Why do sprint cars use mechanical fuel injection?

[Rollover]

Ive always wondered why sprint cars still use mechanical fuel injection and late models use carbs? Is there a performance advantage of one over the other?

[CIRF]

Rollover, I am far from an expert on sprint car engines. However, the question you pose is one that is raised from time to time.

That said there are sprint car sanctions that allow both mechanical fuel injected and carbureted engines in the 305 classes. Most of the higher budget 305 sprint teams have gone to the mechanical fuel injection, but where the rules allow there are still teams running 305 sprinters with carburetors. As far as I know the big dogs, the fire breathin' 410's, are all run mechanical fuel injection. If I'm mistaken I'm sure someone more adept than myself will set the record straight. The USAC Silver Crown cars (AKA big cars, champ cars, dirt cars) are 355 cubic inch engines and they are mandated to run mechanical fuel injection.

There has been talk over the years of possibly allowing electronic fuel injection systems, especially in the USAC Silver Crown division and from what I've read there is conflicting opinions as to whether going electronic would control costs or not. One thing is for sure, EFI would be much easier to dial in and maintain, according to the mechanics that crew chief the Silver Crown cars.

The only way I'm aware of to increase or decrease the amount of fuel delivered by a mechanical injection system to the cylinders is to run a different size fuel return jet that allows excess fuel to be dumped back into the tail tank. The bigger the return jet the more fuel that is bypassed back to the tail tank and not available to the engine and vise versa. I understand that statement is a vast generalization but essentially true. Advocates of EFI for sprints and Silver Crown cars say that EFI makes it much easier and more precise when making changes to the fuel delivery system and they can electronically make adjustments to compensate for atmospheric conditions.

[Rollover]

I was just curious and nobody i had talked to seemed to have a real answer. thanks for the reply

[CIRF]

I've seen the subject discussed on a midget/sprint car/Silver Crown board about a year or so ago. What raised the question was USAC mandated the Silver Crown cars to use ethanol (basically moonshine made from corn) as opposed to methanol, which these days is made by oxidizing methane. The switch to ethanol lasted only 1 season and further decimated Silver Crown car counts due to the fact that none of the mechanics knew exactly how to tune the mechanical fuel injection to run and live long enough to complete 100 mile races on the 1 mile tracks. There were widespread sour sounding engines and total engine failures from the get go. The reason for the 1 year switch to ethanol was due to ethanol sponsorship of the series that had little or no effect on the purses of the Silver Crown races but caused all kinds of problems keeping the engines running at full power and even caused a fair amount of catastrophic failures. Thus the low car counts.

At the time of the ethanol debacle in the Silver Crown series the question was raised as to why USAC didn't allow electronic fuel injection. I never read a credible answer from a credible source at that time or since. I am certainly interested as to the reason, as well.

I'm going to go out on a limb and say part of the reason is going to EFI would instantly put tens of thousands of dollars worth of equipment into instant obsolescence and require the car owners to start at ground zero with technology that would probably be completely foreign to the crew chiefs and mechanics.

Dam good question, Rollover.

[6565]

I will add that as a sprint car driver, I would not want to be upside down after a crash and have fuel spilling out of the carb bowls and catching fire. I know there are 2 barrel sprints in some areas-just saying I don't think I would do it.

[CIRF]

That's a very good point 6565. One that hadn't occurred to me.

[buster83]

the mechanical fuel injectors have been very dependable for decades.

[Stede Bonnet]

I will add that as a sprint car driver, I would not want to be upside down after a crash and have fuel spilling out of the carb bowls and catching fire. I know there are 2 barrel sprints in some areas-just saying I don't think I would do it.
While this use to be a problem, rollover valves installed in the carbs nullifies this problem.


the mechanical fuel injectors have been very dependable for decades.This is true and is not really the point. The Mechanical aspect isn't really the problem I don't think, it's the constant flow aspect, essentially intended for full throttle applications. There is a lot of area for performance improvement between idle and full throttle that could be realized with EFI or a re-imagined mechanical. I understand tradition and I generally try to respect it, but I don't care much for exclusion, like making everyone run a chevy or a ford, these kind of rules stifle passion, creativity and enthusiasm. I'd like to see mechanical and EFI run in competition with each other. The mechanical will always win in the reliability catagory, but EFI may offer greater efficiency and smoother part throttle performance when things are slick. When the track is heavy neither would have the advantage, as full throttle will be prevalent in those conditions. So opening the rules to include both could provide competition inside the competition itself. Inclusion, not exclusion let sprints evolve, they didn't start out as 410 monsters, but they evolved, became truly awesome, let's continue to improve, to grow. In life your either growing or dying, there is no 3rd direction.

[CIRF]

Steve, you delve into an area that I have little to no knowledge. My racing experiences are long since over and they were exclusively limited to carbureted dirt late model engines. I somewhat understand that stuff.

That said I have often wondered why modern day sprint owners and sanctions have not made the conversion over to electronic fuel injection. Interesting topic. Maybe there is someone out there that brings knowledge and experience to the discussion. I for one would be interested in digging deeper into the subject.

[vande077]

I remember back in the 80's when Carburators were more common on Sprints (and production vehicles for that matter). Lots of wrecks caused at the drop of the green flag when a car would "bog down" or "stutter" (just like your street car did with a carburetor).

Once everyone went to Fuel Injection, those types of incidennts are basically non-existent (still happen occasionally, but I remember it being every other race or so when I was a kid in the 80;s).

[CIRF]

I remember back in the 80's when Carburators were more common on Sprints (and production vehicles for that matter). Lots of wrecks caused at the drop of the green flag when a car would "bog down" or "stutter" (just like your street car did with a carburetor).

Once everyone went to Fuel Injection, those types of incidennts are basically non-existent (still happen occasionally, but I remember it being every other race or so when I was a kid in the 80;s).

Makes sense vande. On most of the pace lap coming to the green they didn't have an opportunity to "clean" out the engine. It could be bit of a problem with the stock cars but they could hit the clutch and blow it out which obviously made it less of a concern.

The question of EFI vs. mechanical is a bit of a different animal. Other than the USAC Silver Crown ethanol controversy a few years ago I don't recall much, if any, discussion as to the pros and cons of each or the compatibility of EFI to the full on 410's or Silver Crown cars.

It may be a case of rendering hundreds of thousands of dollars worth of mechanical FI equipment obsolete and useless.

[Stede Bonnet]

I think most of the hesitancy is rooted in fear, but not everyone would change over because it requires alternators and batteries, so the mechanical guys would still have a weight advantage. I've been checking some rules this weekend and a lot of tracks don't have a rule regarding induction, only that they use alcohol and a certain hoosier tire. USAC seems to exist on its own planet, constantly tripping over its own feet, which is sad and regrettable. Their missteps I think have held silver crown champ car racing back, the same is going on right now in WoO/Lucas late models. Those organizations are trying to write rules to enhance and shrink the box they play in, but have only succeeded in suffocating the baby and driving costs into the stratosphere, with tungsten axle tubs, bird cages and brake rotors. Trying legislate every last nut and bolt drives "UP" cost and hinders ingenuity and creativity, resulting in further expense. That fuel debacle in Silver Crown was an unnecessary and seemingly politically motivated move made without proper knowledge or reason.

The "Spec Sprints" in California use 2 barrel carbs and starters, they are required for initial start up. If you have to be rolled off at the start you go to the rear, but once race is underway if you need a push its not an issue. Very competitive class, steel block/head 350's, enough power to smoke the RR thru the turns too.

[CIRF]

First off, most everything I've learned about the Silver Crown ethanol debacle is that there was a fair amount of money involved. Most of which was not integrated into the race purses. But instead it was funneled to USAC. Now, I got that info second hand and it may well be erroneous but it was bandied around racing circles extensively and without any push back from USAC. And, it was costing way too much money since zeroing in on the correct combination proved to be very difficult due to trial and error being the only way to get things right.

The ethanol deal came along not long after the Gold Crown disaster and there were owners that had a very bad taste in their mouth as a result of that and the ethanol disaster sealed the deal for several of them. That's why there were only 14 or 15 cars at Du Quoin back in 2013 & 2014. I have to admit that I'm not at all familiar with the overall legislation of USAC's three national divisions. For those of us who are hard core Silver Crown enthusiasts we rejoiced the hiring of Indiana Andy Hildebrand and now Levi Jones. Andy literally brought the Silver Crown division back from dead and made it relatively healthy again. It looks like Levi is carrying on Andy's work and progress. Let's hope so.

I still believe as significant reason for continuing with the MFI is the cost of obsolescence and the fact that the guys working on the engines and making the cars go fast know the MFI implicitly.

I have a friend that is a partial owner of a very competitive Silver Crown car and the MFI vs. EFI will be a topic of conversation for the next time we get together.

[buster83]

if they were efi it would be a pain in the butt all the extra weight and electrical fires and constant programing the ecm to so many different tracks i just don`t see it happening in the near future.

[Stede Bonnet]

if they were efi it would be a pain in the butt all the extra weight and electrical fires and constant programing the ecm to so many different tracks i just don`t see it happening in the near future.

Electrical fires? One of the appealing elements of (Kinsler)EFI is it can adapt on its own to changes in atmosphere, but it does require wires and sensors, a battery and an alternator, but I've been assured the programming is about as basic as using an app on your phone to find a restaurant. The cars we drive everyday have EFI and I don't notice vehicle fires that often, even in a crash... MFI and EFI both have their pros & cons, I don't see why allowing one would obsolete the other. Racing usually dictates that the lighter option is always best and MFI is that, but it has some warts of its own that are overlooked by those who love and admire those systems. EFI does requires more components and therefore is more weighty, but eliminates some of the tuning and temperamental headaches that can arise in MFI. MFI is at its optimum at WOT, but EFI fills in the gaps in the part throttle zone while matching performance at WOT. EFI also now utilizes the same type of mechanical fuel pump as MFI, so no more fear of runaway fuel pumping in a crash. To me it could be an exciting match up, especially since EFI comes in the traditional 8 stack formation that most traditionalists are so fond of and look so freaking cool!

Having said all that and as I continue to research the best way to proceed to start an economy non-wing sprint car class in my state, the Joe Hunt Spec Sprints I think have about the least intimidating package for the novice that still has enough HP to be exciting for the fan and they use 360 w/2barrel, 500HP. Very simple, reliable and basic, I'm excited!!!

Be well my friends.

[lazyifoto]

Sprint cars don't have a battery so fuel injection "I believe " has to be mechanical. ...also again I believe that alot of sprint car motors plumb the injectors directly into the head and only receive air through the injector tubes.

[Stede Bonnet]

Sprint cars don't have a battery so fuel injection "I believe " has to be mechanical. ...also again I believe that alot of sprint car motors plumb the injectors directly into the head and only receive air through the injector tubes.

Most sprint cars don't have batteries, but some nowadays, do. The Joe Hunt Magneto Wingless series mandates a starter and a battery on every car, the battery is usually under the seat. The injectors are located in the manifold on most every sprint that utilizes MFI, no tuned port. According to the rules of most series that I've read they don't list what type of induction you must use, only alcohol, at least not WAR or BOSS. Now the Elite series guys in Texas stipulate MFI and a RS305.

[CIRF]

Most sprint cars don't have batteries, but some nowadays, do. The Joe Hunt Magneto Wingless series mandates a starter and a battery on every car, the battery is usually under the seat. The injectors are located in the manifold on most every sprint that utilizes MFI, no tuned port. According to the rules of most series that I've read they don't list what type of induction you must use, only alcohol, at least not WAR or BOSS. Now the Elite series guys in Texas stipulate MFI and a RS305.

Since WAR has merged with POWRi I've done some investigating to become familiar with the rules given that WAR will be racing at several tracks near to us during the 2017 season. WAR actually has very few rules and it seems they are wide open as to engine guidelines. The rules state that there are no engine rules. That's one reason I kinda' like the WAR series. It's truly a grass roots outfit, for sure.

This Elite Series in Texas seems to be gaining some popularity. A buddy of mine who lives in Oklahoma has attended several of their shows and really likes them.

The URSS Racesaver 305 sprints can run carbs or MFI. They have been the support series at The Belleville Midget Nationals the past couple of years and they do a good job. These cars are interesting in that you can tell exactly who's running MFI and who's running carbs.

[Stede Bonnet]

...The URSS Racesaver 305 sprints can run carbs or MFI. They have been the support series at The Belleville Midget Nationals the past couple of years and they do a good job. These cars are interesting in that you can tell exactly who's running MFI and who's running carbs...Interesting, what differences do you notice between 4 barrel and MFI?

[CIRF]

Interesting, what differences do you notice between 4 barrel and MFI?

It's the sound of the engine that is the difference. The cars with carburetors sound much like a late model with the distinctive cackle of the exhaust note during deceleration. The carburetor engines also have a distinctive sound upon acceleration, as well. They have a deeper sound unlike the MFI engines which have a bit more of whine and have a higher pitched sound.

It's easy to tell the difference.

[Stede Bonnet]

It's the sound of the engine that is the difference. The cars with carburetors sound much like a late model with the distinctive cackle of the exhaust note during deceleration. The carburetor engines also have a distinctive sound upon acceleration, as well. They have a deeper sound unlike the MFI engines which have a bit more of whine and have a higher pitched sound.

It's easy to tell the difference.

Hey CIRF,
This is off topic, but I saw this morning on IOW that the Lucas Oil Southern States Midget D2 cars are going to be in Georgia in february!!! I can't wait, never seen a midget race in person and its only like 2 hours from my house.

[CIRF]

Hey CIRF,
This is off topic, but I saw this morning on IOW that the Lucas Oil Southern States Midget D2 cars are going to be in Georgia in february!!! I can't wait, never seen a midget race in person and its only like 2 hours from my house.

Stede, although the division II midgets provide very good and exciting racing they aren't the full on USAC, POWRi or ARDC midgets. Be advised that the D II midgets look nearly identical to the full on midgets there is a lot of horsepower difference. The D II midgets are restricted to using OEM 4 cylinder engines of several different manufacturers.

They are:

GM Ecotec 2.4L (LE5), or 2.2L (L61)
Honda 2.4 L (K24A1)
Chrysler World Engine 2.4L
Toyota 2.4L (2AZ-FE)
Ford/Mazda Duratec 2.3L (23 I-4/L3)
GM Quad 4 2.3L and 2.4L
Ford 2.0L Focus/Scream Pre-2004 (see notes)

They can't be massaged very much and must use OEM blocks, heads, camshaft's and crankshaft's. No porting of the heads is allowed. The lower end can be balanced but no lightened or knife edged crankshaft's are allowed. They can choose to run either MFI or EFI either with plenum or individual runner intake systems. They are basically powered by an OEM engine and a clutching system with starter is optional.

They put on a very good show but are noticeably slower than the full on USAC/POWRi/ARDC midgets. But, the engines cost way, way less than the full on TRD's and Esslinger's.

This is a very good purse and I would highly recommend attending the Georgia show. I don't think you'll be disappointed. Since you haven't seen the midgets in person you won't have the full on midgets as a frame of reference thus you'll probably enjoy it even more. The difference between the full on midgets and the D II's is very much akin to the difference between a super dirt late model and a crate late model. From the outside they look identical but what's under sheet metal is a whole other beast.

Go, and have a great time! This might be the biggest purse these guys have ever raced for and there should be a ton of cars!! Let us know how you liked the show.

[Stede Bonnet]

Stede, although the division II midgets provide very good and exciting racing they aren't the full on USAC, POWRi or ARDC midgets. Be advised that the D II midgets look nearly identical to the full on midgets there is a lot of horsepower difference. The D II midgets are restricted to using OEM 4 cylinder engines of several different manufacturers.

They are:

GM Ecotec 2.4L (LE5), or 2.2L (L61)
Honda 2.4 L (K24A1)
Chrysler World Engine 2.4L
Toyota 2.4L (2AZ-FE)
Ford/Mazda Duratec 2.3L (23 I-4/L3)
GM Quad 4 2.3L and 2.4L
Ford 2.0L Focus/Scream Pre-2004 (see notes)

They can't be massaged very much and must use OEM blocks, heads, camshaft's and crankshaft's. No porting of the heads is allowed. The lower end can be balanced but no lightened or knife edged crankshaft's are allowed. They can choose to run either MFI or EFI either with plenum or individual runner intake systems. They are basically powered by an OEM engine and a clutching system with starter is optional.

They put on a very good show but are noticeably slower than the full on USAC/POWRi/ARDC midgets. But, the engines cost way, way less than the full on TRD's and Esslinger's.

This is a very good purse and I would highly recommend attending the Georgia show. I don't think you'll be disappointed. Since you haven't seen the midgets in person you won't have the full on midgets as a frame of reference thus you'll probably enjoy it even more. The difference between the full on midgets and the D II's is very much akin to the difference between a super dirt late model and a crate late model. From the outside they look identical but what's under sheet metal is a whole other beast.

Go, and have a great time! This might be the biggest purse these guys have ever raced for and there should be a ton of cars!! Let us know how you liked the show.

Thanks for the info. I saw what you mean by cost, I think an SR-11 from Stanton is like $36K !!! Ouch. How long have D2 midgets been around?

[CIRF]

Thanks for the info. I saw what you mean by cost, I think an SR-11 from Stanton is like $36K !!! Ouch. How long have D2 midgets been around?

I'm not positive Stede, but I believe this will be the 3rd season for the POWRi D II. I know it hasn't been more that 4 seasons.