RT-41 vs. DB-4 discussion for fun

[RussMcB]

If you were to make a list of reasons why an RT-41 is faster than a Swift DB-4, ranked by "biggect improvement in lap time", what would it look like?

Feel free to hijack this thread and let it go wherever.

[Charles Warner]

Russ,

Off the top of my head probably aero and chassis stiffness.

[RussMcB]

I'm sure that's true. However, I was looking at pictures of a DB-4 and it looked pretty swoopy. My imagination sees it going through the air pretty smoothly, and the tunnels look good (to my untrained eye). Of course, my viewpoint is from an early 1980's Ralt owner.

If I make an assumption that the same driver could go 1-2 seconds per lap faster in the RT-41 around Mid-Ohio compared to the DB-4, and you overlayed the performance of each, where would the RT-41 be faster? Everywhere, a tiny bit? Or does it do some things much better (high speed corners, straights, braking)?

The wheels sizes are different, right? Or is that the 008a's and/or the 014's? Does that mean they have much bigger and better brakes?

Just curious about the differences. Wondering how much performance benefit there is for the more expensive RT-41. In case I suddenly triple my salary I need to start planning my next move.

[Charles Warner]

Russ,

I think you'll find it is a platform difference rather than a specific increase over a specific regime. IIRC, the chassis stiffness of the RT-40 was at least an order of magnitude of 2-3 above the RT-4/DB-4. Then, the RT-41 was another 50% stiffer than the RT-40. We are talking in the range of 12,500 pounds per degree of chassis flex on the alloy tub/S-glass cars to over 45,000 pounds per degree of flex on the RT-41. (The numbers may be a bit off due to memory lapse, but the ratios are pretty accurate.)

Also we are talking about the benefits of learning better designs and suspensions. Technology creep can be a wonderful, if expensive, thingie.

The wheels for the RT-41 are the same - 13". I believe the Swifts ran the 15" wheels. Bernie Sunier was one of the most successful DB-4 drivers in the country. I believe he was in the top 5 at the RunOffs not too long ago. He has upgraded to a 008 and was quicker and enjoyed the car much more. It would be great to see him in an RT-41 to get a real comparison.

As far as looking swoopy, I think the current crop of F1 cars look aerodynamically challenged. However, they are all driven by wind tunnel data. So much for my visual perspective.

[JByers]

Charles,
The DB4 was built in aluminum and carbon, your chassis flex figures are refering to which construction?

[Charles Warner]

The earlier cars were aluminum and S-glass. The later cars used carbon for the upper sections. I would think these numbers would change a bit with the later cars but not by much. I do not have any hard numbers on those. I am sure they come no where near the numbers of even the RT-40, let alone the RT-41. I have no numbers on the Swift 008/014.

[Paddy O'Brien]

I would be interested in hearing the comments of someone who has driven a Ralt 40/41 and a similar set up Swift DB4. I have been running a DB4 since 1996 and have been thinking of upgrading to a Ralt or Swift014 mostly because my tub has been de-lamanating worse the last couple of years and shock and bar changes do less and less. I tried a pro spec Swift 014 last year and really wasn't that impressed with the "improvement". The newer Swift felt better behaved but wasn't as toss-able as my short wheelbase DB4. Perhaps due to the Yok radials it also required a totally different driving style compared to the DB4. But my DB4 is 1990 stock setup with two-way fox shocks, so how much improvement is in newer shocks and stiffer tub? I have noticed that the Ralts put the power down much better than my car(ex.turn 5 at Elkart) and seem to have better high speed aero grip(T1 at Mid o, Carrosel at RA). So, I went the "cheap" route and decided to keep the DB4 and am installing a new tub and 4 way ohlins and the trick salsbury diff so we shall see... Besides,I think the Swift DB4 is one of the prettiest racecars ever.

[Charles Warner]

One issue of the 008/014 versus the others is brakes. Remember, with 15" wheels (bigger discs) the braking of the Swifts is quite a bit better than even the RT-41. That said, in speaking with someone who has driven both, the Swift is probably as fast as the 41 but has a much narrower window. In fact, that window is sooooo narrow that you better be perfectly in it ALL the time. The 41 is much more like the older Swifts (much wider window) in the fact that you can work the car. The comment was made that, in the 008, you had little, if any, chance to correct an error. When you realized you had overstepped your boundaries it was merely noting something that had happened in the past. The 008 is easier to work on. There seem to be little differences in aero.

Look at the Moroso results. Brian French (RT-41) was a full second faster than Cobb (014). Both men have escellently prepared cars and are both top drivers. Much of this could be down to track.

[RobLav]

This is a great discussion. When I looked at a DB4 for possible purchase, I loved the car, and I fit in it very well. But one of the first things I noticed was that the front track was too narrow, and wondered how much of an improvement a 3"-4" increase would provide (a 3"-4" increase in wheelbase might be nice too). The other issue I wondered about was flex between the engine and tub. I'd love to find a decent DB4 roller to experiment with, one that the tub has not de-laminated.

[Charles Warner]

I am currious to know why you feel the front track on a DB-4 is too narrow.

[RobLav]

Charles,

Two reasons - Aero and stability.

Aero - when I looked closely at the DB4, it looked like the air coming from the underside of the front wings near the front tires was going to interfere with the air coming around the front tires creating turbulence. Either improve the front wing to help air flow around the tire or move the track outward and keep the maximum width wing.

Stability - increasing front track can help with putting the power down out of corners. You will not have to dial in so much anti-roll and can reduce the reliance on the limited slip. The chassis will need to be as stiff as one can make it to take full advantage of this, which I then eyeball the engine / tub connection. From here, I'd then explore softening the rear spring rates and rear anti-roll. Oh, and I forgot to mention improved stability in trail braking.

My concern was that the inboard legs of the front upper suspension arms are too close together, which may warrant a somewhat heavier aero tubing. The lower front inboard suspension arm legs seemed far enough apart.

[Charles Warner]

Rob,

I understand the concepts. I am just wondering about a couple of things. First of all, would this mod not have been tried by the many pro teams over the last 15 years or so? Or even the factory? In my memory I seem to think the front track, as is, is approximately the same as the rear track, no? Ralt found that the best configuration (RT-4/RT-5 here) was a wide track front and narrow track rear - IOW, about the same track on the front. I seem to remember that going any wider was pretty much an aero disaster as the hole you are punching in the air becomes somewhat unmanageable and the airflow off the front tires has a hard time attaching itself to the side pods.

As for the wings, Marc Bahner developed a profile years ago that has proven to be very successful on the DB-4.

I would also consider the extra loads placed on suspension pick up points, etc.

[Paddy O'Brien]

I am not an engineer and am afraid of tools but as a DB4 owner I have talked to the people who built and ran these cars "back in the day" and here is the consenus: David Bruns was a brilliant designer and the DB4 was way ahead of its time but the simple fact is that it is now 20 years old. Serious development of the DB4 stopped about 1993 as the slightly better RT40/41 came along. Several mods were tried on the DB4 but everyone always goes back to more or less the factory stock settings because thats how Bruns designed it. Guys who measured chassis twist saw flexing at the cockpit opening which led to same teams bonding in extra carbon supports across the top which is supposed to have nearly doubled tortional rigidity(just did that on my tub). Also some of the tube brackets on the rear suspension mounting points were replaced with solid aluminum blocks. Yes, compared to newer designs the suspension pickup placement is too narrow and Bruns tried to make the front bulkhead do to much work which leads to flexing there, and so the car always goes to understeer. However,far and away the best method to make a DB4 go faster is to make the existing design work as it is supposed to. The problem is that because they are selling so cheap in the used car market that only us budget racers are running them with thier budget motors, budget shocks,budget tires,etc. With a good motor, current shocks,proper diff and fairly stock setup, Dave Wilcox "won" the first practice at the runoffs in his DB4. At current market values, the Swift DB4 has to be the best bang for buck out there.

[Dennis Tapp]

Paddy, What part of your DB-4 tub was de-lamanating? Can you see it or is it the way the car handles? I have a 91 DB-4 and I would like to know what to look for. Thnks, Dennis Tapp

[Paul LeCain]

I've run both over the last few years. We finished second at the Runoffs in 1996 against mostly RT-40s and RT-41s with a DB-4. Qualified 2nd another year (1998).

I have the lap data for every lap we've done in both cars. From it, I can see a couple things.
With current SCCA rules regarding skirt height, I'm sure our DB-4 had more downforce than does our RT-41. 2 centimeters of skirt is a ton. Because of the underwing downforce, we ran much smaller wings on the DB-4 than on the RT-41 = better top speed with the same power.

That said, the RT-41 puts the power down better out of corners. It is better in long sweeping corners, too.

We had a good DB-4 (ex Stuart Moore). He had added a good deal of stiffness to the front end (inside, tying the mounting plates together). The floor did delaminate, but we fixed that by removing it (seemed like a million rivets), having a new, slightly thicker floor made of aluminum, then re-gluing and re-riveting the inner floor, honeycomb and new outer floor with aerospace epoxy.

We raced against a lot of RT-40s and RT-41s and won over 90% of our races in the DB-4.

For a club racer with a limited budget, the DB-4 is usually a better alternative, I think. They're dirt cheap. The race-to-race maintenance load is less. The setup envelope is wider.

Just my thoughts.

[Paddy O'Brien]

Dennis, A quick way to check for DB4 delamination is to take a quarter and ping (or in your case tapp!) the front and top of the tub and then along the lower sides. You should only hear a nice solid sound,if you hear a hollow sound, you have a problem. Unfortunately,visual inspection tells nothing as my old tub was badly de-laminated yet looked brand new. Lots of things can start the de-lam process. I was told that when these cars first came out that some mechanics destroyed DB4's by cleaning them with brake clean just like they would with an aluminum Ralt RT4,of course the brake clean would destroy the glue in the Db4 tub. With my car, it was fine until I took off a right front corner about 6 years ago,it wasn't that bad a hit and seemed ok after it was fixed but gradually started to de-laminate on the right lower side. Eventually, that side had almost total hollow ping sound and when we jacked up a corner you could actually hear the chassis groan, yet I couldn't really tell much from driving except that mechanical traction got worse and shock and bar changes had less and less effect. As Paul mentioned in his excellent comments(thanks),the lower section of the tub where, fiberglass,composite.and aluminum are sandwiched together is most often the problem area. I checked in to fixing mine and talked to a couple of shops here in Indy and to do it properly requires almost total disassembly of the tub so I got some VERY expensive quotes. Aparently, there is a method of drilling holes in the de-lam area an then injecting glue there, I was told that sometimes this will fix a small problem area. I hope your tub sounds are "solid". Good luck!

[Mika]

So is the low price of a DB4 a reflection of the worth of the car on a performance basis or because of the issues with bonding. Thre prices are cheap,but is it going to cost me an arm and a leg to deal with any problems that arise, or is it just a normal part of onging maintenance?

[Mark H]

At a CMP reg. this year all 3 types were there RT-41, 008 and DB-4. In the race that all 3 finished the DB-4 won? They all had Toyota engines and were preped well, but it may have had something to do with the track or drivers? Looking at them all on the grid MAN the RT-41s tunnels were massive compaired to the Swifts, but the DB-4 did look more swoopy Russ. :~)
Adding to the thread, do any of the Reynard F3 cars have tunnles and if so might they be able to hang with a Swift or a Ralt?

[Mika]

In the NZ Atlantic series in the early nineties the 90h was competitive with the DB4's, but the Swifts usually one out. The Reynard 92H/93H dominated the series over the Swifts. It wasn'ttill the RT40 arrived that the Swift had any real opposition. One driver was able to push the 92H witha DB4 though. His name was Jos verstappen...

[Paddy O'Brien]

The Swift DB4 that I own is tthe Tasman winning Jos Verstaapen car that I bought(thru Sandy Dells) from Grame Lawrence Racing in New Zeland. The car was in Castrol colors when I got it (Greg Murphy's seat)but was dark blue when Jos drove it. Jos has a picture of the DB4 on his web site,except for color it is the same car. I have been trying to find race reports of the 1993 Tasman series but have been unsuccessful,other than a comment of Jos recovering from a practice crash to win a race. I have a feeling that Jos crashed my car alot, it would explain a couple of things, I would be curious for more details of Jos' "history" with it. Is my car worth more or less because Jos drove it??

[stonebridge20]

I ran a DB-4 from 1993 to 1996. 1994-96 in the Toyota Atlantic C2 series. The DB4 was and is quicker in a strait line than a Ralt 40/41. Ask Bill Fickling why he put Mark Dismore in his "old vintage car" at Nazareth in 1996. I'll give you the answer...Too kick everybody's ass! That was the last pro win for a DB-4. The DB-4 doesn't come close in grip to the 40 or 41. I did 2 days of testing in a 40 at Savanna in 96 and was just in awe of the grip and sensitivity to bar changes the Ralt had over my Swift. At the LimeRock national in 94 I qualified 2nd at a 0:47:401 with Stan Wattles in a Ralt 40 at 0:47:299. The Atlantic lap record at LimeRock is a 0:47:1?? held by Steve Shelton driving a DB-4 in the last pro race held there. I just still think a DB-4 with the right prep and driven well on a long track can hold it's own with the 40's and 41's.
Any DB-4 owners want to let me have a crack at the Ralts at LRP or Pocono this year?

JMO, Mike Agnifilo

[Paul LeCain]

Mike,
We've never seen that the DB-4 is quicker in a straight line than the RT-41. We have seen, as I've said in other post in this topic, that it gets off corners better, and is especially good at long sweepers.
I still think that the current SCCA aero rules for tunnels favor the DB-4.

[Paul LeCain]

Stu Moore was the team manager. Steve Shelton was the driver.

[stonebridge20]

Paul,

Thanks for the correction on Shelton with the LRP lap record(they say the memory is the first thing to go!) I was in that race at Nazareth when Dismore smoked everybody in Ficklings DB-4. They were running Solex carbs for ALL top end power Formula Ford size brakes and if my memory is correct..2200lb right side springs with about 1/4" of ride height. He went past me like I was going the other way!
Hey...How about a few laps at LRP in your Ralt so I can compare?

Mike

[Sammy]

Mike which vitage car was it ?
I haves his 1989 pro car.
is this the same car mark dismore drove.

regards sammy

[stonebridge20]

Sammy,

I don't have a clue as to which car Dismore won Nazareth with in 1996. All I remember is that it was white and there wasn't much Swift left on that car. The uprites and A-arms were all Fickling design. The brakes were Formula Ford and the wings were almost flat sheets of aluminium. The engine was carbed with Solex carbs. The car was strictly an oval car and would take some doing to get back to road race trim. Hope this helps in some way.

Mike