aerobod - near CYYC

You can unplug the Lambda sensor and it will stay in open loop control. Also, when the engine is above 60C and the car is re-started, the Lambda closed loop control will typically not start for 60 seconds (can be other settings such as 30s, 120s, etc, depends on MBE setting tuner has used). If either of these conditions cause a change in engine behaviour and the engine behaves better when the sensor is not causing closed loop control, then the sensor is probably bad.

The black plastic piece does free-float, shouldn't be a problem if the outer cable is not kinked. The air filter bottom "hooks" that go into the backing plate look a bit close to the Jenvey return spring and guide rod, I would confirm there is no touching there. I would also check the cable on the exhaust side of the engine to see that it runs far enough away from the exhaust that it is not affected by the heat or degraded from it.

With those throttle butterflies, 0.05mm of movement is enough to send the idle up or down by hundreds of RPM. They may be held open by tension in the throttle cable, ensure the throttle quadrant is always touching the throttle stop at idle with the engine cold or hot. Other issues are that the throttle stop may also have moved or the balance between each body may be off. If you have Easimap, check the TPS voltage at the idle position, if not put a volt meter on the TPS and check the voltage at idle. If it is a standard Jenvey system with Colvern TPS, it should be about 0.30V (or 4.70V if reverse wired). I would then put some slack in the throttle cable by marking the existing position of the cable tension adjuster at the throttle body end, then slacken it off a few turns. Next is to check the existing throttle stop position, mark it, then check when the stop is slackened off that the butterflies completely close and the TPS voltage drops about 0.05V, then return the stop to the initial position. Each throttle body should also be checked with a synchrometer for air flow at idle to ensure they are as close as possible in flow rates, if not close down all the bleed screws, pick the throttle body with the highest flow rate, balance it's twin in the same body with the bleed screw, then adjust the linkage between each throttle body pair to get the same flow rate for each pair. This is an iterative process. This document from SBD gives a lot of good info for Jenvey throttle body setup: https://www.sbdmotorsport.co.uk/app/uploads/2020/11/2L_Duratec_TP-DURA-2-0L-K3_Taper_Throttle_Kit_Instructions.pdf Be aware that if you move the TPS, it will affect your mapping overall, ensure you know what it's starting position is if you do move it. It is worth checking it's full range with Easimap or a voltmeter, wired in the increasing voltage with throttle manner, it should go from 0.25V with butterflies completely closed to close to 4.50V completely open (move the quadrant by hand to the full open position, as the throttle pedal may not be opening it fully)

In 13" size there are only 175-50-13, 185/60-13, 205/60 and 235/45-13 available. With 8" wide rear wheels and 250bhp+, 235/45-13 is the only size that is certified for the rim width and will give the required traction out of full throttle corners. 185/60-13 on 6" wide front wheels is the widest size to fit under the standard wings and stays and is closest in diameter to the 235/45-13 rears. For track use, it is a good combination. I'm now on my 3rd set of them.

I had been a bit slack in putting a split pin in place of the 'R' clip as I didn't have the right size in my parts box, until last night when I accidentally popped the 'R' pin out when turning the throttle quadrant by hand to confirm the maximum TPS voltage hadn't change since before the rolling road session. .......First task this morning was to go to Canadian Tire when they opened and buy a pack of 1.6mm split pins, now no risk of the pin coming out and potentially jamming the throttle with disastrous results.

Put a strengthening strip on the inside of the bonnet, across the crack area and laminated with epoxy: The rivets on the inside have been compressed with Mole Grips to avoid interference as far as possible with the Dzus fitting for the nosecone It doesn’t look too bad with the extra rivets:

That was my aim yesterday which seemed to be achieved, with full verification next weekend on the track. Entered with very good mid range, paid virtually no attention to it during tuning as the first run showed little change needed. Was all about the top end (ensuring safety of mixture under high load), bottom end from low revs with high throttle (Caterham is too light to get meaningful readings from road logging) and playing with the timing to get it to the right position.

From some of the info put out by Dynojet, the manufacturers of the rolling road I used yesterday, I can see why they don't give the tools to convert to crank horsepower and why they emphasise wheel horsepower measurement: https://www.dynojet.com/blog/whp-or-chp-which-should-you-trust/. They also tend to lease the rolling roads to the operators and provide the calibration and maintenance services to keep them in good order, discouraging them from doing any adjustments. Mitch, the RCTS owner, says that they don't provide any documentation on re-calibration, just setting the system up for the local atmospheric conditions and checking accuracy during scheduled maintenance.

The graph from the rolling road: Values are measured wheel horsepower and torque corrected to sea-level values, compared with the rolling road altitude of 1050m / 3,400ft. I'm very pleased that we got the AFR / Lambda value so close to a straight line across the whole range, with it slightly decreasing to the torque and power peaks. The actual revs measured may be slightly lagging on the dyno, as we did hit the rev limiter at 8200RPM, so peak power is effectively at the redline. The torque peaks are influenced by the throttle body resonances, likely 5th harmonic lifting the higher torque peak and 7th harmonic lifting the lower torque peak. The revs reached at throttle cut on the Easimap plot show 8202RPM, with Lambda just where I wanted it to be for safe operation. Applying a 20% drivetrain loss factor in 4th gear to the wheel measurements lead to 255bhp at nominally 8200RPM and 188lbft of torque at 6500RPM, compared with the quoted 263bhp@8500RPM and 176lbft@7165 for an "official" R500, so I think it is close enough to job done to call it an R500A!

Hi John, We are lucky here that the number plates can be chosen for about $200 as long as it is no more than 7 characters, doesn't have a reserved name or special format used by, for example, the Government and has no offensive words or connotations. It is a pity that we can't have 8 characters, so I had to go with Caterum instead of Caterham, but it does cause the North Americans to pronounce the name close to correctly, instead of the normal emphasis they would have on the 'ham' part of the name!

Dyno Day at RCTS Autoworx was successful today, 7 hours of setup and tuning to cover all but cold starting. I was going to try and log a cold start as it was sleeting and -1C when I got to the rollers, but needed to get the car inside instead of trying to log info while the laptop was getting wet. The car starts and idles well at 10C and above, but needs throttle and coaxing at 0C for a minute or so. Initially I was disappointed with the engine output, but they are geared towards measuring wheel horsepower at sea level (rollers are at 1050m altitude). They dynoed a Hellcat with a quoted 717 crank horsepower last week and measured 594bhp. They measured just over 212bhp on my car, that would equate to 256bhp at just under 8000RPM with a similar ratio as the Hellcat, right were I was hoping to be, if that is the case. Just waiting for them to email me the Dynojet plot. Here is the full throttle run once the mapping was generally complete: A few other photos of the rolling road setup. Without the nosecone and bonnet on, coolant temps hit 100C and needed a cooldown in extended sessions. With the nosecone and bonnet in place the normal 90C was seen during extended sessions. We spent a couple of hours investigating a couple of issues. The first was that the dynamometer Lambda sensor only agreed with the wideband sensor in my exhaust at medium loads and was about 0.08 different at high loads and 0.10 different at low loads. Due to the inflexible probe inserted into the exhaust, it only makes it to the bend, we concluded by reviewing plugs, smell and peak power when nudging fuel up and down that the exhaust collector was allowing reverse flow to cause the dyno probe to give false readings, tuning was much more predictable using my wideband sensor. The second problem was my knock sensor system kept activating around 6500RPM (it used to do this at about 7200RPM with the plenum). We pulled timing by 4 degrees and it still activated at the same point, pushed timing up a degree and power increased 3bhp, another degree and didn’t increase at all. We concluded that after multiple inspections of the plugs with a loupe that there was no detonation, the knock sensor filter is just picking up mechanical noise at a slightly lower RPM than before, probably the more aggressive cams and throttle bodies to blame. Lots of maps saved from different scenarios and logging to match them, so I can go back and look for any anomalies that we may have missed during the session. I’ve also now settled on 1200RPM for idle due to the sound through the throttle bodies being very tappety at 1000RPM, almost like a valve is about to drop into the engine - gave me flashbacks of the original engine failure 😀 The proof of how good the engine is now will be in the first track day on 12th May.

M15M-D is the Mazda transmission type, M53F-03-000 is the Mazda part number for that transmission. Here is a link to a manual for it: https://www.mellens.net/mazda/Mazda-Miata-2005/manual_transmission_5spd.pdf

Half a degree rotation of the TPS correlates to about 0.02V, about the amount of adjustment needed to even out the idle somewhat. That is only about 0.2mm of slack in the clamping hole. In adjusting the throttle stop screw, 30 degrees or so of rotation is the likely amount of adjustment that would be needed to change the air flow by an appropriate amount.

With the manufacturing tolerances in each engine, the idle will never be very good without careful adjustment for each engine without an idle control system. This means that the engine would need to be run at the factory in the car with the same fuel pump and air intake. Obviously with a self-build model this is not possible. An adjustment in the throttle blade position of 0.05mm makes a significant difference to the idle. The engine map at idle really needs to be specifically set up for the car, which isn’t going to be possible with a standard engine map in a locked ECU on an engine that isn’t running in it’s final fitted configuration. When fully warmed up some basic idle control is provided by closed loop Lambda control, but with the narrow band sensor used, hunting should be expected if the mixture in the map is not close to the needed amount. Throttle stop adjustment may work on some engines, but the tolerances overall may be too much to get it close enough without an ECU remap.

I’ve had plated bolts corrode before when using washing-up liquid to ease rubber installation, sodium chloride and citric acid are some of the common ingredients in it. I usually use a rubber lubricant.

Hi Jonathan, It isn't the Brise starter, it is the standard compact one from Caterham, but I can't remember the manufacturer and the sticker is difficult to see with it installed. The ECU has no problem, it shouldn't drop-out unless the voltage drops below 5V for 100ms or so. The sampling interval on the MBE ECU is 83ms, so it typically will capture transients down to about half the sampling interval, or about 40ms. The inrush voltage dropping in to the 7V range for tens of milliseconds is normal, though. Standard car starters can hit 500-1000A briefly. Effectively the battery is short-circuited and the current is only limited by the battery resistance until the motor is fully energised as the motor turns and the stator and rotor windings have opposing voltages established, it then draws of the order of 200A while cranking. A new battery will potentially show a lower voltage than a more "mature" battery that is still in perfect condition, as the internal resistance is lower, so the initial current spike is higher. My 8.5V drop captured with ECU logging is fairly consistent and normal from my review of recent Easimap logs, but if I put my Hantek USB oscilloscope on it, I would expect a bit more of a drop captured due to it's higher sampling rate.

With a brand new battery that has been charged to full capacity before use, the initial voltage before start on my Duratec drops to 8.5V for 80ms, before cranking at 10.5V before starting. The ECU logging captures this, but it is a bit quick to see on a voltmeter.

The recommended tyre temp range of 60C-90C hot would give a cold pressure range at sea level and 20C ambient of 15PSI cold for 90C at 22PSI hot to 22PSI cold for 60C and 27PSI hot.

The repositioning of the air temp sensor worked well. When it was in the backing plate it would be about 45C above ambient with the car idling for 10mins or so, then only slowly drop to 30C above ambient while driving with the engine up to temperature. Moving the sensor so it is actually outside the bonnet but inside the filter protrusion next to the trumpet bellmouth, dropped the temp to 30C above ambient for an extended idle with an up-to-temperature engine, but it drops to about 18C above ambient after a couple of minutes of driving. I think the value now it is quite representative of the average air temperature in the throttle body inlet tract.

I agree with Peter on this, entirely normal based on not just the Caterham, but any non-synchro gear in a car gearbox. If the input shaft is still spinning due to just having moved the car forward, a grind is possible. It also can vary with oil temperature and viscocity which can affect when the shaft stops spinning.

Last weekend when doing the throttle body balancing and adjustment, I noticed the air temp data showed it rising to 60C due to the proximity of the air filter backing plate to the engine. Even with rubber isolation washers and 30 mins of driving around, the temp only dropped down to 48C. I decided today not to be lazy about sorting a better location for the sensor, especially with more mapping and the rolling road session coming up, I want as accurate temperature input as I can get. I picked up some PVC threaded 1” water pipe fittings, machined them to make a suitable stand-off tube and cut a 32mm hole in the air filter backplate: The end plugs were drilled, the one that was shortened for the sensor end, the other slotted to pass the cable through with the minitimer connector left in place. The main body was enlarged inside to allow space for the connector and a spacer was created to optimize the distance from the backing plate: The position is very close to the trumpet inlet, but not too close to affect the bellmouth flow: The PVC should provide good thermal isolation: I’ve recalibrated by Lambda system, updated the maps from data logged last week and fuel data provided by Neil from his engine, created a new target Lambda map that should be close to the needs of this engine and switched on adaptive Lambda. Hopefully I will get at least 200km of moderate load running-in tomorrow to populate the adaptive maps, then more analysis, followed by another few hundred km over the next week or so, before another oil change to synthetic 5w50 for the rolling road session.

The main thing is not to put balance weights close to the inside edge of the rear wheel barrel if your wheel width is such that the deDion ears are inside the wheel. 8" wide wheels certainly have the problem. I normally put 40mm or so wide painters tape around the inside of the barrel in that area with "no weights here" written on it.

Thanks for the emails Neil, I was going to compare them with my logged data tomorrow. The weather would be good for putting some running in km on the car tomorrow, but I don’t want to rush the analysis and also promised that SWMBO and I would go out somewhere, too (but not in the car!). I’m currently set for sequential injection once cam sync is achieved, batch (paired) before sync when the engine starts.

Hi Neil, I can do adaptive tuning with the MBE, but I need to determine if the new Lambda sensor is giving correct results first. I do have a cam sensor fitted, haven’t checked the data yet to see if cam sync was achieved on target.

Still lots of mapping adjustments to do, also need to determine if my new Lambda sensor is faulty as it would suddenly go from rich to maximum lean, but I could still smell excess fuel. Only one small leak requiring the clip on the main hose at the back of the head to be tightened more. After the first start I shut the engine down quickly from what I thought was excessive top-end noise, but it turned out the throttle bodies allow quite a banging noise out of the intake at low throttle openings, probably due to the late valve closing. Took about 5 brief runs for about 20 seconds at a time to fiddle around with the throttle mapping at sites 0 and 1, as it would not rev initially due to being either too rich or lean just off idle. Did the 20 minute initial cam and ring running-in as specified by the manufacturers, then did all the throttle air-flow balancing (only needed to use th3 bleed screw on #4 to make 0.5kg/hr adjustment, setting all to 9kg/hr after setting mechanical idle at 1,200RPM, then re-activating ECU controlled idle to 1,000RPM. Did a 6km brief drive to log some data with medium load up to 4,500RPM. Did the first oil change and cut the oil filter open, a few bits of old RTV debris and tiny specks of what looked to be machining debris. Probably the amount expected, typically like this every couple of filter pleats: The finger filter also trapped a few bits of larger debris: Overall on track, need to have a look at the logs and make adjustments before more road use and the upcoming rolling road session.