70mm TB/Plenum questions

[TURBOV6]

This is some new mods I have done on my GN. I recently added a 70mm Accufab and a PTE plenum with a RJC powerplate also a 3.5" LS1 MAF with ported ends and a translator to go with it. I have lost over 3-4 mph on the 1/4 and about 2 miles on the 1/8 mile. The interesting thing that I have to lower my fuel pressure because of it running too rich but never had to lean it out with the stock TB I would think more air comming in needs more fuel. My 60ft did improve from the past and the car seems to pull alot harder off the line. So my best ET's was a 11.74@113, look at my sig for my older combo and ET.

Another thing I am having problems with the IAC counts (at zero). I had to crank up the throttle blade to prevent it from dieing out.

I know what most of you will probaly say that the 70mm is TOO BIG! I have spoken to some individuals that say it won't hurt at all and that I will benifit with a bigger throttle body. I would really like this to work so any help is appreciated. Thanks

 

[bruce]

To evaluate changes, means doing things one step at a time, and optimising the tune, at each step. Otherwise you're not going to know what actually worked or not.

Have you been watching EGTs, or using a WB?. If you miss the tune from one change to another then the car will slow down. IF the tune is the same, then the parts weren't needed, or the combo of parts just doesn't work for your setup.

 

[Hot Air]

Did you get the correct RJC plate to go with the PTE plenum? Is the rest of the air intake piping 3" diameter or larger? I see you have a PTE FMIC so it should be fine. Is your chip designed for the 70mm TB?
Conrad

 

[Ormand]

Is your chip designed for the 70mm TB?

How does the size of the throttle body get involved in the chip parameters?

 

[VadersV6]

You shouldnt port the ends of the MAF. They are precisely calibrated from the manufacturer, across a wide flow range, and any deviation from the flow pattern can really really really screw things up. Adding a screen before the MAF can help things a little bit, since the screen creates a uniform turbulence throughout the MAF, and makes thermistor location less critical. But its not a fix for hacking away at it.
Also, did you clear the memory before switching over? There is a relationship between MAF voltage and TPS voltage (flow vs. throttle position). Example: The computer learned to correlate a certain throttle position to a certain amount of flow. Before, 4 volts at the TPS = 500cfm (random numbers), and the computer learned this over time and adjusted for it. Now, when you reach 4 volts at the TPS, you may be flowing 700cfm after the parts were installed. Combine this with a ruined MAF that thinks its flowing 900cfm, and a computer that is assigning an obsolete parameter for 500cfm and you have a total wreck of a tune. You need a new tune. Are you running a chip that doesnt have adaptive strategy?

 

[TURBOV6]

I am using a EGT and my SM. EGT's were at 1580 and O2's at 820's. I have the correct powerplate for the PTE plenum.

I tired calling Joe at PTE but he's not there anymore but the guys at PTE said I don't need my chip reburned.

I will install the stock MAF ends back and try it out or use a screen as mentioned.

 

[VadersV6]

Just get an extender that you can adjust yourself. A mail order tune isnt a one size fits all tune.

 

[bruce]

There is a relationship between MAF voltage and TPS voltage (flow vs. throttle position). Example: The computer learned to correlate a certain throttle position to a certain amount of flow. Before, 4 volts at the TPS = 500cfm (random numbers), and the computer learned this over time and adjusted for it.

Can you quote the code, or tables, you're refering to?. Just curious..

 

[bruce]

I am using a EGT and my SM. EGT's were at 1580 and O2's at 820's. I have the correct powerplate for the PTE plenum.

Personally, I'd remove one or the other, retune to the same specs, and see where you are.

Lots of folks say the TB sizing is no big deal, yet, IMO, velocity should still count for something. With the injectors being aimed at the runner floor, it just seems to me, velocity should matter to some degree, depending on combination, for how well the fuel is vaporized off the runner floor.

 

[TURBOV6]

Thank-you everyone for the help and I'll try to retune my GN and try to put a screen the MAF.

 

[chris2316]

i have the same basic set-up translator plus 70mm t.b extender chip ! check to make sure your parameters are set right on the translator , i would get a wideband it is alot easier to tune i run aroung 10.9to1 a/f ratio! also what timing did you run before?

 

[TURBOV6]

i have the same basic set-up translator plus 70mm t.b extender chip ! check to make sure your parameters are set right on the translator , i would get a wideband it is alot easier to tune i run aroung 10.9to1 a/f ratio! also what timing did you run before?

Timming was at 26 degree Joe L race chip.

 

[chris2316]

you know i wonder if you took out the power plate what would happen , my friend went 2 tenths slower after he put that on

 

[TURBOV6]

you know i wonder if you took out the power plate what would happen , my friend went 2 tenths slower after he put that on

That would be something to think about. Thanks

 

[Ormand]

you know i wonder if you took out the power plate what would happen , my friend went 2 tenths slower after he put that on

Two of my friends put them on, and went 2 tenths QUICKER! Advantage- power plate! Seriously, this dead horse has been beaten so severely, there's nothing left to hit.

 

[VadersV6]

Can you quote the code, or tables, you're refering to?. Just curious..

On a buick? Nope. Its just the way all factory F.I. engine control is set up. Just about every manufacturer uses close to the same system of adaptive engine control. The code itself is different, but the end result is the same. It has to perform certain duties to adhere to EPA laws. If it didnt have adaptive strategy from the factory, the EPA wouldnt let it on the road.

 

[TurboJim]

Personally, I'd remove one or the other, retune to the same specs, and see where you are.

Lots of folks say the TB sizing is no big deal, yet, IMO, velocity should still count for something. With the injectors being aimed at the runner floor, it just seems to me, velocity should matter to some degree, depending on combination, for how well the fuel is vaporized off the runner floor.

I hope you're not saying with a bigger TB the air velocity at the intake runners has changed?!?!? I must disagree, If the port is 2" of area, putting 20" in front of it isnt going to change what can flow thru it. With boost pressure forcing thru youy can, but that isnt dictated by TB size. Once you get into ported this and polished that, I do think the intake tract can outflow a stock TB and thats where the benefit of a larger TB is....in my useless opinion. And I disagree with the injectors being aimed at the runner floor. This aint no TBI. They are aimed to mix with air flowing into the intale "bowl" and/or valve, well, in all the engines I have seen anyway. I've done hundreds of intake jobs and NEVER saw a clean spot in the runner from gasoline cleaning the runner from "powerwashing". Maybe the OE's are doing it wrong?

I do agree with the throttle opening scenario as it pertains to power, and theres another monkey to throw in the wrench, the larger TB allows you to flow more air at lower throttle position..ie: stock TB WOT air at 3/4 throttle for example, well, TV pressure is 3/4 throttle now.....and you're making WOT power. Without raising line pressure to accomodate the increase in power, the trans will most likely suffer from this.

But to the question at hand, you're right, each step should have been compensated for, and doing nothing but changing the plenum/tb/power plate there should have been minimal gain and no loss whatsoever.... airflow into the chambers really wasnt changed, except for possible distribution corrections. I'd venture a guess that the MAF calibration is off a bit and causing the dilemma. I saw a slight change in MAF values when I went to a LS1 maf. Fortunately I could correct it myself in the chip. Unfortunately, this lad is at the mercy of the programmers out there. I would get with Bob Bailey and ask for his input.