View Full Version : big injector problems
whats the downside to fitting big injectors, eg 850's??
I believe it's trickier to get a nice smooth idle as it's tricky to fine-tune to injector pulses to only let through the right amount, as opposed to too much - basically, the bigger ones being almost *too* big.
I've heard it said that the ultimate is to have two banks of injectors, on set large one set small, with the small ones handling cruising/idling/MoT/etc, but as the boost climbs bring the 2nd bank online too feed the giant turbo you'd have fitted if you could afford 2 banks of injectors and the subsequent mapping :D
This could of course all be complete bollocks and I'm talking out my arse (again) :D
MONKEYmark
30-06-03, 01:19
what you planning. just nosey.
wont you need all fuel computers or ecu.
you changing all the fuel system?, got this off boostlogic site of there fuel system kit and all parts.
Boostlogic website (http://boostlogic.com/MKIV_kits.html)
Boost Logic MKIV Upgraded Fuel System
Greddy 720CC Injectors
HKS Fuel Rail
Dual GSS341 Walbro Pumps
Aeroquip AN fittings and Braided lines
Aeromotive -10AN Fuel Filter
Aeromotive -10AN Fuel Pressure Regulator
0-100PSI Fuel Pressure Gauge
6 Injector Piggytails
Necessary Relays and Power Lines
Installation Instructions
Your Price:$2100
have a look here too thought it might be of some use (bet you have read up about it all knowing you)
powerhouse racing fuel systems (http://www.powerhouseracing.com/fuel2.shtml)
If you have whopping great injectors you'll find that to avoid running hugely rich at idle you'll only want them to be open for a tiny percentage of the time. This means you need a really good pulsewidth resolution from your management setup. Shouldn't have a problem with 850s if its been mapped properly and you have a decent ECU setup though, I think you can get a nice idle out of 1000cc injectors if you do it right. I've got 680s fitted (up from 440 originally) just using an SAFC for mapping and it idles perfectly, no problems at all with em. It ran like an absolute bag of shit before it was mapped though (by Leon). I just took about 30% from my previous 550cc map to get it to run and it was horrible to drive. So find someone good to map it and you shouldn't have a problem.
There is a minimum opening time for injectors (dependent on type) and it is this that can cause the poor idle. All the electronics in the world won't help you if the physical properties of the injectors are against you.
the reason im asking is, apex (japan) have recommended 850's. they said that it's a very common next size in japan and have been tested with the powerfc. It just seems a bit massive to me. but then again 550's dont really seem to b worth the effort.
Originally posted by MONKEYmark
wont you need all fuel computers or ecu.
yes, already got.
It all depends on your ultimate goal. I never hurts to have a lot of injector as long as it will idle OK. The thing is the stock line is too small to support 850's at full chat, but you could always upgrade that later.
i would have no need for anything like full chat 850's. apparently rx7 secondary injectors will fit the supra rail with a little modification.
when does the stock rail become a problem?
With twin lines about 1000+ bhp;)
Gaz Walker
30-06-03, 11:13
Originally posted by Terry S
It all depends on your ultimate goal. I never hurts to have a lot of injector as long as it will idle OK.
Yup. No point in really going for 550's if you've got the other things to support these babies.
Gaz.
ahh, so the only reason folk get new rails is to open up the injector option?
when does the stock line become a problem?
It depends how much fuel pressure you want to run.
The only reason I can see for changing the stock rail is a larger choice/cheaper injectors. My car made 690 bhp with the stock rail & twin feeds. No sign of a problem.
The reason I went stock rail is that the stock rail takes side feed injectors. All the aftermarket ones don't. There was a reason Toyota used side feeds & not top feed. I trust Toyota more than any tuner!
what injectors u got in the rail?
Originally posted by Keith C
I believe it's trickier to get a nice smooth idle as it's tricky to fine-tune to injector pulses to only let through the right amount, as opposed to too much - basically, the bigger ones being almost *too* big.
I've heard it said that the ultimate is to have two banks of injectors, on set large one set small, with the small ones handling cruising/idling/MoT/etc, but as the boost climbs bring the 2nd bank online too feed the giant turbo you'd have fitted if you could afford 2 banks of injectors and the subsequent mapping :D
This could of course all be complete bollocks and I'm talking out my arse (again) :D
A twin bank of injectors are used on the Sierra RS500, although they were never plumbed in from factory for road use. Al.
Originally posted by Terry S
You a copper?
look, just answer the questions, then u can go home.
Originally posted by Terry S
The reason I went stock rail is that the stock rail takes side feed injectors. All the aftermarket ones don't. There was a reason Toyota used side feeds & not top feed.
I trust Toyota more than any tuner!
If what I have read is correct side feed injectors run cooler than top feed and are less likely to lock at high duty cycles.
Originally posted by GavinL
If what I have read is correct side feed injectors run cooler than top feed and are less likely to lock at high duty cycles.
That's about the size of it.
size of what , his truncheon, do the injector pulses make any difference to the brightness of neons and chrome ????
John:flame Dev
P1ss off back to suning yourself.
Also change your location in your profile.:innocent:
Sorry , new location Port Banus ;)
like the man said, piss off back to sunning yourself ... LOL :p
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