^^ Old 86,thanks!

 

The crank case pressure sensor is brilliant, nice job.

 

The water press sensor info is interesting. Before,I hadn't given much thought about what would be going on in the cooling system. Just figured it'd get to whatever psi the cap was rated for and basically stay there. With the sensor in the rad, same tank as the cap and suction side for the WP,the press was all over the place,0-15 psi,13psi rated cap. Yesterday I moved the sensor to the intake thinking I'd get a more consistent psi reading. Driving around,its anywhere between 4-20 psi,but on a pull shoots up to 64 psi.

 

That's crazy. I could see it being different on the hot/cold sides of the rad, and at rpm, but 64 psi seems excessive. What are your thoughts on that?

 

Capizzi talked about this monitoring the SBE Lsx stuff. He explained that pressure would normally stabilize once up off idle.
If it was lifting the head the log would show bunches of pressure spikes above that base pressure.

So is it a constant 64 psi. If so what about if you reduce smoothing?

 

I only did a few short pulls last night,90 mph, need to do a longer one just for info. My though is that it's normal, I guess. Makes sense that if you spin the WP speed up,the water can't get out of the block fast enough. I didn't expect to see 65 psi though for sure. The press rise was nice a smooth with RPM. No reason to think I have a HG issue, LOL,but maybe!

 

Hit 59 psi tonight. Crazy.

 

I've heard that the heater core circuit can hit over 100psi on cold starts and was why later cars used a restrictor inline to the core. Never tested myself to find out for sure.

 

I don't know what to think of it. I keep thinking the sensor info is wrong,but have one tied to the trans for line pressure and it follows the mechanical gauge that's been in the truck exactly. Might try a mech gauge to verify the water pressure. Thinking that if the motor was pushing boost, the pressure rise wouldn't be so smooth and follow engine RPM like it does.

 

I forgot, Capizzi has an electric water pump. So his doesnt rise with rpm.
But he stated specifically that it would have high frequency pressure spikes if the heads lift.
It is weird though. Its hard to understand the dynamics of the system. The cap is supposed to release at its rating. But other restrictions in the block or heads could show different readings in different locations.
I could ask him where he takes his readings from.

 

It may be curious to measure pre and post tstat and see if there's variance there.

 

The radiator, near the cap makes the most sense to me. Any restriction along the way is going to cause spikes. If you were to run a restrictor vs a t stat I could see where that may help even some of the spikes

 

The rad tank with the cap is the lowest pressure in the system for sure. Here's a log when the sensor was there. Peak of 8psi.

 

It's like measuring fuel pressure from the tank vs measuring it before the injectors. In this case, the T-stat is your regulator and the engine would represent all of the bends and line size changes in your fuel line that might cause pressure changes and the water pump would obviously represent the fuel pump that's engine driven. Hope that helps make it clearer.

 

Yeah,I was thinking the same DL. Just hard to believe the press in the block is so high. It's a good thing though from what I remember reading a long time ago. Might have been Smokey Yunick's book "Power Secrets". Said the more block psi you could generate, the better the cooling system would work.

 

I've run water press sensors in some gt3 cars I've been involved in. What you are seeing is pretty normal (at least for the race cars.). It also really depends on sensor location and t-stat flow. You'll notice a difference between cold and warm pressures as the stat opens. We used it to alert the driver of a sudden water leak. But it also came in handy for cyl sealing info.

 

I would agree that sensor at rad would provide the best information for the overall system.
The wp is not a direct pressure pump. Their designs allow for water to remain stagnant within it as flow is restricted along with actual bypass hose. Ie thermostat.
I too am surprised at your pressure readings.
If you see spikes the same in your radiator. Then I would be concerned with head lifting issues causing it.

 

Does it do it in neutral?if so you know it's pump based.

 

Waiting for answers....

 

Haven't revved in neutral to see. Might not get a chance, put the truck up on ebay and it sold in a few hrs. Waiting for wire of funds....BOOM! Didn't see that coming did ya?