aerobod - near CYYC

There is no ECU reset on the MBE 9A4 that will affect the idle at cold start or change the TPS calibration. The TPS has a very small adjustment within the mounting holes that could affect it. Without Easimap to view the voltage and throttle site, you could slacken the screws just enough to move the TPS, start the engine, then rotate it within the holes to see if the idle improves in any position, then re tighten the screws in the best position.

Also, best to use a brake cable as opposed to a dérailleur cable, as it is generally a heavier gauge cable.

I ordered a Setrab 19-row Series-6 oil cooler with -12 fittings, the Mocal 19-row -12 ones seem to be back ordered in general. It is interesting that most of the Mocal and Setrab coolers are interchangeable with dimensions and rows being the same down to the millimetre, so the feed hoses will fit exactly the same as the current cooler. With it being taller than the 10-row one and the top needing to be higher, I will probably make some mounting blocks that locate on the existing Caterham brackets, to support both the top and bottom flanges. I have decided that I won't put in a thermostat for now, as that will mean 4 new feed hoses. If it over cools for road use, I will just blank off part or the whole of the cooler.

Ballast will affect the camber quite a bit, the toe to a lesser extent. You can us a long straight pole to gauge the difference in toe on each side by using 2 axle stands to rest the pole on at hub centre height, then when held a fixed distance from the wheel face (using a couple of spacers), measure the position relative to the rear wheel, or just sight along the edge of a long spirit level to a mark at the rear wheel. I f the steering wheel is off when the car is driven, just adjust the track rod an equal amount each side to centre it.

Hi Neil, I think I will go with a 19-row Setrab oil cooler and oil thermostat as the next fix, although mounting the thermostat will require some re-plumbing of the oil lines. For the next track day in 2 weeks, I will take along the old pulley and see what swapping to it does. I want to try and keep the oil pressure at 5.0bar and above at high revs in all temperature conditions. When is your first track day with the new engine?

The engine performed very well for my first track day of the year, today. Best described as an “angry bee” from a noise and responsiveness perspective. Only one problem I have to solve is that I need more oil cooling. With the old 210bhp Duratec with plenum, track use would typically see coolant at 80C, 5w50 oil at 5.5bar at higher RPMs and just over 2 bar at idle after coming off the track. Bulk oil temperature in the oil tank would be 80C (likely about 20C below dry sump temp). With the new engine after several flat-out laps, oil temp would quickly rise to 90C in the oil tank and pressure would drop to about 4bar at higher revs, I briefly saw 100C in the oil tank and an idle pressure of 1.8bar after coming into the paddock. Coolant temp would also be 90C or so at high speed. I ended up running flat out for the beginning of each session, then keeping it to 6000RPM or so and using 4/5th gears instead of 3/4/5, but my speeds and lap times together with oil and coolant temps were than back to the same as with the old engine. I had put a 12% lower speed water pump pulley in to avoid cavitation at high revs, but may put the standard pulley back in. I think in addition to that, both a larger oil cooler and 10w60 oil may be needed.

SWMBO had a good laugh at my expense a couple of weeks ago when she had to dig around with a pair of tweezers in my ear to extract an ear plug which was inserted just a bit too far.

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.