CLASS RACER FORUM - to all 85-92 efi racers

Jim Wahl asks...

"Help me understand something here."

John didn't answer any of this, so, I'd like to try, point-by-point.

>>>>I don't care how much more duration your cam is over stock.

And, you shouldn't care. Cam duration is not a factor, since the NHRA decided to open up the stock cam duration rule in the mid-eighties, and let anyone run any duration they choose, INCLUDING turbo cars. No point here...

>>>> I don't care how much more than stock valve spring you run.
Valve springs were part of the unlimited cam duration package that NHRA introduced about 1985. Any spring presure is legal, INCLUDING any valve springs on turbo cars, so, again, there's no point, here.

>>>>I don't care who's aftermarket non-stock aluminum heads you have.
NHRA cares, and assess increased "factored" horsepower for racers who attach them to their engines. It's not an upgrade that NHRA hasn't looked at and added horsepower to, if you choose to run them. No freebie, and no point, here.

>>>> I don't care how big your fuel injectors are.
I am not familiar with NHRA's rules regarding fuel injectors, so I don't have an answer for this one, except to say that I'd imagine that stock "pound" fuel injectors are probably required in a Stock class. Also, nearly all turbo cars are injected, so whatever the normally-aspirated cars are using, that upgrade should be available to a turbo competitor, too. You MIGHT have a point here; I don't actually know.

>>>>I don't care how you set the screws on your carburetor.
As far as I know, "setting screws," adjusting the mixture, (or secondary opening rate?) has no effect on performance beyond normal tuning, which has always been legal, practically, since day one. No point, here, either, that I can see...

>>>>Why do you care how much boost I choose to run?
That's like asking, "Why do you care how many cubic inches I run," because boost is simply a way of putting more air through an engine, making an engine produce power like it is larger than it really is.

Boost is measured, usually, in pounds per square inch, though there are several other ways it is described ("bar," "atmospheres," etc...)

Generally speaking, increasing the amount of boost on any given engine will result in an increase in the power output. That's why turbos and superchargers exist, to put more air through an engine, so more fuel can be burned in the same amount of time, resulting in a power increase.

If it's such a non-issue, why would YOU, Jim, care if NHRA chose to monitor the amount of boost you run???

When an engine is dyno'd at the favtory, the SAE sets standards for all sorts of conditions, such as air inlet temperature, exhaust system specifications, coolant temperature, etc., etc., etc... correcting things they can't control, such as barometric pressure, to a set, predetermined standard.

If the engine is using forced induction, the amount of what we call "boost" is a part of that set of specifications. It is a critical parameter, because if it is increased, the reasonable expectation is that the power will increase. Lower it, and power will usually go down, all other things being equal.

More power will almost always lower the e.t. of a Stock-Class drag car.
And, to a large extent, increased boost = increased power.

The horsepower figures that the factories supply NHRA with are based on those manufacturers' dyno tests, and at prescribed boost levels on forced induction engines.

Once they have the factory numbers, NHRA then assigns a factored horsepower to the engines in question that may vary from the factory horsepower, but not always. The '"wonderful" AHFS system supposedly takes care of any "mistakes" made by the NHRA Tech Dept. in assigning factored horsepower. Riiiiiiiight...

But, the "original, factory horespower information system" only works for forced induction cars, in practice, if engine output is is SOMEWHAT restricted by an adherence to the factory figures for boost levels. Anyone with a piece of baling wire can disable a waste gate on a turbo car and pick up power, maybe a little; maybe a lot... I'm sure it varies from car-to-car.

Here's the rub. Yes, normally-aspirated cars have TONS of options available (and we all know what they are), to go about increasing horsepower, even though they're running in a "stock" class. Cam duration, multi-angle valve jobs, heavy-duty valve springs, lots of RPM's, trick ring setups, and a whole host of power-creating "tricks" can raise the horsepower level of a "stock", normally-aspirated motor to sometimes half-again its factor (and doubtless, even more, in some cases.)

Thing is, the turbo cars have ALL OF THE SAME OPTIONS....

So, where is the problem with (unauthorized) increased boost?

When the intake valve opens on a normally-aspirated engine, all other things being equal, there's only one thing filling that cylinder when the piston makes its trip to the bottom:
ATMOSPHERIC PRESSURE

When that engine was dyno'd at the factory, to get the number that NHRA was supplied with, an SAE standard having to do with barometric pressure was included in the mix to come up with the specific output for that motor. Now, a similar operation was going on with a turbocharged motor, the only difference being it was tested under boosted conditions. Let's say its rating was 300 HP at 10 pounds of boost

Now, NHRA gets the figures for both of those engines and doesn't change either engine's "factor," with both going into the Class. Guide at their original, factory rating.

In qualifying, the guy with the normally-aspirated car does okay.. let's say he qualifies at #10.
The guy with the turbo motor, in at #4 wants a better number, so, he modifies his waste gate to allow 14 pounds of boost. His car instantly picks up another 25, or so, horsepower, and he goes to number one...

I realize that this is a gross over-simplification, but the idea is this:
The guy with the tuurbo car has EVERY OPTION afforded the normally-aspirated car, to make his car faster, PLUS, possibly one the normally-aspirated car does NOT have: BOOST INCREASE.

No matter WHAT the normaly-aspirated car owner does to make his car faster, he still has one, critical, underlying limit on how much air he can put through his engine; HE CANNOT INCREASE THE AMOUNT OF ATMOSPHERIC PRESSURE AVAILABLE TO FILL THE CYLINDER. This is, for the sake of argument, ignoring gains from ram-tuning the intake, which is not much of an option on most Stockers.

The turbo car can increase the available cylinder-filling pressure at the intake valve, if the boost is increased. Upping the boost pressure (all other things being equal) has a dramatic effect on how much air is put through the engine, It can make the difference between a so-so car and a "killer."

If you will check out the number of #1 nat'l event qualifiers in Stock for the last four years, you will find an inordinate amount of turbo cars qualifying number one. I think there was something like over 20-percent of national events in that time frame that had a turbocharged car as the #1 qualifier, although the number of thrbocharged cars actually racing was probably something around a tenth of that.

Something is very wrong with that picture.

Having said that, I would advocate the use of a a telltale boost gauge for turbo and supercharged cars, like the ones that are being used in some road-race organizations to monitor maximum boost. When a car comes in for his weight/fuel check, the Tech could simply look at the gauge and check a list of boost specs for forced induction cars to verify legality. He wouldn't have to be an expert in turbos to check the legality of the operation. That might do something to eradicate this lopsided qualifying situation.

In defense of this opinion (and it's JUST my opinion... nothing more,) I'd like to say that GENERALLY SPEAKING, boost is a measure of how efficient/inefficient an engine is, in using its air. If you have a poor cylinder head on an engine, are running 10 pounds of boost, and change out that head for a cnc-ported one with bigger valves, the boost number is likely to fall, because the restriction is gone (to a degree.)

So, on a Stocker, replacing the breathing systems (cam, headers, etc) with better-breathing parts won't necessarily result in an increased boost figure. In fact, I believe just the opposite would be true.

Someone correct me if I am wrong about that. Neil?

I KNOW that turbo cars are very difficult to dial. I don't know what the answer is to that, but it seems to me that aside from that, the qualifying problem needs to be addressed.

Too many conventional (normally-aspirated) race cars that have had myriad hours spent on R & D, with years of meticulous preparation, being shuffled into 2nd place in qualifying, by a turbo car that is boosted (in all probability) beyonf factory specs.

It's not that hard to fix...

Hope this answers some of your questions, Jim... I realize that at least 90 percent of what I said is not "news" to 90 percent of the people reading this, but you asked...

Just my usual cent-and-a-half....