Exhaust temps way too high

razors4us

Member
Aug 15, 2021
39
22
Struggling with exhaust temp issues. I have my wideband over 3 feet from the turbo outlet and I have killed 5 sensors now in the last 2 months. Why??? I've verified timing, roughly 32⁰ cruising, 22⁰ idle and 9-10⁰ wot
I'm dialing in afr's but it just keeps killing sensors nonstop so it's been a struggle.

Could my cam timing be off? It seems to be VERY peppy at low to mid throttle and seems to fall off the further I roll into it, at 4 psi it just doesn't seem to have as much "oomph" as it should. It's in the high tens low 11s at wot when the sensor decides to read properly
 
  • Like
Reactions: Kizzlebizz

Chip

Member
Aug 20, 2021
36
94
What motor and combination is this? Need more info

I always ran the wideband 12" from the turbo

Any kind of air leak in front of the sensor will kill them. The sensor should not be after a gasket transition to the main exhaust.

If this is a turbo LS your exhaust temps are likely too high because you are running too LITTLE timing and too much fuel. There is also a possibility to hurt the motor running too rich just as too lean.

If you post your tune and it is either MS3, hptuners, or holley I can try to help you

TIMING POINTERS:

Cruise and low map

1600 rpm 30 degrees

1800 rpm 32 degrees

2000 rpm 34 degrees

2200 rpm 36 degrees

2400 and up rpm 38 degrees



Peak torque/mid throttle

I don't know what system you are using but his should be 15-20 degrees




Full throttle and anything slightly below boost to slightly above boost should be your normal NA timing. For some reason there is an urgency to turn the timing way down with a turbo everywhere. This will make the engine super lazy.

5500-6500 rpm 26 degrees on a turbo LS 90 map to 110 map or PROBABLY .56-.68g/cylinder airmass in hptuners



From full throttle your timing should blend down to hit 14 degrees at 14 psi - yes this even applies to pump gas.

You should not be running 9-10 degrees unless you are running 18-19 psi of boost, at which point this isn't a pump gas deal.



AFR POINTERS:

Most cammed LSes like to idle/return to idle at 14:1-13.5:1 AFR.

Cruise you should just run stoich or if you have E10 gas then 14.2-14.3

Anything mid throttle should blend to 13.5

Full throttle, yes even with the turbo, should blend to 12.5:1 once again everywhere from 90 map to 110 map. You do not need to go hugely rich at 2 psi.

Your AFR should blend down to 11.5:1 at 14 psi. If you are a super safety master you could blend to 11:1. Some combos just will not tolerate this though.

I would not blend to 10.5:1 unless running 20 psi, and that blend would only start above 14 psi.



SPARK PLUGS

Run the ngk tr6 at .025 gap for 14 psi and under. If you are "blowing out the spark" - which is a high rpm hesitation or shudder with lots of soot then you can try an even tighter gap.

Run the ngk br7ef at .020 gap for 15 psi and over



SCENARIOS FOR POOR HIGH RPM PERFORMANCE

If you take a 4.8/5.3/6.0 or an sbf 5.8 and you hit it with 4 psi of boost, richen it to 10.8 AFR, and cut the timing in half it may make less power than it would N/A with 12.5:1 AFR and full timing. I have seen this in cars I've tuned.

Once again, I don't know your combination, but watch Richard Holdener's youtube videos where he compares the same turbo on different size engines. He has a video where he runs the ebay gt45 on a 4.8 and a 454. The 4.8 makes more power. The smallest engine that can max out a turbo in its useable RPM range will have the least back pressure, the best power curve, the most controllable boost, and make the most power.

I see a lot of guys who want "ultimate boost response" put the gt45, the 7665, and the small a/r 7875s on 5.3s, 6.0s, and 351 fords and they are dogs up top - too little turbo for the engine.
 

razors4us

Member
Aug 15, 2021
39
22
Holy crap haha thank you so much for the info, I appreciate everyone's input!

It's a 2500hd crew cab Silverado. I'm running about 5 psi right now but I'd like to be around 14 ish. Right at the top of my map sensor.
SBE lq4. Never been opened, less than 50k miles.
Twin turbo- 72/68s with .96 housings
Bosch 210s
Br7s at .026
Wally 450
3" OD exhaust from the flanges back. dumps right in front of the passenger tire

Factory 4l80e on borrowed time.
Factory converter also on borrowed time.



I have up and forward headers on it as well and I'm sure they're not helping with the whole heat situation. It keeps wiping out the wideband sensor which I have mounted on the passenger bank approximately 3 feet from the downpipe flange on the turbo. The headers glow red hot every single time I go for a spirited drive. I actually almost burned the bastard to the ground because of it. A feed line to the turbo got too close to the header and it burst at 110 mph and sprayed all 6 quarts of oil onto a red hot turbo and header..... That was a fun fire to put out and now everything under my hood is half charcoaled.


Needless to say, I'm ready to park this thing for a while. It seems like every step forward I take - i get pushed back 2 steps in return.
 

Turbocharged400sbc

3800 & 4T80E > ALL
TCG Premium
Jun 16, 2007
32,538
15,846
hangover park IL
That seriously sounds like you're burning fuel and air in your exhaust instead of in the chamber. Either way retarded timing. Or another issue. You have no misfire counts/codes?

I've seen people that did wire harness work end up putting the coil connectors in the wrong locations so that coils were firing way too early and late...

I don't see a bent or nonsealing exhaust valve being able to let that much air and fuel into the exhaust...

Maybe it's because Buick V6's are so much cooler than v8s... but even after spirited driving in the TR with exhaust wrap the headers are absolutely nowhere near glowing.
 

razors4us

Member
Aug 15, 2021
39
22
That seriously sounds like you're burning fuel and air in your exhaust instead of in the chamber. Either way retarded timing. Or another issue. You have no misfire counts/codes?

I've seen people that did wire harness work end up putting the coil connectors in the wrong locations so that coils were firing way too early and late...

I don't see a bent or nonsealing exhaust valve being able to let that much air and fuel into the exhaust...

Maybe it's because Buick V6's are so much cooler than v8s... but even after spirited driving in the TR with exhaust wrap the headers are absolutely nowhere near glowing.
See that was my thoughts as well. I've verified timing twice now just to be sure. I asked a few people about cam timing being off and they said it would be very noticeable if I was a tooth off. I don't think I am either as it seems to be super responsive. I just don't get it. I have no wheel wells in the truck and I've also removed the rear hood seal and also too the top plastic piece off of the grille area and it STILL gets so fuckin hot under the hood that I'm afraid to leave the hood closed if I shut it off. I usually pop the hood and leave it latched half open when I shut it off to go inside anywhere. It has already warped the wire loom that I just replaced too.
 

Pro Stock John

LS is the best engine
TCG Premium
Sep 20, 2011
10,308
14,090
Chicago North Side
Chip's suggestions are in line with what I've heard, I have a single turbo 85/96 LM7 setup on E85. I've heard 26 ish timing at idle and 35-40 cruising (timing 32-36 for pump gas vs E).

Single Walbro, am I reading that right? Does not sound like enough. Pump 93 or E85?

I know of a car that had the cam installed retarded and it affected power.

Not sure what sort of power you expect from a truck like that and 5 psi on 10 timing... a modest gain but is that truck is like 4800 lbs well....

For timing some folks would say to start in the low teens on E85 and read plugs.
 

razors4us

Member
Aug 15, 2021
39
22
Truck is on 91 right now, but the 450 should be more than enough pump for 14psi I would imagine. The truck weighs in at like 5800lbs. I know it will never be a race truck. I'm just mainly worried about the exhaust temps being so high. Trying to narrow down the cause.... I'm still working out the fueling and timing. But the exhaust temp gets that hot under just normal driving as well. It's a little unnerving now after the fire. I'm literally panicking every single time I floor it now because I'm afraid something is going to ignite again. Hard to dial a truck In without going wide open lol
 

Mr_Roboto

Doing the jobs nobody wants to
TCG Premium
Feb 4, 2012
25,640
30,504
Nashotah, Wisconsin (AKA not Illinois)
Have you pulled any of your plugs yet. Don't rely 100% on your O2s being what you think they are if you're having problems. A set of sooty plugs could be a nice sanity check.

Those definitely seem like enough turbo to not be choking things out. I'd be concerned about backpressure potentially but not with a setup like that.
 
  • Like
Reactions: Turbocharged400sbc

Chip

Member
Aug 20, 2021
36
94
Ill just dump my honest opinion on you having tuned a fair number of turbo LSes, including a car that did drag week

Holy crap haha thank you so much for the info, I appreciate everyone's input!

It's a 2500hd crew cab Silverado. I'm running about 5 psi right now but I'd like to be around 14 ish. Right at the top of my map sensor.

Are you on the stock map? You are playing with fire and counting on the deep end of the table to overfuel.

Are you on the stock PCM? If you are on a 2bar map make sure you have the correct engine segment in hptuners. If you try to run the 3 bar OS with a 2 bar map all the scaling can be off.


SBE lq4. Never been opened, less than 50k miles.
Twin turbo- 72/68s with .96 housings

Does the engine have the stock cam? That will be a struggle to spool and not be laggy with a stock cam lq4.

Bosch 210s

Super overkill lol

Br7s at .026

If you are running these at low boost you can tighten the gap more. You would like the low end driveability better with tr6s

Wally 450
3" OD exhaust from the flanges back. dumps right in front of the passenger tire

Factory 4l80e on borrowed time.

Dont sell this trans short, but not running a shift kit like the hd2 is contributing to your issue

Factory converter also on borrowed time.

This is your biggest problem other than fuel and timing


I have up and forward headers on it as well and I'm sure they're not helping with the whole heat situation. It keeps wiping out the wideband sensor which I have mounted on the passenger bank approximately 3 feet from the downpipe flange on the turbo. The headers glow red hot every single time I go for a spirited drive. I actually almost burned the bastard to the ground because of it. A feed line to the turbo got too close to the header and it burst at 110 mph and sprayed all 6 quarts of oil onto a red hot turbo and header..... That was a fun fire to put out and now everything under my hood is half charcoaled.

Up and forward headers just straight up suck. Volume is way too big, kills spool, heat sucks. Stock flipped manifolds would be better.


Needless to say, I'm ready to park this thing for a while. It seems like every step forward I take - i get pushed back 2 steps in return.
 

b00sted

TCG Elite Member
TCG Premium
Oct 6, 2010
7,834
23,514
Have you actually verified timing with a timing light? The reluctor wheels can be off by a few degrees from the factory - so you may think you're commanding 9-10* at WOT(which is low to begin with), when in reality you may actually only be running 7-8 or so.

It definitely sounds like too little timing and possibly too much fuel.
 
  • Like
Reactions: Turbocharged400sbc

Pro Stock John

LS is the best engine
TCG Premium
Sep 20, 2011
10,308
14,090
Chicago North Side
I re-read your tuning advice Chip, great stuff.

I had help dealing with my overheating issue and one of the things my tuner buddy fixed was my timing tables. Now with a single Taurus fan I run at 189-193 coolant temps unless stuck in heavy slow traffic, then I creeped up to 204 but once the road opened up I hit 193 after 3 miles.
 

razors4us

Member
Aug 15, 2021
39
22
Yeah the truck has a stage 2 turbo cam from summit, it lights them off fairly well. The tune is definitely correct, it's a really good base tune from a very very well known tuner. It's a 2 bar is, speed density, yada yada. I'm just trying to work out fueling and exhaust temps lol. I've verified timing twice now, with a light, but I'm not against triple checking myself
 

Turbocharged400sbc

3800 & 4T80E > ALL
TCG Premium
Jun 16, 2007
32,538
15,846
hangover park IL
Double check the logic wire colors for each coil pack confirm that nothing got f***** around.
1 cylinder firing way retired and another firing so advanced so the mixture doesn't light would definitely pump enough air and fuel into the exhaust as well as flaming mixture outta a port.

Cylinder one might be firing properly at TDC.... but the others might not be. .. and I could totally see one pair of coils being Miss wired not being noticeable with a lumpy cam without undergoing a cylinder balance test
 

razors4us

Member
Aug 15, 2021
39
22
I'm going to have to ask the tuner if he minds if I let anyone look at the tune. Not that I care, but I don't want to step on my guys toes ya know? I don't think any wiring has gotten messed up for the coils as it's all factory wiring with an extension harness. I haven't really had the ambition to even start the truck in the last week let alone work on it lol. Thing pisses me off. The plugs have been in there for quite a while so I'm not exactly sure they'll be worth a shit to read.... I'll get them yanked this weekend and post them
 
Old Thread: Hello . There have been no replies in this thread for 90 days.
Content in this thread may no longer be relevant. Consider starting a new thread to get fresh replies.

Thread Info