classicauto

iTrader: (3)

I've been battling a problem for 4 engines that I believe is related to an EGT imbalance.

I'm (currently) running a GT3574 in my FC. My main issue that I'm wanting to know about is causes for uneven EGT.

I can drive down the street and get even readings in the 1350F rangeat 15.0afr's 2800ish RPM. I can hold steady through the rev range and get even EGT's that are around 1600F+ beyond 5K to redline, no boost though.

In boost, say 5-8psi from 2500 to 4K I get a steady rise in both EGT's to about 1450ish and then the front rotor continues up while the rear stays fairly stable.

I have considered a few causes, one being fuel. My fuel system is RC750's and bosch 1600's that were purchased brand new, had a front rotor apex seal failure, had them flow tested and dead timed by paul yaw, implemented all corrections he gave (+1.5% on one secondary and all the dead times). Pump is an rx7.com nippondenso pump with a kennebell boostapump. Stock rails with a parrellel fuel system and aeromotive regulator.

My next probability would be uneven spray from my AI nozzle. Except I can turn it completely off an get the same results although both EGT's are higher (slightly) but still uneven.

My next would be that my manifold (greddy log) is getting a buildup at the front rotor while under boost. The manifold design would make it seem possible that the front section would collect more heat then the rear, but I'm not certain. My probes are 1" from the flange, so I'd presume I'm reading flame temp more then anything else, and I also would think that 1300F + 1300F doesn't necessairly mean it would be hotter then 1300F.

My FINAL idea would be something ignition related as I've found it affects EGT more then anything else. I have also been using the same trailing coil this entire time, but as far as that is concerned I'm not sure what I'd be looking for or how to confirm I'm getting spark when I need it (toggling correctly) when its wired to an E6X.....so fill me in.

SUMMATION - a few ideas on the causes, would like confirmation or more ideas as well as help diagnosing the trailing coils operation.

fritts

iTrader: (5)

Just because an injector is new does not mean for certain that it is flowing correctly. To start I would send the injectors out to be cleaned and flowed. Sounds like a secondary injector on the front rotor is flowing less than the rear.

classicauto

iTrader: (3)

I had them checked and tested. I had a failure last year that I related back to my fuel pump and wanted to check everything in the fuel system out. I sent them away in feburary for testing, and ran the car in march. They didn't have much down time between the test and the car running.

fritts

iTrader: (5)

If my injectors are dry or out of the car for more than a month or so I reflow them. What really scares me are the large secondaries even though they flow similar 1.5% of 1600 is 3% at 800. What's more interesting is when they don't flow the same from flow to flow.

classicauto

iTrader: (3)

Well they were only in the packagign for about 2.5 weeks between the test and the starting of the car. And what makes me lean away from them is the fact that I can get even readings throughout the rev range in vaccum. But in boost I get a difference.

Could that still be an injector issue?

Busted7

Swap the injectors and see if the lean condition moves to the rear. Kind of a real life flow test!

classicauto

iTrader: (3)

Excellent idea, I'll post back results!!

hondahater

iTrader: (2)

Rofl, no joke, good idea..

IAN

iTrader: (3)

Man your smart. What a perfect troubleshooting idea!

Classicauto,
By chance are you using the same side plates. Warpage of a side plates will introduce irregular heat patterns on the side plates and possible combustion chamber. But I doubt that would be something that you could pick up with the egt.


Did you try your spare coils?

Are you using the same LIM and UIM? By some strange oddity would one of the runners be slightly plugged and not getting as much air?

This is puzzling.

I forgot to check but do you have the diffusers installed in the fuel injector holes? Both facing the same direction? (another not an issue since this issue follows all of your engines...........uhmm.)


Ian

classicauto

iTrader: (3)

Ian good ideas!

Sideplates for this engine are different from the last two (1/2 bridge then, streetport now) actually the entire keg is different then vs. now.

Intake manis are the same, great possibility there!

Nothing on the coils yet.

I have diffusers installed and facing the same way



I ahve a new suspect though. The probes. Last night I was logging some freereving neutral to inspect the log for anomalies in the RPM recording and noticed that at 7k (which I've taken this engien to.....mmm three or four times only at this point) my EGT's were WILD, but equal. After that, cruising down the road the rear was lower then before at the same cruising. Then during idle, the rear would stay at 1300F for about a minute, then plumet down to the bottom. I wonder if the rear is just reacting a TONNE slower then the front?

But this weekend I will be swapping the injectors and doing more tests.

Dudemaaanownsanrx7

iTrader: (23)

i've heard that one of the rotors usually runs a little leaner then the other thats on the fd, i dont know about the FC. I believe it has to do with the runners not quite being equal. What ECU are running? Can you add a couple MS extra fuel on the front rotor? Do you have afr readings or just EGT's?

classicauto

iTrader: (3)

I've tried trimming either rotor up 12%, and either rotor down12% and don't get much EGT change. + or - 80F at the most. The difference I'm seeing under boost breifly is 150+

EDIT: I'm running an E6X. And yes I'm reading AFR's also. If I make a + trim change to the front or rear primary, I *can* see it get richer on the WB, but EGT's don't dip that much. Same as if I make a - change, it gets slightly leaner, but the EGT's don't increase that much. And I've made a 12% chagne in both idrections on both rotors just to see what would happen.

I'll swap secondaries and try some boost out and let you know

turbine

iTrader: (1)

do you know anyone else who has ran dual EGTs on a log style mani?
it would be interesting to hear what there readings are.

i can see there could be the potential for slightly different readings with that mani.

i thought about running dual EGTs but it would drive me up the wall if they were not spot on even. the more gauges i have the more i tend to worry.

classicauto

iTrader: (3)

Thats part of the reason for this thread, as I don't know anyone with a log mani who's running dual EGT's. I hoped someone else may chime in with their readings.

Turblown

iTrader: (12)

Try swapping the tc leads, then the t/cs themself. Are you monitoring digitally or using a mechanical gauge? I've never ran dual tcs on a log manifold myself, too bad your so far away or I would let you borrow a manifold to see...

BLUE TII

iTrader: (9)

I would suspect trailing spark problem as EGTs are same in vacuum, but vary in boost.

I suppose it could be a slow EGT probe as well since you are only under boost for short periods (I pressume you haven't tried 4th gear brake boosting).

On my dual set up on modded stock S5 divided turbo manifold it reads the opposite of what you have. Slightly different EGTs in cruise due to manifold/turbo design and then even under boost.

classicauto

iTrader: (3)

1revvin7 - Good suggestion, thats next on the list. The thermocouplers are analog, its the Pineapple Racing dual EGT setup.

BlueTII - Thanks for the info.


I've swapped injectors front to rear and test drove. No dice. I still have the exact same readings as before. Leads me to believe its the probes....but I'm going to try different coil packs tonite and pull the plugs for a read, then I'll post some pics of them for the more experienced eyes.

Dudemaaanownsanrx7

iTrader: (23)

i don't know how the manifold is setup and where the probes are located, is it possible that somehow the heat is dissipated better on the rear rotor probe? is one probe closer to the wastegate or dowpipe section? just an idea. have you contacted pineapple and asked if this is a common result with that setup? maybe its normal

classicauto

iTrader: (3)

There's some shots of the manifold and probe setup.

You can see why the heat dissipation or build up/manifold design theory is valid for sure...but at the same time I would think my probes are so close to the engine that the flame temp is being read more so then anything else.....I've contacted Pineapple about it but they say it shouldn't be. I also asked about getting new probes but they've never gotten back to me. Seems you can't give away money on some days....

Busted7

Another test would to put both probes in hot water and watch the readings as to max temp and differential if any. Of course they should be equal but most things arent.

Also from what ive seen is for some reason front and back intake air temps are not usualy the same. So ive tried ti isolate the effect of heat on the lim. by using shields and insulation.

Hope you find it soon!

afgmoto1978

iTrader: (6)

Better off using a propane torch instead, higher temperature check for better resolution.

classicauto

iTrader: (3)

Another good test! I was thinking I would yoink both probes, clip them together and flip the propane torch on both tips and watch the gauge. Water would perhaps be more even. The only down fall to the water test would be that my gauge's lowest reading is 1000*F.

I do have 2 layers of that sticky fiberglass/aluminum shielding on the LIM, but certainly nothing as hardcore as the one's on your FD. I might have to go a little more ***** to the wall in the future.

For tonight I'll do my ignition changes, and hopefully reading the plugs will give some answers. I'll have some info for that tomorrow.

:EDIT: Lol @ propane torch suggestion. Posted at the same time

Busted7

I wasn't thinking about the start point of the egt probes Dha! The torch is they way! Anyway good lucl!

88rxn/a

iTrader: (6)

im running just about the EXACT (matter of fact..i used your pics for placement of the probes!) same setup as you classic ...IE placement of probes and the "log" mani.
car SHOULD be running this weekend or withn a few weeks...ill see what i come up with and post my results....

The Griffin

High heat outside of the manifold on the probe wiring also affect readings. Swapping the probes is probably the best first troubleshooting idea to see the temp diff. follows the probes and rerouting/heat shielding the wiring from high radiant heat would be a good idea also.
IIRC you're using an e6x.Doesn't the e6x have an injector trim function? If it's not a egt gauge issue and if the e6x has the trim function ,trim out the lean egt diff with the standalone ecu.