Why Tuners Hate 60lb Siemens Deka's

[Headsex]

Some of you may remember the "great injector debate" of Siemens 60lb Deka vs Bosch 968's, and how many tuners liked 968's over deka's. Infact, some HATED deka's!!!!

The discussion then turned into a mess regarding drilled injectors, and spray patterns etc. Please don’t turn this thread into that.

One particular workshop mentioned the reason why they hated Deka's. The main reason being the LOW injector slope is so "fat" in comparison to High injector slope, causing an unwanted rich idle/midrange until the pcm switches over to the high slope

Let me Illustrate.

Factory Injector scalars

High Slope 0.00929140

Low Slope 0.01357369

Example of 968 scalars

High slope 0.0124620

Low Slope 0.0199999

Now with 60lb Deka Injectors, I've seen values like this.

High slope anywhere from 0.0180 to 0.0210

Low slope anywhere from 0.0270 to 0.0370

Personally, I have used 0.0190 for the high slope, and 0.0325 for the low slope, and allowed adaptive fuel control clean it up. But this is WRONG

I can guarantee that anyone who’s scaled 60lb injectors would be doing something along those lines.

If you multiply the scalar by 3600, it will give you the flow in lb/hr. So 0.038 * 3600 gives 136lb.... So as its been mentioned previously, The Siemens injector thinks it’s a 136lb injector at idle pulse width sizes.

Now in the past, I've offered my assistance to a few interstate tuners with scalars for the dekas because they swear deka's are crap, have problems, etc. Which given the way they are scaled, they do have valid points, especially since having real poor fat idle (before adaptive fuel control cleans it up somewhat, But not completely).

But there is something FUNDERMENTIALLY FLAWED in how Australian tuners are "scaling injectors" for our cars.

Back at the start, People started altering High slope, and Low slope values for Bosch 968 injectors. Sure, sounds easy to do, just keep adjusting the numbers until fuelling is right. And you will come very close to those scalars I mentioned before. And they perform perfectly as the factory ones did.

Now, do the same approach with a Siemens Deka Injector. And you end up with the above numbers, crap idle, which most fix by raising the idle speed etc.

Why?

Think about it for a second.

968 injectors are Bosch injectors. Deka's are Siemens injectors.

The Bosch 968 injector is mechanically the same as the original XR6 Turbo injector as they are both Bosch, just with differently calibrated metering holes. Oh, for those thinking of Drilled injectors. This also stands correct; they are still mechanically the same.

Deka's are not the same mechanically as a Bosch (duh).

Have a look at the following Image.

Wow... What do we have here? Spec sheet for a Siemens injector AS RELEASED by Ford Racing USA! Surely if the siemens injector were bad, why would Ford Racing be using them, or even releasing spec sheets for us tuners.

The high and low injector scalars look fairly close to one another... That’s a bit different from what I showed previously... But why?

Sure, those scalars are for 39.15psi (just below 3bar) base fuel pressure, not 4bar as XR6 Turbos run. But using the FNPW_xxCOMP multiplier tables, we can easily work out new injector scalars using interpolation value of 58.0151psi (4bar) using the LSCOMP/BKCOMP/HSCOMP tables giving us the following scalars

Go put that into your Tune, and Wait a second, it still running like crap, Air fuel ratios are wrong. Etc.

What else do you see on that original spec sheet? "FNPW_OFFSET"

This is the amount of "Opening time" in ms the PCM commands prior to fuel coming out of the injector (vs. battery voltage).

Obviously this is based on 39.15psi (just below 3bar), so based on the FNPW_OFFCOMP table, interpolation 58.0151psi (4bar) from the table gives us 1.22374 multiplier, giving us the following "FNPW_OFFSET" table.

Now compare this with the Factory Battery offset table (which was setup for the Bosch injectors @ 4bar)

Original Bosch first, and calculated Deka's last

What do you notice? The deka Injector DOES NOT need as much Opening time at 12volts as the Bosch injector does.

ie, at 12 volts, the Deka injector only needs 0.777ms Opening time compared to the Bosch of 1.291ms

Doesn’t this tell you the Bosch injector is slower reacting than the Deka injector?

What do you think is going to happen if you leave the BOSCH battery compensation Offset table with increased opening times when using Deka injectors? Whats this going to do in fuel metering? Its going to add extra fuel that the PCM doesnt know about, and hence, people come up with strange Low slope scalers.. Hey I admit, I did at the start.

Can you understand now why the way people scale NON BOSCH injectors is FLAWED? Its because they are ignoring the Battery Volt Offset compensation table!

If your a DEKA NON BELIEVER, I put it to you to try these These Injector values completely, High slope, low slope, break point, MIN PULSE WIDTH, and addjust the Battery Offset table and then decide what you really think of 60lb Deka's

Please note, Regarding the High slope value, You may need to alter this slightly depending if the existing fuel system is upto it.. ie, intank original, walbro, or a bosch 044.

I also have the 80lb Siemens spec sheet, Once I finalise my install, I will post details for them also..

80lb injectors give us the ability to run E85 as it needs 40-50% more fuel flow than normal Petrol.

Tuning for E85 from a fueling point of view is easy, you just have to tell the PCM that lambda 1 of the fuel being used is 9.85..

Or if you run 10% ethanol fuel, a value of 14.1 will make sure fueling is correct and commanding the same lambda as per your base fuel table.

Located under "Fuel" Scalars

Here's the Spec sheet for the 80lb injectors from Ford Racing USA

Scalar values calculated from the interpolation of 58psi

Battery offset calculated from the interpolation of 58psi

Notice at 12volts on the Battery offset table, they have a quicker opening time than the 60lb injectors, as well as the Low slope being smaller than the 60lb injectors.. Im starting to think there will be NO idle problems with these injectors..

Edited 12/03/09 01:59 AM by Dagabond

[Guest]

Very informative Danny

Will be passing this on to my tuner as I run the Deka's...

[Dagabond]

For anyone who missed it...

http://www.fordxr6turbo.com/forum/index.php?showtopic=45276

...or go way back to 2004...

http://www.fordxr6turbo.com/forum/index.php?showtopic=9711

....or into the bowels...

http://www.fordxr6turbo.com/forum/index.php?showtopic=15527

[RIP85]

good read hated when my 60lb injectors were blamed as a possible cause for my cars issues. Was proven otherwise when taken to another tuner, keep us updated with future info

[01txr]

Your a legend.

You helped me get on the right path with the Nizpro drilled injectors, & I am planning to change to the Deka's this weekend, what timing.

Cheers & Big thanks for your help.

[spine]

Changing to DEKA's from my drilled injectors was the best thing I ever did

[ebxmple]

Why was it the best thing you did? What did you notice? I have to upgrade my 968s in the future so wondering what your experiences were.

[IH8TOADS]

Very informative Danny

Will be passing this on to my tuner as I run the Deka's...

I'm sure he will cross reference but idle quality improved when an unsaid few worked on my car. Most noticable improvement was the lack of 'hunting' on decel.

Danny....much appreciated input.

[spine]

Why was it the best thing you did? What did you notice? I have to upgrade my 968s in the future so wondering what your experiences were.

Well for a start MUCH better idle quality.

[_Spin_]

I'm sure he will cross reference but idle quality improved when an unsaid few worked on my car. Most noticable improvement was the lack of 'hunting' on decel.

Danny....much appreciated input.

mate can you define " hunting on decel " ?

Would say, specifically, the revs would hang when you lifted your foot at say, 50 - 60 kph?