Tuning With Bigger Injectors

[Crans]

Basic setup of the car Rb25Det Deatchwerks 740cc Injectors Rb20 ECU running nistune and a VCT controller.

Installed the injectors, all looks good nothing leaking. Run the Injector change function on nistune and the Injector multiplier is nearly halfed. Stupid thing starts to barly idle at a very lean 19AFR. Im adding nearly an extra 60% to the Multiplier to get it to idle at 14.9AFR the idle is just shit sounds liek a wrx on 3 cylinders.

Up the multiplier some more and AFR head towards 12.5 and the idle is alot nicer.

Now if the idle is set to what it should be the rest of the map becomes extremely rich, so rich in fact that the car splutters and stops moving.

So now i have 0'ed out the fuel map in the cruise section and cruising along adjust the multiplier to sround what it was when the injector change function was run.

Car seams to drive alot better comming on to boost it is still very rich but drivable(In the 11-12AFR range), no spluttering at all felt more like before the injector change.

Now to get it to idle thoses fuel cells are now adjusted to theroetical 10AFR

The way the nissan ecu's work theoretical AFR sound be pretty close to actual AFR expecially in the light cruize/idle range.

Any ideas? Deatchwerks sell them as drop in replacements from what i can see of the injector report lag tims are correct.

Is thi normal for larger injectors? Any one else with Deatchwerks experiance?

[Moodles2]

Do you know the latency of the injectors?

Did you multiply that figure by 2 and enter it into nistune?

[rob82]

Ahh - the difference between theory and practise.

1. Your using quite a large injector how much power are you after?

2. Those injectors are quite poor in terms of spray pattern and low end drivability.

3. The test benches that injector manufactures use don't always match the how the factory ecu's drive injectors so the provided latencies aren't always that good of a guide.

The problem you are experiencing is non-linearity of the injector from driving a too smaller pulse width. You can correct it by increasing your latency time or to increase your ttp min. I would put in your calculated k value and try increasing your latency first, failing that increase your ttp min.

[Crans]

I new there maybe slight idle issues but nothing like this I havnt touched latency values was actually gonna ask about them I'll post the flow sheet

[JonnoHR31]

you have to adjust the latency corrections, if the 740s are anything like the 1000s i got from Deatchwerks the latency is massively different to stock. you should have got a flow report with the injectors with latency figures on it

[Crans]

Here is the report from Deatchwerks

Report says 756cc avg flow static and 645cc avg flow dynamic. Which figure do i use in my calculations?

And yes I can see 1.3ms Latency @ 14V I will give this a go tomorrow

[MrStabby]

The lean at idle symptoms you describe in your first post is typical of having the latency too low, whereas at WOT latency setting is not important. So - fixing the latency setting should help a lot!

[JonnoHR31]

Here is the report from Deatchwerks

Report says 756cc avg flow static and 645cc avg flow dynamic. Which figure do i use in my calculations?

And yes I can see 1.3ms Latency @ 14V I will give this a go tomorrow

use 756. cant remember exactly how nistune works the latency but for reference the standard 25 injectors are .63ms

[Crans]

Finally got around to trying this again. Set injector latency to 1300 resized injectors to 756 saved changes and started the car.

Car started and idled better than ever before(Even before the injector change)

Didn't have time to let it fully warm up and fine tune the multiplier but so far very happy with the hiflow injectors.

I was always told the hiflowed rb25 injectors were bad at cold start. These being Suburu hiflowed injectors seam absolutly fine.

Oh and to answer the previous question. Why did I buy such large injectors.

My power goal is 400hp for now but I do plan on building a 3L and run E85 so only buying injectors the one time

[Crans]

Still having issues with these injectors haven't driven my car since installing them.

Here is an email I got from Deatschwerks regarding the problem.

Jason,

If the OE latency is displayed as 530us for the OE RB25 ECU, then think using 1300us for our injectors would be way off. The RB25 uses a OE side feed injector with almost the same coil properties as our 740’s. I would suggest trying something in the 700 rang and see if that helps then adjust from there. Our injector would not have anywhere close to more than twice the latency time as the OE injector

Thanks

-Mike

Now as you can see from the flow report I posted @14v(My car runs 13.9-14v at idle) the latency is 1.3MS or 1300us for Nistuns sake.

From what Mike at Deatschwerks is saying this is incorrect??? Does this mean the latency data provided is for both opening and closing time?

Ho can I accurately measure latency time my self?

[Adriano]

So what problems is it now having.

[STATUS]

Your spending too much time on latency and concentrating on theory (very often the case text book tuning is useless in real world applications), best bet is to concentrate on your idle and cruise with latency within 10% of the factory setting as they are high flowed. Use your K value.

Once cruise and idle is set to a reasonable setting then retune the rest of the map,it is not uncommon to rewrite the whole map so it resembles nothing like your old one.

Maniplutaion of the MAF curve is generally a given too. The maps Tao has posted the last few pages of his highflow thread have around 1.5 to 2hours spent on the MAF curve alone... so much detail in there athat changing turbos generally only requires a run or 2 on the dyno to touch up each time.

[Crans]

So what problems is it now having.

Still the same issue idle is only perfect when running really rich.

Status, that is some really good advise. I will get the latency and K value as good as I can get it then just start re tuning the rest of the map.

When you talk about tuning the MAF curve as you referring to adjusting the MAF table so real world AFR's resemble the theoretical AFR on the fuel map?

I guess that kinda like a 2D VE map isn't it?

If only the dyno my mate and me are building was complete would make this a lot easier.

One more question.

What is the stock latency figure for the rb25?

I have a nistuned rb20 ecu running my car and the latency in there is different to the latency of the stock rb25 ecu.

Maybe this value was forgotten when I had the base image built by Nistune? This could be the reason my car has always run really rich and had a bad idle?

Any way cheers for all the help again guys.

[STATUS]

Still the same issue idle is only perfect when running really rich.

Status, that is some really good advise. I will get the latency and K value as good as I can get it then just start re tuning the rest of the map.

When you talk about tuning the MAF curve as you referring to adjusting the MAF table so real world AFR's resemble the theoretical AFR on the fuel map?

I guess that kinda like a 2D VE map isn't it?

If only the dyno my mate and me are building was complete would make this a lot easier.

One more question.

What is the stock latency figure for the rb25?

I have a nistuned rb20 ecu running my car and the latency in there is different to the latency of the stock rb25 ecu.

Maybe this value was forgotten when I had the base image built by Nistune? This could be the reason my car has always run really rich and had a bad idle?

Any way cheers for all the help again guys.

any conversion ecu required a full retune to get it working sweet, if you look in your rom pack under type 6 he rb25 bin files are all there..

Yes your reasoning on the maf map is correct, ive been spending more and more time in this map now that nistune changed the scale manipulation for me (on other ecus like pfc its where i spend most time), it used to be a tedious job as the values would only scale up and down in 10's... they have since changed it for me so it scales in 100's and it has been absolute bliss

Cant fault the Nistune guys as they are quick to react and help with any suggestions or upgrades.

[rob82]

Still the same issue idle is only perfect when running really rich.

Status, that is some really good advise. I will get the latency and K value as good as I can get it then just start re tuning the rest of the map.

When you talk about tuning the MAF curve as you referring to adjusting the MAF table so real world AFR's resemble the theoretical AFR on the fuel map?

I guess that kinda like a 2D VE map isn't it?

If only the dyno my mate and me are building was complete would make this a lot easier.

One more question.

What is the stock latency figure for the rb25?

I have a nistuned rb20 ecu running my car and the latency in there is different to the latency of the stock rb25 ecu.

Maybe this value was forgotten when I had the base image built by Nistune? This could be the reason my car has always run really rich and had a bad idle?

Any way cheers for all the help again guys.

The issue sounds like your operating the injector outside its linear zone. You may have to leave it on the rich side. I would do as I said above and not modify the maf curve.

[Guilt-Toy]

with nistune you need to find the sweet spot. it can be really fiddly.

[Crans]

Little update:

Planned to spend the day tuning my car. Ended up spending most of the time help my mate on his 3L and installing a Deatschwerks 300LPH fuel pump.

We had great sucess apart from my fuel gauge no longer working and i think the filter the fuel pump cam with dosn;t quite reach as far down as the stock setup, both can be fixed easily i guess.

Can you but a new stock fuel pump filter setup?

Started the car with the new pump and no tune adjustment.

Started really well but again very rich. After the car warmed up a little and closed loop took over the fueling the car idle fu*king beautiful and sat with a 14.8 - 14.9 AFR.

Starting the car I can see its still got way too much fuel in it but thats expected as I still need to adjust to injector settings.

So i'm thinking all these rough idle and missing issues for the last 2 years have been a stuffed fuel pump the whole time. Changing the injectors over just made the symptoms a lot worse.

The Deatschwerks pump was a tad over $200 including a nissan filling kit, purchased from Kudos motorsports web site. It is very quiet compaired to the noisy as hell r32GTR pump that was just removed.

Now I can start seeing what the real quality of these injectors are fuel pump are.

[Crans]

BTW here is a pic of the fuel pump on the cradle

[Room42]

BTW here is a pic of the fuel pump on the cradle

outdoor furniture oil hey?

[Crans]

outdoor furniture oil hey?

Haha yep the best stuff for engine assembly.