A bit of history (part 12) – Natural expirations

Success- the new engine runs!! It had taken a few long evenings after work, but was totally worth it when she fired up! I was nervous when it didn’t start on the button, but a flick of the throttle and away it went. Next up was bleeding the coolant system, and dialing in the mechanical ignition timing, which I went slightly aggressive on in anticipation of running super unleaded (aiming to squeeze every fraction of a bhp out of the engine).

Onto running the new engine in, and initially I had problems with a high idle speed, and a propensity to stop altogether once hot and trying to idle…but a second hand idle control valve sorted these issues, and I continued with the process…however…

…the more I drove it, the more smoke I was getting out of the exhaust, primarily with the engine loaded up. Compression was spot on (well actually better than expected thanks to the Total Seal top rings)…so could it be valve stem seals or piston rings? Hard to explain with the high compression results.

Anyhow- I ended up swapping in the other cylinder head I had (with the engine in the car, a painful job to do single handed), and sure enough- the symptoms remained…I must have a bottom end issue here. I inspected the head and noticed that some scoring had developed on the cam bearing surfaces, the worst being on number four inlet cam, then progressively less on each journal running up the engine…joy, I had obviously missed some detritus in the oilways when I cleaned the block despite my over the top attention to detail!

So I pulled the whole engine and ripped it apart, just in time to save the second head…phew! A full inspection revealed that the oil control rings didn’t seem to be doing their job, which I double checked with Tony G. This at least explained the decent compression (as the top and second rings were spot on), I’m guessing my inexperience meant I hadn’t realised they were out of spec- although I’m sure I checked!!

After this I was pretty down on my abilities to get the exacting specifications of an engine build 100% correct, and especially my ability to get the oil system fully cleaned up given the facilities in my workshop. Luckily Tony offered to help me out, and fully cleaned and assembled the bottom end with new oil control rings for me, he even looked over several cylinder heads I had and helped me choose the best combination of parts to build up. We ended up swapping in a fresh set of big end bearings at the same time as Tony had noted some wear in them, presumably related to the debris I had missed.

Forward wind a little bit and I had the freshly rebuilt engine back in the car, and this time opted to run it in on the dyno- I was keen to get the car back on the road, and I was starting to understand the benefits of running engines in in this manner after my experiences with the Turbo car. The car ran beautifully, with only a couple of niggles- the rear brakes were dragging slightly (they were smoking hot when we took it off the dyno!), and one of the driveshaft oil seals was weeping.

We ran it with the ACIS connected and disconnected, which shows the two plots on the dyno graph…it was an eye opener to see in action the impact of this system, and I was left thinking about how you may gain more torque by raising the limit at which it opens up- you can see the power curve flat lines as it does…it strikes me you could avoid this.

I remember being very happy with the recorded power levels, again applying our 15% transmission loss assumption to these at the wheel figures…and considering the rear brakes were dragging…very healthy.

[What is ACIS?

This is Toyota’s Acoustic Control Induction System, which basically changes the volume of the intake manifold in order to try and maximise torque/ power. At lower revs the inlet manifold volume is reduced through use of butterfly valves, and at around 5k rpm the volume is increased.

The changes in volume effect the peak torque the engine can produce based on the resonance of gas pulses back from the opening and closing off the inlet valves.]

Back at home I realised the brakes issue was an installation error on my part, easily rectified and the car was once again track ready! And sure enough, just in time to head back to Anglesey with the MR2 owners club…

I had tweaked my suspension settings in advance, and had gone far more aggressive- which really seemed to pay off on track- the car was turning in super sharp, with nice predictable over steer that could be controlled with the throttle through the corners. However I was eating up the outer edge of my tyres, so I dialled in more negative camber and adjusted the anti-roll bar settings front and rear, which had led to the car washing out a bit more once into the corners, but it still felt very grippy in the faster corners- and the tyres were far happier.

The new exhaust was obviously doing it’s job- the other MR2 owners at the day were convinced I had a v6 in the back, not the lowly 3SGE engine…happy days!

I think on of the most notable features of the car (and the one passengers commented on most) was the braking…I’ve never driven a car that you could brake so late into corners with, the stopping ability was incredible.

This was due to the lack of weight in the car, coupled with fully serviced stock brakes and Carbotech’s XP8 pads that had been properly bedded in. I know folk slate the MR2 brake caliper design, but honestly- I was up there with most cars that day simply by being able to catch the faster cars in the braking zone…well except for the “real racing” cars of course (like the Atom my friend scrounged a ride in)!

I did continue to play with the car after this, and really enjoyed experimenting with different suspension settings. I managed a few more trackdays, and plenty of road driving. I don’t think I’ve ever crashed a car as much as this one, albeit I never hit another car, and the crashes were generally at very low speeds…I did tend to head out in the worst conditions I could find, such as fresh snow on untreated roads, and then really test the car on the limit of its grip.

I remember a 360 spin into a farmers gate at about 3mph when I’d not been able to correct deliberately induced oversteer in the snow, as well as a 1-2mph head on into a gate on our driveway when I had fully locked up and couldn’t get any traction back again- I recall being highly amused as I very slowly drifted into the gate with absolutely no control.

Happy days…and fond memories, it was a great little car. But eventually its time came, I simply couldn’t justify paying insurance and road tax for two highly impractical cars when I was barely driving both of them for most of the year.

I had also achieved what I set out to do: I had gained a huge amount of knowledge and experience about the mechanical side of MR2s, and I had certainly taught myself a load about how they drive (and handle on the limits of grip).

So a new plan was hatched, now I had taken full ownership and control over the Turbo MR2, I wanted to get it to handle and stop as well as this car…but with the higher power levels. Time to take the best bit of both projects, and put them together to make one awesome car!

I parted out the bits I didn’t need and sold them off, including the engine (which went into an MR2 Championship car who instantly started placing further up the running order)…and the shell (which was suffering from tin worm, the winter driving experiences had not been kind to it) was cut up for scrap…

So long my naturally aspirated amigo, it was a blast!!