STL engine builds?

[Knestis]

On the FWD IT Process issue...

1. Comparing production-based cars, FWD is dynamically a disadvantage on the race track - that's established physics and engineering (applied math and physics), not opinion.

2. The influence of that factor varies with other factors - some that the Process can't control for (and don't TRY, like weather), and one important one that it does consider (power).

3. Given the above, it was desirable to come up with a way to take FWD/RWD into consideration.

4. As has been demonstrated here to good effect, any guesstimates from the crowd are going to be disputed by someone else, so an external, unbiased, math expert was called in - Bosch Motorsport Engineering and their LapSim software.

5. LapSim was not used as part of the Process (as has been incorrectly stated around here). It was used to establish cut points for the IT classes, using estimates of the upper and lower HP limits likely in each, to arrive at the percentage deducts codified by the ITAC.

6. We knew that, like every other aspect of the Process, it was NOT perfect but it met alll of the policy requirements in play.

Talk about weather, "real race cars," and all the rest just muddies the water.

K

[Knestis]

On "rewards weight"...

"Pro" (read, made-for-TV-spectacle) racing uses that approach because they value spectators over drivers. Club racing HAS neither spectators nor an obligation to encourage the TV idiocracy to tune in.

Racing is about giving every driver the same OPPORTUNITY to be competitive. Rules control the input variables - the size of tire, for example. If everyone is working to the same rules, everyone has the same opportunity. The challenge that is "racing" is therefore building a system that maximizes its outputs (ultimately, speed around a road course) by managing all of the variables that are within the control of the driver/entrant/crew.

The minimum weight of the ITB MkIII Golf went UP this year, and I went faster at the ARRC.

How in the WORLD could that have happened...???

K

[JeffYoung]

Despite how some of my posts might be read (or even state) I tend to agree that FWD is in a technical sense (all else being equal) a disadvantage to RWD in most situations.

The problem is, was and will be quantification.

We can't say that Bosch Motorsports Engineering and Lapsim was "unbiased" and a "math expert" because we have absolutely no idea how they calculated the FWD deficiency. None.

And it absolutely was used as part of the Process. It was used to justify the "guesses" we made on what percentage deduct we should use for R, S and A.

Each of the 'subjective' adders and deducts are problematic to me. That applies to the ones that would affect my car negatively -- the torque adder -- and those that would help, like the live rear axle deduct, or the brake deduct.

Again, this is all water under the bridge. I'm not advocating we do away with this adder. It's been in use for too long and it's clearly not overly disruptive. But I do think the whole story on how it came into being needs to be trotted out as an example of what not to do for "objective" car weighting.

4. As has been demonstrated here to good effect, any guesstimates from the crowd are going to be disputed by someone else, so an external, unbiased, math expert was called in - Bosch Motorsport Engineering and their LapSim software.

5. LapSim was not used as part of the Process (as has been incorrectly stated around here). It was used to establish cut points for the IT classes, using estimates of the upper and lower HP limits likely in each, to arrive at the percentage deducts codified by the ITAC.

[JeffYoung]

Because FWD is moar bettah....

On "rewards weight"...

"Pro" (read, made-for-TV-spectacle) racing uses that approach because they value spectators over drivers. Club racing HAS neither spectators nor an obligation to encourage the TV idiocracy to tune in.

Racing is about giving every driver the same OPPORTUNITY to be competitive. Rules control the input variables - the size of tire, for example. If everyone is working to the same rules, everyone has the same opportunity. The challenge that is "racing" is therefore building a system that maximizes its outputs (ultimately, speed around a road course) by managing all of the variables that are within the control of the driver/entrant/crew.

The minimum weight of the ITB MkIII Golf went UP this year, and I went faster at the ARRC.

How in the WORLD could that have happened...???

K

[Andy Bettencourt]

But I do think the whole story on how it came into being needs to be trotted out as an example of what not to do for "objective" car weighting.

And there we will disagree. 1st we guess. Then we use a software program, designed to do exactly what we are trying to do, to validate our guess.

I don't care that I am not a software engineer and I don't know the code. It's supporting data to a guess. BETTER IMHO than just a guess.

[Chip42]

So, if Randy Pobst is driving the 2350lb FWD car, what weight should the RWD car be for Bill Auberlin to run the same total time.

(credit Greg Amy for this little exercise )

how much hp/Tq? what's the tire size? I refuse to believe that there is a correct generic answer. is the RWD better? theroetically, yes (if the "equal" suspension design is complete crap, I think the FWD actually has the advantage). by how much? too many variables. It works in IT I think in large part becasue the cars are all so IMperfect. there's slighlty less imperfection in STL, and much less in STU. if I had to stick to a swag, I'd use ~4-5% for STL, roughly the same number used in ITS, just because it "seems" to be about right there for largely the same target engine output and chassis but with slightly more weight (so I went down a bit). but I'm not going to say I think it's absolutely right, or right enough for the series.

BUT - Auberlin wont catch Pobst in near equal machines over a race distance. bad example.

[Andy Bettencourt]

You people make my brain hurt. This is really simple here...
THIS IS NOT IT, THIS IS ST. No car is guaranteed to be competitive in the class. Warts and all.

If you want to make adjustments to your competitors to make your favorite car competitive, then you're looking at the wrong class. Stop trying to fudge the rules to make your Whatsit competitive and built a Thatsit instead because you know it will run up front.

Matt,

I am not sure, in the context of STL, you are correct. Reading Chris's post is proof.

'Build it, race it, prove it sucks and we will review it'. That ain't warts and all.

[Z3_GoCar]

One factor that's not being addressed is that it's assumed that all motors of the same displacement give the same power, now how much drivetrain drag is in a FWD vs RWD. It's pretty well understood that the typical transverse system will be 2% better at getting the motor hp to the wheels. So, if you're talking wheel hp that yes maybe 5%, but using motor hp that's narrowed to 3%. Then if the head and intake manifold's are better on the FWD car, if the suspension is multilink instead of struts and triailing arm and/or beam axle. You get a class built for one manufacturer and and a few motor/chassis combinations (ST-H).

[Andy Bettencourt]

One factor that's not being addressed is that it's assumed that all motors of the same displacement give the same power, now how much drivetrain drag is in a FWD vs RWD. It's pretty well understood that the typical transverse system will be 2% better at getting the motor hp to the wheels. So, if you're talking wheel hp that yes maybe 5%, but using motor hp that's narrowed to 3%. Then if the head and intake manifold's are better on the FWD car, if the suspension is multilink instead of struts and triailing arm and/or beam axle. You get a class built for one manufacturer and and a few motor/chassis combinations (ST-H).

So one thing that I would bet bottom dollar that the SIM didn't take into account, like James is saying, it the slight power advantage a FWD car has - especially within our process.

Using the 25%, a car with 140 stock hp should make 175 hp at the crank. That's approximately 143.5whp for a rwd car and 148.75whp for a FWD car.

5whp is at least 5.5 at the crank which in ITA is worth 80lbs.....discuss. LOL

[lateapex911]

how much hp/Tq? what's the tire size? I refuse to believe that there is a correct generic answer. is the RWD better? theroetically, yes (if the "equal" suspension design is complete crap, I think the FWD actually has the advantage). by how much? too many variables. It works in IT I think in large part becasue the cars are all so IMperfect. there's slighlty less imperfection in STL, and much less in STU. if I had to stick to a swag, I'd use ~4-5% for STL, roughly the same number used in ITS, just because it "seems" to be about right there for largely the same target engine output and chassis but with slightly more weight (so I went down a bit). but I'm not going to say I think it's absolutely right, or right enough for the series.

BUT - Auberlin wont catch Pobst in near equal machines over a race distance. bad example.

Ack!
I forgot to put that in! Power...duh!

OK, the engine makes, in race trim, 200 crank.

Obviously, RWD has another gear set at 90 degees.

And the 'race' is actually just a 30 mile run. Ignore ability to pass, etc. Assume Bot drives that are ideal for the respective car. Name them Jake and Chip. Or whatever!

C'mon guys, toss a number out there!

[Ron Earp]

Ack!
And the 'race' is actually just a 30 mile run. Ignore ability to pass, etc. Assume Bot drives that are ideal for the respective car. Name them Jake and Chip. Or whatever!

Okay, I'll play.

My thought experiment 30 mile run is long straights with some big/long sweepers. In that case the RWD car will need less weight due to the efficiency of the FWD drive train. I figure ITS cars, and 170 FWD hp and around 164 RWD. 6hp, so about 78 lbs less for RWD if I want somewhat similar lap times.

How'd I do?

[lateapex911]

Sigh.

LOL.
The Glen, 200 crank. STL.

[JeffYoung]

Not far off of Ron's example really. 200 crank is around 170ish wheel, if not a little low. The Glen seems to be a lot of long straights and fast sweepers.

Work of his example and explain why he is wrong.

Sigh.

LOL.
The Glen, 200 crank. STL.

[Ron Earp]

The Glen, 200 crank. STL.

Okay, WG. In that case the RWD car will need less weight due to the efficiency of the FWD drive train. I figure STL cars, and 170 FWD hp and around 164 RWD. 6hp, so about 78 lbs less for RWD if I want somewhat similar lap times.

How'd I do?

PS-remind me again how we got off talking about Honda Challenge, err, STL, and FWD modifiers? Why are RX7s allowed in STL again even though you can't build a wankel powered STL car? Oh, wait, to bolster numbers, I remember now.

[Chip42]

Ignore ability to pass, etc.

STL isn't track attack, it's W2W racing. you ignore passing and you might as well be driving slot cars. part of the reason RWD is "Better" is tire wear is more even and the driver has more line options for passing / blocking. FWD has advantages in passing sometimes just because the line works out more advantageously for them in some corner. match whp/wt in your scenario and I wouldn't call a favorite wihtout more chasis specifics. Given matched crank hp with the likelihood of lower whp numbers on the RWD and I'll agree with Ron - though I still think real world the front engined-RWD car will have a slight advantage.

get over ~200hp and the FWD capabiltiy will start to fall off quickly.

[Ron Earp]

I figure STL cars, and 170 FWD hp and around 164 RWD. 6hp, so about 78 lbs less for RWD if I want somewhat similar lap times.

Oh, and I'm ignoring how much of a FWD fanboi I am or how much I want my favorite FWD econbox to win in the class.

[Knestis]

Asking the question differently...

If VW built a rear-drive version of the ITB Golf III, with the same engine and gear ratios and equally crappy suspension all around; would I choose it over the FWD version? Yes.

If the same question were asked of an ITS-power-level car? Hell, yes.

K

[JeffYoung]

Of course. That is a an easy theoretical question to answer.

The problem is the real world ain't like that. We have 300 cars in the ITCS with all kinds of different suspension designs. Using a "one size fits all" deduct calculated from a program that no one can explain how it works is a huge mistake (in my opinion).

Too lat though. Too many cars classed with it, and its our baby, which is fine. I just hope other classes don't repeat the mistake (in my opinion).

Asking the question differently...

If VW built a rear-drive version of the ITB Golf III, with the same engine and gear ratios and equally crappy suspension all around; would I choose it over the FWD version? Yes.

If the same question were asked of an ITS-power-level car? Hell, yes.

K

[lateapex911]

STL isn't track attack, it's W2W racing. you ignore passing and you might as well be driving slot cars. part of the reason RWD is "Better" is tire wear is more even and the driver has more line options for passing / blocking. FWD has advantages in passing sometimes just because the line works out more advantageously for them in some corner. match whp/wt in your scenario and I wouldn't call a favorite wihtout more chasis specifics. Given matched crank hp with the likelihood of lower whp numbers on the RWD and I'll agree with Ron - though I still think real world the front engined-RWD car will have a slight advantage.

get over ~200hp and the FWD capabiltiy will start to fall off quickly.

Chip, I understand all that... I'm trying to get to a base answer, and then from THERE we can debates the little stuff.
Chassis specifics? FWD: all independent, double wishbone front, good geometry. Rear also works well at lowered heights with good geometry. RWD Double A arms all around, Assume 55/45 for FWD car and 50/50 for RWD car or close to those numbers.

Ron, I chose the Glen because there are some long corners and some tight ones as well. The toe of the boot is a pretty tight, long, uphill late apexer that exits onto an uphill straight. A the end of that, theres hard downhill braking into a moderate corner.
Would you answer differently for Mid Ohio?? (I'm trying to find a general 'middle ground", not a dyno run or an autocross)

[lateapex911]

Asking the question differently...

If VW built a rear-drive version of the ITB Golf III, with the same engine and gear ratios and equally crappy suspension all around; would I choose it over the FWD version? Yes.

If the same question were asked of an ITS-power-level car? Hell, yes.

K

OK, for the Golf, you're talking 120hp or so crank? And since you said "yes" how much weight would you add to the RWD car before you said, "hmmm, yea, that's a tough one to choose between, I just don't know which way I'd go"?

And at ITS power levels, "Hell yes" becomes ? weight? (we are at 2350 for the FWD car)