low torque and high torque motors

[Malcolm]

This could easily be another of those issues that is a cost thing. Give me a bigger budget and more will spent on the engine. In 11 years of competing my GTD my total engine budget has been about £10,000. Two engines and one rebuild. If I lived in the USA I am sure I could have saved money on those bills too!

In our little competitions here in the UK, the general rule of thumb that is emerging, is that you want lots of torque low down in the rev range as we need the grunt exiting low speed corners. When guys have have high revving big BHP monster engines, unless it is matched with low rev band torque (is that possible?) they don't blitz the field. I hope you are reading this JP! /ubbthreads/images/graemlins/smile.gif

But a cheaper route to winning is actually tyres. Slap on a set of sticky tyres and your times just tumble.

Cost wise if you want to get better times for less money, put your money into a second set of rims and sticky tyres. Then go back and do your engine later.

If you get the next GTD club mag, I beleive there is an article in there about Jackie Ickx knocking 4 secs off his Goodwood lap times by running a 2 inch wider rear tyre, all else remaining the same.

Interesting comments above about Cobra owners whacking in monster engine power and then crashing at the next corner. Doesn't help the US stereotype of not being able to get cars around corners, just kidding guys. /ubbthreads/images/graemlins/grin.gif /ubbthreads/images/graemlins/grin.gif But it is true. When I got my 40 it was a jump from never having driven anything regularly over 150 bhp to 350 bhp. I went off at Goodwood as a result so took lessons at Peter Gethins Driving School. If I took the lessons first I would have saved a lot of money! I would recommend any new owner taking lessons and building the cost into the build budget. It could well be cheaper in the long run.

Get used to your car's "lower" power before you go nuts with big power.

Malcolm

 

[James]

[ QUOTE ]
, unless it is matched with low rev band torque (is that possible?) they don't blitz the field. I hope you are reading this JP! /ubbthreads/images/graemlins/smile.gif

Malcolm

[/ QUOTE ]

Yep! 360 ft/lb at 3400RPM, 400 ft/lb at 4200RPM & 420 ft/lb at 4800RPM.

Its lovely flat torque curve with max power at 6600RPM, lots of money well spent.

I can't get tyres wider than 275 for the track! Road use 255!

Weight is also key! The MDA is a lightweight, so it should go reasonably well.

Regards,

J.P

 

[Malcolm]

Sorry JP, I was meaning at about 2000 rpm not 3400 rpm. This is the RPM you will be down to at a lot of corners on the hills. I thought your engine was more of a screamer. I thought you asked for it to go to 7500 rpm? Maybe Dave Milham did give you my engine after all! /ubbthreads/images/graemlins/grin.gif

Whilst here JP, can you let me have an email address for you as the one I had before is not responding. I've missed out on sending you stuff that I wanted to get to you. Cheers.

Malcolm

 

[Robert Logan]

Ross,

Good times, well done. Sorry I was not there but we move house in TWO weeks and I needed to earn some Frequent FAMILY Points. What position did you finish with.

Best wishes,

Robert

 

[Knighton]

[ QUOTE ]
Actually, Knighton made the typo in his original post. And being from Canada, where they wear toques (made famous by Bob & Doug McKenzie), we can forgive him /ubbthreads/images/graemlins/wink.gif

[ QUOTE ]
By the way why do Porsche owners hate being passed by a GT40 so much that they move over to block you on a very wide straight.

[/ QUOTE ]
I may end up ticking some people off (so what else is new?), but this seems typical of Porsche drivers. They just don't like to be passed period, whether by a GT40 or a Datsun 510 /ubbthreads/images/graemlins/shocked.gif I don't really understand their thinking, but I guess it has something to do with a feeling of entitlement, given how much they have paid for their cars or something /ubbthreads/images/graemlins/tongue.gif

[/ QUOTE ]


Doohhhhh! It has been rather cold here - down to -17C. I guess a toque was on my mind at the time - pardon the pun!

Start calling you Stevie Wonder - I wonder how Steve found out about toques? /ubbthreads/images/graemlins/grin.gif /ubbthreads/images/graemlins/grin.gif /ubbthreads/images/graemlins/grin.gif

 

[ QUOTE ]
... 2000 rpm not 3400 rpm. This is the RPM you will be down to at a lot of corners on the hills. ...

[/ QUOTE ]

I have no trouble downshifting and keeping my RPM at 3500 or more on any corner. Why would you ever go down to 2000?

 

[Paul Thompson 'Hooligan']

Hi Bart -

If you check the video page of the club web site. The last video, showing Andrew Fordyce at Longleat explains all.

Dodd's hairpin is a 180degree hairpin that I approach at about 100mph - I downshift to second on the approach and turn in. Speed gets down to about 20 Mph or so and revs are down but changing to 1st would be a waste of time as the tyres just light up when you get back on the gas, plus you would add 2 more shifts, 1 down + 1 up. Andrews cam comes back on song about 3750-4000rpm and is not slow but Roy's pulls strongly at even 2000-2500rpm (347ci) so we find it a little easier. The longer 2nd gear ratio of the Quaife converted Renault is also offset by using 25" dia slicks. A short blast leaves us crossing the finish again at about 100Mph.

Longleat is not unique, revs can get pretty low at several other venues eg Wiscombe (Sawbench / Martini), so having an engine that has plenty of low down torque helps. /ubbthreads/images/graemlins/grin.gif

 

[Gary Gibbs]

Don't know know if any of you have seen the latest Car and Driver with the big shoot out between the Ferrari 360 challege car, the Porsche GT2, and the Ford GT. The GT clearly has them covered by 2 seconds per lap on a 1 min 30 sec course. The authors comment on how the high torque down low lets them accel off the corner well. This car is about 3400 lbs though. Based on the 0 - 60 MPH of 3.3 sec and the 1/4 mile of 11.8 at 128 it is making about 500 HP and 500 ft-lbs at the wheels. This jives with the comment I heard one of their engineers make at Monterey (yea 500 HP measured somewhere) Now I think they meant at the wheels. The Car and Driver article does not complain about too much torque at all they love it.

 

[Kevin M]

Gary,

Have you got your car running yet? I haven’t seen any new pictures on your site.

If any car is going to test the “Big Rear Tires & Lots of Torque” approach, yours is it.

If you find it comes off corners well without wanting to swap ends, that should answer that question once and for all.

Kevin

 

[Knighton]

kmcgowen, I agree.

Is it safe to say that really sticky 335 rubber out back is paramount with a high toque - gottcha Steve /ubbthreads/images/graemlins/grin.gif - torque motor?

Ok, what part does traction control (boo, hiss) have then?

 

[Kevin M]

Knighton,

The limit on any of these cars is always traction. That’s why most of my answer to your question about motors was a discussion of tires.

To put this in perspective, the Bentleys that won LeMans this year (and the Audi R8s) make 550 hp and weigh about 2,000 lbs dry. Since they carry a lot more weight of fuel than a street GT40 we can call them 2,100 lbs equivalent weight.

When you look at these numbers and realize that an iron block GT40 weighs about 2,300 lbs. And an aluminum block engine can get the weight under 2,200 lbs. You can see that we are talking about “street” cars that have same power and weight as the top endurance racers in the world.

If you read Paul Frere’s article about driving the Audi R8 in the October 2003 issue of Road & Track, he mentions that the Audi will spin the tires in second gear with full on racing tires mounted on 14.5” wide wheels. (Also, the Audi makes a great deal of downforce, which helps its traction situation. Something the GT40 can’t match)

No one is his right mind would suggest that the Bentleys or Audis could possibly run 255mm street tires (on a 9” wheel) and be controllable. The problem comes when we don’t stop and realize that with a good 393 to 427 Windsor stroker motor we are building a car that is fully equivalent from a power to weight standpoint.

If you approach the subject from this perspective, it changes your ideas of what to expect will be necessary to make the car workable.

As for traction control, I think it would be a reasonable safety net on a car like this for street driving, but you can’t just grab an existing system from another car and stick it on. The systems are all designed and tuned for the specific car they are on and it would take a huge amount of work (and access to the manufacturers programming code) to make it work.

Kevin

 

[Knighton]

Kevin,

I am under the impression that traction control, workable through an EFI system like Motec, is not really an issue but rather fairly straight forward. No?

I would like to read that article on the Bentley. I do think 600+hp & 600+ lbs-ft is really heaps of motor (for me) in a 2,300lb car. Our heavily speed governed roads here in North America would make this amount of power seem like a waste, not being able to use it often. I lived in Belgium and travelled through Europe quite a bit and know that the above power output would not go to waste. Some guys just want this amount of power and I have no issues or problems with this at all. In fact, I think it is great!

I recall driving my grandparent's 65 Ford Galaxy with its 390 and did really enjoy the torque output of that motor. There were no corners with that car, only straightline acceleration so traction and tires weren't an issue.

I agree that tires and traction on the 40 are a concern and your post was excellent addressing this. The new GT does have traction control and an EFI like Motec can also see the replicas with it as well.

Would traction control then be a torque equalizer meaning X amount of traction is available for X amount of torque?

For example: If 350 lbs-ft of torque is enough to spin the tires on corner exit, wouldn't 600lbs-ft motor be traction controlled via EFI traction control, to exert only 350lbs-ft? I would say yes.. no? The other 250 lbs-ft then is not needed or rather is limited by the traction control. This is not to say the other 250 lbs-ft is a waste as it would certainly be used and felt in the higher gears.

Better to have it and not need it than need it and not have it.

 

[Kevin M]

Knighton,

When you asked about traction control, I thought you were referring to a system like Porsche uses that can help to control the car by selective braking, etc. If what you want is just an acceleration control for straight lines then the MoTeC system will do that.

The thing is, for traction control to be really effective there are some other issues.

First, it has to have something to compare to, to know when it needs to become active. The simplest way to do this is to compare the rotational speed of the front wheels to the rear wheels. (This is easy to implement on a car with ABS brakes because all of the necessary sensors are already in place along with the programming to make sense of their output).

The problem area is defining an acceptable level of slip. Good acceleration requires that the rear tires turn a small amount faster than the fronts and generate some slip. If you don’t do this you get the systems that the magazines are always complaining about where the system cuts in at a very low level and doesn’t allow the car to come anywhere near its potential.

On the other hand, when the car is cornering, too much slip can let the tail start to rotate pretty badly. This is why the good systems, like the one Porsche uses, are very complicated and use massive amounts of computer code to vary the response of the system based on speed, acceleration, cornering forces, and inputs of speed differentials from all four wheels, which allow the computer to tell if the car is beginning to spin even before most drivers would be aware of it.

Taking this one step further, a really good (Professional) driver uses the ability to apply power to shift the weight to the rear and stop a spin when it starts. A traction control system prevents him doing this and could actually cause him to lose the car where he might have otherwise been able to save it. For this reason most racing drivers don’t have much use for traction control.

In the end, the real limitation in the equation is the driver. Most of us simply are not competent to handle a very powerful racecar at its limits. We can learn, but it would take at least several months of driving the car on the track on a regular basis.

I hate to quote Clint Eastwood, but a man has to know his limitations. We all love powerful cars or we would never be drawn to something like this to begin with. It is fine to have a car that is beyond your capabilities as a driver, as long as you know that it is beyond your capabilities and you only drive it to your limits.

Kevin

 

[Gary Gibbs]

I had heard that the Ford GT does not have traction control. Has this changed? Anyone seen it in print one way or the other?

 

[Jim Glickenhaus]

It doesn't.

 

[40 Bud]

Kevin, that is one of the best insights I have seen expressed. I have a 289 enlarged to about 305 and all of the goodies inside that give it some extra power - about 330/340HP. It is very streetable and can go very fast on the track. With Dick Smith driving and using 6500 as a red line I was treated to some fun times at Willow Springs. I will never come close to his lap times so would all of the extra goodies do any good? Not really. Well maybe for bar talk or bench racing. I have upgraded the brakes and use Hoosier TD's on the track and find that the car is suited to my talents. Another 50HP would be ok and would not upset the street worthiness but I don't think I would want more than that.

 

[Kevin M]

40bud,

We all go for horsepower because it’s easy to do. I am certainly as guilty of that as anyone. I look at the fact that I can build a 408 that uses basically the same parts as a 306 and only costs a couple of hundred dollars more, and it is very hard not to go ahead and do it.

The simple fact though, is that on most race courses, beyond a certain point, more power only improves you lap times by a little bit. The largest improvements are had from making the car lighter and improving traction (Larger or stickier tires, better balanced suspension, etc.)

Malcolm mentioned in his post the article where Jackie Ickx dropped 4 seconds just from going to 2” larger rear tires. It would take a huge increase in power to get that much of a drop.

Even the creation of the Mk2 cars with the big block engines was an unusual case, because the GT40s only reason for existing was to win LeMans.

LeMans was (and to a lesser extent still is) a very unusual racetrack. It has the Mulsaine straight which back then was miles long. To win at LeMans required a car with a very high top speed. LeMans is one of the few tracks where a car with lots of horsepower and lots of weight could beat a lighter but less powerful car.

They actually built a Mk2 variation for Can-Am. It was run by McLaren and called the X-1. It was uncompetitive because of its weight on the more normal tracks that Can-Am ran on.

Kevin

 

[Gary Gibbs]

Making the car lighter and using stickier tires can be done with either motor combo. I once heard that Mark Donohue said that "if the tires are not spinning at the end of the straight you don't have enough power." If that is an actual quote and the benchmark then only John Force has enough /ubbthreads/images/graemlins/smile.gif.

Looking at the performance of the new Ford GT I would guess that a typical GT40 replica would get its butt kicked on the track by a 1000 lb heavier car (the new GT). Obviously that does not mean that everyone should have such a car, etc.

 

[Kevin M]

Gary,

I agree. That’s what I meant about the motors. You can build a 427 like yours, making over 600 horsepower, and it will only weigh about 40 pounds more than a mild 306 that only makes 350 to 400 horsepower.

When you look at that, it is hard not to go with the big engine. And, as long as you use a strong transaxle and large sticky tires, like you are doing, it should work fine.

The only question would be if it is going to be a street only car. Some years ago I was talking with someone who used to race the Can-Am cars. He told me that he couldn’t use full throttle below 100 miles per hour without spinning. That’s fine on a racetrack, but it would be a little much on a street car that will almost never run above 100 mph.

There is simply no right or wrong answer here. None of these cars really make any sense for “transportation” purposes, that’s not why we build them. In the end it’s just a matter of figuring out what’s right for you.

As for the Ford GT. Your car would certainly be faster around a racetrack once you’ve had time to dial the suspension in properly. You would be making similar power (They are apparently getting about 500 at the rear wheels) but your 2,300 lb weight would be unbeatable by a 3,300 lb car. You should be able to corner much faster as well as out accelerate it.

I look forward to seeing some pictures of your car when you have it running.

Kevin

 

[Howard Jones]

I just spent a few mins reviewing this thread and I have concluded that what I learned racing motorcycles 30 years ago is still true. On a roadrace course the guy with the best set of tires will win. Now I except the fact that a 65Hp spitfire with all the grip in the world will have a hard time staying in front of a 500Hp GT40 but in a case with most of the parameters of two cars nearly the same, weight within 400 lbs or so and Hp not more than 150 hp different the guy with the sticky NEW race tires will win every time. Brakes might be the only exception to this rule but this thread has not gotten around to brakes so I'll assume both cars in my example have similar braking performance. By the way this is a very important aspect of tire performance, braking.

Back in the day I rode a TZ350 Yamaha that belonged to a friend that also ran desert endurance races with me so he let me run his road race bike a few times one summer. The problem was tire buget. I got used tires from the guys that had enough money to run only new tires. I can tell you that it is not possible to pass a guy that is on new tires when your's have 20 min on them already and have been heatcycled more than once. It turns out to be a race with the other cheepskates for best of the rest.

I have always believed that the best performance increase, as measured in lap times, per dollar spent is tires. Always has been, always will be. So save the last few hundred for some nice new sticky slicks and you will be FLYING past those 700HP Cobras into and around the corners. On exit you will have it wide open long before the big snakes and they will damn near kill themselfs trying to catch you. YAAAAA!!! 40's rule!