rear mount radiator, intercooler on diffuser

[ManDogFish]

Hi,
with the z33, most of our weight reduction is at the back, worsening handling characteristics when the weight is reduced....

The main do-able and somewhat cost effective method I see for 50/50 weight dist along with 400lbs+ removed is to have a rear mount radiator, rear mount intercooler and rear mount turbo...

so, the spare wheel slot would get cut out, the trunk flooring gets cut out, steel struts get installed to maintain the rigidity,
a straight aluminum sheet angled upwards could be bolted in, pointing from the bottom of the back door to the middle of the rear number plate.

The radiator could be installed at an angle with fans, with the intercooler and rear mount turbo, all on top of a giant under rear bumper diffuser that helps the air flow through them. It should look epic as well...

My question is, for the handling characteristics, turn in, understeer, oversteer and how the car spins out.... the rigidity of the front and rear would be calculated and controlled...
do you think I would have any issues if I make the rear end too stiff and rigid?

if not that project I was thinking of locating the rear mount turbo in the spare wheel bucket and installing pyrex on top... so ill have the engine at the front and a turbocharger in the trunk, exhaust tips next to the number plate.... this question goes to the people who have turbocharged their vq35s, does the turbocharger get hot enough to cause a fire without being in direct contact with say a carpet 5 inches away with a pyrex sheet in the middle?

btw... the z is my DD, I am not gonna hack up the car until I either get my motorcycle back on the road or a second car

[BusyBadger]

As far as handling you could always get some aftermarket sways and test different settings until you came up with something that you were comfortable with. Hotchkis sways are 4 position adjustable in front (+22%,+48, +82%, +129% stiffer over stock) and the rear sway is 3 position +80%,+125%,+185% over stock). Cusco is two position front and fixed rear so you don't have much to play with there, and I don't know the specs for Whiteline bars, but I'm pretty sure they are three way F/R but I've got no idea of the stiffness increase over stock.

[ManDogFish]

ooo I did not know they existed. Looks like it would help

The part I was concerned about was that to make space for airflow for the rear mount radiator, I would have to cut out a part of the chassis at the back.
Assuming it as the worse case scenario, the back end will be u-shaped once I remove the muffer and fuel tank. The stock rear strut in the trunk would be there and so would be the bottom one. But the trunk in the middle would be cut out and rebuilt slightly higher up.

I have other minor projects in mind aswell but if they are done, the cars balance will be soo far off from factory that all the suspension will also have to be redone.

But yea, seems like the Z can be made to handle similar to an S2000, yes they are very different but
A stock Z base 04 is 3182lbs curb weight...that means including the fuel and fluids
3182 lbs 350z stock
-110 lbs fuel
-15 lbs washer fluid
-40lbs carbon hatch with
-35lbs spare wheel
-5lbs+ tools
-25lbs resonated cats
-35lbs (est) straight pipe with hayabusa mufflers
-15 lbs clutch, flywheel
-----------------------------------------------------------------------
3182
-280
-----------------
2902lbs, 1319kg

At this point the car would understeer heavily and also oversteer heavily. btw some s2000's are around 1300kg curb (inc fuel)

So this would take off around 210lbs from the rear and 70lbs from the front.
The stock weigh dist, 53/47; 1686lbs/1496 would be changed to 1616lbs/1286; 55/45 which is a little more like a subaru's 60/40 but subaru has AWD, we dont

like every other Z owner, I also want to FI my z but slapping on a 100lbs at the front of a to be 55/45 car wouldnt do it for me. So the only FI option for me would be rear intercooler rear mounted turbo.
The single turbo, intercooler and some piping should be around 70-100lbs. The radiator i am guessing could contribute 45lbs with the fan and fluids. A 25 gallon fuel cell at the rear end will probably add another 100lbs.
with relocated battery bringing us to 1571/1496lbs, -15lbs of the clutch are flywheel, if you run smaller rims and tires at the front if may bring it to almost a 50/50 dist.

and if not turbocharging, the weight dist should be around 1548/1352lbs ; 704/614kg. 20 gallon fuel cell at rear end, probably going to put on 30kg. so 704/644kg
one should be able to go below the 1300kg mark with some aluminum struts, lightweight 16-17inch wheels



the rear hatch weighs 70lbs!! Makes me think nissan had difficulty getting the car close to 50/50 and gave up at 53/47 for a mass produced car with the excuse that it turns in 50/50 on hard acceleration.

cuz i mean the hood is lightweight and aluminum and the trunk is 70lbs with a trunk weight inside it aswell

[jerryd1987]

you wont fit a 25 gallon cell in the rear, MAYBY some 20 gallon ones(trust me i know i have a 16 gallon back there) unless you have it custom made. if your that worried about it look for boosted performance he isnt on this forum but is on another, the entire kit weighs about 65 lbs with around 40-45 lbs of it mounted between the two axles to improve your weight distribution. you can mount your stuff in the rear but your diffuser idea isnt going to work because the car was designed very well from the factory and there isnt enough airflow under the car(especially if you have the engine compartment plastics in place. theres a reason stuff like porsche and lambos have vents to direct airflow. fans will help and MIGHT be enough if they run 100% of the time. as far as the turbo you dont want it in the car. my turbo is mounted about 5 inchs under the floor board about 6 inchs behind the shifter(no it dosnt scrape), it has a turbo blanket and all my exhuast is heat wrapped and still gets hot enough to burn me if i touch the silver ring around the shifter. my insulation is taken away but still the most you want to do is tuck the turbos up where the stock muffler sits and you do not want the turbo anywhere near the intercooler and radiator especially not in front of them or they will see huge heat soak.

if you go through with it i suggest you get the cf hatch and make vents to go behind the door windows and direct the airflow into the rear hatch area to flow through the intercooler and radiator. or go with a air/water intercooler in the rear and heat exchanger up front since it would only be about 5-10 lbs.

[ManDogFish]

if the reasoning for it to not work is that the car was designed so precise for air flow that air would not flow though it... then Im afraid that is not correct.
The car was not made to be turbocharged, the car was not made to be turned into an AWD version, the car was not supposed to have its weight reduced to under 1300kg, the car was not designed to take in an sr20det. Who ever did that did not think, hey nissan didnt design it for this.
Eitherway, keep in mind that there is a HUGE difference in cost effectiveness of mass manufacturing car design and backyard project car design.

I was ignoring the weight of the fuel cell itself and was estimating the mass of the fuel in the fuel cell.

I do think it will work though. Cuz high flow rad fans alone should flow enough air through them.

I was thinking if it could be made in a rectangular tube, with the rad in the middle and the fans sealed to the end of the end of the tube, it should flow well...

yes, there is the exhaust in the way. There are also the suspension bits, differential restricting the flow.
On the budget, for the exhaust all I am planning to do is ceramic wrap it. Maybe a heat shield on top.

The differential and suspension bits I cant do much about. What I could do is mount a 12" height rad at like say a 40 degree angle, further back to the end of the diffuser than near the spare tire bucket...to promote flow...


but yea, I am slowly researching aluminum radiators now. There are a lot that could work but I have not found the ideal one yet. I am also looking at the option of having a water based intercooler using the same rad.

The rear side window vents I thought about... but that would have been nice for a gigantic air intake box in the trunk that could feed it to the turbo in the trunk...but yea, I guess it produces too much heat to be in the car.


but yea, if anyone one knows a radiator that is less than 12" in height it would be useful to know.
Most of the ones in small height that I found are made for engines smaller than 3.5l. If I dont find one, I might have to use 2 small radiators side to side, the problem would be the stress on the water pump.
I could go oversize and use the same rad with a second pump for a water based intercooler...the issue again is height...

I took some rough measurements with the car on the hoist, I didnt take the muffer off so i might not be accurate but a lot more needs to be cut out of the chassis for a short normal radiator.

Im surprised at how cheap radiators are....compared to say a plastic plenum spacer...the aluminum rad is cheaper with the rad fans included. The spacer is a joke in the way its priced. You would realize if you had an idea of manufacturing cost, but then the Z33 parts market in North America seems small and the consumers do seem to judge the quality of a product by the price most of the time.

[jerryd1987]

i dint say you couldnt do it i said you would have to incorporate numerous things to make it work, your statement is a fallacy because people dint just bolt in any of those things and they worked it required EXTENSIVE reworking on the car the exact same would be needed for the rear mount systems. one of those extensive mods would be cooling channels and vents to capture airflow but sure ive never put my car into OpenFOAM to test my own aero so i have no idea on the cars airflow characteristics

go ahead though feel free to do it and ignore me but dont whine when im laughing at you because you need a new engine from overheating it and warped the block(which has been done in turbocharged applications on this platform with a 50mm radiator DIRECTLY in the airflow you really think a v mount in the rear will do better?) or warped the heads. like i said they will have to run 100% of the time enjoy replacing those black magic fans(or similar the fans just to match factory arnt cheap to do better your looking at $300 EACH)

if you have ANY sort of budget you arnt going to do this, i did JUST my fuel cell on the budget and i have about $350 in that and thats without trying to fit other crap back there. where your talking about placing the radiator and intercooler is actually where i was originally thinking you where going to place it since its the only place you would have room, theres not crap for airflow there expect to see about 5% of what you see at the front of the car.............and are going to see additional heat from turbo charging.

what i can tell you is you cannot go off any specs you read on websites because they are assuming you are mounting it at the front of the car you will need at a minimum a koyo 50mm, your going to HAVE to cut out the spare wheel well and it is going to have to protrude into the trunk area, you will HAVE to spen about $600-800 just on fans and have a custom shroud made.

if this was cheap or easy everyone will do it, guaranteed your looking at over $1k just in rad and fans if you go cheaper you WILL be buying a new engine but go ahead ignore me ive only built several 10 second cars(and the z on max boost and slicks is a 9 second car) tune my own engines, build my own aero with CFD software, build my own suspension..................well pretty much everything but machine work but yah no idea what im talking about totally just looking to give you a hard time.

[ManDogFish]

my bad for the late reply...
yes, u were right

it is a lot of work

I did try taking off the exhaust to see how much space I have to play with and how much stuff I can cut off to make air flow through...and its gonna be tough and not worth the money

I wasnt looking into 3D modelling, just a hack job
I was going to weigh each end of of the car to distribute weight in the build
use microphones under the bumper in different areas to estimate wind turbulence
but then I added a 1200W sound system and some stuff in the trunk to get 50/50 weigh distribution
and the car is significantly more tail happy, not a good thing when driving on snow with the torque characteristics that we have...
The airflow has to be almost 45 degrees to the horizontal axis and the trunk has to be cut out and rewelded a little.. at the minimum

a jeep 12" x 36inch radiator might have worked but the plan flopped

The budget for me depended on a lot of things... If it is a car that I think is worth investing into (like a 993 porsche, honda nsx, mercedes 560sec amg) and making it very very unique to the point that If I move to another country I would have it shipped with me then I would put all the money I could into it...sounds stupid but thats what works for me i guess
examples: centre steering porsche 911....

The problem with the 350z is that it can be traded in and with 5-8k on top you can get a 370z or a 335i...i mean its a good car, nothing very very special which can also be a good thing cuz then u dont have to worry about wear and tear to the car

but yea, Ill keep you posted is the project goes ahead

[kingbaby]

lots of man hours!

link to build thread