking new setup 57f 63n)
MSD 6012 controller (8* initial timing, 35* total by 2500 RPM 6* retard for the NOS)
Idle RPM is right about 1k


The 5.3 is in a jet boat. It runs very cool (surprised if its ever above 140)

Heres my issue

It keeps fouling the crap out of the plugs, if i run it at home and free rev it they will be black. So far i have had this issue with both TR6's and BR7EF's.

The TR6's ran okay at best. But they eventually got pretty fouled. The boat revs very cleanly and is very responsive. Runs a max RPM of 5200 on the motor.

Today, i figured i would try out the Nitrous system for the first time. Took it to the lake, and the boat ran like complete ****. Here's a video.


Being frustrated and disappointed. I did some quick googleing and came across a pretty generic answer of try new plugs.

So thinking to myself i figured why not try some stock heat range plugs. Went to the local Auto Zone and grabbed a set of NGK TR5's. Gapped them all right about .035 and threw the whole set in.

Boat ran perfect. 0 issues, 0 stumbling, 0 hiccups, couldnt of ran stronger.

I decided to spray it (again for the first time) I turned the retard on, launched the boat and sprayed it. Pulled really hard all the way to 6200 rpm. I only sprayed approx 3 seconds. In that 3 seconds i got a new GPS top speed of 75 (previous best today was 67)

Now i get to the real question.

I have done a lot of research prior to setting this Nitrous setup up. And the research all pointed me to either TR6's or the BR7's. These wont stay clean but the TR5's do?

Is it possible that because the engine runs so cold, the "cooler" plugs are literally just way to cold for my setup? Is it a good/bad idea to run the stock iridium plugs with the nitrous? I wont spray more than im spraying now.

Heres a picture of the plugs after the nitrous pull and about 3 minutes of NA running. Slight speckling im chalking up to running straight 91. Going to try again next weeked with some better fuel.



Heres a couple vids of it running. You can see it runs clean (both videos with the TR5's)
Nitrous pass

NA Pass

 

Do NOT run projected tipped plugs on the juice You're asking for trouble.

The specs on those tips are most likely your pistons starting to melt....step up to a better (higher) octane fuel....and get a NON-PROJECTED tip plug in that same heat range for NA....and a colder plug if you plan to keep spraying.

Now....as far as the heat range and the cold plugs....very well could be you found the issue. Sounds very likely that was it.

 

you're recommedning stock heatrange non projected plugs? Ill see if i can find the part number

 

All i can find in non projected are BR6's

I guess ill grab a set of those and try

should i consider dropping my jets down a little bit?

 

What fuel pressure and bottle pressure are you using ?

Did you flow test it (fuel) to set pressure ?

 

Fuel side of the NOS was set using a flow tool

its' set at 6psi flowing. Bottle pressure was low about 750

 

Jet sizes were at a good starting point.....cold bottle = low pressure and should have been fuel fat which isn't good either.

 

Yeah I know that

I had 950 psi in the bottle but by the time I got the plugs and got back on the water it was cold

Iordered some Br6ef plugs today. We will see how those work

 

85* is about 950psi

 

Yep! I had the bottle right about 88* (verified with my ir temp gun)

I let it sit in the bath tub while I loaded everything up then on the way to the lake it was on my floorboard under the heater vekt.

just the couple of hours it took figuring g out the miss fire and the48* wind blowing on it dropped the temp way down by the time iIwas aable to make the nitrous pass

this weekend should be better

 

It sounds like what you have is a carburetor that needs tuning. It is too rich and you are trying to compensate for that by running a very hot plug to stop them from fowling. You need to get a wide band and start tuning on the carburetor. If you are going to be running nitrous regularly, the BR7 is what will be safe.

If you get specs on your plugs that look like signs of detonation, pull more timing in 2 degree increments until the plugs look better.

 

im thinking about dropping the jets down a bit.

Also looking at a wideband setup

I hate tuning. Something i really never understood

 

Being open header will the wideband still work on only one bank?

 

Can you install a collector extension while tuning? Maybe something about 2' long?

 

not really. my headers have dynomax bullets welded on, then nothing

and no flanges

 

 

Post up a pic. Do the collectors have a place for the wideband sensor?

 

You should be able to run a wideband sensor on that setup

 

and it wont be a problem only reading the one bank? (i know nothing about wideband sensors)

Im looking at the AEM setup

 

You should be fine reading one bank for what you are doing