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Discussion Starter #1
Is it possible with larger injectors to run a small light boost 6-8 psi on stock system?

Thanks
 

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Acme Super Moderator ** The Enforcer **
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Is it possible with larger injectors to run a small light boost 6-8 psi on stock system?

Thanks
I wouldn't advise it without a tune as it will be lean, and without an intercooler you'll just be compounding the problem (higher IAT, proclivity to knock, ECU pulling timing, etc.). Just installing larger injectors doesn't mean the ECU will learn about the increased injector's size, the need for more fuel, the A/F ratio, the turbo and so on.

You'll need a new exhaust manifold to route the exhaust gases to the turbo, a wastegate, exhaust piping from the turbo, consideration of the pre/post cat sensors, added heat, oil and/or coolant feeds for the turbo and a slew of other things. You have to realize this motor wasn't built for boost, and with the already high compression ratio, you'd be wise to properly engineer a complete system, not just add a turbo and larger injectors and think all will be well. You really need the advice of someone extremely competent, which rules me out.

San
 

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Discussion Starter #3
Thanks, yes. Many things.
Has anyone had success with a light pressure system?
I dont need to race, though I live in the mountains and boost sure is nice.
Even if it is only 6-7 psi. That seems to be enough force to help with the hills!

Kind Regards
 

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The stock supercharger is roughly 6psi. Why not buy a SC solution including a tune?

Sent from my Pixel 3 using Tapatalk
 

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The Forced Fed system runs about 8psi and work perfectly well on a stock engine (bunch for sale recently on LT).
You do need a tune! Don't mess with this. BOE has lots of experience and can help.
You can run less boost if you want, boost is adjustable so go with a Garrett 2860RS or something like this.
Perfect size for the Lotus.

The nice thing is if you want to go faster in the future you just turn up the boost button. :grin2:


Thanks, yes. Many things.
Has anyone had success with a light pressure system?
I dont need to race, though I live in the mountains and boost sure is nice.
Even if it is only 6-7 psi. That seems to be enough force to help with the hills!

Kind Regards
 

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Discussion Starter #6
Cheers
Ied most likely add some rods it the boost be turned up beyond 8
12 seems to be a nice goal. When the funds allow for rods etc
Thanks LT
 

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I run force fed kit and like it. FF kit would good start

BOE does not tune turbo cars last time i checked. This is big project. if you do it you will need be somewhat skilled mechanic and do work on the kit, few people have the skill to do it right. DRS will do these setups and does good work.

just few things you will.
===========
new fuel pump
some type of tune or standalone ECU
clutch
injectors
blow off value
oil pan
 

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Discussion Starter #10
Yes 05 2zz
I have updated the tank and pump to a quantum
Think the Injectors need to give a bit more?
Thought the stock system would meter the need for added fuel, this i dont know how much? Question is, what has been done successfully please
 

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Acme Super Moderator ** The Enforcer **
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Yes 05 2zz
I have updated the tank and pump to a quantum
Think the Injectors need to give a bit more?
Thought the stock system would meter the need for added fuel, this i dont know how much? Question is, what has been done successfully please
I have the Blade 300, which adds more boost with a smaller pulley. It uses 550cc injectors and a tune, upgraded IC and the Cup airbox.

Before the kit my AFRs were right at about 14 to 1 across the rpms. That leaves little room for error (bad gas etc.). After the kit and tune were installed the AFRs were more in line with boosted tunes (richer, especially at high rpms). You could squeeze out more power with a custom tune, but my mechanic thought I should leave it where it was. It also provides a bit of headroom for bad gas, etc.

The BOE kits have 750cc injectors. Granted, their blowers are capable of more boost, but part of my point is that with my kit and others, you typically don't add boost to a stock motor (especially one with high compression) without compensating with more fuel (bigger injectors, fuel pump etc.), intercooler, tune to manage the AFRs etc. You may get away with, you may not.

You can obviously add whatever you want, but at a minimum I'd do some dyno pulls to see if your AFR is sufficent for the boost you add.

Just my opinion, and everyone has one.

San
 

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Yes 05 2zz [...]
Thought the stock system would meter the need for added fuel, this i dont know how much?
as far as i understand, most of the load axes in the calibration for the N/A '05 elise top out at about one cylinder volume equivalent (658 mg, likely used reduced temperature and pressure relative to STP) air per stroke. so any volume beyond that would not be properly calibrated.

the fuel trims may help add some fuel to compensate, but these also have limits before throwing an error code.

when the injectors are modified, then i guess the values in the ecu would not be explicitly correct.

I guess that you'll have to try it and make adjustments to really see what happens.

in case you're willing to take an electronics risk, I've written some code to help reflash the '05 ecu after editing a rom in romraider.

https://www.lotustalk.com/forums/f171/notes-about-2005-elise-fueling-timing-control-463664/

https://github.com/Obeisance/Daft_LotusT4_OBD
 

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as far as i understand, most of the load axes in the calibration for the N/A '05 elise top out at about one cylinder volume equivalent (658 mg, likely used reduced temperature and pressure relative to STP) air per stroke. so any volume beyond that would not be properly calibrated.

the fuel trims may help add some fuel to compensate, but these also have limits before throwing an error code.

when the injectors are modified, then i guess the values in the ecu would not be explicitly correct.
If you don't know, the reason that 'everybody' doesn't just put bigger injectors in to begin with is because higher flow rate injectors have worse metering at very low volumes, which makes it hard to get good idle emissions and good low RPM/light load fuel economy. OEMs always fit the smallest injector that will do the job with the stock tuning for this reason.
 

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Discussion Starter #16
Anyone know if stock injectors will support 7-8psi?
Or, is it simply easier to add one or more injectors in the plenum. Running off a second computer, or. Same computer, and a rising rate fuel pressure regulator?
Will a barometric pressure sensor, controlling another (or sixth) injector get close?

I will not be racing, simply climbing hills behind RV’s and Logging trucks. Really dont need a bunch of boost. Don’t care much for the second cam. As low rpm boost is fine, free power.

Innovative wideband installed.
 

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Acme Super Moderator ** The Enforcer **
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Anyone know if stock injectors will support 7-8psi?
Or, is it simply easier to add one or more injectors in the plenum. Running off a second computer, or. Same computer, and a rising rate fuel pressure regulator?
Will a barometric pressure sensor, controlling another (or sixth) injector get close?

I will not be racing, simply climbing hills behind RV’s and Logging trucks. Really dont need a bunch of boost. Don’t care much for the second cam. As low rpm boost is fine, free power.

Innovative wideband installed.
You keep asking the same question, but don't seem to be listening to any answers. I don't think anyone said low rpm boost is fine. Nothing is free.

If you ask 100 people if building a house on stilts next to an often flooding river is a good idea, and 99 say no, but 1 says yes, would you build the house?

It seems like you're looking for one person to reassure you that your proposal is sound. Best of luck.

San
 

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that question got me wondering if i could calculate injector requirements..

i assumed the ideal gas law, fuel density and AFR. I did not account for the short window in engine position where the injectors have to deliver their fuel.

I also read on the forum that the stock Elise injectors are 300-310 cc/min.
https://www.lotustalk.com/forums/f160/injector-sizing-53358/#post948573

Then i made some plots of various required injector volume rates at constant manifold pressure under these simple assumptions.

I think the stock injectors would be working really hard to keep up if you add much more air.
 

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Discussion Starter #19
That is again very helpful Obeisance
I will have time this winter to modify things, or send electronics out.
Cross boarder shopping is difficult, and there are no tuning places near.
RomRaider is interesting, and maybe the best option. If a simple, low boost option does not come knocking.
Some 70’s and 80’s cars have “Cold Start Injectors”. These can be made to turn on without too much. Don’t know if simply open, and a rising rate fuel pressure regulator would add enough. Speculation anyone?

If you don't know, the reason that 'everybody' doesn't just put bigger injectors in to begin with is because higher flow rate injectors have worse metering at very low volumes, which makes it hard to get good idle emissions and good low RPM/light load fuel economy. OEMs always fit the smallest injector that will do the job with the stock tuning for this reason.
Are larger injectors considered 550+? I suspect most folk who are adding boost, are going big. Race track stuff.
Low RPM injector flow in a 320-350 injector may not be so poorly metered?

Has anyone added one or two injectors, to add extra fuel at boost?

Thanks LT
 

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Take a look at my full build log for boosting a 2ZZ. I would recommend you don't skimp on the fuel delivery and ignition control. With Forced Induction it doesn't take much to have things go horribly wrong, especially with the stock internals and the high compression. I'm not running huge injectors Siemens 630cc at 49psi and they behave at lower rpms fairly well. I have seen a lot of really cheap budget turbo builds and they dont last long. The engines that are built for boost (correct compression\charge cooling) and proper (fuel/ign/wideband) control seem to keep running for years. I always say, Do it right the first time, or you'll be doing it again.
 
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