idling BIG injector talk (P&H vs saturated)

[Coupe-R]

Was just doing some research into how the Honda ECU and many other ECU's such as a PFC runs the injectors.
Stumbled across some info when seeing if the ECU's are sequential or batch fire. Anyways If you know what I am talking about have a read of my post and comment if you will: Thought this might be useful for Turbo honda people.

Turns out the honda ECU and PFC have saturated injector drivers, therefore run saturated high impedance injectors. However peak and hold are known for their ability to maintain very good idle quality and lean idle even with HUGE injectors.

However the ECU cannot control a peak and hold injector this way.

I.E You put some 1000cc 2ohm peak and hold injectors in your car, you have to run a resistor box as to not burn out the saturated injector drivers in the ECU.
So the ECU thinks you have saturated injectors and still controls them in this way. After all the ECU does not have the circutry to control the injectors in a peak and hold fashion.

BUT WHAT IS PEAK AND HOLD?
Sends a current 4 times as strong to open the injector then reduces the current for the required injector open time.

SATURATED
ramps up the current and then down again, little bit of fuel comes out then and more until needed.

Think of the two as this, put your finger over the end of the garden hose and turn the tap on HARD. Release your finger for the required amount you want.
VS. leave your finger off the hose, turn the tap on for how much you want.

You can see that P&H injectors with a P&H injector driver can more accuratly deliver fuel at low injector pulse times.
People have seen that when running peak and hold injectors with a peak and hold injector driver added to an ECU (if the ecu isn't Peak and hold) that they require alot less ms time for fuel.

Also some with big injectors like 1600cc are idling in the 11.5:1 to 12:1 area because they simply cannot get the correct open and close times for a quality idle. (think of turning tap on and off with your finger off the hose)

Put a peak and hold injector driver in with peak and hold injectors and you can idle in the 14's (stock idle is 14.7:1) with MASSIVE injectors. Also low load and driveabily is increased, as well as duty cyle of 8-15% reduction.

Basically honda uses saturated because the injectors are so small this isn't a problem. I also assume it isn't for 450cc-550cc either
Anyone with Big injectors running a saturated ECU care to comment on the idle quality or AFR's?
I know Locust2000 came over my house end of last year with an EG6 running on 1000's and it didn't idle like stock, little blips every so often.

FJO low impedance injector driver
http://www.fjoracing.com/products/injdrvr/

Also read my PGMFI.org post if you want to.
http://forum.pgmfi.org/viewtopic.php?f=2&t=15473

More from RX7 users with big injectors (the "transistion" is from their primary injectors to seconday injectors)
http://www.rx7club.com/showthread.ph...ello+peak+hold

[Reaper_2000]

very good writeup, even though im a noob injector person ops:

was wondering if you could explain the numbers you mentioned, 11 12 14 - in relation to idle ? what do these numbers represent

[Coupe-R]

Stoich is 14.7 air fuel ratio
stock hondas idle and cruse at 14.7AFR
High number means less fuel or lean, lower number means more fuel or rich. You want to be in the 14's for crus and idle. Getting richer as the power comes on until your maximum AFR for a safe motor

on a turbo car to be safe maybe you would tune to mid to high 11's or even 12.1AFR at full boost.

To be in the 11's on idle is a waste of gas, however people have trouble asking the ECU to supply so little fuel from a large injector to idle in the 14's that it basically splutters and pops or just can't do it.

Peak and hold with the FJO driver will achieve this. Or just a decent aftermarket ECU with a peak and hold injector driver built in (4A/1A)

[Bananaman]

The numbers are Air Fuel Ratios.

I am a little noob at this myself but I think it is 12 parts air to 1 part fuel.

12:1

[Hayce]

Your link to pgmfi points to rx7-club?

I've read your post and get it but I'm struggling to pick out the question or the point?

So P&H is better for big injectors under idle, I guess if the injectors are that big that you are struggling you either have the wrong (too big) ones or if not who cares? the car must be an animal anyway so why fret over the idle?

I get the feeling I'm missing the point and shouldn't post but thats never stopped me before has it

[Coupe-R]

There is no question, point was just for interesting reading and hearing from others with big injectors and idle. By big I mean over 700cc or something.

So P&H is better for big injectors under idle, I guess if the injectors are that big that you are struggling you either have the wrong (too big) ones

No you have got the point, apart from "wrong injectors" if the car needs 700-1000cc injectors then you can't do much about it. If your idle quality is poor then maybe my post applies.

or if not who cares? the car must be an animal anyway so why fret over the idle?

haha yep, thats why most people don't bother with what I said, just posted out of interest

[Hayce]

Oh cool cool.

I know Judd was having a bitch of a time with his 1000's on his link, swapped them out for 7xx's?

I had a little read of the rx7 forum and yea those chaps would have a real issue with 1600's on a pfc. The post seems to be more talking about the method used (FJO) to swap to P&H.

Good info though, I must admit I don't know enough about injectors and the finer points.

[Coupe-R]

THe RX7 post is a VERY good example of why you need a peak and hold injector driver to idle and cruse large injectors smoothly. It can be done without tho.

FJO is just ONE option to get a peak and hold injector driver

[nemesisteg]

hmmm interesting.. Link themselves basically told me that it wasnt possible to get the car to idle with integralink ecu and 1000cc injectors, we did it in the end tho, it was just really rich down low, save washing bores over time (dont know if that would have been the case or not, rather safe then sorry). thats why i swapped them out for 780cc injectors. the car had two hours on the dyno and all the down low stuff was done. all ive done is drive it off the trailer but first impressions tell me low down driveability is awesome in comparison to previous

[Coupe-R]

hmmm interesting.. Link themselves basically told me that it wasnt possible to get the car to idle with integralink ecu and 1000cc injectors, we did it in the end tho, it was just really rich down low, save washing bores over time (dont know if that would have been the case or not, rather safe then sorry). thats why i swapped them out for 780cc injectors. the car had two hours on the dyno and all the down low stuff was done. all ive done is drive it off the trailer but first impressions tell me low down driveability is awesome in comparison to previous

Find out if the integra link has a saturated injector driver (I bet it does because its designed to run the saturated stock injectors)

So this is a good example of my first post. Because the 780cc injectors are smaller the physical open and close time isn't affected as much as the 1000cc injectors.
You can try compensate as much as possible for this but as you said, it ends up being rich down low.

[turboteg]

integralink does have a saturated injector driver, mine idles fine on 880cc injectors, not real lean but surprisingly it idles leaner and cruises leaner than we use to be able to get it to on saturated 550cc rx7 injectors.

[Coupe-R]

cheers for that turbo teg

either your injector offset settings in the link are better setup for your new 880cc injectors, or the RX7 ones needed cleaning or flow testing.
Or the 880cc just has a better operation and spray pattern.

So it seems you can go pretty dam big before you run into decent probs eh turbo teg. What AFR is your idle and cruse?

[americ_ian]

for a few years YOU could not get saturated injectors over 600-700cc

dont know now tho

preludes/ obd1 and obd0 hondas ran peak and hold with resistor packs...

the idle on my coupe was perfect with 720s p&h ie no blurps.

edit: went on H-T found some injector sizes
looks to still be the case

310cc (Saturated/high impedance) $235 shipped
400cc (Saturated/high impedance) $235 shipped
440cc (Saturated/high impedance) $235 shipped
525cc (Saturated/high impedance) $295 shipped
580cc (Peak and hold/low impedance) $295 shipped
680cc (Peak and hold/low impedance) $295 shipped
650cc (Saturated/high impedance) $295 shipped
780cc (Peak and hold/low impedance) $295 shipped
880cc (Peak and hold/low impedance) $295 shipped
1000cc (Peak and hold/low impedance) $325 shipped
1600cc (Peak and hold/low impedance) $415 shipped

Walbro fuel pumps $99.99 SHIPPED , $120 shipped for pump


no saturated offerrd over 650cc??


edit edit edit

Peak and Hold:

Peak/hold injectors are low impedence, usually in the 1-4 ohm range. When the ecu calls for fuel to be injected, it sends out voltage via the wire clips until a certain current level is reached (the peak part) (varies by injector size, company). For the duration of 1 pulse width, that current is slightly reduced and held (the hold part).

Advantages of this design:

* minimizes the injectors "on" time, resulting in faster response

Disadvantages of this design:

* increases coil heat, which can lead to failure over time



Saturated:

Saturated injectors are generally higher impedence than peak and hold, running in about the 10-15 ohms range. Unlike peak/hold, a saturated injector remains "on" for the entire pulse width.

Advantages of this design:

* reduces heat

Disadvantages of this design:

* slower response time
* can't handel large CC or lb/hr styles due to limitations in its speed.


Hence the reason, P&H injectors are used for high HP

/end thread

edit edit.. or maybe im missing the point? :wink:

[turboteg]

the injectors i run now are 880cc precision peak and hold with a honda resistor box, the biggest saturated injectors i could find were 750cc rc engineering ones, but pretty pricey and not really big enough for what i wanted.

the rx7 ones were cleaned and flow tested but i've read reports on them saying there spray pattern isn't that good.

the setup now will comfortable cruise at 14.7AFR, with a smooth idle a little richer! very touchy on the idle tho, definitely on the limit!

[Coupe-R]

Ian you are bang on with your post

but remember

preludes/ obd1 and obd0 hondas ran peak and hold with resistor packs...

they run a resistor pack with peak and hold but I bet that the ecu uses a saturated injector driver just like all the other ECU's.
Therefore the injectors are still fuctioning in a saturated way. (this is the man crux or point of the post here)

Turbo teg, yes 750cc is the biggest I think; and yes with very good tuning and setup it can be done the regular way just as you have prooven.

[Coupe-R]

Here is some info on how to build the peak and hold injector driver if any electronics guru's are keen.

http://www.national.com/mpf/LM/LM1949.html

[Horny_Devil]

pretty easy to make as python made one back in mid 2006 using the same IC

http://nzhondas.com/phpBB2/the-p-amp...tml?highlight=

would only really be useful if ur running large injectors and u want a short pulse to be able to idle or run at low RPM's

http://www.national.com/images/pf/LM1949/00506201.pdf

[Coupe-R]

Correct 8) he said he built it for $150

would cost about $260 for a FJO peak and hold injector driver here.

Thats cool that Python was into all this stuff and ECU chipping back then, now hes like a ghost.

Oh well it continues to interest me and crome is HEAPS better now than it was in 2006

[Horny_Devil]

i mean its really not that hard to make, the worst bit would be getting a circuit board made up for it so it all works fine and the components are all placed well. the soldering and sourcing of the components are a piece of piss

have access to all that sort of stuff here, but would need to talk to the lil asian guy who makes all our circuits

[turbozxi]

Originally Posted by turboteg

the injectors i run now are 880cc precision peak and hold with a honda resistor box, the biggest saturated injectors i could find were 750cc rc engineering ones, but pretty pricey and not really big enough for what i wanted.

the rx7 ones were cleaned and flow tested but i've read reports on them saying there spray pattern isn't that good.

the setup now will comfortable cruise at 14.7AFR, with a smooth idle a little richer! very touchy on the idle tho, definitely on the limit!

I have said it few times in the past rx7 injectors have a piss poor spray pattern.

[Coupe-R]

granded turbozxi, however we are talking about massive injectors from the likes of precision and RC engineering that won't be able to idle and delivery tiny ms pulses using the current saturated injector drivers.

No matter how good your injector is/spray pattern etc. The injectors are not being driven in a peak 4A hold 1A fashion.

That aside many are running 1000cc off a honda ecu. However they won't have PERFECT factory idle. (Thats what the peak and hold injector driver achieves)

also possibly less injector duration needed under the power curve

[americ_ian]

llew goast? no way

hes been busy


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=madman