My car is a 92 305 TBI Auto. The only mods are Flowmasters, Hi-flow cat, K&N. Will I gain anything by installing a performance chip. I was told that it would change my shift points (which would help fast acceleration) and improve the mpg. Then again, I've been told that the only reason to install a chip is when you have major engine mods like cam, heads and what not. Some one who has dealt with this directly, please educate me!

 

The only REAL, NO BS way to tell is to scan your ECM and collect data to determine if there's anything needing to be adjusted.

SWAG is you haven't made enough changes in the "VE of your engine to need much tuning. But that's just a guess, there's no way to tell without scanning it.

Maybe you could hook up with one of the guys in your area that does his own tuning.

That's the NO BS answer.I'm sure you will talk to a lot of people that will 'pretend' to know what specific tuning you will need without ever seeing your car.
Remember, there's a lot more people that can "talk the talk" than can "walk the walk".

 

ya that seems to be the trend, rather than get educated answers I usually get opinions appreciate your response

 

And whoever told you that it would change your shift points obviously doesn't understand that your transmission, like any other 3rd gen cars, isn't computer controlled.

 

really? thats good to know, thanks. the guy who told me that was a damn Mustang owner so thats probably why he didnt know what he was talking about

 

educate me on this. would he benefit by advancing at distributor a couple degrees of spark and forget the chip? also how about adding a fuel pressure gauge and set FP at 13 lbs if at currently 11?

 

By advancing the dizzy you're effectively increasing the spark advance everywhere (duh) and so at idle, you'll have more timing, and same with WOT, which can be hard to "feel."
All in all this isn't a bad way to start if you've got a larger cam and aluminum heads.
The problem with fuel pressure is that the shift in fuel is everywhere, which is a problem with larger cams and better heads. What happens with a larger cam is the shift in VE. It'll usually (depending on the cam specs) move the VE to a higher RPM. The heads and intake (power adder?) will effect the actual vol eff of your engine, not so much the cam. The cam will also reduce the VE at lower engine speeds. So increasing the fuel pressure with stock tables will only make your engine run safer (rich at low engine speeds). This is why tuning is so important. The heads and intake will make the VE while the cam gives you a "sweet spot" so to speak which will be based on engine speed.
So fuel pressure is again a way of ruffing in a tune but is still not going to be as close as real eprom work.
Also, by advancing the dizzy mechanically you can get into trouble with too much timing (run away knock) depending on the stock table. There is an "initial SA" in the eprom that should match your dizzy's actual advance. If it doesn't, then the "max advance" will be incorrect. So let's say that you've got max advance set to 43 degrees, initial is at 0. When you advance the dizzy 6 degrees and don't change the initial in the eprom you can get too much timing at high engine speed high vacuum. Basically if the ecm calculates 43 degrees of timing it'll dead head there but add on another 6 degrees and you've got 49 degrees of advance! That's just another reason to do it right and do what we do here; Dizzy set between 6 and 10, fuel pressure is set and forget, so long as it's giving you good duty cycle numbers around 90% for Peak and holds and 85% saturated.

 

so will it benefit me or not JPrevost, u kinda got a lil to technical for my rookie expirence

 

Unless you want to learn how to do your own tuning then you can pass on the DIY stuff. The engine itself is still stock so there has only been minor changes to the volumetric efficiency. With heads, cam, etc. your making global changes to the engines volumetric efficiency and spark requirements so then tuning is definatly in order. The off the shelf stuff 'Proms' are useless and will have little effect other then making your wallet a tad lighter. The one I had from Hypercrap (got it for free) just had added fuel at higher rpms and added in timing but since the injectors are already maxed out theyre effectivly just adding in timing, which can cause problems.

 

so any of you guys have any ideas on what i SHOULD do? I want to get it as fast as possible w/out having to get inside the motor, its got alot of miles and its bound to blow up sometime, i figure i'll drop a 350 in it when that happens, but until then I have to stay relatively simple. Headers? Shift Kit? Anything?

 

Headers + cat + catback exaust for another car like a TPI with a 3in exaust are good mods. The stock exaust is small and keeping any part of it or any replacement part meant for a tbi car will jsut maintain those restrictions. IIRC, the exaust is almost the same as that for the LG4. Prom burning could help. The stock tuning is set up to run on the rich side at WOT. Leaning it out would help increase power, but youd risk destroying your cat. Some also swap in gears and a posi carrier. The added traction is a definate plus but the numerically higher gears wont help much as a stock tbi already is in its powerband when you launch and it doesnt have the top end to really take advantage of improved gearing.

All the basic mods have been covered over on the TBI board so a search will bring them up.

 

Not to hijack the thread, but how is it that the injectors are maxed out? The computer tries to make the pulse width wider to put in more gas, right? Do the injectors limit that somehow? I assume they weren't open 100% of the time, or were they?

I realize this is newbie stuff...

 

i would like to know the answer to that as well.

 

This was on my ecm, but I suspect the others where similar. After around ~3000 rpm at WOT the pulsewidth is almost at the maximum alowed before the injectors are jsut full static and stuck open all the time. At high rpms, the injectors tracked right along the limit for the pulsewidth. I think it was something like 96% duty cycle. Jsut something to keep in mind is that with the stock injectors there wont be enough fuel available to maintain the commanded AFRs on a modified setup (heads, cam, exaust, etc.). The plus side is that the stock tune runs rich at WOT so there is some extra fuel available if you dont mind running around 12 or 13:1, of coarse there wont be any safety margin as the injectors are just about static.

 

appreciate the knowledge!