Lotus Elan

Modified Elan Dyno Data

PostPost by: rgh0 » Thu Oct 20, 2005 2:00 pm

I have posted in the photo gallery section in the "Rohans Elans" folder a word document with details of the various developed engines I have built over the years and the dyno results for these engines compared with a standard big valve twin cam.

The latest engine I have just finished and dynoed is "engine 3" a nominal 170hp spec 1600cc twin cam. It produced a very tractable 98kw / 131hp at the back wheels an estimated engine output of 171hp at 7000 rpm with more power and torque than a standard sprint engine across the total rev band. A road compression ratio version of this engine would produce around 165hp and be totally street tractable.

The rear wheel output is the same as the dyno measures on the properly setup , throttle body injection 20 valve 1600cc Toyota 4AGE engines at similar rpm that they put in their Elfin clubmans ( a Lotus 7 clone). Not bad for 40 year old engine design. Elfin have just started building their latest clubman, a 6 litre Gen 111 GM V8 in a clubman style body !! A power to weight ratio that puts just about anything less than a F1 car to shame.

Rohan
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PostPost by: type26owner » Thu Oct 20, 2005 2:59 pm

Rohan,
I'd love to see the graph of the lambda readings. I've never even come close to those types of steady readings. If the AFR stays within 1 I'm happy as hell. What type of lambda sensing instrument was used? Got the feeling you're exceptionally lucky to have the carbies flowing that precisely. Good job and thanks for sharing the data!
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PostPost by: rgh0 » Fri Oct 21, 2005 11:20 am

Keith

No graph of the lambda data, the dyno is a fairly old one with just readouts no fancy computer to graph it all. The system was basically a standard bosch sensor feeding into a handheld display readout unit that was also used for the dyno load control and read out of dyno speed and load. The carbies had a fairly linear trend from .88 at 3000rpm to .85 at 7000 rpm. The dyno guy apologised he could not get it steady at .88 over the whole revs range ! But he was satisified overall with the outcome as pretty good and better than usual.

I think 45's are generally a better made carb and easier to setup than 40's.
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PostPost by: type26owner » Fri Oct 21, 2005 1:50 pm

I think 45's are generally a better made carb and easier to setup than 40's.

The guts of the 45 is the same as the 40 though. What is greater is the throughput of air. It's the amount of pressure differential generated which drives these thingies and more must be better. For you to generate that amount of horsepower over a stock engine requires the amount of air going through the engine to be somewhat proportional to the power. It's the higher airflow I reason which makes the lambda more steady and it easier to tune. Also that O2 sensor is most likely an analog type which provides a huge amount of smoothing. Bet if it were a digital meter with a 80 millisecond resolution the lambda would be bouncing all over the place a little bit more.

I count six companies have now come out with a wide-band O2 digital meter with the most recent entry being NGK. Bet Bosch is not far behind!
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PostPost by: rgh0 » Sun Oct 23, 2005 9:50 am

Keith

A few key differences with the 45DCOE54's compared to my original 40DCOE31's which make a difference to its performance

The guts are held in place with a lock screw rather than the spring clip so no leakage and a consistent vacuum signal.

There is a throttle bypass with a metering screw for independent setting of the correct throttle plate position and idle speed.

The cold starting device does not leak fuel out the air inlet on hard cornering.

The lamba meter had a digital read out but was clearly damped as only changed about once every 2 seconds at its fastest.

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