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Scribe

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Scribe last won the day on December 7 2017

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  • Birthday March 24

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  1. @turbogrill I believe BW has a smaller one than that, the 6258. However, it looks like you would stay in the center of the map you posted if you stopped being a wimp and turned that hypothetical boost up 😋 I personally love MHI (Mitsubishi) turbos as the best bang for the buck If you pick up a used Evo VIII or IX turbo, you will have nearly all of the goodies of the EFR except the integrated BPV and they are journal bearing vs ball bearing. It may also be a better size for what you are looking for. You can find compressor maps for a lot of Mitsubishi turbos on the web.
  2. Do you still have an EGR valve on your engine? That is usually the biggest contributor to carbon buildup that I see. Also, 24 hours of racing is probably more WOT time than a few years of driving around town.
  3. If driver stint limits were reduced to 1:30, everyone would buy 944's and Saab's with fuel cells and go 3 hours with a short driver change in the middle.
  4. There is a good article on that here: http://www.mulsannescorner.com/rearwingLMPCFD2009.html Short answer: yes, but there is a weight and CG height penalty for it (small, but its a consideration) The Ford GT and Corvette GTLM cars still do bottom-mounts, but they also contour their wing mounts to reduce the separation on the bottom surface of the wing.
  5. Disclaimer: I have no formal aerodynamics training and most of this info I am going to share I have just picked up on the side for fun. Feel free to critique anything I am about to say. I believe @@NineLivesJohnny's explanation was correct about the increase in downforce/front end stability from venting the hood is more of a side effect from taking air that may be disrupting the underbody flow and putting it somewhere less disruptive. If you are going to vent your hood, you want to vent it as close to the convex portion of the hood, which will most likely be at the front. This will be the area of lowest pressure and it will only get higher as you approach the windshield, which creates a concave shape with the hood. This is why vented cowls are usually a very bad idea for heat extraction and a great idea for a cold air intake. Another side effect of venting your hood for radiator airflow is that it may allow you to decrease the size of the radiator inlet duct, which can also improve front downforce by maintaining the high pressure zone above your front splitter (assuming you have one). Ultimately, venting the hood is more of a cooling airflow improvement that may have lift reduction (downforce) benefits depending on how the engine compartment was originally vented on your vehicle. You will notice that very high downforce cars like LMP1, LMP2, and DPi that don't have road car constraints will not have any cooling venting on the top of the car and will have all of it at the rear. They also pull air into their side pods for the heat exchangers from underneath the car, which further promotes underbody airflow. Minimizing the gap between the front of your car and the ground with a splitter is one of the easiest ways to create front downforce. Forcing air into a very small area will cause it too accelerate in an attempt to maintain the same mass flow rate, which will lower the pressure under the front splitter. The next step is to add diffuser tunnels that vent towards the inside of the front wheels and vent the rear of the front fenders to further increase airflow velocity under the front splitter. This is where it gets interesting in my opinion. You will notice a difference in design from what I described above in the most recent GT3, LMP1, LMP2 and DPi cars, and one-off hillclimb cars like the VW IDR. Below is the progression of front splitter design for the Ferrari GT3 car (458, 488, and 488 Evo) Notice how the raised portion of the front splitter goes from being non-existent to being nearly the full width of the front-end. The issue with running a flat front splitter as close to the ground as possible is that your front downforce becomes very pitch-sensitive. As soon as the splitter gets too close to the ground due to braking or bumps in the road, you will lose a large portion of your front downforce. This makes for a car that will be very unpredictible to drive, but still stable as the rear downforce will be maintained. These are things you will not notice in CFD or in the wind tunnel, but on the track. By having a raised front splitter and shaping like a nozzle, you still have high velocity air going under your front splitter, but it will be much less pitch sensitive. This is what they mean when you read the press releases of these cars and they say the car is "easier to drive at the limit" than the previous generation. For reference, here are pictures of the underside of the 488 GT3 (middle picture): One thing to note, this splitter design does not work very well unless you can maintain air velocity underneath the car. You cannot add a large raised front splitter on an old sports car and expect it to work. You need a flat bottom like the one above as well as a large rear diffuser to keep air velocity high though the entire underside of the car. As the air becomes turbulent from interacting with parts under the car like the exhaust, suspension, and, drivetrain, you will lose air velocity under the car, which will reduce air velocity at the front, which will greatly reduce front downforce and overall downforce. There is also the problem of the boundary layer increasing in size towards the rear of the bottom of the car. This can be combated by adding positive rake to the vehicle. The key to efficient and effective aero design is to get all of the parts of your aero package working together. With all of that said, lets go to side skirts. This is an area that I think a lot of people mess up. Fully-sealed side skirts are only effective if you are able to maintain underbody air velocity from the front of the car to the diffuser. Otherwise, you are cutting off valuable airflow that the diffuser may need. Norbert Singer briefly describes this phenomena in this video: Below is a comparison between the Porsche 919 and 919 Evo: You will notice the side of the Porsche 919 is very high off the ground. Due to the rules restricting the diffuser size as well as what can be done with the side skirts, they found that rounding the edge of the side skirts and directing the inlet of the rear diffuser towards the side (shown in the second picture, this is actually from the Cadillac/Dallara DPi car) was their best way forward. You will also notice the car has a lot of positive rake to effectively make the entire underbody a diffuser. The 919 Evo is an unrestricted version of the 919. No longer hindered by the rules, they were able to greatly increase the size of the rear diffuser. They also made the rear wing larger and moved it rearward. This created a very large low-pressure area at the rear of the car, which helped maintain air velocity under the car. This allowed side skirts to be beneficial, so they were added. By feeding the rear diffuser from the front instead of the side, they were able to shift the aero balance forward. They then shifted it back to neutral using the giant rear wing and increased total downforce significantly. This design can also be seen on the VW IDR below, which is also unrestricted by rules: If you add side skirts to your old sports car, you may see a small drag reduction, but probably no downforce. One last note is that you want to try to match your downforce balance to your weight balance. If your car is 55/45 Fr/Rr, you want 55% of your downforce at the front. There can be exceptions to this, but it is a good rule of thumb. You should also be aware of how the downforce balance (center of pressure) changes as speed increases. You don't want the balance to shift forward, as it will reduce rear stability at high speed. There is so much more I could get into, but I should probably call it a night. I hope this post is informative and creates some more discussion.
  6. What is it that everyone wants from this series? Why are you here? Do you just want to have fun? Do you want to improve your driving skills? Do you you want to learn how to make your car faster? Do you want to satisfy your primordial urge to prove you are better than everyone else by collecting trophies made from scrap metal? Everything except the last one is possible in Champcar with very little monetary investment. I am pleased with the direction Champcar is going. I am looking for a place to improve my driving skills by getting a lot of affordable track time. I am also looking to put engineering theory to practice and learn from tinkering with my car. If we make everything more like a spec series, than I won't get to tinker as much and will go somewhere else where I can. If costs rise because we have to bring dyno's to every race, buy inspection equipment, and hire a bunch of technical experts, then I will probably go somewhere else that is cheaper. Do I want to win? Sure. But I'm more content with getting to learn a lot from every race I do. If someone spends $40k on a Champ build, I'd just assume that they must have overpaid for a lot of stuff instead of doing it themselves. I have yet to see someone spend their way to the top. There will always be a level of execution that cannot be bought and can only be realized through preparation, experience, and ingenuity. Look at teams like Tuttle and Sahlens. They are big money spenders that have only occasionally found themselves on the top step of the podium, but they are very fun to race against. If I could only have one suggestion, it would be that maybe engine building should be limited by banning race fuel and keeping fuel capacity limits in place. Everything else should fall into place with yearly VPI adjustments to keep any over-performing platforms in check.
  7. My impression from this forum is that not enough people have experience tuning engines. I got into racing by going to test-n-tunes at my local drag strip, so all I cared about was horsepower back then. The amount of horsepower you can gain with megasquirt or any other aftermarket ECU is limited to how far the original tune was from MBT ignition timing (maximum brake torque). Once you can achieve MBT timing, no additional gains can be made unless you reduce friction/pumping losses, or increase volumetric efficiency. With that said, you can make gains to fuel economy at the expense of your cooling system (lean = HOT). If the factory engine was knock limited, you will find horsepower gains from switching to a higher octane fuel and increasing timing to MBT timing. However, by experience is that most of these old 80's and 90's engines we use in Champ are not knock limited unless it was boosted from the factory or something is wrong with the engine (excessive blow-by). Once you're at MBT timing, you can mess with intake upgrades, exhaust upgrades, porting, and cams, which will increase volumetric efficiency. This will most likely increase your in-cylinder temps, which may cause knock. You then either back off the timing, or add more octane. Rinse and repeat until you run out of money. A modified engine has much more to gain from a programable ECU, and the PartsBadger guys seem to be taking advantage of that. Just to be clear, modified engine means aftermarket header in this case. I do not know or think they have done any internal modifications. A properly designed tuned-length header can make a big difference to high-RPM breathing and has the added benefit of keeping your in-cylinder temps down.
  8. I just got ECUMaster's PMU-16 for power distribution duties and I have been pretty impressed with it so far. My favorite part is that their CAN network is fully configurable (with USB to CAN add-on) so you can set it up to communicate with nearly anything. I am working with someone to have the PMU emulate a Haltech CAN expansion module to allow it to communicate with Haltech's "propriety" CAN network. I'm sticking with a Haltech 1500 over the EMU Black due to running a MAF setup over speed density (EMUMaster does not have MAF support). It also helps that I already had the Haltech laying around. I really like how the EMU Black has a built-in wideband O2 controller, so no expensive add-ons required. Did you talk to Haltech about electronic wastegate support? I have a BMW/Mitsubishi actuator sitting on my desk that I might try to mess with.
  9. I already have 3 cars worth of parts for these, so I don't think I need any more at the moment. I could always use more turbos, intercoolers, oil coolers, and radiators if you're willing to partially part the roller out.
  10. FYI, the DOT standard the 6 in DD light bars meet is for "Driving/Auxiliary High Beam Light" so it can still blind the heck out of people (see: driving with your high beams on), but I guess it should be better than the really crappy ones. I believe that HID retrofits retaining the factory cutoff or projector retrofits are the best way to go.
  11. I am really impressed with all of the features that were packed into this system. I would have never thought to add a pit lane timer, which is awesome. No more having the timer fall off or get put on with an incorrect number! (assuming Champcar would allow you to use it instead of the egg timer) Other things I like: Reduced speed differentials at re-starts Less passing under yellow No more wondering if that black flag is for you This all sounds like a huge benefit to not only driver safety, but also to race control efficiency. I don't understand why people are so skeptical. We currently rely on a transponder (which allegedly costs way more than this) to record lap times. Assuming it proves to be reliable, I wouldn't have an issue with this being series mandated. Is there a way to add a feature to tell people to speed the F*** up when they are being a second pace car?
  12. We changed drivers during the Sunday quiet hour to see if we could get rid of a pit stop by going 2:45 on the first tank.
  13. We've run both Lemons and Champ at Gingerman this year with our Volvo 960, which has a 19 gallon tank. At the Lemon race we were able to go 2:45-3:00 per tank. At the Champ race, we could only go 2:00-2:15. Our fast lap was actually faster at the Lemons race, but the sheer number of cars on track and the much slower pace they are going greatly reduced our lap time as we had to pass 5+ cars every lap. There were also yellow flags and safety trucks out for about half the time we were on track. If you are going to get rid of fuel capacity, at least give it to your mustang brethren! I think I've heard they want more.
  14. I just want to remind everyone that a certain MR2 with Randy Pobst behind the wheel did a 1:28.8 last year , exactly 3 seconds faster than the SC300. From what I have seen, the SC300 in question is well built and well driven. With that said, I really like the repurposed aero on the SC300 in question. I don't think it offers a huge performance benefit over adding a bit of high speed stability to counteract the lift most road cars make at higher speeds (Its going to be pretty hard for most people to notice ~50-100 lbs or rear downforce on a ~3000 lb car). These are the type of solutions I really enjoy seeing in Champcar: cheap (free in this case) and effective. If you guys want a spec series, go race in a spec series. There you will find that there are still several seconds in laptime between first and last place.
  15. Maybe one day. I'd like to get my car built first, its starting to rust from sitting for so long!
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