Bigger injectors on NA

[shnazzle]

Is there any merit to running 2zz injectors on a stock NA?

Better spray pattern for a better burn? Less lag time/better fueling response?

Any benefit to lowering duty cycle while maintaining fueling?

All of course assuming running a piggyback at least.

I know tommyzoom/hachiroku needed bigger injectors but their NA is at a high state of tune and required the extra fuel for more power.
But, assuming I'm nowhere near maxing out my injectors, is there an opening here to allow the car to unleash some more torque?

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[Jacobsprky]

not sure? running bigger in mine but with the maf mod seems to go ok.

[shnazzle]

That's where the thought began. But I don't plan on running the MAF mod. No point as I've got the emanage. The bigger injectors on the MAF mod are there to compensate for the change in air mass readings.
But that can all be done with the piggyback.

However I do wonder if running the MAF mod (i.e. bigger injectors) makes for a cleaner and better burn.



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[ChrisGB]

Can't see it making significant difference. Leaning out from stock values yields power and torque gains. Back in the old days, the was some gain from increasing injection pressure in some vehicles, along with reprogram and or smaller injectors. But can't see it being of any use on modern systems.

[shnazzle]

This is the part I struggle with understanding. Some texts say "more fuel, more air, more power!"
But the leaning out to me means a quicker and more explosive.. er.. .. explosion. So I would expect torque from that.



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[jonbill]

This is the part I struggle with understanding. Some texts say "more fuel, more air, more power!"
But the leaning out to me means a quicker and more explosive.. er.. .. explosion. So I would expect torque from that.



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The theoretical limiting factor is the amount of air(oxygen) you flow through the engine. Fuel & spark tuning for power is all about trying to use all the oxygen.
With stoichiometric mixtures and leaner, you don't use all the air.
So for full power, you end up at maybe AFR 12 - 13, a small excess of fuel to ensure the air is used up.

[shnazzle]

But only at full load and higher rpms,when you're "pumping" the most amount of air.
But at lower end?

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[jonbill]

Same applies if you're looking for power at low rpms. It's still about using the airflow that your cam & head offer.
If you're cruising then you just need to produce as much power as required to overcome the wind/friction at that speed. I think thats about 20 bhp at 70mph.
So you can be much more economical there, so go stoichiometric or even a bit leaner.
I think  s:) s:)

[shnazzle]

Agreed on the cruising part.

And I'm comfortable with the high rpm/load scenario, i.e. the bottom right of the map.
But the part I'm not sure of is the left side. The part of the map where you're low in the rpms, so you're not pumping much air in, so you're limited in the amount of fueling you can do.
Would you aim for running richer (15-15.5) from about 70% throttle from 1k rpm to about 2500, to get past the initial friction and weight of the car?
Then slowly lean out a bit towards 4k while you're no longer "getting it going", and then rich again from 4k until 6.9k?

But in that initial 1k to 2.5k,would it not help to have slightly bigger injectors so that you can maintain the timing but have more fuel at that point? Adjusted a tiny bit for the extra time it takes for the flame to propagate with more fuel...

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[jonbill]

Yes I think I'm agreeing with  you, but maybe you've got the numbers back to front - 15s is leaner than stoichiometric. I think I'd aim for mid 13s under load at the bottom end, going to high 12s at the high end (still under load).
Whatever the revs, if it's not under load then you can lean it out towards 15+.
Qualifed by an "I think" just in case [emoji4]

[Jacobsprky]

my 2 cents is that in your car you are putting allot of extra air in faster because of your intake and bored tb so there maybe some gains from slightly bigger injectors? im sure opinions will vary tho. As you can map your car im sure it would run the same/better with the bigger injectors in, provided it was mapped correctly. Jacob

[shnazzle]

Wish I'd kept the 2zz injectors to play around with now  s:) s:)  

Two conflicting opinions so far.
But I'm tempted to think that as I'm nowhere near full duty yet, there's no gain in going bigger.

If there was a prospect of a little gain, it'd be worth a shot as frankly that is the N/A game... Little gains here and there.

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[Jacobsprky]

if you can make an improvement then why not, they all add up. trial and error!

[lamcote]

I'd ask, do you know what AFRs you are running at the moment in the areas of the map you are wanting to improve?

[stupink]

A half assed reply to a half read post... But I think my usual comment stands here, there is NO point tuning part throttle for anything other than economy (within reason, you clearly wouldn't want a 600hp car with only 50hp at 80% throttle)..  But...   you want to consider an engine is a power plant, it is there to create power, the gas pedal does not add power, it removes it... so a standard engine makes 140hp, and by not pushing the pedal 100% we limit that to a lower amount(by blocking air)... So why try to increase that?  you choose to limit to say 60%, then raise it via tuning so its 65%? just push the pedal a bit more?

That said I understand you're trying to consider all options, response etc, lean is more responsive/powerful(to a point).. but.. that is what Toyota have already set the car up for  s:) s:)  so unless you've changed much else this kind of tinkering usually doesn't really make any worthwhile improvement.

As for full throttle, now we need to get extra air in so less restriction in the intake, bigger capacity cylinders, bigger exhaust so more of the old burn gets out etc etc all helps and then extra fuel is needed to create the "right" mix, but, bear in mind the standard injectors are as you say going to be running quite a tolerance, so they wont be anywhere near maxed out, lets say 75% duty cycle, BUT what you may not be thinking about, is that they're also only going to be at 75% at full throttle at the rev limiter, any lower RPM and the fuel demand is lower as theres more time to inject the fuel..

Sorry, writing lots of stuff, a bit tired and bored..  forgot the original question haha.. hope something useful there somewhere  s:) s:)

[shnazzle]

Original question was if 2zz injectors would lead to a more efficient burn, and possibly better access to the engine's torque, given an increased airflow by means of the intake and bored throttle body.

The conversation segued a bit into mapping. The intention again there was not to unleash more power at part throttle, but to displace the torque curve a bit perhaps.
I have absolutely no intention of messing with Toyota's good work in cruising conditions. I'll let it do what it does best.

I don't have a wideband (yet), so that's the big limitation at the minute. I have no idea what the car does.

The easy solution would be to get it mapped, but where's the fun in that?! (and not worth the money).
I ask these questions because I want to understand more about engine management.

I feel like I'm about 50% into understanding fueling, and then I still have timing to start on. All the while building up a basis on airflow, thermodynamics, etc etc.
Keeps me off the streets haha

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[jonbill]

Wideband AFR is endless fun. Every journey is a rolling road session  s:) s:)

[shnazzle]

Wideband AFR is endless fun. Every journey is a rolling road session  s:) s:)

Or endless frustration haha.
But yes, I do look forward to it

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[lamcote]

I think it is difficult to speculate what fuel change would improve low/mid range power until you know the current AFRs.

Many people have discovered that the 1zz runs too rich to make maximum power. This is done deliberately by Toyota to cool the engine and cat during periods of high load use.

There is no reason to believe that this rich running isn't used throughout open loop, including low/mid range revs. If so, adding even more fuel will only reduce power further.

I realise you ALSO [edit, (having bothered to look!) MAINLY] wondered whether the design of the 2zz injectors might be better than 1zz, so may yield improvements. Maybe? But stupink's comments regarding the way to think about the needs of the engine are very wise and are well worth reading very carefully.

In addition to all of this, if any changes made also affect closed loop cells, everything will be undone anyway, by the standard ECU. Presumably just adding bigger injectors would be bound to affect closed loop?

[ChrisGB]

Thinking about this some more, bigger injectors need a smaller duty cycle for a given load. So theoretically, you could end up with the injector firing for less of the air column entering the engine, which could, in turn, lead to poorer atomisation of the mixture, which could lead to a less efficient burn.

Tuning is a tricky business. Generally, for top end power, you are removing airflow restrictions (there is always something that is the limiting factor for gas flow, the more you chase down the more it costs). However, you need to carefully consider where these restrictions are. From experience, it is clear that the standard exhaust is restrictive, but the airbox is not. No idea about the throttle body. However, it is a long stroke engine with a relatively small set of valves, so it will never be a top end star performer, and ultimately, with perhaps stage 3 cams and a custom built, properly developed and tuned 4 into 1 exhaust manifold and free flowing system, standalone ECU you may make over 200bhp, especially if you up the compression ratio and go big bore. It is going to cost as the revs will probably need to go up beyond the capability of the rods.

On the subject of gas flow, it is not just about bigger holes in and out of the engine. The resonant timing of inlet and exhaust systems needs to be optimised to get the best scavenge and cylinder fill possible for the given load. This relies on the exhaust pulses generating pulses in the inlet system to draw mixture into the cylinders, and given a good design, the pumping efficiency can be as high as 125% at peak torque on modern engines, which is impressive. This positive fill effect can only be induced by clever use of pulse timing, or by forced induction.

Mid range torque is more where the 1zz-fe shines. Here, manifold design optimised for the mid range works well with the VVTi system to give a good figure for the displacement.

Mixture is all about optimum burn efficiency and delivering peak cylinder pressure and brake mean effective cylinder pressure at the optimum time in the down stroke of the piston. Too rich, you cool the mixture prior to ignition, slow the flame front and reduce the overall burn efficiency. Too lean, you can end up too hot pre spark, resulting in detonation, or really lean making the burn weak. The ignition timing is used to deliver the peak pressure at the optimum time. Too early, you put huge stress on the engine as the peak pressure arrives before TDC. Too late and you lose burn speed and heat and end up with very high exhaust gas temps from waste heat, burning valves and killing cats.

Whatever you do it is going to cost. Trust me, this I know.

[shnazzle]

This is gold guys.
I know it's all "known knowledge" but to me, having only read about each of these areas, marrying it with the 1zz design really brings it home.

This isn't something I'm hoping to investigate in depth in practice. The injectors maybe, hence the question.
The reason I mentioned that timing is still something I have yet to begin on is because of the likes of scavenging, pulse timing, intake design, valves, piston crown design, exhaust runner length and design.
To me, having all of these areas, each with such a rich depth of knowledge required to begin to understand, is like a goldmine. Keeps me reading for weeks, buying books, looking at diagrams, making drawings.

The conclusion being that it all seems to simple doesn't it? And a lot of it CAN boil down to simple things such as that a less restrictive intake and exhaust generally allow for more power. But why? That's where it gets interesting for me.

So when I ask these (silly) questions, it's because I'm trying to dissect a particular area of interest at that time. Which is fueling at the minute.

I tried exhaust design a few weeks back if you remember and it gave me a lot of direction for areas I need to know more about.


... I'll end up with a degree in mechanical engineering at the end of this hahaha

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