Dudemaaanownsanrx7

iTrader: (23)

i think he said he already adjusted the injectors both up and down and it leaned out or richened the overall mixture but didnt have an effect on the probe reading differently.

Based on the pics it doesnt seem like it would vary, and almost seems like if anything the front rotor would be slightly cooler...unless somehow the rear port adds heat to the front cause it kinda Y's together there....

i agree switching the probes around is a good idea to try first, but maybe try the propane thing while they are out.

if these tests are inconclusive maybe just plug both holes and put 1 probe in so u wont be as paranoid lol

Howard Coleman

iTrader: (6)

i have run/logged digital EGTs for four seasons. my probes are within an inch of the exhaust flange at the motor. i had a slight bias toward the front being hotter... about 60 degrees. i richened it a tad and all is fine.

i suspect your manifold. if i understand, you have close EGTs until you get into boost and then things widen w the front rotor being hotter. since the flange is much closer to the exhaust port than the rear, i believe pressure is building at your motor's exhaust port.

harmonics could be a factor.... just as their is on the intake side. while many run this type of manifold few actually measure both EGTs and i suspect if they did manifold designs would change.

hc

classicauto

iTrader: (3)

Hey guys, thanks for the great suggestions, I beleive manifold design is playing a role, but I'll fill you in on what I found and tried last night.

I inspected my trailing coil and found the plug lead/post on the T1 coil pack had a slight bit of nastyness in it. Tried to get a decent pic but failed. It wasn't *bad* but it wasn't immaculately clean like T2 was. I swapped the pack for another that works and has clean leads.

I then pulled my plugs for a reading (will post pics, have to grab my camera at lunch) and found that the front is DEFINETLY leaner then the rear. Now, I have swapped injectors (all, not just the secondaries) front to rear, so another plug reading after some miles will tell me if the condition has shifted along with the injectors. But I was certainly surprised to find such a clearly illustrated bias what with new, cleaned and flow tested injectors and all. Not to mention, inputted all the dead times given by Mr. Yaw and also a small correction that he also advised me to make (+1.5%) the secondary which had lived in the front rotors' intake track until a couple days ago. Meanign that the front rotor had +1.5% trim added already. Apparently one secondary lagged a tad and that's what he told me to do to equalize them.

Anyways, I fired it up and took it for a drive. After it had warmed up I did a few small boost runs (7psi up to 4Krpm in 4th gear, taking lots of time for temp to build on the probes) and found ====== even EGT's under boost. Within 50-70F.

I wanted to swap the probes, but after finding the few minor gremlins on the trailing coil I thought it would be best to change only one thing at a time. And thats where I'm at now.

My biggest question would be, how could lack of ignition/slight mis firing cause the differential between front and rear (at least, it would seem it was the cause....) and yet the plugs be so different?

I'm very interested to pull them after a while and see what they look like with the injectors now totally reversed. I wonder if its' perhaps a flow charateristic of the stock manifolds? Front gets more air for some reason?

Still slightly baffled, will post pics of the plugs shortly.

Dudemaaanownsanrx7

iTrader: (23)

according to chucks notes one chamber does get more air. i'll look again to see which one it was. but the trim adjustment should have equalized the egt's.

If you have a slight miss i can see how the EGT's would go up at the probe, because the mixture isnt completely burning in the combution chamber, there is some excess fuel that is now burning in the manifold. right near that front probe albeit. or maybe the slight corrosion caused a little delay in the plug firing causing the same results i just mentioned.

Busted7

Yes if you get any unburned fuel in the exhaust it can burn like a blow torch, and depending were the probe is it will read high or low.

I was running a blower 13b on meth with the timing way retarded and was getting 875 deg at the probe but the headers were glowing light yellow about 1800 deg.

classicauto

iTrader: (3)

Yeah, I would think so too, but perhaps the adjustments weren't coarse enough to cause much change? I did notice change after trimming either side up or down, but it was in the <100F range, the probes were showing 200F+ difference under boost.

Makes sense!!


Plugs. Now, these plugs have roughly 7,500kms on them and have been mostly highway, low RPM driven. I ran no more then 10psi the few runs I did through the dragon, but there's mostly vaccum sub 4Krpm driving on them with boost spurts while testing EGT's etc. Also important to note as its' tough to see in the pics, but the front leading's center electrode had been rounded more then the other plugs....



Trailing coil post that was good. The "bad" one I couldn't get a decent pic of, but it had light brownish flim on an area from

classicauto

iTrader: (3)

Dunno what happened but part that was cut off, should read:

Trailing coil post that was good. The "bad" one I couldn't get a decent pic of, but it had light brownish flim on an area from what would be 9 oclock to 11oclock. Nothing I would consider terible, but didn't look like the one in the picture thats for sure.





So if you guys have any insight on my plug reading, feel free to speak up

Dudemaaanownsanrx7

iTrader: (23)

i dont think the plugs look too bad but im not an expert at that and its kind of hard to have an opinion from just the pic... they definitely dont have carbon buildup..

i recently started running NGK B9EGV's and i prefer them, they dont seem to foul out as easy and have better starting IMO. Plus they are a little cheaper. i get them from o'reilly's.

Rally car guys often run an antilag system basically what it does is retards the timing and does some other adjustments when you let of the gas to cause the mixture to combust in the turbo housing to keep the turbo spooling when they lift their foot off the gas. thats todays fun fact for the day.

Dudemaaanownsanrx7

iTrader: (23)

oh and apparently its the rear rotor that generally runs leaner and hotter due to the manifold's runner length differences.

Barry Bordes

Classic,

My RE switches who is hottest from idle, to cruise, to..... wait I can't boost yet!

The leadings should have exactly twice the wear of the trailings because they fire twice as much. It looks like from the picture that the rear leading plug is just as wore as the front. The plugs look nice to me with the rears a little richer.

Barry

IAN

iTrader: (3)

Those plugs look fine to me too. You should have seen my plugs classic after our 6500km cruise. They were awfull.

After reading all of your posts and some peoples input I am wondering about this unequal length runners on our log manifolds. I would assume that with the location of your T/C's and underboost you wouldn't see much of a difference.

Seems like you've spent alot of time troubleshooting this problem.

hairyhoover

Could slightly un even compression causing this?

classicauto

iTrader: (3)

Yes thats a possibility.


However, I've come to find after another plug reading that thigns seem to have evened out now. But I think I should do another test given that engine conditions changed so much during the life of those plugs. We had dyno tuned the engine and ran into seperate issues (trigger noise in the Haltech) and I've chased my tail for weeks on this car.

But, on the new plugs the difference between front and rear plugs was almost non existent and certainly not as obvious as the photo above (which really isn't too bad)

To note however: After sorting the trigger issue in the car (gains and filters needed copious amounts of tweaking) I've been able to run some more boost and watch EGT's. At 13psi ~5500rpm I am seeing 1550front and 1500 rear while spraying water or not. I believe the EGT imbalance to be solely related to manifold design in this case, so chalk it up to that.

I'll be swapping over to the genuine A-Spec divided SS manifold over the winter, so we'll see next year exactly what the difference in performance, and EGT stability between these two is.