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Secondary injectors. What and where? LOL


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The reason for the secondary injectors is that if the engine used large primaries only, it becomes difficult for the ECU to control fueling at low rpms and low loads. Fuel injectors are most efficient and best controlled at high duty cycles. If you put huge injectors in there and drove around at normal traffic speeds, the engine would be very unresponsive.

So Lotus uses secondary injectors to deliver more fuel at high load and high rpm only, and maintain street drive ability with smaller primaries that are sized correctly for average driving.

Same reason the 4cylinder Esprit SE-S4s and GT3 use two secondary injectors.

ok here is another question:

I installed Johan chips, his chip is very rich at wot. I probed when I went for a DYNO. The AFM is running 10:1. I know Nathan has the same chip and problem. He installed a piggyback AEM (I think) to lean the AFM.

Do you think by disconnecting the secondary will help?

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Thanks Mike, I've been wondering for a while now. Wha about on startup? John

Your description of how an injector works is correct... however there are two types of fuel injector -- high impedence and low impedence. The high impedence injector requires 12v to stay open and is s

The issue with the secondaries is usually that the person who re-installs them doesn't get them sealed correctly...  The secondaries are side/galley fed rather than top fed, and the sealing o-ring is

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No, please don

1996 Esprit V8, 1998 Esprit V8 GT, 1999 Esprit S350 #002 (Esprit GT1 replica project), 1996 Esprit V8 GT1 (chassis 114-001), 1992 Lotus Omega (927E), 1999 Esprit V8SE, 1999 Esprit S350 #032, 1995 Esprit S4s, 1999 Esprit V8 GT (ex-5th Gear project), 1999 Esprit V8SE ('02 rear)

1999 S350 #002 Esprit GT1 replica

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I'm really quite confused on secondaries... this secondary injector thing is extremely rare in most of the rest of the automotive world. 235cc injectors are very small and very few turbo charged engines use an injector this small. As an example -- the eagle talon/mitsubishi eclipse has a 2.0 litre turbo with 440cc injectors (330cc in the pre-1995 models). It has a 264 degree cam duration (as I recall) and it runs just fine with these large injectors. It's not even remotely "lopey". The idea behind using smaller injectors is that the pintle is smaller in relation to the fuel molecule and therefore creates a better spray or misting effect, which creates a more efficient burn... there is a second factor and that is that the pintle can be moved easier because it is lighter -- the weight of the pintle and the speed with which the solenoid can open and close it is referred to as the "latency".

Basically, a 235cc injector is going to be very easy to open and close and therefore easier to control the open time... which means better efficiency at idle and low-load situations. However... 235cc is quite small and... I would consider it excessively small... but i'm not an engineer-- can somebody chime in here that knows why they would think this the case?

Here's why I'm lost... lets say the volume of each cylinder in the mitsubishi is 500cc (which it is) and the volume of each cylinder in the lotus is 437.5cc... now the longer the stroke of the engine... the higher the velocity in the intake runner (assuming the same port diameter -- the mitsubishi port is very large and therefore would have a relatively slow port velocity) This gets into some pretty complicated math.. but the stroke of the mitsubishi is 88mm and the stroke of the v8 in the esprit is 83mm.. so there is a longer stroke and therefore a higher potential port velocity if the volumes of the cylinder were the same. They are not... so.. in theory (and, yes I realize i'm missing a critical factor which is the size of each valve and inside diameter of each respective port) but... effectively my deduction is that the engines should pretty much have the same port velocity because one cylinder is 12.5% smaller and one stroke is 5.5% longer... I can't imagine that the lotus v8 couldn't have simply installed 330cc injectors and call it a day --330cc injectors could easily handle 350hp at 80% load.

As another note, it is my understanding, that the injector size that starts to cause issues is around 600cc+... This is because the larger injector effectively shoots a stream as opposed to a spray... and when the air isn't moving quickly, it's movement is insufficient to keep the fuel in suspension and it sits on the walls of the intake plenum causing many other little issues like detonation and wasted fuel. I have installed 550cc injectors on the 300zx turbo with slightly higher compression pistons and it doesn't have an idle problem at all. You just have to make sure you adjust your "k-value" properly when tuning. As a side note... I have a collection of fuel injectors that i save from every engine i take down and I think the smallest one is 180cc/min which was from my toyota supra inline 6.

The addition of secondary injectors, however, makes the engine easy to modify at very little expense (you need to buy only a couple of injectors as opposed to 8).. so if they wanted to test the maximum hp etc... it would be easy for them to simply leave the base tune alone in the computer with the smaller injectors and just add bigger secondaries and re-map the WOT map in the computer.... Anybody have any info on this too?

Modifying esprit's.. now that's fun..

PS... I AM NOT A CERTIFIED MECHANIC.. I Have chosen to help those in need, in the past and must not be construed as being a certified technician.

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All this is easy to explain. The Japanese use evil black magic and Alien technology to design and build their cars.

It's simply not natural how they can build these cars, and still be so reliable. Just look at the Skyline!

That's my understanding of it all. Hope it helps! :)

John

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Mark very nice write up.

The stock Lotus injectors you said is 235cc with supplementary secondary injectors.

Let say 330cc is the best injector for Lotus without using a secondary.

Injectors are set to fire in two ways: Alternating firing scheme or Simultaneous firing scheme. (lotus is alternating)

The critical point is during the peak power and wide open throttle.

Injectors has TOG (Time On Gama) (injector pulse width). Fuel delivery is controlled by the injectors which are cycled by the computer. The computer produces a signal to open the injectors for a certain length of time depending on engine conditions relayed by sensors. The longer that the injector is open, the more fuel is injected. As engine load and rpm are increased, the injector open times are increased to match increasing airflow. This computer output signal is called the injector pulse width. The longer the pulse width, the more fuel is injected.

Now we know, injectors is not the only deciding factors. ECU plays an important role.

If we will take the ECU out of the picture and talk about "just" the injector 235cc vs 330cc, here is what I know inside the injector.

As current starts to flow through the injector coil circuit. When current flows through a coil winding, all of the current is used to create a magnetic field around the winding.

The magnetic field is proportional to the current and the number of turns in the coil. In other words, the larger the current, the larger the magnetic field. As the magnetic field is building, the inductance offers resistance to the change in current flowing through the injector circuit. As the field builds, it moves across the coil winding and induces voltage into the coil winding. This induced voltage frees electrons, offering resistance to the change in current flowing through the coil.

The analogy is this, Imagine a school hallway packed shoulder to shoulder with children running as fast as they can. Now imagine children entering the hallway from classrooms located along this hallway. The children leaving the classrooms can't change the flow of children already running down the hallway without increasing the pressure. Just like the children entering the hallway, the induced voltage (pressure) in the injector winding creates resistance to the change in current flowing through the injector circuit. This resistance is called counter electromotive force, or counter voltage.

So, to go back to your 230cc vs 330cc, you are exactly right. No matter how you squeeze, 230cc will not do the job without supplementary secondary injectors. 330cc will work without secondary injectors (more powerful magnetic field due to the big coil winding) require more voltage to run than the 230cc...but here is a catch.

To visit my original question to Mike:

"why do you think Lotus put a secondary injectors instead of configuring the 8 injectors a bit bigger?

Do you think its a cheap way to pass the federal emission (leaner)."

I still believed Lotus engineers are smart to use 230cc with secondary to accomudate the federal emission, at the same time capable of delivering projected power. Imagine exporting Lotus Esprit in 50 states of United States having different emission rulling & standards? If you put 330cc or larger injectors, the car will idle lumpy and rich below 4000rpm. Most states emission test are done in the roller and run maximum of 4,000 rpm. They collect the HC, Co & NOx at this speed. Lotus will bankrupt and will not sell cars in the US if cannot meet the projected power.

Things that I don't understand: if the eight 230cc injectors are controlled by the ECU in terms of opening in close during firing stage, who control the secondary injectors? If the secondary injectors at mercy

of the ECU, you will not accomplish the projected power because it will close and open at the same time as the 230cc injectors.

My guess: the secondary injectors (although connected to ECU) are getting a 12 volts when WOT

and dump fuel as much as it can (while the butterfly is wide open) and are not subjected to pulse width we are talking.

What do I know, I am not an engineer someone has to correct me !

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Your description of how an injector works is correct... however there are two types of fuel injector -- high impedence and low impedence. The high impedence injector requires 12v to stay open and is simpler to program, but the low impedence needs 12v to open and 6v to stay open. Low impedence injectors are more efficient because they act quicker. As for how to control the secondary injectors... that would just require a secondary map. Similar to a knock map on an ecu, or a limp map, the secondary map would kick in when engine load reached 70%. If I was mapping it, i would make the primaries open at 80% dwell the entire time above the 70% load necessity and make a secondary fuel map for the secondary injectors that would be run at 0% when the engine load is 70% and run at 80% when engine load was 100%... I know it's a lot more complicated than that (one would need at least an 8x16 map to accomplish this properly).

I understand why you mentioned the fact that the injectors are operated sequentially -- fuel puddling is far worse in a constant injection system -- but I was assuming sequential injection. Fuel puddling still occurs in this type of injection, which is why you must not polish your intake ports to anything greater than 60 grit -- the air boundary layer on the surface of the port becomes too thin if it's polished to a shine and then the fuel can easily puddle because of the static air around the surface of the port.

If the injectors in the v8 are high impedence... then perhaps they are much cheaper to produce than low impedence injectors and that's why lotus used them.

I can't imagine it having to do with emissions... plenty of cars use much larger injectors with similar engine dynamics and pass emissions just fine..

I can, however imagine it being easier and cheaper to modify and play with when you have secondaries involved... I really think it all has to do more with economics and previous experience... the 4 cylinder had secondaries... so lotus was accustomed to doing it this way... so why change?

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Modifying esprit's.. now that's fun..

PS... I AM NOT A CERTIFIED MECHANIC.. I Have chosen to help those in need, in the past and must not be construed as being a certified technician.

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"As for how to control the secondary injectors... that would just require a secondary map. Similar to a knock map on an ecu, or a limp map, the secondary map would kick in when engine load reached 70%."[/i]

So, how can this be possible? Using secondary map while the main map in action or in real time?

I searched the motec and see nothing as an option for 2nd mapping.

However, there is GPO (General purpose output). GPO is where you can configure other stuff like triggering the NOS, auxilliary fuel pump control, fan thermo control, intake runner control,

shift light control, torque converter control and so on. Maybe the secondary injectors is triggered by the GPO.

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Here's what I'm guessing happens then... the secondary injectors are controlled by a secondary circuit and are opened at the same time as the other injectors but the load on the primaries is reduced... that's the only way I can think of other than a secondary map. so... when at 80% load, the primaries would be reduced to 60% and the secondaries would also be 60%... and then on from there... but that would be difficult to do because the map is not on/off... it's interpolated. The 16x16 (or 32x32) map is not written in stone.. the computer uses it to determine a value by using the 4 surrounding boxes to calculate it's actual injector open time... so if this were a switchable system without a secondary map... i don't know how it well it would work.. it would be very difficult to get the injectors to reduce their duty cycle and switch on the secondaries... i suppose it could be done by the tps and make it simply switchable at 70% throttle position and make it the open loop map... that might work... actually... i think that's the only way you could do it... secondaries are only functional in open loop... otherwise it would make it very hard to make it a smooth fuel map...

Modifying esprit's.. now that's fun..

PS... I AM NOT A CERTIFIED MECHANIC.. I Have chosen to help those in need, in the past and must not be construed as being a certified technician.

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Mark---if its true, might as well use 330cc (as you said). You are making the system complicated by using primary and seconday system by embbeding two mappings. You can accomplish the same result or better by using say 330cc in one mapping system.

I still think the secondary are just dumping fuel at WOT. However, if only dumping fuel at wot, there should be another fuel pump separate from the primary fuel pump. There is no secondary fuel pump, so I could be wrong and you are probably right. I will research and ask for more info and ask some of the gurus.

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...I still think the secondary are just dumping fuel at WOT. However, if only dumping fuel at wot, there should be another fuel pump separate from the primary fuel pump. There is no secondary fuel pump, so I could be wrong and you are probably right. I will research and ask for more info and ask some of the gurus.

as far as i can see, the V8 does have a secondary fuel pump. With parallel surge line and activated only in start up , or if the fuel flow requires more flow per minute(WOT) and high inlet temp.

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If the secondaries were simply dumping fuel... you'd have a very sharp spike in AFR when they come on... However, if they were operated as i stated earlier... it would be smooth. If you had the sharp spike in AFR... you would have a noticeable decrease in horsepower when they came on line.... as in from one throttle position to 1/4" more would actually give you a significant drop in power. Somebody at lotus must have some information as to why they do this... I really think the secondary map makes more sense then a 70% TPS Map adjustment or an on/off injector relay. The reason I think so is that if you wanted to modify the engine... it would be sooo much cheaper to modify with just changing a couple of secondaries.

Modifying esprit's.. now that's fun..

PS... I AM NOT A CERTIFIED MECHANIC.. I Have chosen to help those in need, in the past and must not be construed as being a certified technician.

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When my car was mapped to the Motec M800, the operation of the injectors was replicated, as opposed to opting for larger primary injectors and blanking off the secondaries. This was done for simplicities sake at the time. Given the chance to have influenced the outcome more, I would have asked the upgrading of the primaries, at the expense of the secondaries.

When I get the car back from the engine rebuild, I

1996 Esprit V8, 1998 Esprit V8 GT, 1999 Esprit S350 #002 (Esprit GT1 replica project), 1996 Esprit V8 GT1 (chassis 114-001), 1992 Lotus Omega (927E), 1999 Esprit V8SE, 1999 Esprit S350 #032, 1995 Esprit S4s, 1999 Esprit V8 GT (ex-5th Gear project), 1999 Esprit V8SE ('02 rear)

1999 S350 #002 Esprit GT1 replica

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Mike....

I found the secondary injectors are MAP sensor controlled, the injector pulse width is in accordance with a

certain manifold pressure and beyond.

Mark-T is right.

Makes sense, but I cannot believe that is is based on MAP alone - there must be some other parameters that are taken into consideration.

1996 Esprit V8, 1998 Esprit V8 GT, 1999 Esprit S350 #002 (Esprit GT1 replica project), 1996 Esprit V8 GT1 (chassis 114-001), 1992 Lotus Omega (927E), 1999 Esprit V8SE, 1999 Esprit S350 #032, 1995 Esprit S4s, 1999 Esprit V8 GT (ex-5th Gear project), 1999 Esprit V8SE ('02 rear)

1999 S350 #002 Esprit GT1 replica

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yes there is, Coolant temp, barometric pressure, air intake temperature, engine rpm, throttle position.....

Modifying esprit's.. now that's fun..

PS... I AM NOT A CERTIFIED MECHANIC.. I Have chosen to help those in need, in the past and must not be construed as being a certified technician.

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  • 6 years later...

Hello all,

Reviving this thread as I just got a message below from my mechanic, who is currently working on my 1999 Esprit V8:

".............. Your secondary fuel lines for your fuel injectors are plugged with JB well type of compound. It looks like whom ever worked on it prior plugged off both of these lines for some reason. The secondary fuel injector lines are used for full power and for when you do over 130 mph. What my technician suspects is that they are on all the time and that’s why your engine needed to be rebuilt before. That there was so much fuel being dumped into the cylinders that the oil wasn’t able to lubricate.

I do not know what you would like for use to do about the secondary fuel lines that are plugged. Right now the engine runs pretty good and we are worried if we clear the lines this might expose an issue with your fuel system. We don’t know how far you would like for use to dig into figuring out what is going on with the fuel system............."

So my questions are:

1. Why would the Previous owner plug the lines?

2. I should have them fix this issue, correct?

Cheers!

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I  would thin that a scanner would be able to diagnose if they are on all the time? If they are, yes, it should be fixed.

Ridiculous way to fix a problem though.

All we know is that when they stop making this, we will be properly, properly sad.Jeremy Clarkson on the Esprit.

Opinions are like armpits. Everyone has them, some just stink more than others.

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If a scanner isnt available for some reason, they should be able to use a oscilloscope or even a sensitive multimeter (with an analogue secondary guage) to see if and when the injectors are being held open or pulsed.

Agree with Michael that it seems a bizzare thing to have done, but equally the current garage doesn't seem too switched on either or they'd be offering up a clearer and more definitive diagnosis.

Chunky Lover

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The issue with the secondaries is usually that the person who re-installs them doesn't get them sealed correctly...  The secondaries are side/galley fed rather than top fed, and the sealing o-ring is apparently easy to screw up.

 

I would fix the "repair" that has been done and carefully check the o-ring seals on the injectors, replace the o-ring, and lube them before carefully re-inserting them correctly.

 

Injector_Service3_L.jpg

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Travis

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  • 4 years later...

I find it exhausting that after 30min scouring the internet for an answer, I cannot find 1 person or online shop tell me the actual "Flow Rate" of the secondary injectors? It's like you can have a 3 page discussion about upgrading them and no mention of the size....  Not even a vendor selling an injector for the Chevy S-10 side feed will have any mention of the flow? WHy so top secret, I think I may have to tap into them or get an adjustable FPR to increase the flow of the 8 Cobra injectors that are only 252cc. 

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The secondary injectors are 550cc/min.  You won't need to upgrade the size of those.

A minor increase in the primary flow, plus the stock secondaries will provide enough fuel for upwards of 500bhp.

1996 Esprit V8, 1998 Esprit V8 GT, 1999 Esprit S350 #002 (Esprit GT1 replica project), 1996 Esprit V8 GT1 (chassis 114-001), 1992 Lotus Omega (927E), 1999 Esprit V8SE, 1999 Esprit S350 #032, 1995 Esprit S4s, 1999 Esprit V8 GT (ex-5th Gear project), 1999 Esprit V8SE ('02 rear)

1999 S350 #002 Esprit GT1 replica

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 And just like that I got my answer thank you Mike    I won’t upgrade but I will have to use them somehow     

 Aeromotive sells an adjustable FPR and that’s about it for options. 

Spent yesterday Tuning the car on the road and I ran out of fuel completely at 7 psi with semi sequential firing 2 injectors at a time. 

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