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Location:
Auckland, New Zealand
Registered:
October 2002
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larger injectors with factory ECU?
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Sun, 02 March 2003 22:26
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I have a question about installing larger injectors on a factory ECU. Will this basically increase fuel delivery across the rev / boost range, hence making the car run rich at idle / cruising hence using a lot more gas? Or does the ECU sense that its running rich and alter the injector pulses to deliver less fuel (unless say at higher boost when the flow from the larger injectors is needed to prevent it from running to lean?)
BTW the car is a 1997 AE115 4wd wagon with a 7AFE engine now fitted with a T25 turbo.
thanx
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Location:
Brisbane
Registered:
May 2002
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Re: larger injectors with factory ECU?
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Mon, 03 March 2003 00:01
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Yes, the engine will run rich right across the rev range if you don't re-tune the ECU to match the bigger injectors. The ECU can only adjust mixtures to a limited degree, and can't do it at all at WOT; it definitely can't compensate for larger injectors.
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Location:
Auckland, New Zealand
Registered:
October 2002
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Re: larger injectors with factory ECU?
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Mon, 03 March 2003 00:12
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Thanx for the reply.
So if i find out what injectors i have (1997 7AFE engine) and then work out how much fuel i want / need at WOT to stop it running lean and then maybe upgrade the injectors *slightly* then it shouldnt run too much richer when cruising etc right? Is it possible to upgrade only say 2 of the injectors, or should i do all four? Im thinking something like 4AGE injectors might suit as they are likely to be dlightly largert than mine - however i will need to do a little more research down this path first.
Re re-tuning the ECU - how is that done? Doesnt the ECU auto-adjust (within its limits) if it sees the mixtre as too rich?
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Location:
Brisbane
Registered:
May 2002
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Re: larger injectors with factory ECU?
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Mon, 03 March 2003 00:19
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Any changes to the flow rate of your injectors is going to confuse the ECU and make the engine run like a bucket of shite. As I explained, the ECU only has a limited ability to adjust mixtures; it cannot compensate for incorrectly sized injectors.
Why do you want to change your injectors anyway? Unless you've turbocharged your engine, you're not likely to run out of flow from your factory injectors...
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Location:
Auckland, New Zealand
Registered:
October 2002
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Registered:
June 2002
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Re: larger injectors with factory ECU?
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Mon, 03 March 2003 00:38
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This is kind dodgy and may not work on the newer ECU's.
But it works on AE82's etc.
Get your self a boost switch and have it cut out the signal from the EFI temp sensor to the ECU, then (with a relay) run it through a variable resistor to the ECU.
Adjust the resistance to fool the ECU & adjust mixtures.
This tricks the ECU into thinking the engine is running cold and enrichens the mixtures.
Good luck.
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Location:
Auckland, New Zealand
Registered:
October 2002
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Re: larger injectors with factory ECU?
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Mon, 03 March 2003 00:46
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Is that actually going to help though if my injectors are flowing as much fuel as they can already? If they are still not flowing 100% of their possible flow rate then it might help though... not sure how i check to see how they are running though - any suggestions?
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Location:
Lost in the K hole
Registered:
May 2002
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Re: larger injectors with factory ECU?
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Mon, 03 March 2003 01:39
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get the pn# of the stock injectrs, look up a reference list, find the peak hold flow rate of your injectors, and figure out how much HP that can produce at 100% duty cycle. then caculate how much HP you want to make with your engine, assume a max of say 90% injector duty cyle, and see if itll all work.
ed
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Location:
Madrid - Spain
Registered:
August 2002
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Re: larger injectors with factory ECU?
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Mon, 03 March 2003 02:29
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A better way might be to rig up a 5th injector to a pressure switch. That way it fires up at say 5psi adn gives you enough extra fuel for a couple of extre pounds.
You need to use a cold start injector though as the normal injectors are designed to pulse, not continuous use. Youe engine may already have a cold start injector, in which case, just wire up the pressure switch in parallel.
If you want to get heaps more out of it, just use more injectors and fire them up at different pressures.
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Registered:
June 2002
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Re: larger injectors with factory ECU?
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Mon, 03 March 2003 02:51
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Yeah, That mod is no good if you've maxed out the injectors.
Not common on a stock ECU though. Stick a multi meter on the injectors and check the duty cycle.
Another option is a rising rate fuel pressure regulator, once again if you haven't maxed out the injectors.
What have you done about the MAP sensor?? Being only a 1bar sensor what does it do under boost??
Another option you could investigate is using a 2bar MAP sensor of a Starlet GT (provided they both have a 0-1.5v range) and some bigger injectors, as the scale the MAP sensor uses is different. This could get messy though.
Check out the article on Autospeed.com.au "DIY Bigger squiters" I think it is called.
How does the Rolla go compared to your old GSR??
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Location:
Auckland, New Zealand
Registered:
October 2002
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Re: larger injectors with factory ECU?
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Mon, 03 March 2003 03:44
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I know maxing out injectors is not common on a stock ECU - but then again neither is a turbo! (not on this ECU anyway as it was never designed to run one!).
 If i put a multi meter over one of the injectors (while im driving i assume) what am i looking for? Volts? Current? Impedance?
Re rising rate fuel pressure reg - im told the factory fuel press regs are *already* rising rate ones... so when it sees 5psi more pressure in the intake manifold it should bump up fuel pressure accordingly right? Or was i mis-informed?
Re the MAP sensor - i have 2 1-way valves bleeding the boost off so the map sensor never sees boost.
Re compared to the fleet of GSR's ive owned - it doesnt go anywhere near as hard. Then again its only running 5psi and i ran my 96 GSR on about 12psi and my black 92 GSR on about 15psi. My evo 4 - well - theres just no comparison - but then again that car was worth 3X the value of this rolla wagon!
Yeah - apart from fueling issues (so i can run a little higher boost) i also have HUGE smoke problems at the mo. I had my T25 completely rebuilt with the competition interlocking oil seal by a very reputable expert over here in auckland, and ive restricted the oil feed to 2mm, however it still seems to be too much oil presssure - making the car leave smoke screens when i am driving at anything above an intake manifold vac of 10! Not sure what to do about that wee problem either...
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Location:
Auckland, New Zealand
Registered:
October 2002
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Re: larger injectors with factory ECU?
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Mon, 03 March 2003 03:52
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I will look for pn# on the injectors when i go home tonite and see what they are (assuming i can find some charts to look em up on).
Re 5th injector - is it as simple as wiring up an extra injector and a pressure switch? The impedance of the whole injector system isnt going to change at all and affect fuel delivery in the 4 stock injectors?
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Location:
Madrid - Spain
Registered:
August 2002
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Re: larger injectors with factory ECU?
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Mon, 03 March 2003 05:24
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You don't want to just wire up another single injector against an existing one. The normal fuel injectors are designed to pulse the fuel, thats why you have one per cylinder.
Some cars (even toyota's) use a cold start injector in a similar manner to a choke. There is a means of idle-up and a temp switch to fire up the additional injector. This injector squirts continuously at a fairly low flow rate. I think most of the older multi point injected toyotas use this method and it is rigged up to a timer. Newer models just increase the firing time on the main injectors to richen it up.
You will need to tap off the fuel before the regulator so you don't stuff up the pressure to the existing injectors. Then just wire it up to an adjustable fressure switch and dial in the pressure you want it to start at.
The additional injector needs to be fitted before the plenum so that each of the inlet runners get a share.
Have a hunt on the net, I came across this one a while back that looks OK
http://www.xmission.com/~dempsey/perform/injector. htm
Have fun
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Registered:
June 2002
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Re: larger injectors with factory ECU?
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Mon, 03 March 2003 20:54
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I'd go with Gold28's option.
Nice and easy. And I'm sure you'd mount the injector alot better than on that link.
You want to measure Duty cycle (or Hz) with the multimeter.
That weird about the Oil.
I had a T-25 on my 323 and I was told not to put any restriction in the oil feed (internally regulated) and it was fine.
What have you done with the cam cover breathers?? It's not blowing oil into the inlet or something stupid?!?!?
Hopefully the crank won't fall out of the Rolla like the E4!!
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Location:
Auckland, New Zealand
Registered:
October 2002
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Re: larger injectors with factory ECU?
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Mon, 03 March 2003 21:36
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OK - who are you E30-323?  You obviouslly know some pretty specific details about my past cars!
Re cam cover breathers... umm - ive done nothing with them?
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Registered:
June 2002
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Re: larger injectors with factory ECU?
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Mon, 03 March 2003 21:55
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LOL
The internet is a marvelous thing isn't it.
NZMMC.
Usually you have 2 breathers off the cam cover.
On a turbo car one goes to the plenum which will have a one way valve to stop the boost filling up the engine and blowing out through the other breather, which normally goes to the inlet side of the turbo. Which is where you prob may be, all the oil mist from the cam cover getting blown into the turbo/intercooler/engine = smoke (detonation even).
Have you got any pics of your setup??
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Location:
Auckland, New Zealand
Registered:
October 2002
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Re: larger injectors with factory ECU?
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Mon, 03 March 2003 22:18
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LOL - NZMMC eh  so who exactly on NZMMC are you? 
OK from memory there is 1 pipe running from rocker cover to plennum. Actually give me yr email addr and ill send u some pics.
Ta for the help.
AL
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Registered:
June 2002
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Location:
sydney
Registered:
March 2003
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Re: larger injectors with factory ECU?
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Tue, 04 March 2003 10:43
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u say u cant afford an aftermarket ecu
then uy did u goi and buy a jaycar air fuel ration meter
if they work of yr original oxygen sensor then it weont be very accurate as the revs go up
many oxygen sensors work at idle and just off idle
save yr money and buy an aftermarket ecu
in the long run it will be cheaper cause u can change it from vehicl eto vehicle and u wont have to worry bout bigger injectors and stuff untill yr injectors run out
bit over a grand for a microtec is nothing
2nd hand injectors are prob about 100 to 200
fart assing around is prob another 200
extra fuel injectors and switches is another 100
for about 1500 u can get an ecu wired and tuned to suit yr car
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Location:
Auckland, New Zealand
Registered:
October 2002
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Re: larger injectors with factory ECU?
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Mon, 10 March 2003 03:56
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I bought the jaycar air fuel meter to get an idea of how rich (or rather how lean) my car would run once i installed the turbo. Its a pretty cheap unit (70 bucks or something) - however i have since found out that they are indeed not that accurate unless running in closed loop (and why would you need it then anyhow!?).
Re aftermarket ECU - i would be looking at at least $2000NZ for an ECU that does both ignition and fuel probably more for tuning. As for taking it with me when i sell the car - well thats not really going to be an option as the car needs to perform well and be reliable when i sell it - i cant just remove the ecu! (even if it is an after market one). I think i will look at a simple pressure switch triggered extra injector as suggested above. Simple and cheap.
If anyone else has any other good links to articles on extra injector installations please post em here 
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Location:
Madrid - Spain
Registered:
August 2002
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Re: larger injectors with factory ECU?
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Mon, 10 March 2003 05:52
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If you really want to get technical, check out what this guy does. I wqas thinking of going this way when I finally get around to the engine mods. It seems to have a good scope for develpment while still using the factory engine management.
http://minimopar.net/perf/eepc.html
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Location:
sydney
Registered:
March 2003
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Re: larger injectors with factory ECU?
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Mon, 10 March 2003 10:59
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this is crude and cheap
but if u are talkin bout cheap i knew a guy who wire the earth triggers from the injectors to a switch on the throttle
when he hit full throttle the injectors would be 100% duty
fully open heheh
was crude but was one way of bypassing the rev limiter too
hehe
not that i would try this
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