Micah Richardson

Hello I am currently looking to go to a 52mm throttle body instead of the stock 48mm. Should I be looking at a computer tune, injector upgrade or anything else to make her run right? Any suggestions? Thanks. It is a 95 c4 by the way.

aklim

What exactly are you trying to achieve? Are you running out of air or fuel? If you are stock, the bigger TB isn't going to help and the injector upsize would probably hurt. What is the definition of running right? If it isn't running within spec, you need to find the problem and fix it. If you are wanting more power, none of those would work without the supporting mods. Heads, intake, headers and a dyno tune to begin with. First question you need to ask is how much money you can spend and how much you want to achieve.

MatthewMiller

I think he meant "get it running right after the new TB is installed." I assume it's running fine right now. but yeah, a bigger TB on its own will not make more power - it isn't a limitation. To put things in perspective, my 396 LT4 with heavily ported heads, different cam, headers, and ported intake probably puts down around 420rwhp; and it does just fine with the stock TB.

Micah Richardson

yes that's basically the most of it. I was told with a smooth bore intake and a slightly bigger T.B. I could get a few extra ponies and a quicker throttle response. I was t to sure if doing so without an exhaust upgrade and computer tine also would do anything for me. I dont have a fortune to spend and I also live in California so she still has to pass smog. Any less expensive ideas how to get some small hp gains?

aklim

I have seen someone who consistently ran slower times with the 1000 cfm TB in stock form. Made several back to back passes with stock and several with 58mm TB.

MatthewMiller

Can't really explain the slower times, but yeah, the main point is that the big TB didn't help. Here's a useful page from Grumpy's that discusses all this. His point is that the MAF is equally restrictive as the 48mm TB, so even if you upsize the TB you haven't decreased restriction overall. Also, he points out how much power you have to be making before the 48mm TB becomes a restriction of any kind.

aklim

Friend has SD so I think it might be somehow the air swirling in the manifold differently?

KyleF

I would say on the short runner LT1 Style manifold, this may have a slight effect. This isn't old school carbs where the engine is relying on velocity through the Venturi to mix the air/fuel. In a port fuel injection system, them velocity is created in the intake runner of the manifold down to the head and the fuel is injected into the flow in an atomized state. In a long runner design like the TPI, it has been shown that there is no gain. Maybe a hp or 2, but I feel like in those tests 1 or 2 hp is in the range of measurement error.

Unless you are going to big HP numbers, a throttle body changes is more about eye candy and the modification list than it is about actual performance. If you change one, you will not need to change anything else. The MAF will still pick up the air flow coming in, the 02 sensor will provide feed back as to what your mixture is, and the computer will do it's thing. You are changing nothing to change the air/fuel the engine consumes. The restrictions are in the heads/intake runners as far as getting air/fuel into the combustion chamber.

What you should expect is more throttle response. Since the openings are bigger, 1/2 throttle will be more open on the new TB than the old.... feeling like you are at 9/16 throttle rather than 1/2... should be just a bit more snappy.

aklim

Just stick with the basic maintenance or move yourself out of the land of fruits and nuts. Gears do not make power They just give you the illusion of it. Try that.

vader86

Larger TBs serve no use until the motor is much bigger underneath. Save the money for something else.

KyleF

I also vote for gears. A 3.54 for auto or a 3.73 if you are stick. You will notice it a lot. Especially if you don't have the performance gear already.

Mr. Peabody

Fortunately with your 95 you can have a "quicker throttle response" programmed into the computer using the stock TB. You can also change the shift points (if the 95 is an auto). A whole lot more RWHP .... no; but yes to a better throttle response but you need to find yourself a tuner who knows what they are doing.

Micah Richardson

Thank you all very much for the info, It is great! I think I will possibly just look I to a good runup and computer tine as well as many a smooth bore intake with a k&n and magnaflo exhaust. What set up do you guys reccomend for a stk. 95 6 speed... I will probably be bugging the crap out of you guys a lot with questions. I just got the car and am currently changing the radiator (which is a lot of fun so far) and need to put in a clutch kit soon. What recommendations do you guys have for any minor power and just fun upgrades that she will still pass smog? THANK YOU EVERYONE .

MatthewMiller

You can tune a 95 with Tunercat, which is not expensive but is very good. But I doubt you'll find much power with just tuning it. OTOH, if you plan to replace the clutch soon, consider a lighter flywheel. You'll be amazed how much difference it makes in acceleration, especially in the lowest gears.

How? These are cable-actuated TBs, so the PCM can't change the throttle response to the gas pedal's movement.

KyleF

Increase the speed at which the engine sees the same air flow to it. Its based of the area of opening at the throttle. All we are saying both at WOT are more than enough to allow the engine to fill itself the best it can. So, there is no gains to be had at WOT. But at any angle of throttle between closed and WOT, there is more area open with the larger bores.

vader86

You'll get very little if anything from tuning it yourself at this point. You need to wait until several things are done to increase the air flow into and out of the engine, what you have listed will not.

To pass smog, you cannot do much to the exhaust, but it is not terribly restrictive from the factory in 95. Your better choice would be 1.6RR, LT4 hotcam kit (which will require tuning), and 4.10 gears in the back.

MatthewMiller

Mr. Peabody was saying you could program a quicker throttle response into the PCM while using the stock TB. This isn't a drive-by-wire setup on C4s, so I don't understand what he's saying. The throttle response on a C4 is set by the throttle pedal and arm geometry. Nothing you can change in the PCM calibrations can change that.

Mr. Peabody

Sorry Mathew, I didn't see your earlier comment.

Back when I had the hot cam kit, headers, etc installed and the car tuned (retaining the stock TB) I noticed that with even the slightest tip-in of the gas peddle the car (95 A4) seemed to leap from the traffic light or stop sign. Last year when I had the trans rebuilt and the D44 put in, the corvette specialty shop where I have my work done was reprogramming the computer to adjust the speedo to account for the rear gear ratio change. After one of his test rides, the shop owner mentioned to me that the car seemed to jump too quickly off the line for a street car and so he programmed "a little of that out" along with some other minor changes. Afterward I was able to notice that some of the tendency to jump from a stop light had gone away.

I assumed (I know, I know) that if this was able to be done via software adjustment that one could program in just the opposite effect (a more abrupt throttle response) hense my post.

The speed shop is closed until after the holidays but next month I will stop over there and talk to them and come back with a more detailed (and perhaps corrected) answer.

vader86

They wouldnt be programming the throttle blades to come more open, they would be changing how the timing/fuel adjusts at that tip-in TPS voltage value.

MatthewMiller

vader86 is on the same wavelength with me. I'd guess that the way to go about that would be to pull a little timing just off idle. The ideal way to go would be to try reshaping the cable cam/arm on the TB, I think. I'm not sure what to make of all this - the jumpiness is not a normal issue with these setups as far as I know. It makes me wonder if there's a small glitch or dead spot in your TPS, or if it just isn't set to the correct voltage when fully closed.