JPrevost

If I have a dyno chart showing my torque curve, can't I somehow adjust my VE tables to match it? The dyno is from a carb of equel cfm and they're both wet flow.
I understand VE and that max torque is when the engine is highest VE%. So is there a way to adjust the VE tables with this knowledge?
If so, how would you go about doing it?
I have 2 VE tables, one is 3d (rpm x map) the other is just rpm.
I understand they can't equal above 100 or it's just looked at as being 100. So what are the calculations?
Thanks

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, Jon (350 TBI!)
91 Red My website

Pablo

iTrader: (1)

dont bother, you tune by trial and error, the numbers in the chip dont relate to reality

it should give you an idea of the curve though, your fuel curve should basically curve somewhat like your torque curve

JPrevost

Yeah Pablo, I'm not saying I wouldn't tune by trial and error, that's a given. I'm just wondering if I can have a solid starting point to work from. I don't want to have a higher VE% at 2200 when in reality it isn't until 2800 you know what I mean?
BTW, is there any real way to calculate from fuel injector size and hp/dyno to figure out an estimated value in the VE tables?

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, Jon (350 TBI!)
91 Red My website

Pablo

iTrader: (1)

There probably is, but its not as simple as that equation floating around whereby you just need the bsfc and rpm and whatnot. I think something is missing from that one. Im no expert so I cant offer any sound reasoning as to why but it seems to me that it way overestimates the amount of fuel your engine actually consumes. I could be wrong. The long and short of it is that number crunching wasted alot of my time. I just made sure i had alot of fuel capability (using that formula as a starting point) so that the injectors werent getting pushed to their limits and tuned down from there. I have way more injector than I need though. Probably better though, I read some talk about GMECMS working better with more injector than they needed something like keeping it under 80% max pw. Maybe I just dreamed that though

Dyno Don

iTrader: (7)

Put the car on the dyno with a wide band 02.
Take your chip burnner with you and make your adjustment according to the readings.
By doing this we picked up 14hp & 10 tq.

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Chronologically challenged. But still kicking!
'92 CAMARO RS
305 TBI 5/spd (now TPI)
B4C Alt.
Cam change:TRW 198/210 ,450/.460 114 LSA
Stock TBI manifolds
'85 IROC Ex.
14.94-92.00 mph
SPDC base and "350" Vortec coming soon!
'69 camaro-BB/Lenco,1050 dominators, /Pump Gas/no drugs 8.97-150+/3200lbs.
SoCal Thirdgen F-Bodies

JPrevost

How much would it cost do you think to get a few hours on a local dyno wiht a wide band o2?
Pablo, where are the calculations you speak of. I'd just like to have that base as well instead of guessing and taking WAY TOO many burns to get things right.
Thanks
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, Jon (350 TBI!)
91 Red My website

[This message has been edited by JPrevost (edited October 14, 2001).]

Dyno Don

iTrader: (7)

Our guy here charges us $75 for two cars for one hour.


------------------
Chronologically challenged. But still kicking!
'92 CAMARO RS
305 TBI 5/spd (now TPI)
B4C Alt.
Cam change:TRW 198/210 ,450/.460 114 LSA
Stock TBI manifolds
'85 IROC Ex.
14.94-92.00 mph
SPDC base and "350" Vortec coming soon!
'69 camaro-BB/Lenco,1050 dominators, /Pump Gas/no drugs 8.97-150+/3200lbs.
SoCal Thirdgen F-Bodies

JPrevost

Thanks Don, I'll have to price out some local speed shops.
Pablo, can you e-mail me at either jprevost@crosswinds or prevost.3@osu.edu with the calculations that gave you a base table. I'd appreciate it

------------------
, Jon (350 TBI!)
91 Red My website

Pablo

iTrader: (1)

www.rceng.com

they have a bunch of math there

JPrevost

That math is crap. I tried a few of the calculations and it was way off. I don't understand, I even entered fuel pressure for peak and hold injectors! It said I needed something like 100# injectors for 330hp! Those look to be only for the 1:1 injector:cylinder type .

------------------
, Jon (350 TBI!)
91 Red My website

Brent

iTrader: (1)

No its not crap.
330hp requires 165#/hr @ .5 BSFC.
165#/hr / 2 injectors = 82.5#/hr ea.

That is running them at 100% duty cycle which is not good. To achieve 83#/hr at a 80% duty cycle you need 103#/hr injectors. Its really that simple.

[This message has been edited by Brent (edited October 21, 2001).]

Brent

iTrader: (1)

Take the TPI injectors. 22#/hr x 8injectors = 176#/hr

or two 88#/hr injectors.....

and we still haven't accounted for duty cycle.

Pablo

iTrader: (1)

what brent said

the only thing is I think that formula seriously over estimates how much fuel you really need (or maybe im just over estimating my HP.. which would mean the trap speed = hp formula is off)

Brent

iTrader: (1)

In addition to Pablo's input....

The BSFC of .5 is a estimation on the rich side for a N/A application. Your engine *may* have a BSFC that is less. It's better to estimate too much injector than not enough. Lean cleans out your wallet via broken and burnt parts.

IMHO the equations are reasonable estimations that provide a good starting point.

JPrevost

I just did some math. This is what I input to find injector size:
330hp, 2 injectors, .4 bsfc, 100% duty (not gonna happen), and 20psi (on the high side for TBI). Now it said 121 lb/hr injectors! If I input that I have 8 injectors running at 46psi it spits out 20# injectors! Now let's go the other extream way with .5 bsfc, 80% duty cycle, 15psi = 175# wa..wa..WHAT am I doing wrong? This just isn't working out.

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, Jon (350 TBI!)
91 Red My website

JPrevost

Why isn't anybody accounting for fuel pressure????? Doesn't fuel pressure on a low pressure system like TBI make a BIG difference?
Let me just observe something....where do these people tell us the fuel pressure?
I noticed that some listings say TBI injectors from a Lo3 were 40#, some say it's 55#, what gives? I'm sure both of these are true but where to they say the fuel pressure!!!!! I'm pulling my hair out on this one, it's like having one equation and 2 unknowns....YUCK!
Brent, that formula you gave me shows ~100#/hr injectors, that's fine, so how to I calculate the injectors I need if there are no fuel pressure standards. Bah, this is useless, I'm going to call up Holley in the morning and have them give me the specs on how they measured 65#/hr. For all I know it could be between 10 and 20psi, lol

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, Jon (350 TBI!)
91 Red My website

Brent

iTrader: (1)

It seems you'd be better off calculating this manually. The automatic version assumes you are using injectors rated at 43.5psi.

This will tell you how much each injector needs to flow.


This will tell you approx. what fuel pressure to run.

fast_broker

iTrader: (1)

I think Holley rates their injectors at 13psi and you CAN'T RAISE IT TOO MCUH or they fail prematurely, like at 16psi+ for extended periods. That is why everyone uses the 454 pods and/or 454 GM injetors, which can take pressure abuse.