Too close for comfort?
Thread Starter
Joined: May 2003
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From: CA (Bay Area)
Too close for comfort?
my coolant supply line is quite close to my DP. ive bent it about as much as i can, short of having a new one welded up. do you guys think this is too close? if i wrap my downpipe as well as foil wrap the coolant pipe theyll be close to touching. 
also, quick question... what is this port for?
thanks, heath
also, quick question... what is this port for?
thanks, heath
Junior Member
Joined: Jun 2005
Posts: 35
Likes: 0
From: Niagara Falls
Yes
Well, I was going to study for my FE's but I got side tracked with the rx7club forum again. You gave me the perfect excuse to study my heat transfer....
Common sense wise, I say definitely. But if that's not enough I did some calculations. I figure, if you're going to go through the trouble and expense to redo that pipe, you better have a reason.
I made some assumptions here. I decided that your dp is 4 inches in diameter and the coolant hose is .75. I also assumed your EGT's would put the dp temp at about 1400 F during hard running. I also assumed, due to surface area differences and how close those pipes are, about 10% of the heat coming from your dp will hit that pipe. Note, these dimensional figures will not change my answer greatly if I'm off. I also assumed the thermal wrap would be of fiberglass and 1/16" thick, wrapped only once on both pipes. It is recommended that you only wrap a pipe once because retaining too much heat can actually be a bad idea. On to the numbers...
Through some crude number crunching I found that if the coolant was at room temperature, the coolant pipe would be approximately 170 F. I did NOT take into account radiation which is pretty difficult to estimate due to the pipe being rusted and the odd angle it is at. being that your coolant temperature will most definitely not be at room temperature, this could seriously raise it. These engines are prone to overheating and I would seriously suggest moving that pipe. you should wrap your dp regardless though. This will greatly reduce underhood temperatures and prolong your engines life.
No idea what that port is, sorry
Hope this helps you in your decision. Thanks for the excuse to study!
Common sense wise, I say definitely. But if that's not enough I did some calculations. I figure, if you're going to go through the trouble and expense to redo that pipe, you better have a reason.
I made some assumptions here. I decided that your dp is 4 inches in diameter and the coolant hose is .75. I also assumed your EGT's would put the dp temp at about 1400 F during hard running. I also assumed, due to surface area differences and how close those pipes are, about 10% of the heat coming from your dp will hit that pipe. Note, these dimensional figures will not change my answer greatly if I'm off. I also assumed the thermal wrap would be of fiberglass and 1/16" thick, wrapped only once on both pipes. It is recommended that you only wrap a pipe once because retaining too much heat can actually be a bad idea. On to the numbers...
Through some crude number crunching I found that if the coolant was at room temperature, the coolant pipe would be approximately 170 F. I did NOT take into account radiation which is pretty difficult to estimate due to the pipe being rusted and the odd angle it is at. being that your coolant temperature will most definitely not be at room temperature, this could seriously raise it. These engines are prone to overheating and I would seriously suggest moving that pipe. you should wrap your dp regardless though. This will greatly reduce underhood temperatures and prolong your engines life.
No idea what that port is, sorry
Hope this helps you in your decision. Thanks for the excuse to study!
Thread Starter
Joined: May 2003
Posts: 4,150
Likes: 0
From: CA (Bay Area)
Well, I was going to study for my FE's but I got side tracked with the rx7club forum again. You gave me the perfect excuse to study my heat transfer....
Common sense wise, I say definitely. But if that's not enough I did some calculations. I figure, if you're going to go through the trouble and expense to redo that pipe, you better have a reason.
I made some assumptions here. I decided that your dp is 4 inches in diameter and the coolant hose is .75. I also assumed your EGT's would put the dp temp at about 1400 F during hard running. I also assumed, due to surface area differences and how close those pipes are, about 10% of the heat coming from your dp will hit that pipe. Note, these dimensional figures will not change my answer greatly if I'm off. I also assumed the thermal wrap would be of fiberglass and 1/16" thick, wrapped only once on both pipes. It is recommended that you only wrap a pipe once because retaining too much heat can actually be a bad idea. On to the numbers...
Through some crude number crunching I found that if the coolant was at room temperature, the coolant pipe would be approximately 170 F. I did NOT take into account radiation which is pretty difficult to estimate due to the pipe being rusted and the odd angle it is at. being that your coolant temperature will most definitely not be at room temperature, this could seriously raise it. These engines are prone to overheating and I would seriously suggest moving that pipe. you should wrap your dp regardless though. This will greatly reduce underhood temperatures and prolong your engines life.
No idea what that port is, sorry
Hope this helps you in your decision. Thanks for the excuse to study!
Common sense wise, I say definitely. But if that's not enough I did some calculations. I figure, if you're going to go through the trouble and expense to redo that pipe, you better have a reason.
I made some assumptions here. I decided that your dp is 4 inches in diameter and the coolant hose is .75. I also assumed your EGT's would put the dp temp at about 1400 F during hard running. I also assumed, due to surface area differences and how close those pipes are, about 10% of the heat coming from your dp will hit that pipe. Note, these dimensional figures will not change my answer greatly if I'm off. I also assumed the thermal wrap would be of fiberglass and 1/16" thick, wrapped only once on both pipes. It is recommended that you only wrap a pipe once because retaining too much heat can actually be a bad idea. On to the numbers...
Through some crude number crunching I found that if the coolant was at room temperature, the coolant pipe would be approximately 170 F. I did NOT take into account radiation which is pretty difficult to estimate due to the pipe being rusted and the odd angle it is at. being that your coolant temperature will most definitely not be at room temperature, this could seriously raise it. These engines are prone to overheating and I would seriously suggest moving that pipe. you should wrap your dp regardless though. This will greatly reduce underhood temperatures and prolong your engines life.
No idea what that port is, sorry
Hope this helps you in your decision. Thanks for the excuse to study!
. ill thermal wrap the DP and silver heat wrap the coolant line and cross my fingers that the secondary lives.
Junior Member
Joined: Jun 2005
Posts: 35
Likes: 0
From: Niagara Falls
Knowing that I haven't completely wasted my time at school is a great thing... If it were me, I would move it. If not, your best bet would be to get fiberglass wrap for the DP and for the coolant pipe. Then use the silver wrap on top of the coolant wrap. This will insulate it both from convective heat and radiation. You may also consider getting a heat shield for around the turbine side. You can fabricate one with some sheet 16 gauge stainless that has the bottom covered in thermal wrap. If you're crafty enough, you can hide the tape so no-one can see it. Polished stainless looks pretty good too. You could trim the edges with some thin stainless scrap that's bent over the edges to smooth it out and coat it with high temp paint to give it a nice finished look. Good luck and keep us posted!
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Thread Starter
Joined: May 2003
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From: CA (Bay Area)
1000 years, lost in time.
Joined: Oct 2007
Posts: 178
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From: Australia
Hi Rotamotor,
Definately too close. And advice to shield or wrap is 110% correct.
I can see space is an issue, so I'd wrap the coolent pipe and add heat shield between it and the dump pipe and the coolent, securing it to the mounting bolt at 10 o'clock. You can use something like an alluminium sheet between the two, slightly wrapped around the dp, but let it open up and flare around the dp very loosely on the areas away from the coolent pipe (that way it will ventilate and disperse the heat in the sheet where the coolect pipe is at it's closest to the dp.)
Cheers
Definately too close. And advice to shield or wrap is 110% correct.
I can see space is an issue, so I'd wrap the coolent pipe and add heat shield between it and the dump pipe and the coolent, securing it to the mounting bolt at 10 o'clock. You can use something like an alluminium sheet between the two, slightly wrapped around the dp, but let it open up and flare around the dp very loosely on the areas away from the coolent pipe (that way it will ventilate and disperse the heat in the sheet where the coolect pipe is at it's closest to the dp.)
Cheers
I dont like it, but I dont think ti will be a problem. The coolant in the pipe will keep the pipe cool, so the only problem would be raising total coolant temperatures, and the heat xfer into that pipe is minimal compared to what happens in the block.
Have you ever boiled water in a paper cup in a campfire? Same principle, the fluid has a high enough heat xfer coefficient that it maintains a uniform temperature throughout the entire volume of the fluid, so no one point on the cup can get hot enough to ignite.
coblepots I wouldnt worry too much about studying for the FE, if youre a mechanical it is insanely easy. I didnt study at all and I passed it no problem last year.
Have you ever boiled water in a paper cup in a campfire? Same principle, the fluid has a high enough heat xfer coefficient that it maintains a uniform temperature throughout the entire volume of the fluid, so no one point on the cup can get hot enough to ignite.
coblepots I wouldnt worry too much about studying for the FE, if youre a mechanical it is insanely easy. I didnt study at all and I passed it no problem last year.
How about putting some DEI fire sleeve on the coolant line and thermal wrapping the downpipe?
http://www.designengineering.com/products.asp
http://www.designengineering.com/products.asp
