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Advice Please - Which Aftermarket Injectors


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  • Member For: 19y 5m 17d
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  • Location: OZ

I would only use Deka's if I knew how the tuner scales them....which can be easily determined with the use of a Flash 2 data logger. Nizpro injectors are so commonly criticised and IMO it's not warranted.

Most people don't understand the requirement to scale injectors correctly (google "injector dead times") in the tuning software but basically if you use an injector that is mechanically different to the Bocsh item then you need to modify the battery offset table to account for the different dead time values for the injectors. This holds true for the deka's, however the problem is that (again in my experience) most tuners simply rely on the PCM's closed loop learning to adjust the fuelling in order to achieve 14.64 AFR when in closed loop. The long term fuel trim for the dekas will sit at about 0.9 and explains why the low slope value in the software is so funky.

Headsex posted some scalars to try for the Deka's but as we know these don't work. Load those scalars and you'll run 10 - 11 AFR at idle. Drop the pulse width and you'll run 17's...if you don't stall. The Aussie PCM simply won't accept the 'known' deadtime values for these injectors. Very few tuners with modify the offset table for the deka's as they simply dont have time to work it out and consequently the fuelling is not the best, particuarly when in closed loop. I did an 11 min AFR log with the dekas and it was very ugly compared to the log with Bosch injectors as I had not scaled the deka's correctly.

As Danny has posted "The deka values I posted before are 100% correct as per ford motorsport, but, the minimum pulsewidth is too large for our engines, and causes excessive richness at idle, combatting this, you rise the idle speed a little and raise the battery offset table a little (and adjust the low slope injector to compensate). dropping the min pulsewidth just causes the engine to stall as PCM will not open the injector".

Anyway in short the deka's are a good injector, it's just that tuners need to learn how to scale them correctly and account for the different deadtime values........the sooner this happens the better!

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  • Member For: 19y 5m 17d
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With the strong aussie dollar look on the net...there's some good prices going around for deka's (sub 400 flow matched & delivered). I bought a set off eBay to have a play with calibrations for the big turbo6.

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  • Member For: 17y 4m 7d
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  • Location: Broady, Melbourne

The Siemens 60lbs that we sell are 1% matched by the supplier in the states.

These were accually flow tested by a customer recently and the figures were backed up which was great.

The unmatched sets can be 5-10% within each other, so results from these can be varied. This us why I only sell matched sets.

Easilly the most commonly used injector for xr6t, so they must be working well enough for the majority of us.

I had mine cleaned and flowed recently and I can back this up. Factory spec is +/- 5% so it's a 10% window meaning there can be a 10% difference in flow. One of my injectors was just on that, 10% less flow than most of the rest. After seeing that, I would not get a set of any injectors unless they were flow matched.

The Siemens are excellent. I've noticed different tuners tune differently (imagine that!) so I've had tunes in my car where the idle from the Siemens is near factory from one tuner, but other tuners idle quality can be fairly rough. The rough idle does not make a difference to performance or economy.

I'd like to see data from the newer Bosch EV14's. 6 orifice and up to 2000cc (milled). And if done correctly, there's nothing wrong with milled injectors. If they are flow matched, you have peace of mind that they have been done correctly. So I wouldn't discount flow matched milled injectors. Plenty of big performance engines use them.

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  • Member For: 19y 5m 17d
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The deka's can suffer from a rough idle and this is very dependant on what scaling is used. Not all cars suffer from this but a lot do. If your car is one that does you need to get your tuner to tune the idle like it has bigger camshafts. Basically the factory calibration doesn't have a target idle. If you look at the idle spark tables you'll see 63 degrees advance, so the pcm can do what it wants.

Closed loop idle control uses spark to trim idle and it's rather aggressive (scaling can affest this though). You really need to drop the desired idle and drive spark as well as lower the scalar to prevent spark jumping around so much. This stabilises the pulsewidth and smoothes the idle.

This method works and it works well :bowdown:

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  • Member For: 17y 4m 7d
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  • Location: Broady, Melbourne

Nice info. If I wasn't going to be putting in my 600+ rwkw donk in a couple of months, I'd probably go back to my tuner and get this sorted. Thanks for sharing because sharing is caring :)

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