What fuel for Road Racing?

[MrSparkle]

I see there's a thread on fuel for drag racing. What do you road racers run? And does anyway run water/alcohol injection on road courses (or is it too risky)?

 

[tackla]

What type of road racing? Endurance ,track days ,autox, IT , ect... Turbo car , hot day, 20 minute session at the least. Good tune low boost?

 

[MrSparkle]

Track day/weekend. I guess boost is the second part of the equation. I should have asked what boost and fuel do you use?

It seems like a lot of the road racers on the evo forum run some form of race gas (actually I didn't read of anyone using pump). I'd like to run pump like I did with my Stealth but I'm pretty sure my Talon with a 2.4L and 50 trim won't like that since I can push it hard enough on the street to start knocking. I was thinking of adding water injection but it's just another thing that could go wrong.

Am I just being too cheap and unrealistic?

 

[Greg Collier]

I run VP 103 unleaded. Unless you bring your own gas to the track (for me that's about 40 gallons) you use what's pumped there. It's usually VP 100 or 110 leaded... not much of a choice. I try to stay with the same octane that I tuned with...

Greg

 

[1LE]

One of the tracks I frequent doesn't have "on-site" fuel during open track days. Nearest station only has 93 octane. So, we tend to run lower boost

Many times the fuel is dictated by the group you're running with.

 

[cait sith]

110 Leaded and use the tuning from DSMLink that I use on the street with 93. Usually.

I was running 1100°-1200° C peak EGT's with 93 octane at Limerock with my "street settings", and my exhaust was quite white. Way too hot for me.

Get a wideband and take note of the leanest conditions, or log the runs. Unfortunately, I don't have a small enough laptop to do logging while on the track.

 

[1LE]

Before I got rid of my A/C condensor, my coolant temps would get quite high (105C), but that was a good thing as it made the car retard the timing a bit. Peak EGT's were around 875C. Now, without the condensor, my coolant temps never change (same 84C roughly that I see on the expressway), however, my EGT's are way higher (I shift at 975C at 6k rpms in 3rd gear, then roll into 4th easy, just to keep the EGT's down) because my timing is so high now.

 

[drivemusicnow]

I think you're looking for too much of a definite answer. Here are the variables that I see as far as fuel and boost goes.

You do NOT want to knock at the track, so thats my number 1 concern when tuning. no knock, even after running the motor hard for a full session. To me this means running the highest octane possible. a blown motor is more expensive than using better gas.

People who have wideband o2's and even with just the stock O2 sensors need to consider that running leaded race fuels shorten the sensor's lifespan significantly.

You are quasi limited by whats at the track, unless you want to bring your own.

If you do want to run pump gas, go with the highest octane possible, as well as using a conservative tune on that same gas. I would keep boost low as well.

The best way to learn is to be conservative in your tune, and then log while you're racing. See what temps you are reaching, as far as exhaust, engine oil, coolant, as well as knock, timing etc. Go from there. Just realize that hotter days will require an even more conservative tune.

Alchy/water injection is a great idea for road racing. I'm still putting together my car, however after doing some research, and seeing logged results on some other cars while racing, I think its a very cheap safety factor. I think that I would just use water at first, and add it only as a safety factor. (As in I wouldn't change the tune for it)

 

[Slow old poop]

I see there's a thread on fuel for drag racing. What do you road racers run? And does anyway run water/alcohol injection on road courses (or is it too risky)?

I ran a 3000GT with water/alcohol injection and 110 oictane leaded race gas. Even at 24 psi, we got no knock. (At 24 psi we got spark blowout, but that's a different problem). The beauty of w/a injection is that it cools the pistons, helps prevent knock, and lets you run higher boost safely. DO NOT run it without an indicator light that tells you when the water tank is empty, or you might burn a piston. It also helps to run a data acquisition system that reads out the knock count. If you rely on the w/a system to prevent knock, you better have a way of knowing when it ain't working no more.

By the bye, NASA assesses 7 points for w/a injection, so somebody over there must think it's helpful. We were going to put w/a on my 90 Eclipse GSX until I learned about those 7 points.

Rich

 

[Slapnut]

just a little fyi,

the cars factory computer will adjust the timing on its own, depending on what octane gas you run. The higher octane causes the car to retard the timing!?! For the guys running a after market comp system, or dsmlink this problem can be dealt with. On a factory computer system, its almost impossible to get around.

 

[MrSparkle]

The higher octane causes the car to retard the timing!?!

That's news to me. How does that work?

 

[1LE]

That's news to me. How does that work?

The only things I can think of that retard the timing are: coolant temp high, higher air flow, and knock.

 

[mavisky]

Timing gets retarded based upon airflow. Those on larger injectors take airflow away from the ecu and it moves the airflow/timing maps into a lower airflow zone and that causes the timing to be bumped up. Now you can retard the base timing to compensate, but then you lose off boost performance as a tradeoff.

 

[MrSparkle]

Timing gets retarded based upon airflow. Those on larger injectors take airflow away from the ecu and it moves the airflow/timing maps into a lower airflow zone and that causes the timing to be bumped up. Now you can retard the base timing to compensate, but then you lose off boost performance as a tradeoff.

Yes that is true for piggybacks.

I'm still waiting for the statement that the ECU decreases timing based on octane to be addressed. Since the ECU can't determine the octane rating directly (only indirectly) I'm wondering how that works, and how it factors into the routine that reads airflow and lookups how much fuel and timing to use.

As far as I know the main way the ECU compensates for octane is via the knock sensor. And running higher octance doesn't produce more knock so I'm wondering why timing would be decreased.

 

[mavisky]

Yes that is true for piggybacks.

I'm still waiting for the statement that the ECU decreases timing based on octane to be addressed. Since the ECU can't determine the octane rating directly (only indirectly) I'm wondering how that works, and how it factors into the routine that reads airflow and lookups how much fuel and timing to use.

As far as I know the main way the ECU compensates for octane is via the knock sensor. And running higher octance doesn't produce more knock so I'm wondering why timing would be decreased.

The ecu has no way of identifying the fuel characteristics in our cars. Racing fuel is however more dense and you will have to lean the car out to run better even on the same boost you would run on pump gas. This would mean that with a piggyback style controller you'd end up in that lower airflow/higher timing area of the map I was talking about.

 

[MrSparkle]

Yes, I understand that, but that doesn't explain this statement: "the cars factory computer will adjust the timing on its own, depending on what octane gas you run. The higher octane causes the car to retard the timing!?!" What you are describing is an adjustment of timing based on your adjuments to airflow and is an "increase" in timing as opposed to the "decrease" in the original statement. So I'm pretty sure me and you are on the same page here.

Also, the ECU does store an Octane value (you can log it with DSMLink). According to the DSMLink manual:
"Octane rating as viewed by the ECU based on long term knock"

I'm not sure how the ECU uses this, but according to the DSMLink manual one of the internal adjustments with DSMLink is to reset this value every time the car is started.

 

[mavisky]

Yes, I understand that, but that doesn't explain this statement: "the cars factory computer will adjust the timing on its own, depending on what octane gas you run. The higher octane causes the car to retard the timing!?!"

I'm not explaining that statement because its not true. The ecu may make a slight adjustment in its low-hi throttle fuel trims based upon the fact that the racing fuel will come across the o2 sensor as being rich. If you don't correct for it then it will make some slight adjustments to those trims, but they won't affect wot and certainly won't move far enough to drastically affect timing either.

Also, the ECU does store an Octane value (you can log it with DSMLink). According to the DSMLink manual:
"Octane rating as viewed by the ECU based on long term knock"

I'm not sure how the ECU uses this, but according to the DSMLink manual one of the internal adjustments with DSMLink is to reset this value every time the car is started.

Basically, if I understood it correctly last time it was explained to me, is that the ecu can and will change the timing maps over time. For instance if you run stock boost on 94 octane all day every day and the ecu never sees knock it may over a long period of time gradually bump of the timing within the timing map. Were you to run 91 octane and 20psi through a 14b, it would do the opposite and probably at a faster rate.

I'm sure Steve could come back in here and explain things 10x better than I am right now, you may want to give him a pm.

 

[Slapnut]

Ignition timing is the single most critical adjustment for a gasoline engine. Assuming the engine is in good mechanical condition, there are no vacuum leaks, and the fuel mixture is correct, then the ignition timing can affect the net power yield from the fuel; the end result can significantly change a vehicle's mpg. Thus, for optimum fuel economy, timing must be optimized. Three types of timing are used for gasoline engines. They are:

1. Static timing;
2. Mechanical (centrifugal); and
3. Pneumatic (vacuum) - mechanical.

Static timing establishes a physical relationship between engine crankshaft position and the distributor. This is fixed and should not change.

Since fuel burns at a relatively fixed rate (i.e., time to burn is in milliseconds) then the faster the engine runs, the sooner the fuel must be ignited so that the millisecond time frame will remain constant. Pre-computer assisted vehicles use mechanical and pneumatic-mechanical devices to accomplish these timing advances.

Computer assisted vehicles use various sensors to modify the computer controlled timing program. A manifold vacuum and/or barometric pressure, throttle position, engine RPM, coolant temperature, and vehicle speed sensor all modify the timing program. The timing program changes are the equivalent of centrifugal and vacuum timing devices formerly used. Computer controlled engines change timing more rapidly than mechanical systems. Computer systems are more closely attuned to optimum timing points than the former mechanical devices. Optimum timing results in optimum fuel economy and reduced tailpipe emissions. Some manufacturers have field serviceable computer calibration chips. These chips modify the computer program and profile for that particular vehicle with specified accessories and equipment. If a vehicle has an improperly calibrated chip, reduced power, lowered mpg, and poor driveability may result. Some aftermarket "hot-rodders" replace calibration chips to optimize engine output for racing purposes. Generally, these lower mpg and increase exhaust emissions. Some are illegal for on-road usage.

Each manufacturer specifies different diagnostic techniques to test for each sensor and for the correct engine calibration chip. Some first generation and most of the latest generation systems use a self testing diagnostic system to detect a non-standard calibration chip. These types provide "memory codes" for failed sensors. All vehicles still require correctly adjusted static timing. In distributorless engines, static timing is accomplished by a crankshaft or camshaft sensor. These sensors must be correctly installed to accomplish correct static timing. Exact procedures MUST be adhered to in establishing this timing reference point. Some manufacturers do provide some checking specifications for timing advance for certain driving conditions. Some use a portable recording device to validate computer operation during specified driving cycles. Others give no "dynamic" timing tests for computer timing and fuel profiles. These require in-shop sequential testing procedures.


Modern vehicles now use computerized engine management systems that can react to engine knock and retard ignition timing if low octane fuel is being used. Consequently cars are now being manufactured with very high compression ratios that appear to give good fuel economy and at the same time good performance. This combination does assume that fuel of adequate octane is being used.

 

[Slapnut]

what i was saying is that high octane will run rich, the o2 sensor reads that, changing the time to run better. From what i learned in school (which was a while ago) we where told running lets say 100 octane in you chevy caviler wouldn't due much because of the computer changing the settings / retardingthe timing, but from what i read in my above post i had it backwards... it advances on higher octane and retards on lower.

so excuse my bass ackwards statement.

 

[eclipsegsx1736]

Before I got rid of my A/C condensor, my coolant temps would get quite high (105C), but that was a good thing as it made the car retard the timing a bit. Peak EGT's were around 875C. Now, without the condensor, my coolant temps never change (same 84C roughly that I see on the expressway), however, my EGT's are way higher (I shift at 975C at 6k rpms in 3rd gear, then roll into 4th easy, just to keep the EGT's down) because my timing is so high now.

I've always heard (and experienced myself) that timing retard causes higher EGTs, not the other way around. When timing is pulled, combustion occurs later, causing the combustion to occur closer to the exhaust stroke, which sends fire thru the manifold, giving you a higher EGT. This used to happen to me when I had bad phantom knock, the timing would dip WAY down and the EGTs would shoot up very fast. Also, you'll notice while doing logs, that if you pull a few degrees of timing during a pull due to knock, right at that second the EGT will increase quite a bit.

 

[1LE]

I've always heard (and experienced myself) that timing retard causes higher EGTs, not the other way around. When timing is pulled, combustion occurs later, causing the combustion to occur closer to the exhaust stroke, which sends fire thru the manifold, giving you a higher EGT. This used to happen to me when I had bad phantom knock, the timing would dip WAY down and the EGTs would shoot up very fast. Also, you'll notice while doing logs, that if you pull a few degrees of timing during a pull due to knock, right at that second the EGT will increase quite a bit.

Correct, timing retard causes higher EGTs. However, so does excessive timing advance! EGT just tells you something is wrong, doesn't tell you which way it's wrong.

 

[JessesTalon]

high torque conservative tune on race gas will be your best bet