Rotary Fuel and Testing

[C. Ludwig]

With a low (stock) compression rotary engine there is no reason to run high octane race fuel. Us IT folks will do just fine on 87 pump. But what to do about fuel testing? Has anyone found pump fuel that consistently passes SCCA fuel tests? Or is the only option to run expensive race fuel that may in actuality cost HP?

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Chris Ludwig
08 ITS RX7 CenDiv

[ddewhurst]

Chris, what's your concern about using pump gas. Is there some new rule about fuel?

Have Fun
David

[Mike Spencer]

Originally posted by ddewhurst:
Chris, what's your concern about using pump gas. Is there some new rule about fuel?

Have Fun
David

Chris, forgive me for putting words in your mouth...

I believe his concern is whether pump gas from fill-in-your-favorite-station will pass fuel testing. For many of us, what they do with that bottle of fuel is a black art!


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Mike Spencer
NC Region
ITA/7 RX-7 #60
1990 RX-7 Convertible (street car)

[C. Ludwig]

That's exactly what I was saying. It's very likely pump fuel won't pass the pee test because of the additives. Especially winter blends that are oxygenated.

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Chris Ludwig
08 ITS RX7 CenDiv

[bldn10]

"Is there some new rule about fuel?"

Yes. Per Fastrack effective 1/1/05 the old fuel specs were abolished in favor of a list of approved fuels, each w/ its own spec. However, the list has yet to materialize and we appear to be left w/o fuel specs so I don't see how there can be any testing at the present time. I hear that the brains that came up w/ this crazy idea are re-thinking it. There is some discussion of this in the Fastrack thread in the Rules forum.

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Bill Denton
87/89 ITS RX-7
02 Audi TT225QC
95 Tahoe
Memphis

[Andy Bettencourt]

Chris,

I don't raise a stink about much of the "National" stuff (belts, H&N, etc), but the day I can't pull into an Exxon/Mobil and fill our jugs with Regular Unleaded for the RX-7's......is the day I go mental.

AB

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Andy Bettencourt
New England Region, R188967
www.flatout-motorsports.com

[Daryl DeArman]

Originally posted by C. Ludwig:
With a low (stock) compression rotary engine there is no reason to run high octane race fuel...Or is the only option to run expensive race fuel that may in actuality cost HP?

Running a higher octane than your motor requires is not gaining you any horsepower.

HOWEVER, there are positive gains to be found in certain race fuel blends over pump gas that don't have to do with octane ratings.

FV's run race fuel (motors are lower compression than a rotary) they do make more power on certain race fuels than pump gas and it sure isn't because they require more than 89 octane!

Rotaries have very long and narrow combustion chambers. Next time your tank is near empty try a few gallons of race fuel and let us know if you notice any difference...

I think you'll be pleased but may decide it isn't neccessary to run it all the time.

[C. Ludwig]

Originally posted by Daryl DeArman:
Running a higher octane than your motor requires is not gaining you any horsepower.

HOWEVER, there are positive gains to be found in certain race fuel blends over pump gas that don't have to do with octane ratings.

FV's run race fuel (motors are lower compression than a rotary) they do make more power on certain race fuels than pump gas and it sure isn't because they require more than 89 octane!

Rotaries have very long and narrow combustion chambers. Next time your tank is near empty try a few gallons of race fuel and let us know if you notice any difference...

I think you'll be pleased but may decide it isn't neccessary to run it all the time.

Perhaps. I wish you would of put that bug in my ear before I got back from the dyno today.

Thanks for the words of wisdom guys. Looks like I'll have to go back through the Fastracks and re-educate myself.



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Chris Ludwig
08 ITS RX7 CenDiv

[jduncan569]

It still was a good dyno trip, race gas or not.

[bldn10]

I must apologize because I went back and looked closer at the March Fastrack and saw that the proposed new fuel rules were NOT passed. However, that seems to be the direction we are headed - in the April Fastrack someone wrote a letter opposing the new fuel rules and it and the response was: "Allow pump gas (Cohen). Pump gas would be inconsistent due to blending and seasonal changes, and a number of pump gases do not pass our current fuel testing procedures."

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Bill Denton
87/89 ITS RX-7
02 Audi TT225QC
95 Tahoe
Memphis

[C. Ludwig]

I saw that and it is what got me thinking. IMO there needs to be a flood of letters to the national office on this topic. I won't pay for race fuel without good reason and especially won't submit to the SCCA allowing the tracks to have a fuel monopoly.

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Chris Ludwig
08 ITS RX7 CenDiv

[its66]

yeah, I saw that too.

Jim (Cohen)
ITS66

p.s.It sounds like the testing method is what is flawed, not the ability to use pump fuels. (FWIW, I know ablsolutley nothing about fuel tests other than what is in the GCR)

[This message has been edited by its66 (edited March 10, 2005).]

[Daryl DeArman]

The problem is that there are too many different chemical signatures in the various pump fuels for the test to know exactly what it is. All the tests can determine is what the DC is (dielectric constant) and whether certain chemicals are present (Reagent A and D tests).

I could make, (well I couldn't, but someone could) make an exotic fuel blend that had a dc within spec and passes the regeant tests. The tests would not be able to kick this fuel as long as it is within specs.

Along comes pump fuel user and he gets kicked because something that refinery X puts in their fuel this time of year puts the fuel outside the DC window or tests positive on the other tests for containing some prohibited chemical.

As I see it, the best solution is to offer SEVERAL accepted fuels including a specific pump gas in the event supps. They then have a control sample of each to compare your fuel sample with. As long as your sample matches one of the control samples your golden. If not, you have done something to it or are using something other than what is approved...you get kicked...no need to find out what it was or what you did. Really quite simple.

[Matt Rowe]

But even offering a wide range of fuels (including pump gas) is not going to prevent problems. Cars that run track a one week and track b two weeks later are still going to have residual gas left in the tank. Then you factor in the sensitivity of DC testing to fuel age and evaporation and flushing the tanks between events ends up being the requirement.

It really appears the problem is in the testing. Dielectric Constant does not tell us enough about the additives in the fuel. Logically that would mean we need some other means to test for them. If the ultimate goal is to keep things like C44 and other harmful additives out of the tank we need to test for them.

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~Matt Rowe
ITA Shelby Charger
MARRS #96

[Daryl DeArman]

Matt,

As long as the list of approved fuels contains enough of a choice AND you choose a common enough option there shouldn't be a need to drain tanks from race to race, at least in regards to the tests.

According to the highdesert site aging and addition of two-stroke oils will affect the numbers slightly. There are also correction tables for temperature.

On this list http://www.ridgenet.net/~hideseng/dc_list.htm are only a handful of fuels that fall outside the DC numbers for rotaries. C-44 is not one of them.

The problem with designing the tests to look for a specific additive, is masking agents and/or other just as dangerous additives can be used. That is why I think the best solution is to test against a known control sample...either it is the same or it is not!

[its66]

Daryl,
Thanks for the quick lesson.

I would be concerned if Brand X pump gas was the only approved street fuel in my area and Brand Y buys out brand X. Think how often the fuel companies buy out each other's locations. In the last 20 years, Shell has left our region 3 times. The locations are sold, Brand x goes in. Three years later, Shell buys them back, and Brand X goes away. Will SCCA cover all these possible scenarios, or react quickly when they happen?

I realize this is a situation which just calls for common sense to be applied at the local level when/if something similar did happen. I haven't had a lot of luck in relying on the common sense of others lately.

The "known sample" is a great idea. As I think about it, it might be better for the regions to administrate this. A dozen or so locally available major fuels are purchased, marked, sampled and displayed in the tech area at each event. IF the acceptable fuels were listed in the supps and readily available, compliance should be no problem-if you read the supps.

Just thinking out loud..again

Jim

[benspeed]

Originally posted by Andy Bettencourt:
Chris,

I don't raise a stink about much of the "National" stuff (belts, H&N, etc), but the day I can't pull into an Exxon/Mobil and fill our jugs with Regular Unleaded for the RX-7's......is the day I go mental.

AB

Yar - I'm with Andy - pitch a fit like a 5 year old with no nap.