Cheers Jay. It gave me context to why race teams with NA cars invest effort in fresh air supply to there engines with closed air boxes and plenums rather than a simple shield.
The old BBQ plate trick. Easy 5 min fix is to wind the rear of the bonnet up 5 to 10mm this will let a lot of the hot air out. The best way for me was to put 2 heat shields over the exhaust with a 10mm air gap , 2 beads of silastic on the sides and a hose to the front of the car to blow air between the 2 plates.
I did see something like this on an old VicZcar race motor sale thread. There was a duplicate offset shield that matched the profile on the hot side of the intake and was spaced off about 5-10mm. It was not sealed but certainly appeared to use air at the insulator between the plate and air box.
280zx has the airbox in front of the radiator, and makes it a true cold air intake.. granted it’s a normal manifold. But a stock 2.8L with headers and bigger throttlebody did 140whp
On my Triple Mikuni 44 powered L28. I ran without a heatshield for a while, but I found in traffic the car could stumble a bit on take off possibly from vapour lock type behavior. After installing the heat shield I noticed it far less, although if I'm stuck idle in traffic on a hot day for long enough it does get a little hesitant when first taking off. When moving again it's fine. I also have a vented 260z bonnet so I think that helps with heat dispersion. Although I can't be 100% sure.
The people have spoken, air box! Build a dry carbon one, its pretty simple to do if you build a mold out of cardboard. I plan on making my own pretty soon. Instead of making your own duct, check out the oem intake tube for the 280ZX, its the perfect shape and pretty cheap if you find one on ebay. Ive owned two cars with ceramic coated headers and its pretty dramatic how much cooler they are. That said, ive also had a car that i header-wrapped, which also worked great and looked equally badass with the "titanium" colored kevlar wrap. Just give the header some rust proof coating first. One more idea: The Inspection lids of datsuns are very cheap to find and quickly swap-able. Perhaps some type of louvres or restomod style holes/vents? Love the videos!
Thanks Jan. I am currently design and prototyping an air box as many OEM parts are difficult to find in Australia. Thanks for your suggestion on the inspection lids, you've given me ideas 😉
I did model up some options in Fusion 360 suitable to be printed using Formfutura's Apollo X filament but after measuring the temps around the intake the 110C limit of the filament might be pushing it. Maybe wet lay CF? An airbox is something I will test later in engine development after I have completed a few other changes like new cam and port the head.
An extreme method I saw on a tarmac racing 240z was an "airbox" that was basically a heat shield that sectioned off the air intake/battery side of the engine bay. Went from the chassis rail up to the carb intakes then up to the bonnet. Rear was the firewall and front was the left side of the radiator mount.
Heat shields block radiant heat to prevent other components from getting hot. I think a heat shield between the exhaust manifold and intake/carb is a good idea to prevent your ITBs from heating up. But the real problem is that your headers are heating the essentially stagnant air under the hood of your s30. Your engine is sucking in that heated air. I think, at a minimum you should vent your hood/bonnet to allow that air to escape and be replaced with fresh air. If you are still having problems then add a cold air intake.
So I would say wrapping the headers which is one of the biggest heat sources, then take a similar approach to what you've done here but you make a plate that has slots and an 80ish degree bend that gets mounted on the lower intake/upper exhaust flange to put a physical barrier between the two manifolds and have heat reflective tape on the bottom(the gold nasa looking stuff). THEN, I've seen people pretty effectively take the oem airboxes that are for the SU's, widen them by a few inches in the middle by sacrificing a second one, smooth it out/paint it so it looks clean and somewhat factory, and then round up the opening at the end so you can fit a 3in. Coupler/tube to a filter element that sits behind the grille in the car. I wish I knew how to contact content creators directly because we just did this in a 72 240 with an l24 and triple mikuni's and I'd email you pictures to see kind of how we did it/what it looks like
Bonnet open or closed made little difference last time I was at the dyno. With bonnet opened, radiator fans on and after a couple of runs my MAT sensor read 75C (ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-udKxrtLthts.html). I did make 225whp under these conditions however.
Thanks Aaron, I have been tempted with going straight trumpets on my stroker motor, but given your thoughts on the ineffectiveness of heat shielding wonder if sticking with the cold air intake is preferable. I am conflicted with the relative inefficiency of airflow with cold air intake vs trumpets and effect on performance. Interested to see where you go from here.
Thanks Wade. It's a bit of a tough decision isn't it. For me the no cost option is to see if I can tune without an airbox first. On face value any power loss from accomodating a hot, less dense, intake air seems to be minimal but I could be wrong!
Would be interesting for you to ceramic coat your headers and see the temp difference, I’ve been told it makes a lot of difference but I’ve never seen a proper investigation. I am of the belief that ceramic coating is more effective than wrapping, but again I haven’t seen any investigations on the matter
I just had my MSA 6-1 headers blasted/painted and considered wrapping them since I'll have DCOEs sitting on top of them but everything read on the forums suggest it's more detrimental to do that... hmm
@@kyushaspeed Yeah, moisture getting inside the wraps and eating it from the inside out. I live in EXTREMELY humid Houston so I try to do everything short of parking my car in a gigantic bowl of rice to keep the moisture out anywhere I can...
Make the heat shield from some silcone bonded mica sheet that has a thermal conductivity of 0.3 W/m K versus that of aluminium which is 88 to 251 W/m K
The heat that the ally shield seem to absorbed and emit originally radiated from the headers. I cannot remember what that property is call, emissivity? 🤔
At the least use some sheet stainless. Titanium also works well. I would use some kind of coating to cut down in thermal gain. Ideally coat and wrap your headers, better heat shield, and some kind of airbox (Coloplast wrapped in aluminum tape would probably work for a cheap mockup to test with).
@@kyushaspeed Yep a proper Cold Air Intake works. Basically you just didn't go far enough in the project. you only got it partially done. Thus the poor results. Heat management on an L-Series is VERY complicated. Turbo engines are even worse. Basically you have to isolate the whole Intake side of the Intake system from the Exhaust. The best system I have seen was on a GT2 NA Race engine with ITB's. They had created a semi Open Air box. Like you they did not have enough room around the Trumpets and Wheel housing to build a fully enclosed Air Box out of Carbon Fiber. The headers were all Ceramic coated. Next step was to build a horizontal shelf under the Intake Plenum with Stainless Steel sheet. Insulated with NASA style Ceramic Tiling on the bottom. ( Nascar suppliers ) . Gold Foil would also work. Though not as well. The horizontal shelf extends all the way to the Wheel housing , Firewall and Rad support. Only a 1/4" gap to allow for slight engine movement. Then foam sealing on edges. A vertical Seal plate was affixed to this horizontal plate to seal this Box to the ITB's and hood. This was sealed with foam stripping as well. The important part that is often missed is not building a proper Horizontal plate that completely isolated the exhaust system and lower part of the engine bay from the upper part of the engine bay and the Intake system. This is essential. SS was used as it Thermal conductivity is much less than Aluminium. You do NOT want to use aluminium plate as it absorbs heat too easily. You want the heat reflected or isolated and SS does this very well. That's why high end cook ware has SS handles. So they don't transmit heat. The back side of the Vertical seal plate was also covered in Gold Foil. Then the front of the box was fed by a Ram and Air Filter CAI in front of the radiator. There was also a lower ram Tube that fed air BELOW the horizontal plate to get airflow through that area. That is something that is often overlooked. You MUST have unsubstantial airflow through the engine. The hood had 280Z style Hood vents to allow the High pressure air to escape from the top area of the " Air Box ". . The factory splash pan was used as this produces a low Pressure area at the back of the Oil pan. that draws out hot air at speed. The clever bit was identifying the hot and cold zones. Isolating them and then providing enough Air Flow through the system to avoid stagnation. Cold Air Induction does work.. as that simple test on the BMW with Scotty showed. But it has to be done as a COMPLETE package. With no steps missed. The L-series is particularly complicated for heat management. On a street car and Turbo It's even more complicated. All of the above methods should be applied as well as Ceramic Coating of Turbo Hot side, exhausts manifold and down pipe. On a street Turbo car you can create the Turbo isolation heat shield as described and then add a 3.0" Axial Bilge blower to the bottom ducting that automatically switched on. This provided Air flow to the Lower " Box " of the air system and prevent stagnant air from building up around the Turbo. It worked really well. Air was exhausted from the lower section underneath the car. It was so effective, that the owner had to line the bottom of the drivers side floor pan with the Nascar Ceramic tile to reduce heat from the foot well. Phew.. bit of a long novel. But thought you would find it interesting. Plus it gives you another project to try.
Ever considered ducting around rad to vent air above or below engine (depending if you want a hood louvre or not). Julian Edgar has some informative videos. Experiment with addition of heat shield material (foil) on the engine side of the shield you made? Not sure on its effectiveness.
Thanks Andrew. I know repositioning and angling the radiator and drawing the hot air through the bonnet using the low pressure formed is effective (WTAC cars are a prime example). I have not considered anything like this as the Australian authorities do not like or permit those modifications for road registered vehicles ☹️
@@kyushaspeed if you were able, as a mental exercise, how would you route it? I’m considering doing so when engine is back in car - a little more flexibility on modification over here in Canada.
Higher underbonnet temperatures are an advantage when engines were carburettor fed as opposed to fuel injection because it assisted in fuel vaporisation particularly at part throttle and warm up. Manifolds with carburettors have a means to heat them to stop petrol falling out of vaporisation- One reason a reverse flow or "non crossflow" head can be of benefit for carburettor fed engines. One advantage of an airbox is that you don't have to use individual filters per intake, but according to Julian Edgar you can expect peak power to improve by 1% for every 4 degrees C decrease in intake temperature which is another reason a remote airbox or "cool air intake" can be a good idea. It's just as the car is stationary intake temp will rise and the ECU parameters under these conditions would of course have to change to optimise that. I'd be excited to see the results of an optimised airbox on your project. A 12C decrease in intake air temp could translate to a 3% increase in top end power. Improves throttle response too.
Sounds like Julian has simplified the ideal gas law. Density changes with temperature are not quite linear but approximate a 4% change in density with 15C of temp which is about 1% density change with 4C.
