'Normal' EGT Temp for stock 6.5TD?

[dondandd]

Hello,
I'm fairly new to the 6.5l TD engine, and diesels in general. But I've owned my 97 Burb 6.5TD for a few months now. I've been preparing to tow with it, and plan to tow about 5500 lbs with it this weekend. In prep for that, I installed an EGT gauge last weekend. It's an Autometer gauge, rated up to 1600 deg. F, and I installed it pre-turbo by drilling and tapping the manifold thru the pass. wheel well (yes, with engine running).

Today so far has given my best indication of running temps, as I was pulling my 1500 lb trailer up some hills in Connecticut. It seems that on relatively flat ground, with minimal throttle to maintain about 50 mph, EGTs ran about 500 deg. F. Up slight inclines, they would rise to between 600-800 deg. F. However, pulling up so steep grades, and trying to maintain 50 mph could easily produce temps in the 1200-1300 def. F range!! This truck is essentially stock, minus the catalytic converter (because it was stolen, and I replaced it with a straight pipe for the moment).

Is this normal for a stock truck? Based on my reading of the forum and other sources, I thought that the max 'continuous' temps you could run were about 1250 deg. F. This has me wondering how the truck will do once I add another 4000 lbs behind it, and try to start lugging in up the hills in Pennsylvania. If I really need to keep the temps down in the 1250 range up hills, I wonder just how slow I will be forced to go.

If I had been completely naive to EGT temps in diesels, and gone with the assumption that "you can't damage a stock truck", would I be looking at disaster if kept on it up hills and let the temp climb to 1300, or maybe more??

Sorry for the long post. I'd appreciate any advice or personal experience. I'd like my first trip with the truck to have a happy ending, and not end with a tow truck!
Thanks,
Don.

[More Power]

In general, the EGT should stay within safe limits when running stock programming. But, now that you have an EGT gauge you'll see just how much the temp varies, and under what conditions. EGT can be used to help you manage the engine (for best power, fuel economy, engine temp).

When stock, the boost pressure will normally peak in 1800-2200 rpm range, then taper off as engine rpms climb above that. When boost is highest, EGT should remain well under control. You'll likely see higher exhaust temps at higher rpms and lower boost pressures. The stock 6.5 does well while towing at 2000-2200 rpm.

Assuming engine temperature remains OK, the 6.5 can handle a pre-turbo EGT of 1250 for the time it takes to pull the longest grade on any Interstate highway and with any rated trailer weight.

Jim

[dondandd]

Thanks very much Jim. I have a boost gauge, but haven't been able to install it yet. I was going to run my laptop and OBD reader so I could watch the intake tamperatures, and I was figuring I could watch MAP readings as well, but for some reason my laptop software shows a mass air flow reading (even though I don't have a MAF). Must be just a fluke in the software I guess?

But in the end, I'll keep an eye on that EGT and also pay attention to the RPMs I'm actually turning. But it sounds like if I can keep it in the 2000-2200 range, it'll be happy. I hadn't really payed too much attention to the RPMs I was turning while pulling the hills, but I will now and try to correlate that better with my EGT values.

And of course, once I get the boost gauge, I'll have one more piece of the puzzle.

Thanks again for your advice and insight... it's much appreciated.

Don.

[dondandd]

Well it was a fairly successful trip for the Suburban. On the two or three largest hills, I slowed from 70 down to 55, and once down to 50. For the most part I was able to maintain 60-65 up most hills.

Three things I noticed:
1)It doesn't burn completely clean while pulling up hills. It usually doesn't push black smoke, but more like a grayish smoke. You definitely notice it while pulling up hills, which I don't know if it's normal or not.
2)EGTs are almost impossible to keep under 1300 up hills. I let the temp stabilize up some hills, and it would easily hold about 1400. Once I wasn't paying attention and pegged the gage at 1600, and immediately let off to cool it back down. However it still begs the question, "why?" since it's completely stock (at least as far as I know).
3)It threw a code P1643 on the way home after stopping for diesel. It seems to be a code for the wait to start light circuit, and I'm hoping it's a fluke since the light seems to work fine.

All-in-all I was extremely glad I towed with the Suburban... especially since my off-road Jeep I was towing ended with tire damage and a no-start condition!

Don.

[More Power]

Either boost pressure is low or you have some sort of chip/program that's overfueling. These engines should smoke very little when stock. Do you have a boost gauge?

Jim

[Scooby]

I'll ask the ? too- WHERE'S THE BOOST ??!! Boost brings the EGT's down under load, so I suspect a lack of boost.

[dondandd]

I guess I really need to get that boost gauge installed and see what I'm getting. I had only had time to install the EGT gauge before the trip (and I still need to get an a-pillar mount, so my gauges aren't just zip tied to the pillar!). I kinda ran out of time to get the pillar mount and other gauges before the trip.

Am I correct that 7psi is stock boost... but I should expect some sort of taper pulling up hills?

Thanks again for the help. I'll try and get a boost reading soon and see if that shows a problem. I've had the connector give issues on the wastegate control solenoid, and that causes it to push quite a bit of smoke, but it also feels quite weak with no boost at all. And this weekend, it pulled strong... but I wonder if the ECU is pulling boost back under load, maybe due to intake temps or something. I'll wait and see what the gauge shows!
Don.

[More Power]

Am I correct that 7psi is stock boost... but I should expect some sort of taper pulling up hills?

Depends on engine RPM.

When stock, you'll see the max boost pressure (of anywhere between approximately 5-10 psi) at 1800-2200 rpm, then boost will decrease as engine rpm increases. This boost pressure management makes the stock 6.5 pull best at 2000-2200 rpm. Not coincidentally, this is the engine rpm range where the turbo is most efficient for both exhaust and air flow. The computer gradually pulls both fueling and boost pressure as engine rpm increases above about 2200.

Jim

[lfytsmith]

I pull a 6000lb TT with my truck. Last summer I would see 1250f preturbo and have to back off the throttle. I had already installed 3.5" exhaust, 97 H2O upgrade, and K&N filter. This year towing I added the good stuff, Heath diesel MAXe Torq and New chip, also put in new HO injectors since truck has over 150,000 miles. Now towing at 70 mph in overdrive with speed control set. Never seen temps over 950 and that was punching it from a stand still up a steep grade. I also see max boost of 14lbs and the truck runs great.

[dondandd]

Any change in fuel mileage with new ECU, in addition to the lower EGTs? I pulled about 10 mpg towing down from CT to PA. Obviously with my questions, it appears I may not be running at peak efficiency, so maybe I can pull better than 10 next time if I solve my problems.

Don.

[Mark Rinker]

Your MPG will stay about the same over time. Initially, it may drop as your FPG reaches an all time high, transferring more PSI to your right foot. (FPG=FunPerGallon) :D

[dondandd]

I certainly wouldn't mind an increase in my FPG!

[Scooby]

Put on a TurboMaster and Max-E-Torq and you will have a big increase in FPG !! Gotta have the boost gauge though!!

[RT]

I don't see a performance exhaust in your postings? I have a '93 with the mods you see in my signature. While its a mechanical pump engine, I have NEVER seen more than 1100* even pulling 8K up grades in 3rd gear with the pedal on the floor. The truck now has 249K on it and pulls a tool trailer and/or trash trailer every day. Never see more than 1000* daily. I would be concerned if I was seeing 1200*+++ RT

[dondandd]

Well, I am slightly concerned, being as you are correct, and this truck has absolutely no modifications to it yet. I'm going to try and get the boost gauge installed soon and go from there. Although my filter indicator hasn't popped yet... I may install a fresh filter and see if there is any change as well.

Don.

[RT]

Just like the old real estate saw: The 6.5 likes three things, Exhaust, exhaust and exhaust. IMHO, nothing reduces EGT's on a basically stock setup as well as a big free flowing system. RT

[dondandd]

Sorry to drag this thread back up from the depths of long-since-past, but my EGT's are still high... and I finally got a boost gage installed (although still currently zip tied to a-pillar wiring as my gage pod hasn't arrived quite yet).

What I've found is this... boost will spike to about 6-7 and drop to about 5 and hold during a moderate acceleration without towing anything. I tested on the highway at about 70 mph (unloaded, not towing), and I would get about 7 psi boost while pushing the gas about as far as it would go without causing the trans to downshift. But still, the EGTs have continued to jump way high while hauling up hills.

Now from the bit of reading I've done, and visiting a more current post on the board "lowish boost, highish egt... need advice", these boost levels seem to be about normal for the truck. Now don't feel like everyones previous advice has fallen on deaf ears... I'm still planning an exhaust upgrade. But I was hoping someone might chime in as to whether my "normal" boost and high EGT's make sense for any reason? It sounds to me like it is just over-fuelling for some reason, causing the high EGTs and the smoke while pulling up hills. Now I haven't checked boost yet while towing... so I'm not sure how it will react under that situation.

I'm not sure if an exhaust alone will help. Or if this is an indication that my FSD is beginning to malfunction. Or if my injectors are getting worn and leaking. Or something else is wrong.

Any thoughts or advice is appreciated. Sorry for the long winded post.

Don.

[john8662]

Your boost sounds about 2psi low.

This could be for several reasons, one of which is the gauge, but I'm going to believe the gauge because of the condition of smoke (indicating low boost as well).

Possible you have a leak. The upper intake plenum gasket can leak, or be broken. But more common is a leaky boot between the upper intake manifold plenum and the turbocharger itself. Sometimes a hole in the boot.

What is the condition of the air filter? This is important as well.

In my now RIP '95 Suburban with the stock engine and the older (GM-4 turbo) you have the better -8 turbo, it would make 9psi if I floored it in overdrive running 65MPH (2200 RPM) down the freeway. The transmission would NOT shift back down due to the programming with 4.10 gears. But on hard acceleration I would regularly see the 9psi until RPM's were near 3-3500. As MP mentiones this is part of the programming.

I know what you mean about the high EGT's in stock form, unfortunatly, this is nearly normal (not good either). If you want the engine to continue to live, keep the EGT's below 1200 at all times. Whatever it takes, slow down, shift down years and not lug the engine at times. I really saw a max of 1300 EGT, but its not too hard of pulls where I was pulling. If you want to kiss high EGT's goodbye, fix the boost and exhaust situation, and install an intercooler, night and day difference.

The exhaust will help some, the air filter change in the box you have won't net you any performance gain, it's pretty good as-is (best air box started in '97). The best after that is the complete AFE cold air intake kit, actually works, source: TJ !

The performance PCM from Heath does lower EGT's, oddly enough, but a more efficient overall program than stock.

I vote leaks in intake tract currently!

J

[MTTwister]

I did the home made version, and I would see 13# going over HomeStake pass in MT. Backed off the throttle a little, just in case. I should turn it down a touch ( currently 2100 ohms) . My understanding is that the ECM might pull boost when you need it most.
A search on "homemade Boost Fooler" should get you about 8 threads.

[More Power]

Keep your engine rpms at no more than 2200-2400 while pulling hardest. The limitations of the stock turbo contribute to higher EGT's. The stock turbine is a bottleneck for exhaust backpressure and its compressor becomes increasingly less efficient when moving more air at higher rpms. The factory turbo does a good enough job for most people at 1800-2400 rpm.

The Duramax has the same problem and for the same reasons, in that it will run cooler (EGT) at lower rpms. The highest EGT's I've seen with the stock Duramax was at 3000+rpm (a little over 1400 degrees). Run it at 2400 rpm or less, and the EGT's stay at about 1250 for as long as it takes to pull the longest grade with the biggest load - and with full pedal. :)

Jim

[dondandd]

Well, I know the upper intake gasket is good, because I just replaced it when I removed the upper intake to drill and tap for the boost gauge. I did not, however, check the condition of the hose very well. If those hoses are a known issue, I'll find a good quality silicone hose to replace it with. Or maybe just a careful inspection of the hose will show any holes.

The air filter looks good, but is not necessarily new. I will pick up a replacement in the next day or so, as it's something I've meant to do, but keep forgetting everytime I'm at the parts store.

When I pull up big hills with the trailer, I try to hit the hill at about 70-75, and can usually keep the trans in OD which keeps the RPMs somewhere around the 2k mark if I remember correctly. If I start to slow, I'll kick it out of OD at or just before hitting 65 mph, as the trans will drop the TC lockup back in while in 3rd, and that keeps the RPMs probably in that 2200-2400 range. But if the truck slows to around 63 mph or less, the TC lockup drops out, the RPMs jump to 2500 or a little more, and all bets are off.

But even in OD or 3rd with TC lockup, I can easily get the EGTs to climb above 1400 deg. I think I had mentioned once before, that on one hill, I had changed my focus from the EGTs to the road or the CB radio, and when I looked back, I was at nearly 1600 deg (and I let off the gas quick to get them to drop back down!). But it seems to like to pull well holding at about 1400 deg and about 65 mph in 3rd with TC lock. And that is with partial throttle. I never use a lot of throttle or else the EGT just skyrockets.

First thing... air filter. Then, maybe a boost fooler will help bump the PSI just a bit. FSD cooler is probably next biggest item, as I want to make sure that failure point is taken care of before it becomes a problem. Then I'll do the exhaust system.

Don.

[dondandd]

Update: I replaced the air filter, and had no noticeable change. I did get to put it thru a towing test, and here is the result:Towing approx. 5000lbs of trailer and car. While pulling at about 65mph, approx. 1800 rpm, boost would rise to no more than 4 psi when pushing the gas down about as far as it would go before downshifting. If I allowed it to downshift, and drop into TC lockup at about 65 mph, now at about 2400 rpm, I would still only see no more than 4-5 psi!

Is there a reason that the computer would be pulling boost down that far, or is this more likely a problem with the vacuum system? Is there any specification, at idle, for how much vacuum the pump should be pulling, and how much vacuum should be seen at the wastegate actuator itself? I will put a gauge on it this afternoon and see that it pulls, thinking maybe I've got a bad hose somewhere.

I did not try replacing the hose between the turbo and intake yet, as was suggested earlier in the post. I looked it over quick and didn't notice any rips, but I guess they could be hidden and only open up under boost.

Thanks for any other suggestions.
Don.

[damork]

dondandd,

Not sure of your total miles, but high exhaust temps can be an indication of late valve timing - has the timing chain ever been inspected/changed? I ran a performance chip in mine and replaced the timing chain with gears at 160k miles. Exhaust temp had inched up unloaded but came back down when the sloppy timing chain was replaced. Cruising 65 unloaded the pre-turbo exhaust temp was 550F, and it took some effort to get it to smoke, even with 180k on the injectors. I credit the injector life to good fuel, good filtration & Stanadyne Blue in every tank. I too never saw exhaust temps ever climb much above 1000-1100F, and when I did it was really doing everything I wanted it to, and with hardly any smoke.

[dondandd]

The truck has 150,000 miles on, and as far as I know, is completely original and never touched. I seem to remember reading about how to check chain slack on these engines... I'll do a quick search unless someone remembers the post and can point me there. I guess it can't hurt! Thanks for that thought... it's something I hadn't even considered yet.

Don.

[dondandd]

Problem solved it seems! I've had minor issues, with the wastegate solenoid not working... and it seemed to be solved by just wiggling the connector. But while I was working on the Burb, replacing the fuel filter, I realized it was acting more strange. So while the engine was running, I started jiggling wires. I had even tried cleaning the connector to no avail. And then while wiggling wires, the engine would stumble and miss which the solenoid was clicking on and off. But if I unplugged the solenoid and jiggled the wires, nothing would happen. So I used a volt meter and traced it to a bad power feed wire to the solenoid right at the connector. I actually just pulled, and wire ripped in two. So, soldered it to the terminal, and all seems well! Now I pull 6-7psi easy, and I even saw as high as 9 psi at one point pulling on the highway! This was a strange one, because it wasn't a total failure, but it finally started to act up enough that I could pin point it.
Thanks for everyones help with this issue!
Don.