The 1947 - Present Chevrolet & GMC Truck Message Board Network - View Single Post - TF running hotter on highway than in-town.

1project2many · 09-07-2015, 09:04 PM

Camaros and 'Vettes have such a low coefficient of drag that the timing tables often run a bit more advanced than what works best for a larger vehicle. Engine MAP on the highway is about 54 kPa in the data screen you posted. I'd expect to see this value a little lower although with A/C running it's not too unreasonable for a truck. I'd also expect to see low to mid 40 in a Camaro at the same speed.

It only takes a few degrees additional timing to bring coolant and oil temperature up considerably and EGR, when operating, counters the effects of excess advance slightly. I'd say that the displayed advance is a bit high for your application. TBI trucks, with similar design heads, often end up around 30-34 deg advanced in OE cals and they use EGR. If too much timing is causing a problem then decreasing base timing 2-4 degrees using the distributor should provide some improvement.

Do you happen to have the four letter code off the original ecm or the chip? I'm just curious to see if I have a copy of that file here to look at.

Hopefully this issue is as simple as needing more openings in the shroud.

09-07-2015, 09:04 PM	#50
1project2many Registered User Join Date: Mar 2012 Location: Lakes Region NH Posts: 3,158	Re: TF running hotter on highway than in-town. Camaros and 'Vettes have such a low coefficient of drag that the timing tables often run a bit more advanced than what works best for a larger vehicle. Engine MAP on the highway is about 54 kPa in the data screen you posted. I'd expect to see this value a little lower although with A/C running it's not too unreasonable for a truck. I'd also expect to see low to mid 40 in a Camaro at the same speed. It only takes a few degrees additional timing to bring coolant and oil temperature up considerably and EGR, when operating, counters the effects of excess advance slightly. I'd say that the displayed advance is a bit high for your application. TBI trucks, with similar design heads, often end up around 30-34 deg advanced in OE cals and they use EGR. If too much timing is causing a problem then decreasing base timing 2-4 degrees using the distributor should provide some improvement. Do you happen to have the four letter code off the original ecm or the chip? I'm just curious to see if I have a copy of that file here to look at. Hopefully this issue is as simple as needing more openings in the shroud.