Engine, Fueling and Turbo's - Answers to the most common questions...

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Monkfish

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Day in day out, the same questions seem to appear in these tech sections that are answered in one or two posts. This topic aims to cover all of those questions and provide info (or links to it) to avoid repeat topics and incorrect information being given.

If you have an item of information, a question, a suggestion or would like to contribute to this topic, please do so here. Keep checking back here every so often or before you pose a new question as this will be updated constantly with new topics.

:)

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Monkfish

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What are the differences between a CT9a and CT9b?

They are both standard Toyota turbo's. The CT9a was fitted to all models of the GT Turbo. The CT9b was fitted to all Glanza's. A little more detail and a picture of the exhaust impellors can be found here. Can either turbo be fitted to either car? Yes, although drivers of standard Glanza's might notice a loss in low down responsiveness due to the slight drop in torque.

The stock CT9 turbo on the GT Turbo and Glanza can be ran at 1.0 bar (14.5psi) all day long and, with the correct supporting mods (covered elsewhere in this thread), will see 170-180bhp at the flywheel. Much more than 1 bar and the little CT9 starts to struggle and runs out of puff. An increase from 0.8 bar to 1.0 bar might see you gain 20 or so bhp, but an increase from 1.0 bar to 1.2 will not see a similar gain. This is because the CT9 is being run well beyond it's efficiency envelope and starts to just blow hotter and hotter air, which is not good. If you want more power, it's time to start looking at a larger turbo. TD04L from an Impreza seems to be the most popular upgrade alongside a hybrid CT9.
 
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Monkfish

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I want more power - What do I need?

So, you're hankering after some more power out of your EP eh? Here's a quick guide on what you need to do...

  1. Service the car
    Before you even consider buying any upgrades for your car, when was it last serviced? When was the timing belt changed? If you don't know, do it. It is fruitless spending money on upgrading parts and gleaning more power out of the 4E if your oil is like treacle and your timing belt is like the elastic in your favourite and well worn pair of shitcatchers. I'm sure you wouldn't want to run a marathon eating only dried bread and wearing a Borat Mankini, so your EP won't appreciate being asked to bang out ~30% above stock power on some shitty old oil and filters and a knackered timing belt.
    -​
  2. Ok, so you've serviced the car. What's next?
    Look at your suspension and brakes? Are they standard? Yes? Upgrade them. It is pointless having a blisteringly quick EP if it can't stop or go round corners. Not only is it embarrassing when your car dives off the road to chase hedgehogs, it is also dangerous and life threatening both for you, your passengers and other road users. Further guides on the basics of suspension and brake upgrades will be posted shortly.
    -​
  3. Car serviced and handling/braking mods fitted? Excellent, now the fun begins.
    Now that your EP is running nicely and actually goes round corners and stops, it's time to start releasing some of the potential out of the 4E. Despite the fact the 4E is essentially a Singer sewing machine with a Barbie hairdryer strapped to it, it is quite a potent little 4-banger. That combined with the EP's kitkat wrapper weight makes for a spicey little package.

    The stock CT9 turbo on the GT Turbo and Glanza can be ran at 1.0 bar (14.5psi) all day long and, with the following supporting mods, will see 170-180bhp at the flywheel. Much more than 1 bar and the little CT9 starts to struggle and runs out of puff. An increase from 0.8 bar to 1.0 bar might see you gain 20 or so bhp, but an increase from 1.0 bar to 1.2 will not see a similar gain. This is because the CT9 is being run well beyond it's efficiency envelope and starts to just blow hotter and hotter air, which is not good.

    Anyway, I'm sure you're all itching to get modding, so here's what you need.
    • Full exhaust system - 2.25" is recommended, although I run 2.5" with no issues.
    • De-cat pipe - Keep the Cat, you'll need it for MOT time. More on this later.
    • Exhaust Manifold - The stock one has a restriction in runner #3 that will cause you all manner of ball and wallet ache if ignored. This recent topic goes into a little detail on why.
    • Rising Rate Fuel Pressure Regulator (RRFPR) - Absolute minimum requirement to control your fueling. Running lean is bad. Very bad. SARD is the popular choice.
    • Adjustable actuator set to 1 bar (14.5psi) - Used to control the boost levels. HKS is the popular choice.
    • Plugs and leads - If you've not changed them yet, get some. I use NGK Iridium (Heat range 7) plugs and Magnecor 8.5mm leads (red), although having broken two sets, I'd avoid as they're a bit shit.
    • Intercooler - Whether you opt for Front mount (FMIC) or top mount (TMIC) is personally preference. FMIC is more and generally more expensive, although it is better at cooling and less prone to heat soak. RX7 top mounts are popular for those opting for TMIC's.
    • Fuel Cut Defender - You will also need to fit a Fuel Cut Defender (FCD) to bypass the stock ECU's fuel cut level to enable boosting to 1 bar. This should only be fitted once the rest of the fueling and support mods are on and ready to set up!
      (Thanks to lingl9z for the reminder on this, I knew I had forgotten something! :eek:)

    It is also recommended to change the fuel pump as the stock ones can be tired. The Walboro 255lph is the popular choice. I would also recommend purchasing some gauges to keep an eye on things. Boost, oil temp, oil pressure and water temps would be the best to have to keep an eye on the essentials.

    Other additional mods can be used such as boost controllers, management and additional electronic trickery to make best use of the mods above, although they aren't essentials and are just preferential items.

That's about it. You should now have a Starlet that handles and stops reasonably well and surprises a good number of larger and more powerful cars. Just be sensible with it and drive carefully!
 
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Monkfish

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Compressor Stall

Compressor Stall

Another regular question we get is about compressor stall, commonly called "chatter", "turbo chatter" or, incorrectly, "Wastegate flutter". Chatter and turbo chatter are sort of correct in their terminology as they essentially describe the noise the turbo is making. Wastegate flutter is wholly incorrect as the noise has absolutely nothing to do with the wastegate. It is also sometimes referred to as the "pigeon mod" because compressor stall through an open filter often sounds like a woodpigeon.

Compressor stall on a CT9 running 1 Bar and mesh over the inlet:

(You'll have to excuse the sound quality, it was shot a while back on a mobile)

So, why does it do that? Firstly, you need to know the basics on how a turbo creates boost. When you open the throttle, a vacuum is created in the inlet manifold, plenum and intake pipework cause by the engine trying to suck air in. This also closes the wastegate on the turbo. The exhaust gassed in coming out of the engine and into the exhaust are fed through the exhaust housing in the turbo, spinning the exhaust impeller wheel. This is connected directly to the inlet compressor wheel which starts to suck air in and force it through the intercooler pipework towards the inlet plenum chamber and inlet manifold. As the pressure becomes positive and begins to increase, the wastegate gradually opens. This redirects some of the exhaust gasses around the exhaust impeller, reducing the flow through it and thus controlling the rpm of the exhaust impellor and therefore the rpm of the inlet compressor. It is this control of rpm that determines how much air the turbo flows, commonly refered to as "boost".

Just before I tell you what causes compressor stall, you need to understand how the recirculating (or atmospheric) dump valve works. On the standard system, the recirculating dump valve (or blow off valve) is closed under boost. When the throttle is closed (closing the throttle butterfly leading into the inlet plenum), the recirculating dumpvalve opens to relieve the pressure in the intercooler pipework. The key thing to remember is that before the dump valve opens, the intercooler pipework is positively pressurised.

So where does compressor stall come into it? Well, if you remove the dump valve (be it standard recirc or aftermarket atmospheric), you remove the pressure release point for the intercooler pipework and 'charged' air. So where does it go? It can't go into the inlet plenum as the throttle has been closed (Remember that the dump valve opens when the throttle is closed) so the air goes the only way it can; back through the turbo. The 'chattering' noise is caused by the compressor wheel stopping and starting as the air comes back through the turbo.

"But why does it stop and start?" I hear you ask. Simple. At the point the throttle is released, the pressure in the exhaust manifold drops to a level lower than than of the charged air after the turbo (ie, in the IC pipework). This inbalance in pressure stalls the turbo and some air is released. The pressure in the intercooler pipework drops and the compressor wheel is then spun again by the pressure in the exhaust manifold and the whole cycle starts again.

It happens very quickly on the CT9 due to its small size, which is why the compressor stall is quite fast and high pitched. The loudness, duration and actual sound will vary from car to car depending on the turbo, the boost level, the type and size of air filter used, the length of the inlet pipework from the filter, the size of the intercooler and length of the intercooler pipework. That's not to mention the colour of the lucky underpants your distantly related Nan's dog wears when it goes out on the town.

The next big question you're going to ask is "does it damage the turbo?". If you do some Google bashing, there seems to be two schools of thought. Make of them what you will, but I'll tell you that I've been running a CT9 at 1 Bar with no BOV (Save for when I get bored and fancy a change for a week or two) for several years now with no problems. That and BOV's are for nonces :p. Besides, there are so many factors to take into consideration when you look at the life span of a turbo ranging from the type and viscosity of oil you use to your driving habits, exhaust gas temperatures, boost levels and the aforementioned dogs undies.

:)
 

Monkfish

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Do I need a Catalytic Converter (Cat) to pass an MOT?

Do I need a Catalytic Converter (Cat) to pass an MOT?

The common answer to this question is "It's an Import, so no". This is incorrect. If you own a Glanza, it will need a Cat to pass the MOT. If you own a GT, it depends on its date of first use (This is found on the V5) although this will only effect the later Mk3 Quadlights.

Ok, so the MOT handbook currently states that any car first used before 01 Nov 1995 where the engine code is not in the DVLA database (ie, the 4E-FTE fitted to all Starlets) only has to pass the basic emissions test. The basic emissions test consists of measuring the exhaust CO2 levels at idle, with the failure limit at 3.5%. If your 4E is over this limit, even without a cat, you either have it fueled to run a turbo the size of a dinner plate or it is fucked. If you garage tells you that your car needs a cat test, tell them to re-read their MOT handbook or go elsewhere to a place that isn't employing morons.

However (this is the bit Glanza and Mk3 GT owners need to pay attention to), if your car was first used on or after 1st July 1995 where the engine code cannot be identified, then it needs to pass the basic cat test. This test differs from the basic emissions test in that the CO2 limit is 0.5% at idle and 0.3% at fast idle (Usually around 3,000 rpm). As you can see, it is quite a lot tighter than the basic emissions test. My GT, running 1 bar and with a decat measured 0.86% at idle and was borderline with the cat on. In short, don't smash the guts out of your cat as a cheap de-cat as you'll need it for the MOT.

Note:- On the V5, "Date of Registration" is different to "Approximate date of first use". The first is the date the car was entered into the DVLA system (ie, when it was imported), the date of first use is the approximate date the car was registered in Japan, taken from what little paperwork will be with your car.

This is the flow chart used by MOT stations to determine if a given car requires a Cat test...

(Thanks to kieran.s for digging it up from an old thread)

http://www.dft.gov.uk/vosa/repository/7.3%20Emmissions%20-%20Spark%20Ignition%20-%20Passenger%20Cars%201992-2002.pdf

So there you have it, all you need to know about Cats, MOT's and the little Starlet. If you live in a different country to the UK, you will need to check the rules and regs with your local governing body.

:)
 
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Monkfish

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What is fuel cut?

What is fuel cut?

Fuel cut is exactly what it says on the tin, the fuel supply is cut to the engine. But why does it do this? Read on, young Padawan.

Whilst the engine is running, the ECU is monitoring various (Read: Lots!) of things going on in the engine with a plethora of sensors. It monitors things such as air:fuel ratio, rpm, temps and all manner of other things I'll not go into now. Basically, it knows how much fuel it needs and how much it is throwing through the injectors. Fuel cut is basically a fail safe. If you modify an engine (For example, increasing the boost for more power) you'll get to a point, about 0.8 Bar from memory, where the ECU basically says "Hang on, if you run the boost any higher without more fuel, bad shit is going to happen" and it then cuts the fuel to the engine entirely to prevent it running lean and causing detonation.

What you'll experience when you're driving is a sudden loss of all power (It'll feel like you've driven into a wall), lots of lurching about and the engine management will light up (as well as your underpants if it's the first time :haha:). After some careful driving, the engine management light will go out and all will return to normal. Constantly hitting fuel cut will also damage your engine, so if you do keep cutting, you need to find out why if you don't know and rectify the issue. You can also get fuel cut on a cold night if you're running boost close to the cut level and are getting creep.

To remove the fuel cut, you need a fuel cut defender which basically tricks the engine into thinking all is well and it'll not fuel cut. Important note: Simply removing the fuel cut without the supporting modifications will cause your engine internals to have and argument with the block and depart. Violently. Please take the time to read through this article in this topic before you proceed.
 
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