looking for some input from guys who have done the throttle body mod or some parts of it.
been trying to decide if i should do the whole thing or just remove the secondary butterflys. my concern is more idle issue after doing it more then a small bog at low rpm.

iam running a streetport s4 TII with a S5 throttle body and PFC,also emission block off plates. car wont be daily driven more weekends and track days.

this is the write up from fc3s pro that i was going to follow
FC3S Pro v2.0:&nbsp HOW-TO - FC3S Turbo Throttle Body Mod



THANKS

pick of my progress so far :p

 

Almost everyone on here has done the mod to some degree. If it's not street driven and you've got a standalone, you've answered your own question, IMO. No harm in bumping idle speed up a hair if you experience issue.

 

Cool thanks. I think iam going to go ahead and do it.

 

I would do it . I've rocked fully modded and its not that bad . I actually just installed a modded s5 t2 tb on my streetported s4 6port turbo setup. I'm going to be using the the secondary throttle plates that are vac driven for cold start and re-purpose them for out of boost throttle response . I needed a better tps setup for the haltech then I had made , which is why I got it. The plate idea came after I got to looking and thinking .

 

If your standalone gives you enough authority over the BAC valve such that it can take control of the cold start idle (I am not familiar with the PFC) then eliminating the cold start cam from the throttle body can be done without any consequences. Assuming the BAC is tuned and working.

Same with the dashpot. Many standalones have a dashpot function for the idle valve, which can take place of the mechanical dashpot. If that is true, then the dashpot can be eliminated.

With a standalone, the tertiary set of throttle plates can also be removed because a standalone which is properly tuned can account for the more abrupt throttle transition.

Note that each of these statements start with "standalone".

On a factory ECU, the so-called "throttle body mod" is a stupid waste of time ultimately resulting in a broken car which has zero net positive effect in power, throttle response or drivability but indeed has massive negative effect on the latter two.

 

Are these negative effects amplified/exaggerated in a turbo car?
I modded my NA throttle body quite a while ago, first for simplicity's sake and later to better serve the modded intake tract and must say, saw no ill effects whatsoever.
No performance benefits either, but I did not expect any, tbh.

 

I'am not really expecting any performance gains from this, more just the simplicity also. especially after having a leak from the coolant line going to the throttle body. worst case if i have any issue's i have a spare s5 tb i can put on.

 

When I bought my Tii the "tb mod" and "emissions delete(including bacv)" were already done do it. After adding back a bacv I had no issues as far as driveability out of it except having to hold the throttle for 10-15 seconds on a cold start till it would idle on its own if it was below maybe 40* outside. That very small inconvenience wasn't worth trying to find a stock S5 Tii TB, although since the S5 cars use timing also to help with idle it may be an issue that's worse on S4 cars.

 

Here is the one thing I don't understand...

On a manual transmission S5 NA car, the forward secondaries plates connect to a thermostat and are operated with just vacuum. It's a dumbass proofing device to keep you from going all out with the engine when it's cold. I removed the system because the vacuum actuator diaphram was busted creating a vacuum leak. The spring in the actuator hold the plates open at all times now.

What I am not understanding is what performance benefit is there to removing the rod and plates? They create minimal air resistance. A K@N air filter probably has better gains than removing that, why go to all the trouble?

Secondly, Why the hell would you remove the BAC? Every OEM car on the planet has some sort of bypass air control when fitted with electronic fuel injection! Its purpose it to let the car idle reliably and start under just about any circumstance.

Thirdly, the biggest restriction in an S5 intake is 2 things. The intake itself is #1 and #2 the MAF sensor. If someone could figure out how to use a GM hot wire MAF sensor on our cars that would be gold.

Other than going complete rewire standalone ECU, I don't see how any of these mods are a benefit. With a standalone the BAC valve is still a benefit, but you can get rid of the MAF sensor and run speed density or do whatever and then tune the car when you make changes.

 

If you've already disabled the function, why not remove the parts completely?

 

Why disable the function in the first place? As Aaron pointed out, you just make your car run worse, and I back him up on that.

 

Wut?
Did you not- your very own self- just admit to disabling the secondaries because the actuating diaphragm was leaking?
Have you not already pre-answered your own question?

 

I did, but didnt gain or lose functionality of the car. I was speaking more toward removing the BAC and such.

 

I have the throttle body mod, and BAC disabled, and have zero issues. Running Sprint RE

 

The NA throttle body is a little different. As I will mention below, the tertiary throttle plates operate opposite of turbo. Depends too on what was modded. Remove the dashpot on a stock ECU and the idle tends to dip quit a bit as the throttle snaps shut. Can be mitigated by turning the idle up. Also if the idle is higher, then the lack of cold start cam can be less noticeable.

But, idle is 750 RPM +-50. If it is higher, than something is wrong.


You could always just replace the leaking hose. Probably a lot easier than farting around with the throttle body.

I'd consider that to be broken, sort of like an old carbureted car with a misadjusted choke, but I realise that other people have different thresholds of drivability. You put the BAC valve back on so you helped mitigate a lot of effects.

I've always found the BAC removal thing to be very odd. No other car community I've been involved with does silly things like remove idle valves for the sake of "simplicity" or "clean engine bay". Seems to be specifically an RX-7 fetish.

Yes, in an NA car, disabling the tertiary throttle plates has little effect as once the car is warm, they are open anyway. That's one of the parts of the "throttle body mod" that is OK on an NA car.

No benefit. But, if the throttle body is already out of the car, then the little bit of effort to remove the rod then tap the holes for plugs is only a few minutes.

People are stupid?

Well, maybe not stupid, but misinformed. And there seems to be a segment that for some odd reason do these things for "simplicity" or "clean engine bay". I mentally translate that to "I don't know what this thing is and it might be broken so I'm going to break the car further by removing it".

Using a different MAF is trivially easy. Almost any standalone will run with any AFM/MAF or speed density without either.

Honestly it wouldn't be too difficult to measure the airflow vs. voltage curve on the stock AFM, then perform the same on a GM hot wire MAF after building an Arduino based control circuit (probably already out there). Then just use that same control circuit output a 0-5V signal translating the GM hot wire current measurements to that of the FC AFM with an internal lookup table (because the hot wire isn't quite linear).

Two benefits...the AFM is replaced with something smaller, newer, less restrictive. And by altering the translation in the controller, one can tune the AFRs.

In the past I've sort of done similar things with an S-AFC. Swapping a larger AFM or a different type (ie. cone type) onto an FC with the S-AFC doing the conversion.

Yes, with a standalone one has many more options. But one can't say "zero issues" without also saying whether the car is equipped with electric fans, AC, power steering. Then how much does the idle dip when one of those engage? What is the idle speed set to? Can you reach into an open window on a fully cold car, start the car with one turn of the key and then have it run smoothly without having to play with the throttle? What happens if EVERY electrical load on the car is suddenly switched on just after cold start?

 

Yeah, you got me there!

 

I was running my S4 T2 with the "complete" TB mod, no BAC. Stock ECU, Idle was set around 850, only had to lightly hold the throttle for 5-10sec when it was cold out.

 

It really does depend on a lot of factors. For example, without the BAC and cold start cam, start the car then turn on the heater, headlights, shift into reverse, turn on the defog. Car stalls due to electrical load.

A stripped down car that is only driven every in the good weather, where the electrical load is nothing but headlights and a stereo...that's a different story. No BAC and a 1000 RPM idle may be functional, even though it's still broken.

It is however remarkable back when I was wiring up standalones on a regular basis how many "No, don't bother with the BAC" came back to me later on asking for an idle valve to be installed.

 

I agree, my car was only driven in nice weather, no AC, etc. My current project with the MS3-Pro I will be running the BAC.

 

I don't deny it was wrong, but finding an unmolested Tii throttle body wasn't worth the hassle or money for the small inconvenience it posed. I had done an emissions delete(leaving bacv and dashpot) 10 years ago on my vert, so I was used to it to the point it was second nature. The Tii has since received a MS3X anyway so its since become a moot point.

 

I have a streetported S4 turbo II running Rtek 1.8, emissions deleted but retaining the BAC. I have already eliminated the coolant to the throttle body, but my car stays in cold idle mode (~2000rpm) much longer than it should. I am 99% sure this is due to the lack of coolant near the thermowax. Should I avoid doing this throttle body mod, or would it help my car idle where it should?

 

If you deleted the water feed but left the thermowax on the throttle body, then yeah, it's gonna stay in fast warmup mode. Remove the thermowax and linkage or hook up the water again, take your pick.

 

Whoops wrong thread. Please disregard. Not sure how that happened...

 

my build looks exactly like yours haha ..anyways i did the mod and i have a street port. Just got it running but will chop up under 1k and does not want to idle at all. Swapping to s5 throttle body that has been untouched to see if that helps me ..also running adaptronic ecu so i need to figure how to wire it??