[Avoneer]

Never having an FI'd car and it all being new to me, can somone explain the basics and eveything I'd need for a safe reliable turbo'd 5.

I understand the theory on how they work in a basic fasion - compressed air being forced into the head, but that's about the limit of my turbo knowledge.

Don't get the detonation, knock, timing stuff, intercoolers and AFR etc.

Also, I noticed MX5 MAD have a few offers on at the moment on basic Greddy stuff - any good?

Thanks,

Pat...

[steve b]

Basic Begi's worth the additional.

Basically when the turbo compresses the air it heats it, this is why turbo sizing is important a small turbo running x psi of boost to create Y power will heat the air more than a big turbo running the required boost to make Y power.

Hot air is bad, less dense, less O2 thats why we have intercoolers to cool it back down. More boost = bigger intercooler required.

Boost = more O2, more O2 needs more fuel so you need to inject more, so various ways to provide it. Best is the right size injectors (theres a calculation to work this out, I forget it at present) and an ECU to control them. As timing also needs to be retarded on boost a standalone ECU makes even more sense. Alternative ways are higher fuel pressure and retarded base timing, but then the car will be sluggish off boost.

On boost AFR needs to be about 11.7:1 so a fair bit richer than cruise that can be around 14.7:1 or a bit leaner to save fuel.

Too little fuel on boost, too little igntion retard on boost (compaired to n/a), insufficient intercooling, insufficient engine cooling can cause det / knock / pinking basically the mixture igniting at the wrong time from the wrong source i.e hot spots on pistons etc rather than the spark from the plug. The uncontrolled explosions crack pistons and create a positve feedback, i.e. 1 uncontrolled explosion heats up the cylinder more, making another more likely, the more it happens more likely engine will fail (usually collapsed ringlands).

Hope that helps a bit

Ultimately the most important thing with turbos is choosing what power you want and then using the correctly spec'd bits. i.e. only want 180bhp then get a smaller turbo thats efficiency range 180bhp falls in the middle of, rather than a big turbo thats peak efficiency is 250bhp. Its more likely to cause problems pushing a small turbo hard than under working a big turbo as the big turbo will just provide lag, not hot air that could cause det.

If you only want 180bhp then you don't need 550cc injectors, smaller will offer a better spray pattern and better idle. etc

[rodders]

Hi Pat

Turbo`s = Where do I start?

You obviously have the basics.
turbo = forced air
Detonation or pinking is caused due to lack of fuel or timing advanced to far.
many overcome both of the above by using Emanage etc
My car (dare I say this?) has neither
Fuel is increased by means of a fuel pressure reg with 1.8 injectors
timing retarded manualy
Intercoolers are used to cool the air from the turbo before entering the inlet manifold.
Hope this helps and feel free to ring me with any questions anytime 07770 566599
Paul

ps my old BBR kit will be for sale around Christmas.

[Avoneer]

Cheers all - that makes a lor of sense and even I understand it now.

Paul - you have PM (when I get round to it....)

Pat...

[Mi5]

A couple of points on timing/det/pinking.

During the compression stroke the mixture of fuel and air is compressed, and then ignited by the spark plug. A flame front then travels through the mixture making heat and pressure - this takes time, so to get power you must ignite the mixture before TDC. The more you advance the timing the higher the peak temperature and pressures will be - as more of the mixture is combusted before TDC - this gets you a bigger "push" on the power stroke. However, if the peak pressure and temperature are too high and the auto ignition temperature of the mixture is achieved, then you will get detonation - in this scenario all of the remaining mixture explodes (rather than controlled burn) instantly causing very high pressure waves and this causes damage to the engine.

Detonation damage is usually characterised by errosion of the pistons, this is what I was looking for with the bore scope at the tech day. From what I have seen (not on my engine I hasten to add) its is usually the sharp machined edges that go first.

A number of factors determine how much advance you can run, the primary ones are:
1. RPM - the faster the engine is spinning the less time there is to burn the fuel, therefore more advance can be used
2. MAP/LOAD - the more air you put and the harder the engine is working in the higher the incylinder pressures and temps will be and so more MAP needs less advance
3. AIT - putting in hotter air will resut in hotter in cylinder temps (essentially as you start hotter you will end up hotter) so needs less advance

Then we have preignition - this occurs where the mixture is ignited very early due to a hot spot, and the resulting explosion literally forces the piston back down the bore and can bend or break rods.

An engine can usually survice many 100's or even 1000's of detonation events (depending on severity), but detonation can induce preignition. A single pre-ignition event can kill the engine.

Matt

[Avoneer]

So what's the safest reliable solution once you have the turbo bolted on - a stand alone ECU?

Pat...

[steve b]

Avoneer, on Oct 13 2008, 04:56 PM, said:

So what's the safest reliable solution once you have the turbo bolted on - a stand alone ECU?

Pat...

[DMRider_10]

^ The safest solution is on that doesnt induce any knock. That could be anything. A badly tuned anything is bad.

But in terms of what it can do the most for you if set p correctly, yes a standalone is best

[Avoneer]

Ok, how about a knock sensor and a wideband doo dar?

Necessary?

Thanks,

Pat...

[steve b]

Both are only necessary if you are going to tune it yourself, if your taking it to a mapper they will have their own that they will use. If not and doing it yourself you;ll also need these.

[Avoneer]

I'll be replacing my ECU with a MSPNP.

Not sure I'll fully understand much/all of it, so may get someone to do it.

That way the pennies for the sensors can be invested in rr time.

Sound good?

Pat...

[Jaydee5]

The more I hear/read the more I realise I fell really lucky with Fluff



I just drove it