Getting it all working pt.2

Ok, im back to finish pt.2 after a slight delay, ill just pick up where I had left off. 

 

Now that I had all of the transmission stuff sorted out and working I drove it a few times to work to make sure-sure the simplifications i had done had solved the CEL and limp mode issue. It did.

The next few things on my list were going to be some low hanging fruit on the aero side of things.  I pulled my old Gurney tray and flap out of the basement that was originally used on my CRX, I was going to make another one in carbon but on a whim decided to see if this on would work. It turned out to be the perfect dimensions I needed for the ISF. I decided to modify it where needed and reuse the part I already had instead of making another one. This sub wing is EXTREMELY light and rigid, maybe less than 2/3 of a pound and can easily support 100lbs of weight. I decided to be able to get it to the optimum length under the wing i'd need to slightly notch it for the aerocatch latches.

Once I had it mocked up I market it then epoxy'd it in to place with an added couple of rivets to mechanically hold the front edge down.

 Ideal angle for a sub wing can vary depending on its proximity to the main element, in some cases when the two are closer together you want a small 'kick up' on the sub wing to add or promote the velocity of the air flowing along bottom of the main wing. In my case the separation of the main element was sufficiently large enough that the main benefit of this sub wing here was going to be much more of a drag reduction device. Its job would mainly be to smooth the turbulent eddies coming off the back of the trunk and allow less turbulant/draggy air to exit off the back of the vehicle. The ideal position of a sub wing in this case is something much more level with the ground and in line with the flow. I used some aileron turnbuckles for supports so id be able to fine tune adjustments on the sub wing as I changed the rake of the car with tire size or height adjustments.

To help the looks I also added a curve of flat black vinyl. It helped to break up the blocky shape and return the visual cue of that curved trunk. This made the tray visually feel shorter and went a long way to blend it into the overall appearance of it on the car. Once happy with the placement I seam sealed the transitions with slicone to add some finish.

I also added carbon spill plates in a effort to keep as much of the air on the top face as possible.

After I finished with the trunk I moved onto the front cowl. Lexus had done a really good job shaping this area from the factory and actually recessed the wipers nicely under the hood. I wanted to take it a step further and seal the area completely. I removed the wiper arms and put them off to the side in case I want to drive a few rainy track days in the future. I then cut 2 pieces of carbon on the curve of the windshield and fixed them into place. This area now sits flush with the hood and has a smooth path for the air to flow over it. Having seen these mods done on other cars during wind tunnel testing I was always surprised by the resuts of something so simple. In my case here i'm sure theres been a positive reduction in drag as well as an improvement to the existing aerodynamic elements efficiency.

After these mods were done I took the car out again to Chuckwalla Raceway. It was a Saturday/Sunday event and I'd originally only signed up for the Saturday. I found that during the Saturday event I was now having problems with understeer on a few corners where i hadnt before. After changing the usual shock settings and wing angles, it got a bit better but did not go all away. Towards the end of the day I decided to remove the gurney flap off of the rear main element that id added a few events back- I did half a session at the end of the day before it got black flagged for some oil down, but I knew that the balance was back in the car. After some contemplation I decided to stay overnight for Sunday to see if Id be able to improve like i thought I should be able to. Up to this time I was siting at a 1:54.3 going clockwise. I really wanted to dip into the 53's and I knew it would be possible if the desert gusts stayed low until after the first few sessions.

Sunday morning came and I was up bright and early for the first session. The day before I was also getting a sparatic fuel cut on a couple of the lefthand corners of the track. It seemed I was now pulling enough G's to fuel starve the pump on long lefthand corners. When this would happen a sensor in the fuel rail would see the low pressures and cut power from the pedal until it came back. I had been riding ta fine line trying to figure out where i would be 'ok' to fill it too fuel-wise in order to not have the fuel surge cut intervene. 

 That Sunday morning was calm and cool and I was pretty sure I'd filled up to a safe point to not get the cut. I went out and on my first session and immediatly got the cut, lap felt quick too.  I was so pissed at myself for trying to ride that line and just not filling it all the way to the brim in order to not starve the rails. I pulled back into my pit spot. I hopped out took my tire pressures and started to back calculate the time remaining in my session and how long i'd need for an outlap and flier. After dong the math I realized I was out of time, but the next session out would be intermediate, a slower group, but I was pretty confident i'd be able to find myself a gap for a clean lap. The wind was still calm and I knew that this would probably be my last chance for the weekend. Just then I rememnered that the day before I had been given an instructor wristband which meant that I was able to go out in any session running on track. I quickly made up my mind- and with my helmet still on I used my gas jug to top off the tank and buckeled back in. I got to grid right as the last intermed car was released from grid. I had them hold me to 20 seconds and send me out. As long as no one in front of me had a mechanical issue or went off and yellow-flagged a corner I would be able to put a fast one down.  

 

Here's how the lap went;

https://youtu.be/CJAAoKwyQmk

I ended up with a 1:53.4. Tires felt like they were inside their window and Id avoided the time killing fuel surge cut. Being on the low side of a 53's feels like a huge accomplishment for me in the car as it was one of the ultimate goals when I started the build.  By achieving it I had confirmation that I was moving in the right direction.

 Can I go faster at Chuckwalla? Yeah. Realistically it all comes down to the weather and track conditions there. If I had another cold morning and I was on a fresh set of tires im sure i could take another couple tenths off. However now that the car is getting to the point where im not making large changes, rather only tweaking what i have, going faster is going to be more of an incremental process for sure. 

  Moving forward. 

Another thing that I'd wanted to do was put together another hammer head design splitter similiar to the one that I had on my CRX. The normal one I had on the ISF already was working (obviously), but having had understeer issues the past weekend I wanted to see if I'd be able to add down force on the front to balance it instead of taking down force off of the rear. I'd been kicking around this idea for a while and decided to take a crack at it.

 I did a lot of measurements and cut a few templates out of the large carbon/armid cores sheets I had.

Once I had some the blanks cut I picked up another set of splitter diffusers from Amir at RS Future. I peel riveted and bonded them on then sealed the seams and transitions with silicone.

I also added some RHR end fences I had laying around

and added a slot gap to them, I have heard and seen some CFD simulations where this promotes localized down force and increases the efficiency of the splitter and diffusers due to their proximity.  I have also heard its not doing much. Whatever its easy enough to do, test, and remove if it's not doing as i hoped.

I also sealed the cut edges of the honeycomb on the blade to ensure its sand/waterproof then also took a pass at sealing all the small gaps and cracks on the front bumper. This was as much to finsh the look of the car as to stop air leaking which increases drag and lowers aero and cooling efficiency.

Hard to tell in the picture below but I also sealed the gap between the lower lip and the bumper.

 

 

To seal the bumper to splitter transistion I ran a strip of EPDM which i nyloc bolted to the lower lip, the air pressures at speed will push it down and make sure it stays sealed to the splitter.

Another large factor in wanting to build this new splitter was I wanted to engineer something that was even lower than my current one was. Generating downforce from a splitter has a lot to do with its distance and interaction with the ground.  Bernoulli's principle describes that differentials in air pressures (driven by the speed of the air) is what actually creates the force on something like a splitter. Sure there is a slight amount force that is generated from the air piling on the top surface in front of the bumper, but that is less that a quarter of its DF potential.  

In rough terms; pressure differentials create forces, to create pressure differentials you need to set up a mechanism to induce different air speeds where you want them. In my splitters case, I want the air moving under the car to be going as fast as possible to create a suction.

A non cambered surfaces ability to create downforce is effectively controlled by how far away it sits from the surface plane of the floor. I have read literature that says the same exact underbody and splitter lifted as little as 1/2 inch can lose up to 30% of its downforce potential. This happens for various reasons- but the major one, like I said, has to do with the interplay in the speed the air when its forced into a a smaller slot. Lowering the splitter creates more air speed.

The trick is to create a reliable gap size somewhere in this 'happy zone' where the amount of flow stays relatively consistent. Too low and the pitch and dive of the car on track will choke off the air going under the splitter and cause a disconcerting feeling that the front aero grip is being flicked on and off like a light switch. This would obviously be not good, especially on corner entry where the majority of the pitch and dive occurs. Looking at the front splitter in terms as a counter balance for the rear wing understeers becomes even worse becasue its no longer matched with the rear wings force. You lost the front grip right when you needed it most. 

After looking at my shock potentiometer data from previous events I was able to tell, on average, how much my car was pitching and diving while on track. From there I could use basic math and geometry to extrapolate about how much lower I could safely drop it and still maintain a reasonable height off the ground under the majority of situations. Once done, I'd have to rely on shock pressures and spring rates to maintain a stable height and air gap but, still allow for the shocks to compress as needed.

This is where cars that have been "set-up" shine over cars that are just "put together" and exactly what i mean when I said i'm now moving onto "tweaking" the components I have vs adding more parts to the car. 

Something can be infered here for people or shops that build cars for events and only get them rolling a few weeks before or only ever bring them out once or twice a year. There is a whole world of tuning potential left on the table by not developing through consistent iteration.

Now that I have the basic blade designed on the car I put surplus ailerons rods on the front to stop any deflection at speed. I had Kristian cut and weld them up to the exact length i needed.

Test fit was looking good.

Now that I had lowered the splitter I wanted to smooth the step down transition back to the height of the floor

I got a 3/32 piece of carbon and measured it out.

I used a piece of 3/8 honeycomb core and sandwiched it between the carbon and the engine pan. I then used angled washers to create a cambered wing shape to create a mini diffuser that measures about 19"x9". This is a pretty large surface area and i'm glad i could take advantage of it in this way.

 

 

You can see the transition here. I also added clear poly carbonate fences to keep the fast moving air from spilling down into the wheel wells then helicopter taped everything that wont need to be coming off anymore.

Now that it was coming together I put the car on leveling plates and adjusted the splitter angle using the adjustable rods that I'd had welded. A slight angle down attitude is ideal.

For my finial idea, and one of the main advantages of a hammer head design, I wanted to take advantage of the air hitting the front face of the splitter at a perpendicular angle. This is more advantageous in many ways on its own, but I wanted to increase these advantages as much as i could.  Profiling the flat leading edges of the splitter would make them low drag and also speed up the air even more. I got some delrin-90 and used a flap disk on my angle grinder to slowly and carefully shape runs of wing profiles.

 These would then be affixed to the flat leading edge of the hammer-head splitter to smooth the flow and increase the speed of the air even more.

 After mounting them and attaching some aluminum skid pucks it was all looking pretty good.

I had a track day at Streets of Willow with the new splitter to get data and make sure it was all staying together. video here:

I ended up running a few of 1:21.1's (which was a new car PB for SOW) but I was now dealing with the fact that the track surface was getting so bumpy and bad that I was basically smashing my new splitter set up over the jump in the back straight on every fastlap. Out of equipment preservation I decided to call it quits. Getting a flat tire on the third session didnt help either. I'd apparently run over a bolt or something that had fallen off of someone else's janky racecar. At that point I had enough data to be able to tell I was heading in the right direction.

 Streets of Willow is NOT an aero track but I was able to tell that the new splitter was making changes for the positive. Below you'll see a red line and a blue line. The blue triangle and value mark the low point of the cycle based on 200mm potentiometers. The red triangle is the max extension point and the white triangle is the average. These graphs are for the front shocks alone. Top (blue dot) values were form a previous day i'd done in the car at Streets of Willow with the old set up. Lower (red dot) is for the sessions i did with the new splitter. In short, 2-3mm of compression on the same 18kg springs equates to quite a bit more downforce up front.

A bummer was after I got home I realized that all the bashing had pushed the splitter rod mount into the blade.

I cut and shaped some carbon foot blocks and added then to the topside of the splitter. I also filled the gouged cavity with epoxy to harden it against this in the future.

I had another day scheduled to run at Streets Of Willow again in a couple weeks and had gone back and forth on running the new splitter set up. In the end I actually opted to go back to my old blade anytime I was going to run at Street. I didnt want to raise my car and I didnt want to just do lap after lap of of smashing the new one into the ground so just swapping the old one back in was the easy move. Again, since Streets isn't a big aero track i didn't think it was going to be the determining factor in getting into the 1:19's. I did however make some shock pressure and rebound adjustments based on the data with the new splitter.

Since the start of the summer I had wanted to add an air divider to the intake scoop, it seemed to me that the water temperature was running higher than it had done before so while I was changing everything back to the old set up I figured it was the perfect time to do the work.

I marked and cut some aluminum sheets to flow air up into the higher parts of the radiator. When building the initial set up had decided to block off the upper radiator grill to reduce drag, I now suspected this was was the main cause of the higher than ideal water temps on hot days. I wanted to see if now i could add diverter ducts but continue to get away with just the lower opening.

 

 

 

I brought it over to Kristian for a quick weld up

 

Once they were welded in I added some oil and transmission cooler protection to the back  edges if the fins and reinstalled it on the car along with the old splitter blade.

Diverters in place, I was ready for the next Streets of Willow day.

Here's how the fast session went:

The car was faster no doubt, even with the older tires.  The rebound setting changes made for a much more snappy car- which was good for weight transitions, but I had to be really really quick on catching the fast throttle oversteer. 

I ran two 1:20's back to back and my quickest was the one with a massive off throttle moment in the back esses. Had I not boinked that lap I could have easily reached of my goal of 1:19's that day. Unfortunately for the rest if the day sun heated the track and it was quite obvious it was then outside the window for a PB run. 

You can see the laps below of session 1 and 2 broken down into sectors- the back esses sector that I dropped 2 wheels is the second one down in the first block of 'absolute split times' I lost 6 tenth due to that alone. So close..  Other than that you can see the car is running fast and consistent. I just have to get it all working at the same time to achieve my Streets Of Willow 1:19 goal.

 

 After the fuel cut issues at Chuckwalla the few months back I'd really started thinking about my options for a fix. As far as solutions, there was a few that would likely do the trick but I needed to see exactly what I was dealing with before I ordered any parts. Working on fuel systems- for obvious reasons isn't typically that fun. It's smelly, dirty and potentially dangerous work, it also normally requires the car to be down for a while and new gaskets, hoses and connectors be purchased for everything that comes apart. I made sure that I didn't have any events coming up for a few weeks and decided now was probably the best time to get this sorted out. It also just so happened that the next track day I had scheduled was back at Chuckwalla where the fuel starve issue was most prevalent. Once I had a solution in place i'd be able to test it right away.

I first drained the fuel tank so I could get a good look at what I was dealing with. The OEM tank is a saddle tank with a 1/2 of the volume sitting on the passengers side and the other half on the drivers side. It has a single low volume pump that feeds the cam driven high pressure DI and PI pumps up at the motor. Its pretty smart. The low volume in-tank pump working at low pressures does not heat up the fuel or need to be overrun dry which can cause failures. Most of the heavy lifting in the system is done up at the motor. The way the fuel gets from one side of the saddle over to the other is with a venturi "jet pump". It has no moving parts and uses the in-tank pump output flow to drive a venturi that creates suction and effectivly siphons fuel through a hard pipe pick up on the passenger's side. The passenger side fuel is drawn up and over the hump into the drivers side where it can be sucked into the main fuel pump sock and integrated filter. It's a quite compact and clever system and it actually works very well, even with a high G capable car i don't suffer any fuel cuts or starves outside of pretty specific circumstances.

There are a few ways to tackle this kind of thing, one would be to re-engineer everything by starting from scratch to solve the problems.  The other would be to piggy back on top of the OEM engineering to fill in the gaps where needed. It seemed to me that the OEM stuff was already prety good, i'd just need to help it along in a few circumstances.

Heres a picture of my super high-tech fuel removal set up.

 Once empty I was able to see how muvh room I had to work in. It wasnt much.

   The service hole on the passenger side are extremely small, were talking like an inch and a half max so it doesn't offer much room to be able to work to add an additional pump or fuel sock. The main pump service hole is a bit bigger but the OEM fuel pump and hanger box has a few key features integrated into it that make engineering a replacement a bit more difficult.

I came up with two blank sheet solutions and sketched them out, the first one was how to do it with an external draw pump with an integrated hydramat.
This set up made sense for a few reasons but was lacking in a few other areas. Mainly would require a custom fuel tank topper disk to be cut and fitted with a a fuel float locator. I would also need to run an external Fuel Pressure Regulator and filter.

The second solution I came up with was to use the stock pump housing, fuel filter and FPR but run everything into an external sump system. This is a great solution and would 100% solve all fuel starve issues.

 

 The down sides are the amount of parts required (2 pumps) and how much complexity is being added in additional lines and fittings outside of the tank. This is something to be considered. The OEM manufacturer spent millions and millions on R&D to make a pretty bomb proof fuel system. I like the peace of mind that the fuel delivery in my car is all stock. My personal rule is if I modify anything in a racecars fuel system outside of the tank, I have to wear a fire suit. This is something i don't want to do in my ISF if I can help it. I dug around in my million dollar box of fittings and found almost everything i need but decided I'd think it over for a few days.

After weighing all of the options I decided to try and OEM + system. I would leave everything outside the tank stock and see if there was a way to help fuel pick up at the pump itself. 

I've use a Holley Hydramats in other racecars in the past with great results so I wanted to see if there was a way I could adapt one in my ISF. If you don't know what a Hydramat is check out this quick demo-

 

It's basically a super wicking sock that can draw up unaerated fuel when only touching a very small corner to the liquid. I ordered a new fuel pump and fuel filter as a matter of course. Mine didn't actually look horrible but this is always a good "while you're in there" type of thing.

 

For the pump I ordered an AEM 50-12210 its literally a direct bolt in pump to OEM with a slight boost in the LPH flow rate. This would create a good bump in the suction to increase draw rate of the siphon jet pump.

 

I next disassembled the fuel hanger too see if there would be a way to adapt a hydramat. You can see in the picture below the oem pick up location with the orientation in the car noted.

The pump sits directly on top of the sock and draws fuel in through the holes in the housing the submerged sock requires fuel feed from the marked area below Threes small holes, one large hole and the dot representing the fuel pressure/main valve bleed-off then finially the curved aero representing the jet pump draw.

All this is good under most conditions but you can see how a hard left hand corner would load the fuel against the fuel tank where gas would have a hard time reaching the pick up. This is what i suspected to be at the root of my pick up problem.

I poked around and took some measurements. I found Holley makes a hydramat for an 11mm pump socket which turns out to be exactly what I need to clip into the fuel pump. There's a couple size mats available with this pump connection size so I made cardboard templates out of each and begin test fitting what would work best in the tank

 You can see the tip of the venturi pump straw peeking inthe top here. Turns out an 8x3 was pretty much perfect for the spot.

 

 

After a lot of measurements to get where the housing would center the sock i verified it would indeed be centered perfectly inside the tank 

 

 

Now that I had my mat I would just need to modify a few different parts of the OEM housing to get the sock to work, it was all pretty straight forward. I first trimmed the main valve and retainer clip off of the pump retainer clip.
 

 

So now they were both divorced from the fuel pump retainer.

 

Then i sized the new hydramat clip and trimmed the clear retainer disk on the new fuel pick up.

 

Once that was done I clipped it all together on the new filter with the new pump.

 

 

 Next I moved onto the housing itself. I trimmed out an channel for the mat to rest in. Luckly it was laid out in such a way that I was able to avoid cutting any substantial structure out of the filter housing. 

 

 

Once it was all cut it took some tricky assembly to get everything routed correctly. 

 

During this time I took an extra hour or so and used a jeweler's file and Dremel to smooth out all the edges on the housing. Again awkward, but afterwards I added new o-rings, the float and hooked up the new siphon pump. I attached the Hydramat retaining disk into the pump and clipped the whole shebang together. There is no weight resting on the mat itself because its suspended by the retaining ring on the bottom and hanger mount on the top of the fuel filter housing, just like stock, but better.

Next it was carefully angled into the tank, new gaskets added, and all sealed up.

Now that that was sorted I got the car ready to get back to the track.

New splitter went back on the car and I also made some shock pressure adjustments on the front end again. After the last time at Streets of Willow I was looking at my shock histograms and seeing that the front left may like more pressure than the front right irregardless of ClockWise or Counter ClockWise running.

I bumped the nitrogen pressure up slightly and was curious to see the difference it was going to make on the shock histrograms.

 

 

By this point, the tires I was on were about 5 or 6 events old and past their prime. I wasnt expecting any PB laps, all the same I was excited to see what the changes I had made had done. 

I think I ended up running a best time of a 1:54 and a bunch of 1:55 as the tires started to fall off more and more.

 

All the same I was collecting good data. After a session I'd come in a pull down the shock data and run a histogram report. You can see in the screen pictures below I was able to dial in the shocks to the new front splitter and landed on almost unheard of 25% split in low speed rebound, low speed compression and high speed rebound and high speed compression. In other words, through the course of a hotlap the shocks now spent equal time in all four quadrents of their range. This told me that it was now in an ideal state of spring rate, nitro pressure and valve settings. 

You can see on the bottom pink histogram that the  Rear_Left can most likely use less compression and less rebound. These are all of course moving targets and would change day to day depending on tire life, overall surface grip and temps.

The MAIN takeaway from the event was that the fuel system upgrades were found to do the trick. They were 100% effective against the fuel starving I was seeing before. On the same corners with the same lateral G-loads/speed and revs I was able to run the tank down to less than a quarter and still did not experience the fuel starvation as I was before adding the fuel mat. 

  I took a slight chance going with this approach and it paid off. It was by far the cheaper option, and I left everything OEM except what was going on inside the tank. This meant no additional complications as far as non oem parts OR the additional weight assiciated with half a tank extra of fuel to keep the car from sputtering.  Since I'd be able to start a session with half the amount of fuel as I was before, I could save substantially on my 'race weight'. Half a tank less fuel comes out to 53+lbs i'd not have to carry onto the track to keep the issue in check.  Now im going to use the half-way mark as my default fill stopping point before sessions. Not bad for some dremel work and a couple hundred bucks in parts.

I threw it on the scales to get the new 'race weight'. The car was not on leveler pads with the swaybars removed so the cross weight wont show up as 50/50, but it is. 3571 with driver isnt bad.

 One thing that didnt work was the front air ducting. After looking at tempatures from the last Chuckwalla day I decided that I wanted to modify the radiator duct and re-add the upper bumper duct. I bent some metal and shaped it up to allow for the oem grill to fit into when installed.

Once I had the dimentions I trimmed the duct hole and affixed the new duct pieces.

This will more draggy for sure but weighing it all out, Id rather have a car that runs cooler for more laps and be able to be driven all year around. 

You can see the flow was increased by around 40% or more.

I took it out again on some well used take-off tires from the basement to a 100+ degree day at Buttonwillow to see how it would do in the heat. Cooling was much improved and I ran a few 1:53's in the heat before cording one of my front tires.

I did have a reccuring 02 sensor failure code and on the drive home I noticed that the inside of the cabin had started to smell like exhaust fumes.

both of which I had seen and smelled before. It was my suspicion that the header to exhaust crush gaskets were leaking and causing the weird air/fuel readings. I pulled off the exhaust swapped the 02 for a new OEM unit and threw in a new MAF sensor. I also swapped both the the gaskets from the header back as well as the graphite ones to the B-pipe. I just wanted to be sure since removing any of this again generally means dripping all the underbody trays and having to replace all the one-time crush gaskets a second time.

As far as the exhaust smell I was reasonably sure that the gaskets would fix it, but had read on the forums there was a common complaint of this exact same thing. The common concensus on there was it was due to deterorating rubber flappy gaskets in the trunk. When new the OEM flappy gaskets would allow for circulation when driving the car and keep the trunk from getting mildewy if wet. Also they supposidly acted as a relief valve to keep equalized pressure inside /outside the car when slamming the doors. Mine no longer had the rubber sealing flaps and since I had carbon doors that were not fully weather sealed i figured I would just block these off so stop any potential ingress of exhaust fumes into the car.

 

It was simple enough to trim off the excess plastics, cut a piece of carbon fiber and weather seal it into place. 

Once installed into the car they closed off the holes tightly and seem to be working. So far so good. I have another few events coming up soon that ill be able to see if all the fixes worked

 

 I'm going to end this one here, again its much longer than I thought it would be. Im sure that ill have more to write about soon.