Purchased in May 2016 the Elan is being modified to a lightweight specification. The car is fitted with a Lotus galvanised chassis, which is in excellent condition and replaced at some stage in its life.
Over the past few months I have fitted a 26R alloy radiator/swirl pot and alloy fuel tank supplied by Tony Thompson Racing. A Safety Devices Roll Bar and side intrusion bars are also fitted to the car with 3 point harnesses. A cable operated plumbed-in fire extinguisher has also been installed behind the rear bulkhead.
The differential was rebuilt with an alloy nose and steel billet output shafts. Not an easy job to remove the diff from the car and unfortunately there was a problem with the rebuilt unit supplied by Tony Thompson Racing. They were immediately on the case and the diff was removed by Gerry Wainwright Motorsport.
Gerry Wainwright fitted solid driveshafts and an ATB (Automatic Torque Biased) Differential fitted with alloy nose casing. To protect the new driveshafts limited droop shocks were fitted. All these parts were supplied by Tony Thompson Racing.
A track day at Castle Combe proved the new ATB and driveshaft configuration, which provide excellent grip and traction. Unfortunately lack of oil pick-up caused a potential main bearing failure. Engine removed and shipped to Craig Beck Racing for investigation. The noise that occurred when the engine failed was due to a Weber trumpet fixing nut becoming loose and sucked into the cylinder causing piston and valve damage – pretty unlucky but a lesson to be learned. When refitting the trumpets nyloc nuts or threadlock will be used. Engine report from Craig Beck Racing showed bent valves and a damaged piston!
Engine removal from the Elan engine bay is not easy due to the limited width. All ancillaries were removed including the Fuel Pump. The block was raised on a hoist and moved across to allow the exhaust manifold to be pulled off the studs. Once the bell-housing bolts are withdrawn the block slides off the splined shaft.
Engine now rebuilt with cams reprofiled for improved power. The dyno results show a peak power of 133bhp at 6250rpm, which is more than adequate for a road going/track car. The engine is run on the dyno for about 2-3 hrs to bed in the bearings, piston rings etc. When fully ‘run-in’ the power runs start by slowly increasing the peak revs and monitoring the mixture by use of a lambda sensor. The Weber jets are then tweaked for best performance over the full rev range.
Craig Beck Racing refitted the engine to the car and checked engine performance on a rolling road.
The car was collected from Craig Beck Racing. Work will now continue with a front brake upgrade.
AR alloy calipers now fitted with their alloy mounting brackets and matching discs. The mounting brackets are a few mm thinner than the original Lotus steel parts. This causes the caliper bracket bolts to foul the disc to hub mounting bolts when the hub is tightened. The solution was to remove the lockwashers from the caliper bracket mounting bolts and use loctite to fix the threads in place. The disk also fouls the track rod end so added some spacer washers to the steering arms to ensure the track rod end will not touch the disc on full lock. Have reset the tracking due to this change in geometry using the string method.
Original servo now removed and a larger bore master cylinder fitted. Pedal feel should be improved without the servo and the slightly larger master cylinder should compensate for the loss in braking effort provided by the servo.
Took the car to Neil Slark Racing rolling road for power check. The engine was significantly down on power when compared to the dyno tests. Neil Slark suggested a larger exhaust as the fitted ‘pea shooter’ as he called it was restricting gas flow. Purchased a fast road exhaust and silencer from Tony Thompson racing, which is much louder than the ‘pea shooter’. Returned to Neil Slark with the results showing a noticeable gain in bhp and torque (now 100bhp at the wheels).
A 123 mappable ignition was fitted before the rolling road work. This distributor, which looks identical to the Lucas original allows the ignition map to be adjusted via a bluetooth connection. The map was tweaked for 16deg at 1000rpm increasing to 36deg at 4000rpm.and above. This ignition map gave the smoothest power delivery over the entire rev range.
Still more power to be extracted from the engine so purchased a large bore manifold, which was not easy to fit and required both engine mounts to be removed to allow the manifold to fit over the exhaust studs.
By the time this work was completed Neil Slark had moved to so took the car to Janspeed. Power runs showed no improvement, in fact a slight reduction in power even with larger main jets fitted due to improved gas flow.
June 2017
The results were a mystery so a wideband lambda sensor was bought with a venturi attachment which fits directly into the exhaust. This sensor with a digital analogue readout manufactured by innovate motorsports allows measurement of the air/fuel ratio when driving the car on the road.
With the engine started and warmed to operating temperature the carb balance was checked with a airflow gauge. Idle mixture was set with a Colourtune with each cylinder set for light blue/orange as the lambda sensor output was erratic at idle, probably due to insufficient gas flow from the exhaust.
Then a road test with the car to check mixture under load. Results showed too rich a mixture (Air Fuel Ratio of 11-12:1 typically across the rev range (145 main jets and 50F9 idle jets fitted). These were replaced with 45F8 idle jets and 130 main jets. Having retuned the idle with the Colortune another road test was very promising with AFR maintained at 13:1 under most load settings. The engine is running weak on the overrun and rich on WOT before the mixture settles. The results confirm the jet settings to be pretty close to optimum with the spark plugs light brown. A rolling road test will confirm engine performance.
As the speedo and tacho do not provide stable readings a set of instruments were purchased from Digital Speedos. The tacho is driven by a signal from the ignition coil and the speedo uses a GPS sensor, which acquires the satellites in a less than a minute. With both instruments installed, accurate speed and rpm readings are provided. Both instruments are designed to work with -ve earth. As the dash is wooden and isolated from chassis a the supply and return to the instruments were swapped over. A relay was also added to allow the internal LED backlight to operate with a positive earth car.
January 2018
A new front wishbone set was fitted as on inspection the original wishbone mounting holes had beed filed out to adjust camber, which is not a particularly safe method of adjustment.
March 2019
Fabricated a bump steer gauge using 18mm plywood some piano hinges and a dial gauge. The car set for a ride height of 145mm measured under the front cross member, which gives approximately 0.75deg negative camber with the Tony Thompson wishbones fitted. The shock/spring assembly was removed to allow free movement of the front suspension. With the bump steer gauge bolted to the hub the suspension was raised and lowered +/-50mm from normal ride height. With the steering wheel locked the dial gauge measures hub rotation as the suspension moves vertically. Any rotation, which undesirable is due to the steering arm not travelling in the same arc as the suspension and this causes bump steer. By adjusting the steering rack height the hub rotation can be reduced. Measurements on both sides of the car showed significant bump steer and this was reduced by introducing shims under the steering rack (2mm was added to each side).
June 2019
Fitted an SD card to the Innovate LM2 AFR gauge and also fitted Keith Frank’s idle hyperjets, which give better adjustment of idle mixture. With the lambda probe fitted to the exhaust a 15 minute road test was performed and the AFR, RPM and throttle position were logged (a throttle position sensor was fitted to the Weber). The SD card data can then be viewed with the Innovate Logworks software, which has a statistical analysis tool. The table shows AFR readings against throttle position and rpm. The results after selecting the optimum jet setting are shown in the table.
1V is approximately 3/4 throttle and ideally looking for 12.5AFR in all conditions. The results are average values so the results are looking within the 10-14 range.
August 2019
Trip to Goodwood for a Lotus On Track day, car ran well except for a a blowing exhaust by mid afternoon, hopefully a simple fix and not something more sinister!
Incorrect diagnosis as just found a loose air box causing a lot induction noise, easy fix.
robblotus 