In response to earlier posts by Dingy and Craig - have learned by the long hard road that 740cc injectors are overkill. 550cc will be the most needed on the majority, if not all 2L cars (OK I am sure there will be some 450bhp plus monster out there )

Basically the standard fuel pump (STI - so assume UK cars even worse!) will not produce the appropriate fuel pressure over 1 bar of boost.

Uprated pump - remapping only required over 1bar boost (consistent with others experience) - and hey presto car runs MUCH better and IDCs are down to around 65%. Peak torque is hugely improved, the engine is quieter - no doubt due to efficiency, better injector timing and better spray pattern. Expect better RR results.

Historic linkage (excuse the pun) with Link tuning and 740s is that a lot of early LINK tuned cars did not go for the uprated pump!

So humble pie is now eaten.

Now a question - any injector experts out there - should I now change for 550s to get better granularity? Or just stick with the 740 in case I build a monster one day?

Trout

 

At the price of injectors, do you ever want to be left short of fuel for future mods ?? It would be a very expensive upgrade to do twice, if it became necessary. A friend is running 740's + FSE fuel pump on his car, and there seems to be no difference in response and drivability down low compared to std injectors ( 440cc yellow sti injectors ) They were Nizmo items purchased thru scoobymania. They are a direct swap, although the wiring plug is different even tho they claim a straight swap. We got wiring plugs from a nissan primera, and joined them to the subaru loom.
Currently with 1.5 bar, Pace FMIC, HKS GT Turbo Kit, Motec we are seeing duty cycles of around 65% at 7000+rpm, which is at around 11.4:1 AFR
Not sure how 550cc would be coping with same. Need more power though

[Edited by ustolemyname??stevieturbo - 5/23/2002 1:24:27 AM]

 

Interesting that we now have similar IDCs - although consistent that we are running similar boost etc.

In terms of the Nismo plugs - they can fit - you slice off one of the lugs - very obvious and very easy with good blade - and then you shorten the injector collar by about 3mm - again with a very fine hacksaw and the Scooby plugs fit perfectly

Will stay with the 740s unles someone says that a 550 running at 90 odd % would be a better set up. Idle is not easy tho!

Trout

 

Trout

[Flame suit on]
Running your 550's at 90% means that you will not be in full control of them, and you have very litle spare capacity. Ideally, you should not exceed 85% IDC and even at this point will be suffering from worse mixing than at lower IDCs.

However, running larger injectors will mean that you may find trouble getting the idle and low speed running sorted. Certainly, this was a problem in the late 80's although things may have improved now. At that time Cosworth cose to go the extra injector route for high power applications with the extra injectors only kicking in for higher power ratings.
[Flame suit off]

Duncan

 

David,

I knew you'd get it in the end

can I say - I told you so?

 

Trout,

not being a mapper, I dont think I am qualified to recommend either way, but then since when has that ever stopped me?

I would say on this one, I would ask R19KET's or Pats opinion, but my instinct would be to change down to 660s and failing that, 550s, from as you say, a granularity point of view.

550s would equate to an 87.5% IDC, which is only very slightly above what they say is the ideal maximum. Plenty people including yourself have run in excess of that in the past for sustained periods, so long as you know the risks which I am sure you do.

I dont consider 87.5% to be in a danger zone at all, and for the rest of the benefits I would change. It will yield a better map, plus it gives you the chance to play come more. Saying that though, I would be more inclined to upgrade to motec or pectel from where you are as having looked into it I can see all the benefits now.

I dont know how many upgrade paths are left on your car without going internal so how much headroom do you need? on top of this, the second hand prices of injectors make 550s a more valuable asset than 740s as you have stated, very few people will ever need them, unless they are a bit stupid! .

Worse case scenario you can always up the fuel pressure a tiny amount if you need any headroom at all, it will be more than enough freedom, and we know the uprated pump can handle it without batting an eyelid.

 

If your max idc/ipw is at your max rpms, in top gear, and you're still only peaking at 90% I wouldn't worry about it.

Through the gears, you'll only be touching it for a tiny period, and even in top, it's only likely to be for a very short period of time.

To be honest, I've not tested the spray pattern of different injectors, at the same fuel pressure, at comparable flow, but personally, If I had a choice, I would go for the smaller injector, and if I was getting a little close for comfort, increase the fuel pressure, as Adam suggested.

Mark.

 

Sorry,I know its off topic but does anybody know the size of the pink injectors on the STi7.Cheers,Deep.

 

Deep - about three inches?

Trout

 

PS Adam you are quite right...............



..........you are not qualified to comment

 

LOL @ Trout

Deep, JDM or Type UK? I know they have different spray patterns(the UK is multi-hole) but don't know if they are the same size....

Sorry to hijack your thread Dave but Deep started it...

Matt

 

I may not be qualified to comment fishman, but what I said holds some water does it not?

admit it, you have been advised by me, and it hurts you!

BTW, still sitting on my replacement brake pads, months later. Arent you lucky I chose to buy them when I did!

 

Trout 3 inches in girth if your're talking about me matey.Ask your missus if you d'ont believe me(LOL)
Matt I meant JDM,trying to ascertain from this thread whether injectors would have to be changed to get about 330 BHP from it.
ps sorry for hijacking the thread again.

 

Deep m8, any news on the NF???

Jacko.

 

Basically the standard fuel pump (STI - so assume UK cars even worse!) will not produce the appropriate fuel pressure over 1 bar of boost.


Does that mean when running a Dawes at high boost - 16psi, the engine is being starved of fuel?

Steve

 

nothing to do with dawes or not,

running anything over 1 bar, trout is suggesting the standard non sti fuel pump may struggle.

 

OK I'm only stating from my experience but my car (UK MY94) runs very rich at 1.2bar and has done for over two years.

 

I've gone down the route of increasing injector size (haven't I Adam ) and found the following.

Car is a MY94 WRX so started with 380 injectors. These were good enough for about 295 bhp with standard fuel pump, induction kit, straight through exhaust and PE Phase 1 remap. But after an engine rebuild could not extract any more power as the IDC was 97-98% and standard top mount intercooler was struggling. So fitted a front mount intercooler, changed to 440's and remapped again. This gave 330 bhp but still with IDC of 95%. So uprated fuel pump and fitted 550's. Still running about 330 bhp, 300 lb/ft, at 85% IDC, on 1.2 bar boost.

Hope this helps

 

Darren,should get to me on Friday.I'll mail you mate.

 

Deep,

From the data I have to hand, it looks like the STi 7 injectors are are likely to be just about good enough for 330bhp but I need to check a couple of things with Jonno.

Matt

 

It may have crap injectors - but still corners well!

Adam - was only having a bit of fun mate!

Also my data suggests I was getting over 300bhp with 440 injectors running 117% IDC!!!!!! It is possible

Running 1.2bar may be fine - it depends how much you are near the limit of airflow etc - it was only a problem on my car once I uprated the turbo. With standard turbo there was no obvious problem and in reality the problem only really came to light on track.

However on road performance is hugely improved!

Trout

[Edited by Trout - 5/23/2002 11:56:02 PM]

 

david,

so was I!
couldn't you tell?

You should know how thick (skinned) I am by now!

 

Mo,

there is also the fact that 1.2bar on a td04 for example requires much less fuel than 1.2 bar on an MD195 for example. Kinda like what trout said above, only more concise!

 

Adam,



Thick yeah you should be skinned mate

Trout

PS Me concise - never!
PPS By the way you were lucky you sold me those pads - they were the wrongs size!!

 

you what?

wrong size!

explain.

what were they for?

despite being the wrong size were they sufficently hard to hit mike tuckwood over the head with them?

btw. all this 350bhp stuff is getting boring, i think you should change ecus, and go internal!

 

Adam,

there were for six pots - but not the slimline version that we use on the Scoobs - essesntially they were about 0.5mm too thick - which does not sound like a lot - but when they won't go in the ******* calipers it is a lot

Resorts to grinder and hammer!

Trout

 

blame mike, he sold them to me.

I hope the ones I replaced them with are the right ones!

 

I upgraded the grey injectors on my '93 RA to 740cc Apexi's.

It was really rough down low and took quite awhile to get tuned properly, but once complete it runs fine. Peak IDC is 50%.

Here the 550's were the same price as the 740's so thought I might as well future-proof myself against the possibility of needing to upgrade further later on.

If you already got 740's then stick with them, not worth spending more money and ending up with 3 sets of used injectors.

 

Adam M says: Adam we haven't heard about your car recently! Dare I say it that you car isn't making over 350bhp at the moment, if at all!!!

 

Spurner, how much did you buy them injectors for? Would it fit a standard MY92? Just curious.