Track car development update - surge tank, splitter

[JohnJL]

Had a chance to do a shakedown day last weekend and was pretty pleased with the car. Over the winter I;

- rebuilt the motor, and while I was in there had Xtreme Cylinder Heads install 53mm intake valves and port both sides

- fabricated a removeable engine mount on the driver's side so I can drop the whole motor with the supercharger installed.

- made up a surge tank system for the fuel. I had fuel sloshing in the corners and on a low tank the motor went lean and detonated all the cylinders. The system I built is essentially a 'dry sump' system for the fuel in very much the same principle as our oil system works.

One A1000 pump feeds a surge tank, another A1000 pumps from the surge tank to the fuel rail. Those are balanced and return to the regulator, which in turn feeds the surge tank. The surge tank has a top fitting to return surplus fuel back to the main fuel cell. Filters in all the right places.

The motor started on the first turn, no joke, that never happened for me before. Upping the fuel map by 10% to compensate for the bigger valves and cams was just about right but a day worth of logging gave me a lot of data to refine the map. The challenge now is getting the idle down, it just likes to idle at 2,100 no matter what. Big cams and boost makes it challenging.

Cornerbalanced the car and got it to 38% front/62% rear weights and the cross weights to the pound.

I have the struts maxed inwards on the tops with elephant monoballs but cant get more than 1.5deg camber. The strut braces I have are too long, there isn't any thread left on the rod ends to make them any shorter. 1/4" toe in on each side on the front, .1" toe in on the rear, 2deg camber.

Front tarret bars on mid, rear bar is full-stiff. I had to roll the rear fenders a lot, I was getting bad rubbing on the hoosier R6s.

I was supposed to be at the track again tomorrow but as I was doing the oil challenge today the drain plug in the engine sump stripped out. It was one of the aluminum ones from the host. I have a GT3 oil pump in the motor so I need the concave sump and I don't have one on any of the other cars so my day at the track tomorrow is a bust.

So I started the process of making a splittter tonight. I picked up a 4x8 sheet of 6mm ABS yesterday and started mocking up placement tonight. The idea is to have 4 quick-release attachment points plus 3 turnbuckles in a way I can install and detach it myself in less than a minute. We'll see...

Anyway, enjoy the pics...

[JohnJL]

Had a couple of hours in the morning to work on the splitter.

First I did some research on how far I wanted the splitter to extend from the RSR front bumper. I've3 been collecting photos of splitters for a year, including a bunch from the Porsche museum and Autoworld museum in Brussels. Along with some articles by Simon McBeath, I settled on 150mm as a starting point. I can always trim it more later.

Simon McBeath Splitter and Diffuser article

I want to be able to pull on and off the trailer without removing the splitter, so I started by measuring the angle of attack on the extended rams to the beavertail on the trailer. At 35", which is where a 15cm splitter would extend, from the front wheels I need at least 2.5" ground clearance. I also want to be able to keep using the kerbs so I kept that in mind when mocking up the splitter.

I drilled 3 pilot holes in the car, two back towards the driver on each corner, and oneat the very front of the frunk. I then transferred those holes to the splitter and temporarily bolted it in place. With it hanging on its bolts I played with the height until I settled on 4.5" as the clearance between the splitter and the ground. This left 3" as the height of the air dam or fence I need to attach to the splitter to meet the bumper. It also leaves me 1.5" of up/dwn adjustment for later by threading more of less of the rods and turnbuckles.

I played with the shape of the buttresses I plan on glueing and screwing to the main splitter to support the air dam/fence. I settled on 2.5" high, 4.5" long with a cutoff on the acute angle to accommodate a clamp later when heat forming and affixing the dam. I cut out 12 of those and need to dress them up a bit with a sander.

The plastics shop where I bought the abs and solvents said to use a fine tooth jigsaw on the abs, but I found that built up heat and the pieces just sealed together again right after the sawblade. Instead I found using a very sharp, course wood jigsaw blade an pushing it very fast through the material resulted in muck less melting and a cleaner cut.


Tracing the bumper for later installation of an air dam when the splitter is lowered to finished install height.



Tracing 15cm out from the bumper.





Note the levelling shims under the rear wheels. I suspect its important to have the car level when checking the ground clearance of the splitter at that also should be at or near level.



With 2 of the three hardpoint attachments installed.

[a930pilot]

made a similar splitter out of SS and have a VERY hard time getting it onto an open trailer (with 4' dovetail). It does NOT drag on my driveway surprisingly. I'm starting to wish I had made it out of ABS like you, but the SS does look nice.

[JohnJL]

Originally Posted by a930pilot

made a similar splitter out of SS and have a VERY hard time getting it onto an open trailer (with 4' dovetail). It does NOT drag on my driveway surprisingly. I'm starting to wish I had made it out of ABS like you, but the SS does look nice.

Nice car, are those Fikses also?

My trailer is a low-rise, with a 7' beavertail and 6' ramps because I planned for this exact issue.

[a930pilot]

Thank you! Yes, they are Fikses and the valence is from GT.
That 7' tail must be a big help. I had to make 4' wood ramps that my 6' trailer ramps sit on.
FYI - I ended up with quite a few bolts (10?) holding the splitter to the lower lip, but didn't build in the adjusters that you have. Mine would take forever to take off.

[JohnJL]

I love your wheels. I think I havethe same fikse's I like the black look on the track, but I really like how they look on your car. Nice color too.

by the way, I imagine a ss splitter with some minor rubbing it gets quite sharp.

Does your car have a name? Because I'd propose "Die Kopf Einchornchen." Which roughly translates to "the headless squirrel" which I imagine there are a few in your neighborhood!

I like it, nice job

[Kozmo930]

sent you PM about specifics ...

Thanks Kozmo

[JohnJL]

Progress...heat, glue, screws, clamps, drill bits...

[saxen]

More pics please