Lotus Elan

vacuum retard port with stromberg carbs

PostPost by: chickenstock10k » Thu Mar 14, 2019 3:28 pm

John, how did you shift the advance curve? Did you just go with a euro dizzy or petronix?
chickenstock10k
Second Gear
Second Gear
 
Posts: 60
Joined: 02 Dec 2018
Location: East Coast, USA

PostPost by: JohnCh » Thu Mar 14, 2019 3:59 pm

I replaced the stock distributor and Pertronix Ignitor with a programmable 123 Ignition distributor. After the initial install, I programmed in the stock Federal curve, then the next weekend replaced the B1G needles with B2AR and programmed in the non Federal curve. The car already had the secondary throttle system removed and intake manifold replaced with a custom setup as per this thread, carbs modified for adjustable needles, and a header from RD Enterprises, so changing the advance curve and installing the richer needles were the final steps in converting the engine to non-Federal spec.

The 123 Ignition isn't a cheap approach, but I like the flexibility of being able to easily optimize the curve on the dyno as changes are made.

-John
User avatar
JohnCh
Second Gear
Second Gear
 
Posts: 55
Joined: 31 May 2018
Location: Seattle-ish, USA

PostPost by: SENC » Thu Mar 14, 2019 8:19 pm

If you want to stick with points, Distributor Doctor carries the correct springs, weights, and points for the 40953 version that has the non-Fed advance curve so you can use your current dizzie. He also has (or did a month ago) some NOS distributors that he can build to your spec if you want to keep your original original.
Henry
69 S4
SENC
Third Gear
Third Gear
 
Posts: 388
Joined: 30 Dec 2015
Location: NC

PostPost by: denicholls2 » Fri Mar 15, 2019 2:35 pm

JohnCh wrote:The Federal advance curve really impacts drivability.


California owners cover your ears.

I guess everybody wasn't there at the time. My initial response was "Of course it does!" We tend to think of tuning as optimizing; what most may not remember is that Lotus was optimizing to a set of numbers that would determine whether or not they stayed in business.

Being able to sell in the U.S. market without adding a hardware store under the bonnet was a HUGE advantage in cost, weight, and power. And the U.S. market wasn't racing these things, the competition was MGBs and TR6s used as second cars for summer commuting and weekend excursions. The 2-ton Chevy in the driveway had at least a hundred more horsepower if that was your thing. My family's 1969 Dodge station wagon (Estate) had a 383 V8 under the hood and was nothing too special. We lived, and still do to some extent, in the Land of Cubic Inches. But even Chrysler had to bump their family engine to 400 cubes to power the dreaded pump.

Lotus did what they had to do to sell in the market. VW's Squareback was injected at the time, showing the way forward, but the technology wasn't in general use as it would be 20 years later. There were no other options but to make these cars run like crap to make the numbers. Unleaded fuel and catalysts were still in the future then though coming quickly.

And the motoring press, while sympathetic, wasn't excusing them when they did this.
denicholls2
Fourth Gear
Fourth Gear
 
Posts: 567
Joined: 23 Jan 2006

PostPost by: 1owner69Elan » Fri Mar 15, 2019 7:34 pm

Yes, Lotus and other manufacturers faced a daunting task trying to adapt their cars to the new Federal emissions standards. Many of them turned to the Stromberg Zenith CDSE carburetors as a way to quickly and relatively cheaply conform. The net effect was deleterious to performance. But, there weren’t a lot of other options at the time.

The engineer that designed and tested the Lotus Stromberg emission system recounted to me the agony of getting the Elan to conform to the standards. The saving grace to him was that WOT throttle performance was not compromised. This fellow emigrated to the US shortly after the system was fitted to the Lotus to work on piezoelectric fuel injection systems. In the US, he drove a RHD Lotus Cortina and got regularly pulled over by the police for a) wondering who was driving the car – as there was no one in the driver (LHD) seat and b) his quite aggressive driving style.

I don’t agree that the Elan was competing with the Triumphs and MG’s of the period. The Elan was significantly more expensive at $5K. The TR’s and MG’s were a bit more than half that price.

In fact the Elan was up against some rather stiff competition. The Corvette, with 3x horsepower (and twice the weight) was a similar price ($4.5-5K). The XKE was $5.5-$6K. The US buyer predilection for cubic inches (Corvette) and the sexy allure of the Jag made the Elan a tough sell.

I purchased my new 1969 Elan S4 SE, for overseas factory delivery, for $3.5K, a savings of $1.5K. At that price it really was a “no-brainer” for me. This was essentially the UK kit price. I had lusted after the XKE as a teenager but it was really out of reach at the price. Heck, you could also buy a used AC Cobra 289 for similar or less money than a new Elan. But, if you drove any of the competition they all came off as ponderous. The Corvette and Cobra were rough and brutish although the raw power was exhilarating – especially in the AC Cobra.
'69 Elan S4 SE
Street 181 BHP
Original owner
User avatar
1owner69Elan
Fourth Gear
Fourth Gear
 
Posts: 561
Joined: 16 Jun 2015
Location: California

PostPost by: JohnCh » Fri Mar 15, 2019 8:30 pm

My point about drivability was specific to my comment in that same post regarding throttle response. I've owned three cars with DCOEs and currently have another with ITBs. Properly set up, the throttle response is razor sharp. In contrast, my Strombergs had a 2-stage delivery akin to a modern turbo (torque upon throttle opening, followed by a stronger surge of torque a heartbeat later). Based on comments I've read when researching these carbs, I incorrectly assumed this was purely due to the CD design and just something I had to accept. Upon moving to the non-Fed curve I quickly realized that the Fed curve compounded the problem. This doesn’t mean my Strombergs now feel like DCOEs. They don’t. But they no longer stand out as being deficient in this area. They ain’t great, but they ain’t bad either.

-John
User avatar
JohnCh
Second Gear
Second Gear
 
Posts: 55
Joined: 31 May 2018
Location: Seattle-ish, USA
Previous

Total Online:

Users browsing this forum: No registered users and 6 guests