Im looking at getting a BBS turbo kit for my RS and im just wondering....it says u can do no modifications like use stock injectors and ecm and all that and run 5psi safely....If i do that will i see much of a power gain...granted i know if i run a high boost and change out parts i would....but would i still see a good performace gain with 5psi on a v8..it has to wake up the 305 a lil lol

 

5 psi equals a pressure ratio of 1.34 ([14.7+5]/14.7). That ratio could also be used to estimate the increase in power, ie you'll have 1.34 times as much. Or, say your 'lil 305 has 200hp NA, with a 1.34 pressure ratio thanks to a turbo you could estimate a 70 hp increase to around 270hp. I repeatedly used the word estimate because that's what it is. This also assumes your stock ecm tune can handle the flow increase and the positive manifold pressure with out loosing its cool. Can it you might ask? Install the kit and let us know!



EDIT - I just noticed you have tbi. Not sure the kit will work for you at all. I'm sure BBS will chime in soon and fill you in.

 

ive already talked to BBS and it can work for my car...it just needs a pressure plenium like a carb would need for it to work...so we'll see what happens if i decide to get it

 

how do you plan to deal with fueling?

 

for fueling follow along the lines of the procharger install found here:

https://www.thirdgen.org/techbb2/sho...hreadid=113322

 

They kit says u can run 5 psi safely without changing anything..all stock..so i would imagine the fuel should be fine since it says u can keep stock injectors and everything...but maybe im wrong

 

For reasonable boost levels on a TBI you need the FP to rise about 2x as fast as the boost… shouldn't really be that big a problem to rig something using a couple of fuel pressure regulators, but it would take some tinkering.

 

or just an fmu....that way you can adjust your rate of fuel pressure gain

 

do you know of an fmu that will give you a 2:1 gain?

 

FYI

I tried the "stock ecm deal" using PE to add fuel. Forget it. Didnt work. Got all kinds of misses and bogs, sometimes detonation, sometimes rich in the n/a to boost transition.

If you pick up a '749 ECM, it will run your TBI under boost.

If you need help figuring out how to pin it, lemme know.


-- Joe

 

Heh, you can always dump a tank full of 116 (or assorted witches brews) in it and tell everyone that you tuned it to work.

 

Mark, I'm curious, I think the ATI TBI kit uses the FMU at 4:1, what made you decide 2:1 would be better?

 

Have you ever seen an ATI TBI setup that didn't run WAY rich? If you add a bleed to it, yea, you've basically made an infinitely adjustable FMU, but all that is really doing is offsetting and even slightly changing the shape of the response curve… the end result is that you make the typical complaint about an fmu running rich at WOT and lean at partial boost even worse, basically as you start getting into the boost you'll get lean, leaner, even leaner, WAY RICH. Where if the thing was right to start with you could actually get very close to a proper fuel curve.

As far as the ratio, do the math… figure out how approximately much more hp you'll make at whatever pressure ratio, find the percent increase and this will also be the % increase in fuel needed. ^2 that and you'll have the pressure increase needed to supply that amount of fuel with the programmed open times. Make sure that you remember to keep track of the pressure ratio across the injector. I worked this out a while back, so I don't have the exact numbers in front of me, but it appears that an actual 2:1 fuel pressure ratio (not FMU ratio, I can't figure out exactly what FMU makers are thinking unless it's "these people (including our technicians) are too dumb to understand what is going on so we'll just build this thing so it's safe and doesn't blow up engines," they can be fixed though so they work right) is almost perfect for the GM TBI setups up to somewhere in the 10-14psi range, and you never really need more then about 2.4:1 in any kind of reasonable range on them.

BTW, if you do spend some time playing with the numbers, you'll notice another interesting thing… the required optimum pressure curve for a TBI setup curves the opposite direction that it does on a more traditional multiport setup because of the low base fuel pressure and the fact that the stock regulator is not manifold vacuum referenced but will be boost referenced, as will the fmu, so the TBI setup will "gain fuel" much faster then a TPI...

 

I was just curious because in most of the applications I have seen other than very modified motors with the wideband on the dyno (with both multi port and TBI) needed the lowest (4:1) with plenty of bleed and an orafice restrictor. ATI includes the orafice restrictors in thier kits to delay the actuation of the fmu just a tad.

 

Yes, exactly. With a 4:1 FMU the bleed and restrictor cause the FMU to act slower, just like a lower ratio FMU would. If you hooked a line straight to the FMU without the bleed and restrictors it would run so rich that it would try to die when you get into boost.

 

Well, actually, not just like a lower ratio fmu, really, it's just acting like the 4:1 would with a lesser boost signal. It starts enriching later and doesn't add as much total fuel at the same boost level

 

yes, the TPI cars will run even with a 6:1 FMU! it was weird some cars actually liked it. but some bleed/restriction was almost always necessary

 

Actually, depending on the setup, TPI cars should be happiest with something between 6:1 and 10:1, and I could see situations where 12:1 would work best (for example, with 19pph injectors)

 

You guys gotta tinker with $58.. Once you get it driveable, you'll be like "FM-who?"

I had an 8:1 with sv0 24# injectors on my tpi car. Less compression than a stock L98 (8.96:1 on mine), and an a-trim .. Even with the FMU the injectors were at 93% dc at 6k, with around .890-.900mv 02..

Funny thing is.. My factory regulator. Have it set to idle around 50psi.. part throttle around 55ps.. on hard decel (high vac) it sinks to 45psi. On boost its around 60ish psi.

The BPW adder on $58 works just so "ohh yeah!".

-- Joe

 

how would eather of these work for him

http://www.superchargersonline.com/p...ber=V6X100-001
http://www.superchargersonline.com/p...ber=V6Z110-125

the 3:1 is not ideal but its beter than a 4:1

 

consider this as well

http://www.cartech.net/fmu2020.htm

 

Where can I find more info on this? Everything I've read about programming the stock ecm's is over my head. Where can I start? What exactly is $58?? What is so much better about it (drivability, performance, both)?

 

I cant even get that 412 tuned, its hard for me to consider something more complecated than a N/A motor

 

cmon...nothing wrong with a carbed 412 , i ran a 9.9 @135 with my old carb at a nice 7 psi(fuel press) no boost...no fmu

 

$58 is the bin for the sy-ty's.. factory boost code.

N/A setups are harder to tune IMO Tom. Generally on a boost setup, get part throttle right, and ae.. Then your boost BPW multiplier.. I've had more problems with flat spots on n/a setups.

-- Joe