CraigH

This "may" have been covered before.......infact I think it has for defo and I can't be 4ssed to check , but...........

I would LOVE to know why cars with 330ish HP are supposed to need 740cc injectors?

I thought a vague test to determinee what injectors is times the injector size by 4 then divide by 5 and you have the rough max HP?

If so, surely std injectors are good for 350hp?

But maybe the pump isn't?

If so, does this mean certain tuners would prefer you buy sets of injectors rather than a cheaper fuel pump upgrade?

740cc injectors for <350HP is ridiculous surely?

SecretAgentMan

*LMAO*

Well put matey.

/J

R19KET

Craig,

The equation you are using, uses the recognised "average" 5cc's of fuel per 1 bhp.

If we assume that 5cc's per 1 bhp is close, then 440cc injectors would be at 100% idc, at 350bhp. So it would be recommended to go to 550cc injectors, which would then be running a theoretical 80% idc.

It's hard to compare the Subaru injectors, with let's say Cossie injectors, unless both were to be tested, and compared on a flow bench, because we don't know if are both are rated, using the same, or different systems (static, or dynamic).

However, I would agree that 740cc injectors, on cars running circa 350bhp, would seem ridiculas.

That said, Links consistantly run high idc's, and when I ran a Motec, I was maxing out the 550cc injectors too. This would infer that I was running close to 440bhp, which I don't believe. The Motec fueling was consistant at .87 volts, so it was only slightly rich.

On the bench dyno, at 6000rpm, my injectors were running at 90%, and based on the 5cc's per 1 bhp, I should have been at 85%, so it seems pretty close, but then I'm running Cossie injectors, and a VERY uprated fuel system.

Mark.

CraigH

So Linked cars give the impression you need bigger injectors than you actually do?

Hmmm.

Do the main Link tuners recognise this fact?

Richie1

You dont want to go above 85% IDC.

All it takes is for a very cold day or a slightly blocked jet and your engine cant inject enough fuel to cope then you're running in the dangerous lean area

steve McCulloch

Edited

[Edited by steve McCulloch - 3/28/2002 11:06:15 PM]

[Edited by steve McCulloch - 3/28/2002 11:07:07 PM]

Bob Rawle

I've heard it all now.

Injector duty on my M800 or M48Pro is about the same as on my Link V5 ... 74%.

When I ran 440's it was up to 126% on both. (7000 rpm and 1.3(ish) bar)... but 126% of what you should ask.

What's your point Craig ?

Injector duty needed is as much about injector timing and ignition dwell as anything ... work it out. I know what injector timing the Link uses, and ignition dwell, its not at all different to any other product ..... the "number" is also clearly dependant on what criteria you use to measure it. Since most ecu internal calculations take the start to finish of the applied pulse that does not take into account the time to charge the injector coil ... so the actual injector time will be effectively less.

As Mark says 550's are clearly inadequate .... 740's are next up. Depends where you are going.

BTW I got more than 330 using stock 440's (PE rollers)



[Edited by Bob Rawle - 3/28/2002 10:44:29 PM]

Harry Potter

I am waiting to have my 850cc injectors fitted to unleash the beast.

Mark eat your heart out

R19KET

Harry,

"Eat my heart out" Why ?. 850cc's are quite cute. My injectors are a fair bit smaller than yours though, but I run a few more than you

What I don't understand, is that The Link, and the Motec both seem to either use more fuel, or show higher idc's, than either the Gems, or the Pectel.

The Link, and the Motec seem unable to run the Subaru 440cc, or 550cc injectors anywhere near 5cc's per 1 bhp. Where as the Gems, and the Pectel don't seem to have this problem.

550cc injectors should be good for well over 400bhp, and I don't know anyone running anywhere near these figures, let alone needing 740's. I think this was Craigs point too, although I don't agree with his "possible" conclusion.

Mark.

Trout...

Craig,

it was covered before and the conclusion was - what is the point of your question?

If the car the running appropriate lambda voltages with the 740s then is it an issue (ok other than wasting a bunch of cash on injectors - I mean people on here have been known to spend in excess of 10k for not much power - so it doesn't seem too expensive to me).

Also - if it is a fuel pump issue then why would fitting bigger injectors resolve the problem?

So why the vehement challenge - I know you are a lovely mild mannered man

Trout

CraigH

Wasn't having a pop at anyone in particular.

However, "if the cap fits....."

Bob Rawle

I thought you were asking a technical question, glad you cleared that up.

CraigH

Bob,

Not exactly a technical question more wondering why, as Mark says, GEMs/Pectel seem to report IDCs differently to Link/Motec.

I know it's not quite this simple, but the EVO in Banzai this month with a claimed 550+ hp (it's 1/4mile terminal speed backs it up if the figures are true) only runs 1000cc injectors.

So why would a sub (being generous)400hp Scoob need 740s?

Like I said, I'm not having a pop so theres no need to be so defensive. If I was gonna have a pop at you I'd be more blatant.

Neil Smalley

This probably ought to go to drivetrain, as the info will probably get swamped by general in a day or so and we'll never find it again.

firefox

Probably not relevant, but.....

Take into account what Bob has previously said, not quoting him, but Cossies run low impedance injectors, where as scoobs run high.
This definately affects the characteristics of the flow/pulse of injector.

So does the design of the injector and its associated firing circuitry... hence why Pectel/Gems can "fire" (signal/contro) injectors better than say Link/Motec.

This was all cover on the i-club with Shiv, and how his ECU option (Tec-II) can control injectors in relation to others.

Fundamentally like Mark says if you can standardise on the ECU (signal generator) and the fuel supply system, then the injectors ratings should be the same .. 85% at 3 bar.

Dont forget this 5cc per BHP is approx, it will depend on several factors BSFC, VE, etc...

Anyway.. I'm off to dig up a drive way.

Tara.

J.