I will be using a MightyVac this spring to calibrate my BPC vs VAC tables in EBL. It appears the MV allows max vac at 85KPA.

does 80kPa = 80 VAC? If so then I can pull 5-80 VAC on fuel pressure regulator noting resulting FP and calibrate my Aeromotive FPR accordingly.

Note it comes with 2 springs that I will check seperately.

Would I then use this calc for every point value on table? NewFlow = OldFlow * (SqRt(NewPsi / OldPsi))

 

I have a vacuum pump I bought at sears 15 years ago and it will still go down to 26 inches of mercury. Stock cam car should idle at 19-20 inches of mercry wich is about 65 Kpa HTH part of your question and here is a good calculater...
http://www.cleavebooks.co.uk/scol/ccpress.htm

 

So does 80kPa = 80 VAC? ?

If 65 kPa is idle I presume the ans is yes.

I idle at 38 MAP which is 62 VAC.

TY.

 

I have to WAG yes, it's the only answer that makes sense.
&
Should compare to your WUD.

I like this lil gem http://joshmadison.com/convert-for-windows/

When I started using a MightyVac (musta been 1978, the name has changed) I looked at the gauge & decided not to use it for engine diagnostics...I have others labeled for the purpose.

 

Ron,

That's what I did when I had the Xfire and using the Aeromotive VAFPR. I used the stiffer spring and my FP was 10psi at idle goingnup to 20psi fir WOT using the 80lb BB injectors. VAC and kPa are the inversely correlated not directly correlated. That's the way I remember the cal. Now maybe RBob has changes something since then. I could try and dig out my old EBL cal for the Xfire and post the VAC values I was using. They worked pretty well and I did set them by using the MV to determine FP then calc the corresponding BPC.
I could get the MV up to 25-26" Hg. And IIRC, my idle was somewhere between 30-35kPa.

 

Hi Dom. Nice to see you are monitoring we TBI guys.
I used your values for my BPC vs VAC tables. Our engines were similar in HP. I however I am using the smaller of the two spings but may need to move to stronger spring due to my N20 added late last summer. last datalog I was fat on fuel jetting for N20. NOS recommendations are on rich side. in using your values I found I was over 100 in VE tables around peak TQ. So I needed to fudge them a bit to place VE values 90-99 40-60 MAP. May be due to spring used? I am going to calibrate both springs with MightVac this spring an see the results. I just recd the newer EBL utility version so will look at that as well. Not sure if RBob used the Aeromotive springs? I would think those tables need to be specific for the spring mfg being used. I presume those springs are linear.

i idle 38 MAP

 

The EBL Utility and previous SS's are linear. It doesn't take into account any deviation there may be in the FPR.

RBob.

 

Ron,

Haven't you been using the Xram? I used a ported Xfire. I recall that my VE's may have been in the 90's at WOT but I was watching my Inj. DC which was in the neighborhood of 75-85, so I wasn't maxed out. In addition, I had also bumped the Inj. Bias giving myself more headroom and a longer "headstart". This is a way of globally lowering VE values by increasing "effective PW".

 

I had the XRam for two seasons. Ditched it and the CF 2.00 TB's in favor of the HolleyProjection and the GM 7.4L TBI. DC is around 80-85 w/o N20 at onset of PE(includes AE shot I presume). My VE table has learned values around 90 at 4000-4500 at 70-80 MAP then the drop at over 80 MAP. Above 4500 rpms I recall are similar no learned. I may have copied what I had at 4500 rpm. I manually dropped 90-100 MAP 5000-6200 RPM VE values so as to enlean my PE as my commanded was 12.8 yet I saw 12.0. Yes, I increased the inj bias. I would need to look at .bin. I think was +10%.

 

Ron,

You may want to give the Inj Bias another look. I doubled mine. IIRC, the more accurate on the IB, the closer the commanded and observed AFR is.
Especially true at WOT where there isn't a lot of time for the injector PW. If your IB is low, much of the PW will be taken up with simply opening the injector and then needing to shut down almost immediately.

 

OK. I will look tonight at my inj bias settings and report back. With the VAFPR I am at 20 lbs WOT with GM 80 lb injectors. Same as you.
thanks again for your help.

 

OK a day late. I do not see any "injector bias" in EBL file in constants.

What I did find in tables is "correction injector multiplier-TBI". Appears as voltage sensitive. IE. 14.4v is +2.34 in ronEBL.bin vs EBL.bin is 0.00 ?

"Injector correction offset" table shows for 14.4v @ 442.5 usec for ronEBL.bin and EBL.bin is 396.8. Might that be it?

I presume it in not a PRP table?

 

Ron,

Yes It's the Inj Correction Bias. I set mine at 8 something across the board. I need to dig out one of my old EBL bins. I'm getting ready to tune my LT5. Just did a major power upgrade by adding ported heads and bigger intake cams. Running rich at idle and have an idle surge that causes motor to shut down at inopportune time while coasting. I'm thinking I may need to set Min Air. We're expecting something around 450rwhp.

 

Is it injector correction offset I found?

 

Ronny,

Dug out an old EBL bin I had and .xdf. The table used for the Injector Bias was named
Inj. Bias Added v Volts. The number I had in there was 671 in all cells. I think I may have gone even a bit higher in subsequent bins.

 

Thanks again I will move this table to what you just posted and try that. I will move the voltage beneath 14.4 a corresponding amount.

[QUOTE]["Injector correction offset" table shows for 14.4v @ 442.5 usec for ronEBL.bin and EBL.bin is 396.8. Might that be it?/QUOTE]

Not sure what to do with this one below? If it in fact is a multiplier (?) then 2.34 may be 234%? Maybe I should restore to 0.00.

 

Ron,

I was able to find an old TBI bin and look at the Inj. Bias v Volts.
I was using 732msec in all the cells. That made a difference in dropping the required VE and increasing headroom on injector DC. IIRC, my DC was ~ 75% at WOT.

 

Thanks again. I looked pretty carefullyand found only the two i mentioned. Maybe RBob changed the .xdf at some time after yours?

That one above is usec or I presume msec is same. Yours is same for all volts from what you said. I will need to look at mine (ebl.bin) and see if the adjustment varies by voltage. Regardless I will certainly bump mine from 442usec to 732.
If the above is a multiplier(2.34) would that not take my current 442 to 884usec?