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Yes, Lobux... that and the placement of the wire inputs on the Engine ECU. I will respond more in-depth when i have a spare second and can get pictures and stuff, this month is a total ****-show for me time wise.
Hey william have you upgraded your fuel pump/sytem? Last track day my F suffer from fuel starvation, seems like the car is choking on highspeed corners. I have an upgraded AEM 320lph intank pump.
@ljdsong Yeah. On long left handers it will starve if sustaining more than 1.2g's of lateral grip. you have to fill allllllll the way to the brim to keep that from happening. I have a couple solutions that are going in the car to fix this as soon as I feel like pulling the fuel tank out.
I decided to update the front aero after looking at some data from my latest trips to Chuckwalla. The car has plenty of high speed understeer and it got a bit better after pulling off the gurney on the wing but the ideal direction is to increase the downforce on the end needed to balance it out, not decrease it on the end that is working. The car still has relatively low (stock) horsepower, about 370 according to my longitudinal data and some math, but that is enough to push the car with additional aero drag through the air to some fast laps as long as I am smart about things.
This first thing I wanted to do was add a low drag rear extension off the trunk to reduce overall drag on the car and promote smoother airflow under the wing. It took a bit of work to complete but I finished it with some black vinyl to retain the visual trunk line.
With the same goal I also deleted the wipers and sealed the cowl area from the hood to the windshield. The wiper motors and all that are still there and this blank plate is only held on with three bolts and some 3m all-weather tape. It can easily be swapped back to stock if and when I want to go drive a rain day at the track I think it worked out well. They work in tandem to smooth out the air flow and lower the drag substantially based on data from similar cars the cowl sealing alone is a net gain of around 20lbs of DF
After doing these mods I drove the car to the track and noticed a 3mpg difference per gallon on the 260 mile drive. Not bad.
For the new splitter I wanted a larger aspect ratio, longer overhang, and optimized fences with slot gaps. I went with the hammerhead-ish design because I also wanted to have the main airstream hitting the splitter at a right angle- and since I also wanted to lower it as much as I could the shape helps allow for the car to roll and pitch without it grinding into the ground. There's only a few 'rules' that work every time as far as front downforce. 1 is surface area 2 is height.
If you can get it big (up to a point) and low (up to a point) with the correct AOA it will create a strong pressure differential and you will gain negative lift.
The shape I decided to use was borrowed off an old design I had made and CFD for a previous racecar of mine. After measuring doing the math I gained about 27% more non cambered surface area and was able to lower the blade half of an inch. While I was there I also went back to basics and sealed off every gap and crack on the carbon block off plates and chin spoiler as well as created smooth transitions into the diffuser tunnels
Having lowered the splitter I had to reweld some of the stanchions to get the ideal angle on them, I also built some aero profiles for the flat leading edge to speed the air up along the bottom side. To seal the belly pan to the new height of the splitter I also fabricated a profiled 'wing' in the transition with a 34x10 surface area... that's a pretty substantial surface area and it should really help make the pressure stay low at the axle line.
Dialed in AOA
Almost the most important thing... the changes look menacing.
Once it was all done I took the car out to what is likely the worst track to test any setup changes, least of all aero, Streets of Willow. I *do* really like this track because its HARD to go fast here, especially in anything over 2300lbs. Its a good equalizer to sort fast cars and fast drivers, but, unfortunately in the last 2 years its gotten bumpier and bumpier. It's basically at the point now where I'm considering either not driving there till it's fixed, or building a specific (higher) splitter so I don't destroy this one.
First session out was cold (42*F) so it was a bit slick for the first few laps, but once the tires came up to temp i felt like there was enough under me to try and throw a few down. Unfortunately the club was holding a 86/BRZ challenge this day so I was sharing the track with a lot of car that I had a 10 second delta on. This is not ideal at a small track like Streets where passing needs to be done delicately, so I spent a few laps of good tire life only to catch up to a much slower moving car and opt out of the divebomb. At the end of the first session I felt some front end weirdness and pulled in only to find a deflating tire due to a puncture. This sucks because session 2 was going to be the golden session to go fast in. We would be gridded by lap time so traffic would have been better, also the surface would have been scrubbed in by the other cars. Unfortunately I had to wait with the car up in the air for my girlfriend to drive out 2 hours with a scrub tire from the basement. After getting the tire mounted at the track tire shop and missing the golden session I decided to run one more to get the data. By now the weather was pretty far outside the PB window and the wind and kicked up a bit. Once back on track I had a really fun drive out-pacing a KTM crossbow driven by an old pro driver from way back. He was pretty puzzled how the ISF on 200 TW tires with much much worse power to weight was beating the KTM North America demo car.
In both session i matched my PB time of 1:21.xx multiple, times. Looking at the data the brakes zones just didn't have the grip they had the last times I was there. I was up on the lap times in the aero sections but the time differentials converge back when under brakes. Also I was literally jumping at 110+ mph off a bump into a braking zone and mashing my splitter into the asphalt over and over again. I decided to call it a day out of splitter preservation.
Looking at the averages afterwards my front R and L shock potentiometers were seeing 3mm of additional deflection against the previous data I was seeing with the old setup, it was also ramping with speed. I'm going to do the calculation on what that means in Lbs DF-wise at the shock pot once I scale for aero moment. Overall though its a big change in the right direction. I'm sure I'll see even more gains at a track that I can utilize the aero even more on.
Sounds like a lot of rubbing in the video. Is that just the video?
To give me perspective, what kind of cars run a 1:21 there?
Your 370 hp estimation seems low for a FBO ISF. We see 400-430 whp with FBO. That may be a conservative number, unless the engine is a bit tired.
Id say 100% the engine is tired. Everytime i plug the numbers into RS3 with realistic drag CO it comes back 370-375 with 390hp spikes. Its calculating from 0-60 and 0-80 so aero drag isnt effecting these numbers. Yes there is A LOT of rubbing and its all titanium skid puck to racetrack surface your hearing, not tire to chassis. The bumpy surface is just plain awful there now, especially with low aero.
So, for perspective Hyper cars like macs or special prep gt3 with 500+hp and sticky-sticky tires can run sub 1:20 range with a competent driver but rarely do. A fast car with a quick driver familiar with the track will generally peak around the 1:24-1:23's and is normally top dog at the event. Anything in the 22's is considered 'really fast'.. 21's, 20's is pretty rare, even with people that are fast elsewhere. i think maybe 20-40 cars have gone that quick and are either 250k+ factory cars or extremely well developed race/attack programs, Either way you have to know what your doing, even in a fast car.
Lyfe motorsports GTR (look it up, its insane) did a 1:17 on race slicks which i think is the overall track record for a unlimited built time attack car. 1000hp awd etc
@kos What did you run there in your TA Subi, like a 1:20?
Id say 100% the engine is tired. Everytime i plug the numbers into RS3 with realistic drag CO it comes back 370-375 with 390hp spikes. Its calculating from 0-60 and 0-80 so aero drag isnt effecting these numbers. Yes there is A LOT of rubbing and its all titanium skid puck to racetrack surface your hearing, not tire to chassis. The bumpy surface is just plain awful there now, especially with low aero.
So, for perspective Hyper cars like macs or special prep gt3 with 500+hp and sticky-sticky tires can run sub 1:20 range with a competent driver but rarely do. A fast car with a quick driver familiar with the track will generally peak around the 1:24-1:23's and is normally top dog at the event. Anything in the 22's is considered 'really fast'.. 21's, 20's is pretty rare, even with people that are fast elsewhere. i think maybe 20-40 cars have gone that quick and are either 250k+ factory cars or extremely well developed race/attack programs, Either way you have to know what your doing, even in a fast car.
Lyfe motorsports GTR (look it up, its insane) did a 1:17 on race slicks which i think is the overall track record for a unlimited built time attack car. 1000hp awd etc
@kos What did you run there in your TA Subi, like a 1:20?
@illwillem you have a good memory haha 1'20"637 was my time, and that was my first and only time ever going there. Between the crap BBK I was on, and just trying to overdrive, there was definitely more time in it.
You are right, that track does not bode well to anything over around the 2300lb scale, I was around 3100lb or so in the video iirc, and you can feel it around there. 255/35 RE71Rs were the tires on the car at the time, and they were getting worked, that surface is abrasive, and that video was from 4 years ago. Can't even imagine how much worse it is now
Hi Will, such awesome write ups. I think you were outdriving John Mueller out there that day. Usually, very "proud" guy previously from the Evo world. Nice guy, but very loud about this work .. lol, Again, thanks for all these write ups.
01-27-21, 06:59 AM
