wvumtnbkr Posted October 9, 2018 Report Share Posted October 9, 2018 Good Day! So, this past weekend at Pitt Race we saw temperatures of 240 Degree in our GM 3400. No changes since the last 2 races where we did not have this issue. We drained the water and added water wetter for day 2. No difference. Im kinda stumped why the temps would be 20+ degrees higher. The race at Nelson Ledges was just as hot as this race and we had no trouble keeping the temps down. The system is not using water and maintains pressure well (using a radiator pressure tester). Will an engine that runs lean create more heat? I have a seperate issue where the car will lean out and stumble under acceleration that seems heat related... Chicken or the egg? Anyway, any help is appreciated! Rob R. Quote Link to comment Share on other sites More sharing options...
mender Posted October 9, 2018 Report Share Posted October 9, 2018 Yes, lean adds to the engine temp because of several reasons: 1. Rich allows excess fuel to go through the engine which absorbs heat when it vapourizes. Alcohol engines run quite cool because of that cooling effect. 2. Lean mixtures don't burn as fast as stoichiometric and mess up the precise timing of the combustion event by delaying it. That can mean less power and a resultant energy loss out the exhaust, transferring heat to the cylinder walls, exhaust ports and valves. 3. That heat can be transferred to the next air/fuel mixture, again messing with the combustion event timing but in the opposite direction. In extreme conditions, the extra heat can cause preignition and detonation, which usually have catastrophic results. It's a balancing act with fuel mixture, and I ran my 3500 on the ragged edge at 13.5-13.8:1 at WOT. However, even the stock rad was able to keep up on days in the high '80s/mid '90s with water temp no more than 200 and oil temp about 240. The stumble means you're running very lean, make sure your fuel pressure is staying up and not causing your issue. 1 Quote Link to comment Share on other sites More sharing options...
wvumtnbkr Posted October 9, 2018 Author Report Share Posted October 9, 2018 2 hours ago, mender said: Yes, lean adds to the engine temp because of several reasons: 1. Rich allows excess fuel to go through the engine which absorbs heat when it vapourizes. Alcohol engines run quite cool because of that cooling effect. 2. Lean mixtures don't burn as fast as stoichiometric and mess up the precise timing of the combustion event by delaying it. That can mean less power and a resultant energy loss out the exhaust, transferring heat to the cylinder walls, exhaust ports and valves. 3. That heat can be transferred to the next air/fuel mixture, again messing with the combustion event timing but in the opposite direction. In extreme conditions, the extra heat can cause preignition and detonation, which usually have catastrophic results. It's a balancing act with fuel mixture, and I ran my 3500 on the ragged edge at 13.5-13.8:1 at WOT. However, even the stock rad was able to keep up on days in the high '80s/mid '90s with water temp no more than 200 and oil temp about 240. The stumble means you're running very lean, make sure your fuel pressure is staying up and not causing your issue. Yea, all possibilities are still on the table. I didnt have a fuel pressure gage connected. Just my AFR wideband. The wideband creeped up until it showed dashes (above 17:1).... Surprised the engine stayed together! Im thinking failing fuel pump that is affected by heat. I am ordering a new fuel pump, possibly a hydromat, and DEFINETLY a fuel pressure gage. Still doesnt solve my high temp issue... Or maybe it will? Who knows. Quote Link to comment Share on other sites More sharing options...
Fitsbain Posted October 9, 2018 Report Share Posted October 9, 2018 If memory serves, there were higher speeds at Nelson. More air, lower temps? Quote Link to comment Share on other sites More sharing options...
mender Posted October 9, 2018 Report Share Posted October 9, 2018 1 hour ago, wvumtnbkr said: Yea, all possibilities are still on the table. I didnt have a fuel pressure gage connected. Just my AFR wideband. The wideband creeped up until it showed dashes (above 17:1).... Surprised the engine stayed together! Im thinking failing fuel pump that is affected by heat. I am ordering a new fuel pump, possibly a hydromat, and DEFINETLY a fuel pressure gage. Still doesnt solve my high temp issue... Or maybe it will? Who knows. Having a slow increase in AFR indicates to me that your line pressure is steadily dropping, either from a failing fuel pump or a clogged fuel filter. Fix that and you'll probably have your normal temps back, plus the 15-20 hp that you were missing near the end of the race. Yes, the 60 degree GM V6s are tough and hold up surprisingly well despite very lean mixtures. Change your spark plugs and check the old ones for speckles on the ceramic. 2 Quote Link to comment Share on other sites More sharing options...
wvumtnbkr Posted October 9, 2018 Author Report Share Posted October 9, 2018 1 hour ago, Fitsbain said: If memory serves, there were higher speeds at Nelson. More air, lower temps? Good thought. However, it didnt happen at Gingerman either. Gingerman was a bit colder, but not like 30 degree colder. Quote Link to comment Share on other sites More sharing options...
Technical Advisory Committee Andrew D Johnson Posted October 9, 2018 Technical Advisory Committee Report Share Posted October 9, 2018 (edited) #ImWithMender - I think he's right. Edited October 9, 2018 by red0 1 Quote Link to comment Share on other sites More sharing options...
Technical Advisory Committee mcoppola Posted October 9, 2018 Technical Advisory Committee Report Share Posted October 9, 2018 I make the same comment (in my head) on most of @mender's posts. 1 Quote Link to comment Share on other sites More sharing options...
wvumtnbkr Posted October 9, 2018 Author Report Share Posted October 9, 2018 Yep. We don't always agree, but I listen (read) when he speaks (writes). Thanks @mender Quote Link to comment Share on other sites More sharing options...
mender Posted October 9, 2018 Report Share Posted October 9, 2018 (edited) 14 minutes ago, wvumtnbkr said: Thanks @mender My pleasure. Edited October 9, 2018 by mender Quote Link to comment Share on other sites More sharing options...
TiredBirds Posted October 10, 2018 Report Share Posted October 10, 2018 19 hours ago, mender said: Yes, lean adds to the engine temp because of several reasons: 1. Rich allows excess fuel to go through the engine which absorbs heat when it vapourizes. Alcohol engines run quite cool because of that cooling effect. 2. Lean mixtures don't burn as fast as stoichiometric and mess up the precise timing of the combustion event by delaying it. That can mean less power and a resultant energy loss out the exhaust, transferring heat to the cylinder walls, exhaust ports and valves. 3. That heat can be transferred to the next air/fuel mixture, again messing with the combustion event timing but in the opposite direction. In extreme conditions, the extra heat can cause preignition and detonation, which usually have catastrophic results. It's a balancing act with fuel mixture, and I ran my 3500 on the ragged edge at 13.5-13.8:1 at WOT. However, even the stock rad was able to keep up on days in the high '80s/mid '90s with water temp no more than 200 and oil temp about 240. The stumble means you're running very lean, make sure your fuel pressure is staying up and not causing your issue. What he said... I had a lean condition burn up a piston.. Quote Link to comment Share on other sites More sharing options...
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