How big a mistake did I just make?

Technical questions and answers about the Mazda Bongo

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jimmo62
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How big a mistake did I just make?

Post by jimmo62 » Sun Feb 23, 2014 7:47 pm

So, I was lubricating the heater motor bearings as it was squeaking and the job went very well - nice a smooth and quiet now. While I had the heater out I noticed that there was a little surface rust on the 2 big metal pipes under the heater/air ducting. Thinking they were water pipes I painted over the rust with Hammerite as I have heard that the metal water pipes can sometimes rust through. However I now think they are the intercooler pipes having seen some on ebay - two fat pipes connected to a small cooling matrix below the radiator and running back under the engine....

What's the opinion, do these pipes get really hot? Will the paint bake on, peel off, make a nasty smell for a while? Or should I try to scrape it all off in case it burns?

So annoyed with myself for making an assumption without checking properly!
nth
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Re: How big a mistake did I just make?

Post by nth » Sun Feb 23, 2014 8:04 pm

Don't worry, the inter cooler pipes won't really get that hot, all that passes through them is pressurised air. You would be lucky if the got more than a few degrees higher than ambient temperature & they won't get anywhere near as hot coolant/water pipes would have.
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jimmo62
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Re: How big a mistake did I just make?

Post by jimmo62 » Sun Feb 23, 2014 8:09 pm

Great thanks that is good news!
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The Great Pretender
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Re: How big a mistake did I just make?

Post by The Great Pretender » Sun Feb 23, 2014 10:38 pm

nth wrote:Don't worry, the inter cooler pipes won't really get that hot, all that passes through them is pressurised air. You would be lucky if the got more than a few degrees higher than ambient temperature & they won't get anywhere near as hot coolant/water pipes would have.
Are you sure?
If that was the case why did they bother to fit an intercooler? :shock:
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Re: How big a mistake did I just make?

Post by nth » Mon Feb 24, 2014 11:18 am

The Great Pretender wrote:
nth wrote:Don't worry, the inter cooler pipes won't really get that hot, all that passes through them is pressurised air. You would be lucky if the got more than a few degrees higher than ambient temperature & they won't get anywhere near as hot coolant/water pipes would have.
Are you sure?
If that was the case why did they bother to fit an intercooler? :shock:
Yes when the turbo compresses air it gets warmer but the intercooler is not just for cooling the air back down its also making it cooler than it was at ambient, by doing this you increase the engines volumetric efficiency, the colder the air the more you can get into a fixed size space (like a cylinder in an engine) you can then get more power out of the engine if the air is colder. Not all turbocharged engines even have an intercooler. Iv been in the motor repair trade for over 15 years & I have never burnt my hand or heard of anyone that has on an intercooler or its pipe work but I have had a few burns from coolant pipes.
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Re: How big a mistake did I just make?

Post by The Great Pretender » Mon Feb 24, 2014 10:36 pm

nth wrote:
The Great Pretender wrote:
nth wrote:Don't worry, the inter cooler pipes won't really get that hot, all that passes through them is pressurised air. You would be lucky if the got more than a few degrees higher than ambient temperature & they won't get anywhere near as hot coolant/water pipes would have.
Are you sure?
If that was the case why did they bother to fit an intercooler? :shock:
Yes when the turbo compresses air it gets warmer but the intercooler is not just for cooling the air back down its also making it cooler than it was at ambient, by doing this you increase the engines volumetric efficiency, the colder the air the more you can get into a fixed size space (like a cylinder in an engine) you can then get more power out of the engine if the air is colder. Not all turbocharged engines even have an intercooler. Iv been in the motor repair trade for over 15 years & I have never burnt my hand or heard of anyone that has on an intercooler or its pipe work but I have had a few burns from coolant pipes.

An intercooler that takes the charge temperature below ambient sound wonderful but impossible as it would be working at over 100% efficiency. Getting anywhere near it would be the holy grail.
I can understand how working on a stationary vehicle the upstream inlet temp would be cool as the turbo is doing virtually nothing. Once you start compressing air you raise the temperature (see Boyle’s law).
The chart in the link shows the relationship between ambient and compressor discharge temp at 10psi, this equates to 0.69bar. Under load the Bongo will boost to 0.9bar equal to 13psi.
As can be seen at sea level with an ambient temp of 70f (20c) the compressed air is at 155f (68c) and at 10000 ft would be 85c. :wink:


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Simon Jones
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Re: How big a mistake did I just make?

Post by Simon Jones » Mon Feb 24, 2014 10:58 pm

Hammerite Metal Paint is rated at 80C continuous / 150C intermittent. Regardless of the temperature of the contents of the pipe, it is located in an area which will be cooled when the vehicle is in motion, but will also soak up heat from the engine bay when stationery. Best way to find out what happens is to take it for a run and then have a feel when you get back home, but be prepared in case it does get a bit sticky :).
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