Running FI - Colder plugs .. yes or no?
 

I've read through a bunch of threads regarding FI and the use of colder plugs, though I don't seem to find any consensus on the subject.

I just got a used 8 with a Greddy turbo and want to overhaul everything.

So the big question is, should I go with colder plugs in the leading and/or trailing holes? If so, what's the model # of the plugs I should get?

Thanks,
Mike

Stock trailing are fine . Most people fit colder Leading plugs although at low boost I can't say if it is necessary or not . I would err on the side of caution and go with 9 heat range plugs on the leading . I use BUR9EQPs and they work great but only last 3-4000 miles max.

I'm hoping 9k chimes in here. He was saying before that Steve suggested using the same plug all around. I can't remember off the top of my head. I'll have to search around for it if he doesn't see this thread

Awesome. Thanks for the feedback.

Is there any specific tipping point in terms of temperature or boost levels that necessitate a switch to a colder plug?

I wouldn't take anyone's word on what to use.

It depends on your set up and your tune.

I haven't personally read the stock 8 plugs yet but with the FD plugs with (1) ground strip, you can see (read) where you are as of heat.

With a nice clean plug, do a 1-3 gear run. Take the plug out and you will see a line on the ground strip. This line is created by the tip of the ground getting very hot. The heat transfers down the strip and makes a line when the heat stops. You want the line to be in the middle of the ground strip.

If the line is closer to the tip, the plug is to cold (or running very rich).

If the line is closer to the bottom, the plug is to hot and getting to the melting point (or running to learn).

There are general rules for a base. Your starting point.

8-10 psi or 75-100 shot of n20, you want to start with a step colder plug then stock. You still need to look at them as this is just a base. I had to run 2 steps colder on one project for a 100 shot.

It all depends on your set up and your tune.

Hope this helps you...

The car is running 8's and 10's now. It's only putting down about 260 at the wheels. Not sure on the boost levels, but I *THINK* I saw it peak at a hair over 11psi.

I just got the car and it isn't running at the moment, so I'll have to wait and see what the boost levels are. I'm a total n00b when it comes to FI, so when I replace the plugs, I don't want to go with stock ones if it's going to cause detonation.

What if I switched to stock plugs without altering the tune? or, what sort of tuning usually has to be done if I switch to stock plugs?

You are missing the point and taking it personal.

There are NO 2 set up's that are the same.

You cant just say, oh you are running 10 psi, you need a step colder plug. It all depends on what THEY have, not what you think. You cant tune a persons car over the Internet. Getting the right plug is part of the tunning process. You have no clue what is going on with what he has. So how could you possibly tell him exactly what plug to use (you cant).

You can tell him were to start (a base). But the final decision is what his car NEEDS not what you think it needs.

I could show you 3 different set ups with the exact engine pushing 10 psi. All 3 will have a different tune with different plugs. But will not tell you what else they have that effects the tune in order to pick the right plug.

I wasn't saying not to listen to anyone on a general base. I am saying not to listen to anyone for the final decision. He has to test to find out what he NEEDS. There is no way around it.

People will check the plugs at the end of a run at the track. Why, becuase it is that important. They are not going on the internet asking what plug they should use. They HAVE TO test and find out.

Just stop...and be quite. Don't talk anymore (unless you can somehow prove you have more credibility than Charles here, ie the amount of knowledge and personal experience he has into these cars)

To OP there should be a good sticky in the major horsepower section that gives good insight on the ins and outs for basic turbocharging but as always Charles gives the right answer. Under normal conditions with just a GReddy turbo there's no need to go one step colder but many people do just as a precaution. Especially when you start turning up the boost as the GReddy units develop a lot of heat when going outside their factory boost setting. Plus the one step colder plugs, BUR9EQP, from the trailing position of the 3rd gen RX-7, are much cheaper than the factory plugs for the leading position in the RX-8. The factory trailing position is more than enough for almost any turbo configuration this side of 400whp at least.

I guess you are smarter then the people that make the plugs. (NGK)

Read this and educate yourself.
http://www.ngksparkplugs.com/pdf/DYK_HeatRanges.pdf

Hmmm, sounds exactly what I was saying.

Here is another good read to educate yourself.
Choosing The Right Spark Plugs For Your Custom Engine - Car Craft Magazine

Just becuase (who ever) bulit the 13b many times or turboed it, does not mean you can tell someone what plug to use. Thats just being ignorant. You have to test.

Especially saying to put a colder plug in for a "precaution". That is the stupidest thing I ever heard. You obviously dont know how to tune or read plugs. Do you understand what the effects are running a colder plug when its not needed. How it effects the combustion and losses proformance, especially on a FI set up.

To the OP, do it right and test for what you need. It is not at all hard to do. You are the only one that can find the right plug to use.

Put a colder plug in as a pecaution, what a joke... This is what it looks like when you run a to cold for a plug. No, you dont want your plugs to look like this.
http://www.americanrcboats.com/howto...s/image004.jpg

I got tuned by Steve Kan and we ended up using the Trailing plugs on all four. We had some random issues that was solved by doing this while dyne tuning.

Thanks. I'll check out those links.

i ran oem plugs with 6lb's of boost never had a problem,i ran boosted for a year til i lost my job.
ray and eric from black halo installed my turbo, and with their assurance on the plugs i was able to drive back home to los angeles from arizona with no problems.

Based on the articles that were shared and everyone's feedback, 1 step colder seems to make sense given the bump in HP.

I'm going to stick with 8's and 10's until I find a reason not to. :)

3+ years boosted with a BNR upgraded wheel at 9psi ... somewhere in the 40,000 mile range at this point... stock plugs from day one.

Have considered trailing on both sides after hearing about the Kan tuning thing a couple months back but not all that compelled to jump into it.

I had the BURQU9's plugs in all 4 originally and kept getting misfiring at higher RPMs.

Put stock plugs in and was still getting misfiring, but at just the very top rpm.

Ended up having to gap the stock plugs to .30" and it solved my issues.... contrary to what 'most' would have thought.

It's true, you will have to find the right plug for YOUR setup.

Edit: Greddy kit w/ BNR upgrade & porting/polishing @ 13psi