Lolas, Enduro, BSFC, 25 gallons, and can we win?

[Ron Earp]

We want to win the 13 Hour enduro. Not just in class, but overall. This year, in 2006, a ITS 2nd Generation RX7 came home with the win. Now, the car was well prepped and well driven, but a car like that works hard to turn 2:15 laptimes. A Daytona Coupe from 2005, that didn't finish due to failure in hour one, ran some 2:01s - over 15 seconds a lap faster, on average, than the next closest car that year.

I think a Lola Spider could run at least 2:01s and faster. It'll weigh less, and, we'll get some good handling out of it. The problem is going to be how much power to put in the car and balancing that with lap times and fuel stops.

Fuel stops are a killer. They average around 2:30 to 3:00 mins, and are mandated, I think, at a minimum of 1:30 mins. You can throw away all your hard earned progress with a fuel stop. Maximum amount of fuel you can carry is 25 gallons, so you can forget lugging 50 gallons out and staying out for four hours.

In the case of the Daytona Coupe that ran 2:00s in 2005 it needed to pit for fuel every 30 minutes I am told. So, every 30 minutes it uses around 3:00 to 5:00 minutes (taking on 25 gallons takes longer than taking on 10 gallons in the Miata) in the pits. A Miata can run for a good 1 hour 30 minutes before refueling, therefore, compared to a Miata the Daytona Coupe gives up six minutes of time every time the Miata pits.

Now, a Miata can comfortably run 2:25 all day long for one and a half hours. Basically every six laps the Coupe will lap the Miata, but, every twelve laps the Coupe had to pit to take on fuel - and when the car is fueled the driver must get out.

The advantage, or appeal, of running a car like the Coupe is diminished with the fuel stops - there are too many of them. I think the car was running a 408 Windsor thus had a lot of power, but, also consumed a lot of fuel.

If one assumes that the BSFC of a motor we might use for the enduro is 0.50 pounds of fuel per horsepower hour, and we have 25 gallons or 165 lbs of fuel, then we can calculate a rough idea of endurance based on engine horsepower.

Doesn't look too good, does it? More later......

 

[Andy Besic]

Should you be looking more at TQ for endurance? HP is Tq vs RPM right? A 350ci v8 making 300hp at 3000rpm will use less fuel than 300hp at 6500rpm won't it? Think truck motor for endurance. Small intake/carb, small exhaust, low rpm, lots of TQ. Audi R10 has proven this. The trick is making torque at low rpm with light weight. That is one of the reasons the 427 gt40's evolved. More tq needs less gears and causes less wear.

IMHO build a balanced 350 with a flat tq curve between 2000rpm and 4000rpm and put in a 930 4 speed transaxle with a bonneville salt flats final gear, get used to shifting around 4000rpm and concentrate on preserving momentum during the race. You should concentrate on average lap times (total time of race/number of laps completed) to design and tune the car.
You may find that driving the car 8/10 will ultimately be faster than driving it 10/10.

 

[Ron Earp]

Well, there is no magic way around the BSFC issue. HP = (Torque * RPM) / 5252, therefore, if you wish to have say 300 ft/lbs at 3000 RPM, between the 2000 RPM and 4000 RPM you mention, then it'll require 171hp. And, a motor with that sort of power is going to have an endurance of around 2 hours at a BSFC of 0.5.

The BSFC of the motor we run is a big player here. For gasoline engines it runs around 0.40 to 0.60. If we can get it down to 0.40 for our engine then things improve. For example, a 200hp motor at 0.5 BSFC has about 1.65 hours of endurance, while the same motor at 0.4 BSFC has an endurance of slightly over 2 hours......(Auto engineers feel free to jump in and correct this mess). I have no idea what our particular engine will have for a BSFC, and I'm sure the BSFC will vary depending on what RPM range the engine operates in too.

Diesels have a BSFC of around 0.28 to 0.38 or so, and if we had one of those with around 200hp and figured a BSFC of about 0.33, then we'd have 2.5 hours - that'd be fantastic.....hmmmm..........a Passat Diesel engine has a N-S orientation, can be had with a six speed, and can make the required amount of power.......

 

[Fran Hall RCR]

Strangely enough I have been talking with Joe T , RCR rep in the UK about a diesel powered RCR-P......hhhmmmm

 

[Ron Earp]

VW group have a V6 turbo diesel in Europe that I have driven in Germany a few times in Passat wagons which our company uses as "fleet" cars. I want to say it is rated stock at 175hp basically and about 250 ft/lbs of torque, and has a very nice 6 speed. I've driven at like 120mph on the A8 there for a good bit of time, nice motor. This might be the ticket.....

R

 

[Russ Noble]

Diesel could work but in a T70? What sacrilige!

However I am the first to note that a race car is always a work in progress to obtain the most benefit under the current rules. So go for it Ron! Good luck. Just as well it's not an original, all the purists would hate you!!! They probably will anyway.

Whether running petrol or diesel is it possible to change the fuel rig/fillers so that you can get your 25 gallons aboard in the mandated minimum 1:30 time frame? That should help quite a bit.

Cheers

 

[Ron Earp]

Hi Russ,

I don't think we'll be using a diesel, but it is nice to think about.

We'll be using my SB Ford, which is "period correct" so the purists won't have a reason to not support the racing effort! However, I think a really neat motor for it would be a 260/289, with small port heads, small 4bbl, and around 200 or so hp and built for extreme y reliable operation.

As far as fueling you can rig about anything you want to fuel the car so a NASCAR dry break deal would be legal for SPO class in SCCA.

 

[Ian Anderson]

Ron

There was an article when Skoda released a new car over here that standard torque was more than the Porsche offering - and theirs came from a 2000cc 4 pot turbo diesel

Something like 200hp and 350nm torque from about 2000 rpm

http://www.carpages.co.uk/skoda/skoda-octavia-19-08-06.asp is one write up. More importantly it is fly by wire and chippable for about £500 to increase both numbers by 35%

Ian

 

[Malcolm]

Sorry, BSFC stands for???

FWIW the Porsche GT2 I drove in this years Silverstone 24 Hours was rated at approximately 345 bhp and 350 ft lbs of torque. It was fuel injected. We revved to 7400 rpm. Our fuel capacity was 120 litres. We tested fuel consumption during the few stints we got prior to the engine dying. We would have been able to do 2 hour stints as we used roughly 45 litres per hour which left a healthy safety margin for pace car periods screwing up calculations during a stint.

Maybe of help?

 

[Fran Hall RCR]

Brake Specif Fuel Consumption

 

[Ron Earp]

120L is 31.5 gallons. 31.5 gallons is 208lbs of fuel. Plugging 350hp into the equation with a BSFC of 0.4 lbs/hp*hr yields 1.5 hours of endurance.

So, it appears in your case the equation is way conservative. And I sort of figured this rule of thumb thing would be off because the BSFC is per hour of solid running, it does not take into account anything else so it would be a worst case scenerio.

In your case it is off by around 30% or so under real-life conditions.

If we can assume that for a moment then a 250hp motor will give us at least 2 hours of running minimum at 0.4 BSFC, and maybe as much as 2.7 hours of running - that would be more than enough. I think if we could get driving stints right at 2.25 hours then we'd only need probably five stops (accounting for yellows, pit time) to finish the race. And I bet we'd be first with such a car.........

 

[Malcolm]

If you went over teh 2 hour stint, then with the light car adn keeping out of trouble when teh sun goes down, yeah I see you in first place. Got a spare seat?

 

[Ron Earp]

Whoa now, we might be getting ahead of ourselves now - we don't have a running car yet....but I think five drivers, each pulling 2.25 hours would get the job done. If a well-driven BMW 325 can run 2:14 flat out, then I would think a Lola could run 2:05-2:10 without breaking much sweat, and faster at 10/10s. And if we could run 2:10 or so, driven comfortably and safely, then we'd be in business.

But I've had a few people wanting to help out on the project and Fran has some ideas too.

 

[Gary Gibbs]

Can you use a higher speed refueling rig?

 

[Ron Earp]

We can use any rig we like really since we'd be in special production.

But, fuel isn't a complete killer. Spec Miatas MUST use the stock filler neck. We cut the flap out, of course, but even so that neck and 5 gallon fuel jugs can be used to fill a SM in 40 seconds or so. Just checking the car over takes about that long, so as long as we can get the fuel in the car in under a minute I think we'd be okay.

NASCAR dump cans would be legal to run if we sorted it out.

 

[Darnel A.]

I would be concerned with fuel economy. I would use port fuel injection. That cool backfire sound and flame out of the exhaust on old carburated race cars was excess gasoline being ignited in the hot exhaust whenever the throttle is closed..

 

[Malcolm]

Whoa now, we might be getting ahead of ourselves now - we don't have a running car yet....but I think five drivers, each pulling 2.25 hours would get the job done.

Fear not, I was just pulling your leg!

Going back to my comments on the fueling, it seemed typical practice here to say 1 litre per minute as a starting point and then to actually test the car in a pre event run.

I would think the bhp/torque design for the engine should be more reliability based than fuel consumption based. As they say, to finish first, first you got to finish. To make a car reliable yes drop bhp/rpm but surely a well built V8 can do say 6000 rpm all day and night? Maybe at 300bhp? Going down to 200 to 250 seems too conservative to me.

 

[J. Salmon]

If you did use a diesel and you won, you'd make a bit of "noise" too. It's one thing when Audi builds a diesel specifically to win, but a privateer doing it? Heck, Audi might even cut you a deal on a motor...

Plus, you could always pull the motor and drop in a SBF later - and then the chassis would have a great racing history!

I rode along with a guy who was turning sub 2:10's in a T1 Corvette. I was sitting there thinking how physically demanding it would be to run an endurance race at that pace. Sub 2:05's - you'd better get one of those neck resistance machines that the F1 boys train with.

 

[Jac Mac]

Ron,
Been thinking about your refueling problem time wise, are you allowed two refuelers over the wall at once?, if so two guys with a 13 gal swirl type dry break refueler each side could cut the refuel time just about in half.

Regardless of your 5/8" bolt in the alternator you will still need a stay from it to the water pump or it will eventually fail at the thread where it enters the cyl head.

Have you gone for a stroll thru a local pick-a-part yard to check out the water pump pulley situation, stick with the Ford pulleys, they have a double thickness in the bolt area, unlike those failure prone GM example's.

Jac Mac

 

[Ron Earp]

2:10s in a T1 is humping pretty good and a lot of work as T1 is almost bone stock all around - seats included. My first instructor raced a Vette in touring and I also scored a ride for about 20mins like that - I was thrown all over the touring car, compared to a race car, and it was physically abusive almost. I think we'll have a big advantage with higher straight speeds, higher acceleration, and much better cornering speeds compared to T cars. There were a couple of touring cars (T2, T3) racing the enduro with us this time and they park in the twisties compared to all the full on race cars out and about.

5/8" and stay - got you, I understand now. And, I can make a stay from the bolt over to the water pump bolt. Refueling can happen in a variety of ways and the main thing is one man for gas and one on the fire extingusher. Not sure about a pair of men though, must check the rules on that one.