what tuning needs to be done to use 42# injectors

I have a set of new 42lb injectors waiting to go in ASAP. Anyone have a table I can import to use em so I can get them in tonight and shake this vacuum leak?

turtleman wrote:

I have a set of new 42lb injectors waiting to go in ASAP. Anyone have a table I can import to use em so I can get them in tonight and shake this vacuum leak?

text mr. kemp.

36 / 42.5 = .847

Multiply your injector flow rates by .847 and you should be good to go. That's it.

AA wrote:

36 / 42.5 = .847

Multiply your injector flow rates by .847 and you should be good to go. That's it.

That's pretty much it. If you do before and after tuning, you'll find the idle needs a little tweaking afterwards for perfection, but otherwise that's all. You will certainly be fully driveable by just multiplying the IFR table by .847.

so my 38.16g/s across the board becomes 32.32g/s

Does that look right?

Yep, that should do it.

CK says 33.7/42.5 because 33.7 is what the stock injectors are at static flow rate

Even if that's true, I don't know why you would use the static value as reference to calculate, because your stock injectors are not going static at idle, cruise, even most heavy throttle (are yours running 100% duty at all?).

If you base your calculation on static value, won't the engine will run rich 99% of the time with the 42.5# injectors?

STOCK INJECTORS
33.71 lbs/hr @ 3 Bar (44.1 psi I think)
34.28 lbs/hr @ 45 psi
12.2 Ohm

42.5lb INJECTORS
Static Flow Rate: 42.29 lb/hr @ 43.5PSI
Static Flow Rate: 48.83 lb/hr @ 58.0PSI
15.9 Ohm

this is ZZP's information but in terms of making an accurate skew, It seems to me like I want to use the 33.7 factor. I'm assuming that the numbers they give for stock injectors are also static.

Interesting numbers. Wonder why they are called "36#" if they only flow 33 lb/hr? If ZZP tested them that low, I wouldn't buy them. Here's a test showing 36 lb/hr:

http://dtcc.cz28.com/flow/index.htm

The way to do this is just pick a number and try it. My suggestion is 32.32 and Kemp's is 30.26 g/s. The lower number risks going lean. I'd be safe and use 32.32 g/s. Scan the engine and watch where STFT goes. If you're (+), IFR needs to go up; if (-), IFR needs to go down.

Ok I installed the injectors, imported the base LQ4 table and the 32.32 in the IFR table. The car runs fine below 50% throttle and fuel trims are pretty good. It stays at or close to zero and deviates negative if anything. I tried using the 30.26 factor in the IFR table and have nearly unchanged scan results. My problem is that above about 50%-60% throttle, the car seems to loose all power and it happens consistently. I suppose it happens when fuel trims lock? Anyway, I'm confused as hell here.

Is your IFR table static values? Mine isn't. What are you tuning with? DHP or HPT?

HPTuners
That's my table

Here's what I got from Frankie and have used w/o issues.



Basically you plug in the value of the injector and skew it as the stockers were or if you need to. Some folks put in the 42.5 across the board and tune the remainder to dial them in.

Codith, what are your O2 numbers looking like at WOT (or when you feel it lose power)?

Correction to my situation - my trims are really hanging negative. They will go anywhere from zero to over 10 (negative) during normal street driving. I reset my trims after I changed the maf and IFR tables to try to have a totally clean slate to start with. What does it take for the trims to find themselves? I've driven it probably three times now since.

Bill you are showing me something totally different than what people have told me so far (as you can see above) which really confuses me even more.
30.26 vs 32.32 and now you throw in these fourty-somethings! lol

The IFR or injector flow rate table needs to have the flow rate of the injectors. Factory injectors are 38ish or something close to that. When you swap to 42.5 injectors you need to add those values accordingly.

Your fuel trims are negative because the computer see's a lot of richness via the O2 and it's trying to remove itt.

STFT's begin to stabilize into LTFT's after at least two drive cycles of 10 minues or more. That's 10 minutes of up to temp in case you are in a cold climate.

here's on HPT thread about it. While I didn't find you the best. thread..it serves it's purpose. The guy takes his stock injector rate of 38ish and mulitplies by 1.1185 which equals right about 42.5
http://www.hptuners.com/forum/showthread.php?t=17588&highlight=changing+injectors

You can choose how you want to make the change, as an equal value in all or distributed the way they were before.

Codith, were your LTFTs zeroed before you swapped the injectors? If you weren't tuned right before, you won't be right with after the injector swap. You need a reference point.

Did you do any changes to the MAFF values? You should start with the same MAFF you used with the stock injectors. Only change the IFR table. If you haven't changed the MAFF or anything else, try Kemp's suggestion of 30.26. That should push you more toward zero.

I agree that Bill's data is confusing. Putting lb/hr values in the g/s IFR table seems pretty crazy. If you're rich now, you certainly don't want to increase your IFR values up into the 40s!!!

You know when the car is done adjusting trims when LTFT seems to stop moving as fast, and STFT is always near zero. If STFT is erratic, it's still learning.

AA wrote:

Codith, were your LTFTs zeroed before you swapped the injectors? If you weren't tuned right before, you won't be right with after the injector swap. You need a reference point.

Did you do any changes to the MAFF values? You should start with the same MAFF you used with the stock injectors. Only change the IFR table.

It was a clusterfuck. I got the injectors in part to replace my old ones which I believed had bad seals that were causing a major vacuum leak. I also made a special maf tune before to drive the car with the vacuum leak. Basically , the idle to vacuum ranges were hopelessly lean and above that point in throttle I was pretty close to zero and stable.

So I had a very skewed maf tune before I did the injectors that would not be acceptable under normal (no vacuum leak) circumstances. When I installed the new injectors, I imported the base LQ4 maf table and changed the IFR table at the same time. Additionally, I used the VCM controls to reset the learned fuel trims because I figured it would be grossly wrong anyway and I wanted a clean slate to start with.


Update, I've been driving the car a bit today and It just doesn't seem like anything wants to stabilize. When I open up the throttle, the trim locks at a value somewhere around -10 and the car doesn't get all retarded like it did but it still lacks power. I would say it's better than it was before but not nearly what it should be. I can have some trouble starting it lately too. It won't really want to start unless I give it some throttle. Again, this seems like a over-enrichening (word?) problem. This maf table I'm running right now should be damn close to perfect if nothing else was changed so I still think something is wrong with the IFR or something concerning fuel control. I've done plenty of messing around with the maf table before I ever touched the fuel system and never had results as poor as this.

In effort to try to learn more, I visited HPtuners tune repository to study some tunes from others with similar stuff. The closest thing I came across was a '00 gtp with my injectors and maf sensor among other things. This is what his stuff looks like...





Note I changed to metric so it's not going to compare very well to what I've shown in above posts. It looks like he did something more like what Bill showed me for the IFR's. This maf table is not much different than my lq4 table. It just has a slight increase across the whole curve. I was hesitant to do this but I just imported his maf table and IFR table (didn't reset trims or anything) and wouldn't you know it the car started up and drove fine. All my power seems to be back. I've only taken one test trip with this tune in but I scanned every second of it and from what I've looked at so far, trims are much better already.

Good to hear... Sorry I'm not more help with the HPT stuff. It's a totally different method.

I can understand where it may seem confusing. Took a moment and looked to Google for the conversion .

1 gram per second = 7.93664144 pounds per hour

About 80% does seem like we'd be a bit off. Then ask yourself, what size is the stock fuel injector? ~38-39lbs right? The values in the table seem to mimick the pph.

Aaron, you confused me with your statement that you wouldn't want to increase the table size of the injector if the trims were screaming rich. The pcm uses the table injector sizing to calculate how frequently to pulse the injectors. A larger injector sees fewer IPW's to supply the same amount of fuel as a smaller injector. with higher IPW's.

Increasing the table size of the injector w/o changing the actual injector will slow pulses and reduce fueling. Just as decreasing the table size of the injectors will increase IPW's and push more fuel.

Uhhh Bill - the injector pulse frequency = once per intake stroke. The IPW = Injector Pulse Width, or how long the injector stays open for. Or is something mistaken there?

So the rated lb/hr of the injectors is at a given duty cycle (I forget what), and grams/sec and lb/hr is pulses * pulse width * injector flow rate * some conversion factor. Right?

I gotta stop ansering posts too early in the morning.

The point was though..by making the injector size larger in the table, it supplies less fuel if the actual size of the injector stays the same.

BillBoost37 wrote:

I gotta stop ansering posts too early in the morning.

The point was though..by making the injector size larger in the table, it supplies less fuel if the actual size of the injector stays the same.

This isn't considered the proper or best way to tune in injectors but in a pinch can help a lean or rich condition until proper tuning is done