Throttle body porting 3.1 L

Post information about intake systems. Either purchased or custom made
beretta
Registered User
Posts: 957
Joined: Wed Feb 02, 2011 7:33 pm

Throttle body porting 3.1 L

Postby beretta » Fri Feb 11, 2011 6:53 pm

some of you may have seen under the post for a new 3.1 L throttle body. that i have recently ported mine.

So i ported it out as much as i possibly could without having a bunch of holes every where lol, and i ground down a 3400 throttle plate to fit, so i got it finished up today and installed and having some issues with my idle.

I just drove about 50 miles and when i let off to change gears the rpm doesnt drop right away and takes a few to 10 seconds for it to idle down. when i come to a full stop it wants to rev around 1500 rpm and slowly drops down to normal but if you let it idle for a few seconds it will start to rev up on its own to somewhere around 1500 to 2000. if i tap the throttle it comes back down and sometimes its sputtering a little then clears up then revs itself up.

My car is a 1988, with a 91 3.1 L 5 speed, and i have a wire harness from a 3.1 L 5 speed beretta with a 3.1 ecm and never had problems until i ported this TB.

I know the throttle plate is closing all the way, and theres a plug you can pop out and an adjustment screw for the throttle i have this cranked down as far as it can go so the plate would be fully closed, if i just barley turn it, it jumps my rpm way up.

I thought the ECM was supposed to self learn the idle.. not sure whats going on, maybe my Idle sensor is not working right....

Other then the idle issue it seems to work pretty good and can feel a difference in the throttle response, its a little more snappy and when it does idle down it kinda sounds cam'd out.

Any suggestions on what i should try ? i think im going to change the idle sensor and see how that goes. im pretty positive that i dont have any vacuum leaks, i never did before and i hooked everything back up with this TB.



User avatar
Money pit Beretta
Registered User
Posts: 6362
Joined: Thu Jul 26, 2007 11:36 am
Location: Kansas
Has thanked: 2 times
Been thanked: 9 times

Re: Throttle body porting 3.1 L

Postby Money pit Beretta » Fri Feb 11, 2011 8:58 pm

You sure your TPS is not bad. Kinda sounds like it.


keep'em flying!

beretta
Registered User
Posts: 957
Joined: Wed Feb 02, 2011 7:33 pm

Re: Throttle body porting 3.1 L

Postby beretta » Sat Feb 12, 2011 12:46 am

i figured it out.... the throttle body i used was off a 2.8 L and it has 2 little tiny holes near the throttle plate and the one from the 3.1 only has 1, so not sure about the big difference there.

So i ported out the one that was on my car to fit my newly made throttle plate. and also i figured out a faster way to port it out, i forgot i had a couple hones LOL, 1 thats for brake cylinders i actually bought it to do a hedge trimmer engine, and i have 1 for doing car engines. i just used the small one and honed it until the throttle plate fit tight.

Put it back on the car and its idling maybe at 1,000 which is not bad i guess, and it comes back down after i hammer on it quickly so its not lagging out now.

Ill mess with it tomorrow and see if i can get it to come down a bit more but its not bad and seems to work normal. i was in 4th gear doing 60 KM/h and kicked it down and it was braking loose all over the road but then its snowing too LOL just a skim on the roads right now.



User avatar
Money pit Beretta
Registered User
Posts: 6362
Joined: Thu Jul 26, 2007 11:36 am
Location: Kansas
Has thanked: 2 times
Been thanked: 9 times

Re: Throttle body porting 3.1 L

Postby Money pit Beretta » Sat Feb 12, 2011 10:54 am

Room for growth. Room for contraction. No room= stuck throttle.


keep'em flying!

beretta
Registered User
Posts: 957
Joined: Wed Feb 02, 2011 7:33 pm

Re: Throttle body porting 3.1 L

Postby beretta » Sat Feb 12, 2011 8:09 pm

ok so this morning i fired it up and was idling at 2500, so i took out the idle sensor and i pulled the plunger on it all the way out and put it back in so it would be closed all the way, and i left the wire unhooked from it, and now i adjust the idle with the set screw on the throttle. idling around 800 rpm now which was right around the same place it was before.

It definatly works great, it has more low end power for sure and gets up there faster, now when it gets warmer im going to the wreckers and find some more throttle bodies and top intakes. now that i know i can use a hone to bore the TB, ill hone it out until something brakes and measure and then ill know to stay below that point and i will know the max i can hone it and get a larger throttle plate in there.

But without doing the intake as well to match the bore of the throttle body to the opening on the intake i dont think it will get the maximum power out of this...

It really does work good right now though, i can feel the difference in the pull. and i couldnt ask for it to run any smoother.



User avatar
scd88ga
Registered User
Posts: 1828
Joined: Mon Jun 28, 2010 9:02 pm
Location: Wisconsin Rapids, Wisconsin
Contact:

Re: Throttle body porting 3.1 L

Postby scd88ga » Sat Feb 12, 2011 8:13 pm

I like a working idle air control valve myself, but to each their own I guess...


'94 Quad 4 H.O. 5 speed Z26, Red & Rare! 1 of 896 Quad Z26's and of those it's 1 of 167 red paint/gray interior!
Need A Quality Used Part? Contact me at Posihead Auto Parts!
https://www.facebook.com/pages/Posihead-Auto-Parts/336733779691724

beretta
Registered User
Posts: 957
Joined: Wed Feb 02, 2011 7:33 pm

Re: Throttle body porting 3.1 L

Postby beretta » Sat Feb 12, 2011 11:10 pm

well... it idles fine i dont see a problem with it not being hooked up for the time being.. when its hooked up for some reason after i go for a drive it wants to stay open and hold my idle around 2500.

Doesnt have any effect with it not hooked up other then my idle stays where i want it to.



beretta
Registered User
Posts: 957
Joined: Wed Feb 02, 2011 7:33 pm

Re: Throttle body porting 3.1 L

Postby beretta » Sat Feb 12, 2011 11:16 pm

Image



User avatar
scd88ga
Registered User
Posts: 1828
Joined: Mon Jun 28, 2010 9:02 pm
Location: Wisconsin Rapids, Wisconsin
Contact:

Re: Throttle body porting 3.1 L

Postby scd88ga » Sun Feb 13, 2011 8:56 am

It DOES have effects to your car by not being hooked up, it's there for a reason...

An idle air control valve is an electronic motor which adjust idle speed. The IAC valve is usually mounted to the throttle body. Some cars don't have IAC valves, instead they have a mass air flow sensor. An IAC valve is used by the computer to change the amount of air flow.

An idle air control valve is a three wire system. It consist of a five volt wire, a ground wire, and a sense wire. The five volt wire is used with the ground wire to move the IAC motor. The sense wire is a direct line for the computer to monitor how far in or out the valve is. The position of the valve in or out is know as steps. The computer reads the steps and compares that information to the current idle speed of the engine. It can then determine how much to increase or decrease the engine idle speed. The computer can also adjusts the IAC to compensate for increased load on an engine. An example of this would be turning on the air conditioning or the rear window defroster.

The IAC has a cone shaped tip called a pintle which protrudes into an air passage. The amount of air in this passage affects the engine idle speed. The pintle is on the end of a rod that has a spring around it. The rod is connected to the electrical motor which moves the rod and pintle in and out of a passageway. If the rod and pintle is pulled in by the IAC motor, the airflow is increased to raise the idle speed of the engine. The opposite will happen if the rod and pintle are pushed out. The airflow in the passage will decrease which in turn will lower the engine speed.

I'd rather have a STOCK size throttle body that worked over a slightly ported one that's "rigged"...


'94 Quad 4 H.O. 5 speed Z26, Red & Rare! 1 of 896 Quad Z26's and of those it's 1 of 167 red paint/gray interior!
Need A Quality Used Part? Contact me at Posihead Auto Parts!
https://www.facebook.com/pages/Posihead-Auto-Parts/336733779691724

User avatar
Money pit Beretta
Registered User
Posts: 6362
Joined: Thu Jul 26, 2007 11:36 am
Location: Kansas
Has thanked: 2 times
Been thanked: 9 times

Re: Throttle body porting 3.1 L

Postby Money pit Beretta » Sun Feb 13, 2011 2:41 pm

Don't turn on the AC. You won't have air to cover the higher idle.


keep'em flying!

User avatar
Cliff8928
Administrator
Posts: 1774
Joined: Wed Mar 03, 2004 10:03 pm
Location: Long Grove, IL
Has thanked: 8 times
Been thanked: 10 times
Contact:

Re: Throttle body porting 3.1 L

Postby Cliff8928 » Mon Feb 14, 2011 12:02 am

scd88ga wrote:An idle air control valve is an electronic motor which adjust idle speed. The IAC valve is usually mounted to the throttle body. Some cars don't have IAC valves, instead they have a mass air flow sensor. An IAC valve is used by the computer to change the amount of air flow.

An idle air control valve is a three wire system. .......


The IAC is 4 Wires. Two coils with two wires each.

A MAF has nothing to do with an IAC, at least as far as GM is concerned. The only GM cars without an IAC have a ETM (drive by wire) as far as I know.


Cliff Scott
Image

beretta
Registered User
Posts: 957
Joined: Wed Feb 02, 2011 7:33 pm

Re: Throttle body porting 3.1 L

Postby beretta » Mon Feb 14, 2011 1:05 am

well its the middle of winter here so i wont be turning on my air any time soon.. i suspect my IAC might be faulty, it will idle great until i drive it around a little then it wants to stay reved up and not idle down also when it did idle down it would slowly rev back up on its own, so i pulled the rod all the way out stuck it back in so it would be closed and pulled the wire.. FOR NOW.. until i can get another IAC.

the throttle body works amazing it pulls alot harder then it ever did and even seems to be better on gas. the car was on empty yesterday and i put 40 bucks in the tank, i drove 4 trips of 80 KM each way. between yesterday and today.. and it still hadnt burned all the gas i still had between empty and half a tank. so i drove like 320 KM on about 30 bucks in fuel and its $1.12 /liter here right now.

It used to cost me almost $20 in gas to do 1 round trip i dont 2 round trips this time and used less gas, and i was not light on the throttle either.

My throttle body is more then just a little polish, the throttle plate is larger and i bored it out and ported the taper going in and wet sanded it for almost and hour started with 300 grit paper and finished with 600 grit.

Im going to pop off my top intake tomorrow and hone out the opening going in to match it up the the ported throttle body and trim the gasket a little, im not going to bother touching anything else in the intake right now just hone out where the throttle body bolts and match it up with the size of the TB.

Im still running the stock air box as well, a friend of mine has a aftermarket filter and tube i was supposed to go check it out a couple days ago but havent made it yet.

Keep in mind, im not trying to make a race car, i had the spare throttle body and had some spare time and wanted to try and see what i could do with it and how it would work. im thinking i might find a couple more and experiment a little more with them and see what works the best, the one im running now seems to be working really good though. i would not have thought that little bit larger and a good polish would have done a whole lot, but you can feel the difference in the power, takes off alot faster and it revs out higher faster too. Im happy with it, other then i need to figure out whats going on with my IAC



User avatar
scd88ga
Registered User
Posts: 1828
Joined: Mon Jun 28, 2010 9:02 pm
Location: Wisconsin Rapids, Wisconsin
Contact:

Re: Throttle body porting 3.1 L

Postby scd88ga » Mon Feb 14, 2011 1:23 am

Cliff8928 wrote:
scd88ga wrote:An idle air control valve is an electronic motor which adjust idle speed. The IAC valve is usually mounted to the throttle body. Some cars don't have IAC valves, instead they have a mass air flow sensor. An IAC valve is used by the computer to change the amount of air flow.

An idle air control valve is a three wire system. .......


The IAC is 4 Wires. Two coils with two wires each.

A MAF has nothing to do with an IAC, at least as far as GM is concerned. The only GM cars without an IAC have a ETM (drive by wire) as far as I know.



I just copied and pasted that crap from some site, it was merely to show what the purpose of the IAC, what it does and why it's there. I know GM ones aren't the same as the one described, but it's just general info to give a general idea.


'94 Quad 4 H.O. 5 speed Z26, Red & Rare! 1 of 896 Quad Z26's and of those it's 1 of 167 red paint/gray interior!
Need A Quality Used Part? Contact me at Posihead Auto Parts!
https://www.facebook.com/pages/Posihead-Auto-Parts/336733779691724

User avatar
90GTZHO
Registered User
Posts: 1068
Joined: Sun Nov 02, 2003 11:54 am
Location: Paulden, AZ
Has thanked: 1 time
Contact:

Re: Throttle body porting 3.1 L

Postby 90GTZHO » Wed Feb 16, 2011 10:33 am

Ya know dude, i was looking at your pic up top, and i see there is a nice gap in the lower left corner of the unit that is a perfect bleed spot for air. If your engine ran fine before this mod and didnt after, you prolly dont have your plate cut down properly to the point that it makes a good seal all the way around the blade. when the factories make the blades, they are actually egg-shaped as they do not close to a perfect 90* to the bore of the unit. They are tilted maybe 2-3* off center, and the edges of the plate are slightly beveled. You may want to hold the unit up to the light, and check to see how much light is coming in around the blade and possibly remake another blade to have a better seal. If you take any unmolested or professionally machine bored unit and hold it up to the light, you will not see any light around it at all.

Just my .02, been there done that ;)


Geoff
95 Base V6: Current Project; Work In Progress

beretta
Registered User
Posts: 957
Joined: Wed Feb 02, 2011 7:33 pm

Re: Throttle body porting 3.1 L

Postby beretta » Wed Feb 16, 2011 12:55 pm

i have held it up to the light and there is just enough of a gap to say there is one. the first throttle body was from a 2.8 that i done and it ran like crap i had the most problems with idle with it, so i pulled the one from my car and worked with it. before i honed it out i looked at the plate and the gap around it and there was a small gap with the factory none touched throttle body.

The throttle plate from the 3400 however has a small pin hole drill in the plate. this would allow for a little extra air as well.

when i first put it back on and fired it up, with everything hooked up, it ran good, until i drove around then the Idle valve i think was sticking open or it was setting itself open a little causing a higher idle, so i just took it out and pulled the plunger all the way and stuck it back in and pulled the wire for now, and adjusted my idle with the set screw on the throttle position.

This is for now until i can figure out if its my Idle valve thats no good or whats going on. but as is.. it works pretty good, when i first start it up i have to hold the throttle for a few seconds till it levels out then its fine for the rest of the day i have put probably 1000 KM on it this past week and never have any issues while driving. idles down great when i let off the throttle and doesnt stall out at stop lights or anything. i can cruise at 60 mph and my foot is just barley pushing the throttle just to say my foot is touching it. cruises along great, for some reason it seems really really good on gas too, seems like im getting way better fuel millage out of it now. weird...

I pulled the intake off the other day it was like +6 C so figured it would be a good day to do it, by the time i put it back on it was -15 C that night..
I pulled the intake to bore out where the throttle plate bolts so it would be the same size, it was already very close if not a little larger to start with. so i gave it a little hone just to smooth it out right there and i cleaned the inside of it from all the crap that was in there, a toilet brush and lots of soap worked great for that in my bath tub LOL just make sure to clean your mess up or your wife will have your head hahahaha.

The intake comes off pretty easy, take out all the 10 MM bolts around the outside, pull the brake booster vac line off, remove the throttle cable mounting plate at the back and when you lift it up there is a small rubber vac line under neath near the back its a little tricky to get off it has a bastard clamp on it but i was able to lift it up enough to get my hand in there with some pliers. put it back on in the reverse order.




Return to “Intakes”

Who is online

Users browsing this forum: No registered users and 1 guest