Tuning and plenum mod. questions?

2000GT · Jan 23, 2004

About two years ago I had my car dyno tuned for an a/f ratio of 13:1 at WOT with my current mods. If I add a new plenum/TB, who thinks I would need another tune and WHY?

It's my understanding that if I have a programmed a/f of 13:1 at WOT, wouldn’t my computer strive to achieve 13:1 after the bolt-on plenum/TB? Wouldn’t my oxygen sensors read the additional airflow from the larger plenum/TB and add more fuel to compensate until the a/f reached 13:1 again?

The result should be more horsepower and torque. However, the if for whatever reason the computer does not account for the additional airflow into the engine, my a/f ratio will run leaner than what it currently is right now. That concerns me.

Highroller · Jan 23, 2004

Wondering the same thing.. I would think that the computer would "want" to re-adjust for the additional air, but can the question is, Can it re-adjust, or will it keep the same program program settings?? I guess only someone that really understands tuning and ECU's can answer.

wms004 · Jan 23, 2004

me wondering too

2000GT · Jan 23, 2004

If someone knew what their a/f was before they installed the plenum/TB combo and then did a dyno afterwards that would help us as long as they posted their a/f graphs too. This way we could at least know if the car runs the same a/f after the install.

Maybe the guy that did the test on modulardepot.com could post the before and after a/f readings for us? Does anyone know who that was?

Tates · Jan 23, 2004

His name on here is 03trubluGT. I am in the process of buying one of these and will prolly retune afterwards, just don't know when this will be.

jstreet0204 · Jan 24, 2004

Yes there is a possibility that you would need a tune to keep it right at 13:1. During normal driving the EEC runs in a closed loop. It is constantly monitoring the oxygen sensor voltage and adjusting the on time of the fuel injectors to maintain a stoichiometric A/F ratio. During WOT it runs in open loop. To change the fuel ratio during WOT the EEC depends on functions in that the tuner probably changed to get your 13:1 ratio.

BMan5150 · Jan 24, 2004

jstreet0204 said:
Yes there is a possibility that you would need a tune to keep it right at 13:1. During normal driving the EEC runs in a closed loop. It is constantly monitoring the oxygen sensor voltage and adjusting the on time of the fuel injectors to maintain a stoichiometric A/F ratio. During WOT it runs in open loop. To change the fuel ratio during WOT the EEC depends on functions in that the tuner probably changed to get your 13:1 ratio.

That makes sense to me! I forgot about WOT being at WOT. When you change something mechanical (plenum), the car is probably still grabbing the same values (fuel, timing, etc.) from the tables the car uses at WOT.

I think I'm understanding this now - thanks for your explanation. Just for good measure, are you saying that basically a tune is needed only for WOT? Is that all most tuners "tune" is the WOT tables?

KenB · Jan 24, 2004

jstreet0204 said:
Yes there is a possibility that you would need a tune to keep it right at 13:1. During normal driving the EEC runs in a closed loop. It is constantly monitoring the oxygen sensor voltage and adjusting the on time of the fuel injectors to maintain a stoichiometric A/F ratio. During WOT it runs in open loop. To change the fuel ratio during WOT the EEC depends on functions in that the tuner probably changed to get your 13:1 ratio.

Yes and no. Depends on the tuner. If the car was tuned correctly you won't need a retune. While at WOT the MAF will detect more air so the EEC will add more fuel to maintain the correct A/F ratio. Like I said, it depends on the tune.

If you have an SCT or Fordchip tune, then you will be fine.

2000GT · Jan 24, 2004

BMan5150 said:
That makes sense to me! I forgot about WOT being at WOT. When you change something mechanical (plenum), the car is probably still grabbing the same values (fuel, timing, etc.) from the tables the car uses at WOT.

I think I'm understanding this now - thanks for your explanation. Just for good measure, are you saying that basically a tune is needed only for WOT? Is that all most tuners "tune" is the WOT tables?

From my experience, you only tune the a/f ratio at WOT. The part throttle a/f ratio doesn't get tinkered with. However, I believe my car's timing was tinkered with for both part throttle and WOT. I remember the tuner pulled out all timing retard after 3500 rpms. He refered to it as "throttle tip-in retard". He told me the stock program has timing retard built in between tranny shifts on both the manual and auto tranny. Seems like something Ford would do to lessen the blow of WOT throttle abuse on the tranny.

KenB · Jan 24, 2004

2000GT said:
From my experience, you only tune the a/f ratio at WOT. The part throttle a/f ratio doesn't get tinkered with. However, I believe my car's timing was tinkered with for both part throttle and WOT. I remember the tuner pulled out all timing retard after 3500 rpms. He refered to it as "throttle tip-in retard". He told me the stock program has timing retard built in between tranny shifts on both the manual and auto tranny. Seems like something Ford would do to lessen the blow of WOT throttle abuse on the tranny.

Doesn't exist on the manual cars.

BMan5150 · Jan 24, 2004

KenB said:
Doesn't exist on the manual cars.

Timing lulls between upshifts? Are you sure? I've heard many people talk about this, and I can honestly say there is something scaling back the throttle a bit inbetween shifts - in particular the 1-2 shift. 2000GT's car exhibits none of this slight hesitation on upshifts with his manual tranny. Could there be another explaination as to why the car hesitates momentarily on upshifts?

PEA · Jan 24, 2004

read this might help some people

2000GT said:
About two years ago I had my car dyno tuned for an a/f ratio of 13:1 at WOT with my current mods. If I add a new plenum/TB, who thinks I would need another tune and WHY?

It's my understanding that if I have a programmed a/f of 13:1 at WOT, wouldn’t my computer strive to achieve 13:1 after the bolt-on plenum/TB? Wouldn’t my oxygen sensors read the additional airflow from the larger plenum/TB and add more fuel to compensate until the a/f reached 13:1 again?

The result should be more horsepower and torque. However, the if for whatever reason the computer does not account for the additional airflow into the engine, my a/f ratio will run leaner than what it currently is right now. That concerns me.

please dont waste your money,
most bolt on crap only makes 2 to 8 real hp
from my own trials
all you do is spend money,chips r good for more timing and raised rev limiter,to help you use the power your car makes,the chip ppl say to reflash for all new bolt ons-
they do that to make money,in the real world his extra tune might get 1 more hp from all your bolt ons
i wasted time and money figuring this out,and you guys will too
please save money and get real hp...vortech,
you want to feel like a little kid again,you will
i dynoed at 370hp and love it.
again bolt ons r not worth the money,add it up and you can almost get your supercharger lol
hope this helps
p.s. dont brag that you have bolt ons-

Tuning and plenum mod. questions?

2000GT

Highroller

wms004

2000GT

Tates

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jstreet0204

Active Member

BMan5150

KenB

2000GT

KenB

BMan5150

PEA

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