Plenum 71mm on Chim 430

[PH430]

Does an enlarged plenum to 71mm increase the performance, torque and trottle responce on my Chim 430?

With one of you have experience with it.

Thanks for all your comment

[SILICONEKID345HP]

PH430 said:

Does an enlarged plenum to 71mm increase the performance, torque and trottle responce on my Chim 430?

With one of you have experience with it.

Thanks for all your comment

Would it better to change all three ,plenum ,trumpet base and inlet manifold ?

[QBee]

Only needed if your engine is powerful enough to need more air and fuel mixture getting into the engine

[carsy]

I don't think you would notice any difference.

[SILICONEKID345HP]

QBee said:

Only needed if your engine is powerful enough to need more air and fuel mixture getting into the engine

Better throttle response . Its got a help a 280hp big valve .

[Sardonicus]

carsy said:

I don't think you would notice any difference.

This

[blitzracing]

The AFM is the biggest bottle neck- have a look at its cross section, its far smaller than the plenum intake. A bigger throttle plate in the plenum intake will let in more air for any given throttle opening (its like gearing the throttle pedal up), but it wont affect peak airflow or power output significantly.

[QBee]

I had my plenum upgraded to 72mm, together with a (bigger) 20AM AFM and a remap required by both, in order to improve top end airflow.
This was thanks to running too lean at high revs on a 300 bhp engine.
You need to do the whole package as Blitz says, and its only relevant if you have the power to require it.

[TV8]

Does the car have the original pipe to the plenum and from the AFM to the front of the car? If so, I would check that over and see how collapsed it is. The smoothbore up-grade seems to make sense and i have put one on both of cars.

[cp81]

Is a re-map needed if the plenum is increased?

As I too am considering this

Thanks

[V8 GRF]

cp81 said:

Is a re-map needed if the plenum is increased?

Yes.

[blitzracing]

I would not totally agree with this - At its simplest the big factors in mapping are the peak airflow for the engine to get the AFM scaling correct, and the point the engines volumetric sufficiency at its greatest (the torque curve shape) as at peak torque the cylinder fill is at maximum so you need the longest injector pulse per engine revolution. This is not the same as peak power as this may be at a higher RPM as the engine has more power cycles per second, albeit that each firing stoke produces less power as you go beyond peak torque. Above peak torque the cylinders may not fill fast enough due to restrictions in the inlet system, so you need to reduce the fuel per cycle to stop the engine running rich to maintain the best air fuel ratio. This seems completely counter intuitive, as you would assume you need peak fuelling at peak power, but you need to think of it as fuel injected per engine cycle (as the injector pulse width), not the total fuel drawn per second.

The so in summery you would need to remap if the engines peak torque point is moved up or down the RPM band, or peak airflow changes and I dont think just messing around with the plenum with change these factors significantly. Also not forgetting the ECU will continue to tweak the mixture in closed loop anyway, which is where the engine spends 95% of its time.

[V8 GRF]

Hmmm, I'd have thought the increased air would have messed around with the fuelling too much but I'll bow to your greater knowledge

(no sarcasm intended or implied )

[cp81]

Blitz thanks.

It's a modification I am considering but won't if re-map was required I wouldn't do it. As I thought the car MBE system I have on it would adjust the fuel mixture accordingly as under closed loop control.

I thought by changing this would change the throttle response.

[PH430]

Thanx for your comment guys.

My 430 has carbon trumpets, vectra injectors, adjustable fuelpress regulator, inductionkit for ACT with K&N filter. It's up now at 275BHP.
At revs above 4900, the engine is running rich. The standard AFM is in place, but i have got the 20AM to get fit on it with a new map from ACT.

I am wondering if the bigger AFM with the 71mm plenum wil give me increases in BHP, torque and trottle responce.
Is it possible to get it on a 300BHP?

[Number 7]

PH430 said:

Is it possible to get it on a 300BHP?

The 4.3 in my Wedge makes that - 72mm throttle disc, BV heads, higher flow injectors, JE 45mm trumpets and base, blended inlet manifold, raised CR (only about 9.5:1) but......no AFM, which takes away one of the big restrictions. Properly mapped ignition and fuelling, and still using a (locked) distributor.

[PH430]

I am running on a programmed 123 ignition system.

[blitzracing]

V8 GRF said:

Hmmm, I'd have thought the increased air would have messed around with the fuelling too much but I'll bow to your greater knowledge

(no sarcasm intended or implied )

No worries- point being here is the peak airflow that that the engine draws wont really change, as the AFM will restrict it long before the plenum throttle plate does. All the bigger plate is doing is letting in more air for less throttle movement, but as the AFM is measuring the actual air regardless of the size of the throttle plate, its business as usual from the ECU and map point of view.

[blitzracing]

Problem is it wont mean anything unless your remove the rest of the inlet system, so you are just measuring the throttle body pressure drop- then the car wont run...

[JimTC]

QBee said:

Only needed if your engine is powerful enough to need more air and fuel mixture getting into the engine

Apologies for the slight hi-jack of the thread.

With an increased diameter AFM and high performance injectors, what sort of power and torque gains could be expected with a 500 in good fettle? Thanks,