Preparing car for heavy road course duty

[Kaldar142]

I wouldn't bother with the windage tray or crank scraper right now.

Whys that?

 

[SoundGuyDave]

First, there is a windage tray in the motor from the factory, I do believe... As for the crank scraper, I don't really see the benefit vs. the cost and PITA factor. I may be wrong, but I just don't think it'll be any real help under our operating conditions.

 

[Kaldar142]

just so i understand, why exactly is the cowl area a high pressure zone? what does that mean lol

 

[pcdrj]

Do you think running 100 octane at the track would be any benefit? I don't mind paying the extra $$$ if it will help keep my car just a bit safer.

I run 100 octane at all track events. It's cheap insurance and will make a little more power.

Also running Canton oil pan with '04 Cobra pickup which fits nicely after a little die grinding work.

 

[Jaylee]

I have a buddy that works at a local Ford dealer. He told me to only run 87 octane unless I have an aftermarket tune. I am guessing that you guys have some sort of programmer to run higher octane? Also is the 100 octane you use in your car unleaded?

 

[SoundGuyDave]

just so i understand, why exactly is the cowl area a high pressure zone? what does that mean lol

Think about the airflow over the front of the car... Innocent air molecules are just hanging around, minding their own business, when suddenly this rather blunt object comes screaming through the neighborhood, (hopefully!) at fairly high speeds... Air in front of the car has essentially five places it can go: 1) under the car, 2) over the car, 3/4) left/right of the car, 5) into the engine bay, and from there to the underside of the car. To predict how the air is going to react to each of these different cases, you need to get into a little bit of fluid dynamics (air behaves as a fluid does at speed), and get at least a nodding familiarity with the Bernoulli principle. In short, for a given amount (volume) of air, pressure and velocity will have an inverse relationship. That is, as pressure builds, velocity drops. Getting back to our somewhat bruised air molecules, they do NOT want to stand still in front of the car, but will attempt to flow around or through the car, to get back to their normal state of rest. The first high-pressure zone will be right in front of the car, around the bumper, grille, and radiator inlet. Because of all the restrictions to flow through the radiator, the engine bay tends to be a slightly high pressure area, which increases with reduction in exhaust from the area. Since high pressure air wants to flow to low pressure areas, the pressure zone in the front of the car will try to flow to lower pressure areas, like the top of the hood, sides of the front fenders, and under the car itself. If the car has front aerodynamic treatment, like an air dam, that will help to channel the air around and over, creating a fairly large low-pressure area under the front of the car. This low pressure area creates negative lift, which translates to a slight amount of downforce on the front end. Adding a splitter to the front creates a large surface area for the air to act upon. High pressure air (bow wave, if you will) above the splitter, and a low pressure area underneath, which can create quite a bit of downforce if properly designed and implemented. Meanwhile, what we're concerned with is the airflow over the hood. We have a huge area of high-pressure low-velocity air trapped as a pocket in front of the car. As the air begins to bleed off the top of that pocket, leading over the hood, it creates a low-pressure area and starts streaming towards the back of the car. When it hits the base of the windshield, however, right at the cowl, the change in airflow direction creates another high-pressure area. This area will be higher in pressure than the area under the hood, and as a result, air flows into the engine bay from the cowl, as well as being redirected over the top of the car. I'm not a physicist, and did not stay at a Holiday Inn Express last night, so if you want more info, google the terms "laminar flow" "aerobytes splitter" "race car downforce" etc. and start reading... Suffice it to say that once you start to wrap your head around aerodynamics as related to the S197, you'll really begin to understand why there can't be a functional diffuser on a production body, and why real wings have such tall uprights, and why the short wings just simply don't function efficiently enough to justify the drag.

The bit about taping pieces of string to the edge of the cowl and seeing what they do at speed is actually very valid. If you've ever wondered about how the car manages aero in different areas, just dribble a little bit of motor oil in a line from side to side on the paint and see how the air passing over the car pulls it aoround. Ever wonder why rain never seems to get on the back window? Airflow over the top of the car pulls it right past the back end. Ever wonder why you get so much brake dust on the trunk end panel and back bumper? Huge low pressure area sucks it all in....

Hope that helps, and if there's anybody more qualified that wants to chime in, please feel free!

 

[pcdrj]

I have a buddy that works at a local Ford dealer. He told me to only run 87 octane unless I have an aftermarket tune. I am guessing that you guys have some sort of programmer to run higher octane? Also is the 100 octane you use in your car unleaded?

The simple answer is yes I have a tune for racing. We tuned with 93 in the tank but I routinely run 100 unleaded at the track. If you run leaded fuel you'll damage the cats and over time possibly valves. My car is supercharged and makes 535 rwhp but that's not really the issue.

Been doing a lot a reading lately on dyno tuning for cars being used in road racing (Porsche forums) and spent a little time with my tuner, who is arguably one of the best drag race tuners around, to get a solid road race tune down. Drag racing is somewhat easy as it takes 10 seconds or so of extreme conditions and it's over. You'll spend 20-30 minutes in the average DE event and exposing the fuel and lube systems to significant g's all of which can't be seen on the dyno. At some point during the run, there will be a leaner condition which will pull timing out of your car to prevent detonation (detonation=heat).

The higher octane will keep the timing up longer and help prevent the lean condition.

 

[Kaldar142]

Those were exactly my thoughts and that's why I plan on using 100 octane next season.

 

[SoundGuyDave]

The simple answer is yes I have a tune for racing. We tuned with 93 in the tank but I routinely run 100 unleaded at the track. If you run leaded fuel you'll damage the cats and over time possibly valves. My car is supercharged and makes 535 rwhp but that's not really the issue.

Been doing a lot a reading lately on dyno tuning for cars being used in road racing (Porsche forums) and spent a little time with my tuner, who is arguably one of the best drag race tuners around, to get a solid road race tune down. Drag racing is somewhat easy as it takes 10 seconds or so of extreme conditions and it's over. You'll spend 20-30 minutes in the average DE event and exposing the fuel and lube systems to significant g's all of which can't be seen on the dyno. At some point during the run, there will be a leaner condition which will pull timing out of your car to prevent detonation (detonation=heat).

The higher octane will keep the timing up longer and help prevent the lean condition.

I think I know what you were getting at, but there are some things that I would consider inaccurate above... G-forces on the lube system will have little measurable effect (on an instantaneous basis) on combustion chamber temps. G-forces on the fuel absolutely CAN and WILL at some point cause a momentary sag in fuel pressure, and thus in fuel delivered to the injectors. That will cause a lean condition. The car's computer will have to pull timing at that point to reduce combustion chamber temps to avoid pre-ignition (detonation). Simply changing the type of fuel, up to a higher-octane type, will NOT affect the mechanics that govern fuel delivery. Higher octane fuels, in a nutshell, effectively detonate at a higher temprature (pressure), allowing for more timing to be run prior to detonation. More timing=more power. The type of fuel used will NOT "help prevent the lean condition," which is a mechanical function, and the main cause of detonation. If you tune for less power, running richer and with less timing, then you'll have a safety margin against detonation, but if the pumps suck air, you're going to go too lean, no matter what kind of fuel you are using.

My understanding of the physics involved with higher-octane fuels is that the fuel itself burns cooler and has a slower flame-front propagation rate than the pump gas does, and that more timing can be dialled in to allow you to extract the extra energy potential of the higher octane fuel. Either way, if your tune is on the edge, if you sag the rail pressure, then you'll wind up detonating.

Bottom line: For the road course, run the fuel the car was tuned for, and set the tune up conservatively. We've ALL experienced fuel slosh, whether we've realized it or not. How many times have we been on track with around a half-tank (or less) of fuel, and watched the fuel gauge cycle back and forth between full and empty? That's fuel sloshing from one side of the saddlebag tank to the other. There is a "transfer pump" of sorts that's supposed to equalize the two sides, but it was never designed to keep up with the constant cornering forces we expose our cars to out on track. The only way to really guard agains a slosh-related lean dropout in rail pressure (with a stock tank) is to run the tank at least 1/2 full the whole time we're on track.

 

[STEVE_POE]

Just a opinion but the oil pan is a waste of money. I've talked at great length with people in the fr500s program. not needed. no fr500s cars have pans on them and they ran fr500s cars at the 25 thunderhill with stock pans. I run a stock pan and I Have not seen anything that would make me believe it's needed.

Don't believe all the hype that it is a must need.

side note: does the roush trak- pak come with a road race pan ?

 

[Kaldar142]

So you see no benefit of running one?

 

[Vapour Trails]

waist of money

I wish I had a waist of money.

 

[DusterRT]

I wish I had a waist of money.

I'd like a maid of money myself..

 

[STEVE_POE]

ya ya wrong spelling....fixed

 

[pcdrj]

I think I know what you were getting at, but there are some things that I would consider inaccurate above... G-forces on the lube system will have little measurable effect (on an instantaneous basis) on combustion chamber temps. G-forces on the fuel absolutely CAN and WILL at some point cause a momentary sag in fuel pressure, and thus in fuel delivered to the injectors. That will cause a lean condition. The car's computer will have to pull timing at that point to reduce combustion chamber temps to avoid pre-ignition (detonation). Simply changing the type of fuel, up to a higher-octane type, will NOT affect the mechanics that govern fuel delivery. Higher octane fuels, in a nutshell, effectively detonate at a higher temprature (pressure), allowing for more timing to be run prior to detonation. More timing=more power. The type of fuel used will NOT "help prevent the lean condition," which is a mechanical function, and the main cause of detonation. If you tune for less power, running richer and with less timing, then you'll have a safety margin against detonation, but if the pumps suck air, you're going to go too lean, no matter what kind of fuel you are using.

My understanding of the physics involved with higher-octane fuels is that the fuel itself burns cooler and has a slower flame-front propagation rate than the pump gas does, and that more timing can be dialled in to allow you to extract the extra energy potential of the higher octane fuel. Either way, if your tune is on the edge, if you sag the rail pressure, then you'll wind up detonating.

Bottom line: For the road course, run the fuel the car was tuned for, and set the tune up conservatively. We've ALL experienced fuel slosh, whether we've realized it or not. How many times have we been on track with around a half-tank (or less) of fuel, and watched the fuel gauge cycle back and forth between full and empty? That's fuel sloshing from one side of the saddlebag tank to the other. There is a "transfer pump" of sorts that's supposed to equalize the two sides, but it was never designed to keep up with the constant cornering forces we expose our cars to out on track. The only way to really guard agains a slosh-related lean dropout in rail pressure (with a stock tank) is to run the tank at least 1/2 full the whole time we're on track.

Yeah we're basically saying the same thing I think. The lean condition I'm referring to is mainly due to temperature while the lube system is due to g's. A little oil starvation in a couple of hot corners or braking can increase friction therefore increasing heat.

We saw lean conditions in August not due to g's but engine IAT temps. Larger radiator, I/C with dual fans and 100 octane solved our problems.

 

[Sam Strano]

I have a buddy that works at a local Ford dealer. He told me to only run 87 octane unless I have an aftermarket tune. I am guessing that you guys have some sort of programmer to run higher octane? Also is the 100 octane you use in your car unleaded?

My '07, bone stock not only ran better on Premium than it did on Regular fuel, but the mileage was better too.... in fact enough better than it didn't cost me anymore in the end to run premium in normal driving. But the car was so much stronger, and on 87 it would detonate (all kinds of different brands of gasoline including BP/Amoco and Exxon/Mobil).

I'd certainly recommend better than 87, regardless of what's claimed.

 

[pcdrj]

Just a opinion but the oil pan is a waste of money. I've talked at great length with people in the fr500s program. not needed. no fr500s cars have pans on them and they ran fr500s cars at the 25 thunderhill with stock pans. I run a stock pan and I Have not seen anything that would make me believe it's needed.

Don't believe all the hype that it is a must need.

side note: does the roush trak- pak come with a road race pan ?

This surprises me a bit. I lost one engine on track. Lean? Oil starved? Maybe both? Cars pulling between 1.2-1.5 g's will likely see some oil starvation with a standard sump. The Canton pan has baffles, takes a little more oil, and after putting out for a new motor it was cheap insurance.

 

[Sam Strano]

I've been running the piss out of, and pulling way over 1g (1.2 not abnormal considering I can pull 1 in a slalom) for 3 years in an S197 with no issues. Can't say that there might not a split second here or there the sump isn't uncovered, but certainly oil 'starvation' hasn't been an issue, and if the FR500S's are using a stock pan, I think that's about case closed on needing to upgrade it.

 

[SoundGuyDave]

I've been running the piss out of, and pulling way over 1g (1.2 not abnormal considering I can pull 1 in a slalom) for 3 years in an S197 with no issues. Can't say that there might not a split second here or there the sump isn't uncovered, but certainly oil 'starvation' hasn't been an issue, and if the FR500S's are using a stock pan, I think that's about case closed on needing to upgrade it.

I had once incidence of oil starvation in a LOOOONG left-hand sweeper, and it was only for a fraction of a second. If you're looking to absolutely bulletproof your oil system, then the pan isn't going to hurt you. It may not help any, but it certainly won't hurt. I went the other way, and installed an Accusump. I now regularly pull well in excess of 1G in the corners (R6 FTW!), and have had ZERO issues. I would be willing to bet that the FR500S cars set up for endurance racing run Accusumps, and maybe the Miller Challenge cars as well. Can't say for sure, but if you wander the paddock and look at the race group cars, you'll see an awful lot of those blue cylinders around...

pcdrj: When you say "lean conditions" are you referring to an acutal shift in mixture ratio? Were you able to quantify it with a wideband? A lean air/fuel mixture is only one possible cause of detonation, the others are high cylinder inlet temps, excessive spark advance, or sharp corners on the head or piston, leading to pre-ignition from residual heat. Temp will not affect the ratio of air to fuel, in any way, shape, or form. The TUNE can incorrectly compensate for the temprature, however. Do you have your blower set up with AIT measurement at the intake manifold, or just after the filter? Once the air runs through the compressor, heat will increase. Running it through the intercooler should reduce that heat, but with varying degrees of success based on heat exchange medium, exchange efficiency, etc. Then the charge hits the intake manifold. If, for example, the IAT sensor is right after the filter, it can be reading air tempratures of around 95* (for example), just above ambient. At that point, the computer cross-references the MAF reading to develop a flow density multiplier, and adds the appropriate amount of fuel to hit the target mixture. If, in that same case, however, you run the air through the blower, and then through the intercooler, the IAT at the intake valve (as measured at the manifold runner) could be considerably higher than that 95* temp. Since hotter gasses are less dense, the intake charge doesn't have nearly as much oxygen content as the computer thinks, and as a result, the mixture will be off. This is NOT due to heat, per se, but due to the computer's receiving garbage data. Also, please note that in this case, the mixture would swing towards the rich side, not the lean side. The problem, however is with the air-charge temp, prior to compression in the cylinder. With elevated temps, the computer would have to pull timing, to keep compressed temps below the flash point of the fuel mixture, and if it STILL thinks the air is going in at 95*, not 195* as it actually is in the runner. In any case, however, the air/fuel ratio is still correct, based on the volume of air flowing into the engine, which is reported by the MAF. Detonation in this case would be caused by excess timing and/or intake charge temprature. Since higher octane fuel has a higher flash temp, and tends to run a cooler flame front, it would provide some protection (but not much) agains pre-ignition in this particular case, but not as much as a properly-tuned (conservative!) engine on pump gas. Make no mistake, heat is indeed the enemy, but the amount of heat generated by momentary sags in oil pressure will be minimal. Particularly in comparison to the increase in charge-air temp due to a heat-soaked blower and intercooler. Once you get the exchanger core surface temp up, it will take a long time to fall again, and while the temp is up, the efficiency of the exchange suffers. If you run 250* air through a heat exchanger with a surface temp of 100*, ambient, and it has a net resulting efficiency of 50%, you will drop the air charge down to 175*. After being exposed to that 175-250* internal temp for a decent period of time, however, the exchanger core itself will begin to heat up, to maybe 200* or so. Applying that same 50% efficiency, that means that your exit temp will have now climbed to around 225*, which is going to cause problems unless the computer pulls the correct amount of timing to compensate for the increased temps. The moral? If you're going to track your car with a blower, make sure that you have the IAT pickup post-intercooler, and not pre-compressor... Also, both air-to-air charge coolers and air-to-water charge coolers suffer from heat soak. I'm not trying to bust your chops here, but there is a significant semantic difference between a lean condition and excessive timing. Upping the octane rating of the fuel will cover a small timing map error, but all that lets you do is make more power for longer before you're back in the same boat again.

 

[Gray Ghost GT]

Accusump is a great upgrade. I have one installed on my Corvette C5 dedicated track car and will also install one in my '09 Mustang GT even though its primarily a daily driver. My Canton 3 quart Accusump will have a pressure controlled release valve and may be plumbed with a oil cooler with oil thermostat. Cheap insurance to save your motor if you spend a lot of time on the road courses.