Yea, so I don't know what a TPI is. I know that my engine says it and I was hoping that someone could type in a crash course for me.

 

By no means am I an expert but I will give you a crash course to the TPI that you have on your car. It stands for Tune Port Injection. In other words there is a computer along with a ton of other sensors that maintain the air/fuel ratio in the motor. The TPI consists of a throttle body, plenum (the square thing behind the throttle body, lower intake, fuel rails, and fuel injectors. I know there are other things but this is simple. The injectors that you have spray fuel into the cylinder at a rate of 19lbs per hour. The 350's have 22 lb/hr injectors.

The computer maintains some things but if a sensor goes bad then it can only compensate just so much. That is about as high level as you can get and like I said there are others in here that are mechanics or selfmade mechanics that know a lot more. Good luck and happy motoring.

 

ok, the other guy explained it pretty good but ill throw in some info.
Little history...
TPI was the best form of FI GM had made for sports cars. After the failure of Cross Fire Injection, GM had went back to carbs for performance. GM developed the Tuned Port Injection system desgined for the 305 cubic inch motor. the 305 or 5.0L engine was supposed to be the super comprimise for performance and emissions/fuel economy. TPI was the best answer for streetable performance and put Fbodies back on the map. The third gen fbody was realy made for handling, not speed as the CFI engine in 82 put out a sorry 140hp or something like that. TPI was the first step in the performance fuel injection direction. TPI is a great system for the street. It has tons of low end torque due to the desinged intake. In 87, 350's were brought back, and was given the TPI set up with different injectors and sensors. They were brought back into fbodies and remained the top engine choice till the end of the generation. TPI does have many faults. Most complained about is it has a very short power band;it usualy chokes off around 4,500-5k rpm. Except for 85, all 305 TPI auto's got a weak "peanut" cam which didnt produce as much power as the 5spd 305. The 305 TPI 5spds got the 350's cam. TPI was replaced by the Gen II LT1 engine for the 4th gen fbodies, which was then replaced with the Gen III LS1 small block. LT1's and LS1's are the offspring of TPI development.
Little tech
TPI runs of a OBD I series computer. It has 8 individual injectors. 19 lbs per hour for 305's and 22's for 350's. ALL TPI systems are the same. Only difference is electrical, and in the case of corvettes, they have a different intake base because of egr placement. TPI runs off of a preset program and calculates fuel and spark by measuring air(mass air flow or manifold air pressure), engine detontation(knock sensor), unburned fuel(02 sensor) and a large group of other sensors. TPI intake consits of a TB, Plenum, Runners, and Intake base. There are many ways to tune and enhance the performance of your car.
Performance.
Easy stuff for TPI cars to gain peformance is exhaust work. Then there is always working on the intake sytstem itself by porting the intake parts and making them flow better to increase the engines power band. At some point, engines want to suck in to much air and the TPI system can not provide it. You will see many people ditch the sytem for a better flowing intake like Holley's Stealth ram, TPIS's mini ram, and Accel's Super Ram. If you want to keep the TPI set up, there are high flow intake bases, runners, and throttle bodies to enhance flow. I do not recomoment getting a "chip" for your car as you will get a e-beatdown if you bring it up here on the site. We have a board here in where people will "burn" or create there own chips or PROMS to squeeze out all the performance. Basic bolt ons right now will help you to get going and make your car faster. good luck and welcome to TGO.

 

Don't feel bad about not knowing anything. This is a great board for info and help. As you can see from the above posts.


I love this place!

 

Thanks for the info... but i have another question. The guy that I bought the car from put some performance chip in the car... so its there, don't burn me, not my call. However, he did give me the stock one along with the aftermarket one in the car. Would it be to my advantage to put the stock one back in?

 

Welcome! I'm fairly new to this too, but I'm having a blast. I learn something new everytime I get on this website. You came to the right place for questions, these guys are great for info. Good luck with your car!:rockon:

 

I would stay with the aftermarket chip. To be honest, the new chip probably doesn't do much. The companies that make them have to keep them emissions legal, AND they have to be fairly compatible with EVERY car that they're intended for. That means that they can only change VERY MINOR little details. If you were to run your car back to back with the 2 chips, you MIGHT see a very slight difference in your times at the track, but you'd probably never feel it in the ever popular "butt dyno" which means the advantage is too small to feel when you're in the car. Now don't get me wrong, a tenth here, and horse there can add up, but it's just not worth buying.....but like you said, it's already there.

Not that you're into this just yet (I'm not either) but for the same money as you would pay for an aftermarket chip, you can get into burning you're own chips. I think Bigals mentioned this. That takes a bit of know-how and trial and error but you can see AMAZING results. If you're ever into it, check out the Prom burning forum. Those guys are amazing. Heck, just go over and read a little about it, you'd be amazed what you can learn. If you get into modifying your car with more than just the basics, you'll need a custom chip at some point. There are a few places that will burn a chip to your given modifications, but they not tested with trial and error to your EXACT engine, so there not as good as a custom chip that you've burnt and tested yourself on your own motor. For the record, I think most of us on this site mod our cars in one way or another, and MOST of us don't burn our own chips.

A quick note. I'd bet that your custom chip is set to run on a 160 thermostat, instead of the OE 195. That's not a big deal unless it was the other way around. OE chip set to 195 and you run a 160 stat...that's no good. He should be fine, right guys?

 

And to throw out an analogy as to why the stock TPI LTR (long tube runner) set-up doesn't flow at high RPM's:

Imagine sucking air through 2 straws. First you have the "stock" straw, which is a skinny Wendy's straw. Under normal breathing, you can get all the air you need...same as your engine breathing during normal driving. Since the straw is skinny, the air is moving pretty quick. This fast moving air almost has a ramming effect in your engine. The long tubes of the stock runners are "tuned" to provide this effect. When you run out of your car because you just realized your Junior bacon has no bacon and you want bacon, you need MORE AIR, because you are running. At this point you can't get enough air through that cheap a$$ straw. Just like the OEM LTR set-up.

Now we go to Mcdonald's. They have those huge mac daddy straws....or a "TPIS Miniram" as Bigals87Z28 mentioned. They provide more than enough air under normal driving/breathing. So much air that the air actually isn't moving that fast, and in some cases....can actually HURT low end torque. The argument as to when and where you actually LOSE performance is a never ending discussion on these boards, since there are so many different combinations. Anyhow, when you start running/driving hard, that's where the huge Mcdonalds straw/aftermarket intake shines. It flows more than enough air to run high RPM's and make a lot more power....and to suck down more Mr. Pibb.


Did you guys know that Mcdonalds actually started using larger straws so we'd drink MORE...back when you had to pay for re-fills.

No joke.

 

So, you're telling me that before I worry about chips or sensors or any of that TPI stuff that up there...if I want to improve performance, I should just start with exhaust and intake stuff? Is that what i'm getting or was that all just for information... don't get me wrong, I love the fact that everyone is willing to take 30 minutes and tell me a little bit about my car, but should I worry about air flow before chips?

 

That's what I got out of that.

 

Yes...and no...well kindasorta.

Anyone feel free to jump in and help here.

First things to do in my opinion.

Right off the bat, do a full tune up. ALL the fluids. Trans/diff./oil/EVERYTHING( or at least check). Plugs wires cap rotor coil. I'd recommend having the injectors cleaned. Depending on your mileage. I had mine cleaned at 150,000 and it was like driving a new car. The throttle body can get pretty gunked up too, so you'll wanna clean that out. I'm sure I'm missing something. Anyhow.......after the tune up:

K&N air filters
Catback exhaust
headers

I know I'm gonna catch h e ll for this, but assuming you've got a automatic, I'd get a torque converter. Since you've got a 305, you've got at worst...what do you guys say? 3.23:1 gear ratio??? At the worst? That's not bad. That automatic SUCKS the power outta that 305. The TC will have a huge "butt dyno" increase.

Regardless of what you do. I think most all of us will agree that the aftermarket air filters/K&N should be the FIRST. After that comes the exhaust system.

You don't need chip till you mess with heads and a cam. You can do all the intake work you want without a chip, but without heads and a cam, the intake won't do much for ya. Some...yes, but not enough to make huge gains.

Best thing I can recommend is to read this site as much as you can.

 

Now, a TC is a good, but its not the auto thats killing the 305. The 700R4 is actualy pretty good and doesnt kill engines as much as its blue oval counterpart. What kills the auto 305's is the cam. The cam BLOWS A$$!! You probably have 2.77 or 2.73's in the 305 auto. TC will not add power, but will cut some time off your et. Dont mess with chips untill you have played around with internals. If you plan on keeping the 305, i sugest you get a decent cam(ZZ4, LT1, LT4 cam) and heads. Improve on what you can now. Exhaust should be first for you. Intake also. A little CAI and some plenum porting should be cut some time off your 1/4.

 

You guys are awsome!

 

If you dont want to go ***** out on the cam you can get a stock 350 cam for your 305 and it will be about as quick as the 305 w/ a T5 and really cheap. Also if you are looking for headers the 1 5/8" are about all that you need with the 305. I have been doing a lot of reading on this subject and have come to the conclusion that you do not need 1 3/4" until you are running a 355 or larger that needs to get rid of lots of fuel. Also if you get a nice 3" catback or have a custom 2 3/4" built like I did and you will be breathing rather nicely. Different systems different sounds. I have Magnaflo and you cannot hear it in the car at all but outside it is nice and loud. Dynomax is pretty much the same. Flowmaster American Thunder is popluar and it is loud all the way around, they make a 3" system that is nice, one of my friends has it. I have also heard good things about the Hooker system but have not heard it first hand. So with a full exhaust and an air filter you are looking at or around $700 or more. That will be a real nice start for a newcomer.

 

the cost and timeyour gunna take for putting in the L98 cam would be a waste. IF your gunna swap out the cam, get something with some lift man!! your gunna have to mod the heads, but there are tons of cams out there that will work with stock heads.

 

Cams... Heads....

 

what do you want to know? what they are?...

 

yea... i have no clue what this stuff is. I feel stupid! but I hear that i came to the right place. Sorry.

 

Don't feel stupid. It's better to ask questions than to not ask any. You don't learn anything by not asking questions.

 

hehe ok
Ill explain this as best I can and then im going to sleep.
Your engine is a Overhead Valve engine or OHV. Now all OHV engines have one cam, and its placed right above the crank. The cam shaft has many lobes or "bumps" on it. Im sure you have seen a cam before.. if not, ill post a pic of my ZZ4 cam.
Ill talk a little about the heads and then ill put the two together. On any V style engine(v4,v6,v8,v10,v12,v16, etc) It has two heads, one to go on top of each side of the V. Now the head is where the action is. The heads on your engine have a combustion chamber that sits right above the piston thats in the block of the engine. The head gets bolted onto the engine. Now, the chamber on small block chevy's have a kidney or a D shape chamber. In the chamber are usualy two valves, one for intake, and one for exhaust. Intake valves are always larger. Now the valve stems up to the top of the head, to where a spring is attached and a rocker arm is placed. Now here is where the cam comes in. The cam spins around like a log, and the bumps push up a lifter that sits on the cam. There are 16 lifters. Each lifter pushes up a push rod which interns pushes one side of the rocker arm up, and forcing the other side down, which pushes the valve down, which will either open the intake valve or open the exhaust valve. Now what people do is get a cam with taller lobes or lobes that have different spacing. This all effects the engines performance. All that is very technincal for you right now. Now the Intake mainfold sits ontop of the engine and is bolted to teh heads. The air travels in to the intake, down the runners, mixes with air, and into the intake part of the head... the intake lobe or bump slides the lifter and pushrod up, which makes the valve opens up, the piston slides down and sucks in the air. as the cam spins, the valve starts to close. The piston goes up to a point where its top dead center, and the spark plug ignites the gas and air mixture, causing an explosion, which forces the piston to go back down again. Now the exhaust valve lobe is pushes up the lifter and pushrod, which opens the exhaust valve open, and the piston goes back up and discharges the the burned mixture out to the exhaust. Better flowing heads and larger cams will increase the size of incoming air into the chamber, therefor making more power. I hope that helps.

 

and pics of heads and cam...

these are SR 305 torqer heads.


here is a cam and lifter set

 

ahhhh... i think i got ya.... but i am definately going to pop my hood and try to identify some of this stuff. Thanks again