Godspeed

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">You can't use a common scaling factor for the correction (across the MAP range) because while the head pressure to the injector will remain constant at 4 bar the discharge pressure will increase or decrease with vacuum..

If you have a 48 psi of rail pressure and 10psi of vacuum you have a 58psi delta across the injector - so you need to use the manifold vacuum + the rail pressure in your correction factor -
and since the table is scaled vs. manifold vacuum the correction will not be constant.

http://www.speeddemonmotorsports.com...ectorscale.xls

that is a quick spreadsheet I typed up to automate the conversion

I think there may be a bug in LS1 Edit - in the scaling of the MAP sensor. It shows flow rate INCREASING as MAP goes up - but the higher the MAP the lower the manifold vacuum (since it measures absolute pressure). Injector flow should increase directly with manifold vacuum, so it should DECREASE with MAP value.

The spreadsheet works currently with the values as stored, and will be correct (just about) if the scaling is actually 80-0kpa. If it is 100-20kpa like I suspect or something else then it may need to be tweaked.
</font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Thanks Chris, I was hoping you would step in. I will take this into consideration and revise as necessary. We are still in a learning curve with LS1 Edit and these are living documents.

<small>[ March 14, 2002, 02:23 PM: Message edited by: Godspeed ]</small>

Godspeed

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">42's are rated at 39psi by Bosch, correct?

Then at 50psi, your at 47.55564lbs

5.99201 g/sec

98 injector table shows 3.64g/sec which makes the 98 injectors more like 28.8 almost 28.9lb.

You'll have to fine tune of course, but I would do the math on g/sec as LS1Edit uses it. Doing the percentage on lbs would yield 6.01 g/sec

John </font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">There seems to be some debate as to if the SVO's are rated at 39psi or 43.5psi. I'll call RC Engineering and ask them if I can.

Also I have seen 1998 PCM's that rate them at 3.62gm/s and 3.63gm/s.

Thanks,
Jeremy

<small>[ March 14, 2002, 02:30 PM: Message edited by: Godspeed ]</small>

Reckless

iTrader: (9)

Thanks for the inputs Chris and John!
Todd

ChrisB

I just got an email back from Ken and yep, the scaling is actually manifold vacuum instead of MAP sensor readings. The spreadsheet I posted will correctly derive you a new table. You just need to enter your fuel pressure (psi), injector rated flow rate (lb/hr), and the pressure the injector was rated at (psi).

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">42's are rated at 39psi by Bosch, correct?</font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">

Pretty close 2.7 bar, or 39.15 psi or so.

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">
Then at 50psi, your at 47.55564lbs
</font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">

But remember that's at 50psi across the injector, so at 48psi of rail pressure that would only be accurate with 2 psi of manifold vacuum. The value itself will scale with vacuum. This is the main purpose of the table - since there is no vacuum referenced fuel pressure regulator this is how the pcm knows how much fuel is going in.

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">
You'll have to fine tune of course, but I would do the math on g/sec as LS1Edit uses it. Doing the percentage on lbs would yield 6.01 g/sec
</font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">

It will not matter what units you do your calculations in as long as they are all consistent. You can do them in g/sec, lb/hr, tons/century, whatever.

Reckless

iTrader: (9)

Chris...been playing around a little with the sheet. Awesome brah!

So the only values I need to change are those in C9, C12, and C13? And then plug the values into the edit?

Todd

<small>[ March 14, 2002, 03:17 PM: Message edited by: Reckless ]</small>

ChrisB

Yep, those are all you need to change! Rail pressure, injector rated flow in lb/hr, and pressure the injector was rated at in psi.

Don't know if any of the FI guys have a vacuum regulated afpr, but if you do then the spreadsheet will not work - if the FP is vacuum/boost regulated then the number will be the same across the board, and will just be the normal method posted earlier.

Chris

y2khawk

iTrader: (5)

Yep

If you're running a 1:1 referenced regulator, flat line the table with the appropriate flow numbers.

Reckless

iTrader: (9)

Thanks guys!

Godspeed

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">You'll have to fine tune of course, but I would do the math on g/sec as LS1Edit uses it. Doing the percentage on lbs would yield 6.01 g/sec</font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">But are these three and four decimal places really significant in the calculations. Are you telling me the stock fuel system maintains 58 psi of pressure to the ten thousandeths place? Also when injectors are flowed they are usually done so to the tenth in cc/min. Even so balanced injectors are only within +-1% which could be a >10cc/min difference on large injectors.

Also this shows that the stock 1998 injectors flowed 28.6# or < and after balancing were only up to 28.7#.

http://204.0.73.225/Godspeed/ls1/injector%20flow.jpg

<small>[ March 14, 2002, 05:55 PM: Message edited by: Godspeed ]</small>

John@PACE

Chris B - We are doing the same only slightly different. <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" />

New rate g/sec flow = (((new rate lbs/60)*16)*28.35)/60

To generate table I take=
((new rate g/sec flow) / (reference g/sec flow @ 0 kpa))* (reference g/sec flow @ x kpa)

http://www.paceparts.com/extras/Injector_Scaler_LS1.xls

Chris, have you done any math yet to take into consideration the different flow curve of the various injectors at different duty cycles?

John Skiba
PACE Performance

John@PACE

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Also this shows that the stock 1998 injectors flowed 28.6# or < and after balancing were only up to 28.7#.

<a href="http://204.0.73.225/Godspeed/ls1/injector%20flow.jpg</font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">" target="_blank">http://204.0.73.225/Godspeed/ls1/injector%20flow.jpg[/quote]</a>

Your test PSI was 43psi on the sheet, so if you take

260cc divided by 10.5 to get lb's per hour it's 24.7619

So that's 24.7619 @ 43psi

Plug that into my sheet and you'll see that at 58psi it perfectly matches what GM ships for the 98 injectors. <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />

Godspeed

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">260cc divided by 10.5 to get lb's per hour it's 24.7619

So that's 24.7619 @ 43psi</font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">The injectors only flowed an avg. of 255.6 cc (range from 250.2 - 258.3.) How many decimal places are significant in these conversions. Why did you round up the injector flow rate to 260cc? Even after being flowed and balanced they only did 259.7 - so you rounded up 3 tenths there. But then .01 becomes relevant later? I just want to find out how accurate these conversion numbers really are and how many significant digits to worry about. The principals I have always used is that once you round at the tenths, then you can not go back and start using the hundreths, thousandeths, or ten thousandeths places as some of these calculations do - it's one way.

<small>[ March 14, 2002, 06:28 PM: Message edited by: Godspeed ]</small>

John@PACE

I'm looking at your injector chart and using the "After Cleaning" numbers. <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

The lowest is 257.9 and the highest 260.7 and most of them fall at ~260.

John@PACE

PSJ - My math was slightly off on the other table I emailed you last week. Here is the revised version for you injectors.

New Injector Size Flow Curve 4.98 5.01 5.04 5.08 5.11 5.13 5.16 5.19 5.23 5.24 5.29 5.31 5.34 5.37 5.40 5.44 5.45

ChrisB

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by John@PACE:
<strong>Chris B - We are doing the same only slightly different. <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" />

To generate table I take=
((new rate g/sec flow) / (reference g/sec flow @ 0 kpa))* (reference g/sec flow @ x kpa)
</font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif"></strong>

That should work as you will just be deriving the ratio factor for different pressure based on the stock table (and the dividing cancels out the stock injector constant). This will compound rounding errors, but as Godspeed pointed out I do not believe the number of significant figures overall warrants worry.

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">
Chris, have you done any math yet to take into consideration the different flow curve of the various injectors at different duty cycles?
</font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">

Yeah, I will post a spreadsheet later on - you can derive the relationship pretty easily working backwards from the stock tables trends - I am just working on the logic behind it now as it isn't the way I would have expected.

<small>[ March 14, 2002, 10:11 PM: Message edited by: ChrisB ]</small>

John@PACE

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">This will compound rounding errors, but as Godspeed pointed out I do not believe the number of significant figures overall warrants worry.</font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Math was never my forte. I'm sure someone can come up with an optimized version. <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />

http://www.geocities.com/rad87gn/tech/injlinearity.html
Chris, here's some interesting info if you haven't seen it yet. It discusses injector linearity from the TurboBuick days and Precision Turbo Engineering. Maybe PTE can supply us with duty cycle vs flow rate for the different injectors and you can work your math magic on it. <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" /> I'll try to check with PTE tomorrow and see if they can provide any numbers. I don't know if they'll have various duty cycle numbers at 58psi for most of the injectors, but they should for 43.5psi. How much error in linearity do you think we'll have to deal with correcting for the higher FP?

<small>[ March 15, 2002, 08:15 AM: Message edited by: John@PACE ]</small>

Godspeed

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">So the CF for 42lb SVO injectors at 50psi would be 1.57? I think this is right?</font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Todd, you got it bud. I doubled check your math and it looks right on to me for SVO 42's @ 50psi. BTW your fuel system rocks!

-Jeremy

<small>[ March 14, 2002, 12:36 PM: Message edited by: Godspeed ]</small>

Reckless

iTrader: (9)

Thanks Jeremy! Will be putting my car back together today and doing some dyno tuning this weekend. Unfortunately, I don't have access to a wideband, so I'll have to use the O2s for now.

Todd

Godspeed

I guess I need to revise my documents. <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />

Ragtop 99

iTrader: (7)

ttt