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The mkiv Supra Owners Club

Injectors


Paul Booth
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550 refers to the number of cc of fuel per minute the injectors can flow if open continuously. The UK injectors are 550cc and the J-spec are 440cc.

 

A common J-spec mod is to fit 550cc injectors and re-map the fueling using an air/fuel controller such as the Apexi AFC.  

 

Yours,

J

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OK, that's what I thought, i.e., they were equivalent to UK spec injectors.

 

So, I'd prefer somewhere in the UK to get them from as importing scrap iron from the US is difficult and expensive to return.

 

JB - what do you know about the status of Justin's injector farm?

 

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Quote: from Ash on 5:54 pm on July 15, 2001[br]

 

550 refers to the number of cc of fuel per minute the injectors can flow if open continuously. The UK injectors are 550cc and the J-spec are 440cc.

 

A common J-spec mod is to fit 550cc injectors and re-map the fueling using an air/fuel controller such as the Apexi AFC.  

 

Yours,

J

 

forgot to ask if you need to do anything with the injector pump?

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Shop!! are looking into the 550cc injectors and we will get back to you...

 

the stock fuel pump should be sufficient, depends what BHP you are going to. Easy option is to just get a UK spec fuel pump which is uprated over the import versions. If you want a price on one let me know.

 

JB

Shop!!

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The UK fuel-pump will probably need to be fitted depending on power levels.

 

Basically, when it comes to uprating the fuelling (like just about everything in life) there's a Mickey-mouse way and there's the proper way.

 

Mickey Mouse way is to try and stuff more fuel in using additional injectors pointed at the throttle-body. Upside is it's relatively cheap; downside is you are asking an intake manifold that was only ever designed to flow air, to now flow air and fuel.

 

The intake manifold utilises a common plenum coupled at right angles (or thereabouts) to long intake runners. This setup gives good mid-range power and is rather efficient at flowing air.

 

However, when it comes to flowing air and fuel, there is the potential for fuel dropout as the air changes direction in order to flow into each runner.

 

Reason being, one of the simplest ways to remove about 90% of any moisture in compressed air is to force the air to suddenly turn through 180 degrees. You can see this kind of air-drier on most of the air compressors sold at places like Machine Mart.

 

It works because water molecules are much heavier than air molecules. The air finds it much easier to change direction. But water molecules, being much heavier thus creating more momentum, find themselves doing the equivalent of understeering and crashing into the armco.

 

Furthermore, the length of the runners, in itself, greatly increases the potential for fuel dropout.

 

In the case of a compressor, the water can be seen collecting at the bottom of a plastic bowl. In the case of an engine, the fuel puddles in the manifold. Thus leading to uneven fuelling across the cylinders... and right where you least-most need it: at high boost pressures.        

 

The proper way is to increase injector and pump size and change the fuel/ignition map to suit.

 

As an aside, we managed to sort out the leaning out problems with Justin's EVO by fitting a higher-pressure fuel pump.

 

Before the pump was fitted, in order to defeat fuel-cut at stock boost, we were forced to run an A/R of 13.4 at WOT which is way too lean. After fitment, we were running a WOT A/R of 10.0 which is way too rich - as our target at WOT was 12.0 A/R.

 

However, rather than having to go to all the time and expense of fitting an AFC, we found there was ample adjustment available by altering the rotary setting on the HKS FCD.

 

Which is quite amazing really. When you think about all the past arguments where people have been saying that it's safe to fit and it doesn't affect your A/R ratio at all, and so forth.

 

And there were were actually using the Fuel-Cut Defencer as an A/R trimming device!

 

In fact, set three-clicks more clockwise, we had the mixture spot-on 12.0 at WOT. We didn't have the time to plot the whole boost curve, so I'm not sure how fuelling will have been effected at other times, such as at the vacuum to boost threshhold, but it's good enough for now.    

 

Yours,

J

 

(Edited by Ash at 3:30 pm on July 16, 2001)

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Mickey Mouse way is to try and stuff more fuel in using additional injectors pointed at the throttle-body. Upside is it's relatively cheap; downside is you are asking an intake manifold that was only ever designed to flow air, to now flow air and fuel.

 

You're kidding aren't you? Pour fuel into the intake pipes? What, where, who and for lawdy sakes, why?

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Well, Paul, that's what some people advocate even today.

 

Though that's how all cars *used* to intake fuel at one time. Only the injector was called a carb and you had to have these tiny intake runners that sapped mid-range power potential. However, there was no choice, on a road-going car, as longer intake runners would mean much low-down efficiency would be lost through fuel dropout.

 

Then came electronic fuel injection. And with it the problems of fuel dropout virtually disappeared overnight. Because, finally, there was a way to inject each indvidual cylinder with a precisely metered quantity of fuel: by utilising a fuel injector located right behind the intake valve(s) of each cylinder.

 

That meant there was *much* greater flexibility in the intake manifold design. No longer hampered by having to flow a fuel/air mixture, engineers boosted mid-range efficiency by designing manifolds with a single throttle body linked to a large plenum chamber. This chamber would feed long intake runners, tuned to each particular engine, and would utilise the pulsing effect of the intakes in order to increase air delivery to the cylinders.

 

The upshot of which, gave us engine efficiencies never before seen in a reciprocating IC motor.

 

But there are those companies and/or individuals whom today see fit to take retrograde steps, usually profit or convenience, and call it sound engineering practice.

 

To someone like myself it's flaming laughable really, but it's a tuning fact I have learned to accept.  

 

Yours,

J  

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Carburettors I can live with, did live with, and they still have their place where the stroke length and swept volume won't support injectors efficiently; very high revving, low CC motocycles for example.

 

But to chuck fuel into the intakes on an already injected engine seems to be a direct route to an unmanageable power profile; or a straight line dragster whereby the throttle is a binary switch.

 

Doesn't look like it has any elegance, but maybe I'm being a bit of a purist.

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Thanks, I've been in touch with Justin, he'll sort me out some injectors.

 

For the power levels I propose to run, whilst it is not ideal, I will use the additional injector kit, which incidentally I have already fitted. Ash is right, the additional injector kit is a bit crude and I agree injecting fuel into what was meant to flow air is not ideal, however the additional injectors will only operate at say 1bar+boost on the larger twin turbo kit I will be fitting. At the moment I only use the AIC on my hybrids at 15psi plus.

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that raises the question that if you are planning on running enough boost to need additional injectors why not go the full whack and get 720cc injectors, second fuel pump and larger fuel lines to make sure you have sufficient fueling at whatever boost you are running.

 

I would only upgrade the 440s to 550s if you plan on keeping the sequential system, going to true twins is a major step up which really needs better fueling and a better ECU or something like the FCON or Motec.

 

I suppose it all depends at what point you plan on stopping the mods, always try and build in some slack so you can upgrade again at a later date.

 

JB

Shop!!

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Quote: from branners on 10:07 am on July 16, 2001[br]Justin can probably pick up a few more sets, I will ask him what he can do. He tends to get them fully refurbished as well just to make sure one of them isnt blocked.

 

more details when I get them.

 

JB

Shop!!

 

Regardless of Mark's resolution to his requirement, I'm still waiting for your feedback from Justin.

 

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Well, I know what type of fuelling methods Toyota would have fitted had they designed the motor to produce 750 HP stock. And that is precisely what I am in the process of designing for my car.  

 

Plus, I agree with JB, fitting the big twins is a *major* step which needs proper mapping with a proper ECU driving an uprated fuel system together with a modified ignition curve. But as long as it's not *my* motor..........

 

I used to wonder how these big turbo'd cars, with AICs fitted, get away with it.

 

What I reckon is the people who set them up, just run mad rich at WOT. So it becomes a case of what the heck if No1 is running leaner than No4 cylinder (or whatever) the whole thing is just awash with fuel anyway.

 

If you were to try and set the motor's fuelling properly, I'd bet you'd find a situation where at WOT there would be a wide variation in A/R ratios across the six cylinders. Running from the richest, say, 11.5 A/R to the leanest 12.8 A/R.

 

Now, an engineer would look at this situation and come to the conclusion that such a wide variation in fuelling, across each cylinder, was totally unacceptable - particularly in a high-power turbo motor. Not only that, such a variation will cause a significant power loss.  

 

But in bolt-on tuning land, all you do to mask this problem is to set the motor to run an A/R of 10.0, say. So in that event, while there will still be the same wide A/R variation across each cylinder, and you will be losing a lot of potential HP as a result, no individual cylinder will be running lean.

 

End result being, the car will feel fast and the fuelling method will appear to work, thus giving the whole setup an air of legitimacy.  

 

Yours,

J

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we should have an answer on how many sets of 550s we can get later this week and I will let you know then whats available and what condition they are in.

 

Theres also a conversation on the NZ mail list about twin setups and 720cc injectors, they are basically saying the same that running serious boost on twins needs decent injectors.

 

JB

Shop!!

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Quote: from Ash on 9:27 am on July 17, 2001[br]

 

Well, I know what type of fuelling methods Toyota would have fitted had they designed the motor to produce 750 HP stock. And that is precisely what I am in the process of designing for my car.  

 

Yours,

J

 

"I canna get 'er of the groond cap'ain, she wilna tak any more".

 

 http://www.stopstart.fsnet.co.uk/aircraft/pigflys.gif

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There is a third way - an FSE valve.  Don't ask me what that stands for or how it works, though.  I think it increases the fuel line pressure, therefore increasing the potential maximum injector flow.  And I think you need the UK spec fuel pump as well.  I know it works, I've got one :)

 

-Ian

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Quote: from Ian C on 10:01 pm on July 17, 2001[br]There is a third way - an FSE valve.  Don't ask me what that stands for or how it works, though.  I think it increases the fuel line pressure, therefore increasing the potential maximum injector flow.  And I think you need the UK spec fuel pump as well.  I know it works, I've got one :)

 

-Ian

 

Could someone commenting on Ian's posting explain what the FSE does before simply stating any preference please?

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