150 max VE for FAST?

[Not a 350]

This may be an easy fix, but I can't find an answer anywhere.

Both under DOS and Windows versions of C-Com WP, I can't set VE to a number higher than 150 in the fuel tables. Is there an upper limit? What do people do for high boost cars?

Thanks,
-Aaron

 

[TurboTR]

Apparently you may have found the upper limit 150% should serve to cover the VE range in most cases, assuming everything else is set and working right. Personally I like to see about the 3x range typical at idle (for no other great reason than comfy with that number to start with, and the resulting upper range), and will sometimes adjust the inj const slightly if need be to get it around there. On the typical Buick v6 combos I've seen this then pans out to around 80-90% at full boost with ported prod style heads and moderate cams. On S2 heads with bigger sticks, maybe even +30%+ higher volume flow at full boost Thump. Similar on v8 and other combos.

In general, increasing MAP has an ~ incremental increase effect on engine VE. In other words, if you look at the VE table graph from the side, with MAP increasing from left to right, then it will also typically slope upwards gently from left to right. Neglecting the lower corner area of the map where the throttle is closed of course- closing the throttle has a huge effect on engine VE obviously It sounds like you are maybe expecting the VE to scale big with increasing MAP- in general it won't.

Not sure why yours is showing such high VE numbers, but it seems that something else is not yet set quite correctly IMO.

TurboTR

 

[HighPSI]

Sounds like you are having another issue. I ASSume this is the same car that has the high VE's at idle.

 

[Not a 350]

Yeah, this is the same car with the high idle VEs.

Would a faulty MAP sensor cause the problem? The car is using a stock GN 2bar. If that is not the problem, I am beginning to think that the 72# injectors my friend bought are really 55#'s.

TurboTR, thanks for the explanation... I am used to tuning N/A cars and have never had any time on a boosted car.

-Aaron

 

[HighPSI]

Originally posted by Not a 350
Yeah, this is the same car with the high idle VEs.

I am beginning to think that the 72# injectors my friend bought are really 55#'s.

That would explain a lot.

 

[Not a 350]

New info, no luck

We put in a known set of 83# injectors, double checked the MAF and fuel pressure, and retuned the car. Now it wants to idle at 95 VE. The exhaust smells fine and the car idles smooth so I don't think it is a bad O2 or anything like that. If I lower the VE the car goes lean quick and dies around 75 VE.

The FAST calculates fuel from the following, right?

VE
CID
# of cylinders
Injector size
MAP

I have checked them all and it is still running weird. I even loaded a tune from another car to make sure there wasn't some hidden value mucking things up. What is going on?

The car idles at 51 VE when I doubled the CID in the FAST, but I don't want to band-aid the tune like that. Please help.

-Aaron

 

[HighPSI]

What is your MAP value with the key off?

 

[norbs]

Maybe your using a 2 bar map and you think its 3?

 

[TwinTrouble]

Hey guys, this is my car. With the engine off, the MAP is 96kpa. I bought a MAP for a 87 GN, so that is a 2 bar, right?

 

[Not a 350]

With the key off it is as follows:

When set to 1 bar: 67 kpa
When set to 2 bar: 99 kpa
When set to 3 bar: 144 kpa

-Aaron

 

[norbs]

looks like you have a 2 bar map, correct

 

[Not a 350]

Yup, so basically, we know the following is correct:

MAP
CID
# of cylinders
Injectors size

That with VE is all the map uses to calc fuel, so I have no idea where I could be going wrong. Injector opening time is 1.0 ms, which I have read is fine for 83 # injectors.

-Aaron

 

[norbs]

Try another fuel pressure gauge maybe? Huge vaccuum leak at idle? whats the idle KPA??????????

 

[Not a 350]

We have used two guages, although both are referenced off of the same AFPR. Both read the same pressure.

Idle is in the 60 kPa range if I remember correctly.

-Aaron

 

[ijames]

MAP
CID
# of cylinders
Injectors size

That with VE is all the map uses to calc fuel, so I have no idea where I could be going wrong. Injector opening time is 1.0 ms, which I have read is fine for 83 # injectors.

Doesn't the FAST take MAP and rpm to index into the ve table and also into the target afr table, then use both ve and afr along with mat, cid, and injector size to get the injector pw (and then apply the opening time and battery voltage corrections)? If you are in closed loop and add to a ve cell the O2 sensor correction just takes pw back out to get back to the same target afr, right?