Wind Noise

[Westfield 129]

My personal W11 has 13" wheels, 185/70s and a 3.9 final drive with a .68 (I think. Gearbox is a Datsun B210 5 speed) overdrive. About 22 mph per 1000 RPM. This would be better with the 15" wheels and 5..X15 tires when I get around to fitting them. I look forward to even more relaxed cruising.

The RHD car has 15s and the 5.00 race Dunlops, with a 4.55 final drive, less the OD 5th gear, that works out to about the same 22 mph/1000 rpm as my car. The gearbox is a CR Type 9. The RHD car is about 50 kg heavier empty than my early, alloy floor chassis.

I had a ribcae in my car, with the 4.55 standard final drive, and the constant 4000 RPM at 60 mph finally relieved the #2 piston of its top ring (not an unusual failure), as well as breaking a couple of pressed metal rockers. I got tired of the wound up engine and having to drive around at 5000 RPM all the time just to keep up with traffic. The Datsun 5 speed was a great help, as was the 3.9 final drive. Now, I can get 40 mpg, and a sub 4000 RPM cruise at 80 mph, which works out well for the long tours I occsionally participate in. And, at 80, the engine is right in the middle of the power band, so I can accelerate to pass without down shifting in most cases.

I have plenty of HP (over 104 HP at the rear wheels) and even with 15" wheels, I don't think that I will loose much acceleration. The car is pretty light, at about 540KG with me in it, and full fluids.

The W11 takes a bit more HP to get down the road than the more slippery Lotus 11 (better engine compartment aero, sealed engine compartment, skinnier tires and full undertray). Even then... I have plenty of power to exeed 120 mph.

As for needing a wider road for top speed runs, my car tracks besutifully, with no problems of twitchy steering (even with the fat rack). One of the things I have noticed in the re building of a few W11s is that they are never properly aligned, with considerable TOE OUT on ALL of the cars I serviced (other than those where I did the original alignment). The problem was that the tracking was not set with the driver installed, camber and ride height at proper spec. Evidently, nobody bothered to cut the tie rod ends enough to adjust the tracking to spec (I use 1/16" total toe in).

Put enough ride height into the chassis so that there is some suspension travel, and you wont have a problem with bump steer. Set the toe correctly, and the steering will calm down and you will be able to enjoy the car at speeds of more than 80 mph all day long. One of the things that amazes my other automotive journalist collegues is how well the car drives at high speeds, and how stable it is on the road, even when passing large trucks.

[Westfield 129]

Quick correction:

My Datsun gearbox has a .82 5th gear, which when combined with the 3.9 final drive gives a 3.2 (rounded off) gear ratio.

So... the 185/70/13 tires are 23.6" in diameter with the 3.2 final drive gives about 22mph/1000 RPM. 80 mph at 3600. With a 25" tall Dunlop 5.00X15, the RPM will be 23 mph/1000. or 80 mph at 3475 RPM (or so...). If it pulls to 6000, that's nearly 140 mph. If the bonnet stays on...

All I know so far is that it will pull easily to 120 mph (GPS + RPM), but the bonnet is lifting on the terry springs. I am sure that with some attention to the aifrlow inside the bonnet, 130 should be possible. That's 500 RPM below my rev limiter (an arbitrary limit to extend engine life, as the cam. valve train and HP are good for 7000).

Interestingly enough, the 15" wheel car with the standard Spridget 1275 rear end from '66 and the 15" Dunlop 5.00 race tires (24.8 or 25" diameter, depending on Tube or L version) gives the same top gear RPM/MPH as my car when paired with a "Long First" CR Type 9.

The RHD car with the long 1st gear T9 also has no problems with accelertion or starting on steep hills. I imagine that the 3.9 would have little effect on that car as well.

I guess you could consider this "Le Mans" gearing. 'Works for me.

As far as acceleration goes, it will pull a Subaru STi in a drag race to nearly 100 mph. Pretty quick. It gets off the line quite a bit faster, and it takes nearly the entire quarter mile for the STi to catch up (and it doesn't always catch up).

We have a lot of freeways here in So. Cal. and the 5th gear with the longer 3.9 ratio from the '71 US version really made the car much more useable for longer trips. I no longer worry about wearing the thing out, or having to drive in the truck lane to reduce RPM (I can cruise at 80 all day), and it's quick enough for any traffic situation I have run into. The Datsun gearbox has a marginally lower 1st gear than the old rib case, so the longer gear or taller tires are not a problem at all. I am looking forward to the installation of 15" tires and the taller Dunlops in the near future.

Oh, and since I am behind the windscreen, there is no buffeting, making the interior comfortable for the long trip. My baseball cap even stays on my head at 90 mph (and faster). Having the extra inch of suspension travel also smooths the ride a bit. As far as turbulence goes, it is as nice as the Bentley Continental convertibles that I am occasionally offered for long trips. I could not comment on noise, as I am deaf (for the most part, born that way), and wear ear plugs for long drives to protect what hearing I have left. Anyway, with the tempurfoam in the seat, and the tempurfoam stuffed into my ears, it's a pretty nice environment to enjoy the canyons.

[alleggerita]

The remark on pressure build up under the bonnet at speed is quite interesting. Do the racers amongst us, who are familiar with Elevens at high speed experience this as well and how do they fare with this? Charles?

Under-bonnet closure for aero purposes would surely introduce even more pressure build-up without any vent holes or so.

[Westfield 129]

The inside of the engine compartment of the Lotus 11 is quit a bit different than the open area beneath the W11 bonnet. The Lotus 11 has much attention to air flow (especially at the radiator, the front suspension, sealed off wheel arches, and the full belly pan. Lots of bulkheads and farings.

There was as much attention to drag reduction and airflow through the engine compartment as there was to bodywork.

The W11 just has a shell draped over the chassis, with an open radiator and an open floor, not unlike a production car of the 50s.

The problem with the W11 is that the radiator duct open to the engine compartment. A lot of air flows around the radiator as well. The Lotus 11 has the radiator enclosed, the air duct sealed around the front aperture, with the air exiting beneath the car. Air only goes where it is supposed to go. Further sealing around the front wheel houses keeps air out of places where it can cause additional drag.

Also, my car doesn't have a bulkhead behind the front wheels. The fabrication was so bad on my car that I ripped out the pieces that were there, and never replaced them. Eventually, I will seal off the engine compartment when I inatall new front enclosed ductwork with the smaller, double pass radiator. That should fix the bonnet lift problem.

Combine the high pressure air inside the bonnet, and the low pressure air over the top of the bonnet, and you get lift. The trick is to kill the airflow inside the bonnet by directing all the air through the radiator and out the bottom (captured within the ductwork, not acting on the bonnet panel). Sealing off the bottom of the engine compartment will help, as well as keeping the high pressure air in the wheel wells from pressurizing the engine compartment.

The idea is to direct the airflow through the engine compartment and out, as it is on the Lotus 11. Air has to flow through the car, as well as around it. The idea is to get the air in and out (for cooling) without it balling up and causing a high pressure (drag) problem.

[erictharg]

Anything over 90 and it does billow alarmingly. Flat out you do wonder if it will stay in place. I stiffened the trailing edge of the calm with a piece of high tech composite material (plywood) but it still moves a lot. Suspect I'll have to add a centre latch for Spa where I typically run to the redline in top at the end of Kemmel. With the 4AGE that's going to be somewhere over 120mph. The hood scoop I have fitted doesn't seem to make that much difference.

[erictharg]

BTW, I run the stock 1275 Midget 3.9 diff and my Rocket g/box has a direct top gear so I still have the 16 and a bit MPH per 1000 rpm of the Midget (on 145 13 tyres). So depending on which tyres I run I'm at anywhere from 115 to 120 mph at 7000 rpm. The 4AGE makes good power to 7500 so...
Re. wind noise I know that when seated (same for my current moulded race seat as the previous Westfield buckets) the wind hits me mid forehead height. So my face and ears miss the worst of it. A coupe of inches taller and it would be a lot more uncomfortable. Rain smacks me in the forehead hard enough to duck or stop to put my flying helmet on. I think if you are over 5' 10" you be well advised to use seat cushions direct on the floor as Jan suggests in place of the stock seats. If my car ever goes back to road spec that's what I'll do. Along with some nice narrow 3 piece 15" rims from Image to give me an extra inch of ground clearance and raise the gearing a little!

[Westfield 129]

I run 185/70s, as they are readily available here in the 'States, and fit under the bodywork. The down side is that the handling is more Caterham like, with a bit too much grip... But then, I have lots of extra HP and an LSD, so neutrality or over steer is available with little right foot pressure.

My old setup had me at 15 mph/1000 RPM, and this caused some premature engine wear (scintered rocker and top ring land failure, sort of a standard failure when the car is run at a constant 5000 RPM) in our 70~80 mph traffic. The 3.9, over drive 5th and the taller 185/70s make it tollerable (if not relaxed), and my engine is doing fine.

Moving to 15" wheels doesn't really give much more than 1/2" of additional ride height (over a 185/70/13 if you use the 4.50x15 and 5.00x15 vintage race rubber. One problem you will run into is that tires larger than the 4.50X15 vintage Dunlop race tire is that they wont fit up front. Even though the 4.50 and 5.00 is a vintage tire, the aspect ratio is relatively low, at 60 or lower. The reality is that there are not many tires that fit up front unless you want to go to a lower profile tire, which will likely require a wider rim. From a fit, handling and feel standpoint, 4.50X15 Dunlop racing or equal sized bias ply front tires are the only way to go.

[erictharg]

We can still get 155 x 15 tyres readily in the UK so I'd plan to use that size. Or maybe 165s on the rear if I have the room. We'll see when or if I put it back on the road!

[Westfield 129]

155/15s have not been successfully fitted here. Problems with contact with both the headlight buckets (ripping out the wiring from the back of the headlight envelop), and contact with the inside of the clamshell up top at full suspension compression. There is also additional limitations to steering lock and contact with the lower alloy body panel behind the wheel with suspension extension when steering. This is a problem for both early and late chassis. I know of several owners who tried the 155/15 Michelins and found that the car could not be driven on them. Fitting the Dunlop vintge tires in 4.50X15 in front fixed the problem. 5.00X15s were fitted up front.

While 155s or maybe 165s might fit in the rear, the real problem is up front.

The 4.50L /15 fits fine, and the diameter is 24". Any larger (and my experience is even 1/16" more is too much) will cause problems.

The aspect ratio on the 4.50X15 is 74%. The 5.00LX15 diameter is 24.8". Aspect ratio is 66%.

You might want to compare these numbers to the dimensions of your available 15" tires.

I imagine that you could use the 4.50X15 and 5.00X15 R5s, if they were available. 'Same dimensions as the CR vintage race rubber.

So far, I have not found a 15" metric radial road tire that was the right diameter and aspect ratio for the W11. There are some sizes that may fit, but the side wall is too short, and the recommended rim width may be beyond 5 or 5.5" that you can successfully fit to the W11 without making a mess of the steering geometry and scrub radius. Oh, and they feel funny. Sort of wiggly, with a harsh ride and mushy steering response.

Otherwise, you can successfully run 185/70/13, or 165/13 tires for a little more tire diameter without fouling the chassis and body.

Meanwhile, save your money. The 155s probably wont work.