MH7 SCS-Delta Engine Management and Hybrid Turbo

 

TL;DR +32bhp, about 140 €/bhp, worth every penny

That project was a long time coming since I did contact MH7 on May 2nd to talk about the idea of tuning my engine a bit. I had recently met MH7 at HoS, and he was also present at the Spa-Francorchamps track day in March. For a while, the MH7 Engineering contact page did even show a picture of that event, with my Caterham parked just next to the MH7-branded trailer and the Raidillon in the background. 

While flashing the OEM EFI ECU could certainly be done, it would be very fiddly and would require soldering thin wires to the circuit board. On top of that, it wouldn't offer the same kind of versatility an upgrade to a proper high performance engine management solution would provide. With the advice of SCS-Delta, the best solution would be to use their 700S in combination with a bigger turbo. The upgrade could even be done in two steps.

Not willing to push anything too fast, expert advice was gathered, and we landed on the idea of a hybrid turbo, rather than a replacement one. A hybrid turbo is just one that has been machined and had its internals replaced with a bigger compressor wheel and/or bigger turbine. We would retain the original IHI turbo but have it enhanced.

On the hardware side, the ECU upgrade is plug&play with a professionally made wiring loom connecting to the car without any modification of the engine or dashboard wiring. As for software, SCS-Delta would provide an existing Caterham 160 map as a base (I suspect it's the one from the 95bhp K6A-based Supersprint but have no proof of that), and MH7 would tune it to my newer R06A engine.

The car was picked-up on Nov 26th, and was running with the 700S ECU by the end of that week. All was easy-peasy with the engine, but less so with the fuel gauge and fuel pump that needed some debugging. Although not measured on the dyno, the handling improvement was already excellent; the ECU logging highlighted how the turbo was struggling at high RPM. Confirming that modifying it should bring a lot. 

Although not directly related, a custom-made air guide was built and fitted in front of the intercooler. It will scoop fresh air from the nose grille and improve the flow; it can do no harm. Talking with the Caterham CEO and their Suzuki expert, they were not impressed with the idea though. We were discussing the 620R nosecone on the 485FE in the delivery area at the factory (I find that the grilles over the oil pot and expansion bottle are pointless and ugly...), and I mentioned it made more sense on the 170R delivered to Caterham Deutschland very recently. They told me that even around the intercooler of the 170 it was just a cosmetic thing that shouldn't add much. My own impression is that the intercooler is rather large for such a small engine; and doesn't need any help.

As MH7 told me we could add a switch to choose whether or not I wanted some pop and bangs in the exhaust when downshifting, I hinted on having 2 different maps altogether. That's how we agreed on a "sport" mode with all the pops, bangs and boost better used with RON 98 fuel, and a more gentle "fuel economy" mode aimed at the flattest torque with RON 95.

After that, the turbo was removed from the car and entrusted to ASD Performance for modification. It was during the Christmas holidays, and there was some back and forth to decide how large the compressor wheel and turbine should be.

The upgrade consists of a full Stage 3 hybrid turbo, including machining of the compressor and turbine housings, featuring +5mm increase on the compressor wheel, and a more complex +5mm nose / +2mm base increase on the turbine that had to be customized. This in order to limit the inertia and lag as we did suspect that more would have been too much and would have required to limit the engine power electronically, just adding lag.

At only 20mm, my turbo is probably the smallest thing they have ever worked on. But what kind on conversion can add 25% on the compressor and 10% on the turbine ? 

If my understanding is correct, the potential improvement of the compressor relates to its +56% increase in surface area. At the same time the turbine reaches +21%, that will also let exhaust gas flow more easily, improving efficiency.

The upgraded turbo came back during the second work week of January and was fitted soon after, with some adjustment of the ECU map, and a very good feeling when driving the car.

From the factory, the car is advertised at 84 bhp and 116 Nm of torque. After final adjustment on the dyno, the "sport" map (blue on the chart below) gives 116 PS (+38%) with 135Nm (+16%) while the "economy" map (red on the chart) reaches 106 PS (+26%) with 119Nm (+2%) on a much wider engine range than originally. Note that PS is just german for BHP, if you don't mind being 1% off.

The economy mode is a achieved by keeping the boost pressure at 2 bar (absolute) and still manages to top the original torque thanks to the improved flow of the exhaust through the larger turbine and machined turbo housing. The sport mode is able to provide the OEM 2.24 bar way up the revs, instead of miserably getting out of breath at 5500 RPM.

Limits in boost, RPM, spark and injection timings were set based on how the engine was behaving, and what felt right and safe. The goal is to keep it reliable and Euro-6 compliant. We didn't touch the catalytic converter, which is stock Suzuki. 

See below a video of a dyno session. In the 100 hp terrirory, that's really nothing to write home about, we are far from the projects that usually touch those rollers. The belgian Caterham world is niche enough that the Instagram publication of that same video by MH7 appeared on the feed of a friend, although he didn't follow MH7 yet.

If we really must talk about money, you'd be right to think that's a lot of cash for 32bhp. Last time I did add 32hp to a car, it didn't cost me 140€ to push my 2.0 CDTI MG ZT-T up to 172hp with a torque reaching 420Nm. Here the total cost is around 140€ per additional hp.

The best alternative to consider is a ~1500€ offer from House Of Speed, that would give you between a third to a half of the power increase for a third of the price. The original EFI ECU is re-mapped by a reputable company near Liège, they fit an air guide to the intercooler, and a heat shield between the turbo and air intake duct. Contact them if you are interested in that 95-98hp mod.

Various websites also show the Caterham 170 on the list of cars they are allegedly able to remap. For half of what HoS asks, you get half the power increase (+9 hp), and I don't believe in the advertised torque as I cannot see them reach anything near what we got on mine, or maybe on a very narrow band. You should also consider that if it does not end well, a new EFI ECU will cost you 1000€.

Reaching 176 PS/liter is nothing short of ludicrous, as that's on par with a McLaren 720S. In such a featherweight 460kg car, we are talking 250 hp/tonne. Which is the same figure as a Caterham 275 that with 135hp and 540kg (1596cc Ford Sigma engine). As the "torque/tonne" would also very similar at 293Nm/t vs 305Nm/t, there is no reason not to expect the 0-100kph to stay just below 5 seconds. That thing will eat any GTI for breakfast. 

For the fun of it, let's get over our heads and see how maths say my car should be able to smash a Caterham 620R at the red light. While the 620 sports 297Nm and 310hp, it's a heavier machine at 610kg -figures per tonne are 486Nm and 508bhp-.
The gearbox ratios and final drive should give some crazy mechanical advantage to the small Suzuki.
In 1st gear, the 170 has a ratio of 1:20, while the 620R with the 6 speed sequential has a ratio of 1:7.5. That's a 2.66 advantage plus 2% due to the larger diameter of the 13" tyres, so 2.7 overall.
Scaling-up my upgraded 170S with that drive ratio gives us 791Nm and 675bhp /ton-equivalents in 1st gear. Shifting up to 2nd gear I still get a 1.6 advantage against the 620R that will reach 100kph in 1st gear, making for 470Nm 400bhp /ton-equivalents. That a 3% disadvantage in torque and 22% disadvantage in power. All in all even the mighty 620R cannot touch me when I lift-off like a rubber band After that, things would get interesting as I would be left laughing manically in the dust.

While not that fast, it will definitely be quick.

DISCLAIMER : Do not try this at home. Not only you will lose you warranty by breaking the Caterham wire seal that proves the turbo has not been tampered with and the engine kept closed, but there are also serious reliability concerns. R06A engines are not as robust as the former K6A, and shouldn't be pushed too far. While I'm confident all will be fine with mine, I won't race it, I won't push it for too long over straight stretches (even though the temperature of the exhaust if monitored with the lambda sensor and is managed with richness adjustment), and I will continue to change the oil every 5000km.

If you decide to go for it - and I think you should - send a message to MH7.