Excessive EGT's
 

I having some difficulty in tuning. Probe before the turbo. Never see less than 700c. When im cruising its 900c+. Afr makes no real difference. But 12 idle and about 12.5 to 13.5 cruising.

13BT S4. Large ports. Power fc. Hybrid turbo.

Thoughts?

ignition zeroed in? how much advance? clogged cat?

What is you setup?

I think my wideband is out to lunch. On full decel, it only reads to 15 when it used to go all the way to 18. At idle, it shows 8.5 and the car runs smooth. Also at 8.5 it would be smoking like crazy. I've added more fuel to the maps and adjusted my injector lag times. I have more power {boost} and the EGT's are coming down. At a glance on the commander, at cruising speed (60kph) around 3k in 3rd it showed 38 degrees timing give or take.

Where do you guys run the sensor? I just put it in the stock bung hole. Heh, Bung Hole. I was thinking to move it down stream to the test pipe.

Timing zero'd in. Exhaust is a 3" RB downpipe to a test pipe, then an HKS catback.

BNR Stage 3 type turbo. 725/1000 ID injectors. Corksport FMIC. Power FC.

The car runs good, just has insane EGT's and low power.

What brand O2 controller are you using? Is it running an LSU4.2 sensor? If so you need to be way downstream, the free air calibration cell tends to breach and give funky readings if it's hosed.

Also, you might want to find an O2 controller that can drive an LSU4.9 sensor. I like the TechEdge units, as unsexy as they are to look at.

Thanks. AEM Analog Sensor with the LSU 4.2 I picked up a replacement sensor yesterday, Im going to put it in on the weekend way down stream. Probably after my presilencer Im putting together.

I think that combined with some grounding is my problem.

My egts preturbo were similar on my s5 based stage 4 w/ p-trim exhaust wheel. Around 1,000c on front rotor under lean cruise, slightly lower on rear straight runner and drop to 700s under throttle to climb up a bi to 800s.

From memory.

Same set up since 2001 with minor changes. Turbo exhaust housing has the same crack in turbine scroll slot since I had it made into hybrid without further cracking.

Car is primarily raced.

340rwhp@12psi, 380@14

I moved my Wideband down stream and installed a new sensor. It still reads erractically from time to time, but it seems to be working consistent. EGT's are reasonable under cruising and load now (doesnt seem to touch over 1000C under load).

My next problem is my boost is inconsistent. I've pressurized the entire system from turbo to engine to 20PSI and found no leaks, but it still is like .5 Bar .3 Bar. Sometimes 1 Bar. Sometimes .8 Bar. I have a 14psi wastegate on my hybrid. Also Have a Greddy Profec Spec B. I can max it out and it makes no difference. Cant really figure it out.

Thinking to swap out the whole turbo system and go with the turbonetics equivalant of a T04E.

Try a manual boost controller?:dunno:

I tried unhooking it completely (the wastegate) and it was still unco-operative. I must be missing a pre turbo exhaust leak. Its the only reasonable explanation. I had it out about 3 weeks ago driving the car and it boosted like it should to 1 bar all the way to 7k in every gear. I thought it had magically remedied itself. The next day it was back to random boosting.

Its a work in progress I guess haha.

check if the wastegate lever is binding in the bushing, or if the bushing is worn out. its better that it underboost instead of creeps. which is big issue on these BNR hybrids.

So, I took the time to take everything apart. I found that my main gasket was leaking, so I replaced that. I also found that the wastegate was worn out and leaking. It would not close all the way. I also checked over all my S5 turbo housings and they are all the same, worn and not able to close sufficently. the force of the wastegate actuator pulling on them lifts up one side.

So I pulled out my old Ported S4 housing and manifold, installed my EGT sensor in the port where the flapper door would go, and put it all together. The result is that it appears to be boosting properly within reason. I also noticed that my EGT's are WAY down with the open manifold versus the divided S5 manifold, which was picking up off the rear rotor. There is a considerable amount of MORE turbo lag, which I believe can be tuned out a little bit with the Power FC. Boost still drops at high RPM, but overall it appears to be working much better and happier.

The exhaust also sound different between the two turbo housings.

i see the same numbers on my S5 hybrid

I believe my next enemy is heat management. I get inconsistent response from the engine, and heat soaking. Its getting there though.

Today I removed my inlet pipe to the turbo to confirm my suspicions that my stainless intake duct plus HKS filter is a restriction. A big one. So I place a K&N filter straight on the turbo for the time being until I figure out an alternative. I got easier performance now, but still inconsistent boosting still and high EGTs

I made one car with bnr stage4, it would boost the same with or without the hose attached to the actuator. so basicly I think it was controlling boost just by pressing the gate open with backpressure in the manifold. the gates were ported alot and also the runners to the gate to prevent boostcreep.

what I hate about this setup is that now it runs about 1.2 bar top end, which is really enough, but midrange it holds only .8 bar, actually it would make more sense to have itt he other way around, as the turbo would be more efficeint making the 1.2 bar at mid range rpm instead of at peak power rpm. I think the only solution is to use a decent actuator with more spring force and bigger diameter and thus area membrane instead of this tiny BNR actuator.

I also replaced the WG bushing on this turbo with a stainless one, it could also be the lever is binding under some conditions, altough it boost consistent from one pull to the other?:scratch:

The EGT is mainly a combination of backpressure, lambda and timing. so if leading spark is working fine and you are running lambda <0.95 it should not have really high egt. I have seen about 900-950°C during cruise (closed loop at lambda 1) on a stock S5 TII before the sensor died.

Yeah when I cruise its about 700~800C with an AFR of about 12.5 to 13 when the wideband is workin.

My wastegate is aftermarket. I purchased a 10-14 psi adjustible wastegate. It made a difference over the stock one, but still doesnt really hold. With my profec maxed out it will give me one bar, then drop to .7ish by the time I hit 7000 rpm.

I honestly think my exhaust ports are way to large, causing the velocity to slow down. The exhaust just doesnt push as hard as it should.

Im going to experiment later and try to take some pressure readings, as well as combat heat management.

Sooner opening exh can cause increased egt as there is less expansion in the chamber. Sooner opening will always help spool, it sill altough decreases efficiency of the engine.

In an extreme case, let say of the exh opens just after tdc all the energy from the combustion will not be used to deliver work to the shaft but come directly in the exh port and thus be available to the turbine wheel.

You have an aftermarket actuator or complete external wastegate setup? I was talking about the bnr actuator which is like half the diameter diagram like stock.

The porting is pretty extreme compared to my pineapple racing ep3 template. The opening is a little earlier but the closing is much later. My theroy is because the ports are so large, you lose that velocity of exhaust.

I have an aftermarket external actuator. The turbo came with a factory S5 actuator. I simply went on ebay and bought an adjustable actuator with a t04b mount and modified it. My turbine housing is a stock s4 with a ported wastegate.