ZCar Forum banner

Looping the Heater Hose

5036 Views 17 Replies 10 Participants Last post by  (goldfish)
Well, there was an argument here (there always is) about how guys have 'run for years' with their heater bypassed and looped to the inlet of the water pump. I have contended that on most 240's done this way, it results in overheating issues. At long last an instrumented engine in a controlled environment was run in such a manner to test this.

Long and short of the results: CHT Readings at a 25HP load at 4500rpms showed 170F (on a 160 thermostat controlled dyno) with this hose BLOCKED OFF (as I suggested.)

The hose open and looped directly to the water pump showed a CHT at the same load and RPM's of 220F.

Moral of the story: Tony D is right, DON'T LOOP THAT HOSE, BLOCK IT OFF (just like Nissan does when your heater water control valve is CLOSED!)

That engine was later 'tested further' after determining this little factoid (attached)
Not open for further replies.
1 - 18 of 18 Posts
So I guess all the other pics over on Hybridz re: hose looping are photoshop'd as well?
Thanks Tony for clearing that up :)

and no its not photoshop'd seen that happen to a subaru engine running too hot at the race track too.
Love the glow of that exhaust manifold and turbo. No wonder the fuel lines on these engines vapor lock.
adroitcaptor said:
PUH-LUEASE! Don't post crap like that, I don't have the time nor inclination to play games with photos. I take the shots and upload them, that's it. If you can't handle the REALITY of the photos I post from personal Dyno Time, don't make idiotic internet commentary. That engine was holding 5000rpms for 5 minutes making 390+ ft-lbs of boost for coolant and oil cooling stability testing. I was not allowed in the testing bay during the run---that photo is actually AFTER the engine is back at idle and cooling down for about 90 seconds by the time I got to that side.

My kid got the task of editing the video. DURING the run, the turbo was so bright there were shadows cast on the aluminum heat shield and the wall. This photo is nothing, but the only thing in the room DURING the run was the little Hero-Cam.

And likely, those videos won't be posted here, for obvious reasons (this retort being one of them)---casting pearls before swine does have it's limits. We can post them where people appreciate them for what they are, and don't think someone is a shuckster trying to pull some teenage internet fast-one.
See less See more
After seeing multiple dyno explosions and fires, I can fully understand why they won't allow you in there. Engine dynos can be rather dangerous places.
Actually, for some of the later runs that day, I had to manually actuate the throttle from the brake end of the dyno because the hat diaphragm on the dynos hydraulic servo sprung a leak. After the VQ table was straight, we went on toe load testing the second day. I was not that keen on the idea of having a piston and rod give me a PT...which runs through your head when you are reaching over an engine spinning at 7KRPM and have to hold it there for three minutes for stabilization of reading points!

But hey, what do I know about this stuff, right? I'm a blowhard who sits behind the computer all day long 'with nothing better to do' right? he he he...

Here's a shot still in the N/A portion of the map after I moved to the brake end of the dyno. The turbo is a 'little hotter' than in the photo above...
See less See more
Tony my feelings are hurt. You of all people should not only appreciate my humor but catch it.

The picture COULD have been taken during ANY type of test. There would be NO point to photoshop it even if you were lying. (Which I never have assumed of you.) Logic being stated. Hence why I would not have thought ppl to assume I was serious.

I expect more from you Tony... maybe not gnoze but def. you!

PS - Photoshop less pl0x kk thnx.
If you don't mind me asking can we get some specs on that engine, such as Hp, torque, what was done to it? Just curious.


ps. after reading this thread it reminded me of testing porsche puts their engines through http://www.youtube.com/watch?v=fv53RbvgfGc
torquemonster said:
If you don't mind me asking can we get some specs on that engine, such as Hp, torque, what was done to it? Just curious.
Not Really, I found posting those kind of things simply causes idiots to make a ruckus and it's not worth my time. Understand this is nothing against you---if you want to send me a PM with your e-mail I can go into it more off-forum. This place isn't conducive to high-end R&D discussions. In any case it was more a coolant testing session, where we were testing modifications to the cooling system to evaluate their effectiveness. We would hold the engine at 500rpm load points at various load levels from mihnimum load to maximum load through the operational range of the engine.

We started at 3000rpms, through to 7000rpms, putting a set load on the engine, and holding it there for five minutes at a time to let all the temperatures stabilize. I can give an isolated load point as an example: 5000 rpms, 16 psi boost, 398 ft-lbs torque, 170 F Engine Out Temperature, 170 F CHT, 210 F oil throw off average, 225F oil sump temperature.

Torque 'Peak' for this engine was flat between 5300 and 5600 rpms. This point was below peak torque. I'm sure you can do some calculations and extrapolate from this out to 7000 in various scenarios! Heh heh heh . This is actually the 'low boost/low power DURABILITY build' of this particular engine. We have another which is quite a bit more radical, this one is pretty conservative due to some aspects of it's build.
See less See more
Tony, thank you for posting that great pic and the accompanying information on the heater loop. I can understand your hesitation to post more info on the engine out in the open. If there is one thing I have learned on this site (and a certain other site), it is that you have some of the best information on Z's, such as the start solenoid cutoff to prime the fuel rail, even if some people won't listen. I for one hope you can put up with the nonsense on this site and continue to post information like this.
T....still looking for a rebuild kit or replacement for the vacuum water **** in the 78. Maybe an outfit in Texas can help. In the mean time, just having read your article reg'd looping the hose, hows about running the H2O thru the heater core?? Would provide coolant cooling and still give heat for the defrosters. Will try it and let ya know how the temp gauge reads
dick w/283
You go!!
dick said:
In the mean time, just having read your article reg'd looping the hose, hows about running the H2O thru the heater core?? Would provide coolant cooling and still give heat for the defrosters. Will try it and let ya know how the temp gauge reads
dick w/283
This 'looping' issue came up when people decide to eliminate the heater core for 'weight elimination' or 'failed heater core'. It seemed like common sense to me that you BLOCK the hose, not LOOP it as that is the NORMAL configuration (the heater valve is closed most of the time, therefore BLOCKED, when it's open, the heater core COOLS the water before recirculating it and doesn't cause overheating problems.)
But like many things here, morons insist on anecdotes and myths without a scintilla of evidence other than 'screwing their sister for 17 years'---just because you do it doesn't make it right... and now the EVIDENCE is clear: Looping the hose does EXACTLY what I said it does (and what common sense says it would!) Raise the temperature in the head to dangerous levels.

Understand the level of cooling system modification on this particular engine is quite high. On a car with stock head, stock block, stock thermostat the numbers you would have would be CONSIDERABLY HIGHER. Where we were running 220F, a stock engine would be close to 260+F! Tell me that won't cause a problem.

Looping it through the core would work if you can stand to have the heater on 'high' or whatever. Remember the heater works porportionally, so wide open really isn't the same as an open hose.

I never figured out how someone could think shunting a 5/8" hose with 180+ F hot water right into the pump inlet wouldn't increase their engine's temperature, but such is the 'logic and false science' that perverts and permeates this board.

Anyway, the thing to take away is when you are running no heater core---just CAP the hoses. Or plug the threaded ports. Whatever you do don't simply 'loop the hose' and think you are doing yourself any favors!
See less See more
Moot point because as I understand it, Healy wants HEAT!!
I'm going to have some more questions for you about this Tony. I have to study your cardomain page some more too.
1 - 18 of 18 Posts
Not open for further replies.