changing injectors question about startup

[MWILSON1995Z]

Im going from 30# to 60# injectors. Will the car even start or do I need to make some tune adjustments before starting and data logging? thanks

[dave w]

The quick answer is yes, the injector flow rate will need to be changed.

dave w

[MWILSON1995Z]

Ok thats not a problem

[dave w]

More often than not: what an injector is rated to flow vs. what an injector is actually flowing vs. the injector flow rate programmed into the .bin file . . . will be different flow rates. :mad1:

dave w

[MWILSON1995Z]

Supposedly the injectors come with flow sheets for my actual injectors

[LeMarky Dissod]

Supposedly the injectors come with flow sheets for my actual injectorsAssuming the flow sheets actually apply to your injectors (there are several places out there that are NOT Fuel Injector Dynamics, that provide flow sheets that look like FID flow sheets, but turn out not to be), you'll have all the info you'll need to adjust not only the basic flow rate, but the low voltage / low pulsewidth behavior as well.

[MWILSON1995Z]

Im very new at this I bought CATS Tuning software the only changes Ive made are to the Fuel & Timing at WOT and I changed it when I swapped the injectors I have now ( not a big difference from stock though ) and I changed it when I changed gears but thats the extent of my tuning experience

[spfautsch]

You should really give more information about what you're tuning, mods, etc. up front. Save everybody the time and trouble of going and reading the introductions forum.

So you're running a '95 LT-1 with the 292XFI? I'm interested how this sounds and smells at idle, I run a 280XFI N/A with 42lb injectors.

Anyway, going from 24lb to 30lb injectors isn't a big change. 30lb to 60lb you're going to have all sorts of starting problems that won't be addressed by simply changing the static flow constant. The prime pulsewidth table will need some tweaks, and it has it's own multiplier that will need to be scaled based on the change so you don't end up flooding the bejeezus out of it. A couple years ago kur4o and I worked on this and as a result I built a spreadsheet that may save you a bunch of time and frustration. I'll try to find the thread and update this one with a link. But if I forget to let me know and I can probably find the spreadsheet easier.

Edit: I located the aforementioned thread and realized it wasn't focused much on the start-up (prime pulsewidth) tables. Gimme a day or so and I'll write up a readme for the spreadsheet and put a link to it all in my signature.

[MWILSON1995Z]

You should really give more information about what you're tuning, mods, etc. up front.


358 ci LT1 all forged bottom end 10.3:1
Trick Flow 185cc heads, 5 angle VJ all 7/16 hardware SS 1.6 Rockers
Springs are set at 160# @ 1.895 & 425# @ 1.295
292XFI HR13
Factory Intake with BBK 58mm TB
Dougs 1 3/4" headers off road X with original flowmaster 40
Powerdyne BD11A @ 7-8psi draw thru Maf sensor
ARP studs everywhere
Canton racing oil pan & valve covers
Still running Optispark buit everything is new and working for now!

Thank you for any help! I have EE Hack I use for data logging and Flash hack for writing, tuner CATS for making adjustments

[spfautsch]

Sig is updated. Unfortunately I think you'll need to use TunerProRT because I'm not sure tunercat has the base pulsewidth multiplier defined. Also the readme is written specifically for TunerPro. If you have any feedback feel free to PM me or post here, I don't think anyone has used this other than myself.

I didn't catch the supercharger in your introduction post - so are you running pure MAF or do you have patches for >1bar MAP (if such a patch exists)? Intercooler?

[MWILSON1995Z]

I see the following:

ECM Constants Table
Minimum Injector Pulse Width--------1.099 msec

I also have MAF sensor tables

I just ordered an integrated AFR guage with 2 oxegen sensors for data logging

[spfautsch]

I see the following:

ECM Constants Table
Minimum Injector Pulse Width--------1.099 msec

If you look at your bin with the .xdf in the startup tables zip in TunerPro, there are actually two values that need to be changed here. The factory bin has 1.44 ms in both. One is the threshold, and the other is the value used when the threshold is reached. I think it's labeled '126d7 - use this value when MIN inj pulse reached'. I have mine set thusly:

126d5 : 0x002f (0.73 ms)
126d7 : 0x0030 (0.075 ms)

The larger # in the second constant is just to make sure the injector actually fires. I've never seen pulsewidths commanded this low, and you probably won't either, but it doesn't hurt to be thorough.

Addition items you'll want to modify are the 129f5 Injector Offset Adder table, and 129d5 Injector Voltage Offsets.

For the offset adder table, most folks zero this out because the bosch style injectors flow more below the knee (the point where the injector's flow rate goes static). The original Multec injectors have a lower flow rate below the knee.

The voltage offsets should have been provided by the vendor. You may have to interpolate some of the voltage points, but all that's critical here are the voltage range you'll actually be running in, say 7-16 volts.

[MWILSON1995Z]

If I load my bin in Tuner Pro I really dont know where to go from there and I dont think I have an XDF file? Im used to Tuner CAT which Im new at as well.

[MWILSON1995Z]

Typical Flow Rate in LB per hour: 60 LBS/HR @ 45 PSI
Typical Flow Rate in CC per minute: 630 CC/min @ 45 PSI
Actual flow rate of your injectors may vary but will be matched together ( mine vary from 54.5-55.5 )
Resistance: 10 ohms (High Impedance, High Resistance)
Voltage: 8-15 Volts, nominal 13.5 Volts
Amperage: 1.0 Amps
Pressure: Min 30 PSIG / Max 100 PSIG
Electrical connector type: EV1 (Minitimer, Jetronic)

[spfautsch]

If I load my bin in Tuner Pro I really dont know where to go from there and I dont think I have an XDF file? Im used to Tuner CAT which Im new at as well.

There's a readme file in the spreadsheet package in my sig that will get you started crawling with TunerPro. That's as close to spoon feeding you're going to get out of me, sorry.

As I mentioned in the PM, 1 lb/hr difference in a set of matched injectors seems really excessive. But at least they gave you that data. Are these injectors new / modified / used + cleaned? You'll need an offset table for them.

[MWILSON1995Z]

They are new, downloaded the file thank you

https://treperformance.com/i-20618988-tre-60lb-bosch-siemens-deka-iv-style-fuel-injectors-8.html

[spfautsch]

I don't have a datasheet on those but it should be easy to find.

If you don't have retainers for the top, be sure to do something on the bottom of the injector to keep it from falling out of the fuel rail. An extra o-ring can work, or you can do something like this with stainless steel lock washers.

1683516836

They absolutely have to be good quality stainless - non-ferrous (check with a magnet) or they can alter the injector's characteristics.

[MWILSON1995Z]

Installed injectors this AM. Brandon Strong @ Strongspeedworks emailed me a tune and it fired right up and drove great. I couldnt get on it due to wet roads though.