Nigel Posted September 7, 2007 Share Posted September 7, 2007 I finally had a chance to wind out my Z through 3 and 4th gear up to 6K rpm with the new intercooler running 12psi, and I glanced down at my EGT gauge at one point to see the needle pointing at 1600F. That's the max the gauge goes to, so I don't know if it was higher than this. This is with 25 deg total timing and AFR's in the 11.5 to 12:1 range, so I was concerned to see the EGT's so high. I searched EGT and Turbo and came up with a few posts with others concerned about similarly high temps. But there doesn't seem to be a consensus on what's a safe or typical range for turbocharged L series motors. So how many people out there actually have an EGT gauge and what numbers are you seeing? Where do you have your probe placed? Is your exhaust manifold covered or wraped with any kind of insulation? What plugs are you running? What are your AFR's? What boost are you running? What is your total timing at that boost level? My specs for the record: EGT: 1600F (max gauge) Probe in manifold just before the turbo Exhaust manifold is covered by a heat blanket BKR7E plugs 11.5 to 12:1 AFR 12 psi 25deg advance Nigel '73 240ZT Quote Link to comment Share on other sites More sharing options...
MrFancypants Posted September 7, 2007 Share Posted September 7, 2007 I was always told that 1100-1200 degF is the safe zone for EGT. 1600 degF is a lot (boom). - Greg - Quote Link to comment Share on other sites More sharing options...
jgkurz Posted September 7, 2007 Share Posted September 7, 2007 I don't have an EGT gauge in my car so I can't speak for my setup but several other highly modded turbo L28 cars have reported 1600 degree EGT's or more to be common, especially on the dyno. I've also read that lowering your AFR's doesn't seem to make much impact on the temps, at least on the L28. I also understand that changing ignition timing doesn't solve the problem either. My guess is it has something to do with the cam profile. Possibly too much overlap. Water/Methanol injection is the only viable option I can think of that would make a real difference. Take a look at some posts by TimZ. That should be a good start. Quote Link to comment Share on other sites More sharing options...
TimZ Posted September 7, 2007 Share Posted September 7, 2007 What turbo are you running? Since changing to the GT42R, my EGTs seem to have gone up considerably - I'm now seeing temps on the order of 1800-1850 degF. With my old T64 o-trim turbo my EGTs were much cooler - more like 1500 degF. Since the turbo and exhaust were the only real difference between the two cases, it appears that the lower exhaust backpressure has something to do with it. It's possible that the decreased exhaust manifold pressure (it's now lower than the intake manifold pressure) is allowing some amount of "blow-through" during the overlap period, and perhaps this mixture is getting burned in the exhaust. As John mentioned, I was not able to get the temps down appreciably with timing or fuel (although the temps do go higher if I try to run much leaner than 11.5:1) This was pretty alarming to me at first, but the more people I talk to about this, the more it seems that this is common for very high output turbo engines. I recently dropped a valve seat, which was most likely directly attributable to the higher temps. I am currently replacing the valves and valve seats with pieces made with the higher temperatures in mind. I'll post more details on this a I work them out. Incidentally, my combustion chambers and pistons had been ceramic coated, and they both looked fine, aside from the damage done by the valve seat on #5. The ceramic coating had not flaked off, and appeared to be doing its job. The surfaces of both the pistons and the combustion chambers were smooth and not pitted at all. Quote Link to comment Share on other sites More sharing options...
Nigel Posted September 7, 2007 Author Share Posted September 7, 2007 EDIT: TimZ responded before I had a chance to reply... Thanks guys... I've read through a lot of the posts already though, and there doesn't seem to be a lot of real world data on just what kind of numbers one can expect to see with an L28 turbo. I've seen TimZ's posts, but I think his engine is a pretty extreme case. How about for a garden variety L28 Turbo? Maybe 1600F is pretty typical for these too? I don't know, so lets see some numbers from personal examples... Quote Link to comment Share on other sites More sharing options...
Nigel Posted September 7, 2007 Author Share Posted September 7, 2007 What turbo are you running? T3/T04B Turbo. I don't remember off hand all the specs other than I think it's a .63AR on the hot side and .7 something on the cold side. The engine is stock other than the exhaust ported on the head. I don't think there's anything too radical about my setup... Quote Link to comment Share on other sites More sharing options...
hughdogz Posted September 7, 2007 Share Posted September 7, 2007 Hey Nigel, I'm running the stock setup. The only mods to speak of is a CAI and a manual boost controller (stock J-pipe, no intercooler) Without the boost controller, my boost was only 5psi at the intake manifold. The highest EGT I remember seeing is ~1400 F. Cranked up the boost, and I still only get ~1400 F, even with the safety pop valve releasing...so that must be at around 9psi (I was more concerned at looking at the EGT gage than the boost gage). I should have the IC done by next week and hope to be boosting in the 10-11psi range... [Edit: I forgot to mention that I have the EGT probe tapped into the #6 runner, just a few inches from the head. I figured that since #5 & 6 run the hottest, this would be the best place to take readings. Next time, I'm tapping in the collector. See pics in the thread about EGT problems] Quote Link to comment Share on other sites More sharing options...
Nigel Posted September 7, 2007 Author Share Posted September 7, 2007 My EGT's were in the 1400 to 1500 range running 9psi pre-intercooler. A couple of years ago, I put a heat blanket over my exhaust manifold, and I noticed my EGTs went up by 50 to 75F. My EGT's are 1400F cruising at 75mph at ~15:1 AFR and 38deg advance. Quote Link to comment Share on other sites More sharing options...
spork Posted September 7, 2007 Share Posted September 7, 2007 I tune for my egt's on my car for around 1600 +-50 degrees. Mine's probably not what is considered an average build, but I still had egt's that high when I was running a milder setup. If you aren't trying to get the last ounce of power out of your setup, then tuning for a lower egt isn't a bad thing, it leaves room for error. As for timing, I have no idea where mine is set at as I'm in the middle of moving, everything is packed up, and my car has no transmission in it...lol Quote Link to comment Share on other sites More sharing options...
jgkurz Posted September 7, 2007 Share Posted September 7, 2007 Incidentally, my combustion chambers and pistons had been ceramic coated, and they both looked fine, aside from the damage done by the valve seat on #5. The ceramic coating had not flaked off, and appeared to be doing its job. The surfaces of both the pistons and the combustion chambers were smooth and not pitted at all. Tim, This is the most valuable information in this whole thread.... I've always thought ceramic coating was a great idea in theory but I couldn't really prove it was worth the cost and effort. I've always wondered how you could run so much boost and not detonate. I'm sure there are many other factors but this has to be one of them. Quote Link to comment Share on other sites More sharing options...
MONZTER Posted September 8, 2007 Share Posted September 8, 2007 Incidentally, my combustion chambers and pistons had been ceramic coated, and they both looked fine, aside from the damage done by the valve seat on #5. The ceramic coating had not flaked off, and appeared to be doing its job. The surfaces of both the pistons and the combustion chambers were smooth and not pitted at all. Hey Tim, Who did your ceramic coating, and which process was it. Thanks Jeff Quote Link to comment Share on other sites More sharing options...
510six Posted September 8, 2007 Share Posted September 8, 2007 This is a dattalog of my EGT`s http://www.theturboforums.com/smf/index.php?topic=93023.0 The EGT `s registered a highest temp of 1580 F and were within 40* of on another at full boost. The tempurature of the EGTs have dropped when timing was added. Quote Link to comment Share on other sites More sharing options...
TimZ Posted September 8, 2007 Share Posted September 8, 2007 Hey Tim,Who did your ceramic coating, and which process was it. Thanks Jeff I believe that it was a local place that my machinist uses - I'll have to check to see who it was. In the past, my experience had also been that EGTs would drop with added timing. In this case it did not seem to help. Quote Link to comment Share on other sites More sharing options...
slownrusty Posted September 8, 2007 Share Posted September 8, 2007 Incidentally, my combustion chambers and pistons had been ceramic coated, and they both looked fine, aside from the damage done by the valve seat on #5. The ceramic coating had not flaked off, and appeared to be doing its job. The surfaces of both the pistons and the combustion chambers were smooth and not pitted at all. Mine is also done Combustion chambers and pistons too... Yasin Quote Link to comment Share on other sites More sharing options...
Tony D Posted September 8, 2007 Share Posted September 8, 2007 I coated the cc and piston crowns at the stationary powerplant I worked at, because I had money in the budget and was curious. Decreased engine fuel requirements a noticable amount, and was still there, 8,000+ hours later. Matter of fact, I ran that engine for 24,000 hours without a valve job, and taking valve recession readings on the 1000 hour valve adjustments got the OEM interested in doing that kind of coating from the factory. Only drawback was there was no way to clean off anything deposited in the field, had to go to a walnut shell blaster (this was 1990's) but that probably wouldn't be an issue now, the stuff is readily available. Noticed some oil temperature reduction on some of the 'splashback immersion probes' in the oil system as well, so the heat was staying in the combustion chamber...on an automotive engine that would translate to quicker spool. In my application it translated to the wastegate being open more...hey, you know you're running a Turbo when the wastegate is 125mm, and the exhaust pipe is 24" before your catalyst, and 36" afterwards, going into the muffler! LOL Natural Gas Lean-Burn engine running 22:1 AFR with rock steady 1100 degree EGT, 24/7/365 @ 22 PSI Manifold Pressure, 10"Bore 10.5" Stroke, V16... Not necessarily applicable, but the N/A version of the same engine ran EGTs in the 800's. Quote Link to comment Share on other sites More sharing options...
speeder Posted September 10, 2007 Share Posted September 10, 2007 My L Motor EGTs run about 1650-1700 - 3.0L, T66, 7.8:1 compression, ~ 20PSI boost, ~ 430 whp. I have not been able to decrease this with fuel or timing adjustments. I was alarmed by this number until hearing of others' results... I concur with Tim and others here that think that big cam specs are responsible for the higher EGTs. My cam is 274 duration/.515 lift intake, 266/.490 exhaust, 114* lobe center. I'm no cam expert, but believe that even with the relatively low duration and wide lobe center, the net overlap of the bigger cam is greatly increased over stock, allowing more "blow-through" of unburned fuel. I don't see much discussion of probe position, but my probe is located at the turbine inlet about 6" away from the nearest exhaust valve. My old BAE manifold appears to have shorter runners than the L28 stocker. Sadly, I've not looked at EGTs until my engine build has progressed to this point - I would have been instructive to see what numbers the earlier, milder builds would have produced, and what changes occurred when the various mods were done. Quote Link to comment Share on other sites More sharing options...
510six Posted September 10, 2007 Share Posted September 10, 2007 http://www.techlinecoatings.com/introduction.html http://new.photos.yahoo.com/sss510six/album/576460762337492981 The coatings can`t hurt. I belive using 35% methanol as fuel has helped to prevent detonation and reduce EGT`s as well Quote Link to comment Share on other sites More sharing options...
Nigel Posted September 11, 2007 Author Share Posted September 11, 2007 I concur with Tim and others here that think that big cam specs are responsible for the higher EGTs. But, that's just it, I'm seeing 1600F with a stock cam... Quote Link to comment Share on other sites More sharing options...
TimZ Posted September 11, 2007 Share Posted September 11, 2007 But, that's just it, I'm seeing 1600F with a stock cam... Maybe you could dial in a bit more timing - what does your timing curve look like? I'm assuming you have a programmable? Quote Link to comment Share on other sites More sharing options...
Nigel Posted September 11, 2007 Author Share Posted September 11, 2007 I have an SDS EM3-6F, and I'm more or less following ScottieGNZ's recomendations for timing from way back when... So, I'm starting with a base timing of 20 deg at idle and ramping up to 38 deg by 2750 rpm. Scottie suggested pulling out a deg of timing for every pound of boost. I'm a little more aggressive at low boost and slightly more conservative at high boost. But like I said in my first post, at 12 pounds I'm at 25 deg total advance. I could bump it up more, but then which is worse, high EGT's or increased risk of detonation? Does no one else have an EGT gauge in their Z? Maybe these numbers are typical? I'm not doing anything out of the ordinary compared with the dozens of other L28 turbo's out there... Nigel Quote Link to comment Share on other sites More sharing options...
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