Friday, May 30, 2008 - 05:45 pm, by: Jeff Bedsor(Jeff_bedsor)
Andrew - I don't know where you come up with these theories, but I'll have another go at explaining. How can reducing temps in the engine bay by 40C in my case (I measured this over several days with a digital temp sensor 50mm above the turbo's and in the valley near the injectors) which in turn reduces the thermal output of the engine, where the coolant is circulating have a negative impact on cooling. If you go by the standard temp gauge which doesn't move from the centre reading while a proper water temp gauge varies between 70C and 95C, you are not getting a true indication of what is going on. The back of the bonnet may be a high pressure area, but wouldn't the greater pressure of the incoming air from either the radiator area or the bonnet scoop overcome this pressure? The best example I can give you is today coming home from work, on a usual day 25C to 35C the water temp sits on 80C. Today it was raining hard so I put a plug in the scoop Guess what, the temp went up to about 88C. (outside air temp was 17C) to me that is proof enough that the bonnet scoop works in reducing temps. I go of facts and things that i have first hand knowledge of, do you have anything to back up your theory's? Christian, Lew - I know what you mean, my cough high flow cough cat would cause me problems.
Friday, May 30, 2008 - 06:03 pm, by: Blake Gloyn(Blakenz)
in practice, the removal of the rubber strip at the rear of the engine bay reduces underbonnet temps markedly. i think the air rushing up over the windscreen helps suck the air out of the engine bay. there is no way the air will do a 180 degree turn and go into the engine bay. seriously, you can now put your hand on the inlet manifold of my car after a five hour drive. but you can't if the car is stock- too hot.the removal of that rubber strip is the first mod that you should do if you own a 300zx. no longer cooking everything under the bonnet.
Friday, May 30, 2008 - 07:25 pm, by: Jeff Bedsor(Jeff_bedsor)
Daniel, it's a sort of 3 inch pipe straight through with 2 rival performance mufflers at the back. Flows very well, a little bit droney at low speed, but a nice crisp note under power.
Andrew Ferres DieHard WA '90 C-F Celsior V8, '84 Soarer V8, '91 Supra V8
Although that doesn't really go into forward facing vents, but heres a modded pic of something in the first link.
At the end of the day, what I'm pointing out is not theory, its simple physics. Just because you have not experienced what I'm pointing out does not automatically mean I'm sprouting bullshit.
Oh, and for the record, removing the rear strip or raising the rear of the bonnet is not only illegal, its also stupid.
And Blake, if at any time the air pressure at the rear of the bonnet is higher than the air pressure inside the engine bay, the air has no choice but to do a 180deg turn and go into the engine bay. Simple physics says it does. Its the same theory that allows planes to fly, and spoilers to work.
Have a look at any of the 80's HDT/HSV cars. They all have the air INTAKE at the REAR of the bonnet, and then a very nicely constructed shield between the underside of the bonnet and the engine, with the airfilter sandwiched between them. EDIT: I may be misremembering the shield.
Saturday, May 31, 2008 - 06:29 am, by: Blake Gloyn(Blakenz)
why is it illegal to have the strip removed or a rear facing vent? so if a oil,water or fuel line splits, your windscreen wont be suddenly covered in junk , right. But this can never happen,because your air is doing a 180 degree turn into the rear facing vent, isn't it andrew? ha ha ha looks like the authorities don't know basic physic "theories".
Lew Radbourn Trader Queensland / Gold coast jzs147 93 TT / uzz30 93'/ 2 X uzz31 92' s
Saturday, May 31, 2008 - 08:43 am, by: Lew Radbourn(Marlew)
OK i can see what Andrew is trying to explain here; Now a real test Has any body got the rubber strip still in there car and is about to take it out??????? Before you do go and take the car out for a flogging and then lift the bonnet then take the strip out and flog it again to the same extent to what you did with it in. then lift the bonnet again and see what the heat difference is. it will not effect your cooling system. and the rear exit point actually acts as a ventury and will suck the hot under bonnet air out from under the bonnet YES there is turbulance at high speed at the lower area of the windscreen which will effect the exit flow. BUT even if it helps the slightest amount in dropping the temp under the bonnet it is a good thing. and most cops wouldn't know that it was there or if it wasn't
Andrew Ferres DieHard WA '90 C-F Celsior V8, '84 Soarer V8, '91 Supra V8
Saturday, May 31, 2008 - 09:29 am, by: Andrew Ferres(Peewee)
The reason its illegal is that the engine bay is designed to contain all fires/liquids/gases.
During the speeds where the rear of the bonnet IS acting as an exit point for air, things can escape. (I never said it was ALWAYS a high pressure point)
And whats directly behind that strip on 99% of cars??? The air intake for the cabin of the car!
So any hot air, or any noxious gases from a small fire, or exhaust leak, fuel leak, etc, are going straight out of the engine bay, and straight into the cabin and into your nose. SMART IDEA THERE EINSTEIN!!
And FWIW, when I bought my car, the previous owner had removed that strip. After finally finding one to replace it, you could easily feel the difference in aircon temps at lower speeds. And no, there was no difference in coolant temp or any performance. Never bothered to check the engine bay for a temp difference.
Saturday, May 31, 2008 - 09:49 am, by: Jeff Bedsor(Jeff_bedsor)
My son is bringing home a Magnehelic gauge next weekend, so I will do some tests and get some real results on high and low pressure areas. As I said before Andrew, I go on real experience and do all my own work, I am not a keyboard mechanic that takes everything he reads from some deadbeat motoring journalist as gospel. I work out what has positive and what has negative impacts by doing the mods.
Andrew Ferres DieHard WA '90 C-F Celsior V8, '84 Soarer V8, '91 Supra V8
Saturday, May 31, 2008 - 10:57 am, by: Andrew Ferres(Peewee)
You do have to remember Jeff that you are only able to do test a small amount of things with limited resources and limited scenarios. What works for your car may not work for anyone elses. If you had put that scoop a couple of inches further back, or a couple of inches further forward the results may have been very different. Its something that needed to be tested to find the most optimal place to put it. It will be interesting to see what your tests show.
Your cooling system so far is not being negatively impacted by the mods you have performed. Whether this will always be the case only time will tell. Perhaps when you squeeze another 50 or 100hp out of the motor you'll push your cooling system to the limit and things will start going the other way. Thats just something we'll have to wait and see (if you ever decide to go for more grunt that is).
For my own curiousity do you have a nice cold air intake or a pod filter thats exposed to engine bay air? Unfortunately with this forum I can't quickly search to see if you have a members ride thread or something.
Saturday, May 31, 2008 - 01:32 pm, by: Jeff Bedsor(Jeff_bedsor)
I am currently getting quite good power out of my setup, just ran an 11.99 down the quarter on standard turbos. So that makes me next in line after Daniel (11.89 or 4?) for the fastest stock turbo Soarer in AUS, so the mods I have done seem to work quite well. I am actually having the problem of the cooling system working to well at the drags, I have to let it run for a while to get the temp to 80C between runs. Yes I do have a pod filter located where the standard one was.
Andrew Ferres DieHard WA '90 C-F Celsior V8, '84 Soarer V8, '91 Supra V8
Saturday, May 31, 2008 - 05:42 pm, by: Andrew Ferres(Peewee)
Another test you can do, one that I believe is very beneficial, is to measure the air temps inside the intake plenum, for both with the scoop open and with the scoop plugged up.
I'm not sure where the stock air temp sensor is on a 1JZ though, so it may be a hard test if you don't have access to a remove thermometer you can temporarily plumb in.
Saturday, May 31, 2008 - 05:51 pm, by: Daniel Clarke(Dieseltrain)
The problem with the actual stock inlet air temp sensor, it retains heat too badly and wont give accurate direct changes in Real Life time...
I aggree with Lew and Blake though! If the rear strip removed for racing purposes only decreases underbonnet temps and temps on manifolds and such, how can this be a bad thing? IM talking strictly for racing. I would replace it when back on the street as i agree it would increase incoming cabin temps for the air vents.
Saturday, May 31, 2008 - 06:22 pm, by: Mustafa Akgul(Muzzy)
Daniel Clarke wrote on Saturday, May 31, 2008 - 05:51 pm:
The problem with the actual stock inlet air temp sensor, it retains heat too badly and wont give accurate direct changes in Real Life time...
Daniel when I installed the EMS eci into my previous car the designer of the system told me to mount the air temp sensor in the plastic pipe before the manifold in order to get better temp readings.
I think what Jeff is doing is great because he is actually experimenting with the car. Thats what I did when I baught the soarer.. when my soarer ran the first ever 12 second pass it had a gtr cooler connected by BRASS plumbers pipes, apexi safc Tuned by me at home, open diff street tyres home designed oil air separator VS commodore air box intake system etc.
so its allways fun to do things others dont.
all should remember that the factory designed all this for factory power levels. most soarers are modified and need extra cooling.
Andrew Ferres DieHard WA '90 C-F Celsior V8, '84 Soarer V8, '91 Supra V8
Sunday, June 01, 2008 - 12:02 pm, by: Andrew Ferres(Peewee)
Is the stock sensor not housed in a plastic shroud?
I used a GM/Delco sensor in mine and except for the threaded part (and the sensor itself), the whole thing is insulated from the manifold by plastic. As long as you put it directly in the airflow path its very quick to react.
Where is the stock sensor? I know the Turbo A 7M has it at the rear of the intake plenum. Not a bad place by I prefer to put it where the cold start injector goes (obviously not possible on the JZ's though)
Monday, June 02, 2008 - 09:01 pm, by: Callum Finch(Sigeneat)
Lew Radbourn wrote on Saturday, May 31, 2008 - 08:43 am:
Has any body got the rubber strip still in there car and is about to take it out???????
To add more to the mix.. I believe Blaine Hansen before he drove the to big SC meet a few years back from WA to Vic (??) in his v8 removed the rear rubber seal strip from the bonnet. I remember him saying how at cruise speed the car was running ~1notch lower on the engine temp gauge on his dash.
Friday, June 06, 2008 - 12:11 pm, by: Maurice Diggler(Mau_rice)
I ripped the rubber strip off on my car after reading this thread and noticed very quickly that I don't need to demist my windscreen on foggy mornings anymore, the heat from the engine bay coming up thru the back is doing it for me I couldn't be arsed with temperature readings but I am now noticing a lot of heat pouring up the back of the bonnet after a hard run, worth it IMO, haven't noticed any lethal gases in the cabin yet either, bonus! lol.
Lew Radbourn Trader Queensland / Gold coast jzs147 93 TT / uzz30 93'/ 2 X uzz31 92' s
Friday, June 06, 2008 - 01:10 pm, by: Maurice Diggler(Mau_rice)
Exactly Although, I am now so paranoid everytime I drive along and get a scent of anything in the cabin, then I notice the ••••••• in front of me pumping out smoke lol.
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