Project/Build Thread- Making a tiny 659cc car fast
This isn't exactly how I wanted to write this as it's all at once and not all of what I wanted to include, but here we go anyhow. Hopefully this guides some people how to tune these things, as the info out there is vague to say the least lol.
Earlier this year after selling my JZX110 I had some money burning a hole in my pocket, and for no reason other than I like experimenting with tuning different things, I bought the blue Mira Classic Superspat had for sale on here, this one...
I bought it sight unseen, in the middle of the night, about 150 miles from home, but it was as described really, so job done there. It came with an aftermarket exhaust, K&N panel filter, and most usefully, KYB uprated suspension. Aside from that, it was stock.
As I guess you all know, these have the 659cc 3cyl 12V turbo engine and 4wd, 64bhp standard.
The journey home was interesting to say the least, all windy undulating A-roads, in the pitch black, with awful headlights, and cracked winter tyres, so 50mph felt like 100mph in any other car, and 70mph (which is 5000rpm in 5th and about as fast as it wanted to go) felt like 130mph+.
It was slow, it looked ridiculous, even HGVs went in to the outside lane thinking they could overtake me any time they spotted me, but I could see the potential at least.
First job was a front mount intercooler...
Due to the chassis rail position, despite there being room for a flippin massive intercooler, there'd be zero room for pipes, but you can still have a pretty massive (and 3in thick) one, with a bit of effort.
Needed quite a lot of careful measuring and a lot of silicone hose buying, but it worked out nicely.
You need to do a bit of hammering to get it past the radiator on the one side, but barring that it was no problem.
At the same time I knocked up an induction kit using the stock airbox, and made an oil catch tank setup using a spare one I had hanging around which originally was on a RX7 D1 car I imported.
Needed a little trimming of the front bumper too as the intercooler was so big, but it then looked like this...
The result was a much quicker car, no less responsive, maybe more so, but pulled much stronger, and seemed to die out at high rpm less too.
Next up was the exhaust, which was some kind of bodge job that exhaust 'experts' Powerflow had made, and as they're clueless retards they'd clearly made it with the wheels off the ground, so suspension at full extension.
The exhaust they made is an over axle one, but this means even when the wheels are on the ground it touches the rear axle and vibrates like hell, and on hard acceleration or over any kind of bump it jams against the rear axle, not only making an awful noise, but stops the suspension working, making the thing handle like shit.
The simple solution to this was make an under-axle setup, which I did. This fixed the rubbing problem, and as these cars are far from low it made no issue on speed bumps.
One thing that was doing my head in was it looked ridiculous. I knew it was never going to look good, but all the chrome plastic trim was proper try-hard, made worse by the tints, everyone used to stare at it, and not in a good way, and I wanted it to be far more anonymous, and far less ridiculous, so I broke out the satin black paint, and added some 0.6L badges so people really knew how 'slow' it is. While I was at it I fitted some 175/50x13 tyres to replace the old, cracked, balloon snow tyres the thing had. And the result is this...
(also note the FCD2 mounted behind where the glovebox used to be)
The difference the weight loss made was huge, far more than all the other mods so far, and the handling was transformed too, from a mix of the weight and finally having proper control thanks to the bucket seat.
It turns out these things handle really bloody well...
PART 2 next post.
Despite all the above, a bigger turbo was still needed, but after a bit of research on here, it was clear sourcing/fitting a different turbo is no easy task.
A Nova TD compressor housing and compressor wheel fitted to the standard turbine wheel and core seemed a common upgrade, but with zero info on how much bigger, if at all, the Nova comp wheel is, and little to no info on performance improvements, it was a lot of work for maybe no gains- Certainly not the gains I wanted, as from my seat of the pants experience I was thinking it's more a restrictive turbine as much as compressor.
Other upgrades I saw involved loads of welding and messing about, or a big bucks HKS turbo. And with all of these, little info on real performance gains, so I wasn't keen.
One thing I do know though is turbos, so after a lot of thought and research, I made my own, and this is the result.
6mm bigger compressor wheel of a MUCH more modern design. 6mm bigger turbine wheel, again, way more modern design.
Compressor housing about twice the size of the standard one. Forward facing comp outlet which means I could shorten the intercooler pipework by about 2foot too. And bolts straight to the standard manifold and downpipe too. Actuator was a pain to sort, but is a modified Renault 5 GT Turbo one now.
All in all, it cost me under £100. If only there was a decent tuning thing for these I'd make more of these (but done prettier with nicer actuators) and sell them. But there isn't, so I won't.
Along with this I knocked up a cone filter setup with some more spares from a Renault 5 GT Turbo, and the result is this...
Even with the boost back down to 0.7bar it was FAR faster than it was even at 1.4bar on the stock turbo, pulled right to 8k instead of starting to die out at 6.5k, and what many might be surprised about- It spooled FASTER than standard- Full boost by 3k in a high gear. It also sounded absolutely mega.
Next job was to hook up my AFR meter and so on, and see what boost we can safely run.
The first issue was, despite it having plenty of fuel (Still in the 10s!) at even 1.4bar on the stock turbo, it was dangerously lean (High 12s) even by 1.1bar on this turbo. Which confirms what I thought about the turbine being the main restriction- Far more airflow now, ie power and torque, even at less boost.
Regardless though, it was QUICK. Honestly twice the power of standard turbo, and pulled hard to 8k, and finally fast enough that you really appreciated the 4wd, which you really can feel on the limit once you got power.
First thing I did was, after reading posts on here for 'advice', fit an adjustable fuel pressure regulator, but rather than a normal 1:1, I fitted a 1.9:1 so I'd not have to bump the base pressure up so much to get the right AFRs on boost. The problem was, even with base pressure at about 5bar (stock is about 2.5bar!), the AFRs were still lean- Turns out the fuel pressure was dropping hugely on boost- Stock pump just couldn't keep up with demand!
This pissed me off a lot as it took a whole lot of testing and messing to check all this, and it was a waste of time.
So next job was refit the stock regulator (to remove one potential fail point) and fit a bigger fuel pump. I had a spare uprated (good for over 500bhp) fuel pump from my RX7, so decided I could make that fit.
Fitting a fuel pump to one of these is a pain in the ass and involves dropping the tank down (4 bolts, easy, but removing and refitting the fuel lines are a ballache). The tank is quite nicely baffled internally though, a decent design.
Once old pump was out it was clear it wasn't gonna be a straight swap, and new pump was about twice the size, but it needed doing, and a lot of cutting and grinding, and a little wiring later, and it was fitted...
Lo and behold, even at standard fuel pressure, with the new pump AFRs were safe even at 1.5bar peak and 1.3bar held. I tried more, but that WILL need more fuel pressure, as it leaned out too much.
While I made a decent exhaust for it as soon as I bought it, I decided to make it a straight pipe unsilenced system, and it was loud. Loud is ok, but it had some awful resonance at 4000rpm that sounded like was blowing a trumpet. So I changed from an unsilenced rear exit that sounded pretty awful aside from at full chat, to a single box side exit system, which was tons quieter, but still awesome sounding. Might have pics somewhere...
Anyhow, at 1.5bar peak, with these mods, and no weight, this car is genuinely bloody quick. Had various tear ups with friends new standard hot hatches, and it keeps up with the best of em up to about 90mph, and out-handles almost anything on twisty roads.
Most of all, it sounds flippin mental. Literally the loudest turbo chatter there is, makes Group B Audi S1 Quattro turbo chatter sound quiet.
Only issue is the gearing is SO low, and it spools SO fast, that even trying to cruise at 70mph on almost no load it tries to boost constantly so chatters like mad, which is funny, but not relaxing. Vids further down...
The only issue I noticed then was after about 20mins of thrashing it started misfiring under load. From experience it felt like the plugs were overheating, and removing the plugs and reading the heat marks, they were deffo too hot. Though the fact they were NGK6s were obvious to me they were too hot for a 1.5bar boost 8000rpm+ engine, so I got some NKG8s and problem solved...
NOW FOR THE BEST BIT- VIDEOS!!!
First up, a video with the big turbo, but only 1bar boost. Still, not slow (gotta be about twice std power), and sounds pretty nuts...!
Next, at 1.5bar peak, much better, much punchier with tons of torque, and sounds awesome...
The chatter is crazy in the other vids, and this is how it is at a cruise just tickling the throttle at 70mph...
Unfortunately the other day, after being out for a few hours caning the absolute tits out of it, I encountered a problem.
As this vid shows, the car runs fine, no smoke, no noises, no overheating, no smoke from the breathers, no water use, boosts and performs normally...
BUT it is dripping oil, like 1 to 2 drips every second, from, it seems at least, the head gasket in the front drivers side quarter. Above and to the left of where the oil pressure switch is.
While it's not exhibiting any blown HG usual symptoms, it looks like that's where the oil leak is from.
Also the MOT has JUST ran out, so those two issues combined mean it might be time for me to end this crazy little project...
Fascinating. Loved that write up. Must get mine sorted - she dropped the tip off of the spark plug and now it's stuck in there tapping away, so I've not been using her.
Agree that a little sorting should make them handle well. Mine's standard, but you can easily control a four wheel drift round big roundabouts - very predictable.