I have the JWT ECU and I recently pulled my plugs and noticed every single one of them exhibited signs of running lean. They all had a whiteish color to them suggesting lots of heat. There was no little if any carbon buildup. Prior to the ECU, my plugs never exhibited signs of running lean. After looking at the dynos of JWT ECUs, you can see that the A/F holds around 14:1 across the whole board. A 14:1 A/F is great from 2000-5000rpms, but after that they should be dialing back to around to the mid to lower 13:1 range. The stock ECUs typically drop the A/F into the mid 12:1 range in the upper rpms.

I wish there was a way to push the A/F back after 5000rpms or so. What I've noticed with the ECU is that I'm definetely quicker, but the car is far more prone to heat soak. If I run on a hot motor, my ETs and MPHs can fall into the high 14.5s and 14.6s@95mph. If I let the motor cool off for 30-45 minutes then it's consistent 14.4s@98mph. My Max never use to be this touchy to heat. My belief is that that the lean A/F up top is introducing detonation (I can't hear anything) which in turn wakes up the knock sensor which then pushes back the ignition advance and then my car starts getting slow.

Do any of you guys notice this inconsistent performance with heat soak. Prior to the ECU, heat could account for .1 and 1mph, but not .3 and 3mph on the SAME DAY!!! I've noticed this on my last three outings to the track.

BTW, the TS ECUs exhibit the same lean upper rpm A/Fs.


Dave

 

could you add a little more fuel with an AFC?

 

My JWT for my 3-gen VE30DE is very sensitive in hot weather. But I can only get 91 octane around here. I believe they do the timing curves based on a 92-93 octane. I can adjust my base timing a bit to help but the 4-gen guys can't.
Maybe the afc like Jefferson said or up the fuel pressure just a tad?

 

Will running lean on a NA motor cause any damage to the pistons?

 

Yes. Especially when you are at WOT or getting on it pretty hard. You might break off the tip of the spark plug, nick a valve, crack a piston ring etc... It's not something you can allow to continue for long periods of time.

 

OT: But isn't the AFC used to lean out the AF mixture, not to richen it up.

 

Hmm, I have change my plugs recently at 60k and I didn't notice any whiteish color to them. Actually they were in great shape and could had been in use for alittle longer. With the jwt and mevi, I think I had about 7,000 on the plugs. I drive my car fairly hard sometimes so I hope others with the combo will chime in.

 

Also can you take pics of your spark plugs?

 

I'm going to be doing mine before too long. I'll let you know what they look like when I get'em out.

 

This post scared me so i just went out and pulled two plugs and they looked fine. Not white at all. I dont' have mevi though if that makes the difrence

 

I don't think I have looked at my plugs since JWT ECU install, but I haven't exhibited any of the problems you describe. My traps stay rock solid all day hot lapping or letting it rest for an hour.

JWT says they tune for 91 octane, they only have 91 available in California where they are located.

 

SAFC is to adjust A/F ratio, rich or lean, doesnt matter.

JWT is in El Cajon, CA: land of 91 octane, i would assume they tuned these in CA. If youre not sure, call them up and ask.

12.5:1-13:1 is optimum for NA performance, 11.5:1 for boost.

are these dynos you saw with the wideband plugged in before any cats? if the wideband is plugged into the tailpipe, for example, its gonna be inaccurate.

 

copper or plat?

 

I'd imagine that JWT programmed the ECU with a USIM-equipped maxima in mind. That being the case, would the extra 30hp or so up top be enough to cause a lean condition? If so I'd guess that cams would make it even worse.

 

NGK coppers with ~10K miles. As usual, it's hard to get a photograph to show what the object really looks like. In person, the electrode is an ashey-white-gray.






I'm assuming they were tailpipe sniffers like most guys use. I've seen 3 JWT ECU dynos and a few TS ECU dynos and they're all showing basically the same thing, a close to 14:1 ratio from 2000 till fuel cut. All the stock ECU dynos show the A/F richening up up quite a bit around 4500rpms with the ending ratio hovering in the mid 12:1 range which is pretty rich. I'm sure all the dynos I've seen are with tailpipe sniffers, but the data sure is suggesting these chip companies are going far more lean in the upper rpms than stock. Like you said, ideally we need to be seeing something like 13:1 in the upper rpms. Lean is good...to a point then you want to richening up as the cylinder temps rise. I'm a bite perplexed as to why JWT has made the A/F like they did.


Dave

 

This may be a dumb question, but would getting the 370cc's help out?

 

I don't notice too much of an ET and trap speed difference when hot lapping or letting the car cool down.

But there maybe something to this runnin lean at high rpm's and that is why race gas helps me out so much.

 

Is this on 40 degree days though? The coolest weather I've run in is ~60 degrees. I've hotlapped and ran back to back 14.4s, but that's when I able to go up and make another pass without having to wait at all. It seems the last three times I've been to the track my first pass is always a 14.6@95-96mph with a 2.2 60' and scalding hot engine. Then I let it cool for an hour and then it's 14.4s@98mph.

Dave

 

JWT didn't do such a great job with my ecu, either. Ben told me they would program for 11.5:1 (boosted), but what I got was more like 13.5:1 when dynoing with a tailpipe mounted O2 sensor. I bought a wideband O2 sensor and installed it in my test pipe because Ben told me that my dyno data was inaccurate. The wideband O2 sensor verified the dyno afr data. I have not confronted Ben with this yet because I really dislike dealing with him. I have since rectified the problem by increasing my base fuel pressure to about 40 psi at idle. Now I'm getting 12.5:1 to about 5500 rpm, then it makes a jump down to 11.5:1 and stays there to rev limit.

I have also noticed a sensitivity to warm weather, with light pinging during partial throttle acceleration at mid rpm with a heat soaked engine on hot days. The pinging goes away once I get past about 50% throttle and the afr jumps downward. I think the timing is set pretty aggressively at mid rpm and partial throttle.

 

Pulled two of my plugs today to compare. No white color at all. Just a nice light brown.

 

My electrode insulator is a nice brown too, but the ground electrode (where the spark from the electrode bridges to) was an ashy/whitesh/gray. The plug collar had some carbon buildup.


Dave

 

you need to put the wideband sensor in the downpipe, right after the turbo. you want it as close to all the cylinders as possible, the test pipe is too far away and wont be 100% accurate.

what brand of wideband did you buy? i only trust Horiba. K&Ns and a few others have proven themselves inaccurate to me.

 

How about going with a step colder plugs?