I will start off by saying that not every combination or engine is the same. After reading here numerous times that setups over 450HP and higher than stock compression should switch to the TR6 I decided to make the swap. I was prepping my car for the Shootout and fresh fluids with a fresh set of plugs is my normal routine, so it seemed the opportune time to make the swap.

My first pass in Memphis was a 11.61@112 w/ a 1.62 60'. The air/fuel was rich (7-8:1 according to the LM1) so I leaned it out a good bit. The second pass was again an 11.61, but this time at 117mph with the same 60'. The air/fuel on this pass was 12.4-13.1 so I left it alone. This was 4 tenths and 5mph slower than my last trip to the home track in very hot & humid conditions. I also noticed the car felt sluggish and throttle response was a little slower than normal.

The only thing I changed about my setup was the plugs from the previous outings, so I decided to start there. That night I went to the auto parts to get the TR55's then back to the track and swapped them out. Test and tune was over so the next pass will be first thing in the morning. To my surprise with only a plug swap the car felt great and the time slip showed it: 10.59@126 w/ a 1.45 60'. Everyone pitted around me knew I was having problems and was swapping plugs. The most common statement of the morning was "Where is the nitrous bottle hiding? Because I know you didn't pick up a full second and 9 mph from a plug swap!'

Moral of the story is(as usual) don't believe everything you read on the internet. I would say for most N/A setups still running pump gas that the TR55 is the way to go. I had no reason to swap other than what I read here and have never had a problem with the TR55's. For the record my setup is 11.5:1 SCR with the components listed in my sig. I hope this info will help a few others who may be wondering "Why is my setup not as fast/not making as much power as it should?".

 

I would typically agree your setup should be running the TR55's. BUT, to say that the time was due to the heat range is sort of a long-shot....with the TR6's in good shape, not fouled or anything, and gapped the same, the times would not have changed significantly if at all. What did the TR6's look like when they came out?

 

They looked great. I pulled one after the second pass to double check what the LM1 was saying. I think the A/F guage is a useful tool, but do not trust it as the only means of tuning. I should have noted that the TR6's were gapped at 0.036 and the TR55's at 0.055.

I know it is a long shot and it is honestly still astounding to me. This was the only change to the car between the 2 passes.

 

Unless a person can go WOT, stop right after turning off the track and stop the motor, its hard to get a good read on a plug, you want to see the plug at the hardest possible part of the pull. Idling will change the plug's look.

TR-6's give you a safety range and depending on track location and conditions as well as general street use I always put them in when making over 400 on my LT1 as I felt they were safe and I was running 44 deg of timing.

I think plug choice is a personal opinion as it is their motor they are racing with. Good info none the less!

 

Well I have switched from Tr-55's to Tr-6's and I experienced less knock retard. I was also able to add a few more degrees of timing @ 4000 rpm. It did not change my track times at all, but my setup is 11:1 static and 9:1 dcr. I think one of your plugs was cracked or you didn't get the plug wires on all the way. No way a plug swap makes that much difference.

 

Thanks for posting and you are right, dont believe everything you read. TR55s are best for NA

 

My DCR is a tad less than 8.5. Yours being that high is one that will benefit from the colder plug as you are pushing the limits of pump gas. Most cars here are running much less DCR than you and can use the TR55 without issue. I did check all plug boots and visibly inspected all plugs for cracks after removal. There was no detectable misfire while running the car. I have had a plug wire come off and there is no mistaking when you are down a cylinder.

I am by no means endorsing that a swap in plug type will make everyone's car a second faster in the 1/4 mile. Hell maybe if I go with TR5's I can hit some 9.50's! I am only pointing out a myth that has been spewed here that the TR__ is the plug to use for XXX setup.

 

I would think the plug gap would have more of an effect on anything than the actual heat range of the plug. I know you want to run as much plug gap as you can without blowing out the spark. Either way results like that are very impressive.

 

Yes they are impressive and should not be taken as a typical result. Apparently my car did not like TR6 with the tighter gap. I was trying to find the 11.0's that I knew my car was capable of, and honestly did not expect to find it by merely swapping the plugs. This was the first thing I wanted to try because it was a change from the previous setup. Needless to say I'm still baffled by what happened and kept the TR6's to try them next time I go to the track. Possibly there is a problem with them and it's just not visible to the naked eye. I will try another set I have and a few different gaps and see what the results are.

This was merely meant as an eye opener to anyone who may be running the wrong plug and gap b/c they read it on the internet. I would advise anyone speak to a reputable tuner about what should work for their setup versus typing the question in the search box and running whatever the results say.

 

Do you think the gapping played at big role?? hmmmm, Im gapped at .045 right now and I wonder if I gap mine to .055 will there be a difference??

 

Respectfully, there's something else going on here. What exactly, I dunno. Did you datalog the runs? Perhaps timing was being pulled for some reason on day 1 (high IAT's?) and not on day 2. I can tell you I have run TR6 plugs gapped at .035 and then NGK -8 plugs gapped at .026 on back-to-back N/A passes and both passes were within .05 sec and .5mph of each other. As long as the plugs aren't fouling, power loss from colder plugs / tighter gaps should be negligible at best.

 

I run the TR6's now gaped at .045. I had Iridium TR55's with a stock gap. I have honestly not noticed any power loss with the same setup. Running like 10.8-9ish : 1 CR.


In fact. I dynoed 414 on a dyno jet. Installed a 12 bolt rear and the TR6's and pulled on a mustang dyno and made 407. Tells me the plugs alone are not losing power in this kinda setup, infact probably gained a bit. Maybe you had a faulty plug or connection, but that is a pretty small gap for just sticking to NA. I would try regapping at +.010 and see how it feels.

 

Do you think adding at +.010 gap will make a difference?

 

The second 11.61 pass was at 55 degrees with a DA of 318. The 10.59 pass the next morning was at 52 degrees with a DA of -166. I don't think there was an IAT problem, but I did not log the passes. I was using the laptop for air/fuel only. The car was fully warmed up prior to both passes as well so there is no inconsistency there.

 

+ a million.. something else going on. I've personally seen the difference between the plugs in my own car and on several others. The power difference is really non existant.

 

I'm guessing that the air density between the night air and the morning air had a lot to do with the change in times. Plugs probably didn't make that much of a difference.

 

The DA Sunday morning was -861 and the car still went a 10.59@126, so I don't think the difference from Friday to Saturday was all that negligable. As soon as I can get to the track I'll do some testing to see if I can figure out exactly what happened. I'm thinking it may be in my best interest to bring at least two witnesses.

 

If you want an internet myth, don't use TR12 spark plugs or your floorpans will explode.

 

I'm trapping the in the low-mid 120s on my setup (same heads, compression, cam, intake, and headers as you) now with TR6 plugs @ .035"

Maybe I should switch to some TR5s @ .055" and shoot for 130mph. Then I'll put on some truck coils and go for the stock bottom end record.

Do you HONESTLY believe that a single heat range and .020" gap gave you your missing power back? You probably had a dead cylinder.

 

Exactly what I was thinking, or air/track conditions, or both!. Thats just to much MPH to pick up from changing plugs, assuming the first set was working as they should. Not that I dont appreciate you telling your story.

I personally run TR55s in my setup, and actually read through all the threads saying I needed TR6's first too.