Guys,

Does anyone run the RB ram air duct on their SII? I am wondering whether the blocked off portions of the grille totally shadow the duct inlets. Does anyone have any pics of how it looks behind the grille? I searched and could find none.

Thanks!

 

Did you search? I have a thread on a R3 install somewhere. But it blocks a lot of the rad opening. Not worth it IMO.

 

I have one, and it seems to cover a big portion of it. I haven't actually looked at my coolant temps while on the track, but got an OBD2 bluetooth connector and will let you know if I hit any coolant temp issues...

For the most part, I drive the car hard until a light comes up or something happens... which... isn't the brightest idea.

That being said, if you're driving around on the street, I can't imagine it being that bad unless you're driving in the desert at 115*+ all the time.

Never drove the car with the intake without the ram air duct though, so can't tell you the difference with / without it.

 

Also - to answer your question, I believe most of the duct is NOT behind the blocked off portions of the grill. I'll try to take a picture of it tonight when I get home.

 

I asked Brian Goodwin about the blocking of the radiator before I purchased that. He, at least, indicated it wasn't a problem.

 

Yeah well he is trying to sell you a product also.

For this particular R3 it was never an issue but it was never tracked either. Either way it is a pretty pointless mod IMO unless you come across one used or something.

 

It is a useless mod. When the car is moving, the intake air temperature is the same as the ambient air temperature. And, the duct does nothing to measurably increase air flow. All it does it add weight and potentially block flow to the radiator.

 

Gentlemen,

Thank you for your responses and opinions. It is pretty clear the stock grille is not an obstruction, except in the very center. However, the radiator airflow issue that you brought up is a concern that I had not fully considered. I would choose get the duct for the 1-2% improvement in airflow, but not at the expense of cooling.

A little backstory:
I am getting the RB oil cooler screens as Step 1 of addressing cooling issues on my 8.
My daily commute takes me up the Cajon Pass (roughly 12 miles, 5-6% grade, highway speeds), and the only way I can keep the coolant temp from going above 220F is to stay in the slow lane @ 55 mph and AC off. Oil cooler fins are pretty messed up, so I'm going to try straightening them up to see if it helps. The screens I should have put on long ago I was thinking of installing the ram air duct while the bumper cover is off, but I really don't have any cooling capacity to spare. Maybe sometime later, when I have a good cooling setup...

 

That's what I figured and given the cost decided not to bother when I recently ordered the RB intake. Have you measured or seen any air flow numbers though?

 

Straightening the oil cooler fins is a good idea but you should not be having cooling issues like that if everything is working properly. You may want to spray out your oil coolers, condenser, and radiator using good strong degreaser. I am not that familiar with the area but I off-road a lot and it is fairly common for guys to overheat due to their radiators getting clogged with dirt and dust. If you live is a high dust.dirt area then the condenser or the radiator could be partially clogged. I remove my condenser and had it removed and it was filthy.

I recommend these flat tip tweezers for straightening the fins. They work much better that the radiator fin tools sold.






You can get them at harbor freight, they sell an assortment.

 

You can see here where I repaired the fins on this cooler. I had it tested and sonic cleaned at a radiator shop after.

 

I have not done anything more than run some quick calculations. There is nothing in its design that would increase pressure or flow rate. So, its only benefit could be temperature reduction, but we have observed that IAT tracks closely with AAT (certainly within the tolerance of the sensors), therefore there is no benefit there either. You'll notice RB makes no claims about its performance on their site. From a reputable vendor, that usually means there are no gains to be had.

 

At 100 mph and standard sea level atmosphere the airflow dynamic pressure is about 0.18 psi. Not much, but enough to theoretically increase stagnation pressure inside the airbox by 1.2%... so good for maybe 2whp? IMO not strictly correct to say there are no gains whatsoever. Of course, maybe under the bumper the stagnation pressure is higher by virtue of how air flows through the bumper... No way to know for sure, without putting pressure transducers inside the airbox and under the pumper, or doing CFD with an accurate model.

I looked at your intake temperature results from the track in the Radiator thread, but on my car the intake temps are always at least 3 deg F higher than ambient, and when the engine gets nice and hot, the delta is more like 10 deg. On the aforementioned uphill climb it can get to +15 degrees. So it definitely seems to me like a cold air duct would help, although I wonder how much of this is due to heat soak of the airbox/accordion tube. My OBDScope app has a PID for ambient air temp, but it doesn't match the temp displayed on the car's LCD, and just seems to be the same as the intake temperature, down to the 10th of a degree.

 

I have not done a direct compare of data from the air temp to the MAF temp sensor, but just observing my MAF temps they appear to be pretty close to ambient when running on track and so in line with what Steve is seeing.

Jastreb, are you running in traffic, or at low speeds? I'd expect the temps to equalize within a short time of getting on the throttle. At idle, or low amounts of throttle, then you will get heat soak through the airbox and intake

 

I was comparing the MAF temp sensor reading to the outside temperature display. This is running 65-75 mph at 3-4k rpm on the highway, after an uphill climb.

 

True, but he's also one of the vendors that I've come to trust a great deal. I've communicated and purchased from him for quite a few years. I've learned that they don't sell products they don't feel are worth the money, and they personally test at least most of what they sell. I've also come to have a great deal of faith in Racing Beat. I don't think anyone here expects anything more than a couple of horsepower and some sound from any of these basic modifications on this car. I also don't believe that either Racing Beat or Good-Win-Racing would bother with the part if they didn't feel that it offered some small gain under the right conditions. From years of communications with both Brian Goodwin and the guys at Racing Beat, I feel pretty confident in that statement.

 

Even if your best case scenario is correct with regard to pressure, ~2hp at high rpm at 100mph is virtually nothing in the real world to 99% of the population. It might make a difference to someone in a competitive situation, but not to anyone else. It is unprovable fringe, since it cannot be measured.

 

No way to measure it, you're right about that! The real question is: does it make the driver feel better?

 

I'm on board with Chibana. I've used RB products over the years in my rx7 and my rx8. Always impressed by the guys who work there and how they run their operation. Have done a few tours of their facilities and nothing short of quality stuff.

Could they try to hoodwink us with useless items? Sure, everyone could. But I don't see them risking their reputation on something completely useless for a few bucks here and there.

 

Here are the temps for my morning commute. This is with the RB Revi intake and without the ram air duct. So there is a difference of a few degrees between ambient and MAF temps. 5degC in my case at 65-70mph on relatively level freeway. I would expect this to drop to 1 or 2 degrees at most if I get on the throttle for any period of time. You can also see it increase once I come off the freeway at the end of the drive.

 

Your data tracks somewhat differently than data I logged last month at the track. My IAT was about 2F higher than AAT. Your IAT seems to fall victim to heat soak when you are not on the freeway. I don't have those data for comparison, but I'm sure my chart would look similar. Perhaps the RB duct could help in that regard. There is only one way to find out. Then again, how much would any small difference actually make in the real world if one is not participaing in competitive motorsports?

One thing we can't know is where each sensor sits in terms of tolerance. Sensor tolerance will have some impact on how closely IAT matches AAT.

 

I expect my on track temps track similarly to yours, but I don't have the exact ambient temp data to compare yet. Next month...

Here's what IAT alone looked like for me over the first lap on a warm afternoon with the stock intake and radiator. I don't have the exact ambient temp, but it was over 80F that afternoon. Basically as soon as I open the throttle IAT drops quite quickly, it is then within 5 degrees of ambient in half a lap and then stays there for the remainder of the session.

 

The screens will actually reduce airflow and you said nothing about oil temps. Are you sure they're a problem? For more airflow, try opening up the fender liner behind the coolers, like this (also see page 3 for a better version): https://www.rx8club.com/series-ii-di...-15%25-168650/

Also, you can try stuffing some foam around the sides of the coolers to make the air go through the core, rather than around it.

For water cooling, you can also try improving the seal around the radiator and cut out a bunch of the blanked off grille sections for better airflow.