Lotus Elan

New member, recommissioning +2 race car

PostPost by: Crossle32F » Thu Jan 10, 2019 5:54 pm

Hello all from Vancouver BC Canada,

A couple of years ago I bought my first Lotus, this +2 race car #502105:

https://bringatrailer.com/listing/1971- ... -race-car/

The previous owner in Colorado ran it as a road car, then converted it to a vintage race car, last raced in 2006 in Denver. I've only seen one other +2 race car here in North America, an almost identical one which sold about 4-5 years ago out of 'Fantasy Junction' in Calif.

So, after being distracted somewhat with long-circuit shifter kart racing with my son, I am finally getting to recommissioning the +2 for this season of vintage race events here in BC, Washington State, and Oregon. Along with the expected brake system rebuild and replacement of 10 year old tyres, I've had additional side and footwell protection put in the cage and need to add silencing to meet current race rules. Next jobs will be to sort out rain tires, and gearbox and gearing. The car has what appears to be the stock 4 speed and diff in it, I'll have to get the car up on the stands and figure out what the actual 4th gear/final drive ratio is - two of the tracks we run have very long main straights and I suspect the gearing will be too short. I did receive a new uninstalled LSD with the car, so it may make sense to install this along with a tall (3.5?) final drive. At some point, a race gearbox may be the way to go if budget allows. Anyway, I'll scan the forums for gearing discussions.

My car & racing issues started with kart racing as a teen in 1979, roadracing 'bikes and Formula Fords (at the greatly missed Westwood circuit near Vancouver, now houses), then F2000 and rallying in Ontario up to the mid 1990's. I'm a mechanical engineer, having worked first in aircraft structures, then medical devices. It has been great to come back to racing via karting with one of my two sons. The +2 has been on my wishlist for years, along with an Elite (a little out of reach now, though).

Great forum, love the no-nonsense guidelines

Cheers!
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PostPost by: Slowtus » Thu Jan 10, 2019 7:31 pm

Welcome!

'bout time you got that on the track! (I'm the guy with the S2000 engined Mk1 Cortina, we chatted at the ABFM a couple of years back).

This car is an absolute beauty so if you get the chance to see it in action - do so.
You may want to get in touch with Ian Wood at IWE for the diff bits, he found all the parts I needed when I blew the diff in that Cortina (wonder how THAT happened :shock: )
Keep posting here and let us know when you will be hitting Mission etc.

PS, if you ever want to sell it... :D :D :D
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PostPost by: StressCraxx » Thu Jan 10, 2019 9:11 pm

Hello Crossle,

Welcome to the fold. There are several vintage racers here on the forum, so you're in good company. We have a roadgoing 67 Elan DHC and a Crossle 25F for vintage and club racing.

We were in Portland in September for the Columbia Classic which was a great time for all.

Your car looks familiar, perhaps once owned by Joel Farber or Dan Wardman here in the SF bay area.

Regards,
Dan Wise
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PostPost by: Davidb » Fri Jan 11, 2019 12:48 am

Welcome to this excellent resource! We have met, at the ABFM and elsewhere, also we have a mutual friend in Ed L of karting fame.

I believe you are having problems getting the car accepted by the local organization-of which I was one of the founders. Back then rules were to be avoided-now they are apparently the reason to race...

There are a lot of Elan racers on this forum and they should be able to help you.
'65 S2 4844
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PostPost by: Slowtus » Fri Jan 11, 2019 2:07 am

Davidb wrote:Welcome to this excellent resource! We have met, at the ABFM and elsewhere, also we have a mutual friend in Ed L of karting fame.

I believe you are having problems getting the car accepted by the local organization-of which I was one of the founders. Back then rules were to be avoided-now they are apparently the reason to race...

There are a lot of Elan racers on this forum and they should be able to help you.


Accepted?

Please enlarge on this.
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PostPost by: rgh0 » Fri Jan 11, 2019 8:29 am

The diff ratio you need will depend on the revs and power output your engine can put out as well as track type you compete on. In general you should be able to run a 3.77 or 3.91 diff if you have long tracks and a 8000 rpm engine. In general the lower the diff the better. On short tracks generally 3.91 or 4.1 will be better. i use a 3.77 in my Elan with around 180hp and a 8300 rpm limit as that works best on the range of tracks I compete on. In a heavier Plus 2 maybe a 3.91 would be better compromise on the tracks I compete on.

cheers
Rohan
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PostPost by: Davidb » Fri Jan 11, 2019 4:40 pm

Further to rgh0s comment-I used a 4:11 in my 26R at Westwood, Seattle, Portland and Laguna (~8000rpm rev limit). Mission didn't exist then and you might get a slight benefit with a lower ratio at Mission but it is probably not worth the effort. I really don't see racing with a 3:55 anywhere around here!
Perhaps you can relate your problems with getting your car accepted locally?
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PostPost by: Crossle32F » Fri Jan 11, 2019 5:37 pm

Thanks, good to hear from you guys, yeah Ed L is a terrific guy, he's been helping me out since my karting days in the early 80's.

Regarding local acceptance of my car, it was all to do with the cage passing tech, not eligibility. Local tech specifies 'two side protection bars', but what is not specified is that this assumes a car with a steel sill (rocker) or some sort of perimeter structure other than fibreglass. Not so with the Elan, of course, so the inspectors wanted a third side bar. Also on my car the side diagonal bar had a sliding joint and pivot, so you could swing the side bar out to get in & out easier - beautifully made, but not technically legal as the sliding tube engagement was not a full 3". Local rules also require a member going forward from the front hoop to the footwell, as a result of some past incidents of front wheels getting pushed back into the footwell on impact.

This is all required on both sides, even though there is no passenger seat in my car. So, I was a bit irritated because the car has an RMVR logbook with entries up to 2006 (so not totally out of the modern era), the cage tube is a full size over the minimum for the car's weight, and it is clearly a professionally built car with a robust cage. But, it turns out SCCA and SOVREN (the vintage series that runs in the Northwest US) rules are similar and a local fabricator was able to do the work at a reasonable cost, so I just got the mods done. Bugs me to have to add grodge and weight on the passenger side, but at least now the car should be legal most anywhere. And, I came around to thinking, why not make it safer?

Here is a great video clip Ed L passed on to me (I think originally from Davidb?) of an Elan cage. Note the structure going forward into the footwells. Funny though, it would seem that technically this cage would still need one more sidebar on each side!
https://www.facebook.com/SafetyDevicesI ... 119109182/

Cheers,
Kevin
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PostPost by: Crossle32F » Fri Jan 11, 2019 5:53 pm

rgh0 wrote:The diff ratio you need will depend on the revs and power output your engine can put out as well as track type you compete on. In general you should be able to run a 3.77 or 3.91 diff if you have long tracks and a 8000 rpm engine. In general the lower the diff the better. On short tracks generally 3.91 or 4.1 will be better. i use a 3.77 in my Elan with around 180hp and a 8300 rpm limit as that works best on the range of tracks I compete on. In a heavier Plus 2 maybe a 3.91 would be better compromise on the tracks I compete on.

cheers
Rohan


Interesting, dyno sheet from the previous owner shows 160 hp & peak torque at 7300 rpm, peak HP of 162 at 7500. So then probably I won't be able to pull taller gearing after all. Our local track (Mission) is tight but Seattle, The Ridge, and Portland (without chicane) all have really long (~ half mile) straights. I'll get the car up on the stands shortly and figure out the ratios.

Do you run a limited slip diff? I wonder if it is worth putting mine in if I don't need to change diff ratios after all?

Cheers,
Kevin
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PostPost by: 661 » Fri Jan 11, 2019 6:11 pm

Kevin,

Pleased you like the car!

https://www.facebook.com/SafetyDevicesI ... 119109182/

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PostPost by: The Veg » Fri Jan 11, 2019 6:32 pm

Welcome! That far looks like a real beauty and sounds ferocious as hell!
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PostPost by: rgh0 » Fri Jan 11, 2019 10:59 pm

Hi Kevin

Yes i use a Quaiffe LSD. The main benefits are for standing starts and coming out of left hand bends in my right hand drive car. A Plus 2 with its wider track and heavier weight is less likely to spin wheels coming out of turns. If your racing does not do standing starts then I would first try without to see if its needed.

It sounds like the engine would benefit from some more head work also as another 10 to 20 hp is not that hard to get. Your in the right part of the world to talk to John McCoy at Omnitech about that.

cheers
Rohan
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PostPost by: stugilmour » Tue Feb 12, 2019 8:10 pm

Welcome aboard Kevin. Great to see you and your lovely car here.

Plan is to come down your way for ABFM with my P,us 2. Hope to see you there.

For Seattle are you meaning Pacific Raceways? If so don’t think a taller diff will help there. Not personally familiar with the other tracks yet (Track Days only rather than racing).

Agree with Rohan regarding John at Omnitech in Bellingham.

Cheers!

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PostPost by: Crossle32F » Tue Apr 16, 2019 12:50 am

Davidb wrote:Further to rgh0s comment-I used a 4:11 in my 26R at Westwood, Seattle, Portland and Laguna (~8000rpm rev limit). Mission didn't exist then and you might get a slight benefit with a lower ratio at Mission but it is probably not worth the effort. I really don't see racing with a 3:55 anywhere around here!
Perhaps you can relate your problems with getting your car accepted locally?


So, regarding gear ratios, my concern was that I'd be geared too short (ie. topped out at max revs) on the long straight tracks like Pacific Raceways or Portland (without chicane). So, having no data on what went in the car I estimated ratios by turning the engine and counting turns on the driveshaft and rear wheels (ensuring both rear hubs turn ~equally, since it is an open diff). This won't be exact because I didn't put precise markers (like a degree wheel) on the rear hubs or the driveshaft, I just marked one bolt/stud and turned the engine until I could eyeball a whole number of complete turns at the driveshaft/axle, using the 30 degree span of timing marks on the engine to get fractional engine turns. This is what I get:

Overall ratio engine-drive wheels:
1st: 13.1:1
2nd: 8.9:1
3rd: 6.3:1
4th: 4.4:1

1st gear ratio is about 3:1 (driveshaft turns about 1 turn per 3 on crankshaft), so the diff is about 4.36:1, giving individual gear ratios in the box of:
1st: 3.0:1
2nd: 2.0:1
3rd: 1.4:1
4th: 1.0:1

So 4th gear is straight through.

Based on the overall ratios and a static, unloaded tire circumference (ie. tire off car, at pressure, measured on tire centreline) of about 72 inches I calculate 115 MPH @7500 RPM (where dyno sheet shows peak of 162 rear wheel HP), and 122 MPH @ 8000 RPM (156 HP).

Does this make any sense? Is there such thing as a 4.36 diff? In any case, with 160 rear-wheel HP I wonder if it would be expected to manage more than ~120 MPH anyway?

Hopefully I will have the car out at Mission Test & Tune this Friday, and if that goes well Seattle (Pacific Raceways) SOVREN test day a week later, in which case I'll go with the gearing as-is and see what happens. I'll eventually get the limited slip diff put in anyway, so can make a final drive gearing decision then.

Cheers, any thoughts appreciated!
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PostPost by: rgh0 » Tue Apr 16, 2019 10:48 am

It looks like you have a 4.4 diff which i think was sourced from some of the commercial vans that used the English diff. This will help get a Plus 2 out of the corners well and will suit a tight track but is probably a little high a numerical ratio for a longer more open track.

You really need to drive the car on the track in question and see how the ratios suits the tracks corners and straight lengths for your car weight, HP, tyres size and driving style. For a Plus 2 thats stripped for racing at around 800 kgs with an 8000 rpm 160 hp engine and if running something like a 185/60 x 13 tyres I would start with a 3.9 or 4.1 diff as this would be a suitable compromise for most tracks if you do not want to swap diffs for different tracks. After that its do the testing and decide if you need to change the ratio up or down and how often you want to change it to suit a particular track.

cheers
Rohan
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