Advice on Ducted hood or not?

I was wondering for guys who track their NSX's, how many of you have ducted hoods and how did that along with undercarriage sealing & splitters affect your handling, stability and cooling. If you do have ducted what has been your brand choice and fitment experience?

I currently have all parts to upgrade to the 2002+ front end except the hood. The car is turbocharged with a large heat exchanger and a Koyo radiator with high flow Spal fan. Oil cooler is fan cooled & in the rear passenger fender. Suspension, brakes, etc are all upgraded & track capable. I probably will do 6 or more track events a year, other than that the car is a weekend fair weather driver.

I have a hookup with American Honda so a factory aluminum non-ducted hood, perfect fitment, would be around $1100 & I can pick it up, and it looks like a Downforce NSXR replica would be about $1600+shipping, unsure of fitment, probably luck of the draw.

Ultimately, best performance is paramount.

Any input would be very greatly appreciated!

Todd

Todd,

If you're like any of us who track our cars in HOT weather I will advise... A ducted hood makes a world of difference. I also think the weak piece in your puzzle is the Koyo radiator. The Spal fan will help in cooldown laps and low speed driving (i.e. in street traffic) but at track speeds it won't help you. Take a look at my build thread for some notes from my perspective. There are a lot of folks who track their cars and there are a handful of good setups here on Prime that work.

Also, a big factor to overheating is not only FI, but how hard you drive near the rev limit/redline. Spending a lot of time in the last 1000-1500 rpm causes temps to rise a whole lot.

Also #2, I wouldn't rely on the factory dashboard idiot gauge to tell you if you're overheating.

Just $0.02.

Where abouts are you located?

RYU, Thanks for the link to your build. Certainly not adverse to getting a more capable radiator PWR, etc.

Unfortunately, I'm in Atlanta, so high temps and humidity.

I have viewing of all temps, oil, coolant, air pre and post intercooler from the AEM 2 viewed on screen with some with audible alarms, plus analog Autometer gauges.

Even back in my N/A days of track events in Southern California, Button willow and Willow Springs, I had temp. Issues from the high revs. So I'm with you there.

I've spent enough time and money, that if making some advisable changes for durability, etc are in order, I'll just have to suck it up.

For me the ducted hood made a huge difference. I drove with an OEM non ducted hood for about 2 years before going ducted in the california heat. On an NA I would typically have to pull in after about 10 laps if ambient temps were above 90*. I bought my CF hood for about 650 off the forum here, i figured i cant lose with the price so i went for it.
Back when I first put it on I would run the track with only a Koyo and my V1 splitter, I had no sealing ducting too or from the radiator basically the air was just wherling around in the front compartment and eventually some would make its way out. not ideal. I saw some improvements in temps but not much.

When I did my total tear down rebuild of my NSX I knew it was an issue that I wanted to address. Long story short, when I rebuild my splitter mounting points I also made sealed ducting to the front of the radiator then made and exhaust side scoop to seal with the vent in line with the the hood. This was done as much to aid airflow to the rear wing as to create a totally sealed flow path for the air. My temps dropped considerably, even still running the Koyo (whenever you're ready with those radiators Regan :] ) the rad is also covered with a stone guard and OEM fan shroud. Even then everything looks solid on water temps after long hot sessions.

OIl temps, now thats a different story...

I have had the Dali CF scoop, sold it not too long ago it was alright but the hood I have didn't scoop low enough to seal completely. There was about a 5 inch gap so I ended up just making my own. You wouldn't believe the heat that blasts out of the hood scoop when the fan kicks over after running a session it was enough that i gold foiled around the BMC as a precaution.

Heres some older pics. a lot of little details have changes since then these will give you an idea though

A first thing you can do is delete the "airtightness" you can have under the hood behind the radiator to create a flow that eliminates the heat there. On my (track only) car I have no more plastic trim with the gasket near the windshield. No overheating with undertray. But for shure a ducted hood is even better (efficiency and aerodynamic).

Will, I love your idea of gold foiling that corner to protect the master cylinder. I hope you don't mind if I borrow that idea.

asylum said:

A first thing you can do is delete the "airtightness" you can have under the hood behind the radiator to create a flow that eliminates the heat there. On my (track only) car I have no more plastic trim with the gasket near the windshield. No overheating with undertray. But for shure a ducted hood is even better (efficiency and aerodynamic).

Click to expand...

The base of the windshield is a high pressure location so you might be sucking air into your front hood and creating lift there.

A vented hood and proper ducting makes a huge difference. Depending on your level of fitment, the FXMD hood is much more affordable.

Also a vented hood does make some front Downforce so I would at a minimum run an nsxr rear wing when on track.

stuntman said:

The base of the windshield is a high pressure location so you might be sucking air into your front hood and creating lift there.

A vented hood and proper ducting makes a huge difference. Depending on your level of fitment, the FXMD hood is much more affordable.

Also a vented hood does make some front Downforce so I would at a minimum run an nsxr rear wing when on track.

Click to expand...

Do you have a picture of the FXMD vented hood? Their site isn't working for me. What is the price?

Who makes a vented hood similar to the Lemans NSX hood? Dali had a "big scoop" hood or something like that but I don't believe they make it anymore. Plus I don't buy from Dali for personal reasons.

For pop up headlights and a stock radiator, the largest vented hood I know of is a Marga Hills ducted hood, or the copy VIS made. Draw back is they are set up for RHD and will have an interference with the ABS system of LHD cars.

Otherwise, if you can find a copy of the RTR hood and are willing to modify the radiator mounts and get a new radiator: that's about as close as to a Le Man's NSX hood you can get.

Next best solutions based on sheer vent cross section area seem to be some NSX-R type hood or a twin ducted hood which exhausts the air "around" the windshield instead of "into" it.

I have the DF type R hood. I also have 2 different ducts that fit under the hood scoop to direct the air. I thought I'd install one or the other and keep whichever looked best but I don't track my car so I could probably sell one or both. PM me with your cell if you'd like me to send you pics.

jones83 said:

Do you have a picture of the FXMD vented hood? Their site isn't working for me. What is the price?

Who makes a vented hood similar to the Lemans NSX hood? Dali had a "big scoop" hood or something like that but I don't believe they make it anymore. Plus I don't buy from Dali for personal reasons.

Click to expand...

Here:

http://image.modified.com/f/feature...248/modp_1009_03_o+10_best_track_cars+nsx.jpg

http://image.importtuner.com/f/even...er-lap-battle-global-time-attack-FXMD-NSX.jpg


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stuntman said:

The base of the windshield is a high pressure location so you might be sucking air into your front hood and creating lift there.

A vented hood and proper ducting makes a huge difference. Depending on your level of fitment, the FXMD hood is much more affordable.

Also a vented hood does make some front Downforce so I would at a minimum run an nsxr rear wing when on track.

Click to expand...

Hi Billy,

Is there a site showing FXMD vented hood pricing?

Does FXMD also make the vented hood for pop up head lights?

Could you reuse the oem latch or must use aftermarket hood pins/latches.