Electric Water Pump questions ...

[gbrtng]

Originally Posted by A26B

At 70~150mph, I don't think the fans are going to be needed, but if they are, you can always add them later.

I thought the stock calibration turned both fans off above 40 MPH.
Correct me if I'm wrong ...

[A26B]

Originally Posted by gbrtng

I thought the stock calibration turned both fans off above 40 MPH.
Correct me if I'm wrong ...

That may very well be true, I don't know about that. My comment about fans was referring to the addition of aftermarket fans. Thanks for pointing that out though.

[GOLDCYLON]

Originally Posted by Dynomite

I do not see Dewitts Radiator in you signature??

Which Dewitts Radiator are you using and where did you get the Dewitts Radiator?

Im losing track of ALL my mods. Its the all aluminum 2 row replacement with the SPAL fans and from Dewitts

[cvette98pacecar]

I have the same setup as Jerry. I drove the car hard for 6 days straight above 5500 RPM for hours on end and had no issues. Ron Davis Radiator, Stock thermostat with 3 small holes drilled to reduce back pressure to keep the antifreeze flowing through the radiator.

[Dynomite]

Originally Posted by cvette98pacecar

I have the same setup as Jerry. I drove the car hard for 6 days straight above 5500 RPM for hours on end and had no issues. Ron Davis Radiator, Stock thermostat with 3 small holes drilled to reduce back pressure to keep the antifreeze flowing through the radiator.

I am thinking the radiator allowable pressure is increased with the Ron Davis (structural capacity of the radiator) or the Coolant flow resistance is decreased such that greater Coolant Flow will not contribute to higher radiator pressure. In the case where the Radiator has greater burst pressure capacity it would be time to increase the Return Spring Pressure on the Thermostat dis-allowing some Coolant to return directly to the engine. In the former case where the Coolant Flow Resistance is decreased through the Radiator, nothing would have to be done to the thermostat to realize the benefits of the larger capacity radiator.

Ron Davis Radiator w/o transmission cooling

Coolant temperature stays at a constant 185 deg (70 deg F ambient) with 180 deg thermostat.*
a. 1989-1996 C4 Type V8 All Part No. 1-16CV8996
b. Rated 800 Hp
c. Manual transmission
* Coolant Temperatures will climb a bit with AC on (100 deg F ambient).

[grahambehan]

I'll just leave this here.

[RussMcB]

Graham, thanks for joining the conversation.

I must admit, I'm not sure what the first graph is conveying.

I *may* understand some of the second attachment. It seems to show a dangerous situation at 6166 RPM, then (as the RPMs rise and the bypass opens), things get safer (from a pressure and HP point of view, but at the sacrifice of less coolant going to the radiator). Am I reading that right?

Hmm. Page 2 mentions cavitation. I'm guessing that can cause near-total lack of flow and possible engine harm.

Graham, what would you do to prep an LT5 cooling system for road racing (in addition to a better radiator)?

BTW, I talked with a couple of DIY Tune guys at Road Atlanta. They seemed impressed with your "next phase" LT5 project and were happy they were involved.

on edit:
It just dawned on me - Our (and all) cooling systems have a blow-off valve in our radiator caps, usually rated at 12-16 lb. How does that come into play? Are we pushing coolant out (via the cap) at 6166 RPM (and then hopefully pulling it back in when pressure drops)? Is that too insufficient to relieve enough pressure to save a radiator from bursting?

[grahambehan]

The first graph shows electric water pump flow vs press, typically the ratings on these pumps are against free air discharge, once some restriction and therefore pressure differential is present their "advertised" flow numbers diminish.

The cavitation is present on the LT5 pump at high rpm reducing flow, it is actually a pretty efficient pump, even by todays standards, prolonged high rpm use could present problems.

Jerry's recommendations, earlier in the thread have proven to work well for track use.

The pressures are measured on the block side of the system.

Graham.

[5ABI VT]

Maybe I missed it but I find it odd after 24 hr record runs there's an issue with continuous high rpm use? What changes did they make to the car used in the record run?

[RussMcB]

The WRR was done with relatively lower RPM's.

From http://www.zr1netregistry.com/Inform...dRecords.aspx:

"With headers, open exhaust and engine controls calibration revised for racing gasoline, horsepower was 400-410. Tests showed the 190 mph necessary to reset the "24" came at 5500 rpm in fifth, so the gas pedal had a stop at 70% throttle. The car had transmission and rear axle coolers and 3.07 gears replaced the stock 3.54s."