Monoposto Fuel Injection Project
Tristan Cliffe spills the beans about the first non-F3 injection Dallara to run in Mono (or not, if you were at Brands)
The topic of fuel injection in Mono2000 was first talked about as a serious possibility during 2008, at which time we were busy wrapping up the Classic2000 championship in the Reynard, and trying to buy a Dallara to take the fight to the very front of the grid. In fact, its legality was one of the factors that made us choose to change to the Dallara, as all the stuff could be fitted from the start, rather than having to, as now, convert from carburettors to injection.
It was at this time that we began phoning, emailing and visiting various suppliers of ECUs and throttle bodies, with a particular emphasis on ‘local’ companies, as well as the usual suspects of Omex, DTA, Jenvey etc. At the time we weren’t sure what the regulations would entail, so everything had to be kept very vague, but we ended up with an initial choice of system, should the go-ahead be given for 2009.
Of course, it wasn’t. As such a pair of Dell’Orto carbs was bolted onto the engine, with the requisite low pressure pumps and ignition-only ECU, but we kept talking to Russ and Nick about what might happen in 2010. Our intention to change was strengthened by initially suffering fuelling problems on the carbs in “high-G” corners – Coram at Snetterton, Gerrards at Mallory – that were costing us measurable and significant chunks of lap time. Indeed, by the time we sorted it overnight at Mallory, we found over a second of lap time!
Still the behind-the-scenes discussions continued, with other competitors becoming more and more anxious to know what was going to happen, until eventually the go-ahead was given. Injection was to be legal in 2010 subject to a few regulations to control power and maintain a degree of parity with existing carburetted engines. Towards the end of the season Martin approached our main rivals – Nick Harrison and Jeremy Timms and discussed the possibility of a Gentleman’s Agreement not to convert, as it would just cost us money with no real change in the status-quo. But with more and more people thinking of getting Dallaras, and no doubt some of them choosing injection, plus F3 engines being allowed in (on larger-than-2009 restrictors), as well as potential arrivals from Formula 4 and Formula Renault 2000 cars we decided that converting would be a necessary thing to ensure competitiveness. I just hope that Clan Harrison and Timms aren’t too upset with us for reneging on that agreement in principle…
Before the season was over we had begun to approach people again, this time spending more time talking about the money aspect than any pipedreams we may have had. Obviously we wanted to get as much of an advantage, for as little money, as we could within the regulations. A set of Jenvey throttle bodies was discounted on the basis that they aren’t very nice, and didn’t seem that bothered – an attitude of bigger companies that isn’t very surprising. However, a local company of ex-Lotus employees called Active Technologies had begun producing throttle bodies, and they were keen to help us out (not least because Martin hired one of them when he was at Lotus). The downside was the regulations – we had to have no more than 40mm diameter throttles (or tracts upstream of the throttles in the case of non-round throttle plates). Active Technologies produced a 38mm version and a 42mm version. The 42mm version is very popular (e.g. with 2.0l Duratec engines), and although we could have put a small venturi section in to satisfy the 40mm rule, there was quite a price premium because they can easily sell every one they make. The 38mm version was in far less demand, but would 38mm be enough to maintain the power outputs of our existing engine?
Our 2009 engine on 48mm Dell’Ortos had a rolling-road peak power figure of 185hp (estimated due to it being a very optimistic rolling road with little or no correction factors). Funnily enough, our Reynard on 45mm Dell’Ortos also had a peak power figure of about 185hp on the same rolling road! Active Technologies were fairly certain we get more on their 38mm bodies, and that 42mm (reduced to 40mm) wouldn’t give anything extra. Who would be right?!
Active Technologies (or AT Power as they call their throttle body division) then put us in touch with another local firm, Specialist Components, who have made and marketed their own ECU. We had also considered an Emerald ECU (again, quite local to us), but the link to AT Power gave Specialist the nod. They are also ex-Lotus people, were keen to get us going, and discussed all sorts of interesting ideas with us.
The first process was to get a throttle body to fit our engine. The 3S-GE Revision 3 Toyota isn’t that widely used, so there wasn’t a Direct-to-Head option offered. But we didn’t want to use
a Weber/Dell’Orto replacement style manifold as the inlet tracts then end up a bit longer than ideal. The end result (write this down if you’ve got a S-GE Revision 3 and want to use throttle bodies) was to use a 38mm Duratec Direct-to-Head throttle body, and a short adaptor/manifold to convert the port shapes and spacings to that of the Toyota. This was made in double quick time by AT Power, and included injector ports rather than using the standard ones in the head.
Whilst we had to commit to having that manifold made, there was little option, as we wanted to confirm the choice as being correct. This was done by taking a spare cylinder head (with valves), the carburettors, the throttle bodies and the relevant manifolds to Scholar engines for an airflow test. Comparing the 38 bodies to the 48 carbs showed either the same or better flow rates with the throttle bodies – perhaps AT Power would be right after all.
The next step was to get the engine over to Damico Engines, based behind Snetterton. They agreed to put our engine on their dyno, get power curves with carbs and throttle bodies, as well as a variety of trumpet lengths, and with and without our airbox. At the same time we decided to get the Specialist Components ECU mapped, as everyone was fairly confident after the airflow tests. The results were that the AT Power 38mm throttle bodies increased out power and torque by roughly 5% at high revs, and about 2% at low revs. In addition it’s likely that the response of the engine will increase, especially at lower revs, although that isn’t something one can see on dyno reports. The 42mm throttle bodies added even more, but with a slight reduction in mid range torque.
Whilst the peak figures don’t show much variation with trumpet length, the shape of the curves vary significantly, to the point where I’d be tempted to design and make a variable length trumpet system for 2011 even though (or perhaps because) it would be hellishly complicated. Also, we were only running a single injector per cylinder, but I would put money on a gain of between 5-10hp being found with a second injector into the trumpets, which isn’t insignificant. You’ll be pleased to know that the Monoposto Racing Club welcomes a horsepower race, as these avenues have not been made illegal. With enough money a 210+hp Mono2000 legal ‘standard road’ engine should be possible.
Of course, we were quite pleased to be able to show AT Power that the larger throttle bodies would have given us even more power, but we were constrained by empty wallets and an ECU map done for the 38s. It’ll have to do, and we’ll keep our fingers crossed that nobody goes that extra [costly] mile.
The next thing to do was to convert the rest of the car for fuel injection. The fuel system was modified to accept a high-pressure pump (most of that work had already been done in 2008, but removed when we had to use carburettors, so not too hard), whilst pressure regulators, and fuel return hoses were added to complete the loop. There were also significant changes to the wiring needed, not only because we were changing from Omex to a Specialist Components ECU, but also because the injectors needed to be powered and controlled, which has meant pretty the whole loom from the monocoque backwards has had to be redone from scratch (we have also taken the opportunity to fit a much bigger battery, due to running out of sparks far too frequently in 2009).
Once everything was fitted, which was done around the annual rebuild and checkover, the car started first time and ran quite sweetly. Once the throttles were balanced at both idle and full throttle, and things like throttle position and crankshaft position sensors were calibrated it ran sweeter still. However, there is only so much you can tell with the engine under no load, so we won’t know if everything is perfect until the car hits the track.
I’m writing this bit after our first (and only?) test session of
the year, held at Snetterton on the 12th March. We had a few problems
– one, another broken throttle cable, was down to bad luck, whilst
the other was a loose earth connection and was clearly our fault. But
for the most part, the car ran well.
Other factors to consider are noise and cooling – with injection our car seems to be louder than before (although that might be down to my silencer repacking [lack of] skills), so noise testing might become a nervous time, and the exhaust temperatures appear to be a lot higher, so we’ll have to keep an eye on bodywork, suspension members and carbon wings for signs of heat damage – not a problem if your exhaust exits from the back of the car, but it might be if you’ve hidden it in the sidepod.
But one test session does not a season make – as Shakespeare would have famously written if he were a motorsport fan – so you’ll just have to keep an eye on us, and the other injection cars, to see how we get on. With the influx of Dallaras into Monoposto, the front of the Mono2000 grid could be a very competitive place, and more punishing of mistakes. Last year if I had a bad practice session I was still in with a good chance of being 3rd on the grid. In 2010 the same poor session could see me languishing in 10th! But surely that just adds to the fun?
CODA - Brands
Whilst we haven't done a complete investigation yet, we don't believe
that the fuel injection system was the cause of the failure to start on
Sunday afternoon. We believe, based on the discovered symptoms,
that it is ultimately down to the internal failure of the starter motor
- resulting in voltage/current being converted efficiently to smoke. This
probably caused a current leak that starved the ECU/fuel pumps/injectors
of the correct voltage to achieve a nice idle even after a push start
(although it actually seemed to be fine under load during the 2 second
full throttle run in the paddock).
Photos: Andrew Cliffe & (Brands) Simon Davey