Magnum cooling
- Thread starter Evan Dutch
- Start date
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TT5.9mag
Two atmospheres are better than one
You should have about 48 degrees of timing in it at cruise. That alone will bring the temp down considerably.
Evan Dutch
Well-Known Member
Yeah it’s about 25 degrees at cruise (2400-2800rpm) which is about 55-65mph.
I’ll mess with the timing table to try and feed more timing into it at that range. Manifold pressure is -4.0 to -4.5 at that range also
Evan Dutch
Well-Known Member
Won’t it ping with 40-50 degrees of timing at cruise? That seems like alot?
Newbomb Turk
Well-Known Member
Not with that little load on it. It’s close to the same as NA in this case.
The cylinder isn’t packed tight with fuel and air. The molecules are a long way apart compared to full boost or full throttle NA.
So it takes longer to get the burn complete.
With the timing retarded like you have it, the burn still gets completed but it’s so late that it’s finishing in the pier and out into the exhaust.
That slow, lazy burn generates an incredible amount of heat late in the cycle.
It drives coolant temperatures through the roof.
Just like you are experiencing.
That’s why 99% of NA engines should be using vacuum advance. It’s the same thing.
TT5.9mag
Two atmospheres are better than one
Nope. That’s where all of your fuel mileage comes from also. Lean and lots of timing. Pinging will happen under load when cylinder pressure is high and VE is up. Mostly at or around peak torque.
TT5.9mag
Two atmospheres are better than one
you have to watch the load as well. You don’t want a bunch of timing in it when the load is high. But cruising you want a bunch. That’s why 3D timing tables are so awesome. Watch your timing on the graph in real time while cruising and keep hitting the up arrow and it’ll cool off, run better, get better mileage, and the vacuum will increase.
Evan Dutch
Well-Known Member
Okay, the terminator software does have 3D timing tables. I’ve only been using the 2D table up until now. I’ll need to have my laptop up so I can see the live table while I’m cruising on the highway.
How do I determine how much is too much for timing at cruise?
Newbomb Turk
Well-Known Member
When you start getting a tiny surge stop there and take a couple out. Test again. I'm assuming you'll use a flat road to test. As flat as you can get anyway.
TT5.9mag
Two atmospheres are better than one
What he ^^^ said. I would also urge you to find a local professional tuner and have a custom tune done. You can get in the weeds pretty quick.
If you do have any type of under drive pulleys on there, they need to go. What is the size ratio between your crank and water pump pulleys? You want around 1.2:1, maybe a little more with forced induction.
I had my pulleys made, 7.00’’ crank & 5.875’’ water pump. Had a similar issue to yours few years ago, used those pulleys with a FlowKooler water pump (vane impeller type) big radiator, big block style 160deg thermostat & went back to a mechanical fan. Solved it. You want good airflow and water flow at low engine speeds.
I had my pulleys made, 7.00’’ crank & 5.875’’ water pump. Had a similar issue to yours few years ago, used those pulleys with a FlowKooler water pump (vane impeller type) big radiator, big block style 160deg thermostat & went back to a mechanical fan. Solved it. You want good airflow and water flow at low engine speeds.
Fuel is still burning as it travels through the exhaust port, in turn roasting the water jacket.
This is usually when you see headers start to glow red as well - retarded timing.
Evan Dutch
Well-Known Member
The crank pulley I’m using is the one supplied with the supercharger. It’s the same size or just slightly larger than the factory magnum crank pulley. The water pump pulley I’m using is what comes stock on a magnum water pump
Newbomb Turk
Well-Known Member
As long as the crank pulley is the same diameter as the water pump pulley you're ok. If the water pump pulley is smaller than the crank pulley that's great. Depending on your rpm and what water pump you have, up to 20% over driven is great.
Under no circumstances should the water pump pulley be bigger than the crank pulley, with one exception. If the rpm is high enough you can run into cavitation and that's bad. If you contact Flowkooler or Milodon they can tell you at what rpm the pump will cavitate.
Then it's simple math to figure out how fast the pump is turning. If your max engine speed is say, 8000 rpm and the pump is 20% overdriven the pump rpm will be 9600. That's an example and I have no idea what your max rpm is or how many rpm the water pump can turn.
One other thing to remember about water pump speed. You can get to the point where you blow the belt off. This is much easier with a V belt arrangement but a serpentine belt will come off if you over speed it far enough. Also, I know you don't run a mechanical fan but if you were you'd need to consider fan speed as well. An exploding fan is bad news.
Under no circumstances should the water pump pulley be bigger than the crank pulley, with one exception. If the rpm is high enough you can run into cavitation and that's bad. If you contact Flowkooler or Milodon they can tell you at what rpm the pump will cavitate.
Then it's simple math to figure out how fast the pump is turning. If your max engine speed is say, 8000 rpm and the pump is 20% overdriven the pump rpm will be 9600. That's an example and I have no idea what your max rpm is or how many rpm the water pump can turn.
One other thing to remember about water pump speed. You can get to the point where you blow the belt off. This is much easier with a V belt arrangement but a serpentine belt will come off if you over speed it far enough. Also, I know you don't run a mechanical fan but if you were you'd need to consider fan speed as well. An exploding fan is bad news.
Why I ask about the size & ratio of the pulleys is that this is really what solved the issue. That and the pump.
The big radiator and other upgrades were already there or added on at the time. Wouldn’t hurt to measure them up and work out the ratio you have.
Evan Dutch
Well-Known Member
The more I read into it the more I feel that the timing is the main culprit. That would explain why my underhood temps are so hot.
The water pump pulley is smaller than my crank pulley. I’d like to try and adjust the timing before I spend the money on a flow cooler water pump
Evan Dutch
Well-Known Member
I could try that, I know that the crank pulley is bigger than the water pump pulley, just not sure about the exact measurement
Newbomb Turk
Well-Known Member
Yup, work on your timing. The pump isn’t under driven so that’s not the issue.
TT5.9mag
Two atmospheres are better than one
You can pull a lot of temperature out of an engine with timing. Conversely you can make a marginal cooling system overheat quickly with retarded timing. The stock magnum pulleys and water pump are sufficient to cool what you have. I’ve used them up to ~650hp. You need a good rad and good airflow AND the timing has to be sorted out. Start there.
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