what size injectors are needed to max out a 14b

[turbojo]

what size injectors are needed to max out a 14b

 

[e85_4g63]

Using what fuel? 750's will max out the 14b on gas (pump or race), for e85 you might need something a tad bigger.

 

[sprmotohooligan]

Depends on what you define "max out" as. I take it the highest boost you can run before you start to get unefficient. This should be about 21 psi on a 14B if I'm not mistaken, anything there after you are really just blowing hot air. I am running EVO IX injectors with my 14B at 21 psi and it tails off to about 16 by red line. I was seeing about 90-93% duty cycle at red line with my target AF at about 10.5-1

 

[gofer]

Its not a boost level that maxes out injectors, its the amount of airflow (cfm) the turbo can create at that boost level. After some research on the 14b rated cfm you'd find that its rated at 405cfm in the stock 6cm housing. Most injectors are rated for max airflow (lbs/min), so you'll have to convert cfm to lbs/min so you know what injectors to get.

405cfm x .07 = 28lbs/min​

Then you look at our sites tech articles on Injector and Fuel Pump Supported Airflow and you find injectors that can support 28lbs/min at 80% IDC.

Because a 1g's base fuel pressure is 37psi, you'll notice in the tech article the injectors are flow rated at 43psi, you'll want to go one injector bigger for your setup. A 660cc injector will support anything you plan to do with that 14b on pump gas, if you decide to switch to E85 you're going to have to get a 950cc injector or bigger.

 

[GSLENK]

I was going to say, 550 seems about right, maybe 650 to be on the safe side. using basic math, and ignoring a lot of complex physics properties...

The factory 450cc can handle about 12-13 psi (ish) before 100% inj duty cycle is reached. <3-4 DC at idle vac, (-1 bar) and almost 100% @ 1 bar, so you figure you would need 150% of your current flow to match 150% more pressure.

well 450*1.5=675
and 2 bar=24 psi (max effiiciency is around 21, and remember were starting at -1 bar, or about 14in of vac. this is an underestimate to keep it simple)

So thats just short of a 3 bar range. 650 is just short of 675, depending on where the 14b maxes out. Im assuming pump gas.

so keeping in mind, that you want 80% duty cycle and not 100%... I would go 650 over 550...

The next question is can the fuel pump handle it? how about with a rewire?

 

[bastarddsm]

You guys are nuts. 550's for gas, and 750's for E85. If you get over 80% idc its no big deal, just keep it under 95%, as most injectors quit flowing more there.

Christ, I made 350whp on E85 and 450's with some extra fuel pressure, and I made mid 400's on a HX35 with 750's and n/t regulator.

 

[LiquidX]

However your injectors were stuck open at those levels and will damage them. That is a poor way to alternative your AFR by adding more air to the point it leans out the mixture since the injectors cannot keep up.

Don't post bad information.

 

[Alex42590]

660cc injectors are a good choice for your 14b ill be using some denso 660's with my 16g

 

[bastarddsm]

However your injectors were stuck open at those levels and will damage them. That is a poor way to alternative your AFR by adding more air to the point it leans out the mixture since the injectors cannot keep up.

Don't post bad information.

Stuck open? What are you talking about? A quality injector like a open 450 maintains its ability to Open and close untill about 95% idc's on a 1000hz square wave. Thats equivlent to the engine turning 120000RPM.

Hell even a junk bosch 1600, can do it until 90%.

So what work have you done to verify that I am posting bad information? How many sets of injectors have you flow tested? How many sets of 550's have you even got close to 80% idc's on a 14b?

Oh buy you'll say that the lower bfp of a 1g makes them really really small. It makes the 7% smaller. So your 550's flow like 510.

Still good enough for 28lbs/min at 80%idc's.



I suggest you stop posting bad information.

 

[e85_4g63]

The reason I stated using 750cc injectors was to keep the IDC's down under 80%, which is considered the industry standard maximum IDC. If anyone feels the need to run there injectors over 80%, kick your own a$$ when your motor dies. If your to cheap to do it right, you deserve what happens to you. Injectors are (for the sizes we're talking about here) under $400, a short block on the other hand is $1,500+

 

[TJCTalon]

Im running stock 450's with my 14b running 18 psi. I have every supporting mod, and at stock fuel pressure I was seeing 85 idc. Stock Injectors with a fuel weight 2g and a shitty launch trapped 95 MPH in the quarter at my altitude.

People under estamate the stock injectors. Granted Id only suggest pushing the stock injectors when you have a logging defice to monitor everything, as it is dangerous to run duty cycles that high.

 

[jrohner]

You guys are nuts. 550's for gas, and 750's for E85. If you get over 80% idc its no big deal, just keep it under 95%, as most injectors quit flowing more there.

Christ, I made 350whp on E85 and 450's with some extra fuel pressure, and I made mid 400's on a HX35 with 750's and n/t regulator.

+1

E85: 414/459 on RC750's with my 2G.


It depends on what you're tuning with too. With an AFC, you still have to deal with stupid fuel cut, where tuning with EPROM, Flashing, or Link you don't. Also, if you're trying to run the stock crappy rich fuel mixture, you'll need bigger injectors. E85 you can go pretty lean which helps a lot; no need to tune 11 or even 11.5:1 usually.

 

[bastarddsm]

The reason I stated using 750cc injectors was to keep the IDC's down under 80%, which is considered the industry standard maximum IDC. If anyone feels the need to run there injectors over 80%, kick your own a$$ when your motor dies. If your to cheap to do it right, you deserve what happens to you. Injectors are (for the sizes we're talking about here) under $400, a short block on the other hand is $1,500+

. If you puke a motor while running idc's over 80%, something else was severely wrong.

80% is an old school limit because old (early 80's design) injectors would not flow anymore over 80% because there internals were so heavy that they were allready static at not much more than 80%. Modern injectors like the ones we use today reach this point at about 90-95% idc.

 

[turboglenn]

. If you puke a motor while running idc's over 80%, something else was severely wrong.

80% is an old school limit because old (early 80's design) injectors would not flow anymore over 80% because there internals were so heavy that they were allready static at not much more than 80%. Modern injectors like the ones we use today reach this point at about 90-95% idc.

I have to say i some what agree, i constantly run my IDC's over 80% (more like 90-95%) and never have issues, i think a lot of it is in the tune as well as some of it being that newer injectors are improving as bastarddsm said

on the other hand and on topic, i'd say 550'swould probably do it maxed out, 660' would be safe and 720's would be really safe and allow you to do it on e85 as well

 

[clipto]

I had my 14b at 15psi and was running 550cc injectors at 70% idc with a 11:1 a/f ratio on a crummy safc.

 

[turboglenn]

I had my 14b at 15psi and was running 550cc injectors at 70% idc with a 11:1 a/f ratio on a crummy safc.

damn, then that thing (or your setup in general) was really flowing well. I ran a normal big 16g on RC550's for a short time before i went all out and got into the 21-25psi range with AFR's in the mid 11's low 12's on race gas and wasn't in that much of a DC.. I think IIRC i hit 85-90% on it with 21psi and 11;1 AFR on pump gas though.. of course i had a nice wally 255 in there to feed it too

RC states the 550's to be good to i think either 325 or 350hp at 85 or 85% IDC (haven't seen the papers that came with them in years as i sold them over 10 years ago to a buddy's CRX project that embarrased my DSM by going 11.4x's on a broken first gear launchingin 2nd, with a stock 155k mile 1.8ls engine and trans from the boneyard..only things it had were a welded up drag manifold to hold a t3 turbo from the boneyard, my 550's and old AFC with a good 255pump and slicks..oh and a good clutch and being gutted.. i STILL haven't hit low 11's and have more than enough power too and that little car broke first on the line but didn't trip the light, re-launched in second and bamn, caughtt eh 14 second camaro next to it and did 11.40's efore we trailered it home)

 

[Bud92gsx]

Did anyone else notice the OP has NO mods?

 

[turboglenn]

either that or hasn't filled it out like he should.. not sure, but just thoughti'd answer the title question

 

[Bud92gsx]

I gotcha glenn..I've been following along, and thought I would mention it..

If the OP does have mods FILL OUT YOUR PROFILE PLEASE?

 

[turbojo]

I gotcha glenn..I've been following along, and thought I would mention it..

If the OP does have mods FILL OUT YOUR PROFILE PLEASE?

i just did

 

[gofer]

You guys are nuts. 550's for gas, and 750's for E85. If you get over 80% idc its no big deal, just keep it under 95%, as most injectors quit flowing more there.

Christ, I made 350whp on E85 and 450's with some extra fuel pressure, and I made mid 400's on a HX35 with 750's and n/t regulator.

Here's why I disagree. When you start seeing around 89-93% IDC (depends on injectors and your fuel pressure of course), the injectors will usually stick open, giving you the equivalent amount of fuel if the injectors were running at 100% duty. This typically results in a rich spike in the AFR curve as soon as the IDC reaches the point where the injectors stick open, 89-93%. I saw these on my FIC 950's pretty consistently at about 91% IDC, and still do. It can be tuned out but its a pain in the dick and its never consistent, so why do it?

What you guys fail to mention is everything else required to run your injectors to the limit like you do, a new DSMer can interpret your posts incorrectly and blow a few hundred on injectors that are WAY too small for their setup. Just because it worked for you two it doesn't work like that for the masses, and even I can't figure out how you stretched your 750's, on 47psi bfp, to support that amount of whp Kurt.

E85 Calculated Flow
750cc x 0.67 = 502.5cc

502.5cc injector on bfp of 48psi, stock 1g N/T (assuming M/T) bumps them to a 528cc injector. So, you're saying that you had a 530cc injector supporting 45lbs/min (possibly more), what were your AFR's then 13.5:1?

The numbers don't add up or your a DSM magician, and if thats the case, I'll buy you plane ticket to fly out here and make my 950's support as much airflow on E85 as your 750's.

I'm not trying to start an argument, so please don't post a smart ass response. I see you post in nearly every injector thread we have about stretching small injectors to support WAY more than I ever thought possible, educate us on how you do it... If you convince me maybe I can sell the 2150's I have in my garage and get a set of 1350's.

turbojo I deleted your avatar because it was against our sites rules, it must be a photo of your DSM.

 

[Hal]

educate us on how you do it

Adjusting fuel pressure is one way to do it.

Remember when the IDC1000's first came out and some people were running them at 100 psi base?

Hal

 

[turboglenn]

Gofer, good disclaimer/catch about our opinions on IDC's.. i guess there's so much knowledge on this forum i just some how "expect" everyone has their car up to snuff using things properly and knows more than they maybe do.. And when some one asks about maxing out a 14b i automatically think they're dropping into something small and going for some small turbo record My bad, BTW, i ALWAYS suggest getting a size larger than you think you want on injectors, i went from 550's to 750's in a 3-4 mnth time, then to 1000's barely much after that

 

[gofer]

Adjusting fuel pressure is one way to do it.

Remember when the IDC1000's first came out and some people were running them at 100 psi base?

Hal

Thats a good point Hal, Kurt clearly stated 48psi base (stock 1g N/T fpr) though, which is why I asked. Thats how I stretched my 950's to support 47lbs/min on E85, I had to kick my bfp up a bit.

What you posted Glenn seemed plausible, 550's will support a 16g @ 21psi with a big fuel pump, which you mentioned in your post.

 

[LandSpeed-DSM]

bastarddsm shared a PM with me from another thread and as I suspected he runs BFP through the roof, to the tune of 60psi BFP.

But what he neglected to follow up on, at least in the thread was the pump setup.

Which is crucial if you intend to go this route, maybe he is just spoiled by diesels ;D

Most pumps, especially a single intank pump, are not going to be able to carry you too far at that BFP. 20psi on top of 60psi is beyond the crack pressure of the relief valve on many common EFI pumps.

Some combinations, like a 255HP intank and a Bosch 044 in series pump can support this, but it is quite a qualifier, and something that should be posted if we are going to discuss the IDC and airflow support of something like a 450 stock injector.

I have logs showing well north of 100% IDC at 30lbs/min on a 14B, and a couple at 120% nearing 35lbs/min.

Yes a 14B flowing 34.x lbs/min. In any event running small injectors to the ragged edge is not worth it if you are worried about streetability with large injectors.

If you are that concerned, you have other saner options. But they cost money. Still cheaper than a new engine. Dependent on how much air you plan to move or what fuel you will be using you also have the option of running a single set of Hi-Z 2150's or run the 450s as the primaries with a secondary rail with some big boys.

This way you will still have stock idle, part throttle and cruise but enough to support real power up top.

Trickiest part is setting up your new map in link via the secondary fuel tables. Many places can mod your intake manifold to put a second rail on.

Anyways for a 14B on kill mode for pump gas I would run at minimum a set of Evo 560s or 660cc injectors and for E85 I would just go straight to 850s. This way if you step up to a 16G you will still be mostly covered.

Unless you are Curt Brown. But if you are Curt Brown you aren't coming to this thread for advice, so don't be a cheap ass and just buy some injectors that are comfortably up to the task.