VE #s 120 with speedpro

[quickstrike]

First off I have read many of the old posts concerning high VE numbers. I understand the relationship they have with air and the efficiency of the motor at a given volume.

I also understand how the ECU will use these numbers along with the target A/F numbers(both open and closed loop) to calculate an inj pulse width, that will be close to the desired result.

I have SD 83lb injectors they have not been flow tested. My setup parameters are all correct and 83 is the value entered for lb per hour. Duty cycle is around 50%.

My concern is that my VE numbers are very high. In the 120 range. I am running 14psi supercharged. Fuel pressure has been verified to be at 45(static) and does increase the proper amount under boost. Rails, lines, pump, etc.........is plenty(up to about 1000HP) I am only in the 650 range, maybe 750 if you count the 100HP loss from driving the charger itself.

How much off the mark would the injector rating have to be, to make my VE numbers so high? 2-3lbs? 5-10lbs? anyone have the same experience as this? Maybe I shouldnt even worry that the numbers are so high, but this seems a little excessive.

I would appreciate any thoughts on this. Thank you in advance.

Randy

 

[Otto J]

on my car the ve numbers under 18 psi are only 59 or so and it runs perfect,but my injectors maybe a bit big for my combo
OJP

 

[TurboJim]

2 things come to mind after my limited chip experience and talking to a few people.

Injector opening time could be wrong. This parameter if set incorrectly will cause an incorrect VE value and heres why. If you are pulsing an injector for 2 mS and you have your openning time set to 1mS but it TAKES 1.5mS to open the injector, the ECU isnt opening the injector early enough to be timed properly and you'll wind up a little lean. ( part of the injection event will be at a closed valve puddling for the next event) Then you'll need to open up the VE numbers to bring it back.

ALso, the characteristics of the injector. If at low PW's the injectors are lazy, say at up to 5mS they dont flow the 120% larger (or whatever) but at higher pulsewidths they do, (Or vice versa) you will wind up lean and need to raise your VE #'s to compensate for that. As in your case, if they dont flow that well ay HIGHER PW's that would explain your higher than normal VE's in that range. Also your fuel pressure will play a role here. Make sure your coolant temp trims arent PULLING fuel and you are putting it BACK in the BE trims. As an example, Harry suggested using a 48# constant with my 50's. Theyre pretty linear, but a little soggy across the board. I have since gone to 65's and required lowering my #'s by about 5 across the board

You might talk to a few people, or call Harry at PTE (assuming you bought the injectors from him) and ask him what he suggests for opening time, and what constant to use.

When I talked to Lance, and I explained I thought MY VE's were high and what would he consider a problem, he said when I get over 120%. So, I'd say something is wrong in your cal and I'd investigate and fix it before hammering it

Hope that helps.

 

[Chuck Leeper]

VE #'s hi??

QS, have you done a data log and overlaid it to see where on the VE map the engine is running??
What is the A/F correction%?
What is your commanded A/F?

 

[quickstrike]

Yes I have done several data logs and the numbers are around 197 KPA at 6000 rpm. Target A/F is 12-1 and I can tune the o2 correction to less than 3%, by altering the VE#s. The numbers are just to high. I wonder if I can find out more about my actual injector characteristics from anywhere?

I understand what you are saying about the inj delay time, and I thought about that as well. It seems to me this could be very important at an idle , but not so much once the injector is opening for 20-30ms at high rpms. I could be wrong 1ms with an 83lb fuel injector could be the difference. I suspect the inj just doesnt flow as well as advertised by some small amount.

I will go in and make sure no fuel is being pulled from another table somewhere.

Who is Harry at PTE, I am not familiar with him. I bought my injectors from another source. Can he shed some light on inj characteristics?

Thanks for your quick replys everyone.
Randy

 

[TurboJim]

Originally posted by quickstrike
Who is Harry at PTE, I am not familiar with him. I bought my injectors from another source. Can he shed some light on inj characteristics?

Thanks for your quick replys everyone.
Randy

Harry Hruska of Precision Turbo & Engine. A really good and knowledgable guy. Possibly one of the best FAST tuners out there. Tests every injector he sells so he knows each ones characteristic. He is a businessman and I dont know how apt to help he may be if you've never bought anything from them. Its worth a shot though. 219-996-7832.

Otherwise, watch here and I'm sure someone more in the know will chime in

 

[JDEstill]

Randy -

To answer your original question, let's assume your engine really has a VE of 90%. If that is true, then you are actually flowing 75% of the air the FAST thinks it is at that point (ie 120 x 75% = 90). To get the same 50% duty cycle with your injectors, the injectors would also have to be 75% of the size you told the FAST. So if those 83's were really 63's (83 x 75%), then it would all make sense.

Not saying that's what happened, just trying to answer your question. 120% VE required to get your correction to go to 0, when the real life VE is 90%, would mean the injectors are 25% smaller than you think they are.

John Estill

 

[Otto J]

isnt 12.o to 1 a bit lean up top?
i was told to set it for 11.5 to 1 am i too rich?
some one please chime in on ideal air/fuel for WOT
thanks OJP

 

[TwinTurboIroc]

every car is different....keep leaning it out until either

1) you start detonating

2) you start losing/not making anymore power

 

[NoSlix]

Exactly. Every motor is different. The 310ci liquid to air intercooled, T76 powered motor in my drag radial mustang likes to run at 13:1 af ratio with 20psi in the intake. Everyone will tell you bs, but it's been verified with 3 different widebands.